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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 SpeculationIndirectBranch: conditional enabled
214 voluntary_ctxt_switches: 0
215 nonvoluntary_ctxt_switches: 1
216
217This shows you nearly the same information you would get if you viewed it with
218the ps command. In fact, ps uses the proc file system to obtain its
219information. But you get a more detailed view of the process by reading the
220file /proc/PID/status. It fields are described in table 1-2.
221
222The statm file contains more detailed information about the process
223memory usage. Its seven fields are explained in Table 1-3. The stat file
224contains detailed information about the process itself. Its fields are
225explained in Table 1-4.
226
227(for SMP CONFIG users)
228
229For making accounting scalable, RSS related information are handled in an
230asynchronous manner and the value may not be very precise. To see a precise
231snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
232It's slow but very precise.
233
234.. table:: Table 1-2: Contents of the status files (as of 4.19)
235
236 ========================== ===================================================
237 Field Content
238 ========================== ===================================================
239 Name filename of the executable
240 Umask file mode creation mask
241 State state (R is running, S is sleeping, D is sleeping
242 in an uninterruptible wait, Z is zombie,
243 T is traced or stopped)
244 Tgid thread group ID
245 Ngid NUMA group ID (0 if none)
246 Pid process id
247 PPid process id of the parent process
248 TracerPid PID of process tracing this process (0 if not)
249 Uid Real, effective, saved set, and file system UIDs
250 Gid Real, effective, saved set, and file system GIDs
251 FDSize number of file descriptor slots currently allocated
252 Groups supplementary group list
253 NStgid descendant namespace thread group ID hierarchy
254 NSpid descendant namespace process ID hierarchy
255 NSpgid descendant namespace process group ID hierarchy
256 NSsid descendant namespace session ID hierarchy
257 VmPeak peak virtual memory size
258 VmSize total program size
259 VmLck locked memory size
260 VmPin pinned memory size
261 VmHWM peak resident set size ("high water mark")
262 VmRSS size of memory portions. It contains the three
263 following parts
264 (VmRSS = RssAnon + RssFile + RssShmem)
265 RssAnon size of resident anonymous memory
266 RssFile size of resident file mappings
267 RssShmem size of resident shmem memory (includes SysV shm,
268 mapping of tmpfs and shared anonymous mappings)
269 VmData size of private data segments
270 VmStk size of stack segments
271 VmExe size of text segment
272 VmLib size of shared library code
273 VmPTE size of page table entries
274 VmSwap amount of swap used by anonymous private data
275 (shmem swap usage is not included)
276 HugetlbPages size of hugetlb memory portions
277 CoreDumping process's memory is currently being dumped
278 (killing the process may lead to a corrupted core)
279 THP_enabled process is allowed to use THP (returns 0 when
280 PR_SET_THP_DISABLE is set on the process
281 Threads number of threads
282 SigQ number of signals queued/max. number for queue
283 SigPnd bitmap of pending signals for the thread
284 ShdPnd bitmap of shared pending signals for the process
285 SigBlk bitmap of blocked signals
286 SigIgn bitmap of ignored signals
287 SigCgt bitmap of caught signals
288 CapInh bitmap of inheritable capabilities
289 CapPrm bitmap of permitted capabilities
290 CapEff bitmap of effective capabilities
291 CapBnd bitmap of capabilities bounding set
292 CapAmb bitmap of ambient capabilities
293 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
294 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
295 Speculation_Store_Bypass speculative store bypass mitigation status
296 SpeculationIndirectBranch indirect branch speculation mode
297 Cpus_allowed mask of CPUs on which this process may run
298 Cpus_allowed_list Same as previous, but in "list format"
299 Mems_allowed mask of memory nodes allowed to this process
300 Mems_allowed_list Same as previous, but in "list format"
301 voluntary_ctxt_switches number of voluntary context switches
302 nonvoluntary_ctxt_switches number of non voluntary context switches
303 ========================== ===================================================
304
305
306.. table:: Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
307
308 ======== =============================== ==============================
309 Field Content
310 ======== =============================== ==============================
311 size total program size (pages) (same as VmSize in status)
312 resident size of memory portions (pages) (same as VmRSS in status)
313 shared number of pages that are shared (i.e. backed by a file, same
314 as RssFile+RssShmem in status)
315 trs number of pages that are 'code' (not including libs; broken,
316 includes data segment)
317 lrs number of pages of library (always 0 on 2.6)
318 drs number of pages of data/stack (including libs; broken,
319 includes library text)
320 dt number of dirty pages (always 0 on 2.6)
321 ======== =============================== ==============================
322
323
324.. table:: Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
325
326 ============= ===============================================================
327 Field Content
328 ============= ===============================================================
329 pid process id
330 tcomm filename of the executable
331 state state (R is running, S is sleeping, D is sleeping in an
332 uninterruptible wait, Z is zombie, T is traced or stopped)
333 ppid process id of the parent process
334 pgrp pgrp of the process
335 sid session id
336 tty_nr tty the process uses
337 tty_pgrp pgrp of the tty
338 flags task flags
339 min_flt number of minor faults
340 cmin_flt number of minor faults with child's
341 maj_flt number of major faults
342 cmaj_flt number of major faults with child's
343 utime user mode jiffies
344 stime kernel mode jiffies
345 cutime user mode jiffies with child's
346 cstime kernel mode jiffies with child's
347 priority priority level
348 nice nice level
349 num_threads number of threads
350 it_real_value (obsolete, always 0)
351 start_time time the process started after system boot
352 vsize virtual memory size
353 rss resident set memory size
354 rsslim current limit in bytes on the rss
355 start_code address above which program text can run
356 end_code address below which program text can run
357 start_stack address of the start of the main process stack
358 esp current value of ESP
359 eip current value of EIP
360 pending bitmap of pending signals
361 blocked bitmap of blocked signals
362 sigign bitmap of ignored signals
363 sigcatch bitmap of caught signals
364 0 (place holder, used to be the wchan address,
365 use /proc/PID/wchan instead)
366 0 (place holder)
367 0 (place holder)
368 exit_signal signal to send to parent thread on exit
369 task_cpu which CPU the task is scheduled on
370 rt_priority realtime priority
371 policy scheduling policy (man sched_setscheduler)
372 blkio_ticks time spent waiting for block IO
373 gtime guest time of the task in jiffies
374 cgtime guest time of the task children in jiffies
375 start_data address above which program data+bss is placed
376 end_data address below which program data+bss is placed
377 start_brk address above which program heap can be expanded with brk()
378 arg_start address above which program command line is placed
379 arg_end address below which program command line is placed
380 env_start address above which program environment is placed
381 env_end address below which program environment is placed
382 exit_code the thread's exit_code in the form reported by the waitpid
383 system call
384 ============= ===============================================================
385
386The /proc/PID/maps file contains the currently mapped memory regions and
387their access permissions.
388
389The format is::
390
391 address perms offset dev inode pathname
392
393 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test
394 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
395 0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
396 a7cb1000-a7cb2000 ---p 00000000 00:00 0
397 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
398 a7eb2000-a7eb3000 ---p 00000000 00:00 0
399 a7eb3000-a7ed5000 rw-p 00000000 00:00 0
400 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
401 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
402 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
403 a800b000-a800e000 rw-p 00000000 00:00 0
404 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
405 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
406 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
407 a8024000-a8027000 rw-p 00000000 00:00 0
408 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
409 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
410 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
411 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
412 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
413
414where "address" is the address space in the process that it occupies, "perms"
415is a set of permissions::
416
417 r = read
418 w = write
419 x = execute
420 s = shared
421 p = private (copy on write)
422
423"offset" is the offset into the mapping, "dev" is the device (major:minor), and
424"inode" is the inode on that device. 0 indicates that no inode is associated
425with the memory region, as the case would be with BSS (uninitialized data).
426The "pathname" shows the name associated file for this mapping. If the mapping
427is not associated with a file:
428
429 ======= ====================================
430 [heap] the heap of the program
431 [stack] the stack of the main process
432 [vdso] the "virtual dynamic shared object",
433 the kernel system call handler
434 ======= ====================================
435
436 or if empty, the mapping is anonymous.
437
438The /proc/PID/smaps is an extension based on maps, showing the memory
439consumption for each of the process's mappings. For each mapping (aka Virtual
440Memory Area, or VMA) there is a series of lines such as the following::
441
442 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
443
444 Size: 1084 kB
445 KernelPageSize: 4 kB
446 MMUPageSize: 4 kB
447 Rss: 892 kB
448 Pss: 374 kB
449 Shared_Clean: 892 kB
450 Shared_Dirty: 0 kB
451 Private_Clean: 0 kB
452 Private_Dirty: 0 kB
453 Referenced: 892 kB
454 Anonymous: 0 kB
455 LazyFree: 0 kB
456 AnonHugePages: 0 kB
457 ShmemPmdMapped: 0 kB
458 Shared_Hugetlb: 0 kB
459 Private_Hugetlb: 0 kB
460 Swap: 0 kB
461 SwapPss: 0 kB
462 KernelPageSize: 4 kB
463 MMUPageSize: 4 kB
464 Locked: 0 kB
465 THPeligible: 0
466 VmFlags: rd ex mr mw me dw
467
468The first of these lines shows the same information as is displayed for the
469mapping in /proc/PID/maps. Following lines show the size of the mapping
470(size); the size of each page allocated when backing a VMA (KernelPageSize),
471which is usually the same as the size in the page table entries; the page size
472used by the MMU when backing a VMA (in most cases, the same as KernelPageSize);
473the amount of the mapping that is currently resident in RAM (RSS); the
474process' proportional share of this mapping (PSS); and the number of clean and
475dirty shared and private pages in the mapping.
476
477The "proportional set size" (PSS) of a process is the count of pages it has
478in memory, where each page is divided by the number of processes sharing it.
479So if a process has 1000 pages all to itself, and 1000 shared with one other
480process, its PSS will be 1500.
481
482Note that even a page which is part of a MAP_SHARED mapping, but has only
483a single pte mapped, i.e. is currently used by only one process, is accounted
484as private and not as shared.
485
486"Referenced" indicates the amount of memory currently marked as referenced or
487accessed.
488
489"Anonymous" shows the amount of memory that does not belong to any file. Even
490a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
491and a page is modified, the file page is replaced by a private anonymous copy.
492
493"LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE).
494The memory isn't freed immediately with madvise(). It's freed in memory
495pressure if the memory is clean. Please note that the printed value might
496be lower than the real value due to optimizations used in the current
497implementation. If this is not desirable please file a bug report.
498
499"AnonHugePages" shows the ammount of memory backed by transparent hugepage.
500
501"ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by
502huge pages.
503
504"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
505hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
506reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
507
508"Swap" shows how much would-be-anonymous memory is also used, but out on swap.
509
510For shmem mappings, "Swap" includes also the size of the mapped (and not
511replaced by copy-on-write) part of the underlying shmem object out on swap.
512"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
513does not take into account swapped out page of underlying shmem objects.
514"Locked" indicates whether the mapping is locked in memory or not.
515"THPeligible" indicates whether the mapping is eligible for allocating THP
516pages - 1 if true, 0 otherwise. It just shows the current status.
517
518"VmFlags" field deserves a separate description. This member represents the
519kernel flags associated with the particular virtual memory area in two letter
520encoded manner. The codes are the following:
521
522 == =======================================
523 rd readable
524 wr writeable
525 ex executable
526 sh shared
527 mr may read
528 mw may write
529 me may execute
530 ms may share
531 gd stack segment growns down
532 pf pure PFN range
533 dw disabled write to the mapped file
534 lo pages are locked in memory
535 io memory mapped I/O area
536 sr sequential read advise provided
537 rr random read advise provided
538 dc do not copy area on fork
539 de do not expand area on remapping
540 ac area is accountable
541 nr swap space is not reserved for the area
542 ht area uses huge tlb pages
543 sf synchronous page fault
544 ar architecture specific flag
545 wf wipe on fork
546 dd do not include area into core dump
547 sd soft dirty flag
548 mm mixed map area
549 hg huge page advise flag
550 nh no huge page advise flag
551 mg mergable advise flag
552 bt arm64 BTI guarded page
553 mt arm64 MTE allocation tags are enabled
554 um userfaultfd missing tracking
555 uw userfaultfd wr-protect tracking
556 == =======================================
557
558Note that there is no guarantee that every flag and associated mnemonic will
559be present in all further kernel releases. Things get changed, the flags may
560be vanished or the reverse -- new added. Interpretation of their meaning
561might change in future as well. So each consumer of these flags has to
562follow each specific kernel version for the exact semantic.
563
564This file is only present if the CONFIG_MMU kernel configuration option is
565enabled.
566
567Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent
568output can be achieved only in the single read call).
569
570This typically manifests when doing partial reads of these files while the
571memory map is being modified. Despite the races, we do provide the following
572guarantees:
573
5741) The mapped addresses never go backwards, which implies no two
575 regions will ever overlap.
5762) If there is something at a given vaddr during the entirety of the
577 life of the smaps/maps walk, there will be some output for it.
578
579The /proc/PID/smaps_rollup file includes the same fields as /proc/PID/smaps,
580but their values are the sums of the corresponding values for all mappings of
581the process. Additionally, it contains these fields:
582
583- Pss_Anon
584- Pss_File
585- Pss_Shmem
586
587They represent the proportional shares of anonymous, file, and shmem pages, as
588described for smaps above. These fields are omitted in smaps since each
589mapping identifies the type (anon, file, or shmem) of all pages it contains.
590Thus all information in smaps_rollup can be derived from smaps, but at a
591significantly higher cost.
592
593The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
594bits on both physical and virtual pages associated with a process, and the
595soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst
596for details).
597To clear the bits for all the pages associated with the process::
598
599 > echo 1 > /proc/PID/clear_refs
600
601To clear the bits for the anonymous pages associated with the process::
602
603 > echo 2 > /proc/PID/clear_refs
604
605To clear the bits for the file mapped pages associated with the process::
606
607 > echo 3 > /proc/PID/clear_refs
608
609To clear the soft-dirty bit::
610
611 > echo 4 > /proc/PID/clear_refs
612
613To reset the peak resident set size ("high water mark") to the process's
614current value::
615
616 > echo 5 > /proc/PID/clear_refs
617
618Any other value written to /proc/PID/clear_refs will have no effect.
619
620The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
621using /proc/kpageflags and number of times a page is mapped using
622/proc/kpagecount. For detailed explanation, see
623Documentation/admin-guide/mm/pagemap.rst.
624
625The /proc/pid/numa_maps is an extension based on maps, showing the memory
626locality and binding policy, as well as the memory usage (in pages) of
627each mapping. The output follows a general format where mapping details get
628summarized separated by blank spaces, one mapping per each file line::
629
630 address policy mapping details
631
632 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
633 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
634 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
635 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
636 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
637 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
638 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
639 320698b000 default file=/lib64/libc-2.12.so
640 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
641 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
642 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
643 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
644 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
645 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
646 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
647 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
648
649Where:
650
651"address" is the starting address for the mapping;
652
653"policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst);
654
655"mapping details" summarizes mapping data such as mapping type, page usage counters,
656node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
657size, in KB, that is backing the mapping up.
658
6591.2 Kernel data
660---------------
661
662Similar to the process entries, the kernel data files give information about
663the running kernel. The files used to obtain this information are contained in
664/proc and are listed in Table 1-5. Not all of these will be present in your
665system. It depends on the kernel configuration and the loaded modules, which
666files are there, and which are missing.
667
668.. table:: Table 1-5: Kernel info in /proc
669
670 ============ ===============================================================
671 File Content
672 ============ ===============================================================
673 apm Advanced power management info
674 buddyinfo Kernel memory allocator information (see text) (2.5)
675 bus Directory containing bus specific information
676 cmdline Kernel command line
677 cpuinfo Info about the CPU
678 devices Available devices (block and character)
679 dma Used DMS channels
680 filesystems Supported filesystems
681 driver Various drivers grouped here, currently rtc (2.4)
682 execdomains Execdomains, related to security (2.4)
683 fb Frame Buffer devices (2.4)
684 fs File system parameters, currently nfs/exports (2.4)
685 ide Directory containing info about the IDE subsystem
686 interrupts Interrupt usage
687 iomem Memory map (2.4)
688 ioports I/O port usage
689 irq Masks for irq to cpu affinity (2.4)(smp?)
690 isapnp ISA PnP (Plug&Play) Info (2.4)
691 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
692 kmsg Kernel messages
693 ksyms Kernel symbol table
694 loadavg Load average of last 1, 5 & 15 minutes;
695 number of processes currently runnable (running or on ready queue);
696 total number of processes in system;
697 last pid created.
698 All fields are separated by one space except "number of
699 processes currently runnable" and "total number of processes
700 in system", which are separated by a slash ('/'). Example:
701 0.61 0.61 0.55 3/828 22084
702 locks Kernel locks
703 meminfo Memory info
704 misc Miscellaneous
705 modules List of loaded modules
706 mounts Mounted filesystems
707 net Networking info (see text)
708 pagetypeinfo Additional page allocator information (see text) (2.5)
709 partitions Table of partitions known to the system
710 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
711 decoupled by lspci (2.4)
712 rtc Real time clock
713 scsi SCSI info (see text)
714 slabinfo Slab pool info
715 softirqs softirq usage
716 stat Overall statistics
717 swaps Swap space utilization
718 sys See chapter 2
719 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
720 tty Info of tty drivers
721 uptime Wall clock since boot, combined idle time of all cpus
722 version Kernel version
723 video bttv info of video resources (2.4)
724 vmallocinfo Show vmalloced areas
725 ============ ===============================================================
726
727You can, for example, check which interrupts are currently in use and what
728they are used for by looking in the file /proc/interrupts::
729
730 > cat /proc/interrupts
731 CPU0
732 0: 8728810 XT-PIC timer
733 1: 895 XT-PIC keyboard
734 2: 0 XT-PIC cascade
735 3: 531695 XT-PIC aha152x
736 4: 2014133 XT-PIC serial
737 5: 44401 XT-PIC pcnet_cs
738 8: 2 XT-PIC rtc
739 11: 8 XT-PIC i82365
740 12: 182918 XT-PIC PS/2 Mouse
741 13: 1 XT-PIC fpu
742 14: 1232265 XT-PIC ide0
743 15: 7 XT-PIC ide1
744 NMI: 0
745
746In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
747output of a SMP machine)::
748
749 > cat /proc/interrupts
750
751 CPU0 CPU1
752 0: 1243498 1214548 IO-APIC-edge timer
753 1: 8949 8958 IO-APIC-edge keyboard
754 2: 0 0 XT-PIC cascade
755 5: 11286 10161 IO-APIC-edge soundblaster
756 8: 1 0 IO-APIC-edge rtc
757 9: 27422 27407 IO-APIC-edge 3c503
758 12: 113645 113873 IO-APIC-edge PS/2 Mouse
759 13: 0 0 XT-PIC fpu
760 14: 22491 24012 IO-APIC-edge ide0
761 15: 2183 2415 IO-APIC-edge ide1
762 17: 30564 30414 IO-APIC-level eth0
763 18: 177 164 IO-APIC-level bttv
764 NMI: 2457961 2457959
765 LOC: 2457882 2457881
766 ERR: 2155
767
768NMI is incremented in this case because every timer interrupt generates a NMI
769(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
770
771LOC is the local interrupt counter of the internal APIC of every CPU.
772
773ERR is incremented in the case of errors in the IO-APIC bus (the bus that
774connects the CPUs in a SMP system. This means that an error has been detected,
775the IO-APIC automatically retry the transmission, so it should not be a big
776problem, but you should read the SMP-FAQ.
777
778In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
779/proc/interrupts to display every IRQ vector in use by the system, not
780just those considered 'most important'. The new vectors are:
781
782THR
783 interrupt raised when a machine check threshold counter
784 (typically counting ECC corrected errors of memory or cache) exceeds
785 a configurable threshold. Only available on some systems.
786
787TRM
788 a thermal event interrupt occurs when a temperature threshold
789 has been exceeded for the CPU. This interrupt may also be generated
790 when the temperature drops back to normal.
791
792SPU
793 a spurious interrupt is some interrupt that was raised then lowered
794 by some IO device before it could be fully processed by the APIC. Hence
795 the APIC sees the interrupt but does not know what device it came from.
796 For this case the APIC will generate the interrupt with a IRQ vector
797 of 0xff. This might also be generated by chipset bugs.
798
799RES, CAL, TLB
800 rescheduling, call and TLB flush interrupts are
801 sent from one CPU to another per the needs of the OS. Typically,
802 their statistics are used by kernel developers and interested users to
803 determine the occurrence of interrupts of the given type.
804
805The above IRQ vectors are displayed only when relevant. For example,
806the threshold vector does not exist on x86_64 platforms. Others are
807suppressed when the system is a uniprocessor. As of this writing, only
808i386 and x86_64 platforms support the new IRQ vector displays.
809
810Of some interest is the introduction of the /proc/irq directory to 2.4.
811It could be used to set IRQ to CPU affinity. This means that you can "hook" an
812IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
813irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
814prof_cpu_mask.
815
816For example::
817
818 > ls /proc/irq/
819 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
820 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
821 > ls /proc/irq/0/
822 smp_affinity
823
824smp_affinity is a bitmask, in which you can specify which CPUs can handle the
825IRQ. You can set it by doing::
826
827 > echo 1 > /proc/irq/10/smp_affinity
828
829This means that only the first CPU will handle the IRQ, but you can also echo
8305 which means that only the first and third CPU can handle the IRQ.
831
832The contents of each smp_affinity file is the same by default::
833
834 > cat /proc/irq/0/smp_affinity
835 ffffffff
836
837There is an alternate interface, smp_affinity_list which allows specifying
838a CPU range instead of a bitmask::
839
840 > cat /proc/irq/0/smp_affinity_list
841 1024-1031
842
843The default_smp_affinity mask applies to all non-active IRQs, which are the
844IRQs which have not yet been allocated/activated, and hence which lack a
845/proc/irq/[0-9]* directory.
846
847The node file on an SMP system shows the node to which the device using the IRQ
848reports itself as being attached. This hardware locality information does not
849include information about any possible driver locality preference.
850
851prof_cpu_mask specifies which CPUs are to be profiled by the system wide
852profiler. Default value is ffffffff (all CPUs if there are only 32 of them).
853
854The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
855between all the CPUs which are allowed to handle it. As usual the kernel has
856more info than you and does a better job than you, so the defaults are the
857best choice for almost everyone. [Note this applies only to those IO-APIC's
858that support "Round Robin" interrupt distribution.]
859
860There are three more important subdirectories in /proc: net, scsi, and sys.
861The general rule is that the contents, or even the existence of these
862directories, depend on your kernel configuration. If SCSI is not enabled, the
863directory scsi may not exist. The same is true with the net, which is there
864only when networking support is present in the running kernel.
865
866The slabinfo file gives information about memory usage at the slab level.
867Linux uses slab pools for memory management above page level in version 2.2.
868Commonly used objects have their own slab pool (such as network buffers,
869directory cache, and so on).
870
871::
872
873 > cat /proc/buddyinfo
874
875 Node 0, zone DMA 0 4 5 4 4 3 ...
876 Node 0, zone Normal 1 0 0 1 101 8 ...
877 Node 0, zone HighMem 2 0 0 1 1 0 ...
878
879External fragmentation is a problem under some workloads, and buddyinfo is a
880useful tool for helping diagnose these problems. Buddyinfo will give you a
881clue as to how big an area you can safely allocate, or why a previous
882allocation failed.
883
884Each column represents the number of pages of a certain order which are
885available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
886ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
887available in ZONE_NORMAL, etc...
888
889More information relevant to external fragmentation can be found in
890pagetypeinfo::
891
892 > cat /proc/pagetypeinfo
893 Page block order: 9
894 Pages per block: 512
895
896 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
897 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
898 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
899 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
900 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
901 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
902 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
903 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
904 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
905 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
906 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
907
908 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
909 Node 0, zone DMA 2 0 5 1 0
910 Node 0, zone DMA32 41 6 967 2 0
911
912Fragmentation avoidance in the kernel works by grouping pages of different
913migrate types into the same contiguous regions of memory called page blocks.
914A page block is typically the size of the default hugepage size, e.g. 2MB on
915X86-64. By keeping pages grouped based on their ability to move, the kernel
916can reclaim pages within a page block to satisfy a high-order allocation.
917
918The pagetypinfo begins with information on the size of a page block. It
919then gives the same type of information as buddyinfo except broken down
920by migrate-type and finishes with details on how many page blocks of each
921type exist.
922
923If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
924from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
925make an estimate of the likely number of huge pages that can be allocated
926at a given point in time. All the "Movable" blocks should be allocatable
927unless memory has been mlock()'d. Some of the Reclaimable blocks should
928also be allocatable although a lot of filesystem metadata may have to be
929reclaimed to achieve this.
930
931
932meminfo
933~~~~~~~
934
935Provides information about distribution and utilization of memory. This
936varies by architecture and compile options. Some of the counters reported
937here overlap. The memory reported by the non overlapping counters may not
938add up to the overall memory usage and the difference for some workloads
939can be substantial. In many cases there are other means to find out
940additional memory using subsystem specific interfaces, for instance
941/proc/net/sockstat for TCP memory allocations.
942
943The following is from a 16GB PIII, which has highmem enabled.
944You may not have all of these fields.
945
946::
947
948 > cat /proc/meminfo
949
950 MemTotal: 16344972 kB
951 MemFree: 13634064 kB
952 MemAvailable: 14836172 kB
953 Buffers: 3656 kB
954 Cached: 1195708 kB
955 SwapCached: 0 kB
956 Active: 891636 kB
957 Inactive: 1077224 kB
958 HighTotal: 15597528 kB
959 HighFree: 13629632 kB
960 LowTotal: 747444 kB
961 LowFree: 4432 kB
962 SwapTotal: 0 kB
963 SwapFree: 0 kB
964 Dirty: 968 kB
965 Writeback: 0 kB
966 AnonPages: 861800 kB
967 Mapped: 280372 kB
968 Shmem: 644 kB
969 KReclaimable: 168048 kB
970 Slab: 284364 kB
971 SReclaimable: 159856 kB
972 SUnreclaim: 124508 kB
973 PageTables: 24448 kB
974 NFS_Unstable: 0 kB
975 Bounce: 0 kB
976 WritebackTmp: 0 kB
977 CommitLimit: 7669796 kB
978 Committed_AS: 100056 kB
979 VmallocTotal: 112216 kB
980 VmallocUsed: 428 kB
981 VmallocChunk: 111088 kB
982 Percpu: 62080 kB
983 HardwareCorrupted: 0 kB
984 AnonHugePages: 49152 kB
985 ShmemHugePages: 0 kB
986 ShmemPmdMapped: 0 kB
987
988MemTotal
989 Total usable RAM (i.e. physical RAM minus a few reserved
990 bits and the kernel binary code)
991MemFree
992 The sum of LowFree+HighFree
993MemAvailable
994 An estimate of how much memory is available for starting new
995 applications, without swapping. Calculated from MemFree,
996 SReclaimable, the size of the file LRU lists, and the low
997 watermarks in each zone.
998 The estimate takes into account that the system needs some
999 page cache to function well, and that not all reclaimable
1000 slab will be reclaimable, due to items being in use. The
1001 impact of those factors will vary from system to system.
1002Buffers
1003 Relatively temporary storage for raw disk blocks
1004 shouldn't get tremendously large (20MB or so)
1005Cached
1006 in-memory cache for files read from the disk (the
1007 pagecache). Doesn't include SwapCached
1008SwapCached
1009 Memory that once was swapped out, is swapped back in but
1010 still also is in the swapfile (if memory is needed it
1011 doesn't need to be swapped out AGAIN because it is already
1012 in the swapfile. This saves I/O)
1013Active
1014 Memory that has been used more recently and usually not
1015 reclaimed unless absolutely necessary.
1016Inactive
1017 Memory which has been less recently used. It is more
1018 eligible to be reclaimed for other purposes
1019HighTotal, HighFree
1020 Highmem is all memory above ~860MB of physical memory.
1021 Highmem areas are for use by userspace programs, or
1022 for the pagecache. The kernel must use tricks to access
1023 this memory, making it slower to access than lowmem.
1024LowTotal, LowFree
1025 Lowmem is memory which can be used for everything that
1026 highmem can be used for, but it is also available for the
1027 kernel's use for its own data structures. Among many
1028 other things, it is where everything from the Slab is
1029 allocated. Bad things happen when you're out of lowmem.
1030SwapTotal
1031 total amount of swap space available
1032SwapFree
1033 Memory which has been evicted from RAM, and is temporarily
1034 on the disk
1035Dirty
1036 Memory which is waiting to get written back to the disk
1037Writeback
1038 Memory which is actively being written back to the disk
1039AnonPages
1040 Non-file backed pages mapped into userspace page tables
1041HardwareCorrupted
1042 The amount of RAM/memory in KB, the kernel identifies as
1043 corrupted.
1044AnonHugePages
1045 Non-file backed huge pages mapped into userspace page tables
1046Mapped
1047 files which have been mmaped, such as libraries
1048Shmem
1049 Total memory used by shared memory (shmem) and tmpfs
1050ShmemHugePages
1051 Memory used by shared memory (shmem) and tmpfs allocated
1052 with huge pages
1053ShmemPmdMapped
1054 Shared memory mapped into userspace with huge pages
1055KReclaimable
1056 Kernel allocations that the kernel will attempt to reclaim
1057 under memory pressure. Includes SReclaimable (below), and other
1058 direct allocations with a shrinker.
1059Slab
1060 in-kernel data structures cache
1061SReclaimable
1062 Part of Slab, that might be reclaimed, such as caches
1063SUnreclaim
1064 Part of Slab, that cannot be reclaimed on memory pressure
1065PageTables
1066 amount of memory dedicated to the lowest level of page
1067 tables.
1068NFS_Unstable
1069 Always zero. Previous counted pages which had been written to
1070 the server, but has not been committed to stable storage.
1071Bounce
1072 Memory used for block device "bounce buffers"
1073WritebackTmp
1074 Memory used by FUSE for temporary writeback buffers
1075CommitLimit
1076 Based on the overcommit ratio ('vm.overcommit_ratio'),
1077 this is the total amount of memory currently available to
1078 be allocated on the system. This limit is only adhered to
1079 if strict overcommit accounting is enabled (mode 2 in
1080 'vm.overcommit_memory').
1081
1082 The CommitLimit is calculated with the following formula::
1083
1084 CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
1085 overcommit_ratio / 100 + [total swap pages]
1086
1087 For example, on a system with 1G of physical RAM and 7G
1088 of swap with a `vm.overcommit_ratio` of 30 it would
1089 yield a CommitLimit of 7.3G.
1090
1091 For more details, see the memory overcommit documentation
1092 in vm/overcommit-accounting.
1093Committed_AS
1094 The amount of memory presently allocated on the system.
1095 The committed memory is a sum of all of the memory which
1096 has been allocated by processes, even if it has not been
1097 "used" by them as of yet. A process which malloc()'s 1G
1098 of memory, but only touches 300M of it will show up as
1099 using 1G. This 1G is memory which has been "committed" to
1100 by the VM and can be used at any time by the allocating
1101 application. With strict overcommit enabled on the system
1102 (mode 2 in 'vm.overcommit_memory'), allocations which would
1103 exceed the CommitLimit (detailed above) will not be permitted.
1104 This is useful if one needs to guarantee that processes will
1105 not fail due to lack of memory once that memory has been
1106 successfully allocated.
1107VmallocTotal
1108 total size of vmalloc memory area
1109VmallocUsed
1110 amount of vmalloc area which is used
1111VmallocChunk
1112 largest contiguous block of vmalloc area which is free
1113Percpu
1114 Memory allocated to the percpu allocator used to back percpu
1115 allocations. This stat excludes the cost of metadata.
1116
1117vmallocinfo
1118~~~~~~~~~~~
1119
1120Provides information about vmalloced/vmaped areas. One line per area,
1121containing the virtual address range of the area, size in bytes,
1122caller information of the creator, and optional information depending
1123on the kind of area:
1124
1125 ========== ===================================================
1126 pages=nr number of pages
1127 phys=addr if a physical address was specified
1128 ioremap I/O mapping (ioremap() and friends)
1129 vmalloc vmalloc() area
1130 vmap vmap()ed pages
1131 user VM_USERMAP area
1132 vpages buffer for pages pointers was vmalloced (huge area)
1133 N<node>=nr (Only on NUMA kernels)
1134 Number of pages allocated on memory node <node>
1135 ========== ===================================================
1136
1137::
1138
1139 > cat /proc/vmallocinfo
1140 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
1141 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
1142 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
1143 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
1144 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
1145 phys=7fee8000 ioremap
1146 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
1147 phys=7fee7000 ioremap
1148 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
1149 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
1150 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
1151 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
1152 pages=2 vmalloc N1=2
1153 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
1154 /0x130 [x_tables] pages=4 vmalloc N0=4
1155 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
1156 pages=14 vmalloc N2=14
1157 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
1158 pages=4 vmalloc N1=4
1159 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
1160 pages=2 vmalloc N1=2
1161 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
1162 pages=10 vmalloc N0=10
1163
1164
1165softirqs
1166~~~~~~~~
1167
1168Provides counts of softirq handlers serviced since boot time, for each CPU.
1169
1170::
1171
1172 > cat /proc/softirqs
1173 CPU0 CPU1 CPU2 CPU3
1174 HI: 0 0 0 0
1175 TIMER: 27166 27120 27097 27034
1176 NET_TX: 0 0 0 17
1177 NET_RX: 42 0 0 39
1178 BLOCK: 0 0 107 1121
1179 TASKLET: 0 0 0 290
1180 SCHED: 27035 26983 26971 26746
1181 HRTIMER: 0 0 0 0
1182 RCU: 1678 1769 2178 2250
1183
1184
11851.3 IDE devices in /proc/ide
1186----------------------------
1187
1188The subdirectory /proc/ide contains information about all IDE devices of which
1189the kernel is aware. There is one subdirectory for each IDE controller, the
1190file drivers and a link for each IDE device, pointing to the device directory
1191in the controller specific subtree.
1192
1193The file 'drivers' contains general information about the drivers used for the
1194IDE devices::
1195
1196 > cat /proc/ide/drivers
1197 ide-cdrom version 4.53
1198 ide-disk version 1.08
1199
1200More detailed information can be found in the controller specific
1201subdirectories. These are named ide0, ide1 and so on. Each of these
1202directories contains the files shown in table 1-6.
1203
1204
1205.. table:: Table 1-6: IDE controller info in /proc/ide/ide?
1206
1207 ======= =======================================
1208 File Content
1209 ======= =======================================
1210 channel IDE channel (0 or 1)
1211 config Configuration (only for PCI/IDE bridge)
1212 mate Mate name
1213 model Type/Chipset of IDE controller
1214 ======= =======================================
1215
1216Each device connected to a controller has a separate subdirectory in the
1217controllers directory. The files listed in table 1-7 are contained in these
1218directories.
1219
1220
1221.. table:: Table 1-7: IDE device information
1222
1223 ================ ==========================================
1224 File Content
1225 ================ ==========================================
1226 cache The cache
1227 capacity Capacity of the medium (in 512Byte blocks)
1228 driver driver and version
1229 geometry physical and logical geometry
1230 identify device identify block
1231 media media type
1232 model device identifier
1233 settings device setup
1234 smart_thresholds IDE disk management thresholds
1235 smart_values IDE disk management values
1236 ================ ==========================================
1237
1238The most interesting file is ``settings``. This file contains a nice
1239overview of the drive parameters::
1240
1241 # cat /proc/ide/ide0/hda/settings
1242 name value min max mode
1243 ---- ----- --- --- ----
1244 bios_cyl 526 0 65535 rw
1245 bios_head 255 0 255 rw
1246 bios_sect 63 0 63 rw
1247 breada_readahead 4 0 127 rw
1248 bswap 0 0 1 r
1249 file_readahead 72 0 2097151 rw
1250 io_32bit 0 0 3 rw
1251 keepsettings 0 0 1 rw
1252 max_kb_per_request 122 1 127 rw
1253 multcount 0 0 8 rw
1254 nice1 1 0 1 rw
1255 nowerr 0 0 1 rw
1256 pio_mode write-only 0 255 w
1257 slow 0 0 1 rw
1258 unmaskirq 0 0 1 rw
1259 using_dma 0 0 1 rw
1260
1261
12621.4 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 tcp TCP sockets
1309 udp UDP sockets
1310 unix UNIX domain sockets
1311 wireless Wireless interface data (Wavelan etc)
1312 igmp IP multicast addresses, which this host joined
1313 psched Global packet scheduler parameters.
1314 netlink List of PF_NETLINK sockets
1315 ip_mr_vifs List of multicast virtual interfaces
1316 ip_mr_cache List of multicast routing cache
1317 ============= ================================================================
1318
1319You can use this information to see which network devices are available in
1320your system and how much traffic was routed over those devices::
1321
1322 > cat /proc/net/dev
1323 Inter-|Receive |[...
1324 face |bytes packets errs drop fifo frame compressed multicast|[...
1325 lo: 908188 5596 0 0 0 0 0 0 [...
1326 ppp0:15475140 20721 410 0 0 410 0 0 [...
1327 eth0: 614530 7085 0 0 0 0 0 1 [...
1328
1329 ...] Transmit
1330 ...] bytes packets errs drop fifo colls carrier compressed
1331 ...] 908188 5596 0 0 0 0 0 0
1332 ...] 1375103 17405 0 0 0 0 0 0
1333 ...] 1703981 5535 0 0 0 3 0 0
1334
1335In addition, each Channel Bond interface has its own directory. For
1336example, the bond0 device will have a directory called /proc/net/bond0/.
1337It will contain information that is specific to that bond, such as the
1338current slaves of the bond, the link status of the slaves, and how
1339many times the slaves link has failed.
1340
13411.5 SCSI info
1342-------------
1343
1344If you have a SCSI host adapter in your system, you'll find a subdirectory
1345named after the driver for this adapter in /proc/scsi. You'll also see a list
1346of all recognized SCSI devices in /proc/scsi::
1347
1348 >cat /proc/scsi/scsi
1349 Attached devices:
1350 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1351 Vendor: IBM Model: DGHS09U Rev: 03E0
1352 Type: Direct-Access ANSI SCSI revision: 03
1353 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1354 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1355 Type: CD-ROM ANSI SCSI revision: 02
1356
1357
1358The directory named after the driver has one file for each adapter found in
1359the system. These files contain information about the controller, including
1360the used IRQ and the IO address range. The amount of information shown is
1361dependent on the adapter you use. The example shows the output for an Adaptec
1362AHA-2940 SCSI adapter::
1363
1364 > cat /proc/scsi/aic7xxx/0
1365
1366 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1367 Compile Options:
1368 TCQ Enabled By Default : Disabled
1369 AIC7XXX_PROC_STATS : Disabled
1370 AIC7XXX_RESET_DELAY : 5
1371 Adapter Configuration:
1372 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1373 Ultra Wide Controller
1374 PCI MMAPed I/O Base: 0xeb001000
1375 Adapter SEEPROM Config: SEEPROM found and used.
1376 Adaptec SCSI BIOS: Enabled
1377 IRQ: 10
1378 SCBs: Active 0, Max Active 2,
1379 Allocated 15, HW 16, Page 255
1380 Interrupts: 160328
1381 BIOS Control Word: 0x18b6
1382 Adapter Control Word: 0x005b
1383 Extended Translation: Enabled
1384 Disconnect Enable Flags: 0xffff
1385 Ultra Enable Flags: 0x0001
1386 Tag Queue Enable Flags: 0x0000
1387 Ordered Queue Tag Flags: 0x0000
1388 Default Tag Queue Depth: 8
1389 Tagged Queue By Device array for aic7xxx host instance 0:
1390 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1391 Actual queue depth per device for aic7xxx host instance 0:
1392 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1393 Statistics:
1394 (scsi0:0:0:0)
1395 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1396 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1397 Total transfers 160151 (74577 reads and 85574 writes)
1398 (scsi0:0:6:0)
1399 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1400 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1401 Total transfers 0 (0 reads and 0 writes)
1402
1403
14041.6 Parallel port info in /proc/parport
1405---------------------------------------
1406
1407The directory /proc/parport contains information about the parallel ports of
1408your system. It has one subdirectory for each port, named after the port
1409number (0,1,2,...).
1410
1411These directories contain the four files shown in Table 1-10.
1412
1413
1414.. table:: Table 1-10: Files in /proc/parport
1415
1416 ========= ====================================================================
1417 File Content
1418 ========= ====================================================================
1419 autoprobe Any IEEE-1284 device ID information that has been acquired.
1420 devices list of the device drivers using that port. A + will appear by the
1421 name of the device currently using the port (it might not appear
1422 against any).
1423 hardware Parallel port's base address, IRQ line and DMA channel.
1424 irq IRQ that parport is using for that port. This is in a separate
1425 file to allow you to alter it by writing a new value in (IRQ
1426 number or none).
1427 ========= ====================================================================
1428
14291.7 TTY info in /proc/tty
1430-------------------------
1431
1432Information about the available and actually used tty's can be found in the
1433directory /proc/tty. You'll find entries for drivers and line disciplines in
1434this directory, as shown in Table 1-11.
1435
1436
1437.. table:: Table 1-11: Files in /proc/tty
1438
1439 ============= ==============================================
1440 File Content
1441 ============= ==============================================
1442 drivers list of drivers and their usage
1443 ldiscs registered line disciplines
1444 driver/serial usage statistic and status of single tty lines
1445 ============= ==============================================
1446
1447To see which tty's are currently in use, you can simply look into the file
1448/proc/tty/drivers::
1449
1450 > cat /proc/tty/drivers
1451 pty_slave /dev/pts 136 0-255 pty:slave
1452 pty_master /dev/ptm 128 0-255 pty:master
1453 pty_slave /dev/ttyp 3 0-255 pty:slave
1454 pty_master /dev/pty 2 0-255 pty:master
1455 serial /dev/cua 5 64-67 serial:callout
1456 serial /dev/ttyS 4 64-67 serial
1457 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1458 /dev/ptmx /dev/ptmx 5 2 system
1459 /dev/console /dev/console 5 1 system:console
1460 /dev/tty /dev/tty 5 0 system:/dev/tty
1461 unknown /dev/tty 4 1-63 console
1462
1463
14641.8 Miscellaneous kernel statistics in /proc/stat
1465-------------------------------------------------
1466
1467Various pieces of information about kernel activity are available in the
1468/proc/stat file. All of the numbers reported in this file are aggregates
1469since the system first booted. For a quick look, simply cat the file::
1470
1471 > cat /proc/stat
1472 cpu 2255 34 2290 22625563 6290 127 456 0 0 0
1473 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1474 cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1475 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1476 ctxt 1990473
1477 btime 1062191376
1478 processes 2915
1479 procs_running 1
1480 procs_blocked 0
1481 softirq 183433 0 21755 12 39 1137 231 21459 2263
1482
1483The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1484lines. These numbers identify the amount of time the CPU has spent performing
1485different kinds of work. Time units are in USER_HZ (typically hundredths of a
1486second). The meanings of the columns are as follows, from left to right:
1487
1488- user: normal processes executing in user mode
1489- nice: niced processes executing in user mode
1490- system: processes executing in kernel mode
1491- idle: twiddling thumbs
1492- iowait: In a word, iowait stands for waiting for I/O to complete. But there
1493 are several problems:
1494
1495 1. CPU will not wait for I/O to complete, iowait is the time that a task is
1496 waiting for I/O to complete. When CPU goes into idle state for
1497 outstanding task I/O, another task will be scheduled on this CPU.
1498 2. In a multi-core CPU, the task waiting for I/O to complete is not running
1499 on any CPU, so the iowait of each CPU is difficult to calculate.
1500 3. The value of iowait field in /proc/stat will decrease in certain
1501 conditions.
1502
1503 So, the iowait is not reliable by reading from /proc/stat.
1504- irq: servicing interrupts
1505- softirq: servicing softirqs
1506- steal: involuntary wait
1507- guest: running a normal guest
1508- guest_nice: running a niced guest
1509
1510The "intr" line gives counts of interrupts serviced since boot time, for each
1511of the possible system interrupts. The first column is the total of all
1512interrupts serviced including unnumbered architecture specific interrupts;
1513each subsequent column is the total for that particular numbered interrupt.
1514Unnumbered interrupts are not shown, only summed into the total.
1515
1516The "ctxt" line gives the total number of context switches across all CPUs.
1517
1518The "btime" line gives the time at which the system booted, in seconds since
1519the Unix epoch.
1520
1521The "processes" line gives the number of processes and threads created, which
1522includes (but is not limited to) those created by calls to the fork() and
1523clone() system calls.
1524
1525The "procs_running" line gives the total number of threads that are
1526running or ready to run (i.e., the total number of runnable threads).
1527
1528The "procs_blocked" line gives the number of processes currently blocked,
1529waiting for I/O to complete.
1530
1531The "softirq" line gives counts of softirqs serviced since boot time, for each
1532of the possible system softirqs. The first column is the total of all
1533softirqs serviced; each subsequent column is the total for that particular
1534softirq.
1535
1536
15371.9 Ext4 file system parameters
1538-------------------------------
1539
1540Information about mounted ext4 file systems can be found in
1541/proc/fs/ext4. Each mounted filesystem will have a directory in
1542/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1543/proc/fs/ext4/dm-0). The files in each per-device directory are shown
1544in Table 1-12, below.
1545
1546.. table:: Table 1-12: Files in /proc/fs/ext4/<devname>
1547
1548 ============== ==========================================================
1549 File Content
1550 mb_groups details of multiblock allocator buddy cache of free blocks
1551 ============== ==========================================================
1552
15531.10 /proc/consoles
1554-------------------
1555Shows registered system console lines.
1556
1557To see which character device lines are currently used for the system console
1558/dev/console, you may simply look into the file /proc/consoles::
1559
1560 > cat /proc/consoles
1561 tty0 -WU (ECp) 4:7
1562 ttyS0 -W- (Ep) 4:64
1563
1564The columns are:
1565
1566+--------------------+-------------------------------------------------------+
1567| device | name of the device |
1568+====================+=======================================================+
1569| operations | * R = can do read operations |
1570| | * W = can do write operations |
1571| | * U = can do unblank |
1572+--------------------+-------------------------------------------------------+
1573| flags | * E = it is enabled |
1574| | * C = it is preferred console |
1575| | * B = it is primary boot console |
1576| | * p = it is used for printk buffer |
1577| | * b = it is not a TTY but a Braille device |
1578| | * a = it is safe to use when cpu is offline |
1579+--------------------+-------------------------------------------------------+
1580| major:minor | major and minor number of the device separated by a |
1581| | colon |
1582+--------------------+-------------------------------------------------------+
1583
1584Summary
1585-------
1586
1587The /proc file system serves information about the running system. It not only
1588allows access to process data but also allows you to request the kernel status
1589by reading files in the hierarchy.
1590
1591The directory structure of /proc reflects the types of information and makes
1592it easy, if not obvious, where to look for specific data.
1593
1594Chapter 2: Modifying System Parameters
1595======================================
1596
1597In This Chapter
1598---------------
1599
1600* Modifying kernel parameters by writing into files found in /proc/sys
1601* Exploring the files which modify certain parameters
1602* Review of the /proc/sys file tree
1603
1604------------------------------------------------------------------------------
1605
1606A very interesting part of /proc is the directory /proc/sys. This is not only
1607a source of information, it also allows you to change parameters within the
1608kernel. Be very careful when attempting this. You can optimize your system,
1609but you can also cause it to crash. Never alter kernel parameters on a
1610production system. Set up a development machine and test to make sure that
1611everything works the way you want it to. You may have no alternative but to
1612reboot the machine once an error has been made.
1613
1614To change a value, simply echo the new value into the file.
1615You need to be root to do this. You can create your own boot script
1616to perform this every time your system boots.
1617
1618The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1619general things in the operation of the Linux kernel. Since some of the files
1620can inadvertently disrupt your system, it is advisable to read both
1621documentation and source before actually making adjustments. In any case, be
1622very careful when writing to any of these files. The entries in /proc may
1623change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1624review the kernel documentation in the directory /usr/src/linux/Documentation.
1625This chapter is heavily based on the documentation included in the pre 2.2
1626kernels, and became part of it in version 2.2.1 of the Linux kernel.
1627
1628Please see: Documentation/admin-guide/sysctl/ directory for descriptions of these
1629entries.
1630
1631Summary
1632-------
1633
1634Certain aspects of kernel behavior can be modified at runtime, without the
1635need to recompile the kernel, or even to reboot the system. The files in the
1636/proc/sys tree can not only be read, but also modified. You can use the echo
1637command to write value into these files, thereby changing the default settings
1638of the kernel.
1639
1640
1641Chapter 3: Per-process Parameters
1642=================================
1643
16443.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1645--------------------------------------------------------------------------------
1646
1647These files can be used to adjust the badness heuristic used to select which
1648process gets killed in out of memory (oom) conditions.
1649
1650The badness heuristic assigns a value to each candidate task ranging from 0
1651(never kill) to 1000 (always kill) to determine which process is targeted. The
1652units are roughly a proportion along that range of allowed memory the process
1653may allocate from based on an estimation of its current memory and swap use.
1654For example, if a task is using all allowed memory, its badness score will be
16551000. If it is using half of its allowed memory, its score will be 500.
1656
1657The amount of "allowed" memory depends on the context in which the oom killer
1658was called. If it is due to the memory assigned to the allocating task's cpuset
1659being exhausted, the allowed memory represents the set of mems assigned to that
1660cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1661memory represents the set of mempolicy nodes. If it is due to a memory
1662limit (or swap limit) being reached, the allowed memory is that configured
1663limit. Finally, if it is due to the entire system being out of memory, the
1664allowed memory represents all allocatable resources.
1665
1666The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1667is used to determine which task to kill. Acceptable values range from -1000
1668(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1669polarize the preference for oom killing either by always preferring a certain
1670task or completely disabling it. The lowest possible value, -1000, is
1671equivalent to disabling oom killing entirely for that task since it will always
1672report a badness score of 0.
1673
1674Consequently, it is very simple for userspace to define the amount of memory to
1675consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1676example, is roughly equivalent to allowing the remainder of tasks sharing the
1677same system, cpuset, mempolicy, or memory controller resources to use at least
167850% more memory. A value of -500, on the other hand, would be roughly
1679equivalent to discounting 50% of the task's allowed memory from being considered
1680as scoring against the task.
1681
1682For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1683be used to tune the badness score. Its acceptable values range from -16
1684(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1685(OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1686scaled linearly with /proc/<pid>/oom_score_adj.
1687
1688The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1689value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1690requires CAP_SYS_RESOURCE.
1691
1692
16933.2 /proc/<pid>/oom_score - Display current oom-killer score
1694-------------------------------------------------------------
1695
1696This file can be used to check the current score used by the oom-killer for
1697any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1698process should be killed in an out-of-memory situation.
1699
1700Please note that the exported value includes oom_score_adj so it is
1701effectively in range [0,2000].
1702
1703
17043.3 /proc/<pid>/io - Display the IO accounting fields
1705-------------------------------------------------------
1706
1707This file contains IO statistics for each running process.
1708
1709Example
1710~~~~~~~
1711
1712::
1713
1714 test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1715 [1] 3828
1716
1717 test:/tmp # cat /proc/3828/io
1718 rchar: 323934931
1719 wchar: 323929600
1720 syscr: 632687
1721 syscw: 632675
1722 read_bytes: 0
1723 write_bytes: 323932160
1724 cancelled_write_bytes: 0
1725
1726
1727Description
1728~~~~~~~~~~~
1729
1730rchar
1731^^^^^
1732
1733I/O counter: chars read
1734The number of bytes which this task has caused to be read from storage. This
1735is simply the sum of bytes which this process passed to read() and pread().
1736It includes things like tty IO and it is unaffected by whether or not actual
1737physical disk IO was required (the read might have been satisfied from
1738pagecache).
1739
1740
1741wchar
1742^^^^^
1743
1744I/O counter: chars written
1745The number of bytes which this task has caused, or shall cause to be written
1746to disk. Similar caveats apply here as with rchar.
1747
1748
1749syscr
1750^^^^^
1751
1752I/O counter: read syscalls
1753Attempt to count the number of read I/O operations, i.e. syscalls like read()
1754and pread().
1755
1756
1757syscw
1758^^^^^
1759
1760I/O counter: write syscalls
1761Attempt to count the number of write I/O operations, i.e. syscalls like
1762write() and pwrite().
1763
1764
1765read_bytes
1766^^^^^^^^^^
1767
1768I/O counter: bytes read
1769Attempt to count the number of bytes which this process really did cause to
1770be fetched from the storage layer. Done at the submit_bio() level, so it is
1771accurate for block-backed filesystems. <please add status regarding NFS and
1772CIFS at a later time>
1773
1774
1775write_bytes
1776^^^^^^^^^^^
1777
1778I/O counter: bytes written
1779Attempt to count the number of bytes which this process caused to be sent to
1780the storage layer. This is done at page-dirtying time.
1781
1782
1783cancelled_write_bytes
1784^^^^^^^^^^^^^^^^^^^^^
1785
1786The big inaccuracy here is truncate. If a process writes 1MB to a file and
1787then deletes the file, it will in fact perform no writeout. But it will have
1788been accounted as having caused 1MB of write.
1789In other words: The number of bytes which this process caused to not happen,
1790by truncating pagecache. A task can cause "negative" IO too. If this task
1791truncates some dirty pagecache, some IO which another task has been accounted
1792for (in its write_bytes) will not be happening. We _could_ just subtract that
1793from the truncating task's write_bytes, but there is information loss in doing
1794that.
1795
1796
1797.. Note::
1798
1799 At its current implementation state, this is a bit racy on 32-bit machines:
1800 if process A reads process B's /proc/pid/io while process B is updating one
1801 of those 64-bit counters, process A could see an intermediate result.
1802
1803
1804More information about this can be found within the taskstats documentation in
1805Documentation/accounting.
1806
18073.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1808---------------------------------------------------------------
1809When a process is dumped, all anonymous memory is written to a core file as
1810long as the size of the core file isn't limited. But sometimes we don't want
1811to dump some memory segments, for example, huge shared memory or DAX.
1812Conversely, sometimes we want to save file-backed memory segments into a core
1813file, not only the individual files.
1814
1815/proc/<pid>/coredump_filter allows you to customize which memory segments
1816will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1817of memory types. If a bit of the bitmask is set, memory segments of the
1818corresponding memory type are dumped, otherwise they are not dumped.
1819
1820The following 9 memory types are supported:
1821
1822 - (bit 0) anonymous private memory
1823 - (bit 1) anonymous shared memory
1824 - (bit 2) file-backed private memory
1825 - (bit 3) file-backed shared memory
1826 - (bit 4) ELF header pages in file-backed private memory areas (it is
1827 effective only if the bit 2 is cleared)
1828 - (bit 5) hugetlb private memory
1829 - (bit 6) hugetlb shared memory
1830 - (bit 7) DAX private memory
1831 - (bit 8) DAX shared memory
1832
1833 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1834 are always dumped regardless of the bitmask status.
1835
1836 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
1837 only affected by bit 5-6, and DAX is only affected by bits 7-8.
1838
1839The default value of coredump_filter is 0x33; this means all anonymous memory
1840segments, ELF header pages and hugetlb private memory are dumped.
1841
1842If you don't want to dump all shared memory segments attached to pid 1234,
1843write 0x31 to the process's proc file::
1844
1845 $ echo 0x31 > /proc/1234/coredump_filter
1846
1847When a new process is created, the process inherits the bitmask status from its
1848parent. It is useful to set up coredump_filter before the program runs.
1849For example::
1850
1851 $ echo 0x7 > /proc/self/coredump_filter
1852 $ ./some_program
1853
18543.5 /proc/<pid>/mountinfo - Information about mounts
1855--------------------------------------------------------
1856
1857This file contains lines of the form::
1858
1859 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1860 (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1861
1862 (1) mount ID: unique identifier of the mount (may be reused after umount)
1863 (2) parent ID: ID of parent (or of self for the top of the mount tree)
1864 (3) major:minor: value of st_dev for files on filesystem
1865 (4) root: root of the mount within the filesystem
1866 (5) mount point: mount point relative to the process's root
1867 (6) mount options: per mount options
1868 (7) optional fields: zero or more fields of the form "tag[:value]"
1869 (8) separator: marks the end of the optional fields
1870 (9) filesystem type: name of filesystem of the form "type[.subtype]"
1871 (10) mount source: filesystem specific information or "none"
1872 (11) super options: per super block options
1873
1874Parsers should ignore all unrecognised optional fields. Currently the
1875possible optional fields are:
1876
1877================ ==============================================================
1878shared:X mount is shared in peer group X
1879master:X mount is slave to peer group X
1880propagate_from:X mount is slave and receives propagation from peer group X [#]_
1881unbindable mount is unbindable
1882================ ==============================================================
1883
1884.. [#] X is the closest dominant peer group under the process's root. If
1885 X is the immediate master of the mount, or if there's no dominant peer
1886 group under the same root, then only the "master:X" field is present
1887 and not the "propagate_from:X" field.
1888
1889For more information on mount propagation see:
1890
1891 Documentation/filesystems/sharedsubtree.rst
1892
1893
18943.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1895--------------------------------------------------------
1896These files provide a method to access a task's comm value. It also allows for
1897a task to set its own or one of its thread siblings comm value. The comm value
1898is limited in size compared to the cmdline value, so writing anything longer
1899then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1900comm value.
1901
1902
19033.7 /proc/<pid>/task/<tid>/children - Information about task children
1904-------------------------------------------------------------------------
1905This file provides a fast way to retrieve first level children pids
1906of a task pointed by <pid>/<tid> pair. The format is a space separated
1907stream of pids.
1908
1909Note the "first level" here -- if a child has its own children they will
1910not be listed here; one needs to read /proc/<children-pid>/task/<tid>/children
1911to obtain the descendants.
1912
1913Since this interface is intended to be fast and cheap it doesn't
1914guarantee to provide precise results and some children might be
1915skipped, especially if they've exited right after we printed their
1916pids, so one needs to either stop or freeze processes being inspected
1917if precise results are needed.
1918
1919
19203.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
1921---------------------------------------------------------------
1922This file provides information associated with an opened file. The regular
1923files have at least four fields -- 'pos', 'flags', 'mnt_id' and 'ino'.
1924The 'pos' represents the current offset of the opened file in decimal
1925form [see lseek(2) for details], 'flags' denotes the octal O_xxx mask the
1926file has been created with [see open(2) for details] and 'mnt_id' represents
1927mount ID of the file system containing the opened file [see 3.5
1928/proc/<pid>/mountinfo for details]. 'ino' represents the inode number of
1929the file.
1930
1931A typical output is::
1932
1933 pos: 0
1934 flags: 0100002
1935 mnt_id: 19
1936 ino: 63107
1937
1938All locks associated with a file descriptor are shown in its fdinfo too::
1939
1940 lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF
1941
1942The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1943pair provide additional information particular to the objects they represent.
1944
1945Eventfd files
1946~~~~~~~~~~~~~
1947
1948::
1949
1950 pos: 0
1951 flags: 04002
1952 mnt_id: 9
1953 ino: 63107
1954 eventfd-count: 5a
1955
1956where 'eventfd-count' is hex value of a counter.
1957
1958Signalfd files
1959~~~~~~~~~~~~~~
1960
1961::
1962
1963 pos: 0
1964 flags: 04002
1965 mnt_id: 9
1966 ino: 63107
1967 sigmask: 0000000000000200
1968
1969where 'sigmask' is hex value of the signal mask associated
1970with a file.
1971
1972Epoll files
1973~~~~~~~~~~~
1974
1975::
1976
1977 pos: 0
1978 flags: 02
1979 mnt_id: 9
1980 ino: 63107
1981 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7
1982
1983where 'tfd' is a target file descriptor number in decimal form,
1984'events' is events mask being watched and the 'data' is data
1985associated with a target [see epoll(7) for more details].
1986
1987The 'pos' is current offset of the target file in decimal form
1988[see lseek(2)], 'ino' and 'sdev' are inode and device numbers
1989where target file resides, all in hex format.
1990
1991Fsnotify files
1992~~~~~~~~~~~~~~
1993For inotify files the format is the following::
1994
1995 pos: 0
1996 flags: 02000000
1997 mnt_id: 9
1998 ino: 63107
1999 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
2000
2001where 'wd' is a watch descriptor in decimal form, i.e. a target file
2002descriptor number, 'ino' and 'sdev' are inode and device where the
2003target file resides and the 'mask' is the mask of events, all in hex
2004form [see inotify(7) for more details].
2005
2006If the kernel was built with exportfs support, the path to the target
2007file is encoded as a file handle. The file handle is provided by three
2008fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
2009format.
2010
2011If the kernel is built without exportfs support the file handle won't be
2012printed out.
2013
2014If there is no inotify mark attached yet the 'inotify' line will be omitted.
2015
2016For fanotify files the format is::
2017
2018 pos: 0
2019 flags: 02
2020 mnt_id: 9
2021 ino: 63107
2022 fanotify flags:10 event-flags:0
2023 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
2024 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
2025
2026where fanotify 'flags' and 'event-flags' are values used in fanotify_init
2027call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
2028flags associated with mark which are tracked separately from events
2029mask. 'ino' and 'sdev' are target inode and device, 'mask' is the events
2030mask and 'ignored_mask' is the mask of events which are to be ignored.
2031All are in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
2032provide information about flags and mask used in fanotify_mark
2033call [see fsnotify manpage for details].
2034
2035While the first three lines are mandatory and always printed, the rest is
2036optional and may be omitted if no marks created yet.
2037
2038Timerfd files
2039~~~~~~~~~~~~~
2040
2041::
2042
2043 pos: 0
2044 flags: 02
2045 mnt_id: 9
2046 ino: 63107
2047 clockid: 0
2048 ticks: 0
2049 settime flags: 01
2050 it_value: (0, 49406829)
2051 it_interval: (1, 0)
2052
2053where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
2054that have occurred [see timerfd_create(2) for details]. 'settime flags' are
2055flags in octal form been used to setup the timer [see timerfd_settime(2) for
2056details]. 'it_value' is remaining time until the timer expiration.
2057'it_interval' is the interval for the timer. Note the timer might be set up
2058with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
2059still exhibits timer's remaining time.
2060
2061DMA Buffer files
2062~~~~~~~~~~~~~~~~
2063
2064::
2065
2066 pos: 0
2067 flags: 04002
2068 mnt_id: 9
2069 ino: 63107
2070 size: 32768
2071 count: 2
2072 exp_name: system-heap
2073
2074where 'size' is the size of the DMA buffer in bytes. 'count' is the file count of
2075the DMA buffer file. 'exp_name' is the name of the DMA buffer exporter.
2076
20773.9 /proc/<pid>/map_files - Information about memory mapped files
2078---------------------------------------------------------------------
2079This directory contains symbolic links which represent memory mapped files
2080the process is maintaining. Example output::
2081
2082 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
2083 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
2084 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
2085 | ...
2086 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
2087 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
2088
2089The name of a link represents the virtual memory bounds of a mapping, i.e.
2090vm_area_struct::vm_start-vm_area_struct::vm_end.
2091
2092The main purpose of the map_files is to retrieve a set of memory mapped
2093files in a fast way instead of parsing /proc/<pid>/maps or
2094/proc/<pid>/smaps, both of which contain many more records. At the same
2095time one can open(2) mappings from the listings of two processes and
2096comparing their inode numbers to figure out which anonymous memory areas
2097are actually shared.
2098
20993.10 /proc/<pid>/timerslack_ns - Task timerslack value
2100---------------------------------------------------------
2101This file provides the value of the task's timerslack value in nanoseconds.
2102This value specifies an amount of time that normal timers may be deferred
2103in order to coalesce timers and avoid unnecessary wakeups.
2104
2105This allows a task's interactivity vs power consumption tradeoff to be
2106adjusted.
2107
2108Writing 0 to the file will set the task's timerslack to the default value.
2109
2110Valid values are from 0 - ULLONG_MAX
2111
2112An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
2113permissions on the task specified to change its timerslack_ns value.
2114
21153.11 /proc/<pid>/patch_state - Livepatch patch operation state
2116-----------------------------------------------------------------
2117When CONFIG_LIVEPATCH is enabled, this file displays the value of the
2118patch state for the task.
2119
2120A value of '-1' indicates that no patch is in transition.
2121
2122A value of '0' indicates that a patch is in transition and the task is
2123unpatched. If the patch is being enabled, then the task hasn't been
2124patched yet. If the patch is being disabled, then the task has already
2125been unpatched.
2126
2127A value of '1' indicates that a patch is in transition and the task is
2128patched. If the patch is being enabled, then the task has already been
2129patched. If the patch is being disabled, then the task hasn't been
2130unpatched yet.
2131
21323.12 /proc/<pid>/arch_status - task architecture specific status
2133-------------------------------------------------------------------
2134When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the
2135architecture specific status of the task.
2136
2137Example
2138~~~~~~~
2139
2140::
2141
2142 $ cat /proc/6753/arch_status
2143 AVX512_elapsed_ms: 8
2144
2145Description
2146~~~~~~~~~~~
2147
2148x86 specific entries
2149~~~~~~~~~~~~~~~~~~~~~
2150
2151AVX512_elapsed_ms
2152^^^^^^^^^^^^^^^^^^
2153
2154 If AVX512 is supported on the machine, this entry shows the milliseconds
2155 elapsed since the last time AVX512 usage was recorded. The recording
2156 happens on a best effort basis when a task is scheduled out. This means
2157 that the value depends on two factors:
2158
2159 1) The time which the task spent on the CPU without being scheduled
2160 out. With CPU isolation and a single runnable task this can take
2161 several seconds.
2162
2163 2) The time since the task was scheduled out last. Depending on the
2164 reason for being scheduled out (time slice exhausted, syscall ...)
2165 this can be arbitrary long time.
2166
2167 As a consequence the value cannot be considered precise and authoritative
2168 information. The application which uses this information has to be aware
2169 of the overall scenario on the system in order to determine whether a
2170 task is a real AVX512 user or not. Precise information can be obtained
2171 with performance counters.
2172
2173 A special value of '-1' indicates that no AVX512 usage was recorded, thus
2174 the task is unlikely an AVX512 user, but depends on the workload and the
2175 scheduling scenario, it also could be a false negative mentioned above.
2176
2177Chapter 4: Configuring procfs
2178=============================
2179
21804.1 Mount options
2181---------------------
2182
2183The following mount options are supported:
2184
2185 ========= ========================================================
2186 hidepid= Set /proc/<pid>/ access mode.
2187 gid= Set the group authorized to learn processes information.
2188 subset= Show only the specified subset of procfs.
2189 ========= ========================================================
2190
2191hidepid=off or hidepid=0 means classic mode - everybody may access all
2192/proc/<pid>/ directories (default).
2193
2194hidepid=noaccess or hidepid=1 means users may not access any /proc/<pid>/
2195directories but their own. Sensitive files like cmdline, sched*, status are now
2196protected against other users. This makes it impossible to learn whether any
2197user runs specific program (given the program doesn't reveal itself by its
2198behaviour). As an additional bonus, as /proc/<pid>/cmdline is unaccessible for
2199other users, poorly written programs passing sensitive information via program
2200arguments are now protected against local eavesdroppers.
2201
2202hidepid=invisible or hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be
2203fully invisible to other users. It doesn't mean that it hides a fact whether a
2204process with a specific pid value exists (it can be learned by other means, e.g.
2205by "kill -0 $PID"), but it hides process' uid and gid, which may be learned by
2206stat()'ing /proc/<pid>/ otherwise. It greatly complicates an intruder's task of
2207gathering information about running processes, whether some daemon runs with
2208elevated privileges, whether other user runs some sensitive program, whether
2209other users run any program at all, etc.
2210
2211hidepid=ptraceable or hidepid=4 means that procfs should only contain
2212/proc/<pid>/ directories that the caller can ptrace.
2213
2214gid= defines a group authorized to learn processes information otherwise
2215prohibited by hidepid=. If you use some daemon like identd which needs to learn
2216information about processes information, just add identd to this group.
2217
2218subset=pid hides all top level files and directories in the procfs that
2219are not related to tasks.
2220
2221Chapter 5: Filesystem behavior
2222==============================
2223
2224Originally, before the advent of pid namepsace, procfs was a global file
2225system. It means that there was only one procfs instance in the system.
2226
2227When pid namespace was added, a separate procfs instance was mounted in
2228each pid namespace. So, procfs mount options are global among all
2229mountpoints within the same namespace::
2230
2231 # grep ^proc /proc/mounts
2232 proc /proc proc rw,relatime,hidepid=2 0 0
2233
2234 # strace -e mount mount -o hidepid=1 -t proc proc /tmp/proc
2235 mount("proc", "/tmp/proc", "proc", 0, "hidepid=1") = 0
2236 +++ exited with 0 +++
2237
2238 # grep ^proc /proc/mounts
2239 proc /proc proc rw,relatime,hidepid=2 0 0
2240 proc /tmp/proc proc rw,relatime,hidepid=2 0 0
2241
2242and only after remounting procfs mount options will change at all
2243mountpoints::
2244
2245 # mount -o remount,hidepid=1 -t proc proc /tmp/proc
2246
2247 # grep ^proc /proc/mounts
2248 proc /proc proc rw,relatime,hidepid=1 0 0
2249 proc /tmp/proc proc rw,relatime,hidepid=1 0 0
2250
2251This behavior is different from the behavior of other filesystems.
2252
2253The new procfs behavior is more like other filesystems. Each procfs mount
2254creates a new procfs instance. Mount options affect own procfs instance.
2255It means that it became possible to have several procfs instances
2256displaying tasks with different filtering options in one pid namespace::
2257
2258 # mount -o hidepid=invisible -t proc proc /proc
2259 # mount -o hidepid=noaccess -t proc proc /tmp/proc
2260 # grep ^proc /proc/mounts
2261 proc /proc proc rw,relatime,hidepid=invisible 0 0
2262 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
88http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/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 VmPeak: 5004 kB
183 VmSize: 5004 kB
184 VmLck: 0 kB
185 VmHWM: 476 kB
186 VmRSS: 476 kB
187 RssAnon: 352 kB
188 RssFile: 120 kB
189 RssShmem: 4 kB
190 VmData: 156 kB
191 VmStk: 88 kB
192 VmExe: 68 kB
193 VmLib: 1412 kB
194 VmPTE: 20 kb
195 VmSwap: 0 kB
196 HugetlbPages: 0 kB
197 CoreDumping: 0
198 THP_enabled: 1
199 Threads: 1
200 SigQ: 0/28578
201 SigPnd: 0000000000000000
202 ShdPnd: 0000000000000000
203 SigBlk: 0000000000000000
204 SigIgn: 0000000000000000
205 SigCgt: 0000000000000000
206 CapInh: 00000000fffffeff
207 CapPrm: 0000000000000000
208 CapEff: 0000000000000000
209 CapBnd: ffffffffffffffff
210 CapAmb: 0000000000000000
211 NoNewPrivs: 0
212 Seccomp: 0
213 Speculation_Store_Bypass: thread vulnerable
214 SpeculationIndirectBranch: conditional enabled
215 voluntary_ctxt_switches: 0
216 nonvoluntary_ctxt_switches: 1
217
218This shows you nearly the same information you would get if you viewed it with
219the ps command. In fact, ps uses the proc file system to obtain its
220information. But you get a more detailed view of the process by reading the
221file /proc/PID/status. It fields are described in table 1-2.
222
223The statm file contains more detailed information about the process
224memory usage. Its seven fields are explained in Table 1-3. The stat file
225contains detailed information about the process itself. Its fields are
226explained in Table 1-4.
227
228(for SMP CONFIG users)
229
230For making accounting scalable, RSS related information are handled in an
231asynchronous manner and the value may not be very precise. To see a precise
232snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
233It's slow but very precise.
234
235.. table:: Table 1-2: Contents of the status files (as of 4.19)
236
237 ========================== ===================================================
238 Field Content
239 ========================== ===================================================
240 Name filename of the executable
241 Umask file mode creation mask
242 State state (R is running, S is sleeping, D is sleeping
243 in an uninterruptible wait, Z is zombie,
244 T is traced or stopped)
245 Tgid thread group ID
246 Ngid NUMA group ID (0 if none)
247 Pid process id
248 PPid process id of the parent process
249 TracerPid PID of process tracing this process (0 if not, or
250 the tracer is outside of the current pid namespace)
251 Uid Real, effective, saved set, and file system UIDs
252 Gid Real, effective, saved set, and file system GIDs
253 FDSize number of file descriptor slots currently allocated
254 Groups supplementary group list
255 NStgid descendant namespace thread group ID hierarchy
256 NSpid descendant namespace process ID hierarchy
257 NSpgid descendant namespace process group ID hierarchy
258 NSsid descendant namespace session ID hierarchy
259 VmPeak peak virtual memory size
260 VmSize total program size
261 VmLck locked memory size
262 VmPin pinned memory size
263 VmHWM peak resident set size ("high water mark")
264 VmRSS size of memory portions. It contains the three
265 following parts
266 (VmRSS = RssAnon + RssFile + RssShmem)
267 RssAnon size of resident anonymous memory
268 RssFile size of resident file mappings
269 RssShmem size of resident shmem memory (includes SysV shm,
270 mapping of tmpfs and shared anonymous mappings)
271 VmData size of private data segments
272 VmStk size of stack segments
273 VmExe size of text segment
274 VmLib size of shared library code
275 VmPTE size of page table entries
276 VmSwap amount of swap used by anonymous private data
277 (shmem swap usage is not included)
278 HugetlbPages size of hugetlb memory portions
279 CoreDumping process's memory is currently being dumped
280 (killing the process may lead to a corrupted core)
281 THP_enabled process is allowed to use THP (returns 0 when
282 PR_SET_THP_DISABLE is set on the process
283 Threads number of threads
284 SigQ number of signals queued/max. number for queue
285 SigPnd bitmap of pending signals for the thread
286 ShdPnd bitmap of shared pending signals for the process
287 SigBlk bitmap of blocked signals
288 SigIgn bitmap of ignored signals
289 SigCgt bitmap of caught signals
290 CapInh bitmap of inheritable capabilities
291 CapPrm bitmap of permitted capabilities
292 CapEff bitmap of effective capabilities
293 CapBnd bitmap of capabilities bounding set
294 CapAmb bitmap of ambient capabilities
295 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
296 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
297 Speculation_Store_Bypass speculative store bypass mitigation status
298 SpeculationIndirectBranch indirect branch speculation mode
299 Cpus_allowed mask of CPUs on which this process may run
300 Cpus_allowed_list Same as previous, but in "list format"
301 Mems_allowed mask of memory nodes allowed to this process
302 Mems_allowed_list Same as previous, but in "list format"
303 voluntary_ctxt_switches number of voluntary context switches
304 nonvoluntary_ctxt_switches number of non voluntary context switches
305 ========================== ===================================================
306
307
308.. table:: Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
309
310 ======== =============================== ==============================
311 Field Content
312 ======== =============================== ==============================
313 size total program size (pages) (same as VmSize in status)
314 resident size of memory portions (pages) (same as VmRSS in status)
315 shared number of pages that are shared (i.e. backed by a file, same
316 as RssFile+RssShmem in status)
317 trs number of pages that are 'code' (not including libs; broken,
318 includes data segment)
319 lrs number of pages of library (always 0 on 2.6)
320 drs number of pages of data/stack (including libs; broken,
321 includes library text)
322 dt number of dirty pages (always 0 on 2.6)
323 ======== =============================== ==============================
324
325
326.. table:: Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
327
328 ============= ===============================================================
329 Field Content
330 ============= ===============================================================
331 pid process id
332 tcomm filename of the executable
333 state state (R is running, S is sleeping, D is sleeping in an
334 uninterruptible wait, Z is zombie, T is traced or stopped)
335 ppid process id of the parent process
336 pgrp pgrp of the process
337 sid session id
338 tty_nr tty the process uses
339 tty_pgrp pgrp of the tty
340 flags task flags
341 min_flt number of minor faults
342 cmin_flt number of minor faults with child's
343 maj_flt number of major faults
344 cmaj_flt number of major faults with child's
345 utime user mode jiffies
346 stime kernel mode jiffies
347 cutime user mode jiffies with child's
348 cstime kernel mode jiffies with child's
349 priority priority level
350 nice nice level
351 num_threads number of threads
352 it_real_value (obsolete, always 0)
353 start_time time the process started after system boot
354 vsize virtual memory size
355 rss resident set memory size
356 rsslim current limit in bytes on the rss
357 start_code address above which program text can run
358 end_code address below which program text can run
359 start_stack address of the start of the main process stack
360 esp current value of ESP
361 eip current value of EIP
362 pending bitmap of pending signals
363 blocked bitmap of blocked signals
364 sigign bitmap of ignored signals
365 sigcatch bitmap of caught signals
366 0 (place holder, used to be the wchan address,
367 use /proc/PID/wchan instead)
368 0 (place holder)
369 0 (place holder)
370 exit_signal signal to send to parent thread on exit
371 task_cpu which CPU the task is scheduled on
372 rt_priority realtime priority
373 policy scheduling policy (man sched_setscheduler)
374 blkio_ticks time spent waiting for block IO
375 gtime guest time of the task in jiffies
376 cgtime guest time of the task children in jiffies
377 start_data address above which program data+bss is placed
378 end_data address below which program data+bss is placed
379 start_brk address above which program heap can be expanded with brk()
380 arg_start address above which program command line is placed
381 arg_end address below which program command line is placed
382 env_start address above which program environment is placed
383 env_end address below which program environment is placed
384 exit_code the thread's exit_code in the form reported by the waitpid
385 system call
386 ============= ===============================================================
387
388The /proc/PID/maps file contains the currently mapped memory regions and
389their access permissions.
390
391The format is::
392
393 address perms offset dev inode pathname
394
395 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test
396 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
397 0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
398 a7cb1000-a7cb2000 ---p 00000000 00:00 0
399 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
400 a7eb2000-a7eb3000 ---p 00000000 00:00 0
401 a7eb3000-a7ed5000 rw-p 00000000 00:00 0
402 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
403 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
404 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
405 a800b000-a800e000 rw-p 00000000 00:00 0
406 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
407 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
408 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
409 a8024000-a8027000 rw-p 00000000 00:00 0
410 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
411 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
412 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
413 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
414 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
415
416where "address" is the address space in the process that it occupies, "perms"
417is a set of permissions::
418
419 r = read
420 w = write
421 x = execute
422 s = shared
423 p = private (copy on write)
424
425"offset" is the offset into the mapping, "dev" is the device (major:minor), and
426"inode" is the inode on that device. 0 indicates that no inode is associated
427with the memory region, as the case would be with BSS (uninitialized data).
428The "pathname" shows the name associated file for this mapping. If the mapping
429is not associated with a file:
430
431 =================== ===========================================
432 [heap] the heap of the program
433 [stack] the stack of the main process
434 [vdso] the "virtual dynamic shared object",
435 the kernel system call handler
436 [anon:<name>] a private anonymous mapping that has been
437 named by userspace
438 [anon_shmem:<name>] an anonymous shared memory mapping that has
439 been named by userspace
440 =================== ===========================================
441
442 or if empty, the mapping is anonymous.
443
444The /proc/PID/smaps is an extension based on maps, showing the memory
445consumption for each of the process's mappings. For each mapping (aka Virtual
446Memory Area, or VMA) there is a series of lines such as the following::
447
448 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
449
450 Size: 1084 kB
451 KernelPageSize: 4 kB
452 MMUPageSize: 4 kB
453 Rss: 892 kB
454 Pss: 374 kB
455 Pss_Dirty: 0 kB
456 Shared_Clean: 892 kB
457 Shared_Dirty: 0 kB
458 Private_Clean: 0 kB
459 Private_Dirty: 0 kB
460 Referenced: 892 kB
461 Anonymous: 0 kB
462 LazyFree: 0 kB
463 AnonHugePages: 0 kB
464 ShmemPmdMapped: 0 kB
465 Shared_Hugetlb: 0 kB
466 Private_Hugetlb: 0 kB
467 Swap: 0 kB
468 SwapPss: 0 kB
469 KernelPageSize: 4 kB
470 MMUPageSize: 4 kB
471 Locked: 0 kB
472 THPeligible: 0
473 VmFlags: rd ex mr mw me dw
474
475The first of these lines shows the same information as is displayed for the
476mapping in /proc/PID/maps. Following lines show the size of the mapping
477(size); the size of each page allocated when backing a VMA (KernelPageSize),
478which is usually the same as the size in the page table entries; the page size
479used by the MMU when backing a VMA (in most cases, the same as KernelPageSize);
480the amount of the mapping that is currently resident in RAM (RSS); the
481process' proportional share of this mapping (PSS); and the number of clean and
482dirty shared and private pages in the mapping.
483
484The "proportional set size" (PSS) of a process is the count of pages it has
485in memory, where each page is divided by the number of processes sharing it.
486So if a process has 1000 pages all to itself, and 1000 shared with one other
487process, its PSS will be 1500. "Pss_Dirty" is the portion of PSS which
488consists of dirty pages. ("Pss_Clean" is not included, but it can be
489calculated by subtracting "Pss_Dirty" from "Pss".)
490
491Note that even a page which is part of a MAP_SHARED mapping, but has only
492a single pte mapped, i.e. is currently used by only one process, is accounted
493as private and not as shared.
494
495"Referenced" indicates the amount of memory currently marked as referenced or
496accessed.
497
498"Anonymous" shows the amount of memory that does not belong to any file. Even
499a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
500and a page is modified, the file page is replaced by a private anonymous copy.
501
502"LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE).
503The memory isn't freed immediately with madvise(). It's freed in memory
504pressure if the memory is clean. Please note that the printed value might
505be lower than the real value due to optimizations used in the current
506implementation. If this is not desirable please file a bug report.
507
508"AnonHugePages" shows the ammount of memory backed by transparent hugepage.
509
510"ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by
511huge pages.
512
513"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
514hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
515reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
516
517"Swap" shows how much would-be-anonymous memory is also used, but out on swap.
518
519For shmem mappings, "Swap" includes also the size of the mapped (and not
520replaced by copy-on-write) part of the underlying shmem object out on swap.
521"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
522does not take into account swapped out page of underlying shmem objects.
523"Locked" indicates whether the mapping is locked in memory or not.
524
525"THPeligible" indicates whether the mapping is eligible for allocating THP
526pages as well as the THP is PMD mappable or not - 1 if true, 0 otherwise.
527It just shows the current status.
528
529"VmFlags" field deserves a separate description. This member represents the
530kernel flags associated with the particular virtual memory area in two letter
531encoded manner. The codes are the following:
532
533 == =======================================
534 rd readable
535 wr writeable
536 ex executable
537 sh shared
538 mr may read
539 mw may write
540 me may execute
541 ms may share
542 gd stack segment growns down
543 pf pure PFN range
544 dw disabled write to the mapped file
545 lo pages are locked in memory
546 io memory mapped I/O area
547 sr sequential read advise provided
548 rr random read advise provided
549 dc do not copy area on fork
550 de do not expand area on remapping
551 ac area is accountable
552 nr swap space is not reserved for the area
553 ht area uses huge tlb pages
554 sf synchronous page fault
555 ar architecture specific flag
556 wf wipe on fork
557 dd do not include area into core dump
558 sd soft dirty flag
559 mm mixed map area
560 hg huge page advise flag
561 nh no huge page advise flag
562 mg mergable advise flag
563 bt arm64 BTI guarded page
564 mt arm64 MTE allocation tags are enabled
565 um userfaultfd missing tracking
566 uw userfaultfd wr-protect tracking
567 == =======================================
568
569Note that there is no guarantee that every flag and associated mnemonic will
570be present in all further kernel releases. Things get changed, the flags may
571be vanished or the reverse -- new added. Interpretation of their meaning
572might change in future as well. So each consumer of these flags has to
573follow each specific kernel version for the exact semantic.
574
575This file is only present if the CONFIG_MMU kernel configuration option is
576enabled.
577
578Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent
579output can be achieved only in the single read call).
580
581This typically manifests when doing partial reads of these files while the
582memory map is being modified. Despite the races, we do provide the following
583guarantees:
584
5851) The mapped addresses never go backwards, which implies no two
586 regions will ever overlap.
5872) If there is something at a given vaddr during the entirety of the
588 life of the smaps/maps walk, there will be some output for it.
589
590The /proc/PID/smaps_rollup file includes the same fields as /proc/PID/smaps,
591but their values are the sums of the corresponding values for all mappings of
592the process. Additionally, it contains these fields:
593
594- Pss_Anon
595- Pss_File
596- Pss_Shmem
597
598They represent the proportional shares of anonymous, file, and shmem pages, as
599described for smaps above. These fields are omitted in smaps since each
600mapping identifies the type (anon, file, or shmem) of all pages it contains.
601Thus all information in smaps_rollup can be derived from smaps, but at a
602significantly higher cost.
603
604The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
605bits on both physical and virtual pages associated with a process, and the
606soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst
607for details).
608To clear the bits for all the pages associated with the process::
609
610 > echo 1 > /proc/PID/clear_refs
611
612To clear the bits for the anonymous pages associated with the process::
613
614 > echo 2 > /proc/PID/clear_refs
615
616To clear the bits for the file mapped pages associated with the process::
617
618 > echo 3 > /proc/PID/clear_refs
619
620To clear the soft-dirty bit::
621
622 > echo 4 > /proc/PID/clear_refs
623
624To reset the peak resident set size ("high water mark") to the process's
625current value::
626
627 > echo 5 > /proc/PID/clear_refs
628
629Any other value written to /proc/PID/clear_refs will have no effect.
630
631The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
632using /proc/kpageflags and number of times a page is mapped using
633/proc/kpagecount. For detailed explanation, see
634Documentation/admin-guide/mm/pagemap.rst.
635
636The /proc/pid/numa_maps is an extension based on maps, showing the memory
637locality and binding policy, as well as the memory usage (in pages) of
638each mapping. The output follows a general format where mapping details get
639summarized separated by blank spaces, one mapping per each file line::
640
641 address policy mapping details
642
643 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
644 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
645 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
646 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
647 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
648 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
649 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
650 320698b000 default file=/lib64/libc-2.12.so
651 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
652 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
653 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
654 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
655 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
656 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
657 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
658 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
659
660Where:
661
662"address" is the starting address for the mapping;
663
664"policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst);
665
666"mapping details" summarizes mapping data such as mapping type, page usage counters,
667node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
668size, in KB, that is backing the mapping up.
669
6701.2 Kernel data
671---------------
672
673Similar to the process entries, the kernel data files give information about
674the running kernel. The files used to obtain this information are contained in
675/proc and are listed in Table 1-5. Not all of these will be present in your
676system. It depends on the kernel configuration and the loaded modules, which
677files are there, and which are missing.
678
679.. table:: Table 1-5: Kernel info in /proc
680
681 ============ ===============================================================
682 File Content
683 ============ ===============================================================
684 apm Advanced power management info
685 buddyinfo Kernel memory allocator information (see text) (2.5)
686 bus Directory containing bus specific information
687 cmdline Kernel command line
688 cpuinfo Info about the CPU
689 devices Available devices (block and character)
690 dma Used DMS channels
691 filesystems Supported filesystems
692 driver Various drivers grouped here, currently rtc (2.4)
693 execdomains Execdomains, related to security (2.4)
694 fb Frame Buffer devices (2.4)
695 fs File system parameters, currently nfs/exports (2.4)
696 ide Directory containing info about the IDE subsystem
697 interrupts Interrupt usage
698 iomem Memory map (2.4)
699 ioports I/O port usage
700 irq Masks for irq to cpu affinity (2.4)(smp?)
701 isapnp ISA PnP (Plug&Play) Info (2.4)
702 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
703 kmsg Kernel messages
704 ksyms Kernel symbol table
705 loadavg Load average of last 1, 5 & 15 minutes;
706 number of processes currently runnable (running or on ready queue);
707 total number of processes in system;
708 last pid created.
709 All fields are separated by one space except "number of
710 processes currently runnable" and "total number of processes
711 in system", which are separated by a slash ('/'). Example:
712 0.61 0.61 0.55 3/828 22084
713 locks Kernel locks
714 meminfo Memory info
715 misc Miscellaneous
716 modules List of loaded modules
717 mounts Mounted filesystems
718 net Networking info (see text)
719 pagetypeinfo Additional page allocator information (see text) (2.5)
720 partitions Table of partitions known to the system
721 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
722 decoupled by lspci (2.4)
723 rtc Real time clock
724 scsi SCSI info (see text)
725 slabinfo Slab pool info
726 softirqs softirq usage
727 stat Overall statistics
728 swaps Swap space utilization
729 sys See chapter 2
730 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
731 tty Info of tty drivers
732 uptime Wall clock since boot, combined idle time of all cpus
733 version Kernel version
734 video bttv info of video resources (2.4)
735 vmallocinfo Show vmalloced areas
736 ============ ===============================================================
737
738You can, for example, check which interrupts are currently in use and what
739they are used for by looking in the file /proc/interrupts::
740
741 > cat /proc/interrupts
742 CPU0
743 0: 8728810 XT-PIC timer
744 1: 895 XT-PIC keyboard
745 2: 0 XT-PIC cascade
746 3: 531695 XT-PIC aha152x
747 4: 2014133 XT-PIC serial
748 5: 44401 XT-PIC pcnet_cs
749 8: 2 XT-PIC rtc
750 11: 8 XT-PIC i82365
751 12: 182918 XT-PIC PS/2 Mouse
752 13: 1 XT-PIC fpu
753 14: 1232265 XT-PIC ide0
754 15: 7 XT-PIC ide1
755 NMI: 0
756
757In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
758output of a SMP machine)::
759
760 > cat /proc/interrupts
761
762 CPU0 CPU1
763 0: 1243498 1214548 IO-APIC-edge timer
764 1: 8949 8958 IO-APIC-edge keyboard
765 2: 0 0 XT-PIC cascade
766 5: 11286 10161 IO-APIC-edge soundblaster
767 8: 1 0 IO-APIC-edge rtc
768 9: 27422 27407 IO-APIC-edge 3c503
769 12: 113645 113873 IO-APIC-edge PS/2 Mouse
770 13: 0 0 XT-PIC fpu
771 14: 22491 24012 IO-APIC-edge ide0
772 15: 2183 2415 IO-APIC-edge ide1
773 17: 30564 30414 IO-APIC-level eth0
774 18: 177 164 IO-APIC-level bttv
775 NMI: 2457961 2457959
776 LOC: 2457882 2457881
777 ERR: 2155
778
779NMI is incremented in this case because every timer interrupt generates a NMI
780(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
781
782LOC is the local interrupt counter of the internal APIC of every CPU.
783
784ERR is incremented in the case of errors in the IO-APIC bus (the bus that
785connects the CPUs in a SMP system. This means that an error has been detected,
786the IO-APIC automatically retry the transmission, so it should not be a big
787problem, but you should read the SMP-FAQ.
788
789In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
790/proc/interrupts to display every IRQ vector in use by the system, not
791just those considered 'most important'. The new vectors are:
792
793THR
794 interrupt raised when a machine check threshold counter
795 (typically counting ECC corrected errors of memory or cache) exceeds
796 a configurable threshold. Only available on some systems.
797
798TRM
799 a thermal event interrupt occurs when a temperature threshold
800 has been exceeded for the CPU. This interrupt may also be generated
801 when the temperature drops back to normal.
802
803SPU
804 a spurious interrupt is some interrupt that was raised then lowered
805 by some IO device before it could be fully processed by the APIC. Hence
806 the APIC sees the interrupt but does not know what device it came from.
807 For this case the APIC will generate the interrupt with a IRQ vector
808 of 0xff. This might also be generated by chipset bugs.
809
810RES, CAL, TLB
811 rescheduling, call and TLB flush interrupts are
812 sent from one CPU to another per the needs of the OS. Typically,
813 their statistics are used by kernel developers and interested users to
814 determine the occurrence of interrupts of the given type.
815
816The above IRQ vectors are displayed only when relevant. For example,
817the threshold vector does not exist on x86_64 platforms. Others are
818suppressed when the system is a uniprocessor. As of this writing, only
819i386 and x86_64 platforms support the new IRQ vector displays.
820
821Of some interest is the introduction of the /proc/irq directory to 2.4.
822It could be used to set IRQ to CPU affinity. This means that you can "hook" an
823IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
824irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
825prof_cpu_mask.
826
827For example::
828
829 > ls /proc/irq/
830 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
831 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
832 > ls /proc/irq/0/
833 smp_affinity
834
835smp_affinity is a bitmask, in which you can specify which CPUs can handle the
836IRQ. You can set it by doing::
837
838 > echo 1 > /proc/irq/10/smp_affinity
839
840This means that only the first CPU will handle the IRQ, but you can also echo
8415 which means that only the first and third CPU can handle the IRQ.
842
843The contents of each smp_affinity file is the same by default::
844
845 > cat /proc/irq/0/smp_affinity
846 ffffffff
847
848There is an alternate interface, smp_affinity_list which allows specifying
849a CPU range instead of a bitmask::
850
851 > cat /proc/irq/0/smp_affinity_list
852 1024-1031
853
854The default_smp_affinity mask applies to all non-active IRQs, which are the
855IRQs which have not yet been allocated/activated, and hence which lack a
856/proc/irq/[0-9]* directory.
857
858The node file on an SMP system shows the node to which the device using the IRQ
859reports itself as being attached. This hardware locality information does not
860include information about any possible driver locality preference.
861
862prof_cpu_mask specifies which CPUs are to be profiled by the system wide
863profiler. Default value is ffffffff (all CPUs if there are only 32 of them).
864
865The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
866between all the CPUs which are allowed to handle it. As usual the kernel has
867more info than you and does a better job than you, so the defaults are the
868best choice for almost everyone. [Note this applies only to those IO-APIC's
869that support "Round Robin" interrupt distribution.]
870
871There are three more important subdirectories in /proc: net, scsi, and sys.
872The general rule is that the contents, or even the existence of these
873directories, depend on your kernel configuration. If SCSI is not enabled, the
874directory scsi may not exist. The same is true with the net, which is there
875only when networking support is present in the running kernel.
876
877The slabinfo file gives information about memory usage at the slab level.
878Linux uses slab pools for memory management above page level in version 2.2.
879Commonly used objects have their own slab pool (such as network buffers,
880directory cache, and so on).
881
882::
883
884 > cat /proc/buddyinfo
885
886 Node 0, zone DMA 0 4 5 4 4 3 ...
887 Node 0, zone Normal 1 0 0 1 101 8 ...
888 Node 0, zone HighMem 2 0 0 1 1 0 ...
889
890External fragmentation is a problem under some workloads, and buddyinfo is a
891useful tool for helping diagnose these problems. Buddyinfo will give you a
892clue as to how big an area you can safely allocate, or why a previous
893allocation failed.
894
895Each column represents the number of pages of a certain order which are
896available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
897ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
898available in ZONE_NORMAL, etc...
899
900More information relevant to external fragmentation can be found in
901pagetypeinfo::
902
903 > cat /proc/pagetypeinfo
904 Page block order: 9
905 Pages per block: 512
906
907 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
908 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
909 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
910 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
911 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
912 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
913 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
914 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
915 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
916 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
917 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
918
919 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
920 Node 0, zone DMA 2 0 5 1 0
921 Node 0, zone DMA32 41 6 967 2 0
922
923Fragmentation avoidance in the kernel works by grouping pages of different
924migrate types into the same contiguous regions of memory called page blocks.
925A page block is typically the size of the default hugepage size, e.g. 2MB on
926X86-64. By keeping pages grouped based on their ability to move, the kernel
927can reclaim pages within a page block to satisfy a high-order allocation.
928
929The pagetypinfo begins with information on the size of a page block. It
930then gives the same type of information as buddyinfo except broken down
931by migrate-type and finishes with details on how many page blocks of each
932type exist.
933
934If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
935from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
936make an estimate of the likely number of huge pages that can be allocated
937at a given point in time. All the "Movable" blocks should be allocatable
938unless memory has been mlock()'d. Some of the Reclaimable blocks should
939also be allocatable although a lot of filesystem metadata may have to be
940reclaimed to achieve this.
941
942
943meminfo
944~~~~~~~
945
946Provides information about distribution and utilization of memory. This
947varies by architecture and compile options. Some of the counters reported
948here overlap. The memory reported by the non overlapping counters may not
949add up to the overall memory usage and the difference for some workloads
950can be substantial. In many cases there are other means to find out
951additional memory using subsystem specific interfaces, for instance
952/proc/net/sockstat for TCP memory allocations.
953
954Example output. You may not have all of these fields.
955
956::
957
958 > cat /proc/meminfo
959
960 MemTotal: 32858820 kB
961 MemFree: 21001236 kB
962 MemAvailable: 27214312 kB
963 Buffers: 581092 kB
964 Cached: 5587612 kB
965 SwapCached: 0 kB
966 Active: 3237152 kB
967 Inactive: 7586256 kB
968 Active(anon): 94064 kB
969 Inactive(anon): 4570616 kB
970 Active(file): 3143088 kB
971 Inactive(file): 3015640 kB
972 Unevictable: 0 kB
973 Mlocked: 0 kB
974 SwapTotal: 0 kB
975 SwapFree: 0 kB
976 Zswap: 1904 kB
977 Zswapped: 7792 kB
978 Dirty: 12 kB
979 Writeback: 0 kB
980 AnonPages: 4654780 kB
981 Mapped: 266244 kB
982 Shmem: 9976 kB
983 KReclaimable: 517708 kB
984 Slab: 660044 kB
985 SReclaimable: 517708 kB
986 SUnreclaim: 142336 kB
987 KernelStack: 11168 kB
988 PageTables: 20540 kB
989 SecPageTables: 0 kB
990 NFS_Unstable: 0 kB
991 Bounce: 0 kB
992 WritebackTmp: 0 kB
993 CommitLimit: 16429408 kB
994 Committed_AS: 7715148 kB
995 VmallocTotal: 34359738367 kB
996 VmallocUsed: 40444 kB
997 VmallocChunk: 0 kB
998 Percpu: 29312 kB
999 HardwareCorrupted: 0 kB
1000 AnonHugePages: 4149248 kB
1001 ShmemHugePages: 0 kB
1002 ShmemPmdMapped: 0 kB
1003 FileHugePages: 0 kB
1004 FilePmdMapped: 0 kB
1005 CmaTotal: 0 kB
1006 CmaFree: 0 kB
1007 HugePages_Total: 0
1008 HugePages_Free: 0
1009 HugePages_Rsvd: 0
1010 HugePages_Surp: 0
1011 Hugepagesize: 2048 kB
1012 Hugetlb: 0 kB
1013 DirectMap4k: 401152 kB
1014 DirectMap2M: 10008576 kB
1015 DirectMap1G: 24117248 kB
1016
1017MemTotal
1018 Total usable RAM (i.e. physical RAM minus a few reserved
1019 bits and the kernel binary code)
1020MemFree
1021 Total free RAM. On highmem systems, the sum of LowFree+HighFree
1022MemAvailable
1023 An estimate of how much memory is available for starting new
1024 applications, without swapping. Calculated from MemFree,
1025 SReclaimable, the size of the file LRU lists, and the low
1026 watermarks in each zone.
1027 The estimate takes into account that the system needs some
1028 page cache to function well, and that not all reclaimable
1029 slab will be reclaimable, due to items being in use. The
1030 impact of those factors will vary from system to system.
1031Buffers
1032 Relatively temporary storage for raw disk blocks
1033 shouldn't get tremendously large (20MB or so)
1034Cached
1035 In-memory cache for files read from the disk (the
1036 pagecache) as well as tmpfs & shmem.
1037 Doesn't include SwapCached.
1038SwapCached
1039 Memory that once was swapped out, is swapped back in but
1040 still also is in the swapfile (if memory is needed it
1041 doesn't need to be swapped out AGAIN because it is already
1042 in the swapfile. This saves I/O)
1043Active
1044 Memory that has been used more recently and usually not
1045 reclaimed unless absolutely necessary.
1046Inactive
1047 Memory which has been less recently used. It is more
1048 eligible to be reclaimed for other purposes
1049Unevictable
1050 Memory allocated for userspace which cannot be reclaimed, such
1051 as mlocked pages, ramfs backing pages, secret memfd pages etc.
1052Mlocked
1053 Memory locked with mlock().
1054HighTotal, HighFree
1055 Highmem is all memory above ~860MB of physical memory.
1056 Highmem areas are for use by userspace programs, or
1057 for the pagecache. The kernel must use tricks to access
1058 this memory, making it slower to access than lowmem.
1059LowTotal, LowFree
1060 Lowmem is memory which can be used for everything that
1061 highmem can be used for, but it is also available for the
1062 kernel's use for its own data structures. Among many
1063 other things, it is where everything from the Slab is
1064 allocated. Bad things happen when you're out of lowmem.
1065SwapTotal
1066 total amount of swap space available
1067SwapFree
1068 Memory which has been evicted from RAM, and is temporarily
1069 on the disk
1070Zswap
1071 Memory consumed by the zswap backend (compressed size)
1072Zswapped
1073 Amount of anonymous memory stored in zswap (original size)
1074Dirty
1075 Memory which is waiting to get written back to the disk
1076Writeback
1077 Memory which is actively being written back to the disk
1078AnonPages
1079 Non-file backed pages mapped into userspace page tables
1080Mapped
1081 files which have been mmaped, such as libraries
1082Shmem
1083 Total memory used by shared memory (shmem) and tmpfs
1084KReclaimable
1085 Kernel allocations that the kernel will attempt to reclaim
1086 under memory pressure. Includes SReclaimable (below), and other
1087 direct allocations with a shrinker.
1088Slab
1089 in-kernel data structures cache
1090SReclaimable
1091 Part of Slab, that might be reclaimed, such as caches
1092SUnreclaim
1093 Part of Slab, that cannot be reclaimed on memory pressure
1094KernelStack
1095 Memory consumed by the kernel stacks of all tasks
1096PageTables
1097 Memory consumed by userspace page tables
1098SecPageTables
1099 Memory consumed by secondary page tables, this currently
1100 currently includes KVM mmu allocations on x86 and arm64.
1101NFS_Unstable
1102 Always zero. Previous counted pages which had been written to
1103 the server, but has not been committed to stable storage.
1104Bounce
1105 Memory used for block device "bounce buffers"
1106WritebackTmp
1107 Memory used by FUSE for temporary writeback buffers
1108CommitLimit
1109 Based on the overcommit ratio ('vm.overcommit_ratio'),
1110 this is the total amount of memory currently available to
1111 be allocated on the system. This limit is only adhered to
1112 if strict overcommit accounting is enabled (mode 2 in
1113 'vm.overcommit_memory').
1114
1115 The CommitLimit is calculated with the following formula::
1116
1117 CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
1118 overcommit_ratio / 100 + [total swap pages]
1119
1120 For example, on a system with 1G of physical RAM and 7G
1121 of swap with a `vm.overcommit_ratio` of 30 it would
1122 yield a CommitLimit of 7.3G.
1123
1124 For more details, see the memory overcommit documentation
1125 in mm/overcommit-accounting.
1126Committed_AS
1127 The amount of memory presently allocated on the system.
1128 The committed memory is a sum of all of the memory which
1129 has been allocated by processes, even if it has not been
1130 "used" by them as of yet. A process which malloc()'s 1G
1131 of memory, but only touches 300M of it will show up as
1132 using 1G. This 1G is memory which has been "committed" to
1133 by the VM and can be used at any time by the allocating
1134 application. With strict overcommit enabled on the system
1135 (mode 2 in 'vm.overcommit_memory'), allocations which would
1136 exceed the CommitLimit (detailed above) will not be permitted.
1137 This is useful if one needs to guarantee that processes will
1138 not fail due to lack of memory once that memory has been
1139 successfully allocated.
1140VmallocTotal
1141 total size of vmalloc virtual address space
1142VmallocUsed
1143 amount of vmalloc area which is used
1144VmallocChunk
1145 largest contiguous block of vmalloc area which is free
1146Percpu
1147 Memory allocated to the percpu allocator used to back percpu
1148 allocations. This stat excludes the cost of metadata.
1149HardwareCorrupted
1150 The amount of RAM/memory in KB, the kernel identifies as
1151 corrupted.
1152AnonHugePages
1153 Non-file backed huge pages mapped into userspace page tables
1154ShmemHugePages
1155 Memory used by shared memory (shmem) and tmpfs allocated
1156 with huge pages
1157ShmemPmdMapped
1158 Shared memory mapped into userspace with huge pages
1159FileHugePages
1160 Memory used for filesystem data (page cache) allocated
1161 with huge pages
1162FilePmdMapped
1163 Page cache mapped into userspace with huge pages
1164CmaTotal
1165 Memory reserved for the Contiguous Memory Allocator (CMA)
1166CmaFree
1167 Free remaining memory in the CMA reserves
1168HugePages_Total, HugePages_Free, HugePages_Rsvd, HugePages_Surp, Hugepagesize, Hugetlb
1169 See Documentation/admin-guide/mm/hugetlbpage.rst.
1170DirectMap4k, DirectMap2M, DirectMap1G
1171 Breakdown of page table sizes used in the kernel's
1172 identity mapping of RAM
1173
1174vmallocinfo
1175~~~~~~~~~~~
1176
1177Provides information about vmalloced/vmaped areas. One line per area,
1178containing the virtual address range of the area, size in bytes,
1179caller information of the creator, and optional information depending
1180on the kind of area:
1181
1182 ========== ===================================================
1183 pages=nr number of pages
1184 phys=addr if a physical address was specified
1185 ioremap I/O mapping (ioremap() and friends)
1186 vmalloc vmalloc() area
1187 vmap vmap()ed pages
1188 user VM_USERMAP area
1189 vpages buffer for pages pointers was vmalloced (huge area)
1190 N<node>=nr (Only on NUMA kernels)
1191 Number of pages allocated on memory node <node>
1192 ========== ===================================================
1193
1194::
1195
1196 > cat /proc/vmallocinfo
1197 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
1198 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
1199 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
1200 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
1201 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
1202 phys=7fee8000 ioremap
1203 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
1204 phys=7fee7000 ioremap
1205 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
1206 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
1207 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
1208 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
1209 pages=2 vmalloc N1=2
1210 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
1211 /0x130 [x_tables] pages=4 vmalloc N0=4
1212 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
1213 pages=14 vmalloc N2=14
1214 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
1215 pages=4 vmalloc N1=4
1216 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
1217 pages=2 vmalloc N1=2
1218 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
1219 pages=10 vmalloc N0=10
1220
1221
1222softirqs
1223~~~~~~~~
1224
1225Provides counts of softirq handlers serviced since boot time, for each CPU.
1226
1227::
1228
1229 > cat /proc/softirqs
1230 CPU0 CPU1 CPU2 CPU3
1231 HI: 0 0 0 0
1232 TIMER: 27166 27120 27097 27034
1233 NET_TX: 0 0 0 17
1234 NET_RX: 42 0 0 39
1235 BLOCK: 0 0 107 1121
1236 TASKLET: 0 0 0 290
1237 SCHED: 27035 26983 26971 26746
1238 HRTIMER: 0 0 0 0
1239 RCU: 1678 1769 2178 2250
1240
12411.3 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
13201.4 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
13831.5 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
14081.6 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
14431.7 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
15161.8 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
15321.9 /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) (n…m) (m+1)(m+2) (m+3) (m+4)
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 (n…m) optional fields: zero or more fields of the form "tag[:value]"
1848 (m+1) separator: marks the end of the optional fields
1849 (m+2) filesystem type: name of filesystem of the form "type[.subtype]"
1850 (m+3) mount source: filesystem specific information or "none"
1851 (m+4) 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 four fields -- 'pos', 'flags', 'mnt_id' and 'ino'.
1903The 'pos' represents the current offset of the opened file in decimal
1904form [see lseek(2) for details], 'flags' denotes the octal O_xxx mask the
1905file has been created with [see open(2) for details] and 'mnt_id' represents
1906mount ID of the file system containing the opened file [see 3.5
1907/proc/<pid>/mountinfo for details]. 'ino' represents the inode number of
1908the file.
1909
1910A typical output is::
1911
1912 pos: 0
1913 flags: 0100002
1914 mnt_id: 19
1915 ino: 63107
1916
1917All locks associated with a file descriptor are shown in its fdinfo too::
1918
1919 lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF
1920
1921The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1922pair provide additional information particular to the objects they represent.
1923
1924Eventfd files
1925~~~~~~~~~~~~~
1926
1927::
1928
1929 pos: 0
1930 flags: 04002
1931 mnt_id: 9
1932 ino: 63107
1933 eventfd-count: 5a
1934
1935where 'eventfd-count' is hex value of a counter.
1936
1937Signalfd files
1938~~~~~~~~~~~~~~
1939
1940::
1941
1942 pos: 0
1943 flags: 04002
1944 mnt_id: 9
1945 ino: 63107
1946 sigmask: 0000000000000200
1947
1948where 'sigmask' is hex value of the signal mask associated
1949with a file.
1950
1951Epoll files
1952~~~~~~~~~~~
1953
1954::
1955
1956 pos: 0
1957 flags: 02
1958 mnt_id: 9
1959 ino: 63107
1960 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7
1961
1962where 'tfd' is a target file descriptor number in decimal form,
1963'events' is events mask being watched and the 'data' is data
1964associated with a target [see epoll(7) for more details].
1965
1966The 'pos' is current offset of the target file in decimal form
1967[see lseek(2)], 'ino' and 'sdev' are inode and device numbers
1968where target file resides, all in hex format.
1969
1970Fsnotify files
1971~~~~~~~~~~~~~~
1972For inotify files the format is the following::
1973
1974 pos: 0
1975 flags: 02000000
1976 mnt_id: 9
1977 ino: 63107
1978 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1979
1980where 'wd' is a watch descriptor in decimal form, i.e. a target file
1981descriptor number, 'ino' and 'sdev' are inode and device where the
1982target file resides and the 'mask' is the mask of events, all in hex
1983form [see inotify(7) for more details].
1984
1985If the kernel was built with exportfs support, the path to the target
1986file is encoded as a file handle. The file handle is provided by three
1987fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1988format.
1989
1990If the kernel is built without exportfs support the file handle won't be
1991printed out.
1992
1993If there is no inotify mark attached yet the 'inotify' line will be omitted.
1994
1995For fanotify files the format is::
1996
1997 pos: 0
1998 flags: 02
1999 mnt_id: 9
2000 ino: 63107
2001 fanotify flags:10 event-flags:0
2002 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
2003 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
2004
2005where fanotify 'flags' and 'event-flags' are values used in fanotify_init
2006call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
2007flags associated with mark which are tracked separately from events
2008mask. 'ino' and 'sdev' are target inode and device, 'mask' is the events
2009mask and 'ignored_mask' is the mask of events which are to be ignored.
2010All are in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
2011provide information about flags and mask used in fanotify_mark
2012call [see fsnotify manpage for details].
2013
2014While the first three lines are mandatory and always printed, the rest is
2015optional and may be omitted if no marks created yet.
2016
2017Timerfd files
2018~~~~~~~~~~~~~
2019
2020::
2021
2022 pos: 0
2023 flags: 02
2024 mnt_id: 9
2025 ino: 63107
2026 clockid: 0
2027 ticks: 0
2028 settime flags: 01
2029 it_value: (0, 49406829)
2030 it_interval: (1, 0)
2031
2032where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
2033that have occurred [see timerfd_create(2) for details]. 'settime flags' are
2034flags in octal form been used to setup the timer [see timerfd_settime(2) for
2035details]. 'it_value' is remaining time until the timer expiration.
2036'it_interval' is the interval for the timer. Note the timer might be set up
2037with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
2038still exhibits timer's remaining time.
2039
2040DMA Buffer files
2041~~~~~~~~~~~~~~~~
2042
2043::
2044
2045 pos: 0
2046 flags: 04002
2047 mnt_id: 9
2048 ino: 63107
2049 size: 32768
2050 count: 2
2051 exp_name: system-heap
2052
2053where 'size' is the size of the DMA buffer in bytes. 'count' is the file count of
2054the DMA buffer file. 'exp_name' is the name of the DMA buffer exporter.
2055
20563.9 /proc/<pid>/map_files - Information about memory mapped files
2057---------------------------------------------------------------------
2058This directory contains symbolic links which represent memory mapped files
2059the process is maintaining. Example output::
2060
2061 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
2062 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
2063 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
2064 | ...
2065 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
2066 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
2067
2068The name of a link represents the virtual memory bounds of a mapping, i.e.
2069vm_area_struct::vm_start-vm_area_struct::vm_end.
2070
2071The main purpose of the map_files is to retrieve a set of memory mapped
2072files in a fast way instead of parsing /proc/<pid>/maps or
2073/proc/<pid>/smaps, both of which contain many more records. At the same
2074time one can open(2) mappings from the listings of two processes and
2075comparing their inode numbers to figure out which anonymous memory areas
2076are actually shared.
2077
20783.10 /proc/<pid>/timerslack_ns - Task timerslack value
2079---------------------------------------------------------
2080This file provides the value of the task's timerslack value in nanoseconds.
2081This value specifies an amount of time that normal timers may be deferred
2082in order to coalesce timers and avoid unnecessary wakeups.
2083
2084This allows a task's interactivity vs power consumption tradeoff to be
2085adjusted.
2086
2087Writing 0 to the file will set the task's timerslack to the default value.
2088
2089Valid values are from 0 - ULLONG_MAX
2090
2091An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
2092permissions on the task specified to change its timerslack_ns value.
2093
20943.11 /proc/<pid>/patch_state - Livepatch patch operation state
2095-----------------------------------------------------------------
2096When CONFIG_LIVEPATCH is enabled, this file displays the value of the
2097patch state for the task.
2098
2099A value of '-1' indicates that no patch is in transition.
2100
2101A value of '0' indicates that a patch is in transition and the task is
2102unpatched. If the patch is being enabled, then the task hasn't been
2103patched yet. If the patch is being disabled, then the task has already
2104been unpatched.
2105
2106A value of '1' indicates that a patch is in transition and the task is
2107patched. If the patch is being enabled, then the task has already been
2108patched. If the patch is being disabled, then the task hasn't been
2109unpatched yet.
2110
21113.12 /proc/<pid>/arch_status - task architecture specific status
2112-------------------------------------------------------------------
2113When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the
2114architecture specific status of the task.
2115
2116Example
2117~~~~~~~
2118
2119::
2120
2121 $ cat /proc/6753/arch_status
2122 AVX512_elapsed_ms: 8
2123
2124Description
2125~~~~~~~~~~~
2126
2127x86 specific entries
2128~~~~~~~~~~~~~~~~~~~~~
2129
2130AVX512_elapsed_ms
2131^^^^^^^^^^^^^^^^^^
2132
2133 If AVX512 is supported on the machine, this entry shows the milliseconds
2134 elapsed since the last time AVX512 usage was recorded. The recording
2135 happens on a best effort basis when a task is scheduled out. This means
2136 that the value depends on two factors:
2137
2138 1) The time which the task spent on the CPU without being scheduled
2139 out. With CPU isolation and a single runnable task this can take
2140 several seconds.
2141
2142 2) The time since the task was scheduled out last. Depending on the
2143 reason for being scheduled out (time slice exhausted, syscall ...)
2144 this can be arbitrary long time.
2145
2146 As a consequence the value cannot be considered precise and authoritative
2147 information. The application which uses this information has to be aware
2148 of the overall scenario on the system in order to determine whether a
2149 task is a real AVX512 user or not. Precise information can be obtained
2150 with performance counters.
2151
2152 A special value of '-1' indicates that no AVX512 usage was recorded, thus
2153 the task is unlikely an AVX512 user, but depends on the workload and the
2154 scheduling scenario, it also could be a false negative mentioned above.
2155
21563.13 /proc/<pid>/fd - List of symlinks to open files
2157-------------------------------------------------------
2158This directory contains symbolic links which represent open files
2159the process is maintaining. Example output::
2160
2161 lr-x------ 1 root root 64 Sep 20 17:53 0 -> /dev/null
2162 l-wx------ 1 root root 64 Sep 20 17:53 1 -> /dev/null
2163 lrwx------ 1 root root 64 Sep 20 17:53 10 -> 'socket:[12539]'
2164 lrwx------ 1 root root 64 Sep 20 17:53 11 -> 'socket:[12540]'
2165 lrwx------ 1 root root 64 Sep 20 17:53 12 -> 'socket:[12542]'
2166
2167The number of open files for the process is stored in 'size' member
2168of stat() output for /proc/<pid>/fd for fast access.
2169-------------------------------------------------------
2170
2171
2172Chapter 4: Configuring procfs
2173=============================
2174
21754.1 Mount options
2176---------------------
2177
2178The following mount options are supported:
2179
2180 ========= ========================================================
2181 hidepid= Set /proc/<pid>/ access mode.
2182 gid= Set the group authorized to learn processes information.
2183 subset= Show only the specified subset of procfs.
2184 ========= ========================================================
2185
2186hidepid=off or hidepid=0 means classic mode - everybody may access all
2187/proc/<pid>/ directories (default).
2188
2189hidepid=noaccess or hidepid=1 means users may not access any /proc/<pid>/
2190directories but their own. Sensitive files like cmdline, sched*, status are now
2191protected against other users. This makes it impossible to learn whether any
2192user runs specific program (given the program doesn't reveal itself by its
2193behaviour). As an additional bonus, as /proc/<pid>/cmdline is unaccessible for
2194other users, poorly written programs passing sensitive information via program
2195arguments are now protected against local eavesdroppers.
2196
2197hidepid=invisible or hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be
2198fully invisible to other users. It doesn't mean that it hides a fact whether a
2199process with a specific pid value exists (it can be learned by other means, e.g.
2200by "kill -0 $PID"), but it hides process' uid and gid, which may be learned by
2201stat()'ing /proc/<pid>/ otherwise. It greatly complicates an intruder's task of
2202gathering information about running processes, whether some daemon runs with
2203elevated privileges, whether other user runs some sensitive program, whether
2204other users run any program at all, etc.
2205
2206hidepid=ptraceable or hidepid=4 means that procfs should only contain
2207/proc/<pid>/ directories that the caller can ptrace.
2208
2209gid= defines a group authorized to learn processes information otherwise
2210prohibited by hidepid=. If you use some daemon like identd which needs to learn
2211information about processes information, just add identd to this group.
2212
2213subset=pid hides all top level files and directories in the procfs that
2214are not related to tasks.
2215
2216Chapter 5: Filesystem behavior
2217==============================
2218
2219Originally, before the advent of pid namepsace, procfs was a global file
2220system. It means that there was only one procfs instance in the system.
2221
2222When pid namespace was added, a separate procfs instance was mounted in
2223each pid namespace. So, procfs mount options are global among all
2224mountpoints within the same namespace::
2225
2226 # grep ^proc /proc/mounts
2227 proc /proc proc rw,relatime,hidepid=2 0 0
2228
2229 # strace -e mount mount -o hidepid=1 -t proc proc /tmp/proc
2230 mount("proc", "/tmp/proc", "proc", 0, "hidepid=1") = 0
2231 +++ exited with 0 +++
2232
2233 # grep ^proc /proc/mounts
2234 proc /proc proc rw,relatime,hidepid=2 0 0
2235 proc /tmp/proc proc rw,relatime,hidepid=2 0 0
2236
2237and only after remounting procfs mount options will change at all
2238mountpoints::
2239
2240 # mount -o remount,hidepid=1 -t proc proc /tmp/proc
2241
2242 # grep ^proc /proc/mounts
2243 proc /proc proc rw,relatime,hidepid=1 0 0
2244 proc /tmp/proc proc rw,relatime,hidepid=1 0 0
2245
2246This behavior is different from the behavior of other filesystems.
2247
2248The new procfs behavior is more like other filesystems. Each procfs mount
2249creates a new procfs instance. Mount options affect own procfs instance.
2250It means that it became possible to have several procfs instances
2251displaying tasks with different filtering options in one pid namespace::
2252
2253 # mount -o hidepid=invisible -t proc proc /proc
2254 # mount -o hidepid=noaccess -t proc proc /tmp/proc
2255 # grep ^proc /proc/mounts
2256 proc /proc proc rw,relatime,hidepid=invisible 0 0
2257 proc /tmp/proc proc rw,relatime,hidepid=noaccess 0 0