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1------------------------------------------------------------------------------
2 T H E /proc F I L E S Y S T E M
3------------------------------------------------------------------------------
4/proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999
5 Bodo Bauer <bb@ricochet.net>
6
72.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
8move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
9------------------------------------------------------------------------------
10Version 1.3 Kernel version 2.2.12
11 Kernel version 2.4.0-test11-pre4
12------------------------------------------------------------------------------
13fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009
14
15Table of Contents
16-----------------
17
18 0 Preface
19 0.1 Introduction/Credits
20 0.2 Legal Stuff
21
22 1 Collecting System Information
23 1.1 Process-Specific Subdirectories
24 1.2 Kernel data
25 1.3 IDE devices in /proc/ide
26 1.4 Networking info in /proc/net
27 1.5 SCSI info
28 1.6 Parallel port info in /proc/parport
29 1.7 TTY info in /proc/tty
30 1.8 Miscellaneous kernel statistics in /proc/stat
31 1.9 Ext4 file system parameters
32
33 2 Modifying System Parameters
34
35 3 Per-Process Parameters
36 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
37 score
38 3.2 /proc/<pid>/oom_score - Display current oom-killer score
39 3.3 /proc/<pid>/io - Display the IO accounting fields
40 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
41 3.5 /proc/<pid>/mountinfo - Information about mounts
42 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
43 3.7 /proc/<pid>/task/<tid>/children - Information about task children
44 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
45 3.9 /proc/<pid>/map_files - Information about memory mapped files
46 3.10 /proc/<pid>/timerslack_ns - Task timerslack value
47 3.11 /proc/<pid>/patch_state - Livepatch patch operation state
48
49 4 Configuring procfs
50 4.1 Mount options
51
52------------------------------------------------------------------------------
53Preface
54------------------------------------------------------------------------------
55
560.1 Introduction/Credits
57------------------------
58
59This documentation is part of a soon (or so we hope) to be released book on
60the SuSE Linux distribution. As there is no complete documentation for the
61/proc file system and we've used many freely available sources to write these
62chapters, it seems only fair to give the work back to the Linux community.
63This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
64afraid it's still far from complete, but we hope it will be useful. As far as
65we know, it is the first 'all-in-one' document about the /proc file system. It
66is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
67SPARC, AXP, etc., features, you probably won't find what you are looking for.
68It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
69additions and patches are welcome and will be added to this document if you
70mail them to Bodo.
71
72We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
73other people for help compiling this documentation. We'd also like to extend a
74special thank you to Andi Kleen for documentation, which we relied on heavily
75to create this document, as well as the additional information he provided.
76Thanks to everybody else who contributed source or docs to the Linux kernel
77and helped create a great piece of software... :)
78
79If you have any comments, corrections or additions, please don't hesitate to
80contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
81document.
82
83The latest version of this document is available online at
84http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
85
86If the above direction does not works for you, you could try the kernel
87mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
88comandante@zaralinux.com.
89
900.2 Legal Stuff
91---------------
92
93We don't guarantee the correctness of this document, and if you come to us
94complaining about how you screwed up your system because of incorrect
95documentation, we won't feel responsible...
96
97------------------------------------------------------------------------------
98CHAPTER 1: COLLECTING SYSTEM INFORMATION
99------------------------------------------------------------------------------
100
101------------------------------------------------------------------------------
102In This Chapter
103------------------------------------------------------------------------------
104* Investigating the properties of the pseudo file system /proc and its
105 ability to provide information on the running Linux system
106* Examining /proc's structure
107* Uncovering various information about the kernel and the processes running
108 on the system
109------------------------------------------------------------------------------
110
111
112The proc file system acts as an interface to internal data structures in the
113kernel. It can be used to obtain information about the system and to change
114certain kernel parameters at runtime (sysctl).
115
116First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
117show you how you can use /proc/sys to change settings.
118
1191.1 Process-Specific Subdirectories
120-----------------------------------
121
122The directory /proc contains (among other things) one subdirectory for each
123process running on the system, which is named after the process ID (PID).
124
125The link self points to the process reading the file system. Each process
126subdirectory has the entries listed in Table 1-1.
127
128
129Table 1-1: Process specific entries in /proc
130..............................................................................
131 File Content
132 clear_refs Clears page referenced bits shown in smaps output
133 cmdline Command line arguments
134 cpu Current and last cpu in which it was executed (2.4)(smp)
135 cwd Link to the current working directory
136 environ Values of environment variables
137 exe Link to the executable of this process
138 fd Directory, which contains all file descriptors
139 maps Memory maps to executables and library files (2.4)
140 mem Memory held by this process
141 root Link to the root directory of this process
142 stat Process status
143 statm Process memory status information
144 status Process status in human readable form
145 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function
146 symbol the task is blocked in - or "0" if not blocked.
147 pagemap Page table
148 stack Report full stack trace, enable via CONFIG_STACKTRACE
149 smaps an extension based on maps, showing the memory consumption of
150 each mapping and flags associated with it
151 numa_maps an extension based on maps, showing the memory locality and
152 binding policy as well as mem usage (in pages) of each mapping.
153..............................................................................
154
155For example, to get the status information of a process, all you have to do is
156read the file /proc/PID/status:
157
158 >cat /proc/self/status
159 Name: cat
160 State: R (running)
161 Tgid: 5452
162 Pid: 5452
163 PPid: 743
164 TracerPid: 0 (2.4)
165 Uid: 501 501 501 501
166 Gid: 100 100 100 100
167 FDSize: 256
168 Groups: 100 14 16
169 VmPeak: 5004 kB
170 VmSize: 5004 kB
171 VmLck: 0 kB
172 VmHWM: 476 kB
173 VmRSS: 476 kB
174 RssAnon: 352 kB
175 RssFile: 120 kB
176 RssShmem: 4 kB
177 VmData: 156 kB
178 VmStk: 88 kB
179 VmExe: 68 kB
180 VmLib: 1412 kB
181 VmPTE: 20 kb
182 VmSwap: 0 kB
183 HugetlbPages: 0 kB
184 CoreDumping: 0
185 Threads: 1
186 SigQ: 0/28578
187 SigPnd: 0000000000000000
188 ShdPnd: 0000000000000000
189 SigBlk: 0000000000000000
190 SigIgn: 0000000000000000
191 SigCgt: 0000000000000000
192 CapInh: 00000000fffffeff
193 CapPrm: 0000000000000000
194 CapEff: 0000000000000000
195 CapBnd: ffffffffffffffff
196 NoNewPrivs: 0
197 Seccomp: 0
198 voluntary_ctxt_switches: 0
199 nonvoluntary_ctxt_switches: 1
200
201This shows you nearly the same information you would get if you viewed it with
202the ps command. In fact, ps uses the proc file system to obtain its
203information. But you get a more detailed view of the process by reading the
204file /proc/PID/status. It fields are described in table 1-2.
205
206The statm file contains more detailed information about the process
207memory usage. Its seven fields are explained in Table 1-3. The stat file
208contains details information about the process itself. Its fields are
209explained in Table 1-4.
210
211(for SMP CONFIG users)
212For making accounting scalable, RSS related information are handled in an
213asynchronous manner and the value may not be very precise. To see a precise
214snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
215It's slow but very precise.
216
217Table 1-2: Contents of the status files (as of 4.8)
218..............................................................................
219 Field Content
220 Name filename of the executable
221 Umask file mode creation mask
222 State state (R is running, S is sleeping, D is sleeping
223 in an uninterruptible wait, Z is zombie,
224 T is traced or stopped)
225 Tgid thread group ID
226 Ngid NUMA group ID (0 if none)
227 Pid process id
228 PPid process id of the parent process
229 TracerPid PID of process tracing this process (0 if not)
230 Uid Real, effective, saved set, and file system UIDs
231 Gid Real, effective, saved set, and file system GIDs
232 FDSize number of file descriptor slots currently allocated
233 Groups supplementary group list
234 NStgid descendant namespace thread group ID hierarchy
235 NSpid descendant namespace process ID hierarchy
236 NSpgid descendant namespace process group ID hierarchy
237 NSsid descendant namespace session ID hierarchy
238 VmPeak peak virtual memory size
239 VmSize total program size
240 VmLck locked memory size
241 VmPin pinned memory size
242 VmHWM peak resident set size ("high water mark")
243 VmRSS size of memory portions. It contains the three
244 following parts (VmRSS = RssAnon + RssFile + RssShmem)
245 RssAnon size of resident anonymous memory
246 RssFile size of resident file mappings
247 RssShmem size of resident shmem memory (includes SysV shm,
248 mapping of tmpfs and shared anonymous mappings)
249 VmData size of private data segments
250 VmStk size of stack segments
251 VmExe size of text segment
252 VmLib size of shared library code
253 VmPTE size of page table entries
254 VmSwap amount of swap used by anonymous private data
255 (shmem swap usage is not included)
256 HugetlbPages size of hugetlb memory portions
257 CoreDumping process's memory is currently being dumped
258 (killing the process may lead to a corrupted core)
259 Threads number of threads
260 SigQ number of signals queued/max. number for queue
261 SigPnd bitmap of pending signals for the thread
262 ShdPnd bitmap of shared pending signals for the process
263 SigBlk bitmap of blocked signals
264 SigIgn bitmap of ignored signals
265 SigCgt bitmap of caught signals
266 CapInh bitmap of inheritable capabilities
267 CapPrm bitmap of permitted capabilities
268 CapEff bitmap of effective capabilities
269 CapBnd bitmap of capabilities bounding set
270 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
271 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
272 Cpus_allowed mask of CPUs on which this process may run
273 Cpus_allowed_list Same as previous, but in "list format"
274 Mems_allowed mask of memory nodes allowed to this process
275 Mems_allowed_list Same as previous, but in "list format"
276 voluntary_ctxt_switches number of voluntary context switches
277 nonvoluntary_ctxt_switches number of non voluntary context switches
278..............................................................................
279
280Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
281..............................................................................
282 Field Content
283 size total program size (pages) (same as VmSize in status)
284 resident size of memory portions (pages) (same as VmRSS in status)
285 shared number of pages that are shared (i.e. backed by a file, same
286 as RssFile+RssShmem in status)
287 trs number of pages that are 'code' (not including libs; broken,
288 includes data segment)
289 lrs number of pages of library (always 0 on 2.6)
290 drs number of pages of data/stack (including libs; broken,
291 includes library text)
292 dt number of dirty pages (always 0 on 2.6)
293..............................................................................
294
295
296Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
297..............................................................................
298 Field Content
299 pid process id
300 tcomm filename of the executable
301 state state (R is running, S is sleeping, D is sleeping in an
302 uninterruptible wait, Z is zombie, T is traced or stopped)
303 ppid process id of the parent process
304 pgrp pgrp of the process
305 sid session id
306 tty_nr tty the process uses
307 tty_pgrp pgrp of the tty
308 flags task flags
309 min_flt number of minor faults
310 cmin_flt number of minor faults with child's
311 maj_flt number of major faults
312 cmaj_flt number of major faults with child's
313 utime user mode jiffies
314 stime kernel mode jiffies
315 cutime user mode jiffies with child's
316 cstime kernel mode jiffies with child's
317 priority priority level
318 nice nice level
319 num_threads number of threads
320 it_real_value (obsolete, always 0)
321 start_time time the process started after system boot
322 vsize virtual memory size
323 rss resident set memory size
324 rsslim current limit in bytes on the rss
325 start_code address above which program text can run
326 end_code address below which program text can run
327 start_stack address of the start of the main process stack
328 esp current value of ESP
329 eip current value of EIP
330 pending bitmap of pending signals
331 blocked bitmap of blocked signals
332 sigign bitmap of ignored signals
333 sigcatch bitmap of caught signals
334 0 (place holder, used to be the wchan address, use /proc/PID/wchan instead)
335 0 (place holder)
336 0 (place holder)
337 exit_signal signal to send to parent thread on exit
338 task_cpu which CPU the task is scheduled on
339 rt_priority realtime priority
340 policy scheduling policy (man sched_setscheduler)
341 blkio_ticks time spent waiting for block IO
342 gtime guest time of the task in jiffies
343 cgtime guest time of the task children in jiffies
344 start_data address above which program data+bss is placed
345 end_data address below which program data+bss is placed
346 start_brk address above which program heap can be expanded with brk()
347 arg_start address above which program command line is placed
348 arg_end address below which program command line is placed
349 env_start address above which program environment is placed
350 env_end address below which program environment is placed
351 exit_code the thread's exit_code in the form reported by the waitpid system call
352..............................................................................
353
354The /proc/PID/maps file containing the currently mapped memory regions and
355their access permissions.
356
357The format is:
358
359address perms offset dev inode pathname
360
36108048000-08049000 r-xp 00000000 03:00 8312 /opt/test
36208049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
3630804a000-0806b000 rw-p 00000000 00:00 0 [heap]
364a7cb1000-a7cb2000 ---p 00000000 00:00 0
365a7cb2000-a7eb2000 rw-p 00000000 00:00 0
366a7eb2000-a7eb3000 ---p 00000000 00:00 0
367a7eb3000-a7ed5000 rw-p 00000000 00:00 0
368a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
369a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
370a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
371a800b000-a800e000 rw-p 00000000 00:00 0
372a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
373a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
374a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
375a8024000-a8027000 rw-p 00000000 00:00 0
376a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
377a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
378a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
379aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
380ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
381
382where "address" is the address space in the process that it occupies, "perms"
383is a set of permissions:
384
385 r = read
386 w = write
387 x = execute
388 s = shared
389 p = private (copy on write)
390
391"offset" is the offset into the mapping, "dev" is the device (major:minor), and
392"inode" is the inode on that device. 0 indicates that no inode is associated
393with the memory region, as the case would be with BSS (uninitialized data).
394The "pathname" shows the name associated file for this mapping. If the mapping
395is not associated with a file:
396
397 [heap] = the heap of the program
398 [stack] = the stack of the main process
399 [vdso] = the "virtual dynamic shared object",
400 the kernel system call handler
401
402 or if empty, the mapping is anonymous.
403
404The /proc/PID/smaps is an extension based on maps, showing the memory
405consumption for each of the process's mappings. For each of mappings there
406is a series of lines such as the following:
407
40808048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
409Size: 1084 kB
410Rss: 892 kB
411Pss: 374 kB
412Shared_Clean: 892 kB
413Shared_Dirty: 0 kB
414Private_Clean: 0 kB
415Private_Dirty: 0 kB
416Referenced: 892 kB
417Anonymous: 0 kB
418LazyFree: 0 kB
419AnonHugePages: 0 kB
420ShmemPmdMapped: 0 kB
421Shared_Hugetlb: 0 kB
422Private_Hugetlb: 0 kB
423Swap: 0 kB
424SwapPss: 0 kB
425KernelPageSize: 4 kB
426MMUPageSize: 4 kB
427Locked: 0 kB
428VmFlags: rd ex mr mw me dw
429
430the first of these lines shows the same information as is displayed for the
431mapping in /proc/PID/maps. The remaining lines show the size of the mapping
432(size), the amount of the mapping that is currently resident in RAM (RSS), the
433process' proportional share of this mapping (PSS), the number of clean and
434dirty private pages in the mapping.
435
436The "proportional set size" (PSS) of a process is the count of pages it has
437in memory, where each page is divided by the number of processes sharing it.
438So if a process has 1000 pages all to itself, and 1000 shared with one other
439process, its PSS will be 1500.
440Note that even a page which is part of a MAP_SHARED mapping, but has only
441a single pte mapped, i.e. is currently used by only one process, is accounted
442as private and not as shared.
443"Referenced" indicates the amount of memory currently marked as referenced or
444accessed.
445"Anonymous" shows the amount of memory that does not belong to any file. Even
446a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
447and a page is modified, the file page is replaced by a private anonymous copy.
448"LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE).
449The memory isn't freed immediately with madvise(). It's freed in memory
450pressure if the memory is clean. Please note that the printed value might
451be lower than the real value due to optimizations used in the current
452implementation. If this is not desirable please file a bug report.
453"AnonHugePages" shows the ammount of memory backed by transparent hugepage.
454"ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by
455huge pages.
456"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
457hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
458reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
459"Swap" shows how much would-be-anonymous memory is also used, but out on swap.
460For shmem mappings, "Swap" includes also the size of the mapped (and not
461replaced by copy-on-write) part of the underlying shmem object out on swap.
462"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
463does not take into account swapped out page of underlying shmem objects.
464"Locked" indicates whether the mapping is locked in memory or not.
465
466"VmFlags" field deserves a separate description. This member represents the kernel
467flags associated with the particular virtual memory area in two letter encoded
468manner. The codes are the following:
469 rd - readable
470 wr - writeable
471 ex - executable
472 sh - shared
473 mr - may read
474 mw - may write
475 me - may execute
476 ms - may share
477 gd - stack segment growns down
478 pf - pure PFN range
479 dw - disabled write to the mapped file
480 lo - pages are locked in memory
481 io - memory mapped I/O area
482 sr - sequential read advise provided
483 rr - random read advise provided
484 dc - do not copy area on fork
485 de - do not expand area on remapping
486 ac - area is accountable
487 nr - swap space is not reserved for the area
488 ht - area uses huge tlb pages
489 ar - architecture specific flag
490 dd - do not include area into core dump
491 sd - soft-dirty flag
492 mm - mixed map area
493 hg - huge page advise flag
494 nh - no-huge page advise flag
495 mg - mergable advise flag
496
497Note that there is no guarantee that every flag and associated mnemonic will
498be present in all further kernel releases. Things get changed, the flags may
499be vanished or the reverse -- new added.
500
501This file is only present if the CONFIG_MMU kernel configuration option is
502enabled.
503
504Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent
505output can be achieved only in the single read call).
506This typically manifests when doing partial reads of these files while the
507memory map is being modified. Despite the races, we do provide the following
508guarantees:
509
5101) The mapped addresses never go backwards, which implies no two
511 regions will ever overlap.
5122) If there is something at a given vaddr during the entirety of the
513 life of the smaps/maps walk, there will be some output for it.
514
515
516The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
517bits on both physical and virtual pages associated with a process, and the
518soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details).
519To clear the bits for all the pages associated with the process
520 > echo 1 > /proc/PID/clear_refs
521
522To clear the bits for the anonymous pages associated with the process
523 > echo 2 > /proc/PID/clear_refs
524
525To clear the bits for the file mapped pages associated with the process
526 > echo 3 > /proc/PID/clear_refs
527
528To clear the soft-dirty bit
529 > echo 4 > /proc/PID/clear_refs
530
531To reset the peak resident set size ("high water mark") to the process's
532current value:
533 > echo 5 > /proc/PID/clear_refs
534
535Any other value written to /proc/PID/clear_refs will have no effect.
536
537The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
538using /proc/kpageflags and number of times a page is mapped using
539/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
540
541The /proc/pid/numa_maps is an extension based on maps, showing the memory
542locality and binding policy, as well as the memory usage (in pages) of
543each mapping. The output follows a general format where mapping details get
544summarized separated by blank spaces, one mapping per each file line:
545
546address policy mapping details
547
54800400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
54900600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5503206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
551320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5523206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5533206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5543206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
555320698b000 default file=/lib64/libc-2.12.so
5563206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
5573206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5583206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
5597f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
5607f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
5617f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
5627fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
5637fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
564
565Where:
566"address" is the starting address for the mapping;
567"policy" reports the NUMA memory policy set for the mapping (see vm/numa_memory_policy.txt);
568"mapping details" summarizes mapping data such as mapping type, page usage counters,
569node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
570size, in KB, that is backing the mapping up.
571
5721.2 Kernel data
573---------------
574
575Similar to the process entries, the kernel data files give information about
576the running kernel. The files used to obtain this information are contained in
577/proc and are listed in Table 1-5. Not all of these will be present in your
578system. It depends on the kernel configuration and the loaded modules, which
579files are there, and which are missing.
580
581Table 1-5: Kernel info in /proc
582..............................................................................
583 File Content
584 apm Advanced power management info
585 buddyinfo Kernel memory allocator information (see text) (2.5)
586 bus Directory containing bus specific information
587 cmdline Kernel command line
588 cpuinfo Info about the CPU
589 devices Available devices (block and character)
590 dma Used DMS channels
591 filesystems Supported filesystems
592 driver Various drivers grouped here, currently rtc (2.4)
593 execdomains Execdomains, related to security (2.4)
594 fb Frame Buffer devices (2.4)
595 fs File system parameters, currently nfs/exports (2.4)
596 ide Directory containing info about the IDE subsystem
597 interrupts Interrupt usage
598 iomem Memory map (2.4)
599 ioports I/O port usage
600 irq Masks for irq to cpu affinity (2.4)(smp?)
601 isapnp ISA PnP (Plug&Play) Info (2.4)
602 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
603 kmsg Kernel messages
604 ksyms Kernel symbol table
605 loadavg Load average of last 1, 5 & 15 minutes
606 locks Kernel locks
607 meminfo Memory info
608 misc Miscellaneous
609 modules List of loaded modules
610 mounts Mounted filesystems
611 net Networking info (see text)
612 pagetypeinfo Additional page allocator information (see text) (2.5)
613 partitions Table of partitions known to the system
614 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
615 decoupled by lspci (2.4)
616 rtc Real time clock
617 scsi SCSI info (see text)
618 slabinfo Slab pool info
619 softirqs softirq usage
620 stat Overall statistics
621 swaps Swap space utilization
622 sys See chapter 2
623 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
624 tty Info of tty drivers
625 uptime Wall clock since boot, combined idle time of all cpus
626 version Kernel version
627 video bttv info of video resources (2.4)
628 vmallocinfo Show vmalloced areas
629..............................................................................
630
631You can, for example, check which interrupts are currently in use and what
632they are used for by looking in the file /proc/interrupts:
633
634 > cat /proc/interrupts
635 CPU0
636 0: 8728810 XT-PIC timer
637 1: 895 XT-PIC keyboard
638 2: 0 XT-PIC cascade
639 3: 531695 XT-PIC aha152x
640 4: 2014133 XT-PIC serial
641 5: 44401 XT-PIC pcnet_cs
642 8: 2 XT-PIC rtc
643 11: 8 XT-PIC i82365
644 12: 182918 XT-PIC PS/2 Mouse
645 13: 1 XT-PIC fpu
646 14: 1232265 XT-PIC ide0
647 15: 7 XT-PIC ide1
648 NMI: 0
649
650In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
651output of a SMP machine):
652
653 > cat /proc/interrupts
654
655 CPU0 CPU1
656 0: 1243498 1214548 IO-APIC-edge timer
657 1: 8949 8958 IO-APIC-edge keyboard
658 2: 0 0 XT-PIC cascade
659 5: 11286 10161 IO-APIC-edge soundblaster
660 8: 1 0 IO-APIC-edge rtc
661 9: 27422 27407 IO-APIC-edge 3c503
662 12: 113645 113873 IO-APIC-edge PS/2 Mouse
663 13: 0 0 XT-PIC fpu
664 14: 22491 24012 IO-APIC-edge ide0
665 15: 2183 2415 IO-APIC-edge ide1
666 17: 30564 30414 IO-APIC-level eth0
667 18: 177 164 IO-APIC-level bttv
668 NMI: 2457961 2457959
669 LOC: 2457882 2457881
670 ERR: 2155
671
672NMI is incremented in this case because every timer interrupt generates a NMI
673(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
674
675LOC is the local interrupt counter of the internal APIC of every CPU.
676
677ERR is incremented in the case of errors in the IO-APIC bus (the bus that
678connects the CPUs in a SMP system. This means that an error has been detected,
679the IO-APIC automatically retry the transmission, so it should not be a big
680problem, but you should read the SMP-FAQ.
681
682In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
683/proc/interrupts to display every IRQ vector in use by the system, not
684just those considered 'most important'. The new vectors are:
685
686 THR -- interrupt raised when a machine check threshold counter
687 (typically counting ECC corrected errors of memory or cache) exceeds
688 a configurable threshold. Only available on some systems.
689
690 TRM -- a thermal event interrupt occurs when a temperature threshold
691 has been exceeded for the CPU. This interrupt may also be generated
692 when the temperature drops back to normal.
693
694 SPU -- a spurious interrupt is some interrupt that was raised then lowered
695 by some IO device before it could be fully processed by the APIC. Hence
696 the APIC sees the interrupt but does not know what device it came from.
697 For this case the APIC will generate the interrupt with a IRQ vector
698 of 0xff. This might also be generated by chipset bugs.
699
700 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
701 sent from one CPU to another per the needs of the OS. Typically,
702 their statistics are used by kernel developers and interested users to
703 determine the occurrence of interrupts of the given type.
704
705The above IRQ vectors are displayed only when relevant. For example,
706the threshold vector does not exist on x86_64 platforms. Others are
707suppressed when the system is a uniprocessor. As of this writing, only
708i386 and x86_64 platforms support the new IRQ vector displays.
709
710Of some interest is the introduction of the /proc/irq directory to 2.4.
711It could be used to set IRQ to CPU affinity, this means that you can "hook" an
712IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
713irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
714prof_cpu_mask.
715
716For example
717 > ls /proc/irq/
718 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
719 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
720 > ls /proc/irq/0/
721 smp_affinity
722
723smp_affinity is a bitmask, in which you can specify which CPUs can handle the
724IRQ, you can set it by doing:
725
726 > echo 1 > /proc/irq/10/smp_affinity
727
728This means that only the first CPU will handle the IRQ, but you can also echo
7295 which means that only the first and third CPU can handle the IRQ.
730
731The contents of each smp_affinity file is the same by default:
732
733 > cat /proc/irq/0/smp_affinity
734 ffffffff
735
736There is an alternate interface, smp_affinity_list which allows specifying
737a cpu range instead of a bitmask:
738
739 > cat /proc/irq/0/smp_affinity_list
740 1024-1031
741
742The default_smp_affinity mask applies to all non-active IRQs, which are the
743IRQs which have not yet been allocated/activated, and hence which lack a
744/proc/irq/[0-9]* directory.
745
746The node file on an SMP system shows the node to which the device using the IRQ
747reports itself as being attached. This hardware locality information does not
748include information about any possible driver locality preference.
749
750prof_cpu_mask specifies which CPUs are to be profiled by the system wide
751profiler. Default value is ffffffff (all cpus if there are only 32 of them).
752
753The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
754between all the CPUs which are allowed to handle it. As usual the kernel has
755more info than you and does a better job than you, so the defaults are the
756best choice for almost everyone. [Note this applies only to those IO-APIC's
757that support "Round Robin" interrupt distribution.]
758
759There are three more important subdirectories in /proc: net, scsi, and sys.
760The general rule is that the contents, or even the existence of these
761directories, depend on your kernel configuration. If SCSI is not enabled, the
762directory scsi may not exist. The same is true with the net, which is there
763only when networking support is present in the running kernel.
764
765The slabinfo file gives information about memory usage at the slab level.
766Linux uses slab pools for memory management above page level in version 2.2.
767Commonly used objects have their own slab pool (such as network buffers,
768directory cache, and so on).
769
770..............................................................................
771
772> cat /proc/buddyinfo
773
774Node 0, zone DMA 0 4 5 4 4 3 ...
775Node 0, zone Normal 1 0 0 1 101 8 ...
776Node 0, zone HighMem 2 0 0 1 1 0 ...
777
778External fragmentation is a problem under some workloads, and buddyinfo is a
779useful tool for helping diagnose these problems. Buddyinfo will give you a
780clue as to how big an area you can safely allocate, or why a previous
781allocation failed.
782
783Each column represents the number of pages of a certain order which are
784available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
785ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
786available in ZONE_NORMAL, etc...
787
788More information relevant to external fragmentation can be found in
789pagetypeinfo.
790
791> cat /proc/pagetypeinfo
792Page block order: 9
793Pages per block: 512
794
795Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
796Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
797Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
798Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
799Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
800Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
801Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
802Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
803Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
804Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
805Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
806
807Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
808Node 0, zone DMA 2 0 5 1 0
809Node 0, zone DMA32 41 6 967 2 0
810
811Fragmentation avoidance in the kernel works by grouping pages of different
812migrate types into the same contiguous regions of memory called page blocks.
813A page block is typically the size of the default hugepage size e.g. 2MB on
814X86-64. By keeping pages grouped based on their ability to move, the kernel
815can reclaim pages within a page block to satisfy a high-order allocation.
816
817The pagetypinfo begins with information on the size of a page block. It
818then gives the same type of information as buddyinfo except broken down
819by migrate-type and finishes with details on how many page blocks of each
820type exist.
821
822If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
823from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
824make an estimate of the likely number of huge pages that can be allocated
825at a given point in time. All the "Movable" blocks should be allocatable
826unless memory has been mlock()'d. Some of the Reclaimable blocks should
827also be allocatable although a lot of filesystem metadata may have to be
828reclaimed to achieve this.
829
830..............................................................................
831
832meminfo:
833
834Provides information about distribution and utilization of memory. This
835varies by architecture and compile options. The following is from a
83616GB PIII, which has highmem enabled. You may not have all of these fields.
837
838> cat /proc/meminfo
839
840MemTotal: 16344972 kB
841MemFree: 13634064 kB
842MemAvailable: 14836172 kB
843Buffers: 3656 kB
844Cached: 1195708 kB
845SwapCached: 0 kB
846Active: 891636 kB
847Inactive: 1077224 kB
848HighTotal: 15597528 kB
849HighFree: 13629632 kB
850LowTotal: 747444 kB
851LowFree: 4432 kB
852SwapTotal: 0 kB
853SwapFree: 0 kB
854Dirty: 968 kB
855Writeback: 0 kB
856AnonPages: 861800 kB
857Mapped: 280372 kB
858Shmem: 644 kB
859Slab: 284364 kB
860SReclaimable: 159856 kB
861SUnreclaim: 124508 kB
862PageTables: 24448 kB
863NFS_Unstable: 0 kB
864Bounce: 0 kB
865WritebackTmp: 0 kB
866CommitLimit: 7669796 kB
867Committed_AS: 100056 kB
868VmallocTotal: 112216 kB
869VmallocUsed: 428 kB
870VmallocChunk: 111088 kB
871AnonHugePages: 49152 kB
872ShmemHugePages: 0 kB
873ShmemPmdMapped: 0 kB
874
875
876 MemTotal: Total usable ram (i.e. physical ram minus a few reserved
877 bits and the kernel binary code)
878 MemFree: The sum of LowFree+HighFree
879MemAvailable: An estimate of how much memory is available for starting new
880 applications, without swapping. Calculated from MemFree,
881 SReclaimable, the size of the file LRU lists, and the low
882 watermarks in each zone.
883 The estimate takes into account that the system needs some
884 page cache to function well, and that not all reclaimable
885 slab will be reclaimable, due to items being in use. The
886 impact of those factors will vary from system to system.
887 Buffers: Relatively temporary storage for raw disk blocks
888 shouldn't get tremendously large (20MB or so)
889 Cached: in-memory cache for files read from the disk (the
890 pagecache). Doesn't include SwapCached
891 SwapCached: Memory that once was swapped out, is swapped back in but
892 still also is in the swapfile (if memory is needed it
893 doesn't need to be swapped out AGAIN because it is already
894 in the swapfile. This saves I/O)
895 Active: Memory that has been used more recently and usually not
896 reclaimed unless absolutely necessary.
897 Inactive: Memory which has been less recently used. It is more
898 eligible to be reclaimed for other purposes
899 HighTotal:
900 HighFree: Highmem is all memory above ~860MB of physical memory
901 Highmem areas are for use by userspace programs, or
902 for the pagecache. The kernel must use tricks to access
903 this memory, making it slower to access than lowmem.
904 LowTotal:
905 LowFree: Lowmem is memory which can be used for everything that
906 highmem can be used for, but it is also available for the
907 kernel's use for its own data structures. Among many
908 other things, it is where everything from the Slab is
909 allocated. Bad things happen when you're out of lowmem.
910 SwapTotal: total amount of swap space available
911 SwapFree: Memory which has been evicted from RAM, and is temporarily
912 on the disk
913 Dirty: Memory which is waiting to get written back to the disk
914 Writeback: Memory which is actively being written back to the disk
915 AnonPages: Non-file backed pages mapped into userspace page tables
916AnonHugePages: Non-file backed huge pages mapped into userspace page tables
917 Mapped: files which have been mmaped, such as libraries
918 Shmem: Total memory used by shared memory (shmem) and tmpfs
919ShmemHugePages: Memory used by shared memory (shmem) and tmpfs allocated
920 with huge pages
921ShmemPmdMapped: Shared memory mapped into userspace with huge pages
922 Slab: in-kernel data structures cache
923SReclaimable: Part of Slab, that might be reclaimed, such as caches
924 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
925 PageTables: amount of memory dedicated to the lowest level of page
926 tables.
927NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
928 storage
929 Bounce: Memory used for block device "bounce buffers"
930WritebackTmp: Memory used by FUSE for temporary writeback buffers
931 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
932 this is the total amount of memory currently available to
933 be allocated on the system. This limit is only adhered to
934 if strict overcommit accounting is enabled (mode 2 in
935 'vm.overcommit_memory').
936 The CommitLimit is calculated with the following formula:
937 CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
938 overcommit_ratio / 100 + [total swap pages]
939 For example, on a system with 1G of physical RAM and 7G
940 of swap with a `vm.overcommit_ratio` of 30 it would
941 yield a CommitLimit of 7.3G.
942 For more details, see the memory overcommit documentation
943 in vm/overcommit-accounting.
944Committed_AS: The amount of memory presently allocated on the system.
945 The committed memory is a sum of all of the memory which
946 has been allocated by processes, even if it has not been
947 "used" by them as of yet. A process which malloc()'s 1G
948 of memory, but only touches 300M of it will show up as
949 using 1G. This 1G is memory which has been "committed" to
950 by the VM and can be used at any time by the allocating
951 application. With strict overcommit enabled on the system
952 (mode 2 in 'vm.overcommit_memory'),allocations which would
953 exceed the CommitLimit (detailed above) will not be permitted.
954 This is useful if one needs to guarantee that processes will
955 not fail due to lack of memory once that memory has been
956 successfully allocated.
957VmallocTotal: total size of vmalloc memory area
958 VmallocUsed: amount of vmalloc area which is used
959VmallocChunk: largest contiguous block of vmalloc area which is free
960
961..............................................................................
962
963vmallocinfo:
964
965Provides information about vmalloced/vmaped areas. One line per area,
966containing the virtual address range of the area, size in bytes,
967caller information of the creator, and optional information depending
968on the kind of area :
969
970 pages=nr number of pages
971 phys=addr if a physical address was specified
972 ioremap I/O mapping (ioremap() and friends)
973 vmalloc vmalloc() area
974 vmap vmap()ed pages
975 user VM_USERMAP area
976 vpages buffer for pages pointers was vmalloced (huge area)
977 N<node>=nr (Only on NUMA kernels)
978 Number of pages allocated on memory node <node>
979
980> cat /proc/vmallocinfo
9810xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
982 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
9830xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
984 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
9850xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
986 phys=7fee8000 ioremap
9870xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
988 phys=7fee7000 ioremap
9890xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
9900xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
991 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
9920xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
993 pages=2 vmalloc N1=2
9940xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
995 /0x130 [x_tables] pages=4 vmalloc N0=4
9960xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
997 pages=14 vmalloc N2=14
9980xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
999 pages=4 vmalloc N1=4
10000xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
1001 pages=2 vmalloc N1=2
10020xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
1003 pages=10 vmalloc N0=10
1004
1005..............................................................................
1006
1007softirqs:
1008
1009Provides counts of softirq handlers serviced since boot time, for each cpu.
1010
1011> cat /proc/softirqs
1012 CPU0 CPU1 CPU2 CPU3
1013 HI: 0 0 0 0
1014 TIMER: 27166 27120 27097 27034
1015 NET_TX: 0 0 0 17
1016 NET_RX: 42 0 0 39
1017 BLOCK: 0 0 107 1121
1018 TASKLET: 0 0 0 290
1019 SCHED: 27035 26983 26971 26746
1020 HRTIMER: 0 0 0 0
1021 RCU: 1678 1769 2178 2250
1022
1023
10241.3 IDE devices in /proc/ide
1025----------------------------
1026
1027The subdirectory /proc/ide contains information about all IDE devices of which
1028the kernel is aware. There is one subdirectory for each IDE controller, the
1029file drivers and a link for each IDE device, pointing to the device directory
1030in the controller specific subtree.
1031
1032The file drivers contains general information about the drivers used for the
1033IDE devices:
1034
1035 > cat /proc/ide/drivers
1036 ide-cdrom version 4.53
1037 ide-disk version 1.08
1038
1039More detailed information can be found in the controller specific
1040subdirectories. These are named ide0, ide1 and so on. Each of these
1041directories contains the files shown in table 1-6.
1042
1043
1044Table 1-6: IDE controller info in /proc/ide/ide?
1045..............................................................................
1046 File Content
1047 channel IDE channel (0 or 1)
1048 config Configuration (only for PCI/IDE bridge)
1049 mate Mate name
1050 model Type/Chipset of IDE controller
1051..............................................................................
1052
1053Each device connected to a controller has a separate subdirectory in the
1054controllers directory. The files listed in table 1-7 are contained in these
1055directories.
1056
1057
1058Table 1-7: IDE device information
1059..............................................................................
1060 File Content
1061 cache The cache
1062 capacity Capacity of the medium (in 512Byte blocks)
1063 driver driver and version
1064 geometry physical and logical geometry
1065 identify device identify block
1066 media media type
1067 model device identifier
1068 settings device setup
1069 smart_thresholds IDE disk management thresholds
1070 smart_values IDE disk management values
1071..............................................................................
1072
1073The most interesting file is settings. This file contains a nice overview of
1074the drive parameters:
1075
1076 # cat /proc/ide/ide0/hda/settings
1077 name value min max mode
1078 ---- ----- --- --- ----
1079 bios_cyl 526 0 65535 rw
1080 bios_head 255 0 255 rw
1081 bios_sect 63 0 63 rw
1082 breada_readahead 4 0 127 rw
1083 bswap 0 0 1 r
1084 file_readahead 72 0 2097151 rw
1085 io_32bit 0 0 3 rw
1086 keepsettings 0 0 1 rw
1087 max_kb_per_request 122 1 127 rw
1088 multcount 0 0 8 rw
1089 nice1 1 0 1 rw
1090 nowerr 0 0 1 rw
1091 pio_mode write-only 0 255 w
1092 slow 0 0 1 rw
1093 unmaskirq 0 0 1 rw
1094 using_dma 0 0 1 rw
1095
1096
10971.4 Networking info in /proc/net
1098--------------------------------
1099
1100The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
1101additional values you get for IP version 6 if you configure the kernel to
1102support this. Table 1-9 lists the files and their meaning.
1103
1104
1105Table 1-8: IPv6 info in /proc/net
1106..............................................................................
1107 File Content
1108 udp6 UDP sockets (IPv6)
1109 tcp6 TCP sockets (IPv6)
1110 raw6 Raw device statistics (IPv6)
1111 igmp6 IP multicast addresses, which this host joined (IPv6)
1112 if_inet6 List of IPv6 interface addresses
1113 ipv6_route Kernel routing table for IPv6
1114 rt6_stats Global IPv6 routing tables statistics
1115 sockstat6 Socket statistics (IPv6)
1116 snmp6 Snmp data (IPv6)
1117..............................................................................
1118
1119
1120Table 1-9: Network info in /proc/net
1121..............................................................................
1122 File Content
1123 arp Kernel ARP table
1124 dev network devices with statistics
1125 dev_mcast the Layer2 multicast groups a device is listening too
1126 (interface index, label, number of references, number of bound
1127 addresses).
1128 dev_stat network device status
1129 ip_fwchains Firewall chain linkage
1130 ip_fwnames Firewall chain names
1131 ip_masq Directory containing the masquerading tables
1132 ip_masquerade Major masquerading table
1133 netstat Network statistics
1134 raw raw device statistics
1135 route Kernel routing table
1136 rpc Directory containing rpc info
1137 rt_cache Routing cache
1138 snmp SNMP data
1139 sockstat Socket statistics
1140 tcp TCP sockets
1141 udp UDP sockets
1142 unix UNIX domain sockets
1143 wireless Wireless interface data (Wavelan etc)
1144 igmp IP multicast addresses, which this host joined
1145 psched Global packet scheduler parameters.
1146 netlink List of PF_NETLINK sockets
1147 ip_mr_vifs List of multicast virtual interfaces
1148 ip_mr_cache List of multicast routing cache
1149..............................................................................
1150
1151You can use this information to see which network devices are available in
1152your system and how much traffic was routed over those devices:
1153
1154 > cat /proc/net/dev
1155 Inter-|Receive |[...
1156 face |bytes packets errs drop fifo frame compressed multicast|[...
1157 lo: 908188 5596 0 0 0 0 0 0 [...
1158 ppp0:15475140 20721 410 0 0 410 0 0 [...
1159 eth0: 614530 7085 0 0 0 0 0 1 [...
1160
1161 ...] Transmit
1162 ...] bytes packets errs drop fifo colls carrier compressed
1163 ...] 908188 5596 0 0 0 0 0 0
1164 ...] 1375103 17405 0 0 0 0 0 0
1165 ...] 1703981 5535 0 0 0 3 0 0
1166
1167In addition, each Channel Bond interface has its own directory. For
1168example, the bond0 device will have a directory called /proc/net/bond0/.
1169It will contain information that is specific to that bond, such as the
1170current slaves of the bond, the link status of the slaves, and how
1171many times the slaves link has failed.
1172
11731.5 SCSI info
1174-------------
1175
1176If you have a SCSI host adapter in your system, you'll find a subdirectory
1177named after the driver for this adapter in /proc/scsi. You'll also see a list
1178of all recognized SCSI devices in /proc/scsi:
1179
1180 >cat /proc/scsi/scsi
1181 Attached devices:
1182 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1183 Vendor: IBM Model: DGHS09U Rev: 03E0
1184 Type: Direct-Access ANSI SCSI revision: 03
1185 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1186 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1187 Type: CD-ROM ANSI SCSI revision: 02
1188
1189
1190The directory named after the driver has one file for each adapter found in
1191the system. These files contain information about the controller, including
1192the used IRQ and the IO address range. The amount of information shown is
1193dependent on the adapter you use. The example shows the output for an Adaptec
1194AHA-2940 SCSI adapter:
1195
1196 > cat /proc/scsi/aic7xxx/0
1197
1198 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1199 Compile Options:
1200 TCQ Enabled By Default : Disabled
1201 AIC7XXX_PROC_STATS : Disabled
1202 AIC7XXX_RESET_DELAY : 5
1203 Adapter Configuration:
1204 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1205 Ultra Wide Controller
1206 PCI MMAPed I/O Base: 0xeb001000
1207 Adapter SEEPROM Config: SEEPROM found and used.
1208 Adaptec SCSI BIOS: Enabled
1209 IRQ: 10
1210 SCBs: Active 0, Max Active 2,
1211 Allocated 15, HW 16, Page 255
1212 Interrupts: 160328
1213 BIOS Control Word: 0x18b6
1214 Adapter Control Word: 0x005b
1215 Extended Translation: Enabled
1216 Disconnect Enable Flags: 0xffff
1217 Ultra Enable Flags: 0x0001
1218 Tag Queue Enable Flags: 0x0000
1219 Ordered Queue Tag Flags: 0x0000
1220 Default Tag Queue Depth: 8
1221 Tagged Queue By Device array for aic7xxx host instance 0:
1222 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1223 Actual queue depth per device for aic7xxx host instance 0:
1224 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1225 Statistics:
1226 (scsi0:0:0:0)
1227 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1228 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1229 Total transfers 160151 (74577 reads and 85574 writes)
1230 (scsi0:0:6:0)
1231 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1232 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1233 Total transfers 0 (0 reads and 0 writes)
1234
1235
12361.6 Parallel port info in /proc/parport
1237---------------------------------------
1238
1239The directory /proc/parport contains information about the parallel ports of
1240your system. It has one subdirectory for each port, named after the port
1241number (0,1,2,...).
1242
1243These directories contain the four files shown in Table 1-10.
1244
1245
1246Table 1-10: Files in /proc/parport
1247..............................................................................
1248 File Content
1249 autoprobe Any IEEE-1284 device ID information that has been acquired.
1250 devices list of the device drivers using that port. A + will appear by the
1251 name of the device currently using the port (it might not appear
1252 against any).
1253 hardware Parallel port's base address, IRQ line and DMA channel.
1254 irq IRQ that parport is using for that port. This is in a separate
1255 file to allow you to alter it by writing a new value in (IRQ
1256 number or none).
1257..............................................................................
1258
12591.7 TTY info in /proc/tty
1260-------------------------
1261
1262Information about the available and actually used tty's can be found in the
1263directory /proc/tty.You'll find entries for drivers and line disciplines in
1264this directory, as shown in Table 1-11.
1265
1266
1267Table 1-11: Files in /proc/tty
1268..............................................................................
1269 File Content
1270 drivers list of drivers and their usage
1271 ldiscs registered line disciplines
1272 driver/serial usage statistic and status of single tty lines
1273..............................................................................
1274
1275To see which tty's are currently in use, you can simply look into the file
1276/proc/tty/drivers:
1277
1278 > cat /proc/tty/drivers
1279 pty_slave /dev/pts 136 0-255 pty:slave
1280 pty_master /dev/ptm 128 0-255 pty:master
1281 pty_slave /dev/ttyp 3 0-255 pty:slave
1282 pty_master /dev/pty 2 0-255 pty:master
1283 serial /dev/cua 5 64-67 serial:callout
1284 serial /dev/ttyS 4 64-67 serial
1285 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1286 /dev/ptmx /dev/ptmx 5 2 system
1287 /dev/console /dev/console 5 1 system:console
1288 /dev/tty /dev/tty 5 0 system:/dev/tty
1289 unknown /dev/tty 4 1-63 console
1290
1291
12921.8 Miscellaneous kernel statistics in /proc/stat
1293-------------------------------------------------
1294
1295Various pieces of information about kernel activity are available in the
1296/proc/stat file. All of the numbers reported in this file are aggregates
1297since the system first booted. For a quick look, simply cat the file:
1298
1299 > cat /proc/stat
1300 cpu 2255 34 2290 22625563 6290 127 456 0 0 0
1301 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1302 cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1303 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1304 ctxt 1990473
1305 btime 1062191376
1306 processes 2915
1307 procs_running 1
1308 procs_blocked 0
1309 softirq 183433 0 21755 12 39 1137 231 21459 2263
1310
1311The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1312lines. These numbers identify the amount of time the CPU has spent performing
1313different kinds of work. Time units are in USER_HZ (typically hundredths of a
1314second). The meanings of the columns are as follows, from left to right:
1315
1316- user: normal processes executing in user mode
1317- nice: niced processes executing in user mode
1318- system: processes executing in kernel mode
1319- idle: twiddling thumbs
1320- iowait: In a word, iowait stands for waiting for I/O to complete. But there
1321 are several problems:
1322 1. Cpu will not wait for I/O to complete, iowait is the time that a task is
1323 waiting for I/O to complete. When cpu goes into idle state for
1324 outstanding task io, another task will be scheduled on this CPU.
1325 2. In a multi-core CPU, the task waiting for I/O to complete is not running
1326 on any CPU, so the iowait of each CPU is difficult to calculate.
1327 3. The value of iowait field in /proc/stat will decrease in certain
1328 conditions.
1329 So, the iowait is not reliable by reading from /proc/stat.
1330- irq: servicing interrupts
1331- softirq: servicing softirqs
1332- steal: involuntary wait
1333- guest: running a normal guest
1334- guest_nice: running a niced guest
1335
1336The "intr" line gives counts of interrupts serviced since boot time, for each
1337of the possible system interrupts. The first column is the total of all
1338interrupts serviced including unnumbered architecture specific interrupts;
1339each subsequent column is the total for that particular numbered interrupt.
1340Unnumbered interrupts are not shown, only summed into the total.
1341
1342The "ctxt" line gives the total number of context switches across all CPUs.
1343
1344The "btime" line gives the time at which the system booted, in seconds since
1345the Unix epoch.
1346
1347The "processes" line gives the number of processes and threads created, which
1348includes (but is not limited to) those created by calls to the fork() and
1349clone() system calls.
1350
1351The "procs_running" line gives the total number of threads that are
1352running or ready to run (i.e., the total number of runnable threads).
1353
1354The "procs_blocked" line gives the number of processes currently blocked,
1355waiting for I/O to complete.
1356
1357The "softirq" line gives counts of softirqs serviced since boot time, for each
1358of the possible system softirqs. The first column is the total of all
1359softirqs serviced; each subsequent column is the total for that particular
1360softirq.
1361
1362
13631.9 Ext4 file system parameters
1364-------------------------------
1365
1366Information about mounted ext4 file systems can be found in
1367/proc/fs/ext4. Each mounted filesystem will have a directory in
1368/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1369/proc/fs/ext4/dm-0). The files in each per-device directory are shown
1370in Table 1-12, below.
1371
1372Table 1-12: Files in /proc/fs/ext4/<devname>
1373..............................................................................
1374 File Content
1375 mb_groups details of multiblock allocator buddy cache of free blocks
1376..............................................................................
1377
13782.0 /proc/consoles
1379------------------
1380Shows registered system console lines.
1381
1382To see which character device lines are currently used for the system console
1383/dev/console, you may simply look into the file /proc/consoles:
1384
1385 > cat /proc/consoles
1386 tty0 -WU (ECp) 4:7
1387 ttyS0 -W- (Ep) 4:64
1388
1389The columns are:
1390
1391 device name of the device
1392 operations R = can do read operations
1393 W = can do write operations
1394 U = can do unblank
1395 flags E = it is enabled
1396 C = it is preferred console
1397 B = it is primary boot console
1398 p = it is used for printk buffer
1399 b = it is not a TTY but a Braille device
1400 a = it is safe to use when cpu is offline
1401 major:minor major and minor number of the device separated by a colon
1402
1403------------------------------------------------------------------------------
1404Summary
1405------------------------------------------------------------------------------
1406The /proc file system serves information about the running system. It not only
1407allows access to process data but also allows you to request the kernel status
1408by reading files in the hierarchy.
1409
1410The directory structure of /proc reflects the types of information and makes
1411it easy, if not obvious, where to look for specific data.
1412------------------------------------------------------------------------------
1413
1414------------------------------------------------------------------------------
1415CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1416------------------------------------------------------------------------------
1417
1418------------------------------------------------------------------------------
1419In This Chapter
1420------------------------------------------------------------------------------
1421* Modifying kernel parameters by writing into files found in /proc/sys
1422* Exploring the files which modify certain parameters
1423* Review of the /proc/sys file tree
1424------------------------------------------------------------------------------
1425
1426
1427A very interesting part of /proc is the directory /proc/sys. This is not only
1428a source of information, it also allows you to change parameters within the
1429kernel. Be very careful when attempting this. You can optimize your system,
1430but you can also cause it to crash. Never alter kernel parameters on a
1431production system. Set up a development machine and test to make sure that
1432everything works the way you want it to. You may have no alternative but to
1433reboot the machine once an error has been made.
1434
1435To change a value, simply echo the new value into the file. An example is
1436given below in the section on the file system data. You need to be root to do
1437this. You can create your own boot script to perform this every time your
1438system boots.
1439
1440The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1441general things in the operation of the Linux kernel. Since some of the files
1442can inadvertently disrupt your system, it is advisable to read both
1443documentation and source before actually making adjustments. In any case, be
1444very careful when writing to any of these files. The entries in /proc may
1445change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1446review the kernel documentation in the directory /usr/src/linux/Documentation.
1447This chapter is heavily based on the documentation included in the pre 2.2
1448kernels, and became part of it in version 2.2.1 of the Linux kernel.
1449
1450Please see: Documentation/sysctl/ directory for descriptions of these
1451entries.
1452
1453------------------------------------------------------------------------------
1454Summary
1455------------------------------------------------------------------------------
1456Certain aspects of kernel behavior can be modified at runtime, without the
1457need to recompile the kernel, or even to reboot the system. The files in the
1458/proc/sys tree can not only be read, but also modified. You can use the echo
1459command to write value into these files, thereby changing the default settings
1460of the kernel.
1461------------------------------------------------------------------------------
1462
1463------------------------------------------------------------------------------
1464CHAPTER 3: PER-PROCESS PARAMETERS
1465------------------------------------------------------------------------------
1466
14673.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1468--------------------------------------------------------------------------------
1469
1470These file can be used to adjust the badness heuristic used to select which
1471process gets killed in out of memory conditions.
1472
1473The badness heuristic assigns a value to each candidate task ranging from 0
1474(never kill) to 1000 (always kill) to determine which process is targeted. The
1475units are roughly a proportion along that range of allowed memory the process
1476may allocate from based on an estimation of its current memory and swap use.
1477For example, if a task is using all allowed memory, its badness score will be
14781000. If it is using half of its allowed memory, its score will be 500.
1479
1480There is an additional factor included in the badness score: the current memory
1481and swap usage is discounted by 3% for root processes.
1482
1483The amount of "allowed" memory depends on the context in which the oom killer
1484was called. If it is due to the memory assigned to the allocating task's cpuset
1485being exhausted, the allowed memory represents the set of mems assigned to that
1486cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1487memory represents the set of mempolicy nodes. If it is due to a memory
1488limit (or swap limit) being reached, the allowed memory is that configured
1489limit. Finally, if it is due to the entire system being out of memory, the
1490allowed memory represents all allocatable resources.
1491
1492The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1493is used to determine which task to kill. Acceptable values range from -1000
1494(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1495polarize the preference for oom killing either by always preferring a certain
1496task or completely disabling it. The lowest possible value, -1000, is
1497equivalent to disabling oom killing entirely for that task since it will always
1498report a badness score of 0.
1499
1500Consequently, it is very simple for userspace to define the amount of memory to
1501consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1502example, is roughly equivalent to allowing the remainder of tasks sharing the
1503same system, cpuset, mempolicy, or memory controller resources to use at least
150450% more memory. A value of -500, on the other hand, would be roughly
1505equivalent to discounting 50% of the task's allowed memory from being considered
1506as scoring against the task.
1507
1508For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1509be used to tune the badness score. Its acceptable values range from -16
1510(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1511(OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1512scaled linearly with /proc/<pid>/oom_score_adj.
1513
1514The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1515value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1516requires CAP_SYS_RESOURCE.
1517
1518Caveat: when a parent task is selected, the oom killer will sacrifice any first
1519generation children with separate address spaces instead, if possible. This
1520avoids servers and important system daemons from being killed and loses the
1521minimal amount of work.
1522
1523
15243.2 /proc/<pid>/oom_score - Display current oom-killer score
1525-------------------------------------------------------------
1526
1527This file can be used to check the current score used by the oom-killer is for
1528any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1529process should be killed in an out-of-memory situation.
1530
1531
15323.3 /proc/<pid>/io - Display the IO accounting fields
1533-------------------------------------------------------
1534
1535This file contains IO statistics for each running process
1536
1537Example
1538-------
1539
1540test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1541[1] 3828
1542
1543test:/tmp # cat /proc/3828/io
1544rchar: 323934931
1545wchar: 323929600
1546syscr: 632687
1547syscw: 632675
1548read_bytes: 0
1549write_bytes: 323932160
1550cancelled_write_bytes: 0
1551
1552
1553Description
1554-----------
1555
1556rchar
1557-----
1558
1559I/O counter: chars read
1560The number of bytes which this task has caused to be read from storage. This
1561is simply the sum of bytes which this process passed to read() and pread().
1562It includes things like tty IO and it is unaffected by whether or not actual
1563physical disk IO was required (the read might have been satisfied from
1564pagecache)
1565
1566
1567wchar
1568-----
1569
1570I/O counter: chars written
1571The number of bytes which this task has caused, or shall cause to be written
1572to disk. Similar caveats apply here as with rchar.
1573
1574
1575syscr
1576-----
1577
1578I/O counter: read syscalls
1579Attempt to count the number of read I/O operations, i.e. syscalls like read()
1580and pread().
1581
1582
1583syscw
1584-----
1585
1586I/O counter: write syscalls
1587Attempt to count the number of write I/O operations, i.e. syscalls like
1588write() and pwrite().
1589
1590
1591read_bytes
1592----------
1593
1594I/O counter: bytes read
1595Attempt to count the number of bytes which this process really did cause to
1596be fetched from the storage layer. Done at the submit_bio() level, so it is
1597accurate for block-backed filesystems. <please add status regarding NFS and
1598CIFS at a later time>
1599
1600
1601write_bytes
1602-----------
1603
1604I/O counter: bytes written
1605Attempt to count the number of bytes which this process caused to be sent to
1606the storage layer. This is done at page-dirtying time.
1607
1608
1609cancelled_write_bytes
1610---------------------
1611
1612The big inaccuracy here is truncate. If a process writes 1MB to a file and
1613then deletes the file, it will in fact perform no writeout. But it will have
1614been accounted as having caused 1MB of write.
1615In other words: The number of bytes which this process caused to not happen,
1616by truncating pagecache. A task can cause "negative" IO too. If this task
1617truncates some dirty pagecache, some IO which another task has been accounted
1618for (in its write_bytes) will not be happening. We _could_ just subtract that
1619from the truncating task's write_bytes, but there is information loss in doing
1620that.
1621
1622
1623Note
1624----
1625
1626At its current implementation state, this is a bit racy on 32-bit machines: if
1627process A reads process B's /proc/pid/io while process B is updating one of
1628those 64-bit counters, process A could see an intermediate result.
1629
1630
1631More information about this can be found within the taskstats documentation in
1632Documentation/accounting.
1633
16343.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1635---------------------------------------------------------------
1636When a process is dumped, all anonymous memory is written to a core file as
1637long as the size of the core file isn't limited. But sometimes we don't want
1638to dump some memory segments, for example, huge shared memory or DAX.
1639Conversely, sometimes we want to save file-backed memory segments into a core
1640file, not only the individual files.
1641
1642/proc/<pid>/coredump_filter allows you to customize which memory segments
1643will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1644of memory types. If a bit of the bitmask is set, memory segments of the
1645corresponding memory type are dumped, otherwise they are not dumped.
1646
1647The following 9 memory types are supported:
1648 - (bit 0) anonymous private memory
1649 - (bit 1) anonymous shared memory
1650 - (bit 2) file-backed private memory
1651 - (bit 3) file-backed shared memory
1652 - (bit 4) ELF header pages in file-backed private memory areas (it is
1653 effective only if the bit 2 is cleared)
1654 - (bit 5) hugetlb private memory
1655 - (bit 6) hugetlb shared memory
1656 - (bit 7) DAX private memory
1657 - (bit 8) DAX shared memory
1658
1659 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1660 are always dumped regardless of the bitmask status.
1661
1662 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
1663 only affected by bit 5-6, and DAX is only affected by bits 7-8.
1664
1665The default value of coredump_filter is 0x33; this means all anonymous memory
1666segments, ELF header pages and hugetlb private memory are dumped.
1667
1668If you don't want to dump all shared memory segments attached to pid 1234,
1669write 0x31 to the process's proc file.
1670
1671 $ echo 0x31 > /proc/1234/coredump_filter
1672
1673When a new process is created, the process inherits the bitmask status from its
1674parent. It is useful to set up coredump_filter before the program runs.
1675For example:
1676
1677 $ echo 0x7 > /proc/self/coredump_filter
1678 $ ./some_program
1679
16803.5 /proc/<pid>/mountinfo - Information about mounts
1681--------------------------------------------------------
1682
1683This file contains lines of the form:
1684
168536 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1686(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1687
1688(1) mount ID: unique identifier of the mount (may be reused after umount)
1689(2) parent ID: ID of parent (or of self for the top of the mount tree)
1690(3) major:minor: value of st_dev for files on filesystem
1691(4) root: root of the mount within the filesystem
1692(5) mount point: mount point relative to the process's root
1693(6) mount options: per mount options
1694(7) optional fields: zero or more fields of the form "tag[:value]"
1695(8) separator: marks the end of the optional fields
1696(9) filesystem type: name of filesystem of the form "type[.subtype]"
1697(10) mount source: filesystem specific information or "none"
1698(11) super options: per super block options
1699
1700Parsers should ignore all unrecognised optional fields. Currently the
1701possible optional fields are:
1702
1703shared:X mount is shared in peer group X
1704master:X mount is slave to peer group X
1705propagate_from:X mount is slave and receives propagation from peer group X (*)
1706unbindable mount is unbindable
1707
1708(*) X is the closest dominant peer group under the process's root. If
1709X is the immediate master of the mount, or if there's no dominant peer
1710group under the same root, then only the "master:X" field is present
1711and not the "propagate_from:X" field.
1712
1713For more information on mount propagation see:
1714
1715 Documentation/filesystems/sharedsubtree.txt
1716
1717
17183.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1719--------------------------------------------------------
1720These files provide a method to access a tasks comm value. It also allows for
1721a task to set its own or one of its thread siblings comm value. The comm value
1722is limited in size compared to the cmdline value, so writing anything longer
1723then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1724comm value.
1725
1726
17273.7 /proc/<pid>/task/<tid>/children - Information about task children
1728-------------------------------------------------------------------------
1729This file provides a fast way to retrieve first level children pids
1730of a task pointed by <pid>/<tid> pair. The format is a space separated
1731stream of pids.
1732
1733Note the "first level" here -- if a child has own children they will
1734not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1735to obtain the descendants.
1736
1737Since this interface is intended to be fast and cheap it doesn't
1738guarantee to provide precise results and some children might be
1739skipped, especially if they've exited right after we printed their
1740pids, so one need to either stop or freeze processes being inspected
1741if precise results are needed.
1742
1743
17443.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
1745---------------------------------------------------------------
1746This file provides information associated with an opened file. The regular
1747files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1748represents the current offset of the opened file in decimal form [see lseek(2)
1749for details], 'flags' denotes the octal O_xxx mask the file has been
1750created with [see open(2) for details] and 'mnt_id' represents mount ID of
1751the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1752for details].
1753
1754A typical output is
1755
1756 pos: 0
1757 flags: 0100002
1758 mnt_id: 19
1759
1760All locks associated with a file descriptor are shown in its fdinfo too.
1761
1762lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF
1763
1764The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1765pair provide additional information particular to the objects they represent.
1766
1767 Eventfd files
1768 ~~~~~~~~~~~~~
1769 pos: 0
1770 flags: 04002
1771 mnt_id: 9
1772 eventfd-count: 5a
1773
1774 where 'eventfd-count' is hex value of a counter.
1775
1776 Signalfd files
1777 ~~~~~~~~~~~~~~
1778 pos: 0
1779 flags: 04002
1780 mnt_id: 9
1781 sigmask: 0000000000000200
1782
1783 where 'sigmask' is hex value of the signal mask associated
1784 with a file.
1785
1786 Epoll files
1787 ~~~~~~~~~~~
1788 pos: 0
1789 flags: 02
1790 mnt_id: 9
1791 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7
1792
1793 where 'tfd' is a target file descriptor number in decimal form,
1794 'events' is events mask being watched and the 'data' is data
1795 associated with a target [see epoll(7) for more details].
1796
1797 The 'pos' is current offset of the target file in decimal form
1798 [see lseek(2)], 'ino' and 'sdev' are inode and device numbers
1799 where target file resides, all in hex format.
1800
1801 Fsnotify files
1802 ~~~~~~~~~~~~~~
1803 For inotify files the format is the following
1804
1805 pos: 0
1806 flags: 02000000
1807 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1808
1809 where 'wd' is a watch descriptor in decimal form, ie a target file
1810 descriptor number, 'ino' and 'sdev' are inode and device where the
1811 target file resides and the 'mask' is the mask of events, all in hex
1812 form [see inotify(7) for more details].
1813
1814 If the kernel was built with exportfs support, the path to the target
1815 file is encoded as a file handle. The file handle is provided by three
1816 fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1817 format.
1818
1819 If the kernel is built without exportfs support the file handle won't be
1820 printed out.
1821
1822 If there is no inotify mark attached yet the 'inotify' line will be omitted.
1823
1824 For fanotify files the format is
1825
1826 pos: 0
1827 flags: 02
1828 mnt_id: 9
1829 fanotify flags:10 event-flags:0
1830 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1831 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1832
1833 where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1834 call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1835 flags associated with mark which are tracked separately from events
1836 mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1837 mask and 'ignored_mask' is the mask of events which are to be ignored.
1838 All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1839 does provide information about flags and mask used in fanotify_mark
1840 call [see fsnotify manpage for details].
1841
1842 While the first three lines are mandatory and always printed, the rest is
1843 optional and may be omitted if no marks created yet.
1844
1845 Timerfd files
1846 ~~~~~~~~~~~~~
1847
1848 pos: 0
1849 flags: 02
1850 mnt_id: 9
1851 clockid: 0
1852 ticks: 0
1853 settime flags: 01
1854 it_value: (0, 49406829)
1855 it_interval: (1, 0)
1856
1857 where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
1858 that have occurred [see timerfd_create(2) for details]. 'settime flags' are
1859 flags in octal form been used to setup the timer [see timerfd_settime(2) for
1860 details]. 'it_value' is remaining time until the timer exiration.
1861 'it_interval' is the interval for the timer. Note the timer might be set up
1862 with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
1863 still exhibits timer's remaining time.
1864
18653.9 /proc/<pid>/map_files - Information about memory mapped files
1866---------------------------------------------------------------------
1867This directory contains symbolic links which represent memory mapped files
1868the process is maintaining. Example output:
1869
1870 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
1871 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
1872 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
1873 | ...
1874 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
1875 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
1876
1877The name of a link represents the virtual memory bounds of a mapping, i.e.
1878vm_area_struct::vm_start-vm_area_struct::vm_end.
1879
1880The main purpose of the map_files is to retrieve a set of memory mapped
1881files in a fast way instead of parsing /proc/<pid>/maps or
1882/proc/<pid>/smaps, both of which contain many more records. At the same
1883time one can open(2) mappings from the listings of two processes and
1884comparing their inode numbers to figure out which anonymous memory areas
1885are actually shared.
1886
18873.10 /proc/<pid>/timerslack_ns - Task timerslack value
1888---------------------------------------------------------
1889This file provides the value of the task's timerslack value in nanoseconds.
1890This value specifies a amount of time that normal timers may be deferred
1891in order to coalesce timers and avoid unnecessary wakeups.
1892
1893This allows a task's interactivity vs power consumption trade off to be
1894adjusted.
1895
1896Writing 0 to the file will set the tasks timerslack to the default value.
1897
1898Valid values are from 0 - ULLONG_MAX
1899
1900An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
1901permissions on the task specified to change its timerslack_ns value.
1902
19033.11 /proc/<pid>/patch_state - Livepatch patch operation state
1904-----------------------------------------------------------------
1905When CONFIG_LIVEPATCH is enabled, this file displays the value of the
1906patch state for the task.
1907
1908A value of '-1' indicates that no patch is in transition.
1909
1910A value of '0' indicates that a patch is in transition and the task is
1911unpatched. If the patch is being enabled, then the task hasn't been
1912patched yet. If the patch is being disabled, then the task has already
1913been unpatched.
1914
1915A value of '1' indicates that a patch is in transition and the task is
1916patched. If the patch is being enabled, then the task has already been
1917patched. If the patch is being disabled, then the task hasn't been
1918unpatched yet.
1919
1920
1921------------------------------------------------------------------------------
1922Configuring procfs
1923------------------------------------------------------------------------------
1924
19254.1 Mount options
1926---------------------
1927
1928The following mount options are supported:
1929
1930 hidepid= Set /proc/<pid>/ access mode.
1931 gid= Set the group authorized to learn processes information.
1932
1933hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1934(default).
1935
1936hidepid=1 means users may not access any /proc/<pid>/ directories but their
1937own. Sensitive files like cmdline, sched*, status are now protected against
1938other users. This makes it impossible to learn whether any user runs
1939specific program (given the program doesn't reveal itself by its behaviour).
1940As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1941poorly written programs passing sensitive information via program arguments are
1942now protected against local eavesdroppers.
1943
1944hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1945users. It doesn't mean that it hides a fact whether a process with a specific
1946pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1947but it hides process' uid and gid, which may be learned by stat()'ing
1948/proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering
1949information about running processes, whether some daemon runs with elevated
1950privileges, whether other user runs some sensitive program, whether other users
1951run any program at all, etc.
1952
1953gid= defines a group authorized to learn processes information otherwise
1954prohibited by hidepid=. If you use some daemon like identd which needs to learn
1955information about processes information, just add identd to this group.
1------------------------------------------------------------------------------
2 T H E /proc F I L E S Y S T E M
3------------------------------------------------------------------------------
4/proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999
5 Bodo Bauer <bb@ricochet.net>
6
72.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
8move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
9------------------------------------------------------------------------------
10Version 1.3 Kernel version 2.2.12
11 Kernel version 2.4.0-test11-pre4
12------------------------------------------------------------------------------
13fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009
14
15Table of Contents
16-----------------
17
18 0 Preface
19 0.1 Introduction/Credits
20 0.2 Legal Stuff
21
22 1 Collecting System Information
23 1.1 Process-Specific Subdirectories
24 1.2 Kernel data
25 1.3 IDE devices in /proc/ide
26 1.4 Networking info in /proc/net
27 1.5 SCSI info
28 1.6 Parallel port info in /proc/parport
29 1.7 TTY info in /proc/tty
30 1.8 Miscellaneous kernel statistics in /proc/stat
31 1.9 Ext4 file system parameters
32
33 2 Modifying System Parameters
34
35 3 Per-Process Parameters
36 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
37 score
38 3.2 /proc/<pid>/oom_score - Display current oom-killer score
39 3.3 /proc/<pid>/io - Display the IO accounting fields
40 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
41 3.5 /proc/<pid>/mountinfo - Information about mounts
42 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
43
44
45------------------------------------------------------------------------------
46Preface
47------------------------------------------------------------------------------
48
490.1 Introduction/Credits
50------------------------
51
52This documentation is part of a soon (or so we hope) to be released book on
53the SuSE Linux distribution. As there is no complete documentation for the
54/proc file system and we've used many freely available sources to write these
55chapters, it seems only fair to give the work back to the Linux community.
56This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
57afraid it's still far from complete, but we hope it will be useful. As far as
58we know, it is the first 'all-in-one' document about the /proc file system. It
59is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
60SPARC, AXP, etc., features, you probably won't find what you are looking for.
61It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
62additions and patches are welcome and will be added to this document if you
63mail them to Bodo.
64
65We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
66other people for help compiling this documentation. We'd also like to extend a
67special thank you to Andi Kleen for documentation, which we relied on heavily
68to create this document, as well as the additional information he provided.
69Thanks to everybody else who contributed source or docs to the Linux kernel
70and helped create a great piece of software... :)
71
72If you have any comments, corrections or additions, please don't hesitate to
73contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
74document.
75
76The latest version of this document is available online at
77http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
78
79If the above direction does not works for you, you could try the kernel
80mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
81comandante@zaralinux.com.
82
830.2 Legal Stuff
84---------------
85
86We don't guarantee the correctness of this document, and if you come to us
87complaining about how you screwed up your system because of incorrect
88documentation, we won't feel responsible...
89
90------------------------------------------------------------------------------
91CHAPTER 1: COLLECTING SYSTEM INFORMATION
92------------------------------------------------------------------------------
93
94------------------------------------------------------------------------------
95In This Chapter
96------------------------------------------------------------------------------
97* Investigating the properties of the pseudo file system /proc and its
98 ability to provide information on the running Linux system
99* Examining /proc's structure
100* Uncovering various information about the kernel and the processes running
101 on the system
102------------------------------------------------------------------------------
103
104
105The proc file system acts as an interface to internal data structures in the
106kernel. It can be used to obtain information about the system and to change
107certain kernel parameters at runtime (sysctl).
108
109First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
110show you how you can use /proc/sys to change settings.
111
1121.1 Process-Specific Subdirectories
113-----------------------------------
114
115The directory /proc contains (among other things) one subdirectory for each
116process running on the system, which is named after the process ID (PID).
117
118The link self points to the process reading the file system. Each process
119subdirectory has the entries listed in Table 1-1.
120
121
122Table 1-1: Process specific entries in /proc
123..............................................................................
124 File Content
125 clear_refs Clears page referenced bits shown in smaps output
126 cmdline Command line arguments
127 cpu Current and last cpu in which it was executed (2.4)(smp)
128 cwd Link to the current working directory
129 environ Values of environment variables
130 exe Link to the executable of this process
131 fd Directory, which contains all file descriptors
132 maps Memory maps to executables and library files (2.4)
133 mem Memory held by this process
134 root Link to the root directory of this process
135 stat Process status
136 statm Process memory status information
137 status Process status in human readable form
138 wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan
139 pagemap Page table
140 stack Report full stack trace, enable via CONFIG_STACKTRACE
141 smaps a extension based on maps, showing the memory consumption of
142 each mapping
143..............................................................................
144
145For example, to get the status information of a process, all you have to do is
146read the file /proc/PID/status:
147
148 >cat /proc/self/status
149 Name: cat
150 State: R (running)
151 Tgid: 5452
152 Pid: 5452
153 PPid: 743
154 TracerPid: 0 (2.4)
155 Uid: 501 501 501 501
156 Gid: 100 100 100 100
157 FDSize: 256
158 Groups: 100 14 16
159 VmPeak: 5004 kB
160 VmSize: 5004 kB
161 VmLck: 0 kB
162 VmHWM: 476 kB
163 VmRSS: 476 kB
164 VmData: 156 kB
165 VmStk: 88 kB
166 VmExe: 68 kB
167 VmLib: 1412 kB
168 VmPTE: 20 kb
169 VmSwap: 0 kB
170 Threads: 1
171 SigQ: 0/28578
172 SigPnd: 0000000000000000
173 ShdPnd: 0000000000000000
174 SigBlk: 0000000000000000
175 SigIgn: 0000000000000000
176 SigCgt: 0000000000000000
177 CapInh: 00000000fffffeff
178 CapPrm: 0000000000000000
179 CapEff: 0000000000000000
180 CapBnd: ffffffffffffffff
181 voluntary_ctxt_switches: 0
182 nonvoluntary_ctxt_switches: 1
183
184This shows you nearly the same information you would get if you viewed it with
185the ps command. In fact, ps uses the proc file system to obtain its
186information. But you get a more detailed view of the process by reading the
187file /proc/PID/status. It fields are described in table 1-2.
188
189The statm file contains more detailed information about the process
190memory usage. Its seven fields are explained in Table 1-3. The stat file
191contains details information about the process itself. Its fields are
192explained in Table 1-4.
193
194(for SMP CONFIG users)
195For making accounting scalable, RSS related information are handled in
196asynchronous manner and the vaule may not be very precise. To see a precise
197snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
198It's slow but very precise.
199
200Table 1-2: Contents of the status files (as of 2.6.30-rc7)
201..............................................................................
202 Field Content
203 Name filename of the executable
204 State state (R is running, S is sleeping, D is sleeping
205 in an uninterruptible wait, Z is zombie,
206 T is traced or stopped)
207 Tgid thread group ID
208 Pid process id
209 PPid process id of the parent process
210 TracerPid PID of process tracing this process (0 if not)
211 Uid Real, effective, saved set, and file system UIDs
212 Gid Real, effective, saved set, and file system GIDs
213 FDSize number of file descriptor slots currently allocated
214 Groups supplementary group list
215 VmPeak peak virtual memory size
216 VmSize total program size
217 VmLck locked memory size
218 VmHWM peak resident set size ("high water mark")
219 VmRSS size of memory portions
220 VmData size of data, stack, and text segments
221 VmStk size of data, stack, and text segments
222 VmExe size of text segment
223 VmLib size of shared library code
224 VmPTE size of page table entries
225 VmSwap size of swap usage (the number of referred swapents)
226 Threads number of threads
227 SigQ number of signals queued/max. number for queue
228 SigPnd bitmap of pending signals for the thread
229 ShdPnd bitmap of shared pending signals for the process
230 SigBlk bitmap of blocked signals
231 SigIgn bitmap of ignored signals
232 SigCgt bitmap of catched signals
233 CapInh bitmap of inheritable capabilities
234 CapPrm bitmap of permitted capabilities
235 CapEff bitmap of effective capabilities
236 CapBnd bitmap of capabilities bounding set
237 Cpus_allowed mask of CPUs on which this process may run
238 Cpus_allowed_list Same as previous, but in "list format"
239 Mems_allowed mask of memory nodes allowed to this process
240 Mems_allowed_list Same as previous, but in "list format"
241 voluntary_ctxt_switches number of voluntary context switches
242 nonvoluntary_ctxt_switches number of non voluntary context switches
243..............................................................................
244
245Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
246..............................................................................
247 Field Content
248 size total program size (pages) (same as VmSize in status)
249 resident size of memory portions (pages) (same as VmRSS in status)
250 shared number of pages that are shared (i.e. backed by a file)
251 trs number of pages that are 'code' (not including libs; broken,
252 includes data segment)
253 lrs number of pages of library (always 0 on 2.6)
254 drs number of pages of data/stack (including libs; broken,
255 includes library text)
256 dt number of dirty pages (always 0 on 2.6)
257..............................................................................
258
259
260Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
261..............................................................................
262 Field Content
263 pid process id
264 tcomm filename of the executable
265 state state (R is running, S is sleeping, D is sleeping in an
266 uninterruptible wait, Z is zombie, T is traced or stopped)
267 ppid process id of the parent process
268 pgrp pgrp of the process
269 sid session id
270 tty_nr tty the process uses
271 tty_pgrp pgrp of the tty
272 flags task flags
273 min_flt number of minor faults
274 cmin_flt number of minor faults with child's
275 maj_flt number of major faults
276 cmaj_flt number of major faults with child's
277 utime user mode jiffies
278 stime kernel mode jiffies
279 cutime user mode jiffies with child's
280 cstime kernel mode jiffies with child's
281 priority priority level
282 nice nice level
283 num_threads number of threads
284 it_real_value (obsolete, always 0)
285 start_time time the process started after system boot
286 vsize virtual memory size
287 rss resident set memory size
288 rsslim current limit in bytes on the rss
289 start_code address above which program text can run
290 end_code address below which program text can run
291 start_stack address of the start of the stack
292 esp current value of ESP
293 eip current value of EIP
294 pending bitmap of pending signals
295 blocked bitmap of blocked signals
296 sigign bitmap of ignored signals
297 sigcatch bitmap of catched signals
298 wchan address where process went to sleep
299 0 (place holder)
300 0 (place holder)
301 exit_signal signal to send to parent thread on exit
302 task_cpu which CPU the task is scheduled on
303 rt_priority realtime priority
304 policy scheduling policy (man sched_setscheduler)
305 blkio_ticks time spent waiting for block IO
306 gtime guest time of the task in jiffies
307 cgtime guest time of the task children in jiffies
308..............................................................................
309
310The /proc/PID/maps file containing the currently mapped memory regions and
311their access permissions.
312
313The format is:
314
315address perms offset dev inode pathname
316
31708048000-08049000 r-xp 00000000 03:00 8312 /opt/test
31808049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
3190804a000-0806b000 rw-p 00000000 00:00 0 [heap]
320a7cb1000-a7cb2000 ---p 00000000 00:00 0
321a7cb2000-a7eb2000 rw-p 00000000 00:00 0
322a7eb2000-a7eb3000 ---p 00000000 00:00 0
323a7eb3000-a7ed5000 rw-p 00000000 00:00 0
324a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
325a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
326a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
327a800b000-a800e000 rw-p 00000000 00:00 0
328a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
329a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
330a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
331a8024000-a8027000 rw-p 00000000 00:00 0
332a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
333a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
334a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
335aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
336ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
337
338where "address" is the address space in the process that it occupies, "perms"
339is a set of permissions:
340
341 r = read
342 w = write
343 x = execute
344 s = shared
345 p = private (copy on write)
346
347"offset" is the offset into the mapping, "dev" is the device (major:minor), and
348"inode" is the inode on that device. 0 indicates that no inode is associated
349with the memory region, as the case would be with BSS (uninitialized data).
350The "pathname" shows the name associated file for this mapping. If the mapping
351is not associated with a file:
352
353 [heap] = the heap of the program
354 [stack] = the stack of the main process
355 [vdso] = the "virtual dynamic shared object",
356 the kernel system call handler
357
358 or if empty, the mapping is anonymous.
359
360
361The /proc/PID/smaps is an extension based on maps, showing the memory
362consumption for each of the process's mappings. For each of mappings there
363is a series of lines such as the following:
364
36508048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
366Size: 1084 kB
367Rss: 892 kB
368Pss: 374 kB
369Shared_Clean: 892 kB
370Shared_Dirty: 0 kB
371Private_Clean: 0 kB
372Private_Dirty: 0 kB
373Referenced: 892 kB
374Anonymous: 0 kB
375Swap: 0 kB
376KernelPageSize: 4 kB
377MMUPageSize: 4 kB
378Locked: 374 kB
379
380The first of these lines shows the same information as is displayed for the
381mapping in /proc/PID/maps. The remaining lines show the size of the mapping
382(size), the amount of the mapping that is currently resident in RAM (RSS), the
383process' proportional share of this mapping (PSS), the number of clean and
384dirty private pages in the mapping. Note that even a page which is part of a
385MAP_SHARED mapping, but has only a single pte mapped, i.e. is currently used
386by only one process, is accounted as private and not as shared. "Referenced"
387indicates the amount of memory currently marked as referenced or accessed.
388"Anonymous" shows the amount of memory that does not belong to any file. Even
389a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
390and a page is modified, the file page is replaced by a private anonymous copy.
391"Swap" shows how much would-be-anonymous memory is also used, but out on
392swap.
393
394This file is only present if the CONFIG_MMU kernel configuration option is
395enabled.
396
397The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
398bits on both physical and virtual pages associated with a process.
399To clear the bits for all the pages associated with the process
400 > echo 1 > /proc/PID/clear_refs
401
402To clear the bits for the anonymous pages associated with the process
403 > echo 2 > /proc/PID/clear_refs
404
405To clear the bits for the file mapped pages associated with the process
406 > echo 3 > /proc/PID/clear_refs
407Any other value written to /proc/PID/clear_refs will have no effect.
408
409The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
410using /proc/kpageflags and number of times a page is mapped using
411/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
412
4131.2 Kernel data
414---------------
415
416Similar to the process entries, the kernel data files give information about
417the running kernel. The files used to obtain this information are contained in
418/proc and are listed in Table 1-5. Not all of these will be present in your
419system. It depends on the kernel configuration and the loaded modules, which
420files are there, and which are missing.
421
422Table 1-5: Kernel info in /proc
423..............................................................................
424 File Content
425 apm Advanced power management info
426 buddyinfo Kernel memory allocator information (see text) (2.5)
427 bus Directory containing bus specific information
428 cmdline Kernel command line
429 cpuinfo Info about the CPU
430 devices Available devices (block and character)
431 dma Used DMS channels
432 filesystems Supported filesystems
433 driver Various drivers grouped here, currently rtc (2.4)
434 execdomains Execdomains, related to security (2.4)
435 fb Frame Buffer devices (2.4)
436 fs File system parameters, currently nfs/exports (2.4)
437 ide Directory containing info about the IDE subsystem
438 interrupts Interrupt usage
439 iomem Memory map (2.4)
440 ioports I/O port usage
441 irq Masks for irq to cpu affinity (2.4)(smp?)
442 isapnp ISA PnP (Plug&Play) Info (2.4)
443 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
444 kmsg Kernel messages
445 ksyms Kernel symbol table
446 loadavg Load average of last 1, 5 & 15 minutes
447 locks Kernel locks
448 meminfo Memory info
449 misc Miscellaneous
450 modules List of loaded modules
451 mounts Mounted filesystems
452 net Networking info (see text)
453 pagetypeinfo Additional page allocator information (see text) (2.5)
454 partitions Table of partitions known to the system
455 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
456 decoupled by lspci (2.4)
457 rtc Real time clock
458 scsi SCSI info (see text)
459 slabinfo Slab pool info
460 softirqs softirq usage
461 stat Overall statistics
462 swaps Swap space utilization
463 sys See chapter 2
464 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
465 tty Info of tty drivers
466 uptime System uptime
467 version Kernel version
468 video bttv info of video resources (2.4)
469 vmallocinfo Show vmalloced areas
470..............................................................................
471
472You can, for example, check which interrupts are currently in use and what
473they are used for by looking in the file /proc/interrupts:
474
475 > cat /proc/interrupts
476 CPU0
477 0: 8728810 XT-PIC timer
478 1: 895 XT-PIC keyboard
479 2: 0 XT-PIC cascade
480 3: 531695 XT-PIC aha152x
481 4: 2014133 XT-PIC serial
482 5: 44401 XT-PIC pcnet_cs
483 8: 2 XT-PIC rtc
484 11: 8 XT-PIC i82365
485 12: 182918 XT-PIC PS/2 Mouse
486 13: 1 XT-PIC fpu
487 14: 1232265 XT-PIC ide0
488 15: 7 XT-PIC ide1
489 NMI: 0
490
491In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
492output of a SMP machine):
493
494 > cat /proc/interrupts
495
496 CPU0 CPU1
497 0: 1243498 1214548 IO-APIC-edge timer
498 1: 8949 8958 IO-APIC-edge keyboard
499 2: 0 0 XT-PIC cascade
500 5: 11286 10161 IO-APIC-edge soundblaster
501 8: 1 0 IO-APIC-edge rtc
502 9: 27422 27407 IO-APIC-edge 3c503
503 12: 113645 113873 IO-APIC-edge PS/2 Mouse
504 13: 0 0 XT-PIC fpu
505 14: 22491 24012 IO-APIC-edge ide0
506 15: 2183 2415 IO-APIC-edge ide1
507 17: 30564 30414 IO-APIC-level eth0
508 18: 177 164 IO-APIC-level bttv
509 NMI: 2457961 2457959
510 LOC: 2457882 2457881
511 ERR: 2155
512
513NMI is incremented in this case because every timer interrupt generates a NMI
514(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
515
516LOC is the local interrupt counter of the internal APIC of every CPU.
517
518ERR is incremented in the case of errors in the IO-APIC bus (the bus that
519connects the CPUs in a SMP system. This means that an error has been detected,
520the IO-APIC automatically retry the transmission, so it should not be a big
521problem, but you should read the SMP-FAQ.
522
523In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
524/proc/interrupts to display every IRQ vector in use by the system, not
525just those considered 'most important'. The new vectors are:
526
527 THR -- interrupt raised when a machine check threshold counter
528 (typically counting ECC corrected errors of memory or cache) exceeds
529 a configurable threshold. Only available on some systems.
530
531 TRM -- a thermal event interrupt occurs when a temperature threshold
532 has been exceeded for the CPU. This interrupt may also be generated
533 when the temperature drops back to normal.
534
535 SPU -- a spurious interrupt is some interrupt that was raised then lowered
536 by some IO device before it could be fully processed by the APIC. Hence
537 the APIC sees the interrupt but does not know what device it came from.
538 For this case the APIC will generate the interrupt with a IRQ vector
539 of 0xff. This might also be generated by chipset bugs.
540
541 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
542 sent from one CPU to another per the needs of the OS. Typically,
543 their statistics are used by kernel developers and interested users to
544 determine the occurrence of interrupts of the given type.
545
546The above IRQ vectors are displayed only when relevant. For example,
547the threshold vector does not exist on x86_64 platforms. Others are
548suppressed when the system is a uniprocessor. As of this writing, only
549i386 and x86_64 platforms support the new IRQ vector displays.
550
551Of some interest is the introduction of the /proc/irq directory to 2.4.
552It could be used to set IRQ to CPU affinity, this means that you can "hook" an
553IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
554irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
555prof_cpu_mask.
556
557For example
558 > ls /proc/irq/
559 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
560 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
561 > ls /proc/irq/0/
562 smp_affinity
563
564smp_affinity is a bitmask, in which you can specify which CPUs can handle the
565IRQ, you can set it by doing:
566
567 > echo 1 > /proc/irq/10/smp_affinity
568
569This means that only the first CPU will handle the IRQ, but you can also echo
5705 which means that only the first and fourth CPU can handle the IRQ.
571
572The contents of each smp_affinity file is the same by default:
573
574 > cat /proc/irq/0/smp_affinity
575 ffffffff
576
577There is an alternate interface, smp_affinity_list which allows specifying
578a cpu range instead of a bitmask:
579
580 > cat /proc/irq/0/smp_affinity_list
581 1024-1031
582
583The default_smp_affinity mask applies to all non-active IRQs, which are the
584IRQs which have not yet been allocated/activated, and hence which lack a
585/proc/irq/[0-9]* directory.
586
587The node file on an SMP system shows the node to which the device using the IRQ
588reports itself as being attached. This hardware locality information does not
589include information about any possible driver locality preference.
590
591prof_cpu_mask specifies which CPUs are to be profiled by the system wide
592profiler. Default value is ffffffff (all cpus if there are only 32 of them).
593
594The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
595between all the CPUs which are allowed to handle it. As usual the kernel has
596more info than you and does a better job than you, so the defaults are the
597best choice for almost everyone. [Note this applies only to those IO-APIC's
598that support "Round Robin" interrupt distribution.]
599
600There are three more important subdirectories in /proc: net, scsi, and sys.
601The general rule is that the contents, or even the existence of these
602directories, depend on your kernel configuration. If SCSI is not enabled, the
603directory scsi may not exist. The same is true with the net, which is there
604only when networking support is present in the running kernel.
605
606The slabinfo file gives information about memory usage at the slab level.
607Linux uses slab pools for memory management above page level in version 2.2.
608Commonly used objects have their own slab pool (such as network buffers,
609directory cache, and so on).
610
611..............................................................................
612
613> cat /proc/buddyinfo
614
615Node 0, zone DMA 0 4 5 4 4 3 ...
616Node 0, zone Normal 1 0 0 1 101 8 ...
617Node 0, zone HighMem 2 0 0 1 1 0 ...
618
619External fragmentation is a problem under some workloads, and buddyinfo is a
620useful tool for helping diagnose these problems. Buddyinfo will give you a
621clue as to how big an area you can safely allocate, or why a previous
622allocation failed.
623
624Each column represents the number of pages of a certain order which are
625available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
626ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
627available in ZONE_NORMAL, etc...
628
629More information relevant to external fragmentation can be found in
630pagetypeinfo.
631
632> cat /proc/pagetypeinfo
633Page block order: 9
634Pages per block: 512
635
636Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
637Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
638Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
639Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
640Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
641Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
642Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
643Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
644Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
645Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
646Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
647
648Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
649Node 0, zone DMA 2 0 5 1 0
650Node 0, zone DMA32 41 6 967 2 0
651
652Fragmentation avoidance in the kernel works by grouping pages of different
653migrate types into the same contiguous regions of memory called page blocks.
654A page block is typically the size of the default hugepage size e.g. 2MB on
655X86-64. By keeping pages grouped based on their ability to move, the kernel
656can reclaim pages within a page block to satisfy a high-order allocation.
657
658The pagetypinfo begins with information on the size of a page block. It
659then gives the same type of information as buddyinfo except broken down
660by migrate-type and finishes with details on how many page blocks of each
661type exist.
662
663If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
664from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
665make an estimate of the likely number of huge pages that can be allocated
666at a given point in time. All the "Movable" blocks should be allocatable
667unless memory has been mlock()'d. Some of the Reclaimable blocks should
668also be allocatable although a lot of filesystem metadata may have to be
669reclaimed to achieve this.
670
671..............................................................................
672
673meminfo:
674
675Provides information about distribution and utilization of memory. This
676varies by architecture and compile options. The following is from a
67716GB PIII, which has highmem enabled. You may not have all of these fields.
678
679> cat /proc/meminfo
680
681The "Locked" indicates whether the mapping is locked in memory or not.
682
683
684MemTotal: 16344972 kB
685MemFree: 13634064 kB
686Buffers: 3656 kB
687Cached: 1195708 kB
688SwapCached: 0 kB
689Active: 891636 kB
690Inactive: 1077224 kB
691HighTotal: 15597528 kB
692HighFree: 13629632 kB
693LowTotal: 747444 kB
694LowFree: 4432 kB
695SwapTotal: 0 kB
696SwapFree: 0 kB
697Dirty: 968 kB
698Writeback: 0 kB
699AnonPages: 861800 kB
700Mapped: 280372 kB
701Slab: 284364 kB
702SReclaimable: 159856 kB
703SUnreclaim: 124508 kB
704PageTables: 24448 kB
705NFS_Unstable: 0 kB
706Bounce: 0 kB
707WritebackTmp: 0 kB
708CommitLimit: 7669796 kB
709Committed_AS: 100056 kB
710VmallocTotal: 112216 kB
711VmallocUsed: 428 kB
712VmallocChunk: 111088 kB
713
714 MemTotal: Total usable ram (i.e. physical ram minus a few reserved
715 bits and the kernel binary code)
716 MemFree: The sum of LowFree+HighFree
717 Buffers: Relatively temporary storage for raw disk blocks
718 shouldn't get tremendously large (20MB or so)
719 Cached: in-memory cache for files read from the disk (the
720 pagecache). Doesn't include SwapCached
721 SwapCached: Memory that once was swapped out, is swapped back in but
722 still also is in the swapfile (if memory is needed it
723 doesn't need to be swapped out AGAIN because it is already
724 in the swapfile. This saves I/O)
725 Active: Memory that has been used more recently and usually not
726 reclaimed unless absolutely necessary.
727 Inactive: Memory which has been less recently used. It is more
728 eligible to be reclaimed for other purposes
729 HighTotal:
730 HighFree: Highmem is all memory above ~860MB of physical memory
731 Highmem areas are for use by userspace programs, or
732 for the pagecache. The kernel must use tricks to access
733 this memory, making it slower to access than lowmem.
734 LowTotal:
735 LowFree: Lowmem is memory which can be used for everything that
736 highmem can be used for, but it is also available for the
737 kernel's use for its own data structures. Among many
738 other things, it is where everything from the Slab is
739 allocated. Bad things happen when you're out of lowmem.
740 SwapTotal: total amount of swap space available
741 SwapFree: Memory which has been evicted from RAM, and is temporarily
742 on the disk
743 Dirty: Memory which is waiting to get written back to the disk
744 Writeback: Memory which is actively being written back to the disk
745 AnonPages: Non-file backed pages mapped into userspace page tables
746 Mapped: files which have been mmaped, such as libraries
747 Slab: in-kernel data structures cache
748SReclaimable: Part of Slab, that might be reclaimed, such as caches
749 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
750 PageTables: amount of memory dedicated to the lowest level of page
751 tables.
752NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
753 storage
754 Bounce: Memory used for block device "bounce buffers"
755WritebackTmp: Memory used by FUSE for temporary writeback buffers
756 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
757 this is the total amount of memory currently available to
758 be allocated on the system. This limit is only adhered to
759 if strict overcommit accounting is enabled (mode 2 in
760 'vm.overcommit_memory').
761 The CommitLimit is calculated with the following formula:
762 CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap
763 For example, on a system with 1G of physical RAM and 7G
764 of swap with a `vm.overcommit_ratio` of 30 it would
765 yield a CommitLimit of 7.3G.
766 For more details, see the memory overcommit documentation
767 in vm/overcommit-accounting.
768Committed_AS: The amount of memory presently allocated on the system.
769 The committed memory is a sum of all of the memory which
770 has been allocated by processes, even if it has not been
771 "used" by them as of yet. A process which malloc()'s 1G
772 of memory, but only touches 300M of it will only show up
773 as using 300M of memory even if it has the address space
774 allocated for the entire 1G. This 1G is memory which has
775 been "committed" to by the VM and can be used at any time
776 by the allocating application. With strict overcommit
777 enabled on the system (mode 2 in 'vm.overcommit_memory'),
778 allocations which would exceed the CommitLimit (detailed
779 above) will not be permitted. This is useful if one needs
780 to guarantee that processes will not fail due to lack of
781 memory once that memory has been successfully allocated.
782VmallocTotal: total size of vmalloc memory area
783 VmallocUsed: amount of vmalloc area which is used
784VmallocChunk: largest contiguous block of vmalloc area which is free
785
786..............................................................................
787
788vmallocinfo:
789
790Provides information about vmalloced/vmaped areas. One line per area,
791containing the virtual address range of the area, size in bytes,
792caller information of the creator, and optional information depending
793on the kind of area :
794
795 pages=nr number of pages
796 phys=addr if a physical address was specified
797 ioremap I/O mapping (ioremap() and friends)
798 vmalloc vmalloc() area
799 vmap vmap()ed pages
800 user VM_USERMAP area
801 vpages buffer for pages pointers was vmalloced (huge area)
802 N<node>=nr (Only on NUMA kernels)
803 Number of pages allocated on memory node <node>
804
805> cat /proc/vmallocinfo
8060xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
807 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
8080xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
809 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
8100xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
811 phys=7fee8000 ioremap
8120xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
813 phys=7fee7000 ioremap
8140xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
8150xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
816 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
8170xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
818 pages=2 vmalloc N1=2
8190xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
820 /0x130 [x_tables] pages=4 vmalloc N0=4
8210xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
822 pages=14 vmalloc N2=14
8230xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
824 pages=4 vmalloc N1=4
8250xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
826 pages=2 vmalloc N1=2
8270xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
828 pages=10 vmalloc N0=10
829
830..............................................................................
831
832softirqs:
833
834Provides counts of softirq handlers serviced since boot time, for each cpu.
835
836> cat /proc/softirqs
837 CPU0 CPU1 CPU2 CPU3
838 HI: 0 0 0 0
839 TIMER: 27166 27120 27097 27034
840 NET_TX: 0 0 0 17
841 NET_RX: 42 0 0 39
842 BLOCK: 0 0 107 1121
843 TASKLET: 0 0 0 290
844 SCHED: 27035 26983 26971 26746
845 HRTIMER: 0 0 0 0
846 RCU: 1678 1769 2178 2250
847
848
8491.3 IDE devices in /proc/ide
850----------------------------
851
852The subdirectory /proc/ide contains information about all IDE devices of which
853the kernel is aware. There is one subdirectory for each IDE controller, the
854file drivers and a link for each IDE device, pointing to the device directory
855in the controller specific subtree.
856
857The file drivers contains general information about the drivers used for the
858IDE devices:
859
860 > cat /proc/ide/drivers
861 ide-cdrom version 4.53
862 ide-disk version 1.08
863
864More detailed information can be found in the controller specific
865subdirectories. These are named ide0, ide1 and so on. Each of these
866directories contains the files shown in table 1-6.
867
868
869Table 1-6: IDE controller info in /proc/ide/ide?
870..............................................................................
871 File Content
872 channel IDE channel (0 or 1)
873 config Configuration (only for PCI/IDE bridge)
874 mate Mate name
875 model Type/Chipset of IDE controller
876..............................................................................
877
878Each device connected to a controller has a separate subdirectory in the
879controllers directory. The files listed in table 1-7 are contained in these
880directories.
881
882
883Table 1-7: IDE device information
884..............................................................................
885 File Content
886 cache The cache
887 capacity Capacity of the medium (in 512Byte blocks)
888 driver driver and version
889 geometry physical and logical geometry
890 identify device identify block
891 media media type
892 model device identifier
893 settings device setup
894 smart_thresholds IDE disk management thresholds
895 smart_values IDE disk management values
896..............................................................................
897
898The most interesting file is settings. This file contains a nice overview of
899the drive parameters:
900
901 # cat /proc/ide/ide0/hda/settings
902 name value min max mode
903 ---- ----- --- --- ----
904 bios_cyl 526 0 65535 rw
905 bios_head 255 0 255 rw
906 bios_sect 63 0 63 rw
907 breada_readahead 4 0 127 rw
908 bswap 0 0 1 r
909 file_readahead 72 0 2097151 rw
910 io_32bit 0 0 3 rw
911 keepsettings 0 0 1 rw
912 max_kb_per_request 122 1 127 rw
913 multcount 0 0 8 rw
914 nice1 1 0 1 rw
915 nowerr 0 0 1 rw
916 pio_mode write-only 0 255 w
917 slow 0 0 1 rw
918 unmaskirq 0 0 1 rw
919 using_dma 0 0 1 rw
920
921
9221.4 Networking info in /proc/net
923--------------------------------
924
925The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
926additional values you get for IP version 6 if you configure the kernel to
927support this. Table 1-9 lists the files and their meaning.
928
929
930Table 1-8: IPv6 info in /proc/net
931..............................................................................
932 File Content
933 udp6 UDP sockets (IPv6)
934 tcp6 TCP sockets (IPv6)
935 raw6 Raw device statistics (IPv6)
936 igmp6 IP multicast addresses, which this host joined (IPv6)
937 if_inet6 List of IPv6 interface addresses
938 ipv6_route Kernel routing table for IPv6
939 rt6_stats Global IPv6 routing tables statistics
940 sockstat6 Socket statistics (IPv6)
941 snmp6 Snmp data (IPv6)
942..............................................................................
943
944
945Table 1-9: Network info in /proc/net
946..............................................................................
947 File Content
948 arp Kernel ARP table
949 dev network devices with statistics
950 dev_mcast the Layer2 multicast groups a device is listening too
951 (interface index, label, number of references, number of bound
952 addresses).
953 dev_stat network device status
954 ip_fwchains Firewall chain linkage
955 ip_fwnames Firewall chain names
956 ip_masq Directory containing the masquerading tables
957 ip_masquerade Major masquerading table
958 netstat Network statistics
959 raw raw device statistics
960 route Kernel routing table
961 rpc Directory containing rpc info
962 rt_cache Routing cache
963 snmp SNMP data
964 sockstat Socket statistics
965 tcp TCP sockets
966 tr_rif Token ring RIF routing table
967 udp UDP sockets
968 unix UNIX domain sockets
969 wireless Wireless interface data (Wavelan etc)
970 igmp IP multicast addresses, which this host joined
971 psched Global packet scheduler parameters.
972 netlink List of PF_NETLINK sockets
973 ip_mr_vifs List of multicast virtual interfaces
974 ip_mr_cache List of multicast routing cache
975..............................................................................
976
977You can use this information to see which network devices are available in
978your system and how much traffic was routed over those devices:
979
980 > cat /proc/net/dev
981 Inter-|Receive |[...
982 face |bytes packets errs drop fifo frame compressed multicast|[...
983 lo: 908188 5596 0 0 0 0 0 0 [...
984 ppp0:15475140 20721 410 0 0 410 0 0 [...
985 eth0: 614530 7085 0 0 0 0 0 1 [...
986
987 ...] Transmit
988 ...] bytes packets errs drop fifo colls carrier compressed
989 ...] 908188 5596 0 0 0 0 0 0
990 ...] 1375103 17405 0 0 0 0 0 0
991 ...] 1703981 5535 0 0 0 3 0 0
992
993In addition, each Channel Bond interface has its own directory. For
994example, the bond0 device will have a directory called /proc/net/bond0/.
995It will contain information that is specific to that bond, such as the
996current slaves of the bond, the link status of the slaves, and how
997many times the slaves link has failed.
998
9991.5 SCSI info
1000-------------
1001
1002If you have a SCSI host adapter in your system, you'll find a subdirectory
1003named after the driver for this adapter in /proc/scsi. You'll also see a list
1004of all recognized SCSI devices in /proc/scsi:
1005
1006 >cat /proc/scsi/scsi
1007 Attached devices:
1008 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1009 Vendor: IBM Model: DGHS09U Rev: 03E0
1010 Type: Direct-Access ANSI SCSI revision: 03
1011 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1012 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1013 Type: CD-ROM ANSI SCSI revision: 02
1014
1015
1016The directory named after the driver has one file for each adapter found in
1017the system. These files contain information about the controller, including
1018the used IRQ and the IO address range. The amount of information shown is
1019dependent on the adapter you use. The example shows the output for an Adaptec
1020AHA-2940 SCSI adapter:
1021
1022 > cat /proc/scsi/aic7xxx/0
1023
1024 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1025 Compile Options:
1026 TCQ Enabled By Default : Disabled
1027 AIC7XXX_PROC_STATS : Disabled
1028 AIC7XXX_RESET_DELAY : 5
1029 Adapter Configuration:
1030 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1031 Ultra Wide Controller
1032 PCI MMAPed I/O Base: 0xeb001000
1033 Adapter SEEPROM Config: SEEPROM found and used.
1034 Adaptec SCSI BIOS: Enabled
1035 IRQ: 10
1036 SCBs: Active 0, Max Active 2,
1037 Allocated 15, HW 16, Page 255
1038 Interrupts: 160328
1039 BIOS Control Word: 0x18b6
1040 Adapter Control Word: 0x005b
1041 Extended Translation: Enabled
1042 Disconnect Enable Flags: 0xffff
1043 Ultra Enable Flags: 0x0001
1044 Tag Queue Enable Flags: 0x0000
1045 Ordered Queue Tag Flags: 0x0000
1046 Default Tag Queue Depth: 8
1047 Tagged Queue By Device array for aic7xxx host instance 0:
1048 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1049 Actual queue depth per device for aic7xxx host instance 0:
1050 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1051 Statistics:
1052 (scsi0:0:0:0)
1053 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1054 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1055 Total transfers 160151 (74577 reads and 85574 writes)
1056 (scsi0:0:6:0)
1057 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1058 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1059 Total transfers 0 (0 reads and 0 writes)
1060
1061
10621.6 Parallel port info in /proc/parport
1063---------------------------------------
1064
1065The directory /proc/parport contains information about the parallel ports of
1066your system. It has one subdirectory for each port, named after the port
1067number (0,1,2,...).
1068
1069These directories contain the four files shown in Table 1-10.
1070
1071
1072Table 1-10: Files in /proc/parport
1073..............................................................................
1074 File Content
1075 autoprobe Any IEEE-1284 device ID information that has been acquired.
1076 devices list of the device drivers using that port. A + will appear by the
1077 name of the device currently using the port (it might not appear
1078 against any).
1079 hardware Parallel port's base address, IRQ line and DMA channel.
1080 irq IRQ that parport is using for that port. This is in a separate
1081 file to allow you to alter it by writing a new value in (IRQ
1082 number or none).
1083..............................................................................
1084
10851.7 TTY info in /proc/tty
1086-------------------------
1087
1088Information about the available and actually used tty's can be found in the
1089directory /proc/tty.You'll find entries for drivers and line disciplines in
1090this directory, as shown in Table 1-11.
1091
1092
1093Table 1-11: Files in /proc/tty
1094..............................................................................
1095 File Content
1096 drivers list of drivers and their usage
1097 ldiscs registered line disciplines
1098 driver/serial usage statistic and status of single tty lines
1099..............................................................................
1100
1101To see which tty's are currently in use, you can simply look into the file
1102/proc/tty/drivers:
1103
1104 > cat /proc/tty/drivers
1105 pty_slave /dev/pts 136 0-255 pty:slave
1106 pty_master /dev/ptm 128 0-255 pty:master
1107 pty_slave /dev/ttyp 3 0-255 pty:slave
1108 pty_master /dev/pty 2 0-255 pty:master
1109 serial /dev/cua 5 64-67 serial:callout
1110 serial /dev/ttyS 4 64-67 serial
1111 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1112 /dev/ptmx /dev/ptmx 5 2 system
1113 /dev/console /dev/console 5 1 system:console
1114 /dev/tty /dev/tty 5 0 system:/dev/tty
1115 unknown /dev/tty 4 1-63 console
1116
1117
11181.8 Miscellaneous kernel statistics in /proc/stat
1119-------------------------------------------------
1120
1121Various pieces of information about kernel activity are available in the
1122/proc/stat file. All of the numbers reported in this file are aggregates
1123since the system first booted. For a quick look, simply cat the file:
1124
1125 > cat /proc/stat
1126 cpu 2255 34 2290 22625563 6290 127 456 0 0
1127 cpu0 1132 34 1441 11311718 3675 127 438 0 0
1128 cpu1 1123 0 849 11313845 2614 0 18 0 0
1129 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1130 ctxt 1990473
1131 btime 1062191376
1132 processes 2915
1133 procs_running 1
1134 procs_blocked 0
1135 softirq 183433 0 21755 12 39 1137 231 21459 2263
1136
1137The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1138lines. These numbers identify the amount of time the CPU has spent performing
1139different kinds of work. Time units are in USER_HZ (typically hundredths of a
1140second). The meanings of the columns are as follows, from left to right:
1141
1142- user: normal processes executing in user mode
1143- nice: niced processes executing in user mode
1144- system: processes executing in kernel mode
1145- idle: twiddling thumbs
1146- iowait: waiting for I/O to complete
1147- irq: servicing interrupts
1148- softirq: servicing softirqs
1149- steal: involuntary wait
1150- guest: running a normal guest
1151- guest_nice: running a niced guest
1152
1153The "intr" line gives counts of interrupts serviced since boot time, for each
1154of the possible system interrupts. The first column is the total of all
1155interrupts serviced; each subsequent column is the total for that particular
1156interrupt.
1157
1158The "ctxt" line gives the total number of context switches across all CPUs.
1159
1160The "btime" line gives the time at which the system booted, in seconds since
1161the Unix epoch.
1162
1163The "processes" line gives the number of processes and threads created, which
1164includes (but is not limited to) those created by calls to the fork() and
1165clone() system calls.
1166
1167The "procs_running" line gives the total number of threads that are
1168running or ready to run (i.e., the total number of runnable threads).
1169
1170The "procs_blocked" line gives the number of processes currently blocked,
1171waiting for I/O to complete.
1172
1173The "softirq" line gives counts of softirqs serviced since boot time, for each
1174of the possible system softirqs. The first column is the total of all
1175softirqs serviced; each subsequent column is the total for that particular
1176softirq.
1177
1178
11791.9 Ext4 file system parameters
1180------------------------------
1181
1182Information about mounted ext4 file systems can be found in
1183/proc/fs/ext4. Each mounted filesystem will have a directory in
1184/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1185/proc/fs/ext4/dm-0). The files in each per-device directory are shown
1186in Table 1-12, below.
1187
1188Table 1-12: Files in /proc/fs/ext4/<devname>
1189..............................................................................
1190 File Content
1191 mb_groups details of multiblock allocator buddy cache of free blocks
1192..............................................................................
1193
11942.0 /proc/consoles
1195------------------
1196Shows registered system console lines.
1197
1198To see which character device lines are currently used for the system console
1199/dev/console, you may simply look into the file /proc/consoles:
1200
1201 > cat /proc/consoles
1202 tty0 -WU (ECp) 4:7
1203 ttyS0 -W- (Ep) 4:64
1204
1205The columns are:
1206
1207 device name of the device
1208 operations R = can do read operations
1209 W = can do write operations
1210 U = can do unblank
1211 flags E = it is enabled
1212 C = it is preferred console
1213 B = it is primary boot console
1214 p = it is used for printk buffer
1215 b = it is not a TTY but a Braille device
1216 a = it is safe to use when cpu is offline
1217 major:minor major and minor number of the device separated by a colon
1218
1219------------------------------------------------------------------------------
1220Summary
1221------------------------------------------------------------------------------
1222The /proc file system serves information about the running system. It not only
1223allows access to process data but also allows you to request the kernel status
1224by reading files in the hierarchy.
1225
1226The directory structure of /proc reflects the types of information and makes
1227it easy, if not obvious, where to look for specific data.
1228------------------------------------------------------------------------------
1229
1230------------------------------------------------------------------------------
1231CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1232------------------------------------------------------------------------------
1233
1234------------------------------------------------------------------------------
1235In This Chapter
1236------------------------------------------------------------------------------
1237* Modifying kernel parameters by writing into files found in /proc/sys
1238* Exploring the files which modify certain parameters
1239* Review of the /proc/sys file tree
1240------------------------------------------------------------------------------
1241
1242
1243A very interesting part of /proc is the directory /proc/sys. This is not only
1244a source of information, it also allows you to change parameters within the
1245kernel. Be very careful when attempting this. You can optimize your system,
1246but you can also cause it to crash. Never alter kernel parameters on a
1247production system. Set up a development machine and test to make sure that
1248everything works the way you want it to. You may have no alternative but to
1249reboot the machine once an error has been made.
1250
1251To change a value, simply echo the new value into the file. An example is
1252given below in the section on the file system data. You need to be root to do
1253this. You can create your own boot script to perform this every time your
1254system boots.
1255
1256The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1257general things in the operation of the Linux kernel. Since some of the files
1258can inadvertently disrupt your system, it is advisable to read both
1259documentation and source before actually making adjustments. In any case, be
1260very careful when writing to any of these files. The entries in /proc may
1261change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1262review the kernel documentation in the directory /usr/src/linux/Documentation.
1263This chapter is heavily based on the documentation included in the pre 2.2
1264kernels, and became part of it in version 2.2.1 of the Linux kernel.
1265
1266Please see: Documentation/sysctls/ directory for descriptions of these
1267entries.
1268
1269------------------------------------------------------------------------------
1270Summary
1271------------------------------------------------------------------------------
1272Certain aspects of kernel behavior can be modified at runtime, without the
1273need to recompile the kernel, or even to reboot the system. The files in the
1274/proc/sys tree can not only be read, but also modified. You can use the echo
1275command to write value into these files, thereby changing the default settings
1276of the kernel.
1277------------------------------------------------------------------------------
1278
1279------------------------------------------------------------------------------
1280CHAPTER 3: PER-PROCESS PARAMETERS
1281------------------------------------------------------------------------------
1282
12833.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1284--------------------------------------------------------------------------------
1285
1286These file can be used to adjust the badness heuristic used to select which
1287process gets killed in out of memory conditions.
1288
1289The badness heuristic assigns a value to each candidate task ranging from 0
1290(never kill) to 1000 (always kill) to determine which process is targeted. The
1291units are roughly a proportion along that range of allowed memory the process
1292may allocate from based on an estimation of its current memory and swap use.
1293For example, if a task is using all allowed memory, its badness score will be
12941000. If it is using half of its allowed memory, its score will be 500.
1295
1296There is an additional factor included in the badness score: root
1297processes are given 3% extra memory over other tasks.
1298
1299The amount of "allowed" memory depends on the context in which the oom killer
1300was called. If it is due to the memory assigned to the allocating task's cpuset
1301being exhausted, the allowed memory represents the set of mems assigned to that
1302cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1303memory represents the set of mempolicy nodes. If it is due to a memory
1304limit (or swap limit) being reached, the allowed memory is that configured
1305limit. Finally, if it is due to the entire system being out of memory, the
1306allowed memory represents all allocatable resources.
1307
1308The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1309is used to determine which task to kill. Acceptable values range from -1000
1310(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1311polarize the preference for oom killing either by always preferring a certain
1312task or completely disabling it. The lowest possible value, -1000, is
1313equivalent to disabling oom killing entirely for that task since it will always
1314report a badness score of 0.
1315
1316Consequently, it is very simple for userspace to define the amount of memory to
1317consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1318example, is roughly equivalent to allowing the remainder of tasks sharing the
1319same system, cpuset, mempolicy, or memory controller resources to use at least
132050% more memory. A value of -500, on the other hand, would be roughly
1321equivalent to discounting 50% of the task's allowed memory from being considered
1322as scoring against the task.
1323
1324For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1325be used to tune the badness score. Its acceptable values range from -16
1326(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1327(OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1328scaled linearly with /proc/<pid>/oom_score_adj.
1329
1330Writing to /proc/<pid>/oom_score_adj or /proc/<pid>/oom_adj will change the
1331other with its scaled value.
1332
1333The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1334value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1335requires CAP_SYS_RESOURCE.
1336
1337NOTICE: /proc/<pid>/oom_adj is deprecated and will be removed, please see
1338Documentation/feature-removal-schedule.txt.
1339
1340Caveat: when a parent task is selected, the oom killer will sacrifice any first
1341generation children with separate address spaces instead, if possible. This
1342avoids servers and important system daemons from being killed and loses the
1343minimal amount of work.
1344
1345
13463.2 /proc/<pid>/oom_score - Display current oom-killer score
1347-------------------------------------------------------------
1348
1349This file can be used to check the current score used by the oom-killer is for
1350any given <pid>. Use it together with /proc/<pid>/oom_adj to tune which
1351process should be killed in an out-of-memory situation.
1352
1353
13543.3 /proc/<pid>/io - Display the IO accounting fields
1355-------------------------------------------------------
1356
1357This file contains IO statistics for each running process
1358
1359Example
1360-------
1361
1362test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1363[1] 3828
1364
1365test:/tmp # cat /proc/3828/io
1366rchar: 323934931
1367wchar: 323929600
1368syscr: 632687
1369syscw: 632675
1370read_bytes: 0
1371write_bytes: 323932160
1372cancelled_write_bytes: 0
1373
1374
1375Description
1376-----------
1377
1378rchar
1379-----
1380
1381I/O counter: chars read
1382The number of bytes which this task has caused to be read from storage. This
1383is simply the sum of bytes which this process passed to read() and pread().
1384It includes things like tty IO and it is unaffected by whether or not actual
1385physical disk IO was required (the read might have been satisfied from
1386pagecache)
1387
1388
1389wchar
1390-----
1391
1392I/O counter: chars written
1393The number of bytes which this task has caused, or shall cause to be written
1394to disk. Similar caveats apply here as with rchar.
1395
1396
1397syscr
1398-----
1399
1400I/O counter: read syscalls
1401Attempt to count the number of read I/O operations, i.e. syscalls like read()
1402and pread().
1403
1404
1405syscw
1406-----
1407
1408I/O counter: write syscalls
1409Attempt to count the number of write I/O operations, i.e. syscalls like
1410write() and pwrite().
1411
1412
1413read_bytes
1414----------
1415
1416I/O counter: bytes read
1417Attempt to count the number of bytes which this process really did cause to
1418be fetched from the storage layer. Done at the submit_bio() level, so it is
1419accurate for block-backed filesystems. <please add status regarding NFS and
1420CIFS at a later time>
1421
1422
1423write_bytes
1424-----------
1425
1426I/O counter: bytes written
1427Attempt to count the number of bytes which this process caused to be sent to
1428the storage layer. This is done at page-dirtying time.
1429
1430
1431cancelled_write_bytes
1432---------------------
1433
1434The big inaccuracy here is truncate. If a process writes 1MB to a file and
1435then deletes the file, it will in fact perform no writeout. But it will have
1436been accounted as having caused 1MB of write.
1437In other words: The number of bytes which this process caused to not happen,
1438by truncating pagecache. A task can cause "negative" IO too. If this task
1439truncates some dirty pagecache, some IO which another task has been accounted
1440for (in its write_bytes) will not be happening. We _could_ just subtract that
1441from the truncating task's write_bytes, but there is information loss in doing
1442that.
1443
1444
1445Note
1446----
1447
1448At its current implementation state, this is a bit racy on 32-bit machines: if
1449process A reads process B's /proc/pid/io while process B is updating one of
1450those 64-bit counters, process A could see an intermediate result.
1451
1452
1453More information about this can be found within the taskstats documentation in
1454Documentation/accounting.
1455
14563.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1457---------------------------------------------------------------
1458When a process is dumped, all anonymous memory is written to a core file as
1459long as the size of the core file isn't limited. But sometimes we don't want
1460to dump some memory segments, for example, huge shared memory. Conversely,
1461sometimes we want to save file-backed memory segments into a core file, not
1462only the individual files.
1463
1464/proc/<pid>/coredump_filter allows you to customize which memory segments
1465will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1466of memory types. If a bit of the bitmask is set, memory segments of the
1467corresponding memory type are dumped, otherwise they are not dumped.
1468
1469The following 7 memory types are supported:
1470 - (bit 0) anonymous private memory
1471 - (bit 1) anonymous shared memory
1472 - (bit 2) file-backed private memory
1473 - (bit 3) file-backed shared memory
1474 - (bit 4) ELF header pages in file-backed private memory areas (it is
1475 effective only if the bit 2 is cleared)
1476 - (bit 5) hugetlb private memory
1477 - (bit 6) hugetlb shared memory
1478
1479 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1480 are always dumped regardless of the bitmask status.
1481
1482 Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
1483 effected by bit 5-6.
1484
1485Default value of coredump_filter is 0x23; this means all anonymous memory
1486segments and hugetlb private memory are dumped.
1487
1488If you don't want to dump all shared memory segments attached to pid 1234,
1489write 0x21 to the process's proc file.
1490
1491 $ echo 0x21 > /proc/1234/coredump_filter
1492
1493When a new process is created, the process inherits the bitmask status from its
1494parent. It is useful to set up coredump_filter before the program runs.
1495For example:
1496
1497 $ echo 0x7 > /proc/self/coredump_filter
1498 $ ./some_program
1499
15003.5 /proc/<pid>/mountinfo - Information about mounts
1501--------------------------------------------------------
1502
1503This file contains lines of the form:
1504
150536 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1506(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1507
1508(1) mount ID: unique identifier of the mount (may be reused after umount)
1509(2) parent ID: ID of parent (or of self for the top of the mount tree)
1510(3) major:minor: value of st_dev for files on filesystem
1511(4) root: root of the mount within the filesystem
1512(5) mount point: mount point relative to the process's root
1513(6) mount options: per mount options
1514(7) optional fields: zero or more fields of the form "tag[:value]"
1515(8) separator: marks the end of the optional fields
1516(9) filesystem type: name of filesystem of the form "type[.subtype]"
1517(10) mount source: filesystem specific information or "none"
1518(11) super options: per super block options
1519
1520Parsers should ignore all unrecognised optional fields. Currently the
1521possible optional fields are:
1522
1523shared:X mount is shared in peer group X
1524master:X mount is slave to peer group X
1525propagate_from:X mount is slave and receives propagation from peer group X (*)
1526unbindable mount is unbindable
1527
1528(*) X is the closest dominant peer group under the process's root. If
1529X is the immediate master of the mount, or if there's no dominant peer
1530group under the same root, then only the "master:X" field is present
1531and not the "propagate_from:X" field.
1532
1533For more information on mount propagation see:
1534
1535 Documentation/filesystems/sharedsubtree.txt
1536
1537
15383.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1539--------------------------------------------------------
1540These files provide a method to access a tasks comm value. It also allows for
1541a task to set its own or one of its thread siblings comm value. The comm value
1542is limited in size compared to the cmdline value, so writing anything longer
1543then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1544comm value.