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1.. SPDX-License-Identifier: GPL-2.0
2
3====================
4The /proc Filesystem
5====================
6
7===================== ======================================= ================
8/proc/sys Terrehon Bowden <terrehon@pacbell.net>, October 7 1999
9 Bodo Bauer <bb@ricochet.net>
102.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
11move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
12fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009
13===================== ======================================= ================
14
15
16
17.. Table of Contents
18
19 0 Preface
20 0.1 Introduction/Credits
21 0.2 Legal Stuff
22
23 1 Collecting System Information
24 1.1 Process-Specific Subdirectories
25 1.2 Kernel data
26 1.3 IDE devices in /proc/ide
27 1.4 Networking info in /proc/net
28 1.5 SCSI info
29 1.6 Parallel port info in /proc/parport
30 1.7 TTY info in /proc/tty
31 1.8 Miscellaneous kernel statistics in /proc/stat
32 1.9 Ext4 file system parameters
33
34 2 Modifying System Parameters
35
36 3 Per-Process Parameters
37 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
38 score
39 3.2 /proc/<pid>/oom_score - Display current oom-killer score
40 3.3 /proc/<pid>/io - Display the IO accounting fields
41 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
42 3.5 /proc/<pid>/mountinfo - Information about mounts
43 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
44 3.7 /proc/<pid>/task/<tid>/children - Information about task children
45 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
46 3.9 /proc/<pid>/map_files - Information about memory mapped files
47 3.10 /proc/<pid>/timerslack_ns - Task timerslack value
48 3.11 /proc/<pid>/patch_state - Livepatch patch operation state
49 3.12 /proc/<pid>/arch_status - Task architecture specific information
50
51 4 Configuring procfs
52 4.1 Mount options
53
54 5 Filesystem behavior
55
56Preface
57=======
58
590.1 Introduction/Credits
60------------------------
61
62This documentation is part of a soon (or so we hope) to be released book on
63the SuSE Linux distribution. As there is no complete documentation for the
64/proc file system and we've used many freely available sources to write these
65chapters, it seems only fair to give the work back to the Linux community.
66This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
67afraid it's still far from complete, but we hope it will be useful. As far as
68we know, it is the first 'all-in-one' document about the /proc file system. It
69is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
70SPARC, AXP, etc., features, you probably won't find what you are looking for.
71It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
72additions and patches are welcome and will be added to this document if you
73mail them to Bodo.
74
75We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
76other people for help compiling this documentation. We'd also like to extend a
77special thank you to Andi Kleen for documentation, which we relied on heavily
78to create this document, as well as the additional information he provided.
79Thanks to everybody else who contributed source or docs to the Linux kernel
80and helped create a great piece of software... :)
81
82If you have any comments, corrections or additions, please don't hesitate to
83contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
84document.
85
86The latest version of this document is available online at
87http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
88
89If the above direction does not works for you, you could try the kernel
90mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
91comandante@zaralinux.com.
92
930.2 Legal Stuff
94---------------
95
96We don't guarantee the correctness of this document, and if you come to us
97complaining about how you screwed up your system because of incorrect
98documentation, we won't feel responsible...
99
100Chapter 1: Collecting System Information
101========================================
102
103In This Chapter
104---------------
105* Investigating the properties of the pseudo file system /proc and its
106 ability to provide information on the running Linux system
107* Examining /proc's structure
108* Uncovering various information about the kernel and the processes running
109 on the system
110
111------------------------------------------------------------------------------
112
113The proc file system acts as an interface to internal data structures in the
114kernel. It can be used to obtain information about the system and to change
115certain kernel parameters at runtime (sysctl).
116
117First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
118show you how you can use /proc/sys to change settings.
119
1201.1 Process-Specific Subdirectories
121-----------------------------------
122
123The directory /proc contains (among other things) one subdirectory for each
124process running on the system, which is named after the process ID (PID).
125
126The link 'self' points to the process reading the file system. Each process
127subdirectory has the entries listed in Table 1-1.
128
129Note that an open file descriptor to /proc/<pid> or to any of its
130contained files or subdirectories does not prevent <pid> being reused
131for some other process in the event that <pid> exits. Operations on
132open /proc/<pid> file descriptors corresponding to dead processes
133never act on any new process that the kernel may, through chance, have
134also assigned the process ID <pid>. Instead, operations on these FDs
135usually fail with ESRCH.
136
137.. table:: Table 1-1: Process specific entries in /proc
138
139 ============= ===============================================================
140 File Content
141 ============= ===============================================================
142 clear_refs Clears page referenced bits shown in smaps output
143 cmdline Command line arguments
144 cpu Current and last cpu in which it was executed (2.4)(smp)
145 cwd Link to the current working directory
146 environ Values of environment variables
147 exe Link to the executable of this process
148 fd Directory, which contains all file descriptors
149 maps Memory maps to executables and library files (2.4)
150 mem Memory held by this process
151 root Link to the root directory of this process
152 stat Process status
153 statm Process memory status information
154 status Process status in human readable form
155 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function
156 symbol the task is blocked in - or "0" if not blocked.
157 pagemap Page table
158 stack Report full stack trace, enable via CONFIG_STACKTRACE
159 smaps An extension based on maps, showing the memory consumption of
160 each mapping and flags associated with it
161 smaps_rollup Accumulated smaps stats for all mappings of the process. This
162 can be derived from smaps, but is faster and more convenient
163 numa_maps An extension based on maps, showing the memory locality and
164 binding policy as well as mem usage (in pages) of each mapping.
165 ============= ===============================================================
166
167For example, to get the status information of a process, all you have to do is
168read the file /proc/PID/status::
169
170 >cat /proc/self/status
171 Name: cat
172 State: R (running)
173 Tgid: 5452
174 Pid: 5452
175 PPid: 743
176 TracerPid: 0 (2.4)
177 Uid: 501 501 501 501
178 Gid: 100 100 100 100
179 FDSize: 256
180 Groups: 100 14 16
181 VmPeak: 5004 kB
182 VmSize: 5004 kB
183 VmLck: 0 kB
184 VmHWM: 476 kB
185 VmRSS: 476 kB
186 RssAnon: 352 kB
187 RssFile: 120 kB
188 RssShmem: 4 kB
189 VmData: 156 kB
190 VmStk: 88 kB
191 VmExe: 68 kB
192 VmLib: 1412 kB
193 VmPTE: 20 kb
194 VmSwap: 0 kB
195 HugetlbPages: 0 kB
196 CoreDumping: 0
197 THP_enabled: 1
198 Threads: 1
199 SigQ: 0/28578
200 SigPnd: 0000000000000000
201 ShdPnd: 0000000000000000
202 SigBlk: 0000000000000000
203 SigIgn: 0000000000000000
204 SigCgt: 0000000000000000
205 CapInh: 00000000fffffeff
206 CapPrm: 0000000000000000
207 CapEff: 0000000000000000
208 CapBnd: ffffffffffffffff
209 CapAmb: 0000000000000000
210 NoNewPrivs: 0
211 Seccomp: 0
212 Speculation_Store_Bypass: thread vulnerable
213 voluntary_ctxt_switches: 0
214 nonvoluntary_ctxt_switches: 1
215
216This shows you nearly the same information you would get if you viewed it with
217the ps command. In fact, ps uses the proc file system to obtain its
218information. But you get a more detailed view of the process by reading the
219file /proc/PID/status. It fields are described in table 1-2.
220
221The statm file contains more detailed information about the process
222memory usage. Its seven fields are explained in Table 1-3. The stat file
223contains detailed information about the process itself. Its fields are
224explained in Table 1-4.
225
226(for SMP CONFIG users)
227
228For making accounting scalable, RSS related information are handled in an
229asynchronous manner and the value may not be very precise. To see a precise
230snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
231It's slow but very precise.
232
233.. table:: Table 1-2: Contents of the status files (as of 4.19)
234
235 ========================== ===================================================
236 Field Content
237 ========================== ===================================================
238 Name filename of the executable
239 Umask file mode creation mask
240 State state (R is running, S is sleeping, D is sleeping
241 in an uninterruptible wait, Z is zombie,
242 T is traced or stopped)
243 Tgid thread group ID
244 Ngid NUMA group ID (0 if none)
245 Pid process id
246 PPid process id of the parent process
247 TracerPid PID of process tracing this process (0 if not)
248 Uid Real, effective, saved set, and file system UIDs
249 Gid Real, effective, saved set, and file system GIDs
250 FDSize number of file descriptor slots currently allocated
251 Groups supplementary group list
252 NStgid descendant namespace thread group ID hierarchy
253 NSpid descendant namespace process ID hierarchy
254 NSpgid descendant namespace process group ID hierarchy
255 NSsid descendant namespace session ID hierarchy
256 VmPeak peak virtual memory size
257 VmSize total program size
258 VmLck locked memory size
259 VmPin pinned memory size
260 VmHWM peak resident set size ("high water mark")
261 VmRSS size of memory portions. It contains the three
262 following parts
263 (VmRSS = RssAnon + RssFile + RssShmem)
264 RssAnon size of resident anonymous memory
265 RssFile size of resident file mappings
266 RssShmem size of resident shmem memory (includes SysV shm,
267 mapping of tmpfs and shared anonymous mappings)
268 VmData size of private data segments
269 VmStk size of stack segments
270 VmExe size of text segment
271 VmLib size of shared library code
272 VmPTE size of page table entries
273 VmSwap amount of swap used by anonymous private data
274 (shmem swap usage is not included)
275 HugetlbPages size of hugetlb memory portions
276 CoreDumping process's memory is currently being dumped
277 (killing the process may lead to a corrupted core)
278 THP_enabled process is allowed to use THP (returns 0 when
279 PR_SET_THP_DISABLE is set on the process
280 Threads number of threads
281 SigQ number of signals queued/max. number for queue
282 SigPnd bitmap of pending signals for the thread
283 ShdPnd bitmap of shared pending signals for the process
284 SigBlk bitmap of blocked signals
285 SigIgn bitmap of ignored signals
286 SigCgt bitmap of caught signals
287 CapInh bitmap of inheritable capabilities
288 CapPrm bitmap of permitted capabilities
289 CapEff bitmap of effective capabilities
290 CapBnd bitmap of capabilities bounding set
291 CapAmb bitmap of ambient capabilities
292 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
293 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
294 Speculation_Store_Bypass speculative store bypass mitigation status
295 Cpus_allowed mask of CPUs on which this process may run
296 Cpus_allowed_list Same as previous, but in "list format"
297 Mems_allowed mask of memory nodes allowed to this process
298 Mems_allowed_list Same as previous, but in "list format"
299 voluntary_ctxt_switches number of voluntary context switches
300 nonvoluntary_ctxt_switches number of non voluntary context switches
301 ========================== ===================================================
302
303
304.. table:: Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
305
306 ======== =============================== ==============================
307 Field Content
308 ======== =============================== ==============================
309 size total program size (pages) (same as VmSize in status)
310 resident size of memory portions (pages) (same as VmRSS in status)
311 shared number of pages that are shared (i.e. backed by a file, same
312 as RssFile+RssShmem in status)
313 trs number of pages that are 'code' (not including libs; broken,
314 includes data segment)
315 lrs number of pages of library (always 0 on 2.6)
316 drs number of pages of data/stack (including libs; broken,
317 includes library text)
318 dt number of dirty pages (always 0 on 2.6)
319 ======== =============================== ==============================
320
321
322.. table:: Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
323
324 ============= ===============================================================
325 Field Content
326 ============= ===============================================================
327 pid process id
328 tcomm filename of the executable
329 state state (R is running, S is sleeping, D is sleeping in an
330 uninterruptible wait, Z is zombie, T is traced or stopped)
331 ppid process id of the parent process
332 pgrp pgrp of the process
333 sid session id
334 tty_nr tty the process uses
335 tty_pgrp pgrp of the tty
336 flags task flags
337 min_flt number of minor faults
338 cmin_flt number of minor faults with child's
339 maj_flt number of major faults
340 cmaj_flt number of major faults with child's
341 utime user mode jiffies
342 stime kernel mode jiffies
343 cutime user mode jiffies with child's
344 cstime kernel mode jiffies with child's
345 priority priority level
346 nice nice level
347 num_threads number of threads
348 it_real_value (obsolete, always 0)
349 start_time time the process started after system boot
350 vsize virtual memory size
351 rss resident set memory size
352 rsslim current limit in bytes on the rss
353 start_code address above which program text can run
354 end_code address below which program text can run
355 start_stack address of the start of the main process stack
356 esp current value of ESP
357 eip current value of EIP
358 pending bitmap of pending signals
359 blocked bitmap of blocked signals
360 sigign bitmap of ignored signals
361 sigcatch bitmap of caught signals
362 0 (place holder, used to be the wchan address,
363 use /proc/PID/wchan instead)
364 0 (place holder)
365 0 (place holder)
366 exit_signal signal to send to parent thread on exit
367 task_cpu which CPU the task is scheduled on
368 rt_priority realtime priority
369 policy scheduling policy (man sched_setscheduler)
370 blkio_ticks time spent waiting for block IO
371 gtime guest time of the task in jiffies
372 cgtime guest time of the task children in jiffies
373 start_data address above which program data+bss is placed
374 end_data address below which program data+bss is placed
375 start_brk address above which program heap can be expanded with brk()
376 arg_start address above which program command line is placed
377 arg_end address below which program command line is placed
378 env_start address above which program environment is placed
379 env_end address below which program environment is placed
380 exit_code the thread's exit_code in the form reported by the waitpid
381 system call
382 ============= ===============================================================
383
384The /proc/PID/maps file contains the currently mapped memory regions and
385their access permissions.
386
387The format is::
388
389 address perms offset dev inode pathname
390
391 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test
392 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
393 0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
394 a7cb1000-a7cb2000 ---p 00000000 00:00 0
395 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
396 a7eb2000-a7eb3000 ---p 00000000 00:00 0
397 a7eb3000-a7ed5000 rw-p 00000000 00:00 0
398 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
399 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
400 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
401 a800b000-a800e000 rw-p 00000000 00:00 0
402 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
403 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
404 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
405 a8024000-a8027000 rw-p 00000000 00:00 0
406 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
407 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
408 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
409 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
410 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
411
412where "address" is the address space in the process that it occupies, "perms"
413is a set of permissions::
414
415 r = read
416 w = write
417 x = execute
418 s = shared
419 p = private (copy on write)
420
421"offset" is the offset into the mapping, "dev" is the device (major:minor), and
422"inode" is the inode on that device. 0 indicates that no inode is associated
423with the memory region, as the case would be with BSS (uninitialized data).
424The "pathname" shows the name associated file for this mapping. If the mapping
425is not associated with a file:
426
427 ======= ====================================
428 [heap] the heap of the program
429 [stack] the stack of the main process
430 [vdso] the "virtual dynamic shared object",
431 the kernel system call handler
432 ======= ====================================
433
434 or if empty, the mapping is anonymous.
435
436The /proc/PID/smaps is an extension based on maps, showing the memory
437consumption for each of the process's mappings. For each mapping (aka Virtual
438Memory Area, or VMA) there is a series of lines such as the following::
439
440 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
441
442 Size: 1084 kB
443 KernelPageSize: 4 kB
444 MMUPageSize: 4 kB
445 Rss: 892 kB
446 Pss: 374 kB
447 Shared_Clean: 892 kB
448 Shared_Dirty: 0 kB
449 Private_Clean: 0 kB
450 Private_Dirty: 0 kB
451 Referenced: 892 kB
452 Anonymous: 0 kB
453 LazyFree: 0 kB
454 AnonHugePages: 0 kB
455 ShmemPmdMapped: 0 kB
456 Shared_Hugetlb: 0 kB
457 Private_Hugetlb: 0 kB
458 Swap: 0 kB
459 SwapPss: 0 kB
460 KernelPageSize: 4 kB
461 MMUPageSize: 4 kB
462 Locked: 0 kB
463 THPeligible: 0
464 VmFlags: rd ex mr mw me dw
465
466The first of these lines shows the same information as is displayed for the
467mapping in /proc/PID/maps. Following lines show the size of the mapping
468(size); the size of each page allocated when backing a VMA (KernelPageSize),
469which is usually the same as the size in the page table entries; the page size
470used by the MMU when backing a VMA (in most cases, the same as KernelPageSize);
471the amount of the mapping that is currently resident in RAM (RSS); the
472process' proportional share of this mapping (PSS); and the number of clean and
473dirty shared and private pages in the mapping.
474
475The "proportional set size" (PSS) of a process is the count of pages it has
476in memory, where each page is divided by the number of processes sharing it.
477So if a process has 1000 pages all to itself, and 1000 shared with one other
478process, its PSS will be 1500.
479
480Note that even a page which is part of a MAP_SHARED mapping, but has only
481a single pte mapped, i.e. is currently used by only one process, is accounted
482as private and not as shared.
483
484"Referenced" indicates the amount of memory currently marked as referenced or
485accessed.
486
487"Anonymous" shows the amount of memory that does not belong to any file. Even
488a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
489and a page is modified, the file page is replaced by a private anonymous copy.
490
491"LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE).
492The memory isn't freed immediately with madvise(). It's freed in memory
493pressure if the memory is clean. Please note that the printed value might
494be lower than the real value due to optimizations used in the current
495implementation. If this is not desirable please file a bug report.
496
497"AnonHugePages" shows the ammount of memory backed by transparent hugepage.
498
499"ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by
500huge pages.
501
502"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
503hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
504reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
505
506"Swap" shows how much would-be-anonymous memory is also used, but out on swap.
507
508For shmem mappings, "Swap" includes also the size of the mapped (and not
509replaced by copy-on-write) part of the underlying shmem object out on swap.
510"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
511does not take into account swapped out page of underlying shmem objects.
512"Locked" indicates whether the mapping is locked in memory or not.
513"THPeligible" indicates whether the mapping is eligible for allocating THP
514pages - 1 if true, 0 otherwise. It just shows the current status.
515
516"VmFlags" field deserves a separate description. This member represents the
517kernel flags associated with the particular virtual memory area in two letter
518encoded manner. The codes are the following:
519
520 == =======================================
521 rd readable
522 wr writeable
523 ex executable
524 sh shared
525 mr may read
526 mw may write
527 me may execute
528 ms may share
529 gd stack segment growns down
530 pf pure PFN range
531 dw disabled write to the mapped file
532 lo pages are locked in memory
533 io memory mapped I/O area
534 sr sequential read advise provided
535 rr random read advise provided
536 dc do not copy area on fork
537 de do not expand area on remapping
538 ac area is accountable
539 nr swap space is not reserved for the area
540 ht area uses huge tlb pages
541 ar architecture specific flag
542 dd do not include area into core dump
543 sd soft dirty flag
544 mm mixed map area
545 hg huge page advise flag
546 nh no huge page advise flag
547 mg mergable advise flag
548 bt arm64 BTI guarded page
549 == =======================================
550
551Note that there is no guarantee that every flag and associated mnemonic will
552be present in all further kernel releases. Things get changed, the flags may
553be vanished or the reverse -- new added. Interpretation of their meaning
554might change in future as well. So each consumer of these flags has to
555follow each specific kernel version for the exact semantic.
556
557This file is only present if the CONFIG_MMU kernel configuration option is
558enabled.
559
560Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent
561output can be achieved only in the single read call).
562
563This typically manifests when doing partial reads of these files while the
564memory map is being modified. Despite the races, we do provide the following
565guarantees:
566
5671) The mapped addresses never go backwards, which implies no two
568 regions will ever overlap.
5692) If there is something at a given vaddr during the entirety of the
570 life of the smaps/maps walk, there will be some output for it.
571
572The /proc/PID/smaps_rollup file includes the same fields as /proc/PID/smaps,
573but their values are the sums of the corresponding values for all mappings of
574the process. Additionally, it contains these fields:
575
576- Pss_Anon
577- Pss_File
578- Pss_Shmem
579
580They represent the proportional shares of anonymous, file, and shmem pages, as
581described for smaps above. These fields are omitted in smaps since each
582mapping identifies the type (anon, file, or shmem) of all pages it contains.
583Thus all information in smaps_rollup can be derived from smaps, but at a
584significantly higher cost.
585
586The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
587bits on both physical and virtual pages associated with a process, and the
588soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst
589for details).
590To clear the bits for all the pages associated with the process::
591
592 > echo 1 > /proc/PID/clear_refs
593
594To clear the bits for the anonymous pages associated with the process::
595
596 > echo 2 > /proc/PID/clear_refs
597
598To clear the bits for the file mapped pages associated with the process::
599
600 > echo 3 > /proc/PID/clear_refs
601
602To clear the soft-dirty bit::
603
604 > echo 4 > /proc/PID/clear_refs
605
606To reset the peak resident set size ("high water mark") to the process's
607current value::
608
609 > echo 5 > /proc/PID/clear_refs
610
611Any other value written to /proc/PID/clear_refs will have no effect.
612
613The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
614using /proc/kpageflags and number of times a page is mapped using
615/proc/kpagecount. For detailed explanation, see
616Documentation/admin-guide/mm/pagemap.rst.
617
618The /proc/pid/numa_maps is an extension based on maps, showing the memory
619locality and binding policy, as well as the memory usage (in pages) of
620each mapping. The output follows a general format where mapping details get
621summarized separated by blank spaces, one mapping per each file line::
622
623 address policy mapping details
624
625 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
626 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
627 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
628 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
629 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
630 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
631 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
632 320698b000 default file=/lib64/libc-2.12.so
633 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
634 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
635 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
636 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
637 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
638 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
639 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
640 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
641
642Where:
643
644"address" is the starting address for the mapping;
645
646"policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst);
647
648"mapping details" summarizes mapping data such as mapping type, page usage counters,
649node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
650size, in KB, that is backing the mapping up.
651
6521.2 Kernel data
653---------------
654
655Similar to the process entries, the kernel data files give information about
656the running kernel. The files used to obtain this information are contained in
657/proc and are listed in Table 1-5. Not all of these will be present in your
658system. It depends on the kernel configuration and the loaded modules, which
659files are there, and which are missing.
660
661.. table:: Table 1-5: Kernel info in /proc
662
663 ============ ===============================================================
664 File Content
665 ============ ===============================================================
666 apm Advanced power management info
667 buddyinfo Kernel memory allocator information (see text) (2.5)
668 bus Directory containing bus specific information
669 cmdline Kernel command line
670 cpuinfo Info about the CPU
671 devices Available devices (block and character)
672 dma Used DMS channels
673 filesystems Supported filesystems
674 driver Various drivers grouped here, currently rtc (2.4)
675 execdomains Execdomains, related to security (2.4)
676 fb Frame Buffer devices (2.4)
677 fs File system parameters, currently nfs/exports (2.4)
678 ide Directory containing info about the IDE subsystem
679 interrupts Interrupt usage
680 iomem Memory map (2.4)
681 ioports I/O port usage
682 irq Masks for irq to cpu affinity (2.4)(smp?)
683 isapnp ISA PnP (Plug&Play) Info (2.4)
684 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
685 kmsg Kernel messages
686 ksyms Kernel symbol table
687 loadavg Load average of last 1, 5 & 15 minutes
688 locks Kernel locks
689 meminfo Memory info
690 misc Miscellaneous
691 modules List of loaded modules
692 mounts Mounted filesystems
693 net Networking info (see text)
694 pagetypeinfo Additional page allocator information (see text) (2.5)
695 partitions Table of partitions known to the system
696 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
697 decoupled by lspci (2.4)
698 rtc Real time clock
699 scsi SCSI info (see text)
700 slabinfo Slab pool info
701 softirqs softirq usage
702 stat Overall statistics
703 swaps Swap space utilization
704 sys See chapter 2
705 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
706 tty Info of tty drivers
707 uptime Wall clock since boot, combined idle time of all cpus
708 version Kernel version
709 video bttv info of video resources (2.4)
710 vmallocinfo Show vmalloced areas
711 ============ ===============================================================
712
713You can, for example, check which interrupts are currently in use and what
714they are used for by looking in the file /proc/interrupts::
715
716 > cat /proc/interrupts
717 CPU0
718 0: 8728810 XT-PIC timer
719 1: 895 XT-PIC keyboard
720 2: 0 XT-PIC cascade
721 3: 531695 XT-PIC aha152x
722 4: 2014133 XT-PIC serial
723 5: 44401 XT-PIC pcnet_cs
724 8: 2 XT-PIC rtc
725 11: 8 XT-PIC i82365
726 12: 182918 XT-PIC PS/2 Mouse
727 13: 1 XT-PIC fpu
728 14: 1232265 XT-PIC ide0
729 15: 7 XT-PIC ide1
730 NMI: 0
731
732In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
733output of a SMP machine)::
734
735 > cat /proc/interrupts
736
737 CPU0 CPU1
738 0: 1243498 1214548 IO-APIC-edge timer
739 1: 8949 8958 IO-APIC-edge keyboard
740 2: 0 0 XT-PIC cascade
741 5: 11286 10161 IO-APIC-edge soundblaster
742 8: 1 0 IO-APIC-edge rtc
743 9: 27422 27407 IO-APIC-edge 3c503
744 12: 113645 113873 IO-APIC-edge PS/2 Mouse
745 13: 0 0 XT-PIC fpu
746 14: 22491 24012 IO-APIC-edge ide0
747 15: 2183 2415 IO-APIC-edge ide1
748 17: 30564 30414 IO-APIC-level eth0
749 18: 177 164 IO-APIC-level bttv
750 NMI: 2457961 2457959
751 LOC: 2457882 2457881
752 ERR: 2155
753
754NMI is incremented in this case because every timer interrupt generates a NMI
755(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
756
757LOC is the local interrupt counter of the internal APIC of every CPU.
758
759ERR is incremented in the case of errors in the IO-APIC bus (the bus that
760connects the CPUs in a SMP system. This means that an error has been detected,
761the IO-APIC automatically retry the transmission, so it should not be a big
762problem, but you should read the SMP-FAQ.
763
764In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
765/proc/interrupts to display every IRQ vector in use by the system, not
766just those considered 'most important'. The new vectors are:
767
768THR
769 interrupt raised when a machine check threshold counter
770 (typically counting ECC corrected errors of memory or cache) exceeds
771 a configurable threshold. Only available on some systems.
772
773TRM
774 a thermal event interrupt occurs when a temperature threshold
775 has been exceeded for the CPU. This interrupt may also be generated
776 when the temperature drops back to normal.
777
778SPU
779 a spurious interrupt is some interrupt that was raised then lowered
780 by some IO device before it could be fully processed by the APIC. Hence
781 the APIC sees the interrupt but does not know what device it came from.
782 For this case the APIC will generate the interrupt with a IRQ vector
783 of 0xff. This might also be generated by chipset bugs.
784
785RES, CAL, TLB
786 rescheduling, call and TLB flush interrupts are
787 sent from one CPU to another per the needs of the OS. Typically,
788 their statistics are used by kernel developers and interested users to
789 determine the occurrence of interrupts of the given type.
790
791The above IRQ vectors are displayed only when relevant. For example,
792the threshold vector does not exist on x86_64 platforms. Others are
793suppressed when the system is a uniprocessor. As of this writing, only
794i386 and x86_64 platforms support the new IRQ vector displays.
795
796Of some interest is the introduction of the /proc/irq directory to 2.4.
797It could be used to set IRQ to CPU affinity. This means that you can "hook" an
798IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
799irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
800prof_cpu_mask.
801
802For example::
803
804 > ls /proc/irq/
805 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
806 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
807 > ls /proc/irq/0/
808 smp_affinity
809
810smp_affinity is a bitmask, in which you can specify which CPUs can handle the
811IRQ. You can set it by doing::
812
813 > echo 1 > /proc/irq/10/smp_affinity
814
815This means that only the first CPU will handle the IRQ, but you can also echo
8165 which means that only the first and third CPU can handle the IRQ.
817
818The contents of each smp_affinity file is the same by default::
819
820 > cat /proc/irq/0/smp_affinity
821 ffffffff
822
823There is an alternate interface, smp_affinity_list which allows specifying
824a CPU range instead of a bitmask::
825
826 > cat /proc/irq/0/smp_affinity_list
827 1024-1031
828
829The default_smp_affinity mask applies to all non-active IRQs, which are the
830IRQs which have not yet been allocated/activated, and hence which lack a
831/proc/irq/[0-9]* directory.
832
833The node file on an SMP system shows the node to which the device using the IRQ
834reports itself as being attached. This hardware locality information does not
835include information about any possible driver locality preference.
836
837prof_cpu_mask specifies which CPUs are to be profiled by the system wide
838profiler. Default value is ffffffff (all CPUs if there are only 32 of them).
839
840The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
841between all the CPUs which are allowed to handle it. As usual the kernel has
842more info than you and does a better job than you, so the defaults are the
843best choice for almost everyone. [Note this applies only to those IO-APIC's
844that support "Round Robin" interrupt distribution.]
845
846There are three more important subdirectories in /proc: net, scsi, and sys.
847The general rule is that the contents, or even the existence of these
848directories, depend on your kernel configuration. If SCSI is not enabled, the
849directory scsi may not exist. The same is true with the net, which is there
850only when networking support is present in the running kernel.
851
852The slabinfo file gives information about memory usage at the slab level.
853Linux uses slab pools for memory management above page level in version 2.2.
854Commonly used objects have their own slab pool (such as network buffers,
855directory cache, and so on).
856
857::
858
859 > cat /proc/buddyinfo
860
861 Node 0, zone DMA 0 4 5 4 4 3 ...
862 Node 0, zone Normal 1 0 0 1 101 8 ...
863 Node 0, zone HighMem 2 0 0 1 1 0 ...
864
865External fragmentation is a problem under some workloads, and buddyinfo is a
866useful tool for helping diagnose these problems. Buddyinfo will give you a
867clue as to how big an area you can safely allocate, or why a previous
868allocation failed.
869
870Each column represents the number of pages of a certain order which are
871available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
872ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
873available in ZONE_NORMAL, etc...
874
875More information relevant to external fragmentation can be found in
876pagetypeinfo::
877
878 > cat /proc/pagetypeinfo
879 Page block order: 9
880 Pages per block: 512
881
882 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
883 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
884 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
885 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
886 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
887 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
888 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
889 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
890 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
891 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
892 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
893
894 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
895 Node 0, zone DMA 2 0 5 1 0
896 Node 0, zone DMA32 41 6 967 2 0
897
898Fragmentation avoidance in the kernel works by grouping pages of different
899migrate types into the same contiguous regions of memory called page blocks.
900A page block is typically the size of the default hugepage size, e.g. 2MB on
901X86-64. By keeping pages grouped based on their ability to move, the kernel
902can reclaim pages within a page block to satisfy a high-order allocation.
903
904The pagetypinfo begins with information on the size of a page block. It
905then gives the same type of information as buddyinfo except broken down
906by migrate-type and finishes with details on how many page blocks of each
907type exist.
908
909If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
910from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
911make an estimate of the likely number of huge pages that can be allocated
912at a given point in time. All the "Movable" blocks should be allocatable
913unless memory has been mlock()'d. Some of the Reclaimable blocks should
914also be allocatable although a lot of filesystem metadata may have to be
915reclaimed to achieve this.
916
917
918meminfo
919~~~~~~~
920
921Provides information about distribution and utilization of memory. This
922varies by architecture and compile options. The following is from a
92316GB PIII, which has highmem enabled. You may not have all of these fields.
924
925::
926
927 > cat /proc/meminfo
928
929 MemTotal: 16344972 kB
930 MemFree: 13634064 kB
931 MemAvailable: 14836172 kB
932 Buffers: 3656 kB
933 Cached: 1195708 kB
934 SwapCached: 0 kB
935 Active: 891636 kB
936 Inactive: 1077224 kB
937 HighTotal: 15597528 kB
938 HighFree: 13629632 kB
939 LowTotal: 747444 kB
940 LowFree: 4432 kB
941 SwapTotal: 0 kB
942 SwapFree: 0 kB
943 Dirty: 968 kB
944 Writeback: 0 kB
945 AnonPages: 861800 kB
946 Mapped: 280372 kB
947 Shmem: 644 kB
948 KReclaimable: 168048 kB
949 Slab: 284364 kB
950 SReclaimable: 159856 kB
951 SUnreclaim: 124508 kB
952 PageTables: 24448 kB
953 NFS_Unstable: 0 kB
954 Bounce: 0 kB
955 WritebackTmp: 0 kB
956 CommitLimit: 7669796 kB
957 Committed_AS: 100056 kB
958 VmallocTotal: 112216 kB
959 VmallocUsed: 428 kB
960 VmallocChunk: 111088 kB
961 Percpu: 62080 kB
962 HardwareCorrupted: 0 kB
963 AnonHugePages: 49152 kB
964 ShmemHugePages: 0 kB
965 ShmemPmdMapped: 0 kB
966
967MemTotal
968 Total usable RAM (i.e. physical RAM minus a few reserved
969 bits and the kernel binary code)
970MemFree
971 The sum of LowFree+HighFree
972MemAvailable
973 An estimate of how much memory is available for starting new
974 applications, without swapping. Calculated from MemFree,
975 SReclaimable, the size of the file LRU lists, and the low
976 watermarks in each zone.
977 The estimate takes into account that the system needs some
978 page cache to function well, and that not all reclaimable
979 slab will be reclaimable, due to items being in use. The
980 impact of those factors will vary from system to system.
981Buffers
982 Relatively temporary storage for raw disk blocks
983 shouldn't get tremendously large (20MB or so)
984Cached
985 in-memory cache for files read from the disk (the
986 pagecache). Doesn't include SwapCached
987SwapCached
988 Memory that once was swapped out, is swapped back in but
989 still also is in the swapfile (if memory is needed it
990 doesn't need to be swapped out AGAIN because it is already
991 in the swapfile. This saves I/O)
992Active
993 Memory that has been used more recently and usually not
994 reclaimed unless absolutely necessary.
995Inactive
996 Memory which has been less recently used. It is more
997 eligible to be reclaimed for other purposes
998HighTotal, HighFree
999 Highmem is all memory above ~860MB of physical memory.
1000 Highmem areas are for use by userspace programs, or
1001 for the pagecache. The kernel must use tricks to access
1002 this memory, making it slower to access than lowmem.
1003LowTotal, LowFree
1004 Lowmem is memory which can be used for everything that
1005 highmem can be used for, but it is also available for the
1006 kernel's use for its own data structures. Among many
1007 other things, it is where everything from the Slab is
1008 allocated. Bad things happen when you're out of lowmem.
1009SwapTotal
1010 total amount of swap space available
1011SwapFree
1012 Memory which has been evicted from RAM, and is temporarily
1013 on the disk
1014Dirty
1015 Memory which is waiting to get written back to the disk
1016Writeback
1017 Memory which is actively being written back to the disk
1018AnonPages
1019 Non-file backed pages mapped into userspace page tables
1020HardwareCorrupted
1021 The amount of RAM/memory in KB, the kernel identifies as
1022 corrupted.
1023AnonHugePages
1024 Non-file backed huge pages mapped into userspace page tables
1025Mapped
1026 files which have been mmaped, such as libraries
1027Shmem
1028 Total memory used by shared memory (shmem) and tmpfs
1029ShmemHugePages
1030 Memory used by shared memory (shmem) and tmpfs allocated
1031 with huge pages
1032ShmemPmdMapped
1033 Shared memory mapped into userspace with huge pages
1034KReclaimable
1035 Kernel allocations that the kernel will attempt to reclaim
1036 under memory pressure. Includes SReclaimable (below), and other
1037 direct allocations with a shrinker.
1038Slab
1039 in-kernel data structures cache
1040SReclaimable
1041 Part of Slab, that might be reclaimed, such as caches
1042SUnreclaim
1043 Part of Slab, that cannot be reclaimed on memory pressure
1044PageTables
1045 amount of memory dedicated to the lowest level of page
1046 tables.
1047NFS_Unstable
1048 Always zero. Previous counted pages which had been written to
1049 the server, but has not been committed to stable storage.
1050Bounce
1051 Memory used for block device "bounce buffers"
1052WritebackTmp
1053 Memory used by FUSE for temporary writeback buffers
1054CommitLimit
1055 Based on the overcommit ratio ('vm.overcommit_ratio'),
1056 this is the total amount of memory currently available to
1057 be allocated on the system. This limit is only adhered to
1058 if strict overcommit accounting is enabled (mode 2 in
1059 'vm.overcommit_memory').
1060
1061 The CommitLimit is calculated with the following formula::
1062
1063 CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
1064 overcommit_ratio / 100 + [total swap pages]
1065
1066 For example, on a system with 1G of physical RAM and 7G
1067 of swap with a `vm.overcommit_ratio` of 30 it would
1068 yield a CommitLimit of 7.3G.
1069
1070 For more details, see the memory overcommit documentation
1071 in vm/overcommit-accounting.
1072Committed_AS
1073 The amount of memory presently allocated on the system.
1074 The committed memory is a sum of all of the memory which
1075 has been allocated by processes, even if it has not been
1076 "used" by them as of yet. A process which malloc()'s 1G
1077 of memory, but only touches 300M of it will show up as
1078 using 1G. This 1G is memory which has been "committed" to
1079 by the VM and can be used at any time by the allocating
1080 application. With strict overcommit enabled on the system
1081 (mode 2 in 'vm.overcommit_memory'), allocations which would
1082 exceed the CommitLimit (detailed above) will not be permitted.
1083 This is useful if one needs to guarantee that processes will
1084 not fail due to lack of memory once that memory has been
1085 successfully allocated.
1086VmallocTotal
1087 total size of vmalloc memory area
1088VmallocUsed
1089 amount of vmalloc area which is used
1090VmallocChunk
1091 largest contiguous block of vmalloc area which is free
1092Percpu
1093 Memory allocated to the percpu allocator used to back percpu
1094 allocations. This stat excludes the cost of metadata.
1095
1096vmallocinfo
1097~~~~~~~~~~~
1098
1099Provides information about vmalloced/vmaped areas. One line per area,
1100containing the virtual address range of the area, size in bytes,
1101caller information of the creator, and optional information depending
1102on the kind of area:
1103
1104 ========== ===================================================
1105 pages=nr number of pages
1106 phys=addr if a physical address was specified
1107 ioremap I/O mapping (ioremap() and friends)
1108 vmalloc vmalloc() area
1109 vmap vmap()ed pages
1110 user VM_USERMAP area
1111 vpages buffer for pages pointers was vmalloced (huge area)
1112 N<node>=nr (Only on NUMA kernels)
1113 Number of pages allocated on memory node <node>
1114 ========== ===================================================
1115
1116::
1117
1118 > cat /proc/vmallocinfo
1119 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
1120 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
1121 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
1122 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
1123 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
1124 phys=7fee8000 ioremap
1125 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
1126 phys=7fee7000 ioremap
1127 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
1128 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
1129 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
1130 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
1131 pages=2 vmalloc N1=2
1132 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
1133 /0x130 [x_tables] pages=4 vmalloc N0=4
1134 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
1135 pages=14 vmalloc N2=14
1136 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
1137 pages=4 vmalloc N1=4
1138 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
1139 pages=2 vmalloc N1=2
1140 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
1141 pages=10 vmalloc N0=10
1142
1143
1144softirqs
1145~~~~~~~~
1146
1147Provides counts of softirq handlers serviced since boot time, for each CPU.
1148
1149::
1150
1151 > cat /proc/softirqs
1152 CPU0 CPU1 CPU2 CPU3
1153 HI: 0 0 0 0
1154 TIMER: 27166 27120 27097 27034
1155 NET_TX: 0 0 0 17
1156 NET_RX: 42 0 0 39
1157 BLOCK: 0 0 107 1121
1158 TASKLET: 0 0 0 290
1159 SCHED: 27035 26983 26971 26746
1160 HRTIMER: 0 0 0 0
1161 RCU: 1678 1769 2178 2250
1162
1163
11641.3 IDE devices in /proc/ide
1165----------------------------
1166
1167The subdirectory /proc/ide contains information about all IDE devices of which
1168the kernel is aware. There is one subdirectory for each IDE controller, the
1169file drivers and a link for each IDE device, pointing to the device directory
1170in the controller specific subtree.
1171
1172The file 'drivers' contains general information about the drivers used for the
1173IDE devices::
1174
1175 > cat /proc/ide/drivers
1176 ide-cdrom version 4.53
1177 ide-disk version 1.08
1178
1179More detailed information can be found in the controller specific
1180subdirectories. These are named ide0, ide1 and so on. Each of these
1181directories contains the files shown in table 1-6.
1182
1183
1184.. table:: Table 1-6: IDE controller info in /proc/ide/ide?
1185
1186 ======= =======================================
1187 File Content
1188 ======= =======================================
1189 channel IDE channel (0 or 1)
1190 config Configuration (only for PCI/IDE bridge)
1191 mate Mate name
1192 model Type/Chipset of IDE controller
1193 ======= =======================================
1194
1195Each device connected to a controller has a separate subdirectory in the
1196controllers directory. The files listed in table 1-7 are contained in these
1197directories.
1198
1199
1200.. table:: Table 1-7: IDE device information
1201
1202 ================ ==========================================
1203 File Content
1204 ================ ==========================================
1205 cache The cache
1206 capacity Capacity of the medium (in 512Byte blocks)
1207 driver driver and version
1208 geometry physical and logical geometry
1209 identify device identify block
1210 media media type
1211 model device identifier
1212 settings device setup
1213 smart_thresholds IDE disk management thresholds
1214 smart_values IDE disk management values
1215 ================ ==========================================
1216
1217The most interesting file is ``settings``. This file contains a nice
1218overview of the drive parameters::
1219
1220 # cat /proc/ide/ide0/hda/settings
1221 name value min max mode
1222 ---- ----- --- --- ----
1223 bios_cyl 526 0 65535 rw
1224 bios_head 255 0 255 rw
1225 bios_sect 63 0 63 rw
1226 breada_readahead 4 0 127 rw
1227 bswap 0 0 1 r
1228 file_readahead 72 0 2097151 rw
1229 io_32bit 0 0 3 rw
1230 keepsettings 0 0 1 rw
1231 max_kb_per_request 122 1 127 rw
1232 multcount 0 0 8 rw
1233 nice1 1 0 1 rw
1234 nowerr 0 0 1 rw
1235 pio_mode write-only 0 255 w
1236 slow 0 0 1 rw
1237 unmaskirq 0 0 1 rw
1238 using_dma 0 0 1 rw
1239
1240
12411.4 Networking info in /proc/net
1242--------------------------------
1243
1244The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
1245additional values you get for IP version 6 if you configure the kernel to
1246support this. Table 1-9 lists the files and their meaning.
1247
1248
1249.. table:: Table 1-8: IPv6 info in /proc/net
1250
1251 ========== =====================================================
1252 File Content
1253 ========== =====================================================
1254 udp6 UDP sockets (IPv6)
1255 tcp6 TCP sockets (IPv6)
1256 raw6 Raw device statistics (IPv6)
1257 igmp6 IP multicast addresses, which this host joined (IPv6)
1258 if_inet6 List of IPv6 interface addresses
1259 ipv6_route Kernel routing table for IPv6
1260 rt6_stats Global IPv6 routing tables statistics
1261 sockstat6 Socket statistics (IPv6)
1262 snmp6 Snmp data (IPv6)
1263 ========== =====================================================
1264
1265.. table:: Table 1-9: Network info in /proc/net
1266
1267 ============= ================================================================
1268 File Content
1269 ============= ================================================================
1270 arp Kernel ARP table
1271 dev network devices with statistics
1272 dev_mcast the Layer2 multicast groups a device is listening too
1273 (interface index, label, number of references, number of bound
1274 addresses).
1275 dev_stat network device status
1276 ip_fwchains Firewall chain linkage
1277 ip_fwnames Firewall chain names
1278 ip_masq Directory containing the masquerading tables
1279 ip_masquerade Major masquerading table
1280 netstat Network statistics
1281 raw raw device statistics
1282 route Kernel routing table
1283 rpc Directory containing rpc info
1284 rt_cache Routing cache
1285 snmp SNMP data
1286 sockstat Socket statistics
1287 tcp TCP sockets
1288 udp UDP sockets
1289 unix UNIX domain sockets
1290 wireless Wireless interface data (Wavelan etc)
1291 igmp IP multicast addresses, which this host joined
1292 psched Global packet scheduler parameters.
1293 netlink List of PF_NETLINK sockets
1294 ip_mr_vifs List of multicast virtual interfaces
1295 ip_mr_cache List of multicast routing cache
1296 ============= ================================================================
1297
1298You can use this information to see which network devices are available in
1299your system and how much traffic was routed over those devices::
1300
1301 > cat /proc/net/dev
1302 Inter-|Receive |[...
1303 face |bytes packets errs drop fifo frame compressed multicast|[...
1304 lo: 908188 5596 0 0 0 0 0 0 [...
1305 ppp0:15475140 20721 410 0 0 410 0 0 [...
1306 eth0: 614530 7085 0 0 0 0 0 1 [...
1307
1308 ...] Transmit
1309 ...] bytes packets errs drop fifo colls carrier compressed
1310 ...] 908188 5596 0 0 0 0 0 0
1311 ...] 1375103 17405 0 0 0 0 0 0
1312 ...] 1703981 5535 0 0 0 3 0 0
1313
1314In addition, each Channel Bond interface has its own directory. For
1315example, the bond0 device will have a directory called /proc/net/bond0/.
1316It will contain information that is specific to that bond, such as the
1317current slaves of the bond, the link status of the slaves, and how
1318many times the slaves link has failed.
1319
13201.5 SCSI info
1321-------------
1322
1323If you have a SCSI host adapter in your system, you'll find a subdirectory
1324named after the driver for this adapter in /proc/scsi. You'll also see a list
1325of all recognized SCSI devices in /proc/scsi::
1326
1327 >cat /proc/scsi/scsi
1328 Attached devices:
1329 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1330 Vendor: IBM Model: DGHS09U Rev: 03E0
1331 Type: Direct-Access ANSI SCSI revision: 03
1332 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1333 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1334 Type: CD-ROM ANSI SCSI revision: 02
1335
1336
1337The directory named after the driver has one file for each adapter found in
1338the system. These files contain information about the controller, including
1339the used IRQ and the IO address range. The amount of information shown is
1340dependent on the adapter you use. The example shows the output for an Adaptec
1341AHA-2940 SCSI adapter::
1342
1343 > cat /proc/scsi/aic7xxx/0
1344
1345 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1346 Compile Options:
1347 TCQ Enabled By Default : Disabled
1348 AIC7XXX_PROC_STATS : Disabled
1349 AIC7XXX_RESET_DELAY : 5
1350 Adapter Configuration:
1351 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1352 Ultra Wide Controller
1353 PCI MMAPed I/O Base: 0xeb001000
1354 Adapter SEEPROM Config: SEEPROM found and used.
1355 Adaptec SCSI BIOS: Enabled
1356 IRQ: 10
1357 SCBs: Active 0, Max Active 2,
1358 Allocated 15, HW 16, Page 255
1359 Interrupts: 160328
1360 BIOS Control Word: 0x18b6
1361 Adapter Control Word: 0x005b
1362 Extended Translation: Enabled
1363 Disconnect Enable Flags: 0xffff
1364 Ultra Enable Flags: 0x0001
1365 Tag Queue Enable Flags: 0x0000
1366 Ordered Queue Tag Flags: 0x0000
1367 Default Tag Queue Depth: 8
1368 Tagged Queue By Device array for aic7xxx host instance 0:
1369 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1370 Actual queue depth per device for aic7xxx host instance 0:
1371 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1372 Statistics:
1373 (scsi0:0:0:0)
1374 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1375 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1376 Total transfers 160151 (74577 reads and 85574 writes)
1377 (scsi0:0:6:0)
1378 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1379 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1380 Total transfers 0 (0 reads and 0 writes)
1381
1382
13831.6 Parallel port info in /proc/parport
1384---------------------------------------
1385
1386The directory /proc/parport contains information about the parallel ports of
1387your system. It has one subdirectory for each port, named after the port
1388number (0,1,2,...).
1389
1390These directories contain the four files shown in Table 1-10.
1391
1392
1393.. table:: Table 1-10: Files in /proc/parport
1394
1395 ========= ====================================================================
1396 File Content
1397 ========= ====================================================================
1398 autoprobe Any IEEE-1284 device ID information that has been acquired.
1399 devices list of the device drivers using that port. A + will appear by the
1400 name of the device currently using the port (it might not appear
1401 against any).
1402 hardware Parallel port's base address, IRQ line and DMA channel.
1403 irq IRQ that parport is using for that port. This is in a separate
1404 file to allow you to alter it by writing a new value in (IRQ
1405 number or none).
1406 ========= ====================================================================
1407
14081.7 TTY info in /proc/tty
1409-------------------------
1410
1411Information about the available and actually used tty's can be found in the
1412directory /proc/tty. You'll find entries for drivers and line disciplines in
1413this directory, as shown in Table 1-11.
1414
1415
1416.. table:: Table 1-11: Files in /proc/tty
1417
1418 ============= ==============================================
1419 File Content
1420 ============= ==============================================
1421 drivers list of drivers and their usage
1422 ldiscs registered line disciplines
1423 driver/serial usage statistic and status of single tty lines
1424 ============= ==============================================
1425
1426To see which tty's are currently in use, you can simply look into the file
1427/proc/tty/drivers::
1428
1429 > cat /proc/tty/drivers
1430 pty_slave /dev/pts 136 0-255 pty:slave
1431 pty_master /dev/ptm 128 0-255 pty:master
1432 pty_slave /dev/ttyp 3 0-255 pty:slave
1433 pty_master /dev/pty 2 0-255 pty:master
1434 serial /dev/cua 5 64-67 serial:callout
1435 serial /dev/ttyS 4 64-67 serial
1436 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1437 /dev/ptmx /dev/ptmx 5 2 system
1438 /dev/console /dev/console 5 1 system:console
1439 /dev/tty /dev/tty 5 0 system:/dev/tty
1440 unknown /dev/tty 4 1-63 console
1441
1442
14431.8 Miscellaneous kernel statistics in /proc/stat
1444-------------------------------------------------
1445
1446Various pieces of information about kernel activity are available in the
1447/proc/stat file. All of the numbers reported in this file are aggregates
1448since the system first booted. For a quick look, simply cat the file::
1449
1450 > cat /proc/stat
1451 cpu 2255 34 2290 22625563 6290 127 456 0 0 0
1452 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1453 cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1454 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1455 ctxt 1990473
1456 btime 1062191376
1457 processes 2915
1458 procs_running 1
1459 procs_blocked 0
1460 softirq 183433 0 21755 12 39 1137 231 21459 2263
1461
1462The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1463lines. These numbers identify the amount of time the CPU has spent performing
1464different kinds of work. Time units are in USER_HZ (typically hundredths of a
1465second). The meanings of the columns are as follows, from left to right:
1466
1467- user: normal processes executing in user mode
1468- nice: niced processes executing in user mode
1469- system: processes executing in kernel mode
1470- idle: twiddling thumbs
1471- iowait: In a word, iowait stands for waiting for I/O to complete. But there
1472 are several problems:
1473
1474 1. CPU will not wait for I/O to complete, iowait is the time that a task is
1475 waiting for I/O to complete. When CPU goes into idle state for
1476 outstanding task I/O, another task will be scheduled on this CPU.
1477 2. In a multi-core CPU, the task waiting for I/O to complete is not running
1478 on any CPU, so the iowait of each CPU is difficult to calculate.
1479 3. The value of iowait field in /proc/stat will decrease in certain
1480 conditions.
1481
1482 So, the iowait is not reliable by reading from /proc/stat.
1483- irq: servicing interrupts
1484- softirq: servicing softirqs
1485- steal: involuntary wait
1486- guest: running a normal guest
1487- guest_nice: running a niced guest
1488
1489The "intr" line gives counts of interrupts serviced since boot time, for each
1490of the possible system interrupts. The first column is the total of all
1491interrupts serviced including unnumbered architecture specific interrupts;
1492each subsequent column is the total for that particular numbered interrupt.
1493Unnumbered interrupts are not shown, only summed into the total.
1494
1495The "ctxt" line gives the total number of context switches across all CPUs.
1496
1497The "btime" line gives the time at which the system booted, in seconds since
1498the Unix epoch.
1499
1500The "processes" line gives the number of processes and threads created, which
1501includes (but is not limited to) those created by calls to the fork() and
1502clone() system calls.
1503
1504The "procs_running" line gives the total number of threads that are
1505running or ready to run (i.e., the total number of runnable threads).
1506
1507The "procs_blocked" line gives the number of processes currently blocked,
1508waiting for I/O to complete.
1509
1510The "softirq" line gives counts of softirqs serviced since boot time, for each
1511of the possible system softirqs. The first column is the total of all
1512softirqs serviced; each subsequent column is the total for that particular
1513softirq.
1514
1515
15161.9 Ext4 file system parameters
1517-------------------------------
1518
1519Information about mounted ext4 file systems can be found in
1520/proc/fs/ext4. Each mounted filesystem will have a directory in
1521/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1522/proc/fs/ext4/dm-0). The files in each per-device directory are shown
1523in Table 1-12, below.
1524
1525.. table:: Table 1-12: Files in /proc/fs/ext4/<devname>
1526
1527 ============== ==========================================================
1528 File Content
1529 mb_groups details of multiblock allocator buddy cache of free blocks
1530 ============== ==========================================================
1531
15321.10 /proc/consoles
1533-------------------
1534Shows registered system console lines.
1535
1536To see which character device lines are currently used for the system console
1537/dev/console, you may simply look into the file /proc/consoles::
1538
1539 > cat /proc/consoles
1540 tty0 -WU (ECp) 4:7
1541 ttyS0 -W- (Ep) 4:64
1542
1543The columns are:
1544
1545+--------------------+-------------------------------------------------------+
1546| device | name of the device |
1547+====================+=======================================================+
1548| operations | * R = can do read operations |
1549| | * W = can do write operations |
1550| | * U = can do unblank |
1551+--------------------+-------------------------------------------------------+
1552| flags | * E = it is enabled |
1553| | * C = it is preferred console |
1554| | * B = it is primary boot console |
1555| | * p = it is used for printk buffer |
1556| | * b = it is not a TTY but a Braille device |
1557| | * a = it is safe to use when cpu is offline |
1558+--------------------+-------------------------------------------------------+
1559| major:minor | major and minor number of the device separated by a |
1560| | colon |
1561+--------------------+-------------------------------------------------------+
1562
1563Summary
1564-------
1565
1566The /proc file system serves information about the running system. It not only
1567allows access to process data but also allows you to request the kernel status
1568by reading files in the hierarchy.
1569
1570The directory structure of /proc reflects the types of information and makes
1571it easy, if not obvious, where to look for specific data.
1572
1573Chapter 2: Modifying System Parameters
1574======================================
1575
1576In This Chapter
1577---------------
1578
1579* Modifying kernel parameters by writing into files found in /proc/sys
1580* Exploring the files which modify certain parameters
1581* Review of the /proc/sys file tree
1582
1583------------------------------------------------------------------------------
1584
1585A very interesting part of /proc is the directory /proc/sys. This is not only
1586a source of information, it also allows you to change parameters within the
1587kernel. Be very careful when attempting this. You can optimize your system,
1588but you can also cause it to crash. Never alter kernel parameters on a
1589production system. Set up a development machine and test to make sure that
1590everything works the way you want it to. You may have no alternative but to
1591reboot the machine once an error has been made.
1592
1593To change a value, simply echo the new value into the file.
1594You need to be root to do this. You can create your own boot script
1595to perform this every time your system boots.
1596
1597The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1598general things in the operation of the Linux kernel. Since some of the files
1599can inadvertently disrupt your system, it is advisable to read both
1600documentation and source before actually making adjustments. In any case, be
1601very careful when writing to any of these files. The entries in /proc may
1602change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1603review the kernel documentation in the directory /usr/src/linux/Documentation.
1604This chapter is heavily based on the documentation included in the pre 2.2
1605kernels, and became part of it in version 2.2.1 of the Linux kernel.
1606
1607Please see: Documentation/admin-guide/sysctl/ directory for descriptions of these
1608entries.
1609
1610Summary
1611-------
1612
1613Certain aspects of kernel behavior can be modified at runtime, without the
1614need to recompile the kernel, or even to reboot the system. The files in the
1615/proc/sys tree can not only be read, but also modified. You can use the echo
1616command to write value into these files, thereby changing the default settings
1617of the kernel.
1618
1619
1620Chapter 3: Per-process Parameters
1621=================================
1622
16233.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1624--------------------------------------------------------------------------------
1625
1626These files can be used to adjust the badness heuristic used to select which
1627process gets killed in out of memory (oom) conditions.
1628
1629The badness heuristic assigns a value to each candidate task ranging from 0
1630(never kill) to 1000 (always kill) to determine which process is targeted. The
1631units are roughly a proportion along that range of allowed memory the process
1632may allocate from based on an estimation of its current memory and swap use.
1633For example, if a task is using all allowed memory, its badness score will be
16341000. If it is using half of its allowed memory, its score will be 500.
1635
1636The amount of "allowed" memory depends on the context in which the oom killer
1637was called. If it is due to the memory assigned to the allocating task's cpuset
1638being exhausted, the allowed memory represents the set of mems assigned to that
1639cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1640memory represents the set of mempolicy nodes. If it is due to a memory
1641limit (or swap limit) being reached, the allowed memory is that configured
1642limit. Finally, if it is due to the entire system being out of memory, the
1643allowed memory represents all allocatable resources.
1644
1645The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1646is used to determine which task to kill. Acceptable values range from -1000
1647(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1648polarize the preference for oom killing either by always preferring a certain
1649task or completely disabling it. The lowest possible value, -1000, is
1650equivalent to disabling oom killing entirely for that task since it will always
1651report a badness score of 0.
1652
1653Consequently, it is very simple for userspace to define the amount of memory to
1654consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1655example, is roughly equivalent to allowing the remainder of tasks sharing the
1656same system, cpuset, mempolicy, or memory controller resources to use at least
165750% more memory. A value of -500, on the other hand, would be roughly
1658equivalent to discounting 50% of the task's allowed memory from being considered
1659as scoring against the task.
1660
1661For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1662be used to tune the badness score. Its acceptable values range from -16
1663(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1664(OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1665scaled linearly with /proc/<pid>/oom_score_adj.
1666
1667The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1668value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1669requires CAP_SYS_RESOURCE.
1670
1671
16723.2 /proc/<pid>/oom_score - Display current oom-killer score
1673-------------------------------------------------------------
1674
1675This file can be used to check the current score used by the oom-killer for
1676any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1677process should be killed in an out-of-memory situation.
1678
1679Please note that the exported value includes oom_score_adj so it is
1680effectively in range [0,2000].
1681
1682
16833.3 /proc/<pid>/io - Display the IO accounting fields
1684-------------------------------------------------------
1685
1686This file contains IO statistics for each running process.
1687
1688Example
1689~~~~~~~
1690
1691::
1692
1693 test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1694 [1] 3828
1695
1696 test:/tmp # cat /proc/3828/io
1697 rchar: 323934931
1698 wchar: 323929600
1699 syscr: 632687
1700 syscw: 632675
1701 read_bytes: 0
1702 write_bytes: 323932160
1703 cancelled_write_bytes: 0
1704
1705
1706Description
1707~~~~~~~~~~~
1708
1709rchar
1710^^^^^
1711
1712I/O counter: chars read
1713The number of bytes which this task has caused to be read from storage. This
1714is simply the sum of bytes which this process passed to read() and pread().
1715It includes things like tty IO and it is unaffected by whether or not actual
1716physical disk IO was required (the read might have been satisfied from
1717pagecache).
1718
1719
1720wchar
1721^^^^^
1722
1723I/O counter: chars written
1724The number of bytes which this task has caused, or shall cause to be written
1725to disk. Similar caveats apply here as with rchar.
1726
1727
1728syscr
1729^^^^^
1730
1731I/O counter: read syscalls
1732Attempt to count the number of read I/O operations, i.e. syscalls like read()
1733and pread().
1734
1735
1736syscw
1737^^^^^
1738
1739I/O counter: write syscalls
1740Attempt to count the number of write I/O operations, i.e. syscalls like
1741write() and pwrite().
1742
1743
1744read_bytes
1745^^^^^^^^^^
1746
1747I/O counter: bytes read
1748Attempt to count the number of bytes which this process really did cause to
1749be fetched from the storage layer. Done at the submit_bio() level, so it is
1750accurate for block-backed filesystems. <please add status regarding NFS and
1751CIFS at a later time>
1752
1753
1754write_bytes
1755^^^^^^^^^^^
1756
1757I/O counter: bytes written
1758Attempt to count the number of bytes which this process caused to be sent to
1759the storage layer. This is done at page-dirtying time.
1760
1761
1762cancelled_write_bytes
1763^^^^^^^^^^^^^^^^^^^^^
1764
1765The big inaccuracy here is truncate. If a process writes 1MB to a file and
1766then deletes the file, it will in fact perform no writeout. But it will have
1767been accounted as having caused 1MB of write.
1768In other words: The number of bytes which this process caused to not happen,
1769by truncating pagecache. A task can cause "negative" IO too. If this task
1770truncates some dirty pagecache, some IO which another task has been accounted
1771for (in its write_bytes) will not be happening. We _could_ just subtract that
1772from the truncating task's write_bytes, but there is information loss in doing
1773that.
1774
1775
1776.. Note::
1777
1778 At its current implementation state, this is a bit racy on 32-bit machines:
1779 if process A reads process B's /proc/pid/io while process B is updating one
1780 of those 64-bit counters, process A could see an intermediate result.
1781
1782
1783More information about this can be found within the taskstats documentation in
1784Documentation/accounting.
1785
17863.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1787---------------------------------------------------------------
1788When a process is dumped, all anonymous memory is written to a core file as
1789long as the size of the core file isn't limited. But sometimes we don't want
1790to dump some memory segments, for example, huge shared memory or DAX.
1791Conversely, sometimes we want to save file-backed memory segments into a core
1792file, not only the individual files.
1793
1794/proc/<pid>/coredump_filter allows you to customize which memory segments
1795will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1796of memory types. If a bit of the bitmask is set, memory segments of the
1797corresponding memory type are dumped, otherwise they are not dumped.
1798
1799The following 9 memory types are supported:
1800
1801 - (bit 0) anonymous private memory
1802 - (bit 1) anonymous shared memory
1803 - (bit 2) file-backed private memory
1804 - (bit 3) file-backed shared memory
1805 - (bit 4) ELF header pages in file-backed private memory areas (it is
1806 effective only if the bit 2 is cleared)
1807 - (bit 5) hugetlb private memory
1808 - (bit 6) hugetlb shared memory
1809 - (bit 7) DAX private memory
1810 - (bit 8) DAX shared memory
1811
1812 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1813 are always dumped regardless of the bitmask status.
1814
1815 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
1816 only affected by bit 5-6, and DAX is only affected by bits 7-8.
1817
1818The default value of coredump_filter is 0x33; this means all anonymous memory
1819segments, ELF header pages and hugetlb private memory are dumped.
1820
1821If you don't want to dump all shared memory segments attached to pid 1234,
1822write 0x31 to the process's proc file::
1823
1824 $ echo 0x31 > /proc/1234/coredump_filter
1825
1826When a new process is created, the process inherits the bitmask status from its
1827parent. It is useful to set up coredump_filter before the program runs.
1828For example::
1829
1830 $ echo 0x7 > /proc/self/coredump_filter
1831 $ ./some_program
1832
18333.5 /proc/<pid>/mountinfo - Information about mounts
1834--------------------------------------------------------
1835
1836This file contains lines of the form::
1837
1838 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1839 (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1840
1841 (1) mount ID: unique identifier of the mount (may be reused after umount)
1842 (2) parent ID: ID of parent (or of self for the top of the mount tree)
1843 (3) major:minor: value of st_dev for files on filesystem
1844 (4) root: root of the mount within the filesystem
1845 (5) mount point: mount point relative to the process's root
1846 (6) mount options: per mount options
1847 (7) optional fields: zero or more fields of the form "tag[:value]"
1848 (8) separator: marks the end of the optional fields
1849 (9) filesystem type: name of filesystem of the form "type[.subtype]"
1850 (10) mount source: filesystem specific information or "none"
1851 (11) super options: per super block options
1852
1853Parsers should ignore all unrecognised optional fields. Currently the
1854possible optional fields are:
1855
1856================ ==============================================================
1857shared:X mount is shared in peer group X
1858master:X mount is slave to peer group X
1859propagate_from:X mount is slave and receives propagation from peer group X [#]_
1860unbindable mount is unbindable
1861================ ==============================================================
1862
1863.. [#] X is the closest dominant peer group under the process's root. If
1864 X is the immediate master of the mount, or if there's no dominant peer
1865 group under the same root, then only the "master:X" field is present
1866 and not the "propagate_from:X" field.
1867
1868For more information on mount propagation see:
1869
1870 Documentation/filesystems/sharedsubtree.rst
1871
1872
18733.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1874--------------------------------------------------------
1875These files provide a method to access a task's comm value. It also allows for
1876a task to set its own or one of its thread siblings comm value. The comm value
1877is limited in size compared to the cmdline value, so writing anything longer
1878then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1879comm value.
1880
1881
18823.7 /proc/<pid>/task/<tid>/children - Information about task children
1883-------------------------------------------------------------------------
1884This file provides a fast way to retrieve first level children pids
1885of a task pointed by <pid>/<tid> pair. The format is a space separated
1886stream of pids.
1887
1888Note the "first level" here -- if a child has its own children they will
1889not be listed here; one needs to read /proc/<children-pid>/task/<tid>/children
1890to obtain the descendants.
1891
1892Since this interface is intended to be fast and cheap it doesn't
1893guarantee to provide precise results and some children might be
1894skipped, especially if they've exited right after we printed their
1895pids, so one needs to either stop or freeze processes being inspected
1896if precise results are needed.
1897
1898
18993.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
1900---------------------------------------------------------------
1901This file provides information associated with an opened file. The regular
1902files have at least three fields -- 'pos', 'flags' and 'mnt_id'. The 'pos'
1903represents the current offset of the opened file in decimal form [see lseek(2)
1904for details], 'flags' denotes the octal O_xxx mask the file has been
1905created with [see open(2) for details] and 'mnt_id' represents mount ID of
1906the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1907for details].
1908
1909A typical output is::
1910
1911 pos: 0
1912 flags: 0100002
1913 mnt_id: 19
1914
1915All locks associated with a file descriptor are shown in its fdinfo too::
1916
1917 lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF
1918
1919The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1920pair provide additional information particular to the objects they represent.
1921
1922Eventfd files
1923~~~~~~~~~~~~~
1924
1925::
1926
1927 pos: 0
1928 flags: 04002
1929 mnt_id: 9
1930 eventfd-count: 5a
1931
1932where 'eventfd-count' is hex value of a counter.
1933
1934Signalfd files
1935~~~~~~~~~~~~~~
1936
1937::
1938
1939 pos: 0
1940 flags: 04002
1941 mnt_id: 9
1942 sigmask: 0000000000000200
1943
1944where 'sigmask' is hex value of the signal mask associated
1945with a file.
1946
1947Epoll files
1948~~~~~~~~~~~
1949
1950::
1951
1952 pos: 0
1953 flags: 02
1954 mnt_id: 9
1955 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7
1956
1957where 'tfd' is a target file descriptor number in decimal form,
1958'events' is events mask being watched and the 'data' is data
1959associated with a target [see epoll(7) for more details].
1960
1961The 'pos' is current offset of the target file in decimal form
1962[see lseek(2)], 'ino' and 'sdev' are inode and device numbers
1963where target file resides, all in hex format.
1964
1965Fsnotify files
1966~~~~~~~~~~~~~~
1967For inotify files the format is the following::
1968
1969 pos: 0
1970 flags: 02000000
1971 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1972
1973where 'wd' is a watch descriptor in decimal form, i.e. a target file
1974descriptor number, 'ino' and 'sdev' are inode and device where the
1975target file resides and the 'mask' is the mask of events, all in hex
1976form [see inotify(7) for more details].
1977
1978If the kernel was built with exportfs support, the path to the target
1979file is encoded as a file handle. The file handle is provided by three
1980fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1981format.
1982
1983If the kernel is built without exportfs support the file handle won't be
1984printed out.
1985
1986If there is no inotify mark attached yet the 'inotify' line will be omitted.
1987
1988For fanotify files the format is::
1989
1990 pos: 0
1991 flags: 02
1992 mnt_id: 9
1993 fanotify flags:10 event-flags:0
1994 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1995 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1996
1997where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1998call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1999flags associated with mark which are tracked separately from events
2000mask. 'ino' and 'sdev' are target inode and device, 'mask' is the events
2001mask and 'ignored_mask' is the mask of events which are to be ignored.
2002All are in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
2003provide information about flags and mask used in fanotify_mark
2004call [see fsnotify manpage for details].
2005
2006While the first three lines are mandatory and always printed, the rest is
2007optional and may be omitted if no marks created yet.
2008
2009Timerfd files
2010~~~~~~~~~~~~~
2011
2012::
2013
2014 pos: 0
2015 flags: 02
2016 mnt_id: 9
2017 clockid: 0
2018 ticks: 0
2019 settime flags: 01
2020 it_value: (0, 49406829)
2021 it_interval: (1, 0)
2022
2023where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
2024that have occurred [see timerfd_create(2) for details]. 'settime flags' are
2025flags in octal form been used to setup the timer [see timerfd_settime(2) for
2026details]. 'it_value' is remaining time until the timer expiration.
2027'it_interval' is the interval for the timer. Note the timer might be set up
2028with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
2029still exhibits timer's remaining time.
2030
20313.9 /proc/<pid>/map_files - Information about memory mapped files
2032---------------------------------------------------------------------
2033This directory contains symbolic links which represent memory mapped files
2034the process is maintaining. Example output::
2035
2036 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
2037 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
2038 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
2039 | ...
2040 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
2041 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
2042
2043The name of a link represents the virtual memory bounds of a mapping, i.e.
2044vm_area_struct::vm_start-vm_area_struct::vm_end.
2045
2046The main purpose of the map_files is to retrieve a set of memory mapped
2047files in a fast way instead of parsing /proc/<pid>/maps or
2048/proc/<pid>/smaps, both of which contain many more records. At the same
2049time one can open(2) mappings from the listings of two processes and
2050comparing their inode numbers to figure out which anonymous memory areas
2051are actually shared.
2052
20533.10 /proc/<pid>/timerslack_ns - Task timerslack value
2054---------------------------------------------------------
2055This file provides the value of the task's timerslack value in nanoseconds.
2056This value specifies an amount of time that normal timers may be deferred
2057in order to coalesce timers and avoid unnecessary wakeups.
2058
2059This allows a task's interactivity vs power consumption tradeoff to be
2060adjusted.
2061
2062Writing 0 to the file will set the task's timerslack to the default value.
2063
2064Valid values are from 0 - ULLONG_MAX
2065
2066An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
2067permissions on the task specified to change its timerslack_ns value.
2068
20693.11 /proc/<pid>/patch_state - Livepatch patch operation state
2070-----------------------------------------------------------------
2071When CONFIG_LIVEPATCH is enabled, this file displays the value of the
2072patch state for the task.
2073
2074A value of '-1' indicates that no patch is in transition.
2075
2076A value of '0' indicates that a patch is in transition and the task is
2077unpatched. If the patch is being enabled, then the task hasn't been
2078patched yet. If the patch is being disabled, then the task has already
2079been unpatched.
2080
2081A value of '1' indicates that a patch is in transition and the task is
2082patched. If the patch is being enabled, then the task has already been
2083patched. If the patch is being disabled, then the task hasn't been
2084unpatched yet.
2085
20863.12 /proc/<pid>/arch_status - task architecture specific status
2087-------------------------------------------------------------------
2088When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the
2089architecture specific status of the task.
2090
2091Example
2092~~~~~~~
2093
2094::
2095
2096 $ cat /proc/6753/arch_status
2097 AVX512_elapsed_ms: 8
2098
2099Description
2100~~~~~~~~~~~
2101
2102x86 specific entries
2103~~~~~~~~~~~~~~~~~~~~~
2104
2105AVX512_elapsed_ms
2106^^^^^^^^^^^^^^^^^^
2107
2108 If AVX512 is supported on the machine, this entry shows the milliseconds
2109 elapsed since the last time AVX512 usage was recorded. The recording
2110 happens on a best effort basis when a task is scheduled out. This means
2111 that the value depends on two factors:
2112
2113 1) The time which the task spent on the CPU without being scheduled
2114 out. With CPU isolation and a single runnable task this can take
2115 several seconds.
2116
2117 2) The time since the task was scheduled out last. Depending on the
2118 reason for being scheduled out (time slice exhausted, syscall ...)
2119 this can be arbitrary long time.
2120
2121 As a consequence the value cannot be considered precise and authoritative
2122 information. The application which uses this information has to be aware
2123 of the overall scenario on the system in order to determine whether a
2124 task is a real AVX512 user or not. Precise information can be obtained
2125 with performance counters.
2126
2127 A special value of '-1' indicates that no AVX512 usage was recorded, thus
2128 the task is unlikely an AVX512 user, but depends on the workload and the
2129 scheduling scenario, it also could be a false negative mentioned above.
2130
2131Chapter 4: Configuring procfs
2132=============================
2133
21344.1 Mount options
2135---------------------
2136
2137The following mount options are supported:
2138
2139 ========= ========================================================
2140 hidepid= Set /proc/<pid>/ access mode.
2141 gid= Set the group authorized to learn processes information.
2142 subset= Show only the specified subset of procfs.
2143 ========= ========================================================
2144
2145hidepid=off or hidepid=0 means classic mode - everybody may access all
2146/proc/<pid>/ directories (default).
2147
2148hidepid=noaccess or hidepid=1 means users may not access any /proc/<pid>/
2149directories but their own. Sensitive files like cmdline, sched*, status are now
2150protected against other users. This makes it impossible to learn whether any
2151user runs specific program (given the program doesn't reveal itself by its
2152behaviour). As an additional bonus, as /proc/<pid>/cmdline is unaccessible for
2153other users, poorly written programs passing sensitive information via program
2154arguments are now protected against local eavesdroppers.
2155
2156hidepid=invisible or hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be
2157fully invisible to other users. It doesn't mean that it hides a fact whether a
2158process with a specific pid value exists (it can be learned by other means, e.g.
2159by "kill -0 $PID"), but it hides process' uid and gid, which may be learned by
2160stat()'ing /proc/<pid>/ otherwise. It greatly complicates an intruder's task of
2161gathering information about running processes, whether some daemon runs with
2162elevated privileges, whether other user runs some sensitive program, whether
2163other users run any program at all, etc.
2164
2165hidepid=ptraceable or hidepid=4 means that procfs should only contain
2166/proc/<pid>/ directories that the caller can ptrace.
2167
2168gid= defines a group authorized to learn processes information otherwise
2169prohibited by hidepid=. If you use some daemon like identd which needs to learn
2170information about processes information, just add identd to this group.
2171
2172subset=pid hides all top level files and directories in the procfs that
2173are not related to tasks.
2174
2175Chapter 5: Filesystem behavior
2176==============================
2177
2178Originally, before the advent of pid namepsace, procfs was a global file
2179system. It means that there was only one procfs instance in the system.
2180
2181When pid namespace was added, a separate procfs instance was mounted in
2182each pid namespace. So, procfs mount options are global among all
2183mountpoints within the same namespace::
2184
2185 # grep ^proc /proc/mounts
2186 proc /proc proc rw,relatime,hidepid=2 0 0
2187
2188 # strace -e mount mount -o hidepid=1 -t proc proc /tmp/proc
2189 mount("proc", "/tmp/proc", "proc", 0, "hidepid=1") = 0
2190 +++ exited with 0 +++
2191
2192 # grep ^proc /proc/mounts
2193 proc /proc proc rw,relatime,hidepid=2 0 0
2194 proc /tmp/proc proc rw,relatime,hidepid=2 0 0
2195
2196and only after remounting procfs mount options will change at all
2197mountpoints::
2198
2199 # mount -o remount,hidepid=1 -t proc proc /tmp/proc
2200
2201 # grep ^proc /proc/mounts
2202 proc /proc proc rw,relatime,hidepid=1 0 0
2203 proc /tmp/proc proc rw,relatime,hidepid=1 0 0
2204
2205This behavior is different from the behavior of other filesystems.
2206
2207The new procfs behavior is more like other filesystems. Each procfs mount
2208creates a new procfs instance. Mount options affect own procfs instance.
2209It means that it became possible to have several procfs instances
2210displaying tasks with different filtering options in one pid namespace::
2211
2212 # mount -o hidepid=invisible -t proc proc /proc
2213 # mount -o hidepid=noaccess -t proc proc /tmp/proc
2214 # grep ^proc /proc/mounts
2215 proc /proc proc rw,relatime,hidepid=invisible 0 0
2216 proc /tmp/proc proc rw,relatime,hidepid=noaccess 0 0
1.. SPDX-License-Identifier: GPL-2.0
2
3====================
4The /proc Filesystem
5====================
6
7===================== ======================================= ================
8/proc/sys Terrehon Bowden <terrehon@pacbell.net>, October 7 1999
9 Bodo Bauer <bb@ricochet.net>
102.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
11move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
12fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009
13===================== ======================================= ================
14
15
16
17.. Table of Contents
18
19 0 Preface
20 0.1 Introduction/Credits
21 0.2 Legal Stuff
22
23 1 Collecting System Information
24 1.1 Process-Specific Subdirectories
25 1.2 Kernel data
26 1.3 IDE devices in /proc/ide
27 1.4 Networking info in /proc/net
28 1.5 SCSI info
29 1.6 Parallel port info in /proc/parport
30 1.7 TTY info in /proc/tty
31 1.8 Miscellaneous kernel statistics in /proc/stat
32 1.9 Ext4 file system parameters
33
34 2 Modifying System Parameters
35
36 3 Per-Process Parameters
37 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
38 score
39 3.2 /proc/<pid>/oom_score - Display current oom-killer score
40 3.3 /proc/<pid>/io - Display the IO accounting fields
41 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
42 3.5 /proc/<pid>/mountinfo - Information about mounts
43 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
44 3.7 /proc/<pid>/task/<tid>/children - Information about task children
45 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
46 3.9 /proc/<pid>/map_files - Information about memory mapped files
47 3.10 /proc/<pid>/timerslack_ns - Task timerslack value
48 3.11 /proc/<pid>/patch_state - Livepatch patch operation state
49 3.12 /proc/<pid>/arch_status - Task architecture specific information
50 3.13 /proc/<pid>/fd - List of symlinks to open files
51
52 4 Configuring procfs
53 4.1 Mount options
54
55 5 Filesystem behavior
56
57Preface
58=======
59
600.1 Introduction/Credits
61------------------------
62
63This documentation is part of a soon (or so we hope) to be released book on
64the SuSE Linux distribution. As there is no complete documentation for the
65/proc file system and we've used many freely available sources to write these
66chapters, it seems only fair to give the work back to the Linux community.
67This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
68afraid it's still far from complete, but we hope it will be useful. As far as
69we know, it is the first 'all-in-one' document about the /proc file system. It
70is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
71SPARC, AXP, etc., features, you probably won't find what you are looking for.
72It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
73additions and patches are welcome and will be added to this document if you
74mail them to Bodo.
75
76We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
77other people for help compiling this documentation. We'd also like to extend a
78special thank you to Andi Kleen for documentation, which we relied on heavily
79to create this document, as well as the additional information he provided.
80Thanks to everybody else who contributed source or docs to the Linux kernel
81and helped create a great piece of software... :)
82
83If you have any comments, corrections or additions, please don't hesitate to
84contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
85document.
86
87The latest version of this document is available online at
88https://www.kernel.org/doc/html/latest/filesystems/proc.html
89
90If the above direction does not works for you, you could try the kernel
91mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
92comandante@zaralinux.com.
93
940.2 Legal Stuff
95---------------
96
97We don't guarantee the correctness of this document, and if you come to us
98complaining about how you screwed up your system because of incorrect
99documentation, we won't feel responsible...
100
101Chapter 1: Collecting System Information
102========================================
103
104In This Chapter
105---------------
106* Investigating the properties of the pseudo file system /proc and its
107 ability to provide information on the running Linux system
108* Examining /proc's structure
109* Uncovering various information about the kernel and the processes running
110 on the system
111
112------------------------------------------------------------------------------
113
114The proc file system acts as an interface to internal data structures in the
115kernel. It can be used to obtain information about the system and to change
116certain kernel parameters at runtime (sysctl).
117
118First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
119show you how you can use /proc/sys to change settings.
120
1211.1 Process-Specific Subdirectories
122-----------------------------------
123
124The directory /proc contains (among other things) one subdirectory for each
125process running on the system, which is named after the process ID (PID).
126
127The link 'self' points to the process reading the file system. Each process
128subdirectory has the entries listed in Table 1-1.
129
130Note that an open file descriptor to /proc/<pid> or to any of its
131contained files or subdirectories does not prevent <pid> being reused
132for some other process in the event that <pid> exits. Operations on
133open /proc/<pid> file descriptors corresponding to dead processes
134never act on any new process that the kernel may, through chance, have
135also assigned the process ID <pid>. Instead, operations on these FDs
136usually fail with ESRCH.
137
138.. table:: Table 1-1: Process specific entries in /proc
139
140 ============= ===============================================================
141 File Content
142 ============= ===============================================================
143 clear_refs Clears page referenced bits shown in smaps output
144 cmdline Command line arguments
145 cpu Current and last cpu in which it was executed (2.4)(smp)
146 cwd Link to the current working directory
147 environ Values of environment variables
148 exe Link to the executable of this process
149 fd Directory, which contains all file descriptors
150 maps Memory maps to executables and library files (2.4)
151 mem Memory held by this process
152 root Link to the root directory of this process
153 stat Process status
154 statm Process memory status information
155 status Process status in human readable form
156 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function
157 symbol the task is blocked in - or "0" if not blocked.
158 pagemap Page table
159 stack Report full stack trace, enable via CONFIG_STACKTRACE
160 smaps An extension based on maps, showing the memory consumption of
161 each mapping and flags associated with it
162 smaps_rollup Accumulated smaps stats for all mappings of the process. This
163 can be derived from smaps, but is faster and more convenient
164 numa_maps An extension based on maps, showing the memory locality and
165 binding policy as well as mem usage (in pages) of each mapping.
166 ============= ===============================================================
167
168For example, to get the status information of a process, all you have to do is
169read the file /proc/PID/status::
170
171 >cat /proc/self/status
172 Name: cat
173 State: R (running)
174 Tgid: 5452
175 Pid: 5452
176 PPid: 743
177 TracerPid: 0 (2.4)
178 Uid: 501 501 501 501
179 Gid: 100 100 100 100
180 FDSize: 256
181 Groups: 100 14 16
182 Kthread: 0
183 VmPeak: 5004 kB
184 VmSize: 5004 kB
185 VmLck: 0 kB
186 VmHWM: 476 kB
187 VmRSS: 476 kB
188 RssAnon: 352 kB
189 RssFile: 120 kB
190 RssShmem: 4 kB
191 VmData: 156 kB
192 VmStk: 88 kB
193 VmExe: 68 kB
194 VmLib: 1412 kB
195 VmPTE: 20 kb
196 VmSwap: 0 kB
197 HugetlbPages: 0 kB
198 CoreDumping: 0
199 THP_enabled: 1
200 Threads: 1
201 SigQ: 0/28578
202 SigPnd: 0000000000000000
203 ShdPnd: 0000000000000000
204 SigBlk: 0000000000000000
205 SigIgn: 0000000000000000
206 SigCgt: 0000000000000000
207 CapInh: 00000000fffffeff
208 CapPrm: 0000000000000000
209 CapEff: 0000000000000000
210 CapBnd: ffffffffffffffff
211 CapAmb: 0000000000000000
212 NoNewPrivs: 0
213 Seccomp: 0
214 Speculation_Store_Bypass: thread vulnerable
215 SpeculationIndirectBranch: conditional enabled
216 voluntary_ctxt_switches: 0
217 nonvoluntary_ctxt_switches: 1
218
219This shows you nearly the same information you would get if you viewed it with
220the ps command. In fact, ps uses the proc file system to obtain its
221information. But you get a more detailed view of the process by reading the
222file /proc/PID/status. It fields are described in table 1-2.
223
224The statm file contains more detailed information about the process
225memory usage. Its seven fields are explained in Table 1-3. The stat file
226contains detailed information about the process itself. Its fields are
227explained in Table 1-4.
228
229(for SMP CONFIG users)
230
231For making accounting scalable, RSS related information are handled in an
232asynchronous manner and the value may not be very precise. To see a precise
233snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
234It's slow but very precise.
235
236.. table:: Table 1-2: Contents of the status fields (as of 4.19)
237
238 ========================== ===================================================
239 Field Content
240 ========================== ===================================================
241 Name filename of the executable
242 Umask file mode creation mask
243 State state (R is running, S is sleeping, D is sleeping
244 in an uninterruptible wait, Z is zombie,
245 T is traced or stopped)
246 Tgid thread group ID
247 Ngid NUMA group ID (0 if none)
248 Pid process id
249 PPid process id of the parent process
250 TracerPid PID of process tracing this process (0 if not, or
251 the tracer is outside of the current pid namespace)
252 Uid Real, effective, saved set, and file system UIDs
253 Gid Real, effective, saved set, and file system GIDs
254 FDSize number of file descriptor slots currently allocated
255 Groups supplementary group list
256 NStgid descendant namespace thread group ID hierarchy
257 NSpid descendant namespace process ID hierarchy
258 NSpgid descendant namespace process group ID hierarchy
259 NSsid descendant namespace session ID hierarchy
260 Kthread kernel thread flag, 1 is yes, 0 is no
261 VmPeak peak virtual memory size
262 VmSize total program size
263 VmLck locked memory size
264 VmPin pinned memory size
265 VmHWM peak resident set size ("high water mark")
266 VmRSS size of memory portions. It contains the three
267 following parts
268 (VmRSS = RssAnon + RssFile + RssShmem)
269 RssAnon size of resident anonymous memory
270 RssFile size of resident file mappings
271 RssShmem size of resident shmem memory (includes SysV shm,
272 mapping of tmpfs and shared anonymous mappings)
273 VmData size of private data segments
274 VmStk size of stack segments
275 VmExe size of text segment
276 VmLib size of shared library code
277 VmPTE size of page table entries
278 VmSwap amount of swap used by anonymous private data
279 (shmem swap usage is not included)
280 HugetlbPages size of hugetlb memory portions
281 CoreDumping process's memory is currently being dumped
282 (killing the process may lead to a corrupted core)
283 THP_enabled process is allowed to use THP (returns 0 when
284 PR_SET_THP_DISABLE is set on the process
285 Threads number of threads
286 SigQ number of signals queued/max. number for queue
287 SigPnd bitmap of pending signals for the thread
288 ShdPnd bitmap of shared pending signals for the process
289 SigBlk bitmap of blocked signals
290 SigIgn bitmap of ignored signals
291 SigCgt bitmap of caught signals
292 CapInh bitmap of inheritable capabilities
293 CapPrm bitmap of permitted capabilities
294 CapEff bitmap of effective capabilities
295 CapBnd bitmap of capabilities bounding set
296 CapAmb bitmap of ambient capabilities
297 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
298 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
299 Speculation_Store_Bypass speculative store bypass mitigation status
300 SpeculationIndirectBranch indirect branch speculation mode
301 Cpus_allowed mask of CPUs on which this process may run
302 Cpus_allowed_list Same as previous, but in "list format"
303 Mems_allowed mask of memory nodes allowed to this process
304 Mems_allowed_list Same as previous, but in "list format"
305 voluntary_ctxt_switches number of voluntary context switches
306 nonvoluntary_ctxt_switches number of non voluntary context switches
307 ========================== ===================================================
308
309
310.. table:: Table 1-3: Contents of the statm fields (as of 2.6.8-rc3)
311
312 ======== =============================== ==============================
313 Field Content
314 ======== =============================== ==============================
315 size total program size (pages) (same as VmSize in status)
316 resident size of memory portions (pages) (same as VmRSS in status)
317 shared number of pages that are shared (i.e. backed by a file, same
318 as RssFile+RssShmem in status)
319 trs number of pages that are 'code' (not including libs; broken,
320 includes data segment)
321 lrs number of pages of library (always 0 on 2.6)
322 drs number of pages of data/stack (including libs; broken,
323 includes library text)
324 dt number of dirty pages (always 0 on 2.6)
325 ======== =============================== ==============================
326
327
328.. table:: Table 1-4: Contents of the stat fields (as of 2.6.30-rc7)
329
330 ============= ===============================================================
331 Field Content
332 ============= ===============================================================
333 pid process id
334 tcomm filename of the executable
335 state state (R is running, S is sleeping, D is sleeping in an
336 uninterruptible wait, Z is zombie, T is traced or stopped)
337 ppid process id of the parent process
338 pgrp pgrp of the process
339 sid session id
340 tty_nr tty the process uses
341 tty_pgrp pgrp of the tty
342 flags task flags
343 min_flt number of minor faults
344 cmin_flt number of minor faults with child's
345 maj_flt number of major faults
346 cmaj_flt number of major faults with child's
347 utime user mode jiffies
348 stime kernel mode jiffies
349 cutime user mode jiffies with child's
350 cstime kernel mode jiffies with child's
351 priority priority level
352 nice nice level
353 num_threads number of threads
354 it_real_value (obsolete, always 0)
355 start_time time the process started after system boot
356 vsize virtual memory size
357 rss resident set memory size
358 rsslim current limit in bytes on the rss
359 start_code address above which program text can run
360 end_code address below which program text can run
361 start_stack address of the start of the main process stack
362 esp current value of ESP
363 eip current value of EIP
364 pending bitmap of pending signals
365 blocked bitmap of blocked signals
366 sigign bitmap of ignored signals
367 sigcatch bitmap of caught signals
368 0 (place holder, used to be the wchan address,
369 use /proc/PID/wchan instead)
370 0 (place holder)
371 0 (place holder)
372 exit_signal signal to send to parent thread on exit
373 task_cpu which CPU the task is scheduled on
374 rt_priority realtime priority
375 policy scheduling policy (man sched_setscheduler)
376 blkio_ticks time spent waiting for block IO
377 gtime guest time of the task in jiffies
378 cgtime guest time of the task children in jiffies
379 start_data address above which program data+bss is placed
380 end_data address below which program data+bss is placed
381 start_brk address above which program heap can be expanded with brk()
382 arg_start address above which program command line is placed
383 arg_end address below which program command line is placed
384 env_start address above which program environment is placed
385 env_end address below which program environment is placed
386 exit_code the thread's exit_code in the form reported by the waitpid
387 system call
388 ============= ===============================================================
389
390The /proc/PID/maps file contains the currently mapped memory regions and
391their access permissions.
392
393The format is::
394
395 address perms offset dev inode pathname
396
397 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test
398 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
399 0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
400 a7cb1000-a7cb2000 ---p 00000000 00:00 0
401 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
402 a7eb2000-a7eb3000 ---p 00000000 00:00 0
403 a7eb3000-a7ed5000 rw-p 00000000 00:00 0
404 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
405 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
406 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
407 a800b000-a800e000 rw-p 00000000 00:00 0
408 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
409 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
410 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
411 a8024000-a8027000 rw-p 00000000 00:00 0
412 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
413 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
414 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
415 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
416 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
417
418where "address" is the address space in the process that it occupies, "perms"
419is a set of permissions::
420
421 r = read
422 w = write
423 x = execute
424 s = shared
425 p = private (copy on write)
426
427"offset" is the offset into the mapping, "dev" is the device (major:minor), and
428"inode" is the inode on that device. 0 indicates that no inode is associated
429with the memory region, as the case would be with BSS (uninitialized data).
430The "pathname" shows the name associated file for this mapping. If the mapping
431is not associated with a file:
432
433 =================== ===========================================
434 [heap] the heap of the program
435 [stack] the stack of the main process
436 [vdso] the "virtual dynamic shared object",
437 the kernel system call handler
438 [anon:<name>] a private anonymous mapping that has been
439 named by userspace
440 [anon_shmem:<name>] an anonymous shared memory mapping that has
441 been named by userspace
442 =================== ===========================================
443
444 or if empty, the mapping is anonymous.
445
446The /proc/PID/smaps is an extension based on maps, showing the memory
447consumption for each of the process's mappings. For each mapping (aka Virtual
448Memory Area, or VMA) there is a series of lines such as the following::
449
450 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
451
452 Size: 1084 kB
453 KernelPageSize: 4 kB
454 MMUPageSize: 4 kB
455 Rss: 892 kB
456 Pss: 374 kB
457 Pss_Dirty: 0 kB
458 Shared_Clean: 892 kB
459 Shared_Dirty: 0 kB
460 Private_Clean: 0 kB
461 Private_Dirty: 0 kB
462 Referenced: 892 kB
463 Anonymous: 0 kB
464 KSM: 0 kB
465 LazyFree: 0 kB
466 AnonHugePages: 0 kB
467 ShmemPmdMapped: 0 kB
468 Shared_Hugetlb: 0 kB
469 Private_Hugetlb: 0 kB
470 Swap: 0 kB
471 SwapPss: 0 kB
472 KernelPageSize: 4 kB
473 MMUPageSize: 4 kB
474 Locked: 0 kB
475 THPeligible: 0
476 VmFlags: rd ex mr mw me dw
477
478The first of these lines shows the same information as is displayed for the
479mapping in /proc/PID/maps. Following lines show the size of the mapping
480(size); the size of each page allocated when backing a VMA (KernelPageSize),
481which is usually the same as the size in the page table entries; the page size
482used by the MMU when backing a VMA (in most cases, the same as KernelPageSize);
483the amount of the mapping that is currently resident in RAM (RSS); the
484process' proportional share of this mapping (PSS); and the number of clean and
485dirty shared and private pages in the mapping.
486
487The "proportional set size" (PSS) of a process is the count of pages it has
488in memory, where each page is divided by the number of processes sharing it.
489So if a process has 1000 pages all to itself, and 1000 shared with one other
490process, its PSS will be 1500. "Pss_Dirty" is the portion of PSS which
491consists of dirty pages. ("Pss_Clean" is not included, but it can be
492calculated by subtracting "Pss_Dirty" from "Pss".)
493
494Note that even a page which is part of a MAP_SHARED mapping, but has only
495a single pte mapped, i.e. is currently used by only one process, is accounted
496as private and not as shared.
497
498"Referenced" indicates the amount of memory currently marked as referenced or
499accessed.
500
501"Anonymous" shows the amount of memory that does not belong to any file. Even
502a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
503and a page is modified, the file page is replaced by a private anonymous copy.
504
505"KSM" reports how many of the pages are KSM pages. Note that KSM-placed zeropages
506are not included, only actual KSM pages.
507
508"LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE).
509The memory isn't freed immediately with madvise(). It's freed in memory
510pressure if the memory is clean. Please note that the printed value might
511be lower than the real value due to optimizations used in the current
512implementation. If this is not desirable please file a bug report.
513
514"AnonHugePages" shows the amount of memory backed by transparent hugepage.
515
516"ShmemPmdMapped" shows the amount of shared (shmem/tmpfs) memory backed by
517huge pages.
518
519"Shared_Hugetlb" and "Private_Hugetlb" show the amounts of memory backed by
520hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
521reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
522
523"Swap" shows how much would-be-anonymous memory is also used, but out on swap.
524
525For shmem mappings, "Swap" includes also the size of the mapped (and not
526replaced by copy-on-write) part of the underlying shmem object out on swap.
527"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
528does not take into account swapped out page of underlying shmem objects.
529"Locked" indicates whether the mapping is locked in memory or not.
530
531"THPeligible" indicates whether the mapping is eligible for allocating
532naturally aligned THP pages of any currently enabled size. 1 if true, 0
533otherwise.
534
535"VmFlags" field deserves a separate description. This member represents the
536kernel flags associated with the particular virtual memory area in two letter
537encoded manner. The codes are the following:
538
539 == =======================================
540 rd readable
541 wr writeable
542 ex executable
543 sh shared
544 mr may read
545 mw may write
546 me may execute
547 ms may share
548 gd stack segment growns down
549 pf pure PFN range
550 dw disabled write to the mapped file
551 lo pages are locked in memory
552 io memory mapped I/O area
553 sr sequential read advise provided
554 rr random read advise provided
555 dc do not copy area on fork
556 de do not expand area on remapping
557 ac area is accountable
558 nr swap space is not reserved for the area
559 ht area uses huge tlb pages
560 sf synchronous page fault
561 ar architecture specific flag
562 wf wipe on fork
563 dd do not include area into core dump
564 sd soft dirty flag
565 mm mixed map area
566 hg huge page advise flag
567 nh no huge page advise flag
568 mg mergeable advise flag
569 bt arm64 BTI guarded page
570 mt arm64 MTE allocation tags are enabled
571 um userfaultfd missing tracking
572 uw userfaultfd wr-protect tracking
573 ss shadow stack page
574 == =======================================
575
576Note that there is no guarantee that every flag and associated mnemonic will
577be present in all further kernel releases. Things get changed, the flags may
578be vanished or the reverse -- new added. Interpretation of their meaning
579might change in future as well. So each consumer of these flags has to
580follow each specific kernel version for the exact semantic.
581
582This file is only present if the CONFIG_MMU kernel configuration option is
583enabled.
584
585Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent
586output can be achieved only in the single read call).
587
588This typically manifests when doing partial reads of these files while the
589memory map is being modified. Despite the races, we do provide the following
590guarantees:
591
5921) The mapped addresses never go backwards, which implies no two
593 regions will ever overlap.
5942) If there is something at a given vaddr during the entirety of the
595 life of the smaps/maps walk, there will be some output for it.
596
597The /proc/PID/smaps_rollup file includes the same fields as /proc/PID/smaps,
598but their values are the sums of the corresponding values for all mappings of
599the process. Additionally, it contains these fields:
600
601- Pss_Anon
602- Pss_File
603- Pss_Shmem
604
605They represent the proportional shares of anonymous, file, and shmem pages, as
606described for smaps above. These fields are omitted in smaps since each
607mapping identifies the type (anon, file, or shmem) of all pages it contains.
608Thus all information in smaps_rollup can be derived from smaps, but at a
609significantly higher cost.
610
611The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
612bits on both physical and virtual pages associated with a process, and the
613soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst
614for details).
615To clear the bits for all the pages associated with the process::
616
617 > echo 1 > /proc/PID/clear_refs
618
619To clear the bits for the anonymous pages associated with the process::
620
621 > echo 2 > /proc/PID/clear_refs
622
623To clear the bits for the file mapped pages associated with the process::
624
625 > echo 3 > /proc/PID/clear_refs
626
627To clear the soft-dirty bit::
628
629 > echo 4 > /proc/PID/clear_refs
630
631To reset the peak resident set size ("high water mark") to the process's
632current value::
633
634 > echo 5 > /proc/PID/clear_refs
635
636Any other value written to /proc/PID/clear_refs will have no effect.
637
638The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
639using /proc/kpageflags and number of times a page is mapped using
640/proc/kpagecount. For detailed explanation, see
641Documentation/admin-guide/mm/pagemap.rst.
642
643The /proc/pid/numa_maps is an extension based on maps, showing the memory
644locality and binding policy, as well as the memory usage (in pages) of
645each mapping. The output follows a general format where mapping details get
646summarized separated by blank spaces, one mapping per each file line::
647
648 address policy mapping details
649
650 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
651 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
652 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
653 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
654 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
655 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
656 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
657 320698b000 default file=/lib64/libc-2.12.so
658 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
659 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
660 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
661 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
662 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
663 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
664 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
665 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
666
667Where:
668
669"address" is the starting address for the mapping;
670
671"policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst);
672
673"mapping details" summarizes mapping data such as mapping type, page usage counters,
674node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
675size, in KB, that is backing the mapping up.
676
6771.2 Kernel data
678---------------
679
680Similar to the process entries, the kernel data files give information about
681the running kernel. The files used to obtain this information are contained in
682/proc and are listed in Table 1-5. Not all of these will be present in your
683system. It depends on the kernel configuration and the loaded modules, which
684files are there, and which are missing.
685
686.. table:: Table 1-5: Kernel info in /proc
687
688 ============ ===============================================================
689 File Content
690 ============ ===============================================================
691 apm Advanced power management info
692 bootconfig Kernel command line obtained from boot config,
693 and, if there were kernel parameters from the
694 boot loader, a "# Parameters from bootloader:"
695 line followed by a line containing those
696 parameters prefixed by "# ". (5.5)
697 buddyinfo Kernel memory allocator information (see text) (2.5)
698 bus Directory containing bus specific information
699 cmdline Kernel command line, both from bootloader and embedded
700 in the kernel image
701 cpuinfo Info about the CPU
702 devices Available devices (block and character)
703 dma Used DMS channels
704 filesystems Supported filesystems
705 driver Various drivers grouped here, currently rtc (2.4)
706 execdomains Execdomains, related to security (2.4)
707 fb Frame Buffer devices (2.4)
708 fs File system parameters, currently nfs/exports (2.4)
709 ide Directory containing info about the IDE subsystem
710 interrupts Interrupt usage
711 iomem Memory map (2.4)
712 ioports I/O port usage
713 irq Masks for irq to cpu affinity (2.4)(smp?)
714 isapnp ISA PnP (Plug&Play) Info (2.4)
715 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
716 kmsg Kernel messages
717 ksyms Kernel symbol table
718 loadavg Load average of last 1, 5 & 15 minutes;
719 number of processes currently runnable (running or on ready queue);
720 total number of processes in system;
721 last pid created.
722 All fields are separated by one space except "number of
723 processes currently runnable" and "total number of processes
724 in system", which are separated by a slash ('/'). Example:
725 0.61 0.61 0.55 3/828 22084
726 locks Kernel locks
727 meminfo Memory info
728 misc Miscellaneous
729 modules List of loaded modules
730 mounts Mounted filesystems
731 net Networking info (see text)
732 pagetypeinfo Additional page allocator information (see text) (2.5)
733 partitions Table of partitions known to the system
734 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
735 decoupled by lspci (2.4)
736 rtc Real time clock
737 scsi SCSI info (see text)
738 slabinfo Slab pool info
739 softirqs softirq usage
740 stat Overall statistics
741 swaps Swap space utilization
742 sys See chapter 2
743 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
744 tty Info of tty drivers
745 uptime Wall clock since boot, combined idle time of all cpus
746 version Kernel version
747 video bttv info of video resources (2.4)
748 vmallocinfo Show vmalloced areas
749 ============ ===============================================================
750
751You can, for example, check which interrupts are currently in use and what
752they are used for by looking in the file /proc/interrupts::
753
754 > cat /proc/interrupts
755 CPU0
756 0: 8728810 XT-PIC timer
757 1: 895 XT-PIC keyboard
758 2: 0 XT-PIC cascade
759 3: 531695 XT-PIC aha152x
760 4: 2014133 XT-PIC serial
761 5: 44401 XT-PIC pcnet_cs
762 8: 2 XT-PIC rtc
763 11: 8 XT-PIC i82365
764 12: 182918 XT-PIC PS/2 Mouse
765 13: 1 XT-PIC fpu
766 14: 1232265 XT-PIC ide0
767 15: 7 XT-PIC ide1
768 NMI: 0
769
770In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
771output of a SMP machine)::
772
773 > cat /proc/interrupts
774
775 CPU0 CPU1
776 0: 1243498 1214548 IO-APIC-edge timer
777 1: 8949 8958 IO-APIC-edge keyboard
778 2: 0 0 XT-PIC cascade
779 5: 11286 10161 IO-APIC-edge soundblaster
780 8: 1 0 IO-APIC-edge rtc
781 9: 27422 27407 IO-APIC-edge 3c503
782 12: 113645 113873 IO-APIC-edge PS/2 Mouse
783 13: 0 0 XT-PIC fpu
784 14: 22491 24012 IO-APIC-edge ide0
785 15: 2183 2415 IO-APIC-edge ide1
786 17: 30564 30414 IO-APIC-level eth0
787 18: 177 164 IO-APIC-level bttv
788 NMI: 2457961 2457959
789 LOC: 2457882 2457881
790 ERR: 2155
791
792NMI is incremented in this case because every timer interrupt generates a NMI
793(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
794
795LOC is the local interrupt counter of the internal APIC of every CPU.
796
797ERR is incremented in the case of errors in the IO-APIC bus (the bus that
798connects the CPUs in a SMP system. This means that an error has been detected,
799the IO-APIC automatically retry the transmission, so it should not be a big
800problem, but you should read the SMP-FAQ.
801
802In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
803/proc/interrupts to display every IRQ vector in use by the system, not
804just those considered 'most important'. The new vectors are:
805
806THR
807 interrupt raised when a machine check threshold counter
808 (typically counting ECC corrected errors of memory or cache) exceeds
809 a configurable threshold. Only available on some systems.
810
811TRM
812 a thermal event interrupt occurs when a temperature threshold
813 has been exceeded for the CPU. This interrupt may also be generated
814 when the temperature drops back to normal.
815
816SPU
817 a spurious interrupt is some interrupt that was raised then lowered
818 by some IO device before it could be fully processed by the APIC. Hence
819 the APIC sees the interrupt but does not know what device it came from.
820 For this case the APIC will generate the interrupt with a IRQ vector
821 of 0xff. This might also be generated by chipset bugs.
822
823RES, CAL, TLB
824 rescheduling, call and TLB flush interrupts are
825 sent from one CPU to another per the needs of the OS. Typically,
826 their statistics are used by kernel developers and interested users to
827 determine the occurrence of interrupts of the given type.
828
829The above IRQ vectors are displayed only when relevant. For example,
830the threshold vector does not exist on x86_64 platforms. Others are
831suppressed when the system is a uniprocessor. As of this writing, only
832i386 and x86_64 platforms support the new IRQ vector displays.
833
834Of some interest is the introduction of the /proc/irq directory to 2.4.
835It could be used to set IRQ to CPU affinity. This means that you can "hook" an
836IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
837irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
838prof_cpu_mask.
839
840For example::
841
842 > ls /proc/irq/
843 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
844 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
845 > ls /proc/irq/0/
846 smp_affinity
847
848smp_affinity is a bitmask, in which you can specify which CPUs can handle the
849IRQ. You can set it by doing::
850
851 > echo 1 > /proc/irq/10/smp_affinity
852
853This means that only the first CPU will handle the IRQ, but you can also echo
8545 which means that only the first and third CPU can handle the IRQ.
855
856The contents of each smp_affinity file is the same by default::
857
858 > cat /proc/irq/0/smp_affinity
859 ffffffff
860
861There is an alternate interface, smp_affinity_list which allows specifying
862a CPU range instead of a bitmask::
863
864 > cat /proc/irq/0/smp_affinity_list
865 1024-1031
866
867The default_smp_affinity mask applies to all non-active IRQs, which are the
868IRQs which have not yet been allocated/activated, and hence which lack a
869/proc/irq/[0-9]* directory.
870
871The node file on an SMP system shows the node to which the device using the IRQ
872reports itself as being attached. This hardware locality information does not
873include information about any possible driver locality preference.
874
875prof_cpu_mask specifies which CPUs are to be profiled by the system wide
876profiler. Default value is ffffffff (all CPUs if there are only 32 of them).
877
878The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
879between all the CPUs which are allowed to handle it. As usual the kernel has
880more info than you and does a better job than you, so the defaults are the
881best choice for almost everyone. [Note this applies only to those IO-APIC's
882that support "Round Robin" interrupt distribution.]
883
884There are three more important subdirectories in /proc: net, scsi, and sys.
885The general rule is that the contents, or even the existence of these
886directories, depend on your kernel configuration. If SCSI is not enabled, the
887directory scsi may not exist. The same is true with the net, which is there
888only when networking support is present in the running kernel.
889
890The slabinfo file gives information about memory usage at the slab level.
891Linux uses slab pools for memory management above page level in version 2.2.
892Commonly used objects have their own slab pool (such as network buffers,
893directory cache, and so on).
894
895::
896
897 > cat /proc/buddyinfo
898
899 Node 0, zone DMA 0 4 5 4 4 3 ...
900 Node 0, zone Normal 1 0 0 1 101 8 ...
901 Node 0, zone HighMem 2 0 0 1 1 0 ...
902
903External fragmentation is a problem under some workloads, and buddyinfo is a
904useful tool for helping diagnose these problems. Buddyinfo will give you a
905clue as to how big an area you can safely allocate, or why a previous
906allocation failed.
907
908Each column represents the number of pages of a certain order which are
909available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
910ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
911available in ZONE_NORMAL, etc...
912
913More information relevant to external fragmentation can be found in
914pagetypeinfo::
915
916 > cat /proc/pagetypeinfo
917 Page block order: 9
918 Pages per block: 512
919
920 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
921 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
922 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
923 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
924 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
925 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
926 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
927 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
928 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
929 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
930 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
931
932 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
933 Node 0, zone DMA 2 0 5 1 0
934 Node 0, zone DMA32 41 6 967 2 0
935
936Fragmentation avoidance in the kernel works by grouping pages of different
937migrate types into the same contiguous regions of memory called page blocks.
938A page block is typically the size of the default hugepage size, e.g. 2MB on
939X86-64. By keeping pages grouped based on their ability to move, the kernel
940can reclaim pages within a page block to satisfy a high-order allocation.
941
942The pagetypinfo begins with information on the size of a page block. It
943then gives the same type of information as buddyinfo except broken down
944by migrate-type and finishes with details on how many page blocks of each
945type exist.
946
947If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
948from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
949make an estimate of the likely number of huge pages that can be allocated
950at a given point in time. All the "Movable" blocks should be allocatable
951unless memory has been mlock()'d. Some of the Reclaimable blocks should
952also be allocatable although a lot of filesystem metadata may have to be
953reclaimed to achieve this.
954
955
956meminfo
957~~~~~~~
958
959Provides information about distribution and utilization of memory. This
960varies by architecture and compile options. Some of the counters reported
961here overlap. The memory reported by the non overlapping counters may not
962add up to the overall memory usage and the difference for some workloads
963can be substantial. In many cases there are other means to find out
964additional memory using subsystem specific interfaces, for instance
965/proc/net/sockstat for TCP memory allocations.
966
967Example output. You may not have all of these fields.
968
969::
970
971 > cat /proc/meminfo
972
973 MemTotal: 32858820 kB
974 MemFree: 21001236 kB
975 MemAvailable: 27214312 kB
976 Buffers: 581092 kB
977 Cached: 5587612 kB
978 SwapCached: 0 kB
979 Active: 3237152 kB
980 Inactive: 7586256 kB
981 Active(anon): 94064 kB
982 Inactive(anon): 4570616 kB
983 Active(file): 3143088 kB
984 Inactive(file): 3015640 kB
985 Unevictable: 0 kB
986 Mlocked: 0 kB
987 SwapTotal: 0 kB
988 SwapFree: 0 kB
989 Zswap: 1904 kB
990 Zswapped: 7792 kB
991 Dirty: 12 kB
992 Writeback: 0 kB
993 AnonPages: 4654780 kB
994 Mapped: 266244 kB
995 Shmem: 9976 kB
996 KReclaimable: 517708 kB
997 Slab: 660044 kB
998 SReclaimable: 517708 kB
999 SUnreclaim: 142336 kB
1000 KernelStack: 11168 kB
1001 PageTables: 20540 kB
1002 SecPageTables: 0 kB
1003 NFS_Unstable: 0 kB
1004 Bounce: 0 kB
1005 WritebackTmp: 0 kB
1006 CommitLimit: 16429408 kB
1007 Committed_AS: 7715148 kB
1008 VmallocTotal: 34359738367 kB
1009 VmallocUsed: 40444 kB
1010 VmallocChunk: 0 kB
1011 Percpu: 29312 kB
1012 EarlyMemtestBad: 0 kB
1013 HardwareCorrupted: 0 kB
1014 AnonHugePages: 4149248 kB
1015 ShmemHugePages: 0 kB
1016 ShmemPmdMapped: 0 kB
1017 FileHugePages: 0 kB
1018 FilePmdMapped: 0 kB
1019 CmaTotal: 0 kB
1020 CmaFree: 0 kB
1021 HugePages_Total: 0
1022 HugePages_Free: 0
1023 HugePages_Rsvd: 0
1024 HugePages_Surp: 0
1025 Hugepagesize: 2048 kB
1026 Hugetlb: 0 kB
1027 DirectMap4k: 401152 kB
1028 DirectMap2M: 10008576 kB
1029 DirectMap1G: 24117248 kB
1030
1031MemTotal
1032 Total usable RAM (i.e. physical RAM minus a few reserved
1033 bits and the kernel binary code)
1034MemFree
1035 Total free RAM. On highmem systems, the sum of LowFree+HighFree
1036MemAvailable
1037 An estimate of how much memory is available for starting new
1038 applications, without swapping. Calculated from MemFree,
1039 SReclaimable, the size of the file LRU lists, and the low
1040 watermarks in each zone.
1041 The estimate takes into account that the system needs some
1042 page cache to function well, and that not all reclaimable
1043 slab will be reclaimable, due to items being in use. The
1044 impact of those factors will vary from system to system.
1045Buffers
1046 Relatively temporary storage for raw disk blocks
1047 shouldn't get tremendously large (20MB or so)
1048Cached
1049 In-memory cache for files read from the disk (the
1050 pagecache) as well as tmpfs & shmem.
1051 Doesn't include SwapCached.
1052SwapCached
1053 Memory that once was swapped out, is swapped back in but
1054 still also is in the swapfile (if memory is needed it
1055 doesn't need to be swapped out AGAIN because it is already
1056 in the swapfile. This saves I/O)
1057Active
1058 Memory that has been used more recently and usually not
1059 reclaimed unless absolutely necessary.
1060Inactive
1061 Memory which has been less recently used. It is more
1062 eligible to be reclaimed for other purposes
1063Unevictable
1064 Memory allocated for userspace which cannot be reclaimed, such
1065 as mlocked pages, ramfs backing pages, secret memfd pages etc.
1066Mlocked
1067 Memory locked with mlock().
1068HighTotal, HighFree
1069 Highmem is all memory above ~860MB of physical memory.
1070 Highmem areas are for use by userspace programs, or
1071 for the pagecache. The kernel must use tricks to access
1072 this memory, making it slower to access than lowmem.
1073LowTotal, LowFree
1074 Lowmem is memory which can be used for everything that
1075 highmem can be used for, but it is also available for the
1076 kernel's use for its own data structures. Among many
1077 other things, it is where everything from the Slab is
1078 allocated. Bad things happen when you're out of lowmem.
1079SwapTotal
1080 total amount of swap space available
1081SwapFree
1082 Memory which has been evicted from RAM, and is temporarily
1083 on the disk
1084Zswap
1085 Memory consumed by the zswap backend (compressed size)
1086Zswapped
1087 Amount of anonymous memory stored in zswap (original size)
1088Dirty
1089 Memory which is waiting to get written back to the disk
1090Writeback
1091 Memory which is actively being written back to the disk
1092AnonPages
1093 Non-file backed pages mapped into userspace page tables
1094Mapped
1095 files which have been mmapped, such as libraries
1096Shmem
1097 Total memory used by shared memory (shmem) and tmpfs
1098KReclaimable
1099 Kernel allocations that the kernel will attempt to reclaim
1100 under memory pressure. Includes SReclaimable (below), and other
1101 direct allocations with a shrinker.
1102Slab
1103 in-kernel data structures cache
1104SReclaimable
1105 Part of Slab, that might be reclaimed, such as caches
1106SUnreclaim
1107 Part of Slab, that cannot be reclaimed on memory pressure
1108KernelStack
1109 Memory consumed by the kernel stacks of all tasks
1110PageTables
1111 Memory consumed by userspace page tables
1112SecPageTables
1113 Memory consumed by secondary page tables, this currently
1114 currently includes KVM mmu allocations on x86 and arm64.
1115NFS_Unstable
1116 Always zero. Previous counted pages which had been written to
1117 the server, but has not been committed to stable storage.
1118Bounce
1119 Memory used for block device "bounce buffers"
1120WritebackTmp
1121 Memory used by FUSE for temporary writeback buffers
1122CommitLimit
1123 Based on the overcommit ratio ('vm.overcommit_ratio'),
1124 this is the total amount of memory currently available to
1125 be allocated on the system. This limit is only adhered to
1126 if strict overcommit accounting is enabled (mode 2 in
1127 'vm.overcommit_memory').
1128
1129 The CommitLimit is calculated with the following formula::
1130
1131 CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
1132 overcommit_ratio / 100 + [total swap pages]
1133
1134 For example, on a system with 1G of physical RAM and 7G
1135 of swap with a `vm.overcommit_ratio` of 30 it would
1136 yield a CommitLimit of 7.3G.
1137
1138 For more details, see the memory overcommit documentation
1139 in mm/overcommit-accounting.
1140Committed_AS
1141 The amount of memory presently allocated on the system.
1142 The committed memory is a sum of all of the memory which
1143 has been allocated by processes, even if it has not been
1144 "used" by them as of yet. A process which malloc()'s 1G
1145 of memory, but only touches 300M of it will show up as
1146 using 1G. This 1G is memory which has been "committed" to
1147 by the VM and can be used at any time by the allocating
1148 application. With strict overcommit enabled on the system
1149 (mode 2 in 'vm.overcommit_memory'), allocations which would
1150 exceed the CommitLimit (detailed above) will not be permitted.
1151 This is useful if one needs to guarantee that processes will
1152 not fail due to lack of memory once that memory has been
1153 successfully allocated.
1154VmallocTotal
1155 total size of vmalloc virtual address space
1156VmallocUsed
1157 amount of vmalloc area which is used
1158VmallocChunk
1159 largest contiguous block of vmalloc area which is free
1160Percpu
1161 Memory allocated to the percpu allocator used to back percpu
1162 allocations. This stat excludes the cost of metadata.
1163EarlyMemtestBad
1164 The amount of RAM/memory in kB, that was identified as corrupted
1165 by early memtest. If memtest was not run, this field will not
1166 be displayed at all. Size is never rounded down to 0 kB.
1167 That means if 0 kB is reported, you can safely assume
1168 there was at least one pass of memtest and none of the passes
1169 found a single faulty byte of RAM.
1170HardwareCorrupted
1171 The amount of RAM/memory in KB, the kernel identifies as
1172 corrupted.
1173AnonHugePages
1174 Non-file backed huge pages mapped into userspace page tables
1175ShmemHugePages
1176 Memory used by shared memory (shmem) and tmpfs allocated
1177 with huge pages
1178ShmemPmdMapped
1179 Shared memory mapped into userspace with huge pages
1180FileHugePages
1181 Memory used for filesystem data (page cache) allocated
1182 with huge pages
1183FilePmdMapped
1184 Page cache mapped into userspace with huge pages
1185CmaTotal
1186 Memory reserved for the Contiguous Memory Allocator (CMA)
1187CmaFree
1188 Free remaining memory in the CMA reserves
1189HugePages_Total, HugePages_Free, HugePages_Rsvd, HugePages_Surp, Hugepagesize, Hugetlb
1190 See Documentation/admin-guide/mm/hugetlbpage.rst.
1191DirectMap4k, DirectMap2M, DirectMap1G
1192 Breakdown of page table sizes used in the kernel's
1193 identity mapping of RAM
1194
1195vmallocinfo
1196~~~~~~~~~~~
1197
1198Provides information about vmalloced/vmaped areas. One line per area,
1199containing the virtual address range of the area, size in bytes,
1200caller information of the creator, and optional information depending
1201on the kind of area:
1202
1203 ========== ===================================================
1204 pages=nr number of pages
1205 phys=addr if a physical address was specified
1206 ioremap I/O mapping (ioremap() and friends)
1207 vmalloc vmalloc() area
1208 vmap vmap()ed pages
1209 user VM_USERMAP area
1210 vpages buffer for pages pointers was vmalloced (huge area)
1211 N<node>=nr (Only on NUMA kernels)
1212 Number of pages allocated on memory node <node>
1213 ========== ===================================================
1214
1215::
1216
1217 > cat /proc/vmallocinfo
1218 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
1219 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
1220 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
1221 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
1222 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
1223 phys=7fee8000 ioremap
1224 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
1225 phys=7fee7000 ioremap
1226 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
1227 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
1228 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
1229 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
1230 pages=2 vmalloc N1=2
1231 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
1232 /0x130 [x_tables] pages=4 vmalloc N0=4
1233 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
1234 pages=14 vmalloc N2=14
1235 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
1236 pages=4 vmalloc N1=4
1237 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
1238 pages=2 vmalloc N1=2
1239 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
1240 pages=10 vmalloc N0=10
1241
1242
1243softirqs
1244~~~~~~~~
1245
1246Provides counts of softirq handlers serviced since boot time, for each CPU.
1247
1248::
1249
1250 > cat /proc/softirqs
1251 CPU0 CPU1 CPU2 CPU3
1252 HI: 0 0 0 0
1253 TIMER: 27166 27120 27097 27034
1254 NET_TX: 0 0 0 17
1255 NET_RX: 42 0 0 39
1256 BLOCK: 0 0 107 1121
1257 TASKLET: 0 0 0 290
1258 SCHED: 27035 26983 26971 26746
1259 HRTIMER: 0 0 0 0
1260 RCU: 1678 1769 2178 2250
1261
12621.3 Networking info in /proc/net
1263--------------------------------
1264
1265The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
1266additional values you get for IP version 6 if you configure the kernel to
1267support this. Table 1-9 lists the files and their meaning.
1268
1269
1270.. table:: Table 1-8: IPv6 info in /proc/net
1271
1272 ========== =====================================================
1273 File Content
1274 ========== =====================================================
1275 udp6 UDP sockets (IPv6)
1276 tcp6 TCP sockets (IPv6)
1277 raw6 Raw device statistics (IPv6)
1278 igmp6 IP multicast addresses, which this host joined (IPv6)
1279 if_inet6 List of IPv6 interface addresses
1280 ipv6_route Kernel routing table for IPv6
1281 rt6_stats Global IPv6 routing tables statistics
1282 sockstat6 Socket statistics (IPv6)
1283 snmp6 Snmp data (IPv6)
1284 ========== =====================================================
1285
1286.. table:: Table 1-9: Network info in /proc/net
1287
1288 ============= ================================================================
1289 File Content
1290 ============= ================================================================
1291 arp Kernel ARP table
1292 dev network devices with statistics
1293 dev_mcast the Layer2 multicast groups a device is listening too
1294 (interface index, label, number of references, number of bound
1295 addresses).
1296 dev_stat network device status
1297 ip_fwchains Firewall chain linkage
1298 ip_fwnames Firewall chain names
1299 ip_masq Directory containing the masquerading tables
1300 ip_masquerade Major masquerading table
1301 netstat Network statistics
1302 raw raw device statistics
1303 route Kernel routing table
1304 rpc Directory containing rpc info
1305 rt_cache Routing cache
1306 snmp SNMP data
1307 sockstat Socket statistics
1308 softnet_stat Per-CPU incoming packets queues statistics of online CPUs
1309 tcp TCP sockets
1310 udp UDP sockets
1311 unix UNIX domain sockets
1312 wireless Wireless interface data (Wavelan etc)
1313 igmp IP multicast addresses, which this host joined
1314 psched Global packet scheduler parameters.
1315 netlink List of PF_NETLINK sockets
1316 ip_mr_vifs List of multicast virtual interfaces
1317 ip_mr_cache List of multicast routing cache
1318 ============= ================================================================
1319
1320You can use this information to see which network devices are available in
1321your system and how much traffic was routed over those devices::
1322
1323 > cat /proc/net/dev
1324 Inter-|Receive |[...
1325 face |bytes packets errs drop fifo frame compressed multicast|[...
1326 lo: 908188 5596 0 0 0 0 0 0 [...
1327 ppp0:15475140 20721 410 0 0 410 0 0 [...
1328 eth0: 614530 7085 0 0 0 0 0 1 [...
1329
1330 ...] Transmit
1331 ...] bytes packets errs drop fifo colls carrier compressed
1332 ...] 908188 5596 0 0 0 0 0 0
1333 ...] 1375103 17405 0 0 0 0 0 0
1334 ...] 1703981 5535 0 0 0 3 0 0
1335
1336In addition, each Channel Bond interface has its own directory. For
1337example, the bond0 device will have a directory called /proc/net/bond0/.
1338It will contain information that is specific to that bond, such as the
1339current slaves of the bond, the link status of the slaves, and how
1340many times the slaves link has failed.
1341
13421.4 SCSI info
1343-------------
1344
1345If you have a SCSI or ATA host adapter in your system, you'll find a
1346subdirectory named after the driver for this adapter in /proc/scsi.
1347You'll also see a list of all recognized SCSI devices in /proc/scsi::
1348
1349 >cat /proc/scsi/scsi
1350 Attached devices:
1351 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1352 Vendor: IBM Model: DGHS09U Rev: 03E0
1353 Type: Direct-Access ANSI SCSI revision: 03
1354 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1355 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1356 Type: CD-ROM ANSI SCSI revision: 02
1357
1358
1359The directory named after the driver has one file for each adapter found in
1360the system. These files contain information about the controller, including
1361the used IRQ and the IO address range. The amount of information shown is
1362dependent on the adapter you use. The example shows the output for an Adaptec
1363AHA-2940 SCSI adapter::
1364
1365 > cat /proc/scsi/aic7xxx/0
1366
1367 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1368 Compile Options:
1369 TCQ Enabled By Default : Disabled
1370 AIC7XXX_PROC_STATS : Disabled
1371 AIC7XXX_RESET_DELAY : 5
1372 Adapter Configuration:
1373 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1374 Ultra Wide Controller
1375 PCI MMAPed I/O Base: 0xeb001000
1376 Adapter SEEPROM Config: SEEPROM found and used.
1377 Adaptec SCSI BIOS: Enabled
1378 IRQ: 10
1379 SCBs: Active 0, Max Active 2,
1380 Allocated 15, HW 16, Page 255
1381 Interrupts: 160328
1382 BIOS Control Word: 0x18b6
1383 Adapter Control Word: 0x005b
1384 Extended Translation: Enabled
1385 Disconnect Enable Flags: 0xffff
1386 Ultra Enable Flags: 0x0001
1387 Tag Queue Enable Flags: 0x0000
1388 Ordered Queue Tag Flags: 0x0000
1389 Default Tag Queue Depth: 8
1390 Tagged Queue By Device array for aic7xxx host instance 0:
1391 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1392 Actual queue depth per device for aic7xxx host instance 0:
1393 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1394 Statistics:
1395 (scsi0:0:0:0)
1396 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1397 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1398 Total transfers 160151 (74577 reads and 85574 writes)
1399 (scsi0:0:6:0)
1400 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1401 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1402 Total transfers 0 (0 reads and 0 writes)
1403
1404
14051.5 Parallel port info in /proc/parport
1406---------------------------------------
1407
1408The directory /proc/parport contains information about the parallel ports of
1409your system. It has one subdirectory for each port, named after the port
1410number (0,1,2,...).
1411
1412These directories contain the four files shown in Table 1-10.
1413
1414
1415.. table:: Table 1-10: Files in /proc/parport
1416
1417 ========= ====================================================================
1418 File Content
1419 ========= ====================================================================
1420 autoprobe Any IEEE-1284 device ID information that has been acquired.
1421 devices list of the device drivers using that port. A + will appear by the
1422 name of the device currently using the port (it might not appear
1423 against any).
1424 hardware Parallel port's base address, IRQ line and DMA channel.
1425 irq IRQ that parport is using for that port. This is in a separate
1426 file to allow you to alter it by writing a new value in (IRQ
1427 number or none).
1428 ========= ====================================================================
1429
14301.6 TTY info in /proc/tty
1431-------------------------
1432
1433Information about the available and actually used tty's can be found in the
1434directory /proc/tty. You'll find entries for drivers and line disciplines in
1435this directory, as shown in Table 1-11.
1436
1437
1438.. table:: Table 1-11: Files in /proc/tty
1439
1440 ============= ==============================================
1441 File Content
1442 ============= ==============================================
1443 drivers list of drivers and their usage
1444 ldiscs registered line disciplines
1445 driver/serial usage statistic and status of single tty lines
1446 ============= ==============================================
1447
1448To see which tty's are currently in use, you can simply look into the file
1449/proc/tty/drivers::
1450
1451 > cat /proc/tty/drivers
1452 pty_slave /dev/pts 136 0-255 pty:slave
1453 pty_master /dev/ptm 128 0-255 pty:master
1454 pty_slave /dev/ttyp 3 0-255 pty:slave
1455 pty_master /dev/pty 2 0-255 pty:master
1456 serial /dev/cua 5 64-67 serial:callout
1457 serial /dev/ttyS 4 64-67 serial
1458 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1459 /dev/ptmx /dev/ptmx 5 2 system
1460 /dev/console /dev/console 5 1 system:console
1461 /dev/tty /dev/tty 5 0 system:/dev/tty
1462 unknown /dev/tty 4 1-63 console
1463
1464
14651.7 Miscellaneous kernel statistics in /proc/stat
1466-------------------------------------------------
1467
1468Various pieces of information about kernel activity are available in the
1469/proc/stat file. All of the numbers reported in this file are aggregates
1470since the system first booted. For a quick look, simply cat the file::
1471
1472 > cat /proc/stat
1473 cpu 237902850 368826709 106375398 1873517540 1135548 0 14507935 0 0 0
1474 cpu0 60045249 91891769 26331539 468411416 495718 0 5739640 0 0 0
1475 cpu1 59746288 91759249 26609887 468860630 312281 0 4384817 0 0 0
1476 cpu2 59489247 92985423 26904446 467808813 171668 0 2268998 0 0 0
1477 cpu3 58622065 92190267 26529524 468436680 155879 0 2114478 0 0 0
1478 intr 8688370575 8 3373 0 0 0 0 0 0 1 40791 0 0 353317 0 0 0 0 224789828 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 190974333 41958554 123983334 43 0 224593 0 0 0 <more 0's deleted>
1479 ctxt 22848221062
1480 btime 1605316999
1481 processes 746787147
1482 procs_running 2
1483 procs_blocked 0
1484 softirq 12121874454 100099120 3938138295 127375644 2795979 187870761 0 173808342 3072582055 52608 224184354
1485
1486The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1487lines. These numbers identify the amount of time the CPU has spent performing
1488different kinds of work. Time units are in USER_HZ (typically hundredths of a
1489second). The meanings of the columns are as follows, from left to right:
1490
1491- user: normal processes executing in user mode
1492- nice: niced processes executing in user mode
1493- system: processes executing in kernel mode
1494- idle: twiddling thumbs
1495- iowait: In a word, iowait stands for waiting for I/O to complete. But there
1496 are several problems:
1497
1498 1. CPU will not wait for I/O to complete, iowait is the time that a task is
1499 waiting for I/O to complete. When CPU goes into idle state for
1500 outstanding task I/O, another task will be scheduled on this CPU.
1501 2. In a multi-core CPU, the task waiting for I/O to complete is not running
1502 on any CPU, so the iowait of each CPU is difficult to calculate.
1503 3. The value of iowait field in /proc/stat will decrease in certain
1504 conditions.
1505
1506 So, the iowait is not reliable by reading from /proc/stat.
1507- irq: servicing interrupts
1508- softirq: servicing softirqs
1509- steal: involuntary wait
1510- guest: running a normal guest
1511- guest_nice: running a niced guest
1512
1513The "intr" line gives counts of interrupts serviced since boot time, for each
1514of the possible system interrupts. The first column is the total of all
1515interrupts serviced including unnumbered architecture specific interrupts;
1516each subsequent column is the total for that particular numbered interrupt.
1517Unnumbered interrupts are not shown, only summed into the total.
1518
1519The "ctxt" line gives the total number of context switches across all CPUs.
1520
1521The "btime" line gives the time at which the system booted, in seconds since
1522the Unix epoch.
1523
1524The "processes" line gives the number of processes and threads created, which
1525includes (but is not limited to) those created by calls to the fork() and
1526clone() system calls.
1527
1528The "procs_running" line gives the total number of threads that are
1529running or ready to run (i.e., the total number of runnable threads).
1530
1531The "procs_blocked" line gives the number of processes currently blocked,
1532waiting for I/O to complete.
1533
1534The "softirq" line gives counts of softirqs serviced since boot time, for each
1535of the possible system softirqs. The first column is the total of all
1536softirqs serviced; each subsequent column is the total for that particular
1537softirq.
1538
1539
15401.8 Ext4 file system parameters
1541-------------------------------
1542
1543Information about mounted ext4 file systems can be found in
1544/proc/fs/ext4. Each mounted filesystem will have a directory in
1545/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1546/proc/fs/ext4/sda9 or /proc/fs/ext4/dm-0). The files in each per-device
1547directory are shown in Table 1-12, below.
1548
1549.. table:: Table 1-12: Files in /proc/fs/ext4/<devname>
1550
1551 ============== ==========================================================
1552 File Content
1553 mb_groups details of multiblock allocator buddy cache of free blocks
1554 ============== ==========================================================
1555
15561.9 /proc/consoles
1557-------------------
1558Shows registered system console lines.
1559
1560To see which character device lines are currently used for the system console
1561/dev/console, you may simply look into the file /proc/consoles::
1562
1563 > cat /proc/consoles
1564 tty0 -WU (ECp) 4:7
1565 ttyS0 -W- (Ep) 4:64
1566
1567The columns are:
1568
1569+--------------------+-------------------------------------------------------+
1570| device | name of the device |
1571+====================+=======================================================+
1572| operations | * R = can do read operations |
1573| | * W = can do write operations |
1574| | * U = can do unblank |
1575+--------------------+-------------------------------------------------------+
1576| flags | * E = it is enabled |
1577| | * C = it is preferred console |
1578| | * B = it is primary boot console |
1579| | * p = it is used for printk buffer |
1580| | * b = it is not a TTY but a Braille device |
1581| | * a = it is safe to use when cpu is offline |
1582+--------------------+-------------------------------------------------------+
1583| major:minor | major and minor number of the device separated by a |
1584| | colon |
1585+--------------------+-------------------------------------------------------+
1586
1587Summary
1588-------
1589
1590The /proc file system serves information about the running system. It not only
1591allows access to process data but also allows you to request the kernel status
1592by reading files in the hierarchy.
1593
1594The directory structure of /proc reflects the types of information and makes
1595it easy, if not obvious, where to look for specific data.
1596
1597Chapter 2: Modifying System Parameters
1598======================================
1599
1600In This Chapter
1601---------------
1602
1603* Modifying kernel parameters by writing into files found in /proc/sys
1604* Exploring the files which modify certain parameters
1605* Review of the /proc/sys file tree
1606
1607------------------------------------------------------------------------------
1608
1609A very interesting part of /proc is the directory /proc/sys. This is not only
1610a source of information, it also allows you to change parameters within the
1611kernel. Be very careful when attempting this. You can optimize your system,
1612but you can also cause it to crash. Never alter kernel parameters on a
1613production system. Set up a development machine and test to make sure that
1614everything works the way you want it to. You may have no alternative but to
1615reboot the machine once an error has been made.
1616
1617To change a value, simply echo the new value into the file.
1618You need to be root to do this. You can create your own boot script
1619to perform this every time your system boots.
1620
1621The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1622general things in the operation of the Linux kernel. Since some of the files
1623can inadvertently disrupt your system, it is advisable to read both
1624documentation and source before actually making adjustments. In any case, be
1625very careful when writing to any of these files. The entries in /proc may
1626change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1627review the kernel documentation in the directory linux/Documentation.
1628This chapter is heavily based on the documentation included in the pre 2.2
1629kernels, and became part of it in version 2.2.1 of the Linux kernel.
1630
1631Please see: Documentation/admin-guide/sysctl/ directory for descriptions of
1632these entries.
1633
1634Summary
1635-------
1636
1637Certain aspects of kernel behavior can be modified at runtime, without the
1638need to recompile the kernel, or even to reboot the system. The files in the
1639/proc/sys tree can not only be read, but also modified. You can use the echo
1640command to write value into these files, thereby changing the default settings
1641of the kernel.
1642
1643
1644Chapter 3: Per-process Parameters
1645=================================
1646
16473.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1648--------------------------------------------------------------------------------
1649
1650These files can be used to adjust the badness heuristic used to select which
1651process gets killed in out of memory (oom) conditions.
1652
1653The badness heuristic assigns a value to each candidate task ranging from 0
1654(never kill) to 1000 (always kill) to determine which process is targeted. The
1655units are roughly a proportion along that range of allowed memory the process
1656may allocate from based on an estimation of its current memory and swap use.
1657For example, if a task is using all allowed memory, its badness score will be
16581000. If it is using half of its allowed memory, its score will be 500.
1659
1660The amount of "allowed" memory depends on the context in which the oom killer
1661was called. If it is due to the memory assigned to the allocating task's cpuset
1662being exhausted, the allowed memory represents the set of mems assigned to that
1663cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1664memory represents the set of mempolicy nodes. If it is due to a memory
1665limit (or swap limit) being reached, the allowed memory is that configured
1666limit. Finally, if it is due to the entire system being out of memory, the
1667allowed memory represents all allocatable resources.
1668
1669The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1670is used to determine which task to kill. Acceptable values range from -1000
1671(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1672polarize the preference for oom killing either by always preferring a certain
1673task or completely disabling it. The lowest possible value, -1000, is
1674equivalent to disabling oom killing entirely for that task since it will always
1675report a badness score of 0.
1676
1677Consequently, it is very simple for userspace to define the amount of memory to
1678consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1679example, is roughly equivalent to allowing the remainder of tasks sharing the
1680same system, cpuset, mempolicy, or memory controller resources to use at least
168150% more memory. A value of -500, on the other hand, would be roughly
1682equivalent to discounting 50% of the task's allowed memory from being considered
1683as scoring against the task.
1684
1685For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1686be used to tune the badness score. Its acceptable values range from -16
1687(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1688(OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1689scaled linearly with /proc/<pid>/oom_score_adj.
1690
1691The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1692value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1693requires CAP_SYS_RESOURCE.
1694
1695
16963.2 /proc/<pid>/oom_score - Display current oom-killer score
1697-------------------------------------------------------------
1698
1699This file can be used to check the current score used by the oom-killer for
1700any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1701process should be killed in an out-of-memory situation.
1702
1703Please note that the exported value includes oom_score_adj so it is
1704effectively in range [0,2000].
1705
1706
17073.3 /proc/<pid>/io - Display the IO accounting fields
1708-------------------------------------------------------
1709
1710This file contains IO statistics for each running process.
1711
1712Example
1713~~~~~~~
1714
1715::
1716
1717 test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1718 [1] 3828
1719
1720 test:/tmp # cat /proc/3828/io
1721 rchar: 323934931
1722 wchar: 323929600
1723 syscr: 632687
1724 syscw: 632675
1725 read_bytes: 0
1726 write_bytes: 323932160
1727 cancelled_write_bytes: 0
1728
1729
1730Description
1731~~~~~~~~~~~
1732
1733rchar
1734^^^^^
1735
1736I/O counter: chars read
1737The number of bytes which this task has caused to be read from storage. This
1738is simply the sum of bytes which this process passed to read() and pread().
1739It includes things like tty IO and it is unaffected by whether or not actual
1740physical disk IO was required (the read might have been satisfied from
1741pagecache).
1742
1743
1744wchar
1745^^^^^
1746
1747I/O counter: chars written
1748The number of bytes which this task has caused, or shall cause to be written
1749to disk. Similar caveats apply here as with rchar.
1750
1751
1752syscr
1753^^^^^
1754
1755I/O counter: read syscalls
1756Attempt to count the number of read I/O operations, i.e. syscalls like read()
1757and pread().
1758
1759
1760syscw
1761^^^^^
1762
1763I/O counter: write syscalls
1764Attempt to count the number of write I/O operations, i.e. syscalls like
1765write() and pwrite().
1766
1767
1768read_bytes
1769^^^^^^^^^^
1770
1771I/O counter: bytes read
1772Attempt to count the number of bytes which this process really did cause to
1773be fetched from the storage layer. Done at the submit_bio() level, so it is
1774accurate for block-backed filesystems. <please add status regarding NFS and
1775CIFS at a later time>
1776
1777
1778write_bytes
1779^^^^^^^^^^^
1780
1781I/O counter: bytes written
1782Attempt to count the number of bytes which this process caused to be sent to
1783the storage layer. This is done at page-dirtying time.
1784
1785
1786cancelled_write_bytes
1787^^^^^^^^^^^^^^^^^^^^^
1788
1789The big inaccuracy here is truncate. If a process writes 1MB to a file and
1790then deletes the file, it will in fact perform no writeout. But it will have
1791been accounted as having caused 1MB of write.
1792In other words: The number of bytes which this process caused to not happen,
1793by truncating pagecache. A task can cause "negative" IO too. If this task
1794truncates some dirty pagecache, some IO which another task has been accounted
1795for (in its write_bytes) will not be happening. We _could_ just subtract that
1796from the truncating task's write_bytes, but there is information loss in doing
1797that.
1798
1799
1800.. Note::
1801
1802 At its current implementation state, this is a bit racy on 32-bit machines:
1803 if process A reads process B's /proc/pid/io while process B is updating one
1804 of those 64-bit counters, process A could see an intermediate result.
1805
1806
1807More information about this can be found within the taskstats documentation in
1808Documentation/accounting.
1809
18103.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1811---------------------------------------------------------------
1812When a process is dumped, all anonymous memory is written to a core file as
1813long as the size of the core file isn't limited. But sometimes we don't want
1814to dump some memory segments, for example, huge shared memory or DAX.
1815Conversely, sometimes we want to save file-backed memory segments into a core
1816file, not only the individual files.
1817
1818/proc/<pid>/coredump_filter allows you to customize which memory segments
1819will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1820of memory types. If a bit of the bitmask is set, memory segments of the
1821corresponding memory type are dumped, otherwise they are not dumped.
1822
1823The following 9 memory types are supported:
1824
1825 - (bit 0) anonymous private memory
1826 - (bit 1) anonymous shared memory
1827 - (bit 2) file-backed private memory
1828 - (bit 3) file-backed shared memory
1829 - (bit 4) ELF header pages in file-backed private memory areas (it is
1830 effective only if the bit 2 is cleared)
1831 - (bit 5) hugetlb private memory
1832 - (bit 6) hugetlb shared memory
1833 - (bit 7) DAX private memory
1834 - (bit 8) DAX shared memory
1835
1836 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1837 are always dumped regardless of the bitmask status.
1838
1839 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
1840 only affected by bit 5-6, and DAX is only affected by bits 7-8.
1841
1842The default value of coredump_filter is 0x33; this means all anonymous memory
1843segments, ELF header pages and hugetlb private memory are dumped.
1844
1845If you don't want to dump all shared memory segments attached to pid 1234,
1846write 0x31 to the process's proc file::
1847
1848 $ echo 0x31 > /proc/1234/coredump_filter
1849
1850When a new process is created, the process inherits the bitmask status from its
1851parent. It is useful to set up coredump_filter before the program runs.
1852For example::
1853
1854 $ echo 0x7 > /proc/self/coredump_filter
1855 $ ./some_program
1856
18573.5 /proc/<pid>/mountinfo - Information about mounts
1858--------------------------------------------------------
1859
1860This file contains lines of the form::
1861
1862 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1863 (1)(2)(3) (4) (5) (6) (n…m) (m+1)(m+2) (m+3) (m+4)
1864
1865 (1) mount ID: unique identifier of the mount (may be reused after umount)
1866 (2) parent ID: ID of parent (or of self for the top of the mount tree)
1867 (3) major:minor: value of st_dev for files on filesystem
1868 (4) root: root of the mount within the filesystem
1869 (5) mount point: mount point relative to the process's root
1870 (6) mount options: per mount options
1871 (n…m) optional fields: zero or more fields of the form "tag[:value]"
1872 (m+1) separator: marks the end of the optional fields
1873 (m+2) filesystem type: name of filesystem of the form "type[.subtype]"
1874 (m+3) mount source: filesystem specific information or "none"
1875 (m+4) super options: per super block options
1876
1877Parsers should ignore all unrecognised optional fields. Currently the
1878possible optional fields are:
1879
1880================ ==============================================================
1881shared:X mount is shared in peer group X
1882master:X mount is slave to peer group X
1883propagate_from:X mount is slave and receives propagation from peer group X [#]_
1884unbindable mount is unbindable
1885================ ==============================================================
1886
1887.. [#] X is the closest dominant peer group under the process's root. If
1888 X is the immediate master of the mount, or if there's no dominant peer
1889 group under the same root, then only the "master:X" field is present
1890 and not the "propagate_from:X" field.
1891
1892For more information on mount propagation see:
1893
1894 Documentation/filesystems/sharedsubtree.rst
1895
1896
18973.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1898--------------------------------------------------------
1899These files provide a method to access a task's comm value. It also allows for
1900a task to set its own or one of its thread siblings comm value. The comm value
1901is limited in size compared to the cmdline value, so writing anything longer
1902then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1903comm value.
1904
1905
19063.7 /proc/<pid>/task/<tid>/children - Information about task children
1907-------------------------------------------------------------------------
1908This file provides a fast way to retrieve first level children pids
1909of a task pointed by <pid>/<tid> pair. The format is a space separated
1910stream of pids.
1911
1912Note the "first level" here -- if a child has its own children they will
1913not be listed here; one needs to read /proc/<children-pid>/task/<tid>/children
1914to obtain the descendants.
1915
1916Since this interface is intended to be fast and cheap it doesn't
1917guarantee to provide precise results and some children might be
1918skipped, especially if they've exited right after we printed their
1919pids, so one needs to either stop or freeze processes being inspected
1920if precise results are needed.
1921
1922
19233.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
1924---------------------------------------------------------------
1925This file provides information associated with an opened file. The regular
1926files have at least four fields -- 'pos', 'flags', 'mnt_id' and 'ino'.
1927The 'pos' represents the current offset of the opened file in decimal
1928form [see lseek(2) for details], 'flags' denotes the octal O_xxx mask the
1929file has been created with [see open(2) for details] and 'mnt_id' represents
1930mount ID of the file system containing the opened file [see 3.5
1931/proc/<pid>/mountinfo for details]. 'ino' represents the inode number of
1932the file.
1933
1934A typical output is::
1935
1936 pos: 0
1937 flags: 0100002
1938 mnt_id: 19
1939 ino: 63107
1940
1941All locks associated with a file descriptor are shown in its fdinfo too::
1942
1943 lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF
1944
1945The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1946pair provide additional information particular to the objects they represent.
1947
1948Eventfd files
1949~~~~~~~~~~~~~
1950
1951::
1952
1953 pos: 0
1954 flags: 04002
1955 mnt_id: 9
1956 ino: 63107
1957 eventfd-count: 5a
1958
1959where 'eventfd-count' is hex value of a counter.
1960
1961Signalfd files
1962~~~~~~~~~~~~~~
1963
1964::
1965
1966 pos: 0
1967 flags: 04002
1968 mnt_id: 9
1969 ino: 63107
1970 sigmask: 0000000000000200
1971
1972where 'sigmask' is hex value of the signal mask associated
1973with a file.
1974
1975Epoll files
1976~~~~~~~~~~~
1977
1978::
1979
1980 pos: 0
1981 flags: 02
1982 mnt_id: 9
1983 ino: 63107
1984 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7
1985
1986where 'tfd' is a target file descriptor number in decimal form,
1987'events' is events mask being watched and the 'data' is data
1988associated with a target [see epoll(7) for more details].
1989
1990The 'pos' is current offset of the target file in decimal form
1991[see lseek(2)], 'ino' and 'sdev' are inode and device numbers
1992where target file resides, all in hex format.
1993
1994Fsnotify files
1995~~~~~~~~~~~~~~
1996For inotify files the format is the following::
1997
1998 pos: 0
1999 flags: 02000000
2000 mnt_id: 9
2001 ino: 63107
2002 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
2003
2004where 'wd' is a watch descriptor in decimal form, i.e. a target file
2005descriptor number, 'ino' and 'sdev' are inode and device where the
2006target file resides and the 'mask' is the mask of events, all in hex
2007form [see inotify(7) for more details].
2008
2009If the kernel was built with exportfs support, the path to the target
2010file is encoded as a file handle. The file handle is provided by three
2011fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
2012format.
2013
2014If the kernel is built without exportfs support the file handle won't be
2015printed out.
2016
2017If there is no inotify mark attached yet the 'inotify' line will be omitted.
2018
2019For fanotify files the format is::
2020
2021 pos: 0
2022 flags: 02
2023 mnt_id: 9
2024 ino: 63107
2025 fanotify flags:10 event-flags:0
2026 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
2027 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
2028
2029where fanotify 'flags' and 'event-flags' are values used in fanotify_init
2030call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
2031flags associated with mark which are tracked separately from events
2032mask. 'ino' and 'sdev' are target inode and device, 'mask' is the events
2033mask and 'ignored_mask' is the mask of events which are to be ignored.
2034All are in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
2035provide information about flags and mask used in fanotify_mark
2036call [see fsnotify manpage for details].
2037
2038While the first three lines are mandatory and always printed, the rest is
2039optional and may be omitted if no marks created yet.
2040
2041Timerfd files
2042~~~~~~~~~~~~~
2043
2044::
2045
2046 pos: 0
2047 flags: 02
2048 mnt_id: 9
2049 ino: 63107
2050 clockid: 0
2051 ticks: 0
2052 settime flags: 01
2053 it_value: (0, 49406829)
2054 it_interval: (1, 0)
2055
2056where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
2057that have occurred [see timerfd_create(2) for details]. 'settime flags' are
2058flags in octal form been used to setup the timer [see timerfd_settime(2) for
2059details]. 'it_value' is remaining time until the timer expiration.
2060'it_interval' is the interval for the timer. Note the timer might be set up
2061with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
2062still exhibits timer's remaining time.
2063
2064DMA Buffer files
2065~~~~~~~~~~~~~~~~
2066
2067::
2068
2069 pos: 0
2070 flags: 04002
2071 mnt_id: 9
2072 ino: 63107
2073 size: 32768
2074 count: 2
2075 exp_name: system-heap
2076
2077where 'size' is the size of the DMA buffer in bytes. 'count' is the file count of
2078the DMA buffer file. 'exp_name' is the name of the DMA buffer exporter.
2079
20803.9 /proc/<pid>/map_files - Information about memory mapped files
2081---------------------------------------------------------------------
2082This directory contains symbolic links which represent memory mapped files
2083the process is maintaining. Example output::
2084
2085 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
2086 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
2087 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
2088 | ...
2089 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
2090 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
2091
2092The name of a link represents the virtual memory bounds of a mapping, i.e.
2093vm_area_struct::vm_start-vm_area_struct::vm_end.
2094
2095The main purpose of the map_files is to retrieve a set of memory mapped
2096files in a fast way instead of parsing /proc/<pid>/maps or
2097/proc/<pid>/smaps, both of which contain many more records. At the same
2098time one can open(2) mappings from the listings of two processes and
2099comparing their inode numbers to figure out which anonymous memory areas
2100are actually shared.
2101
21023.10 /proc/<pid>/timerslack_ns - Task timerslack value
2103---------------------------------------------------------
2104This file provides the value of the task's timerslack value in nanoseconds.
2105This value specifies an amount of time that normal timers may be deferred
2106in order to coalesce timers and avoid unnecessary wakeups.
2107
2108This allows a task's interactivity vs power consumption tradeoff to be
2109adjusted.
2110
2111Writing 0 to the file will set the task's timerslack to the default value.
2112
2113Valid values are from 0 - ULLONG_MAX
2114
2115An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
2116permissions on the task specified to change its timerslack_ns value.
2117
21183.11 /proc/<pid>/patch_state - Livepatch patch operation state
2119-----------------------------------------------------------------
2120When CONFIG_LIVEPATCH is enabled, this file displays the value of the
2121patch state for the task.
2122
2123A value of '-1' indicates that no patch is in transition.
2124
2125A value of '0' indicates that a patch is in transition and the task is
2126unpatched. If the patch is being enabled, then the task hasn't been
2127patched yet. If the patch is being disabled, then the task has already
2128been unpatched.
2129
2130A value of '1' indicates that a patch is in transition and the task is
2131patched. If the patch is being enabled, then the task has already been
2132patched. If the patch is being disabled, then the task hasn't been
2133unpatched yet.
2134
21353.12 /proc/<pid>/arch_status - task architecture specific status
2136-------------------------------------------------------------------
2137When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the
2138architecture specific status of the task.
2139
2140Example
2141~~~~~~~
2142
2143::
2144
2145 $ cat /proc/6753/arch_status
2146 AVX512_elapsed_ms: 8
2147
2148Description
2149~~~~~~~~~~~
2150
2151x86 specific entries
2152~~~~~~~~~~~~~~~~~~~~~
2153
2154AVX512_elapsed_ms
2155^^^^^^^^^^^^^^^^^^
2156
2157 If AVX512 is supported on the machine, this entry shows the milliseconds
2158 elapsed since the last time AVX512 usage was recorded. The recording
2159 happens on a best effort basis when a task is scheduled out. This means
2160 that the value depends on two factors:
2161
2162 1) The time which the task spent on the CPU without being scheduled
2163 out. With CPU isolation and a single runnable task this can take
2164 several seconds.
2165
2166 2) The time since the task was scheduled out last. Depending on the
2167 reason for being scheduled out (time slice exhausted, syscall ...)
2168 this can be arbitrary long time.
2169
2170 As a consequence the value cannot be considered precise and authoritative
2171 information. The application which uses this information has to be aware
2172 of the overall scenario on the system in order to determine whether a
2173 task is a real AVX512 user or not. Precise information can be obtained
2174 with performance counters.
2175
2176 A special value of '-1' indicates that no AVX512 usage was recorded, thus
2177 the task is unlikely an AVX512 user, but depends on the workload and the
2178 scheduling scenario, it also could be a false negative mentioned above.
2179
21803.13 /proc/<pid>/fd - List of symlinks to open files
2181-------------------------------------------------------
2182This directory contains symbolic links which represent open files
2183the process is maintaining. Example output::
2184
2185 lr-x------ 1 root root 64 Sep 20 17:53 0 -> /dev/null
2186 l-wx------ 1 root root 64 Sep 20 17:53 1 -> /dev/null
2187 lrwx------ 1 root root 64 Sep 20 17:53 10 -> 'socket:[12539]'
2188 lrwx------ 1 root root 64 Sep 20 17:53 11 -> 'socket:[12540]'
2189 lrwx------ 1 root root 64 Sep 20 17:53 12 -> 'socket:[12542]'
2190
2191The number of open files for the process is stored in 'size' member
2192of stat() output for /proc/<pid>/fd for fast access.
2193-------------------------------------------------------
2194
2195
2196Chapter 4: Configuring procfs
2197=============================
2198
21994.1 Mount options
2200---------------------
2201
2202The following mount options are supported:
2203
2204 ========= ========================================================
2205 hidepid= Set /proc/<pid>/ access mode.
2206 gid= Set the group authorized to learn processes information.
2207 subset= Show only the specified subset of procfs.
2208 ========= ========================================================
2209
2210hidepid=off or hidepid=0 means classic mode - everybody may access all
2211/proc/<pid>/ directories (default).
2212
2213hidepid=noaccess or hidepid=1 means users may not access any /proc/<pid>/
2214directories but their own. Sensitive files like cmdline, sched*, status are now
2215protected against other users. This makes it impossible to learn whether any
2216user runs specific program (given the program doesn't reveal itself by its
2217behaviour). As an additional bonus, as /proc/<pid>/cmdline is unaccessible for
2218other users, poorly written programs passing sensitive information via program
2219arguments are now protected against local eavesdroppers.
2220
2221hidepid=invisible or hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be
2222fully invisible to other users. It doesn't mean that it hides a fact whether a
2223process with a specific pid value exists (it can be learned by other means, e.g.
2224by "kill -0 $PID"), but it hides process' uid and gid, which may be learned by
2225stat()'ing /proc/<pid>/ otherwise. It greatly complicates an intruder's task of
2226gathering information about running processes, whether some daemon runs with
2227elevated privileges, whether other user runs some sensitive program, whether
2228other users run any program at all, etc.
2229
2230hidepid=ptraceable or hidepid=4 means that procfs should only contain
2231/proc/<pid>/ directories that the caller can ptrace.
2232
2233gid= defines a group authorized to learn processes information otherwise
2234prohibited by hidepid=. If you use some daemon like identd which needs to learn
2235information about processes information, just add identd to this group.
2236
2237subset=pid hides all top level files and directories in the procfs that
2238are not related to tasks.
2239
2240Chapter 5: Filesystem behavior
2241==============================
2242
2243Originally, before the advent of pid namespace, procfs was a global file
2244system. It means that there was only one procfs instance in the system.
2245
2246When pid namespace was added, a separate procfs instance was mounted in
2247each pid namespace. So, procfs mount options are global among all
2248mountpoints within the same namespace::
2249
2250 # grep ^proc /proc/mounts
2251 proc /proc proc rw,relatime,hidepid=2 0 0
2252
2253 # strace -e mount mount -o hidepid=1 -t proc proc /tmp/proc
2254 mount("proc", "/tmp/proc", "proc", 0, "hidepid=1") = 0
2255 +++ exited with 0 +++
2256
2257 # grep ^proc /proc/mounts
2258 proc /proc proc rw,relatime,hidepid=2 0 0
2259 proc /tmp/proc proc rw,relatime,hidepid=2 0 0
2260
2261and only after remounting procfs mount options will change at all
2262mountpoints::
2263
2264 # mount -o remount,hidepid=1 -t proc proc /tmp/proc
2265
2266 # grep ^proc /proc/mounts
2267 proc /proc proc rw,relatime,hidepid=1 0 0
2268 proc /tmp/proc proc rw,relatime,hidepid=1 0 0
2269
2270This behavior is different from the behavior of other filesystems.
2271
2272The new procfs behavior is more like other filesystems. Each procfs mount
2273creates a new procfs instance. Mount options affect own procfs instance.
2274It means that it became possible to have several procfs instances
2275displaying tasks with different filtering options in one pid namespace::
2276
2277 # mount -o hidepid=invisible -t proc proc /proc
2278 # mount -o hidepid=noaccess -t proc proc /tmp/proc
2279 # grep ^proc /proc/mounts
2280 proc /proc proc rw,relatime,hidepid=invisible 0 0
2281 proc /tmp/proc proc rw,relatime,hidepid=noaccess 0 0