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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
48 4 Configuring procfs
49 4.1 Mount options
50
51------------------------------------------------------------------------------
52Preface
53------------------------------------------------------------------------------
54
550.1 Introduction/Credits
56------------------------
57
58This documentation is part of a soon (or so we hope) to be released book on
59the SuSE Linux distribution. As there is no complete documentation for the
60/proc file system and we've used many freely available sources to write these
61chapters, it seems only fair to give the work back to the Linux community.
62This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
63afraid it's still far from complete, but we hope it will be useful. As far as
64we know, it is the first 'all-in-one' document about the /proc file system. It
65is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
66SPARC, AXP, etc., features, you probably won't find what you are looking for.
67It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
68additions and patches are welcome and will be added to this document if you
69mail them to Bodo.
70
71We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
72other people for help compiling this documentation. We'd also like to extend a
73special thank you to Andi Kleen for documentation, which we relied on heavily
74to create this document, as well as the additional information he provided.
75Thanks to everybody else who contributed source or docs to the Linux kernel
76and helped create a great piece of software... :)
77
78If you have any comments, corrections or additions, please don't hesitate to
79contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
80document.
81
82The latest version of this document is available online at
83http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
84
85If the above direction does not works for you, you could try the kernel
86mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
87comandante@zaralinux.com.
88
890.2 Legal Stuff
90---------------
91
92We don't guarantee the correctness of this document, and if you come to us
93complaining about how you screwed up your system because of incorrect
94documentation, we won't feel responsible...
95
96------------------------------------------------------------------------------
97CHAPTER 1: COLLECTING SYSTEM INFORMATION
98------------------------------------------------------------------------------
99
100------------------------------------------------------------------------------
101In This Chapter
102------------------------------------------------------------------------------
103* Investigating the properties of the pseudo file system /proc and its
104 ability to provide information on the running Linux system
105* Examining /proc's structure
106* Uncovering various information about the kernel and the processes running
107 on the system
108------------------------------------------------------------------------------
109
110
111The proc file system acts as an interface to internal data structures in the
112kernel. It can be used to obtain information about the system and to change
113certain kernel parameters at runtime (sysctl).
114
115First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
116show you how you can use /proc/sys to change settings.
117
1181.1 Process-Specific Subdirectories
119-----------------------------------
120
121The directory /proc contains (among other things) one subdirectory for each
122process running on the system, which is named after the process ID (PID).
123
124The link self points to the process reading the file system. Each process
125subdirectory has the entries listed in Table 1-1.
126
127
128Table 1-1: Process specific entries in /proc
129..............................................................................
130 File Content
131 clear_refs Clears page referenced bits shown in smaps output
132 cmdline Command line arguments
133 cpu Current and last cpu in which it was executed (2.4)(smp)
134 cwd Link to the current working directory
135 environ Values of environment variables
136 exe Link to the executable of this process
137 fd Directory, which contains all file descriptors
138 maps Memory maps to executables and library files (2.4)
139 mem Memory held by this process
140 root Link to the root directory of this process
141 stat Process status
142 statm Process memory status information
143 status Process status in human readable form
144 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function
145 symbol the task is blocked in - or "0" if not blocked.
146 pagemap Page table
147 stack Report full stack trace, enable via CONFIG_STACKTRACE
148 smaps a extension based on maps, showing the memory consumption of
149 each mapping and flags associated with it
150 numa_maps an extension based on maps, showing the memory locality and
151 binding policy as well as mem usage (in pages) of each mapping.
152..............................................................................
153
154For example, to get the status information of a process, all you have to do is
155read the file /proc/PID/status:
156
157 >cat /proc/self/status
158 Name: cat
159 State: R (running)
160 Tgid: 5452
161 Pid: 5452
162 PPid: 743
163 TracerPid: 0 (2.4)
164 Uid: 501 501 501 501
165 Gid: 100 100 100 100
166 FDSize: 256
167 Groups: 100 14 16
168 VmPeak: 5004 kB
169 VmSize: 5004 kB
170 VmLck: 0 kB
171 VmHWM: 476 kB
172 VmRSS: 476 kB
173 RssAnon: 352 kB
174 RssFile: 120 kB
175 RssShmem: 4 kB
176 VmData: 156 kB
177 VmStk: 88 kB
178 VmExe: 68 kB
179 VmLib: 1412 kB
180 VmPTE: 20 kb
181 VmSwap: 0 kB
182 HugetlbPages: 0 kB
183 Threads: 1
184 SigQ: 0/28578
185 SigPnd: 0000000000000000
186 ShdPnd: 0000000000000000
187 SigBlk: 0000000000000000
188 SigIgn: 0000000000000000
189 SigCgt: 0000000000000000
190 CapInh: 00000000fffffeff
191 CapPrm: 0000000000000000
192 CapEff: 0000000000000000
193 CapBnd: ffffffffffffffff
194 Seccomp: 0
195 voluntary_ctxt_switches: 0
196 nonvoluntary_ctxt_switches: 1
197
198This shows you nearly the same information you would get if you viewed it with
199the ps command. In fact, ps uses the proc file system to obtain its
200information. But you get a more detailed view of the process by reading the
201file /proc/PID/status. It fields are described in table 1-2.
202
203The statm file contains more detailed information about the process
204memory usage. Its seven fields are explained in Table 1-3. The stat file
205contains details information about the process itself. Its fields are
206explained in Table 1-4.
207
208(for SMP CONFIG users)
209For making accounting scalable, RSS related information are handled in an
210asynchronous manner and the value may not be very precise. To see a precise
211snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
212It's slow but very precise.
213
214Table 1-2: Contents of the status files (as of 4.1)
215..............................................................................
216 Field Content
217 Name filename of the executable
218 State state (R is running, S is sleeping, D is sleeping
219 in an uninterruptible wait, Z is zombie,
220 T is traced or stopped)
221 Tgid thread group ID
222 Ngid NUMA group ID (0 if none)
223 Pid process id
224 PPid process id of the parent process
225 TracerPid PID of process tracing this process (0 if not)
226 Uid Real, effective, saved set, and file system UIDs
227 Gid Real, effective, saved set, and file system GIDs
228 FDSize number of file descriptor slots currently allocated
229 Groups supplementary group list
230 NStgid descendant namespace thread group ID hierarchy
231 NSpid descendant namespace process ID hierarchy
232 NSpgid descendant namespace process group ID hierarchy
233 NSsid descendant namespace session ID hierarchy
234 VmPeak peak virtual memory size
235 VmSize total program size
236 VmLck locked memory size
237 VmHWM peak resident set size ("high water mark")
238 VmRSS size of memory portions. It contains the three
239 following parts (VmRSS = RssAnon + RssFile + RssShmem)
240 RssAnon size of resident anonymous memory
241 RssFile size of resident file mappings
242 RssShmem size of resident shmem memory (includes SysV shm,
243 mapping of tmpfs and shared anonymous mappings)
244 VmData size of private data segments
245 VmStk size of stack segments
246 VmExe size of text segment
247 VmLib size of shared library code
248 VmPTE size of page table entries
249 VmPMD size of second level page tables
250 VmSwap amount of swap used by anonymous private data
251 (shmem swap usage is not included)
252 HugetlbPages size of hugetlb memory portions
253 Threads number of threads
254 SigQ number of signals queued/max. number for queue
255 SigPnd bitmap of pending signals for the thread
256 ShdPnd bitmap of shared pending signals for the process
257 SigBlk bitmap of blocked signals
258 SigIgn bitmap of ignored signals
259 SigCgt bitmap of caught signals
260 CapInh bitmap of inheritable capabilities
261 CapPrm bitmap of permitted capabilities
262 CapEff bitmap of effective capabilities
263 CapBnd bitmap of capabilities bounding set
264 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
265 Cpus_allowed mask of CPUs on which this process may run
266 Cpus_allowed_list Same as previous, but in "list format"
267 Mems_allowed mask of memory nodes allowed to this process
268 Mems_allowed_list Same as previous, but in "list format"
269 voluntary_ctxt_switches number of voluntary context switches
270 nonvoluntary_ctxt_switches number of non voluntary context switches
271..............................................................................
272
273Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
274..............................................................................
275 Field Content
276 size total program size (pages) (same as VmSize in status)
277 resident size of memory portions (pages) (same as VmRSS in status)
278 shared number of pages that are shared (i.e. backed by a file, same
279 as RssFile+RssShmem in status)
280 trs number of pages that are 'code' (not including libs; broken,
281 includes data segment)
282 lrs number of pages of library (always 0 on 2.6)
283 drs number of pages of data/stack (including libs; broken,
284 includes library text)
285 dt number of dirty pages (always 0 on 2.6)
286..............................................................................
287
288
289Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
290..............................................................................
291 Field Content
292 pid process id
293 tcomm filename of the executable
294 state state (R is running, S is sleeping, D is sleeping in an
295 uninterruptible wait, Z is zombie, T is traced or stopped)
296 ppid process id of the parent process
297 pgrp pgrp of the process
298 sid session id
299 tty_nr tty the process uses
300 tty_pgrp pgrp of the tty
301 flags task flags
302 min_flt number of minor faults
303 cmin_flt number of minor faults with child's
304 maj_flt number of major faults
305 cmaj_flt number of major faults with child's
306 utime user mode jiffies
307 stime kernel mode jiffies
308 cutime user mode jiffies with child's
309 cstime kernel mode jiffies with child's
310 priority priority level
311 nice nice level
312 num_threads number of threads
313 it_real_value (obsolete, always 0)
314 start_time time the process started after system boot
315 vsize virtual memory size
316 rss resident set memory size
317 rsslim current limit in bytes on the rss
318 start_code address above which program text can run
319 end_code address below which program text can run
320 start_stack address of the start of the main process stack
321 esp current value of ESP
322 eip current value of EIP
323 pending bitmap of pending signals
324 blocked bitmap of blocked signals
325 sigign bitmap of ignored signals
326 sigcatch bitmap of caught signals
327 0 (place holder, used to be the wchan address, use /proc/PID/wchan instead)
328 0 (place holder)
329 0 (place holder)
330 exit_signal signal to send to parent thread on exit
331 task_cpu which CPU the task is scheduled on
332 rt_priority realtime priority
333 policy scheduling policy (man sched_setscheduler)
334 blkio_ticks time spent waiting for block IO
335 gtime guest time of the task in jiffies
336 cgtime guest time of the task children in jiffies
337 start_data address above which program data+bss is placed
338 end_data address below which program data+bss is placed
339 start_brk address above which program heap can be expanded with brk()
340 arg_start address above which program command line is placed
341 arg_end address below which program command line is placed
342 env_start address above which program environment is placed
343 env_end address below which program environment is placed
344 exit_code the thread's exit_code in the form reported by the waitpid system call
345..............................................................................
346
347The /proc/PID/maps file containing the currently mapped memory regions and
348their access permissions.
349
350The format is:
351
352address perms offset dev inode pathname
353
35408048000-08049000 r-xp 00000000 03:00 8312 /opt/test
35508049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
3560804a000-0806b000 rw-p 00000000 00:00 0 [heap]
357a7cb1000-a7cb2000 ---p 00000000 00:00 0
358a7cb2000-a7eb2000 rw-p 00000000 00:00 0
359a7eb2000-a7eb3000 ---p 00000000 00:00 0
360a7eb3000-a7ed5000 rw-p 00000000 00:00 0
361a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
362a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
363a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
364a800b000-a800e000 rw-p 00000000 00:00 0
365a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
366a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
367a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
368a8024000-a8027000 rw-p 00000000 00:00 0
369a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
370a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
371a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
372aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
373ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
374
375where "address" is the address space in the process that it occupies, "perms"
376is a set of permissions:
377
378 r = read
379 w = write
380 x = execute
381 s = shared
382 p = private (copy on write)
383
384"offset" is the offset into the mapping, "dev" is the device (major:minor), and
385"inode" is the inode on that device. 0 indicates that no inode is associated
386with the memory region, as the case would be with BSS (uninitialized data).
387The "pathname" shows the name associated file for this mapping. If the mapping
388is not associated with a file:
389
390 [heap] = the heap of the program
391 [stack] = the stack of the main process
392 [vdso] = the "virtual dynamic shared object",
393 the kernel system call handler
394
395 or if empty, the mapping is anonymous.
396
397The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint
398of the individual tasks of a process. In this file you will see a mapping marked
399as [stack] if that task sees it as a stack. Hence, for the example above, the
400task-level map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this:
401
40208048000-08049000 r-xp 00000000 03:00 8312 /opt/test
40308049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
4040804a000-0806b000 rw-p 00000000 00:00 0 [heap]
405a7cb1000-a7cb2000 ---p 00000000 00:00 0
406a7cb2000-a7eb2000 rw-p 00000000 00:00 0
407a7eb2000-a7eb3000 ---p 00000000 00:00 0
408a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack]
409a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
410a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
411a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
412a800b000-a800e000 rw-p 00000000 00:00 0
413a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
414a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
415a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
416a8024000-a8027000 rw-p 00000000 00:00 0
417a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
418a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
419a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
420aff35000-aff4a000 rw-p 00000000 00:00 0
421ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
422
423The /proc/PID/smaps is an extension based on maps, showing the memory
424consumption for each of the process's mappings. For each of mappings there
425is a series of lines such as the following:
426
42708048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
428Size: 1084 kB
429Rss: 892 kB
430Pss: 374 kB
431Shared_Clean: 892 kB
432Shared_Dirty: 0 kB
433Private_Clean: 0 kB
434Private_Dirty: 0 kB
435Referenced: 892 kB
436Anonymous: 0 kB
437AnonHugePages: 0 kB
438Shared_Hugetlb: 0 kB
439Private_Hugetlb: 0 kB
440Swap: 0 kB
441SwapPss: 0 kB
442KernelPageSize: 4 kB
443MMUPageSize: 4 kB
444Locked: 0 kB
445VmFlags: rd ex mr mw me dw
446
447the first of these lines shows the same information as is displayed for the
448mapping in /proc/PID/maps. The remaining lines show the size of the mapping
449(size), the amount of the mapping that is currently resident in RAM (RSS), the
450process' proportional share of this mapping (PSS), the number of clean and
451dirty private pages in the mapping.
452
453The "proportional set size" (PSS) of a process is the count of pages it has
454in memory, where each page is divided by the number of processes sharing it.
455So if a process has 1000 pages all to itself, and 1000 shared with one other
456process, its PSS will be 1500.
457Note that even a page which is part of a MAP_SHARED mapping, but has only
458a single pte mapped, i.e. is currently used by only one process, is accounted
459as private and not as shared.
460"Referenced" indicates the amount of memory currently marked as referenced or
461accessed.
462"Anonymous" shows the amount of memory that does not belong to any file. Even
463a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
464and a page is modified, the file page is replaced by a private anonymous copy.
465"AnonHugePages" shows the ammount of memory backed by transparent hugepage.
466"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
467hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
468reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
469"Swap" shows how much would-be-anonymous memory is also used, but out on swap.
470For shmem mappings, "Swap" includes also the size of the mapped (and not
471replaced by copy-on-write) part of the underlying shmem object out on swap.
472"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
473does not take into account swapped out page of underlying shmem objects.
474"Locked" indicates whether the mapping is locked in memory or not.
475
476"VmFlags" field deserves a separate description. This member represents the kernel
477flags associated with the particular virtual memory area in two letter encoded
478manner. The codes are the following:
479 rd - readable
480 wr - writeable
481 ex - executable
482 sh - shared
483 mr - may read
484 mw - may write
485 me - may execute
486 ms - may share
487 gd - stack segment growns down
488 pf - pure PFN range
489 dw - disabled write to the mapped file
490 lo - pages are locked in memory
491 io - memory mapped I/O area
492 sr - sequential read advise provided
493 rr - random read advise provided
494 dc - do not copy area on fork
495 de - do not expand area on remapping
496 ac - area is accountable
497 nr - swap space is not reserved for the area
498 ht - area uses huge tlb pages
499 ar - architecture specific flag
500 dd - do not include area into core dump
501 sd - soft-dirty flag
502 mm - mixed map area
503 hg - huge page advise flag
504 nh - no-huge page advise flag
505 mg - mergable advise flag
506
507Note that there is no guarantee that every flag and associated mnemonic will
508be present in all further kernel releases. Things get changed, the flags may
509be vanished or the reverse -- new added.
510
511This file is only present if the CONFIG_MMU kernel configuration option is
512enabled.
513
514The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
515bits on both physical and virtual pages associated with a process, and the
516soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details).
517To clear the bits for all the pages associated with the process
518 > echo 1 > /proc/PID/clear_refs
519
520To clear the bits for the anonymous pages associated with the process
521 > echo 2 > /proc/PID/clear_refs
522
523To clear the bits for the file mapped pages associated with the process
524 > echo 3 > /proc/PID/clear_refs
525
526To clear the soft-dirty bit
527 > echo 4 > /proc/PID/clear_refs
528
529To reset the peak resident set size ("high water mark") to the process's
530current value:
531 > echo 5 > /proc/PID/clear_refs
532
533Any other value written to /proc/PID/clear_refs will have no effect.
534
535The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
536using /proc/kpageflags and number of times a page is mapped using
537/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
538
539The /proc/pid/numa_maps is an extension based on maps, showing the memory
540locality and binding policy, as well as the memory usage (in pages) of
541each mapping. The output follows a general format where mapping details get
542summarized separated by blank spaces, one mapping per each file line:
543
544address policy mapping details
545
54600400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
54700600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5483206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
549320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5503206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5513206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5523206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
553320698b000 default file=/lib64/libc-2.12.so
5543206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
5553206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5563206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
5577f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
5587f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
5597f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
5607fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
5617fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
562
563Where:
564"address" is the starting address for the mapping;
565"policy" reports the NUMA memory policy set for the mapping (see vm/numa_memory_policy.txt);
566"mapping details" summarizes mapping data such as mapping type, page usage counters,
567node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
568size, in KB, that is backing the mapping up.
569
5701.2 Kernel data
571---------------
572
573Similar to the process entries, the kernel data files give information about
574the running kernel. The files used to obtain this information are contained in
575/proc and are listed in Table 1-5. Not all of these will be present in your
576system. It depends on the kernel configuration and the loaded modules, which
577files are there, and which are missing.
578
579Table 1-5: Kernel info in /proc
580..............................................................................
581 File Content
582 apm Advanced power management info
583 buddyinfo Kernel memory allocator information (see text) (2.5)
584 bus Directory containing bus specific information
585 cmdline Kernel command line
586 cpuinfo Info about the CPU
587 devices Available devices (block and character)
588 dma Used DMS channels
589 filesystems Supported filesystems
590 driver Various drivers grouped here, currently rtc (2.4)
591 execdomains Execdomains, related to security (2.4)
592 fb Frame Buffer devices (2.4)
593 fs File system parameters, currently nfs/exports (2.4)
594 ide Directory containing info about the IDE subsystem
595 interrupts Interrupt usage
596 iomem Memory map (2.4)
597 ioports I/O port usage
598 irq Masks for irq to cpu affinity (2.4)(smp?)
599 isapnp ISA PnP (Plug&Play) Info (2.4)
600 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
601 kmsg Kernel messages
602 ksyms Kernel symbol table
603 loadavg Load average of last 1, 5 & 15 minutes
604 locks Kernel locks
605 meminfo Memory info
606 misc Miscellaneous
607 modules List of loaded modules
608 mounts Mounted filesystems
609 net Networking info (see text)
610 pagetypeinfo Additional page allocator information (see text) (2.5)
611 partitions Table of partitions known to the system
612 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
613 decoupled by lspci (2.4)
614 rtc Real time clock
615 scsi SCSI info (see text)
616 slabinfo Slab pool info
617 softirqs softirq usage
618 stat Overall statistics
619 swaps Swap space utilization
620 sys See chapter 2
621 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
622 tty Info of tty drivers
623 uptime Wall clock since boot, combined idle time of all cpus
624 version Kernel version
625 video bttv info of video resources (2.4)
626 vmallocinfo Show vmalloced areas
627..............................................................................
628
629You can, for example, check which interrupts are currently in use and what
630they are used for by looking in the file /proc/interrupts:
631
632 > cat /proc/interrupts
633 CPU0
634 0: 8728810 XT-PIC timer
635 1: 895 XT-PIC keyboard
636 2: 0 XT-PIC cascade
637 3: 531695 XT-PIC aha152x
638 4: 2014133 XT-PIC serial
639 5: 44401 XT-PIC pcnet_cs
640 8: 2 XT-PIC rtc
641 11: 8 XT-PIC i82365
642 12: 182918 XT-PIC PS/2 Mouse
643 13: 1 XT-PIC fpu
644 14: 1232265 XT-PIC ide0
645 15: 7 XT-PIC ide1
646 NMI: 0
647
648In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
649output of a SMP machine):
650
651 > cat /proc/interrupts
652
653 CPU0 CPU1
654 0: 1243498 1214548 IO-APIC-edge timer
655 1: 8949 8958 IO-APIC-edge keyboard
656 2: 0 0 XT-PIC cascade
657 5: 11286 10161 IO-APIC-edge soundblaster
658 8: 1 0 IO-APIC-edge rtc
659 9: 27422 27407 IO-APIC-edge 3c503
660 12: 113645 113873 IO-APIC-edge PS/2 Mouse
661 13: 0 0 XT-PIC fpu
662 14: 22491 24012 IO-APIC-edge ide0
663 15: 2183 2415 IO-APIC-edge ide1
664 17: 30564 30414 IO-APIC-level eth0
665 18: 177 164 IO-APIC-level bttv
666 NMI: 2457961 2457959
667 LOC: 2457882 2457881
668 ERR: 2155
669
670NMI is incremented in this case because every timer interrupt generates a NMI
671(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
672
673LOC is the local interrupt counter of the internal APIC of every CPU.
674
675ERR is incremented in the case of errors in the IO-APIC bus (the bus that
676connects the CPUs in a SMP system. This means that an error has been detected,
677the IO-APIC automatically retry the transmission, so it should not be a big
678problem, but you should read the SMP-FAQ.
679
680In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
681/proc/interrupts to display every IRQ vector in use by the system, not
682just those considered 'most important'. The new vectors are:
683
684 THR -- interrupt raised when a machine check threshold counter
685 (typically counting ECC corrected errors of memory or cache) exceeds
686 a configurable threshold. Only available on some systems.
687
688 TRM -- a thermal event interrupt occurs when a temperature threshold
689 has been exceeded for the CPU. This interrupt may also be generated
690 when the temperature drops back to normal.
691
692 SPU -- a spurious interrupt is some interrupt that was raised then lowered
693 by some IO device before it could be fully processed by the APIC. Hence
694 the APIC sees the interrupt but does not know what device it came from.
695 For this case the APIC will generate the interrupt with a IRQ vector
696 of 0xff. This might also be generated by chipset bugs.
697
698 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
699 sent from one CPU to another per the needs of the OS. Typically,
700 their statistics are used by kernel developers and interested users to
701 determine the occurrence of interrupts of the given type.
702
703The above IRQ vectors are displayed only when relevant. For example,
704the threshold vector does not exist on x86_64 platforms. Others are
705suppressed when the system is a uniprocessor. As of this writing, only
706i386 and x86_64 platforms support the new IRQ vector displays.
707
708Of some interest is the introduction of the /proc/irq directory to 2.4.
709It could be used to set IRQ to CPU affinity, this means that you can "hook" an
710IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
711irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
712prof_cpu_mask.
713
714For example
715 > ls /proc/irq/
716 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
717 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
718 > ls /proc/irq/0/
719 smp_affinity
720
721smp_affinity is a bitmask, in which you can specify which CPUs can handle the
722IRQ, you can set it by doing:
723
724 > echo 1 > /proc/irq/10/smp_affinity
725
726This means that only the first CPU will handle the IRQ, but you can also echo
7275 which means that only the first and fourth CPU can handle the IRQ.
728
729The contents of each smp_affinity file is the same by default:
730
731 > cat /proc/irq/0/smp_affinity
732 ffffffff
733
734There is an alternate interface, smp_affinity_list which allows specifying
735a cpu range instead of a bitmask:
736
737 > cat /proc/irq/0/smp_affinity_list
738 1024-1031
739
740The default_smp_affinity mask applies to all non-active IRQs, which are the
741IRQs which have not yet been allocated/activated, and hence which lack a
742/proc/irq/[0-9]* directory.
743
744The node file on an SMP system shows the node to which the device using the IRQ
745reports itself as being attached. This hardware locality information does not
746include information about any possible driver locality preference.
747
748prof_cpu_mask specifies which CPUs are to be profiled by the system wide
749profiler. Default value is ffffffff (all cpus if there are only 32 of them).
750
751The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
752between all the CPUs which are allowed to handle it. As usual the kernel has
753more info than you and does a better job than you, so the defaults are the
754best choice for almost everyone. [Note this applies only to those IO-APIC's
755that support "Round Robin" interrupt distribution.]
756
757There are three more important subdirectories in /proc: net, scsi, and sys.
758The general rule is that the contents, or even the existence of these
759directories, depend on your kernel configuration. If SCSI is not enabled, the
760directory scsi may not exist. The same is true with the net, which is there
761only when networking support is present in the running kernel.
762
763The slabinfo file gives information about memory usage at the slab level.
764Linux uses slab pools for memory management above page level in version 2.2.
765Commonly used objects have their own slab pool (such as network buffers,
766directory cache, and so on).
767
768..............................................................................
769
770> cat /proc/buddyinfo
771
772Node 0, zone DMA 0 4 5 4 4 3 ...
773Node 0, zone Normal 1 0 0 1 101 8 ...
774Node 0, zone HighMem 2 0 0 1 1 0 ...
775
776External fragmentation is a problem under some workloads, and buddyinfo is a
777useful tool for helping diagnose these problems. Buddyinfo will give you a
778clue as to how big an area you can safely allocate, or why a previous
779allocation failed.
780
781Each column represents the number of pages of a certain order which are
782available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
783ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
784available in ZONE_NORMAL, etc...
785
786More information relevant to external fragmentation can be found in
787pagetypeinfo.
788
789> cat /proc/pagetypeinfo
790Page block order: 9
791Pages per block: 512
792
793Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
794Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
795Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
796Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
797Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
798Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
799Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
800Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
801Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
802Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
803Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
804
805Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
806Node 0, zone DMA 2 0 5 1 0
807Node 0, zone DMA32 41 6 967 2 0
808
809Fragmentation avoidance in the kernel works by grouping pages of different
810migrate types into the same contiguous regions of memory called page blocks.
811A page block is typically the size of the default hugepage size e.g. 2MB on
812X86-64. By keeping pages grouped based on their ability to move, the kernel
813can reclaim pages within a page block to satisfy a high-order allocation.
814
815The pagetypinfo begins with information on the size of a page block. It
816then gives the same type of information as buddyinfo except broken down
817by migrate-type and finishes with details on how many page blocks of each
818type exist.
819
820If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
821from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
822make an estimate of the likely number of huge pages that can be allocated
823at a given point in time. All the "Movable" blocks should be allocatable
824unless memory has been mlock()'d. Some of the Reclaimable blocks should
825also be allocatable although a lot of filesystem metadata may have to be
826reclaimed to achieve this.
827
828..............................................................................
829
830meminfo:
831
832Provides information about distribution and utilization of memory. This
833varies by architecture and compile options. The following is from a
83416GB PIII, which has highmem enabled. You may not have all of these fields.
835
836> cat /proc/meminfo
837
838MemTotal: 16344972 kB
839MemFree: 13634064 kB
840MemAvailable: 14836172 kB
841Buffers: 3656 kB
842Cached: 1195708 kB
843SwapCached: 0 kB
844Active: 891636 kB
845Inactive: 1077224 kB
846HighTotal: 15597528 kB
847HighFree: 13629632 kB
848LowTotal: 747444 kB
849LowFree: 4432 kB
850SwapTotal: 0 kB
851SwapFree: 0 kB
852Dirty: 968 kB
853Writeback: 0 kB
854AnonPages: 861800 kB
855Mapped: 280372 kB
856Shmem: 644 kB
857Slab: 284364 kB
858SReclaimable: 159856 kB
859SUnreclaim: 124508 kB
860PageTables: 24448 kB
861NFS_Unstable: 0 kB
862Bounce: 0 kB
863WritebackTmp: 0 kB
864CommitLimit: 7669796 kB
865Committed_AS: 100056 kB
866VmallocTotal: 112216 kB
867VmallocUsed: 428 kB
868VmallocChunk: 111088 kB
869AnonHugePages: 49152 kB
870
871 MemTotal: Total usable ram (i.e. physical ram minus a few reserved
872 bits and the kernel binary code)
873 MemFree: The sum of LowFree+HighFree
874MemAvailable: An estimate of how much memory is available for starting new
875 applications, without swapping. Calculated from MemFree,
876 SReclaimable, the size of the file LRU lists, and the low
877 watermarks in each zone.
878 The estimate takes into account that the system needs some
879 page cache to function well, and that not all reclaimable
880 slab will be reclaimable, due to items being in use. The
881 impact of those factors will vary from system to system.
882 Buffers: Relatively temporary storage for raw disk blocks
883 shouldn't get tremendously large (20MB or so)
884 Cached: in-memory cache for files read from the disk (the
885 pagecache). Doesn't include SwapCached
886 SwapCached: Memory that once was swapped out, is swapped back in but
887 still also is in the swapfile (if memory is needed it
888 doesn't need to be swapped out AGAIN because it is already
889 in the swapfile. This saves I/O)
890 Active: Memory that has been used more recently and usually not
891 reclaimed unless absolutely necessary.
892 Inactive: Memory which has been less recently used. It is more
893 eligible to be reclaimed for other purposes
894 HighTotal:
895 HighFree: Highmem is all memory above ~860MB of physical memory
896 Highmem areas are for use by userspace programs, or
897 for the pagecache. The kernel must use tricks to access
898 this memory, making it slower to access than lowmem.
899 LowTotal:
900 LowFree: Lowmem is memory which can be used for everything that
901 highmem can be used for, but it is also available for the
902 kernel's use for its own data structures. Among many
903 other things, it is where everything from the Slab is
904 allocated. Bad things happen when you're out of lowmem.
905 SwapTotal: total amount of swap space available
906 SwapFree: Memory which has been evicted from RAM, and is temporarily
907 on the disk
908 Dirty: Memory which is waiting to get written back to the disk
909 Writeback: Memory which is actively being written back to the disk
910 AnonPages: Non-file backed pages mapped into userspace page tables
911AnonHugePages: Non-file backed huge pages mapped into userspace page tables
912 Mapped: files which have been mmaped, such as libraries
913 Shmem: Total memory used by shared memory (shmem) and tmpfs
914 Slab: in-kernel data structures cache
915SReclaimable: Part of Slab, that might be reclaimed, such as caches
916 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
917 PageTables: amount of memory dedicated to the lowest level of page
918 tables.
919NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
920 storage
921 Bounce: Memory used for block device "bounce buffers"
922WritebackTmp: Memory used by FUSE for temporary writeback buffers
923 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
924 this is the total amount of memory currently available to
925 be allocated on the system. This limit is only adhered to
926 if strict overcommit accounting is enabled (mode 2 in
927 'vm.overcommit_memory').
928 The CommitLimit is calculated with the following formula:
929 CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
930 overcommit_ratio / 100 + [total swap pages]
931 For example, on a system with 1G of physical RAM and 7G
932 of swap with a `vm.overcommit_ratio` of 30 it would
933 yield a CommitLimit of 7.3G.
934 For more details, see the memory overcommit documentation
935 in vm/overcommit-accounting.
936Committed_AS: The amount of memory presently allocated on the system.
937 The committed memory is a sum of all of the memory which
938 has been allocated by processes, even if it has not been
939 "used" by them as of yet. A process which malloc()'s 1G
940 of memory, but only touches 300M of it will show up as
941 using 1G. This 1G is memory which has been "committed" to
942 by the VM and can be used at any time by the allocating
943 application. With strict overcommit enabled on the system
944 (mode 2 in 'vm.overcommit_memory'),allocations which would
945 exceed the CommitLimit (detailed above) will not be permitted.
946 This is useful if one needs to guarantee that processes will
947 not fail due to lack of memory once that memory has been
948 successfully allocated.
949VmallocTotal: total size of vmalloc memory area
950 VmallocUsed: amount of vmalloc area which is used
951VmallocChunk: largest contiguous block of vmalloc area which is free
952
953..............................................................................
954
955vmallocinfo:
956
957Provides information about vmalloced/vmaped areas. One line per area,
958containing the virtual address range of the area, size in bytes,
959caller information of the creator, and optional information depending
960on the kind of area :
961
962 pages=nr number of pages
963 phys=addr if a physical address was specified
964 ioremap I/O mapping (ioremap() and friends)
965 vmalloc vmalloc() area
966 vmap vmap()ed pages
967 user VM_USERMAP area
968 vpages buffer for pages pointers was vmalloced (huge area)
969 N<node>=nr (Only on NUMA kernels)
970 Number of pages allocated on memory node <node>
971
972> cat /proc/vmallocinfo
9730xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
974 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
9750xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
976 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
9770xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
978 phys=7fee8000 ioremap
9790xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
980 phys=7fee7000 ioremap
9810xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
9820xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
983 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
9840xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
985 pages=2 vmalloc N1=2
9860xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
987 /0x130 [x_tables] pages=4 vmalloc N0=4
9880xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
989 pages=14 vmalloc N2=14
9900xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
991 pages=4 vmalloc N1=4
9920xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
993 pages=2 vmalloc N1=2
9940xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
995 pages=10 vmalloc N0=10
996
997..............................................................................
998
999softirqs:
1000
1001Provides counts of softirq handlers serviced since boot time, for each cpu.
1002
1003> cat /proc/softirqs
1004 CPU0 CPU1 CPU2 CPU3
1005 HI: 0 0 0 0
1006 TIMER: 27166 27120 27097 27034
1007 NET_TX: 0 0 0 17
1008 NET_RX: 42 0 0 39
1009 BLOCK: 0 0 107 1121
1010 TASKLET: 0 0 0 290
1011 SCHED: 27035 26983 26971 26746
1012 HRTIMER: 0 0 0 0
1013 RCU: 1678 1769 2178 2250
1014
1015
10161.3 IDE devices in /proc/ide
1017----------------------------
1018
1019The subdirectory /proc/ide contains information about all IDE devices of which
1020the kernel is aware. There is one subdirectory for each IDE controller, the
1021file drivers and a link for each IDE device, pointing to the device directory
1022in the controller specific subtree.
1023
1024The file drivers contains general information about the drivers used for the
1025IDE devices:
1026
1027 > cat /proc/ide/drivers
1028 ide-cdrom version 4.53
1029 ide-disk version 1.08
1030
1031More detailed information can be found in the controller specific
1032subdirectories. These are named ide0, ide1 and so on. Each of these
1033directories contains the files shown in table 1-6.
1034
1035
1036Table 1-6: IDE controller info in /proc/ide/ide?
1037..............................................................................
1038 File Content
1039 channel IDE channel (0 or 1)
1040 config Configuration (only for PCI/IDE bridge)
1041 mate Mate name
1042 model Type/Chipset of IDE controller
1043..............................................................................
1044
1045Each device connected to a controller has a separate subdirectory in the
1046controllers directory. The files listed in table 1-7 are contained in these
1047directories.
1048
1049
1050Table 1-7: IDE device information
1051..............................................................................
1052 File Content
1053 cache The cache
1054 capacity Capacity of the medium (in 512Byte blocks)
1055 driver driver and version
1056 geometry physical and logical geometry
1057 identify device identify block
1058 media media type
1059 model device identifier
1060 settings device setup
1061 smart_thresholds IDE disk management thresholds
1062 smart_values IDE disk management values
1063..............................................................................
1064
1065The most interesting file is settings. This file contains a nice overview of
1066the drive parameters:
1067
1068 # cat /proc/ide/ide0/hda/settings
1069 name value min max mode
1070 ---- ----- --- --- ----
1071 bios_cyl 526 0 65535 rw
1072 bios_head 255 0 255 rw
1073 bios_sect 63 0 63 rw
1074 breada_readahead 4 0 127 rw
1075 bswap 0 0 1 r
1076 file_readahead 72 0 2097151 rw
1077 io_32bit 0 0 3 rw
1078 keepsettings 0 0 1 rw
1079 max_kb_per_request 122 1 127 rw
1080 multcount 0 0 8 rw
1081 nice1 1 0 1 rw
1082 nowerr 0 0 1 rw
1083 pio_mode write-only 0 255 w
1084 slow 0 0 1 rw
1085 unmaskirq 0 0 1 rw
1086 using_dma 0 0 1 rw
1087
1088
10891.4 Networking info in /proc/net
1090--------------------------------
1091
1092The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
1093additional values you get for IP version 6 if you configure the kernel to
1094support this. Table 1-9 lists the files and their meaning.
1095
1096
1097Table 1-8: IPv6 info in /proc/net
1098..............................................................................
1099 File Content
1100 udp6 UDP sockets (IPv6)
1101 tcp6 TCP sockets (IPv6)
1102 raw6 Raw device statistics (IPv6)
1103 igmp6 IP multicast addresses, which this host joined (IPv6)
1104 if_inet6 List of IPv6 interface addresses
1105 ipv6_route Kernel routing table for IPv6
1106 rt6_stats Global IPv6 routing tables statistics
1107 sockstat6 Socket statistics (IPv6)
1108 snmp6 Snmp data (IPv6)
1109..............................................................................
1110
1111
1112Table 1-9: Network info in /proc/net
1113..............................................................................
1114 File Content
1115 arp Kernel ARP table
1116 dev network devices with statistics
1117 dev_mcast the Layer2 multicast groups a device is listening too
1118 (interface index, label, number of references, number of bound
1119 addresses).
1120 dev_stat network device status
1121 ip_fwchains Firewall chain linkage
1122 ip_fwnames Firewall chain names
1123 ip_masq Directory containing the masquerading tables
1124 ip_masquerade Major masquerading table
1125 netstat Network statistics
1126 raw raw device statistics
1127 route Kernel routing table
1128 rpc Directory containing rpc info
1129 rt_cache Routing cache
1130 snmp SNMP data
1131 sockstat Socket statistics
1132 tcp TCP sockets
1133 udp UDP sockets
1134 unix UNIX domain sockets
1135 wireless Wireless interface data (Wavelan etc)
1136 igmp IP multicast addresses, which this host joined
1137 psched Global packet scheduler parameters.
1138 netlink List of PF_NETLINK sockets
1139 ip_mr_vifs List of multicast virtual interfaces
1140 ip_mr_cache List of multicast routing cache
1141..............................................................................
1142
1143You can use this information to see which network devices are available in
1144your system and how much traffic was routed over those devices:
1145
1146 > cat /proc/net/dev
1147 Inter-|Receive |[...
1148 face |bytes packets errs drop fifo frame compressed multicast|[...
1149 lo: 908188 5596 0 0 0 0 0 0 [...
1150 ppp0:15475140 20721 410 0 0 410 0 0 [...
1151 eth0: 614530 7085 0 0 0 0 0 1 [...
1152
1153 ...] Transmit
1154 ...] bytes packets errs drop fifo colls carrier compressed
1155 ...] 908188 5596 0 0 0 0 0 0
1156 ...] 1375103 17405 0 0 0 0 0 0
1157 ...] 1703981 5535 0 0 0 3 0 0
1158
1159In addition, each Channel Bond interface has its own directory. For
1160example, the bond0 device will have a directory called /proc/net/bond0/.
1161It will contain information that is specific to that bond, such as the
1162current slaves of the bond, the link status of the slaves, and how
1163many times the slaves link has failed.
1164
11651.5 SCSI info
1166-------------
1167
1168If you have a SCSI host adapter in your system, you'll find a subdirectory
1169named after the driver for this adapter in /proc/scsi. You'll also see a list
1170of all recognized SCSI devices in /proc/scsi:
1171
1172 >cat /proc/scsi/scsi
1173 Attached devices:
1174 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1175 Vendor: IBM Model: DGHS09U Rev: 03E0
1176 Type: Direct-Access ANSI SCSI revision: 03
1177 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1178 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1179 Type: CD-ROM ANSI SCSI revision: 02
1180
1181
1182The directory named after the driver has one file for each adapter found in
1183the system. These files contain information about the controller, including
1184the used IRQ and the IO address range. The amount of information shown is
1185dependent on the adapter you use. The example shows the output for an Adaptec
1186AHA-2940 SCSI adapter:
1187
1188 > cat /proc/scsi/aic7xxx/0
1189
1190 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1191 Compile Options:
1192 TCQ Enabled By Default : Disabled
1193 AIC7XXX_PROC_STATS : Disabled
1194 AIC7XXX_RESET_DELAY : 5
1195 Adapter Configuration:
1196 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1197 Ultra Wide Controller
1198 PCI MMAPed I/O Base: 0xeb001000
1199 Adapter SEEPROM Config: SEEPROM found and used.
1200 Adaptec SCSI BIOS: Enabled
1201 IRQ: 10
1202 SCBs: Active 0, Max Active 2,
1203 Allocated 15, HW 16, Page 255
1204 Interrupts: 160328
1205 BIOS Control Word: 0x18b6
1206 Adapter Control Word: 0x005b
1207 Extended Translation: Enabled
1208 Disconnect Enable Flags: 0xffff
1209 Ultra Enable Flags: 0x0001
1210 Tag Queue Enable Flags: 0x0000
1211 Ordered Queue Tag Flags: 0x0000
1212 Default Tag Queue Depth: 8
1213 Tagged Queue By Device array for aic7xxx host instance 0:
1214 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1215 Actual queue depth per device for aic7xxx host instance 0:
1216 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1217 Statistics:
1218 (scsi0:0:0:0)
1219 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1220 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1221 Total transfers 160151 (74577 reads and 85574 writes)
1222 (scsi0:0:6:0)
1223 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1224 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1225 Total transfers 0 (0 reads and 0 writes)
1226
1227
12281.6 Parallel port info in /proc/parport
1229---------------------------------------
1230
1231The directory /proc/parport contains information about the parallel ports of
1232your system. It has one subdirectory for each port, named after the port
1233number (0,1,2,...).
1234
1235These directories contain the four files shown in Table 1-10.
1236
1237
1238Table 1-10: Files in /proc/parport
1239..............................................................................
1240 File Content
1241 autoprobe Any IEEE-1284 device ID information that has been acquired.
1242 devices list of the device drivers using that port. A + will appear by the
1243 name of the device currently using the port (it might not appear
1244 against any).
1245 hardware Parallel port's base address, IRQ line and DMA channel.
1246 irq IRQ that parport is using for that port. This is in a separate
1247 file to allow you to alter it by writing a new value in (IRQ
1248 number or none).
1249..............................................................................
1250
12511.7 TTY info in /proc/tty
1252-------------------------
1253
1254Information about the available and actually used tty's can be found in the
1255directory /proc/tty.You'll find entries for drivers and line disciplines in
1256this directory, as shown in Table 1-11.
1257
1258
1259Table 1-11: Files in /proc/tty
1260..............................................................................
1261 File Content
1262 drivers list of drivers and their usage
1263 ldiscs registered line disciplines
1264 driver/serial usage statistic and status of single tty lines
1265..............................................................................
1266
1267To see which tty's are currently in use, you can simply look into the file
1268/proc/tty/drivers:
1269
1270 > cat /proc/tty/drivers
1271 pty_slave /dev/pts 136 0-255 pty:slave
1272 pty_master /dev/ptm 128 0-255 pty:master
1273 pty_slave /dev/ttyp 3 0-255 pty:slave
1274 pty_master /dev/pty 2 0-255 pty:master
1275 serial /dev/cua 5 64-67 serial:callout
1276 serial /dev/ttyS 4 64-67 serial
1277 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1278 /dev/ptmx /dev/ptmx 5 2 system
1279 /dev/console /dev/console 5 1 system:console
1280 /dev/tty /dev/tty 5 0 system:/dev/tty
1281 unknown /dev/tty 4 1-63 console
1282
1283
12841.8 Miscellaneous kernel statistics in /proc/stat
1285-------------------------------------------------
1286
1287Various pieces of information about kernel activity are available in the
1288/proc/stat file. All of the numbers reported in this file are aggregates
1289since the system first booted. For a quick look, simply cat the file:
1290
1291 > cat /proc/stat
1292 cpu 2255 34 2290 22625563 6290 127 456 0 0 0
1293 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1294 cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1295 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1296 ctxt 1990473
1297 btime 1062191376
1298 processes 2915
1299 procs_running 1
1300 procs_blocked 0
1301 softirq 183433 0 21755 12 39 1137 231 21459 2263
1302
1303The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1304lines. These numbers identify the amount of time the CPU has spent performing
1305different kinds of work. Time units are in USER_HZ (typically hundredths of a
1306second). The meanings of the columns are as follows, from left to right:
1307
1308- user: normal processes executing in user mode
1309- nice: niced processes executing in user mode
1310- system: processes executing in kernel mode
1311- idle: twiddling thumbs
1312- iowait: waiting for I/O to complete
1313- irq: servicing interrupts
1314- softirq: servicing softirqs
1315- steal: involuntary wait
1316- guest: running a normal guest
1317- guest_nice: running a niced guest
1318
1319The "intr" line gives counts of interrupts serviced since boot time, for each
1320of the possible system interrupts. The first column is the total of all
1321interrupts serviced including unnumbered architecture specific interrupts;
1322each subsequent column is the total for that particular numbered interrupt.
1323Unnumbered interrupts are not shown, only summed into the total.
1324
1325The "ctxt" line gives the total number of context switches across all CPUs.
1326
1327The "btime" line gives the time at which the system booted, in seconds since
1328the Unix epoch.
1329
1330The "processes" line gives the number of processes and threads created, which
1331includes (but is not limited to) those created by calls to the fork() and
1332clone() system calls.
1333
1334The "procs_running" line gives the total number of threads that are
1335running or ready to run (i.e., the total number of runnable threads).
1336
1337The "procs_blocked" line gives the number of processes currently blocked,
1338waiting for I/O to complete.
1339
1340The "softirq" line gives counts of softirqs serviced since boot time, for each
1341of the possible system softirqs. The first column is the total of all
1342softirqs serviced; each subsequent column is the total for that particular
1343softirq.
1344
1345
13461.9 Ext4 file system parameters
1347-------------------------------
1348
1349Information about mounted ext4 file systems can be found in
1350/proc/fs/ext4. Each mounted filesystem will have a directory in
1351/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1352/proc/fs/ext4/dm-0). The files in each per-device directory are shown
1353in Table 1-12, below.
1354
1355Table 1-12: Files in /proc/fs/ext4/<devname>
1356..............................................................................
1357 File Content
1358 mb_groups details of multiblock allocator buddy cache of free blocks
1359..............................................................................
1360
13612.0 /proc/consoles
1362------------------
1363Shows registered system console lines.
1364
1365To see which character device lines are currently used for the system console
1366/dev/console, you may simply look into the file /proc/consoles:
1367
1368 > cat /proc/consoles
1369 tty0 -WU (ECp) 4:7
1370 ttyS0 -W- (Ep) 4:64
1371
1372The columns are:
1373
1374 device name of the device
1375 operations R = can do read operations
1376 W = can do write operations
1377 U = can do unblank
1378 flags E = it is enabled
1379 C = it is preferred console
1380 B = it is primary boot console
1381 p = it is used for printk buffer
1382 b = it is not a TTY but a Braille device
1383 a = it is safe to use when cpu is offline
1384 major:minor major and minor number of the device separated by a colon
1385
1386------------------------------------------------------------------------------
1387Summary
1388------------------------------------------------------------------------------
1389The /proc file system serves information about the running system. It not only
1390allows access to process data but also allows you to request the kernel status
1391by reading files in the hierarchy.
1392
1393The directory structure of /proc reflects the types of information and makes
1394it easy, if not obvious, where to look for specific data.
1395------------------------------------------------------------------------------
1396
1397------------------------------------------------------------------------------
1398CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1399------------------------------------------------------------------------------
1400
1401------------------------------------------------------------------------------
1402In This Chapter
1403------------------------------------------------------------------------------
1404* Modifying kernel parameters by writing into files found in /proc/sys
1405* Exploring the files which modify certain parameters
1406* Review of the /proc/sys file tree
1407------------------------------------------------------------------------------
1408
1409
1410A very interesting part of /proc is the directory /proc/sys. This is not only
1411a source of information, it also allows you to change parameters within the
1412kernel. Be very careful when attempting this. You can optimize your system,
1413but you can also cause it to crash. Never alter kernel parameters on a
1414production system. Set up a development machine and test to make sure that
1415everything works the way you want it to. You may have no alternative but to
1416reboot the machine once an error has been made.
1417
1418To change a value, simply echo the new value into the file. An example is
1419given below in the section on the file system data. You need to be root to do
1420this. You can create your own boot script to perform this every time your
1421system boots.
1422
1423The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1424general things in the operation of the Linux kernel. Since some of the files
1425can inadvertently disrupt your system, it is advisable to read both
1426documentation and source before actually making adjustments. In any case, be
1427very careful when writing to any of these files. The entries in /proc may
1428change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1429review the kernel documentation in the directory /usr/src/linux/Documentation.
1430This chapter is heavily based on the documentation included in the pre 2.2
1431kernels, and became part of it in version 2.2.1 of the Linux kernel.
1432
1433Please see: Documentation/sysctl/ directory for descriptions of these
1434entries.
1435
1436------------------------------------------------------------------------------
1437Summary
1438------------------------------------------------------------------------------
1439Certain aspects of kernel behavior can be modified at runtime, without the
1440need to recompile the kernel, or even to reboot the system. The files in the
1441/proc/sys tree can not only be read, but also modified. You can use the echo
1442command to write value into these files, thereby changing the default settings
1443of the kernel.
1444------------------------------------------------------------------------------
1445
1446------------------------------------------------------------------------------
1447CHAPTER 3: PER-PROCESS PARAMETERS
1448------------------------------------------------------------------------------
1449
14503.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1451--------------------------------------------------------------------------------
1452
1453These file can be used to adjust the badness heuristic used to select which
1454process gets killed in out of memory conditions.
1455
1456The badness heuristic assigns a value to each candidate task ranging from 0
1457(never kill) to 1000 (always kill) to determine which process is targeted. The
1458units are roughly a proportion along that range of allowed memory the process
1459may allocate from based on an estimation of its current memory and swap use.
1460For example, if a task is using all allowed memory, its badness score will be
14611000. If it is using half of its allowed memory, its score will be 500.
1462
1463There is an additional factor included in the badness score: the current memory
1464and swap usage is discounted by 3% for root processes.
1465
1466The amount of "allowed" memory depends on the context in which the oom killer
1467was called. If it is due to the memory assigned to the allocating task's cpuset
1468being exhausted, the allowed memory represents the set of mems assigned to that
1469cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1470memory represents the set of mempolicy nodes. If it is due to a memory
1471limit (or swap limit) being reached, the allowed memory is that configured
1472limit. Finally, if it is due to the entire system being out of memory, the
1473allowed memory represents all allocatable resources.
1474
1475The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1476is used to determine which task to kill. Acceptable values range from -1000
1477(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1478polarize the preference for oom killing either by always preferring a certain
1479task or completely disabling it. The lowest possible value, -1000, is
1480equivalent to disabling oom killing entirely for that task since it will always
1481report a badness score of 0.
1482
1483Consequently, it is very simple for userspace to define the amount of memory to
1484consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1485example, is roughly equivalent to allowing the remainder of tasks sharing the
1486same system, cpuset, mempolicy, or memory controller resources to use at least
148750% more memory. A value of -500, on the other hand, would be roughly
1488equivalent to discounting 50% of the task's allowed memory from being considered
1489as scoring against the task.
1490
1491For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1492be used to tune the badness score. Its acceptable values range from -16
1493(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1494(OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1495scaled linearly with /proc/<pid>/oom_score_adj.
1496
1497The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1498value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1499requires CAP_SYS_RESOURCE.
1500
1501Caveat: when a parent task is selected, the oom killer will sacrifice any first
1502generation children with separate address spaces instead, if possible. This
1503avoids servers and important system daemons from being killed and loses the
1504minimal amount of work.
1505
1506
15073.2 /proc/<pid>/oom_score - Display current oom-killer score
1508-------------------------------------------------------------
1509
1510This file can be used to check the current score used by the oom-killer is for
1511any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1512process should be killed in an out-of-memory situation.
1513
1514
15153.3 /proc/<pid>/io - Display the IO accounting fields
1516-------------------------------------------------------
1517
1518This file contains IO statistics for each running process
1519
1520Example
1521-------
1522
1523test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1524[1] 3828
1525
1526test:/tmp # cat /proc/3828/io
1527rchar: 323934931
1528wchar: 323929600
1529syscr: 632687
1530syscw: 632675
1531read_bytes: 0
1532write_bytes: 323932160
1533cancelled_write_bytes: 0
1534
1535
1536Description
1537-----------
1538
1539rchar
1540-----
1541
1542I/O counter: chars read
1543The number of bytes which this task has caused to be read from storage. This
1544is simply the sum of bytes which this process passed to read() and pread().
1545It includes things like tty IO and it is unaffected by whether or not actual
1546physical disk IO was required (the read might have been satisfied from
1547pagecache)
1548
1549
1550wchar
1551-----
1552
1553I/O counter: chars written
1554The number of bytes which this task has caused, or shall cause to be written
1555to disk. Similar caveats apply here as with rchar.
1556
1557
1558syscr
1559-----
1560
1561I/O counter: read syscalls
1562Attempt to count the number of read I/O operations, i.e. syscalls like read()
1563and pread().
1564
1565
1566syscw
1567-----
1568
1569I/O counter: write syscalls
1570Attempt to count the number of write I/O operations, i.e. syscalls like
1571write() and pwrite().
1572
1573
1574read_bytes
1575----------
1576
1577I/O counter: bytes read
1578Attempt to count the number of bytes which this process really did cause to
1579be fetched from the storage layer. Done at the submit_bio() level, so it is
1580accurate for block-backed filesystems. <please add status regarding NFS and
1581CIFS at a later time>
1582
1583
1584write_bytes
1585-----------
1586
1587I/O counter: bytes written
1588Attempt to count the number of bytes which this process caused to be sent to
1589the storage layer. This is done at page-dirtying time.
1590
1591
1592cancelled_write_bytes
1593---------------------
1594
1595The big inaccuracy here is truncate. If a process writes 1MB to a file and
1596then deletes the file, it will in fact perform no writeout. But it will have
1597been accounted as having caused 1MB of write.
1598In other words: The number of bytes which this process caused to not happen,
1599by truncating pagecache. A task can cause "negative" IO too. If this task
1600truncates some dirty pagecache, some IO which another task has been accounted
1601for (in its write_bytes) will not be happening. We _could_ just subtract that
1602from the truncating task's write_bytes, but there is information loss in doing
1603that.
1604
1605
1606Note
1607----
1608
1609At its current implementation state, this is a bit racy on 32-bit machines: if
1610process A reads process B's /proc/pid/io while process B is updating one of
1611those 64-bit counters, process A could see an intermediate result.
1612
1613
1614More information about this can be found within the taskstats documentation in
1615Documentation/accounting.
1616
16173.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1618---------------------------------------------------------------
1619When a process is dumped, all anonymous memory is written to a core file as
1620long as the size of the core file isn't limited. But sometimes we don't want
1621to dump some memory segments, for example, huge shared memory or DAX.
1622Conversely, sometimes we want to save file-backed memory segments into a core
1623file, not only the individual files.
1624
1625/proc/<pid>/coredump_filter allows you to customize which memory segments
1626will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1627of memory types. If a bit of the bitmask is set, memory segments of the
1628corresponding memory type are dumped, otherwise they are not dumped.
1629
1630The following 9 memory types are supported:
1631 - (bit 0) anonymous private memory
1632 - (bit 1) anonymous shared memory
1633 - (bit 2) file-backed private memory
1634 - (bit 3) file-backed shared memory
1635 - (bit 4) ELF header pages in file-backed private memory areas (it is
1636 effective only if the bit 2 is cleared)
1637 - (bit 5) hugetlb private memory
1638 - (bit 6) hugetlb shared memory
1639 - (bit 7) DAX private memory
1640 - (bit 8) DAX shared memory
1641
1642 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1643 are always dumped regardless of the bitmask status.
1644
1645 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
1646 only affected by bit 5-6, and DAX is only affected by bits 7-8.
1647
1648The default value of coredump_filter is 0x33; this means all anonymous memory
1649segments, ELF header pages and hugetlb private memory are dumped.
1650
1651If you don't want to dump all shared memory segments attached to pid 1234,
1652write 0x31 to the process's proc file.
1653
1654 $ echo 0x31 > /proc/1234/coredump_filter
1655
1656When a new process is created, the process inherits the bitmask status from its
1657parent. It is useful to set up coredump_filter before the program runs.
1658For example:
1659
1660 $ echo 0x7 > /proc/self/coredump_filter
1661 $ ./some_program
1662
16633.5 /proc/<pid>/mountinfo - Information about mounts
1664--------------------------------------------------------
1665
1666This file contains lines of the form:
1667
166836 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1669(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1670
1671(1) mount ID: unique identifier of the mount (may be reused after umount)
1672(2) parent ID: ID of parent (or of self for the top of the mount tree)
1673(3) major:minor: value of st_dev for files on filesystem
1674(4) root: root of the mount within the filesystem
1675(5) mount point: mount point relative to the process's root
1676(6) mount options: per mount options
1677(7) optional fields: zero or more fields of the form "tag[:value]"
1678(8) separator: marks the end of the optional fields
1679(9) filesystem type: name of filesystem of the form "type[.subtype]"
1680(10) mount source: filesystem specific information or "none"
1681(11) super options: per super block options
1682
1683Parsers should ignore all unrecognised optional fields. Currently the
1684possible optional fields are:
1685
1686shared:X mount is shared in peer group X
1687master:X mount is slave to peer group X
1688propagate_from:X mount is slave and receives propagation from peer group X (*)
1689unbindable mount is unbindable
1690
1691(*) X is the closest dominant peer group under the process's root. If
1692X is the immediate master of the mount, or if there's no dominant peer
1693group under the same root, then only the "master:X" field is present
1694and not the "propagate_from:X" field.
1695
1696For more information on mount propagation see:
1697
1698 Documentation/filesystems/sharedsubtree.txt
1699
1700
17013.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1702--------------------------------------------------------
1703These files provide a method to access a tasks comm value. It also allows for
1704a task to set its own or one of its thread siblings comm value. The comm value
1705is limited in size compared to the cmdline value, so writing anything longer
1706then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1707comm value.
1708
1709
17103.7 /proc/<pid>/task/<tid>/children - Information about task children
1711-------------------------------------------------------------------------
1712This file provides a fast way to retrieve first level children pids
1713of a task pointed by <pid>/<tid> pair. The format is a space separated
1714stream of pids.
1715
1716Note the "first level" here -- if a child has own children they will
1717not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1718to obtain the descendants.
1719
1720Since this interface is intended to be fast and cheap it doesn't
1721guarantee to provide precise results and some children might be
1722skipped, especially if they've exited right after we printed their
1723pids, so one need to either stop or freeze processes being inspected
1724if precise results are needed.
1725
1726
17273.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
1728---------------------------------------------------------------
1729This file provides information associated with an opened file. The regular
1730files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1731represents the current offset of the opened file in decimal form [see lseek(2)
1732for details], 'flags' denotes the octal O_xxx mask the file has been
1733created with [see open(2) for details] and 'mnt_id' represents mount ID of
1734the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1735for details].
1736
1737A typical output is
1738
1739 pos: 0
1740 flags: 0100002
1741 mnt_id: 19
1742
1743All locks associated with a file descriptor are shown in its fdinfo too.
1744
1745lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF
1746
1747The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1748pair provide additional information particular to the objects they represent.
1749
1750 Eventfd files
1751 ~~~~~~~~~~~~~
1752 pos: 0
1753 flags: 04002
1754 mnt_id: 9
1755 eventfd-count: 5a
1756
1757 where 'eventfd-count' is hex value of a counter.
1758
1759 Signalfd files
1760 ~~~~~~~~~~~~~~
1761 pos: 0
1762 flags: 04002
1763 mnt_id: 9
1764 sigmask: 0000000000000200
1765
1766 where 'sigmask' is hex value of the signal mask associated
1767 with a file.
1768
1769 Epoll files
1770 ~~~~~~~~~~~
1771 pos: 0
1772 flags: 02
1773 mnt_id: 9
1774 tfd: 5 events: 1d data: ffffffffffffffff
1775
1776 where 'tfd' is a target file descriptor number in decimal form,
1777 'events' is events mask being watched and the 'data' is data
1778 associated with a target [see epoll(7) for more details].
1779
1780 Fsnotify files
1781 ~~~~~~~~~~~~~~
1782 For inotify files the format is the following
1783
1784 pos: 0
1785 flags: 02000000
1786 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1787
1788 where 'wd' is a watch descriptor in decimal form, ie a target file
1789 descriptor number, 'ino' and 'sdev' are inode and device where the
1790 target file resides and the 'mask' is the mask of events, all in hex
1791 form [see inotify(7) for more details].
1792
1793 If the kernel was built with exportfs support, the path to the target
1794 file is encoded as a file handle. The file handle is provided by three
1795 fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1796 format.
1797
1798 If the kernel is built without exportfs support the file handle won't be
1799 printed out.
1800
1801 If there is no inotify mark attached yet the 'inotify' line will be omitted.
1802
1803 For fanotify files the format is
1804
1805 pos: 0
1806 flags: 02
1807 mnt_id: 9
1808 fanotify flags:10 event-flags:0
1809 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1810 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1811
1812 where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1813 call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1814 flags associated with mark which are tracked separately from events
1815 mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1816 mask and 'ignored_mask' is the mask of events which are to be ignored.
1817 All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1818 does provide information about flags and mask used in fanotify_mark
1819 call [see fsnotify manpage for details].
1820
1821 While the first three lines are mandatory and always printed, the rest is
1822 optional and may be omitted if no marks created yet.
1823
1824 Timerfd files
1825 ~~~~~~~~~~~~~
1826
1827 pos: 0
1828 flags: 02
1829 mnt_id: 9
1830 clockid: 0
1831 ticks: 0
1832 settime flags: 01
1833 it_value: (0, 49406829)
1834 it_interval: (1, 0)
1835
1836 where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
1837 that have occurred [see timerfd_create(2) for details]. 'settime flags' are
1838 flags in octal form been used to setup the timer [see timerfd_settime(2) for
1839 details]. 'it_value' is remaining time until the timer exiration.
1840 'it_interval' is the interval for the timer. Note the timer might be set up
1841 with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
1842 still exhibits timer's remaining time.
1843
18443.9 /proc/<pid>/map_files - Information about memory mapped files
1845---------------------------------------------------------------------
1846This directory contains symbolic links which represent memory mapped files
1847the process is maintaining. Example output:
1848
1849 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
1850 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
1851 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
1852 | ...
1853 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
1854 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
1855
1856The name of a link represents the virtual memory bounds of a mapping, i.e.
1857vm_area_struct::vm_start-vm_area_struct::vm_end.
1858
1859The main purpose of the map_files is to retrieve a set of memory mapped
1860files in a fast way instead of parsing /proc/<pid>/maps or
1861/proc/<pid>/smaps, both of which contain many more records. At the same
1862time one can open(2) mappings from the listings of two processes and
1863comparing their inode numbers to figure out which anonymous memory areas
1864are actually shared.
1865
18663.10 /proc/<pid>/timerslack_ns - Task timerslack value
1867---------------------------------------------------------
1868This file provides the value of the task's timerslack value in nanoseconds.
1869This value specifies a amount of time that normal timers may be deferred
1870in order to coalesce timers and avoid unnecessary wakeups.
1871
1872This allows a task's interactivity vs power consumption trade off to be
1873adjusted.
1874
1875Writing 0 to the file will set the tasks timerslack to the default value.
1876
1877Valid values are from 0 - ULLONG_MAX
1878
1879An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
1880permissions on the task specified to change its timerslack_ns value.
1881
1882
1883------------------------------------------------------------------------------
1884Configuring procfs
1885------------------------------------------------------------------------------
1886
18874.1 Mount options
1888---------------------
1889
1890The following mount options are supported:
1891
1892 hidepid= Set /proc/<pid>/ access mode.
1893 gid= Set the group authorized to learn processes information.
1894
1895hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1896(default).
1897
1898hidepid=1 means users may not access any /proc/<pid>/ directories but their
1899own. Sensitive files like cmdline, sched*, status are now protected against
1900other users. This makes it impossible to learn whether any user runs
1901specific program (given the program doesn't reveal itself by its behaviour).
1902As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1903poorly written programs passing sensitive information via program arguments are
1904now protected against local eavesdroppers.
1905
1906hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1907users. It doesn't mean that it hides a fact whether a process with a specific
1908pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1909but it hides process' uid and gid, which may be learned by stat()'ing
1910/proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering
1911information about running processes, whether some daemon runs with elevated
1912privileges, whether other user runs some sensitive program, whether other users
1913run any program at all, etc.
1914
1915gid= defines a group authorized to learn processes information otherwise
1916prohibited by hidepid=. If you use some daemon like identd which needs to learn
1917information 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 3.7 /proc/<pid>/task/<tid>/children - Information about task children
44 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
45
46 4 Configuring procfs
47 4.1 Mount options
48
49------------------------------------------------------------------------------
50Preface
51------------------------------------------------------------------------------
52
530.1 Introduction/Credits
54------------------------
55
56This documentation is part of a soon (or so we hope) to be released book on
57the SuSE Linux distribution. As there is no complete documentation for the
58/proc file system and we've used many freely available sources to write these
59chapters, it seems only fair to give the work back to the Linux community.
60This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
61afraid it's still far from complete, but we hope it will be useful. As far as
62we know, it is the first 'all-in-one' document about the /proc file system. It
63is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
64SPARC, AXP, etc., features, you probably won't find what you are looking for.
65It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
66additions and patches are welcome and will be added to this document if you
67mail them to Bodo.
68
69We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
70other people for help compiling this documentation. We'd also like to extend a
71special thank you to Andi Kleen for documentation, which we relied on heavily
72to create this document, as well as the additional information he provided.
73Thanks to everybody else who contributed source or docs to the Linux kernel
74and helped create a great piece of software... :)
75
76If you have any comments, corrections or additions, please don't hesitate to
77contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
78document.
79
80The latest version of this document is available online at
81http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
82
83If the above direction does not works for you, you could try the kernel
84mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
85comandante@zaralinux.com.
86
870.2 Legal Stuff
88---------------
89
90We don't guarantee the correctness of this document, and if you come to us
91complaining about how you screwed up your system because of incorrect
92documentation, we won't feel responsible...
93
94------------------------------------------------------------------------------
95CHAPTER 1: COLLECTING SYSTEM INFORMATION
96------------------------------------------------------------------------------
97
98------------------------------------------------------------------------------
99In This Chapter
100------------------------------------------------------------------------------
101* Investigating the properties of the pseudo file system /proc and its
102 ability to provide information on the running Linux system
103* Examining /proc's structure
104* Uncovering various information about the kernel and the processes running
105 on the system
106------------------------------------------------------------------------------
107
108
109The proc file system acts as an interface to internal data structures in the
110kernel. It can be used to obtain information about the system and to change
111certain kernel parameters at runtime (sysctl).
112
113First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
114show you how you can use /proc/sys to change settings.
115
1161.1 Process-Specific Subdirectories
117-----------------------------------
118
119The directory /proc contains (among other things) one subdirectory for each
120process running on the system, which is named after the process ID (PID).
121
122The link self points to the process reading the file system. Each process
123subdirectory has the entries listed in Table 1-1.
124
125
126Table 1-1: Process specific entries in /proc
127..............................................................................
128 File Content
129 clear_refs Clears page referenced bits shown in smaps output
130 cmdline Command line arguments
131 cpu Current and last cpu in which it was executed (2.4)(smp)
132 cwd Link to the current working directory
133 environ Values of environment variables
134 exe Link to the executable of this process
135 fd Directory, which contains all file descriptors
136 maps Memory maps to executables and library files (2.4)
137 mem Memory held by this process
138 root Link to the root directory of this process
139 stat Process status
140 statm Process memory status information
141 status Process status in human readable form
142 wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan
143 pagemap Page table
144 stack Report full stack trace, enable via CONFIG_STACKTRACE
145 smaps a extension based on maps, showing the memory consumption of
146 each mapping and flags associated with it
147..............................................................................
148
149For example, to get the status information of a process, all you have to do is
150read the file /proc/PID/status:
151
152 >cat /proc/self/status
153 Name: cat
154 State: R (running)
155 Tgid: 5452
156 Pid: 5452
157 PPid: 743
158 TracerPid: 0 (2.4)
159 Uid: 501 501 501 501
160 Gid: 100 100 100 100
161 FDSize: 256
162 Groups: 100 14 16
163 VmPeak: 5004 kB
164 VmSize: 5004 kB
165 VmLck: 0 kB
166 VmHWM: 476 kB
167 VmRSS: 476 kB
168 VmData: 156 kB
169 VmStk: 88 kB
170 VmExe: 68 kB
171 VmLib: 1412 kB
172 VmPTE: 20 kb
173 VmSwap: 0 kB
174 Threads: 1
175 SigQ: 0/28578
176 SigPnd: 0000000000000000
177 ShdPnd: 0000000000000000
178 SigBlk: 0000000000000000
179 SigIgn: 0000000000000000
180 SigCgt: 0000000000000000
181 CapInh: 00000000fffffeff
182 CapPrm: 0000000000000000
183 CapEff: 0000000000000000
184 CapBnd: ffffffffffffffff
185 Seccomp: 0
186 voluntary_ctxt_switches: 0
187 nonvoluntary_ctxt_switches: 1
188
189This shows you nearly the same information you would get if you viewed it with
190the ps command. In fact, ps uses the proc file system to obtain its
191information. But you get a more detailed view of the process by reading the
192file /proc/PID/status. It fields are described in table 1-2.
193
194The statm file contains more detailed information about the process
195memory usage. Its seven fields are explained in Table 1-3. The stat file
196contains details information about the process itself. Its fields are
197explained in Table 1-4.
198
199(for SMP CONFIG users)
200For making accounting scalable, RSS related information are handled in
201asynchronous manner and the vaule may not be very precise. To see a precise
202snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
203It's slow but very precise.
204
205Table 1-2: Contents of the status files (as of 2.6.30-rc7)
206..............................................................................
207 Field Content
208 Name filename of the executable
209 State state (R is running, S is sleeping, D is sleeping
210 in an uninterruptible wait, Z is zombie,
211 T is traced or stopped)
212 Tgid thread group ID
213 Pid process id
214 PPid process id of the parent process
215 TracerPid PID of process tracing this process (0 if not)
216 Uid Real, effective, saved set, and file system UIDs
217 Gid Real, effective, saved set, and file system GIDs
218 FDSize number of file descriptor slots currently allocated
219 Groups supplementary group list
220 VmPeak peak virtual memory size
221 VmSize total program size
222 VmLck locked memory size
223 VmHWM peak resident set size ("high water mark")
224 VmRSS size of memory portions
225 VmData size of data, stack, and text segments
226 VmStk size of data, stack, and text segments
227 VmExe size of text segment
228 VmLib size of shared library code
229 VmPTE size of page table entries
230 VmSwap size of swap usage (the number of referred swapents)
231 Threads number of threads
232 SigQ number of signals queued/max. number for queue
233 SigPnd bitmap of pending signals for the thread
234 ShdPnd bitmap of shared pending signals for the process
235 SigBlk bitmap of blocked signals
236 SigIgn bitmap of ignored signals
237 SigCgt bitmap of catched signals
238 CapInh bitmap of inheritable capabilities
239 CapPrm bitmap of permitted capabilities
240 CapEff bitmap of effective capabilities
241 CapBnd bitmap of capabilities bounding set
242 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
243 Cpus_allowed mask of CPUs on which this process may run
244 Cpus_allowed_list Same as previous, but in "list format"
245 Mems_allowed mask of memory nodes allowed to this process
246 Mems_allowed_list Same as previous, but in "list format"
247 voluntary_ctxt_switches number of voluntary context switches
248 nonvoluntary_ctxt_switches number of non voluntary context switches
249..............................................................................
250
251Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
252..............................................................................
253 Field Content
254 size total program size (pages) (same as VmSize in status)
255 resident size of memory portions (pages) (same as VmRSS in status)
256 shared number of pages that are shared (i.e. backed by a file)
257 trs number of pages that are 'code' (not including libs; broken,
258 includes data segment)
259 lrs number of pages of library (always 0 on 2.6)
260 drs number of pages of data/stack (including libs; broken,
261 includes library text)
262 dt number of dirty pages (always 0 on 2.6)
263..............................................................................
264
265
266Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
267..............................................................................
268 Field Content
269 pid process id
270 tcomm filename of the executable
271 state state (R is running, S is sleeping, D is sleeping in an
272 uninterruptible wait, Z is zombie, T is traced or stopped)
273 ppid process id of the parent process
274 pgrp pgrp of the process
275 sid session id
276 tty_nr tty the process uses
277 tty_pgrp pgrp of the tty
278 flags task flags
279 min_flt number of minor faults
280 cmin_flt number of minor faults with child's
281 maj_flt number of major faults
282 cmaj_flt number of major faults with child's
283 utime user mode jiffies
284 stime kernel mode jiffies
285 cutime user mode jiffies with child's
286 cstime kernel mode jiffies with child's
287 priority priority level
288 nice nice level
289 num_threads number of threads
290 it_real_value (obsolete, always 0)
291 start_time time the process started after system boot
292 vsize virtual memory size
293 rss resident set memory size
294 rsslim current limit in bytes on the rss
295 start_code address above which program text can run
296 end_code address below which program text can run
297 start_stack address of the start of the main process stack
298 esp current value of ESP
299 eip current value of EIP
300 pending bitmap of pending signals
301 blocked bitmap of blocked signals
302 sigign bitmap of ignored signals
303 sigcatch bitmap of catched signals
304 wchan address where process went to sleep
305 0 (place holder)
306 0 (place holder)
307 exit_signal signal to send to parent thread on exit
308 task_cpu which CPU the task is scheduled on
309 rt_priority realtime priority
310 policy scheduling policy (man sched_setscheduler)
311 blkio_ticks time spent waiting for block IO
312 gtime guest time of the task in jiffies
313 cgtime guest time of the task children in jiffies
314 start_data address above which program data+bss is placed
315 end_data address below which program data+bss is placed
316 start_brk address above which program heap can be expanded with brk()
317 arg_start address above which program command line is placed
318 arg_end address below which program command line is placed
319 env_start address above which program environment is placed
320 env_end address below which program environment is placed
321 exit_code the thread's exit_code in the form reported by the waitpid system call
322..............................................................................
323
324The /proc/PID/maps file containing the currently mapped memory regions and
325their access permissions.
326
327The format is:
328
329address perms offset dev inode pathname
330
33108048000-08049000 r-xp 00000000 03:00 8312 /opt/test
33208049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
3330804a000-0806b000 rw-p 00000000 00:00 0 [heap]
334a7cb1000-a7cb2000 ---p 00000000 00:00 0
335a7cb2000-a7eb2000 rw-p 00000000 00:00 0
336a7eb2000-a7eb3000 ---p 00000000 00:00 0
337a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack:1001]
338a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
339a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
340a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
341a800b000-a800e000 rw-p 00000000 00:00 0
342a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
343a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
344a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
345a8024000-a8027000 rw-p 00000000 00:00 0
346a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
347a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
348a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
349aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
350ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
351
352where "address" is the address space in the process that it occupies, "perms"
353is a set of permissions:
354
355 r = read
356 w = write
357 x = execute
358 s = shared
359 p = private (copy on write)
360
361"offset" is the offset into the mapping, "dev" is the device (major:minor), and
362"inode" is the inode on that device. 0 indicates that no inode is associated
363with the memory region, as the case would be with BSS (uninitialized data).
364The "pathname" shows the name associated file for this mapping. If the mapping
365is not associated with a file:
366
367 [heap] = the heap of the program
368 [stack] = the stack of the main process
369 [stack:1001] = the stack of the thread with tid 1001
370 [vdso] = the "virtual dynamic shared object",
371 the kernel system call handler
372
373 or if empty, the mapping is anonymous.
374
375The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint
376of the individual tasks of a process. In this file you will see a mapping marked
377as [stack] if that task sees it as a stack. This is a key difference from the
378content of /proc/PID/maps, where you will see all mappings that are being used
379as stack by all of those tasks. Hence, for the example above, the task-level
380map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this:
381
38208048000-08049000 r-xp 00000000 03:00 8312 /opt/test
38308049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
3840804a000-0806b000 rw-p 00000000 00:00 0 [heap]
385a7cb1000-a7cb2000 ---p 00000000 00:00 0
386a7cb2000-a7eb2000 rw-p 00000000 00:00 0
387a7eb2000-a7eb3000 ---p 00000000 00:00 0
388a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack]
389a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
390a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
391a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
392a800b000-a800e000 rw-p 00000000 00:00 0
393a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
394a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
395a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
396a8024000-a8027000 rw-p 00000000 00:00 0
397a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
398a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
399a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
400aff35000-aff4a000 rw-p 00000000 00:00 0
401ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
402
403The /proc/PID/smaps is an extension based on maps, showing the memory
404consumption for each of the process's mappings. For each of mappings there
405is a series of lines such as the following:
406
40708048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
408Size: 1084 kB
409Rss: 892 kB
410Pss: 374 kB
411Shared_Clean: 892 kB
412Shared_Dirty: 0 kB
413Private_Clean: 0 kB
414Private_Dirty: 0 kB
415Referenced: 892 kB
416Anonymous: 0 kB
417Swap: 0 kB
418KernelPageSize: 4 kB
419MMUPageSize: 4 kB
420Locked: 374 kB
421VmFlags: rd ex mr mw me de
422
423the first of these lines shows the same information as is displayed for the
424mapping in /proc/PID/maps. The remaining lines show the size of the mapping
425(size), the amount of the mapping that is currently resident in RAM (RSS), the
426process' proportional share of this mapping (PSS), the number of clean and
427dirty private pages in the mapping. Note that even a page which is part of a
428MAP_SHARED mapping, but has only a single pte mapped, i.e. is currently used
429by only one process, is accounted as private and not as shared. "Referenced"
430indicates the amount of memory currently marked as referenced or accessed.
431"Anonymous" shows the amount of memory that does not belong to any file. Even
432a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
433and a page is modified, the file page is replaced by a private anonymous copy.
434"Swap" shows how much would-be-anonymous memory is also used, but out on
435swap.
436
437"VmFlags" field deserves a separate description. This member represents the kernel
438flags associated with the particular virtual memory area in two letter encoded
439manner. The codes are the following:
440 rd - readable
441 wr - writeable
442 ex - executable
443 sh - shared
444 mr - may read
445 mw - may write
446 me - may execute
447 ms - may share
448 gd - stack segment growns down
449 pf - pure PFN range
450 dw - disabled write to the mapped file
451 lo - pages are locked in memory
452 io - memory mapped I/O area
453 sr - sequential read advise provided
454 rr - random read advise provided
455 dc - do not copy area on fork
456 de - do not expand area on remapping
457 ac - area is accountable
458 nr - swap space is not reserved for the area
459 ht - area uses huge tlb pages
460 nl - non-linear mapping
461 ar - architecture specific flag
462 dd - do not include area into core dump
463 sd - soft-dirty flag
464 mm - mixed map area
465 hg - huge page advise flag
466 nh - no-huge page advise flag
467 mg - mergable advise flag
468
469Note that there is no guarantee that every flag and associated mnemonic will
470be present in all further kernel releases. Things get changed, the flags may
471be vanished or the reverse -- new added.
472
473This file is only present if the CONFIG_MMU kernel configuration option is
474enabled.
475
476The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
477bits on both physical and virtual pages associated with a process, and the
478soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details).
479To clear the bits for all the pages associated with the process
480 > echo 1 > /proc/PID/clear_refs
481
482To clear the bits for the anonymous pages associated with the process
483 > echo 2 > /proc/PID/clear_refs
484
485To clear the bits for the file mapped pages associated with the process
486 > echo 3 > /proc/PID/clear_refs
487
488To clear the soft-dirty bit
489 > echo 4 > /proc/PID/clear_refs
490
491Any other value written to /proc/PID/clear_refs will have no effect.
492
493The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
494using /proc/kpageflags and number of times a page is mapped using
495/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
496
4971.2 Kernel data
498---------------
499
500Similar to the process entries, the kernel data files give information about
501the running kernel. The files used to obtain this information are contained in
502/proc and are listed in Table 1-5. Not all of these will be present in your
503system. It depends on the kernel configuration and the loaded modules, which
504files are there, and which are missing.
505
506Table 1-5: Kernel info in /proc
507..............................................................................
508 File Content
509 apm Advanced power management info
510 buddyinfo Kernel memory allocator information (see text) (2.5)
511 bus Directory containing bus specific information
512 cmdline Kernel command line
513 cpuinfo Info about the CPU
514 devices Available devices (block and character)
515 dma Used DMS channels
516 filesystems Supported filesystems
517 driver Various drivers grouped here, currently rtc (2.4)
518 execdomains Execdomains, related to security (2.4)
519 fb Frame Buffer devices (2.4)
520 fs File system parameters, currently nfs/exports (2.4)
521 ide Directory containing info about the IDE subsystem
522 interrupts Interrupt usage
523 iomem Memory map (2.4)
524 ioports I/O port usage
525 irq Masks for irq to cpu affinity (2.4)(smp?)
526 isapnp ISA PnP (Plug&Play) Info (2.4)
527 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
528 kmsg Kernel messages
529 ksyms Kernel symbol table
530 loadavg Load average of last 1, 5 & 15 minutes
531 locks Kernel locks
532 meminfo Memory info
533 misc Miscellaneous
534 modules List of loaded modules
535 mounts Mounted filesystems
536 net Networking info (see text)
537 pagetypeinfo Additional page allocator information (see text) (2.5)
538 partitions Table of partitions known to the system
539 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
540 decoupled by lspci (2.4)
541 rtc Real time clock
542 scsi SCSI info (see text)
543 slabinfo Slab pool info
544 softirqs softirq usage
545 stat Overall statistics
546 swaps Swap space utilization
547 sys See chapter 2
548 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
549 tty Info of tty drivers
550 uptime Wall clock since boot, combined idle time of all cpus
551 version Kernel version
552 video bttv info of video resources (2.4)
553 vmallocinfo Show vmalloced areas
554..............................................................................
555
556You can, for example, check which interrupts are currently in use and what
557they are used for by looking in the file /proc/interrupts:
558
559 > cat /proc/interrupts
560 CPU0
561 0: 8728810 XT-PIC timer
562 1: 895 XT-PIC keyboard
563 2: 0 XT-PIC cascade
564 3: 531695 XT-PIC aha152x
565 4: 2014133 XT-PIC serial
566 5: 44401 XT-PIC pcnet_cs
567 8: 2 XT-PIC rtc
568 11: 8 XT-PIC i82365
569 12: 182918 XT-PIC PS/2 Mouse
570 13: 1 XT-PIC fpu
571 14: 1232265 XT-PIC ide0
572 15: 7 XT-PIC ide1
573 NMI: 0
574
575In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
576output of a SMP machine):
577
578 > cat /proc/interrupts
579
580 CPU0 CPU1
581 0: 1243498 1214548 IO-APIC-edge timer
582 1: 8949 8958 IO-APIC-edge keyboard
583 2: 0 0 XT-PIC cascade
584 5: 11286 10161 IO-APIC-edge soundblaster
585 8: 1 0 IO-APIC-edge rtc
586 9: 27422 27407 IO-APIC-edge 3c503
587 12: 113645 113873 IO-APIC-edge PS/2 Mouse
588 13: 0 0 XT-PIC fpu
589 14: 22491 24012 IO-APIC-edge ide0
590 15: 2183 2415 IO-APIC-edge ide1
591 17: 30564 30414 IO-APIC-level eth0
592 18: 177 164 IO-APIC-level bttv
593 NMI: 2457961 2457959
594 LOC: 2457882 2457881
595 ERR: 2155
596
597NMI is incremented in this case because every timer interrupt generates a NMI
598(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
599
600LOC is the local interrupt counter of the internal APIC of every CPU.
601
602ERR is incremented in the case of errors in the IO-APIC bus (the bus that
603connects the CPUs in a SMP system. This means that an error has been detected,
604the IO-APIC automatically retry the transmission, so it should not be a big
605problem, but you should read the SMP-FAQ.
606
607In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
608/proc/interrupts to display every IRQ vector in use by the system, not
609just those considered 'most important'. The new vectors are:
610
611 THR -- interrupt raised when a machine check threshold counter
612 (typically counting ECC corrected errors of memory or cache) exceeds
613 a configurable threshold. Only available on some systems.
614
615 TRM -- a thermal event interrupt occurs when a temperature threshold
616 has been exceeded for the CPU. This interrupt may also be generated
617 when the temperature drops back to normal.
618
619 SPU -- a spurious interrupt is some interrupt that was raised then lowered
620 by some IO device before it could be fully processed by the APIC. Hence
621 the APIC sees the interrupt but does not know what device it came from.
622 For this case the APIC will generate the interrupt with a IRQ vector
623 of 0xff. This might also be generated by chipset bugs.
624
625 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
626 sent from one CPU to another per the needs of the OS. Typically,
627 their statistics are used by kernel developers and interested users to
628 determine the occurrence of interrupts of the given type.
629
630The above IRQ vectors are displayed only when relevant. For example,
631the threshold vector does not exist on x86_64 platforms. Others are
632suppressed when the system is a uniprocessor. As of this writing, only
633i386 and x86_64 platforms support the new IRQ vector displays.
634
635Of some interest is the introduction of the /proc/irq directory to 2.4.
636It could be used to set IRQ to CPU affinity, this means that you can "hook" an
637IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
638irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
639prof_cpu_mask.
640
641For example
642 > ls /proc/irq/
643 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
644 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
645 > ls /proc/irq/0/
646 smp_affinity
647
648smp_affinity is a bitmask, in which you can specify which CPUs can handle the
649IRQ, you can set it by doing:
650
651 > echo 1 > /proc/irq/10/smp_affinity
652
653This means that only the first CPU will handle the IRQ, but you can also echo
6545 which means that only the first and fourth CPU can handle the IRQ.
655
656The contents of each smp_affinity file is the same by default:
657
658 > cat /proc/irq/0/smp_affinity
659 ffffffff
660
661There is an alternate interface, smp_affinity_list which allows specifying
662a cpu range instead of a bitmask:
663
664 > cat /proc/irq/0/smp_affinity_list
665 1024-1031
666
667The default_smp_affinity mask applies to all non-active IRQs, which are the
668IRQs which have not yet been allocated/activated, and hence which lack a
669/proc/irq/[0-9]* directory.
670
671The node file on an SMP system shows the node to which the device using the IRQ
672reports itself as being attached. This hardware locality information does not
673include information about any possible driver locality preference.
674
675prof_cpu_mask specifies which CPUs are to be profiled by the system wide
676profiler. Default value is ffffffff (all cpus if there are only 32 of them).
677
678The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
679between all the CPUs which are allowed to handle it. As usual the kernel has
680more info than you and does a better job than you, so the defaults are the
681best choice for almost everyone. [Note this applies only to those IO-APIC's
682that support "Round Robin" interrupt distribution.]
683
684There are three more important subdirectories in /proc: net, scsi, and sys.
685The general rule is that the contents, or even the existence of these
686directories, depend on your kernel configuration. If SCSI is not enabled, the
687directory scsi may not exist. The same is true with the net, which is there
688only when networking support is present in the running kernel.
689
690The slabinfo file gives information about memory usage at the slab level.
691Linux uses slab pools for memory management above page level in version 2.2.
692Commonly used objects have their own slab pool (such as network buffers,
693directory cache, and so on).
694
695..............................................................................
696
697> cat /proc/buddyinfo
698
699Node 0, zone DMA 0 4 5 4 4 3 ...
700Node 0, zone Normal 1 0 0 1 101 8 ...
701Node 0, zone HighMem 2 0 0 1 1 0 ...
702
703External fragmentation is a problem under some workloads, and buddyinfo is a
704useful tool for helping diagnose these problems. Buddyinfo will give you a
705clue as to how big an area you can safely allocate, or why a previous
706allocation failed.
707
708Each column represents the number of pages of a certain order which are
709available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
710ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
711available in ZONE_NORMAL, etc...
712
713More information relevant to external fragmentation can be found in
714pagetypeinfo.
715
716> cat /proc/pagetypeinfo
717Page block order: 9
718Pages per block: 512
719
720Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
721Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
722Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
723Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
724Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
725Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
726Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
727Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
728Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
729Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
730Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
731
732Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
733Node 0, zone DMA 2 0 5 1 0
734Node 0, zone DMA32 41 6 967 2 0
735
736Fragmentation avoidance in the kernel works by grouping pages of different
737migrate types into the same contiguous regions of memory called page blocks.
738A page block is typically the size of the default hugepage size e.g. 2MB on
739X86-64. By keeping pages grouped based on their ability to move, the kernel
740can reclaim pages within a page block to satisfy a high-order allocation.
741
742The pagetypinfo begins with information on the size of a page block. It
743then gives the same type of information as buddyinfo except broken down
744by migrate-type and finishes with details on how many page blocks of each
745type exist.
746
747If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
748from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
749make an estimate of the likely number of huge pages that can be allocated
750at a given point in time. All the "Movable" blocks should be allocatable
751unless memory has been mlock()'d. Some of the Reclaimable blocks should
752also be allocatable although a lot of filesystem metadata may have to be
753reclaimed to achieve this.
754
755..............................................................................
756
757meminfo:
758
759Provides information about distribution and utilization of memory. This
760varies by architecture and compile options. The following is from a
76116GB PIII, which has highmem enabled. You may not have all of these fields.
762
763> cat /proc/meminfo
764
765The "Locked" indicates whether the mapping is locked in memory or not.
766
767
768MemTotal: 16344972 kB
769MemFree: 13634064 kB
770MemAvailable: 14836172 kB
771Buffers: 3656 kB
772Cached: 1195708 kB
773SwapCached: 0 kB
774Active: 891636 kB
775Inactive: 1077224 kB
776HighTotal: 15597528 kB
777HighFree: 13629632 kB
778LowTotal: 747444 kB
779LowFree: 4432 kB
780SwapTotal: 0 kB
781SwapFree: 0 kB
782Dirty: 968 kB
783Writeback: 0 kB
784AnonPages: 861800 kB
785Mapped: 280372 kB
786Slab: 284364 kB
787SReclaimable: 159856 kB
788SUnreclaim: 124508 kB
789PageTables: 24448 kB
790NFS_Unstable: 0 kB
791Bounce: 0 kB
792WritebackTmp: 0 kB
793CommitLimit: 7669796 kB
794Committed_AS: 100056 kB
795VmallocTotal: 112216 kB
796VmallocUsed: 428 kB
797VmallocChunk: 111088 kB
798AnonHugePages: 49152 kB
799
800 MemTotal: Total usable ram (i.e. physical ram minus a few reserved
801 bits and the kernel binary code)
802 MemFree: The sum of LowFree+HighFree
803MemAvailable: An estimate of how much memory is available for starting new
804 applications, without swapping. Calculated from MemFree,
805 SReclaimable, the size of the file LRU lists, and the low
806 watermarks in each zone.
807 The estimate takes into account that the system needs some
808 page cache to function well, and that not all reclaimable
809 slab will be reclaimable, due to items being in use. The
810 impact of those factors will vary from system to system.
811 Buffers: Relatively temporary storage for raw disk blocks
812 shouldn't get tremendously large (20MB or so)
813 Cached: in-memory cache for files read from the disk (the
814 pagecache). Doesn't include SwapCached
815 SwapCached: Memory that once was swapped out, is swapped back in but
816 still also is in the swapfile (if memory is needed it
817 doesn't need to be swapped out AGAIN because it is already
818 in the swapfile. This saves I/O)
819 Active: Memory that has been used more recently and usually not
820 reclaimed unless absolutely necessary.
821 Inactive: Memory which has been less recently used. It is more
822 eligible to be reclaimed for other purposes
823 HighTotal:
824 HighFree: Highmem is all memory above ~860MB of physical memory
825 Highmem areas are for use by userspace programs, or
826 for the pagecache. The kernel must use tricks to access
827 this memory, making it slower to access than lowmem.
828 LowTotal:
829 LowFree: Lowmem is memory which can be used for everything that
830 highmem can be used for, but it is also available for the
831 kernel's use for its own data structures. Among many
832 other things, it is where everything from the Slab is
833 allocated. Bad things happen when you're out of lowmem.
834 SwapTotal: total amount of swap space available
835 SwapFree: Memory which has been evicted from RAM, and is temporarily
836 on the disk
837 Dirty: Memory which is waiting to get written back to the disk
838 Writeback: Memory which is actively being written back to the disk
839 AnonPages: Non-file backed pages mapped into userspace page tables
840AnonHugePages: Non-file backed huge pages mapped into userspace page tables
841 Mapped: files which have been mmaped, such as libraries
842 Slab: in-kernel data structures cache
843SReclaimable: Part of Slab, that might be reclaimed, such as caches
844 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
845 PageTables: amount of memory dedicated to the lowest level of page
846 tables.
847NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
848 storage
849 Bounce: Memory used for block device "bounce buffers"
850WritebackTmp: Memory used by FUSE for temporary writeback buffers
851 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
852 this is the total amount of memory currently available to
853 be allocated on the system. This limit is only adhered to
854 if strict overcommit accounting is enabled (mode 2 in
855 'vm.overcommit_memory').
856 The CommitLimit is calculated with the following formula:
857 CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap
858 For example, on a system with 1G of physical RAM and 7G
859 of swap with a `vm.overcommit_ratio` of 30 it would
860 yield a CommitLimit of 7.3G.
861 For more details, see the memory overcommit documentation
862 in vm/overcommit-accounting.
863Committed_AS: The amount of memory presently allocated on the system.
864 The committed memory is a sum of all of the memory which
865 has been allocated by processes, even if it has not been
866 "used" by them as of yet. A process which malloc()'s 1G
867 of memory, but only touches 300M of it will show up as
868 using 1G. This 1G is memory which has been "committed" to
869 by the VM and can be used at any time by the allocating
870 application. With strict overcommit enabled on the system
871 (mode 2 in 'vm.overcommit_memory'),allocations which would
872 exceed the CommitLimit (detailed above) will not be permitted.
873 This is useful if one needs to guarantee that processes will
874 not fail due to lack of memory once that memory has been
875 successfully allocated.
876VmallocTotal: total size of vmalloc memory area
877 VmallocUsed: amount of vmalloc area which is used
878VmallocChunk: largest contiguous block of vmalloc area which is free
879
880..............................................................................
881
882vmallocinfo:
883
884Provides information about vmalloced/vmaped areas. One line per area,
885containing the virtual address range of the area, size in bytes,
886caller information of the creator, and optional information depending
887on the kind of area :
888
889 pages=nr number of pages
890 phys=addr if a physical address was specified
891 ioremap I/O mapping (ioremap() and friends)
892 vmalloc vmalloc() area
893 vmap vmap()ed pages
894 user VM_USERMAP area
895 vpages buffer for pages pointers was vmalloced (huge area)
896 N<node>=nr (Only on NUMA kernels)
897 Number of pages allocated on memory node <node>
898
899> cat /proc/vmallocinfo
9000xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
901 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
9020xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
903 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
9040xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
905 phys=7fee8000 ioremap
9060xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
907 phys=7fee7000 ioremap
9080xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
9090xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
910 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
9110xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
912 pages=2 vmalloc N1=2
9130xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
914 /0x130 [x_tables] pages=4 vmalloc N0=4
9150xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
916 pages=14 vmalloc N2=14
9170xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
918 pages=4 vmalloc N1=4
9190xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
920 pages=2 vmalloc N1=2
9210xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
922 pages=10 vmalloc N0=10
923
924..............................................................................
925
926softirqs:
927
928Provides counts of softirq handlers serviced since boot time, for each cpu.
929
930> cat /proc/softirqs
931 CPU0 CPU1 CPU2 CPU3
932 HI: 0 0 0 0
933 TIMER: 27166 27120 27097 27034
934 NET_TX: 0 0 0 17
935 NET_RX: 42 0 0 39
936 BLOCK: 0 0 107 1121
937 TASKLET: 0 0 0 290
938 SCHED: 27035 26983 26971 26746
939 HRTIMER: 0 0 0 0
940 RCU: 1678 1769 2178 2250
941
942
9431.3 IDE devices in /proc/ide
944----------------------------
945
946The subdirectory /proc/ide contains information about all IDE devices of which
947the kernel is aware. There is one subdirectory for each IDE controller, the
948file drivers and a link for each IDE device, pointing to the device directory
949in the controller specific subtree.
950
951The file drivers contains general information about the drivers used for the
952IDE devices:
953
954 > cat /proc/ide/drivers
955 ide-cdrom version 4.53
956 ide-disk version 1.08
957
958More detailed information can be found in the controller specific
959subdirectories. These are named ide0, ide1 and so on. Each of these
960directories contains the files shown in table 1-6.
961
962
963Table 1-6: IDE controller info in /proc/ide/ide?
964..............................................................................
965 File Content
966 channel IDE channel (0 or 1)
967 config Configuration (only for PCI/IDE bridge)
968 mate Mate name
969 model Type/Chipset of IDE controller
970..............................................................................
971
972Each device connected to a controller has a separate subdirectory in the
973controllers directory. The files listed in table 1-7 are contained in these
974directories.
975
976
977Table 1-7: IDE device information
978..............................................................................
979 File Content
980 cache The cache
981 capacity Capacity of the medium (in 512Byte blocks)
982 driver driver and version
983 geometry physical and logical geometry
984 identify device identify block
985 media media type
986 model device identifier
987 settings device setup
988 smart_thresholds IDE disk management thresholds
989 smart_values IDE disk management values
990..............................................................................
991
992The most interesting file is settings. This file contains a nice overview of
993the drive parameters:
994
995 # cat /proc/ide/ide0/hda/settings
996 name value min max mode
997 ---- ----- --- --- ----
998 bios_cyl 526 0 65535 rw
999 bios_head 255 0 255 rw
1000 bios_sect 63 0 63 rw
1001 breada_readahead 4 0 127 rw
1002 bswap 0 0 1 r
1003 file_readahead 72 0 2097151 rw
1004 io_32bit 0 0 3 rw
1005 keepsettings 0 0 1 rw
1006 max_kb_per_request 122 1 127 rw
1007 multcount 0 0 8 rw
1008 nice1 1 0 1 rw
1009 nowerr 0 0 1 rw
1010 pio_mode write-only 0 255 w
1011 slow 0 0 1 rw
1012 unmaskirq 0 0 1 rw
1013 using_dma 0 0 1 rw
1014
1015
10161.4 Networking info in /proc/net
1017--------------------------------
1018
1019The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
1020additional values you get for IP version 6 if you configure the kernel to
1021support this. Table 1-9 lists the files and their meaning.
1022
1023
1024Table 1-8: IPv6 info in /proc/net
1025..............................................................................
1026 File Content
1027 udp6 UDP sockets (IPv6)
1028 tcp6 TCP sockets (IPv6)
1029 raw6 Raw device statistics (IPv6)
1030 igmp6 IP multicast addresses, which this host joined (IPv6)
1031 if_inet6 List of IPv6 interface addresses
1032 ipv6_route Kernel routing table for IPv6
1033 rt6_stats Global IPv6 routing tables statistics
1034 sockstat6 Socket statistics (IPv6)
1035 snmp6 Snmp data (IPv6)
1036..............................................................................
1037
1038
1039Table 1-9: Network info in /proc/net
1040..............................................................................
1041 File Content
1042 arp Kernel ARP table
1043 dev network devices with statistics
1044 dev_mcast the Layer2 multicast groups a device is listening too
1045 (interface index, label, number of references, number of bound
1046 addresses).
1047 dev_stat network device status
1048 ip_fwchains Firewall chain linkage
1049 ip_fwnames Firewall chain names
1050 ip_masq Directory containing the masquerading tables
1051 ip_masquerade Major masquerading table
1052 netstat Network statistics
1053 raw raw device statistics
1054 route Kernel routing table
1055 rpc Directory containing rpc info
1056 rt_cache Routing cache
1057 snmp SNMP data
1058 sockstat Socket statistics
1059 tcp TCP sockets
1060 udp UDP sockets
1061 unix UNIX domain sockets
1062 wireless Wireless interface data (Wavelan etc)
1063 igmp IP multicast addresses, which this host joined
1064 psched Global packet scheduler parameters.
1065 netlink List of PF_NETLINK sockets
1066 ip_mr_vifs List of multicast virtual interfaces
1067 ip_mr_cache List of multicast routing cache
1068..............................................................................
1069
1070You can use this information to see which network devices are available in
1071your system and how much traffic was routed over those devices:
1072
1073 > cat /proc/net/dev
1074 Inter-|Receive |[...
1075 face |bytes packets errs drop fifo frame compressed multicast|[...
1076 lo: 908188 5596 0 0 0 0 0 0 [...
1077 ppp0:15475140 20721 410 0 0 410 0 0 [...
1078 eth0: 614530 7085 0 0 0 0 0 1 [...
1079
1080 ...] Transmit
1081 ...] bytes packets errs drop fifo colls carrier compressed
1082 ...] 908188 5596 0 0 0 0 0 0
1083 ...] 1375103 17405 0 0 0 0 0 0
1084 ...] 1703981 5535 0 0 0 3 0 0
1085
1086In addition, each Channel Bond interface has its own directory. For
1087example, the bond0 device will have a directory called /proc/net/bond0/.
1088It will contain information that is specific to that bond, such as the
1089current slaves of the bond, the link status of the slaves, and how
1090many times the slaves link has failed.
1091
10921.5 SCSI info
1093-------------
1094
1095If you have a SCSI host adapter in your system, you'll find a subdirectory
1096named after the driver for this adapter in /proc/scsi. You'll also see a list
1097of all recognized SCSI devices in /proc/scsi:
1098
1099 >cat /proc/scsi/scsi
1100 Attached devices:
1101 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1102 Vendor: IBM Model: DGHS09U Rev: 03E0
1103 Type: Direct-Access ANSI SCSI revision: 03
1104 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1105 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1106 Type: CD-ROM ANSI SCSI revision: 02
1107
1108
1109The directory named after the driver has one file for each adapter found in
1110the system. These files contain information about the controller, including
1111the used IRQ and the IO address range. The amount of information shown is
1112dependent on the adapter you use. The example shows the output for an Adaptec
1113AHA-2940 SCSI adapter:
1114
1115 > cat /proc/scsi/aic7xxx/0
1116
1117 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1118 Compile Options:
1119 TCQ Enabled By Default : Disabled
1120 AIC7XXX_PROC_STATS : Disabled
1121 AIC7XXX_RESET_DELAY : 5
1122 Adapter Configuration:
1123 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1124 Ultra Wide Controller
1125 PCI MMAPed I/O Base: 0xeb001000
1126 Adapter SEEPROM Config: SEEPROM found and used.
1127 Adaptec SCSI BIOS: Enabled
1128 IRQ: 10
1129 SCBs: Active 0, Max Active 2,
1130 Allocated 15, HW 16, Page 255
1131 Interrupts: 160328
1132 BIOS Control Word: 0x18b6
1133 Adapter Control Word: 0x005b
1134 Extended Translation: Enabled
1135 Disconnect Enable Flags: 0xffff
1136 Ultra Enable Flags: 0x0001
1137 Tag Queue Enable Flags: 0x0000
1138 Ordered Queue Tag Flags: 0x0000
1139 Default Tag Queue Depth: 8
1140 Tagged Queue By Device array for aic7xxx host instance 0:
1141 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1142 Actual queue depth per device for aic7xxx host instance 0:
1143 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1144 Statistics:
1145 (scsi0:0:0:0)
1146 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1147 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1148 Total transfers 160151 (74577 reads and 85574 writes)
1149 (scsi0:0:6:0)
1150 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1151 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1152 Total transfers 0 (0 reads and 0 writes)
1153
1154
11551.6 Parallel port info in /proc/parport
1156---------------------------------------
1157
1158The directory /proc/parport contains information about the parallel ports of
1159your system. It has one subdirectory for each port, named after the port
1160number (0,1,2,...).
1161
1162These directories contain the four files shown in Table 1-10.
1163
1164
1165Table 1-10: Files in /proc/parport
1166..............................................................................
1167 File Content
1168 autoprobe Any IEEE-1284 device ID information that has been acquired.
1169 devices list of the device drivers using that port. A + will appear by the
1170 name of the device currently using the port (it might not appear
1171 against any).
1172 hardware Parallel port's base address, IRQ line and DMA channel.
1173 irq IRQ that parport is using for that port. This is in a separate
1174 file to allow you to alter it by writing a new value in (IRQ
1175 number or none).
1176..............................................................................
1177
11781.7 TTY info in /proc/tty
1179-------------------------
1180
1181Information about the available and actually used tty's can be found in the
1182directory /proc/tty.You'll find entries for drivers and line disciplines in
1183this directory, as shown in Table 1-11.
1184
1185
1186Table 1-11: Files in /proc/tty
1187..............................................................................
1188 File Content
1189 drivers list of drivers and their usage
1190 ldiscs registered line disciplines
1191 driver/serial usage statistic and status of single tty lines
1192..............................................................................
1193
1194To see which tty's are currently in use, you can simply look into the file
1195/proc/tty/drivers:
1196
1197 > cat /proc/tty/drivers
1198 pty_slave /dev/pts 136 0-255 pty:slave
1199 pty_master /dev/ptm 128 0-255 pty:master
1200 pty_slave /dev/ttyp 3 0-255 pty:slave
1201 pty_master /dev/pty 2 0-255 pty:master
1202 serial /dev/cua 5 64-67 serial:callout
1203 serial /dev/ttyS 4 64-67 serial
1204 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1205 /dev/ptmx /dev/ptmx 5 2 system
1206 /dev/console /dev/console 5 1 system:console
1207 /dev/tty /dev/tty 5 0 system:/dev/tty
1208 unknown /dev/tty 4 1-63 console
1209
1210
12111.8 Miscellaneous kernel statistics in /proc/stat
1212-------------------------------------------------
1213
1214Various pieces of information about kernel activity are available in the
1215/proc/stat file. All of the numbers reported in this file are aggregates
1216since the system first booted. For a quick look, simply cat the file:
1217
1218 > cat /proc/stat
1219 cpu 2255 34 2290 22625563 6290 127 456 0 0
1220 cpu0 1132 34 1441 11311718 3675 127 438 0 0
1221 cpu1 1123 0 849 11313845 2614 0 18 0 0
1222 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1223 ctxt 1990473
1224 btime 1062191376
1225 processes 2915
1226 procs_running 1
1227 procs_blocked 0
1228 softirq 183433 0 21755 12 39 1137 231 21459 2263
1229
1230The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1231lines. These numbers identify the amount of time the CPU has spent performing
1232different kinds of work. Time units are in USER_HZ (typically hundredths of a
1233second). The meanings of the columns are as follows, from left to right:
1234
1235- user: normal processes executing in user mode
1236- nice: niced processes executing in user mode
1237- system: processes executing in kernel mode
1238- idle: twiddling thumbs
1239- iowait: waiting for I/O to complete
1240- irq: servicing interrupts
1241- softirq: servicing softirqs
1242- steal: involuntary wait
1243- guest: running a normal guest
1244- guest_nice: running a niced guest
1245
1246The "intr" line gives counts of interrupts serviced since boot time, for each
1247of the possible system interrupts. The first column is the total of all
1248interrupts serviced including unnumbered architecture specific interrupts;
1249each subsequent column is the total for that particular numbered interrupt.
1250Unnumbered interrupts are not shown, only summed into the total.
1251
1252The "ctxt" line gives the total number of context switches across all CPUs.
1253
1254The "btime" line gives the time at which the system booted, in seconds since
1255the Unix epoch.
1256
1257The "processes" line gives the number of processes and threads created, which
1258includes (but is not limited to) those created by calls to the fork() and
1259clone() system calls.
1260
1261The "procs_running" line gives the total number of threads that are
1262running or ready to run (i.e., the total number of runnable threads).
1263
1264The "procs_blocked" line gives the number of processes currently blocked,
1265waiting for I/O to complete.
1266
1267The "softirq" line gives counts of softirqs serviced since boot time, for each
1268of the possible system softirqs. The first column is the total of all
1269softirqs serviced; each subsequent column is the total for that particular
1270softirq.
1271
1272
12731.9 Ext4 file system parameters
1274------------------------------
1275
1276Information about mounted ext4 file systems can be found in
1277/proc/fs/ext4. Each mounted filesystem will have a directory in
1278/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1279/proc/fs/ext4/dm-0). The files in each per-device directory are shown
1280in Table 1-12, below.
1281
1282Table 1-12: Files in /proc/fs/ext4/<devname>
1283..............................................................................
1284 File Content
1285 mb_groups details of multiblock allocator buddy cache of free blocks
1286..............................................................................
1287
12882.0 /proc/consoles
1289------------------
1290Shows registered system console lines.
1291
1292To see which character device lines are currently used for the system console
1293/dev/console, you may simply look into the file /proc/consoles:
1294
1295 > cat /proc/consoles
1296 tty0 -WU (ECp) 4:7
1297 ttyS0 -W- (Ep) 4:64
1298
1299The columns are:
1300
1301 device name of the device
1302 operations R = can do read operations
1303 W = can do write operations
1304 U = can do unblank
1305 flags E = it is enabled
1306 C = it is preferred console
1307 B = it is primary boot console
1308 p = it is used for printk buffer
1309 b = it is not a TTY but a Braille device
1310 a = it is safe to use when cpu is offline
1311 major:minor major and minor number of the device separated by a colon
1312
1313------------------------------------------------------------------------------
1314Summary
1315------------------------------------------------------------------------------
1316The /proc file system serves information about the running system. It not only
1317allows access to process data but also allows you to request the kernel status
1318by reading files in the hierarchy.
1319
1320The directory structure of /proc reflects the types of information and makes
1321it easy, if not obvious, where to look for specific data.
1322------------------------------------------------------------------------------
1323
1324------------------------------------------------------------------------------
1325CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1326------------------------------------------------------------------------------
1327
1328------------------------------------------------------------------------------
1329In This Chapter
1330------------------------------------------------------------------------------
1331* Modifying kernel parameters by writing into files found in /proc/sys
1332* Exploring the files which modify certain parameters
1333* Review of the /proc/sys file tree
1334------------------------------------------------------------------------------
1335
1336
1337A very interesting part of /proc is the directory /proc/sys. This is not only
1338a source of information, it also allows you to change parameters within the
1339kernel. Be very careful when attempting this. You can optimize your system,
1340but you can also cause it to crash. Never alter kernel parameters on a
1341production system. Set up a development machine and test to make sure that
1342everything works the way you want it to. You may have no alternative but to
1343reboot the machine once an error has been made.
1344
1345To change a value, simply echo the new value into the file. An example is
1346given below in the section on the file system data. You need to be root to do
1347this. You can create your own boot script to perform this every time your
1348system boots.
1349
1350The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1351general things in the operation of the Linux kernel. Since some of the files
1352can inadvertently disrupt your system, it is advisable to read both
1353documentation and source before actually making adjustments. In any case, be
1354very careful when writing to any of these files. The entries in /proc may
1355change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1356review the kernel documentation in the directory /usr/src/linux/Documentation.
1357This chapter is heavily based on the documentation included in the pre 2.2
1358kernels, and became part of it in version 2.2.1 of the Linux kernel.
1359
1360Please see: Documentation/sysctl/ directory for descriptions of these
1361entries.
1362
1363------------------------------------------------------------------------------
1364Summary
1365------------------------------------------------------------------------------
1366Certain aspects of kernel behavior can be modified at runtime, without the
1367need to recompile the kernel, or even to reboot the system. The files in the
1368/proc/sys tree can not only be read, but also modified. You can use the echo
1369command to write value into these files, thereby changing the default settings
1370of the kernel.
1371------------------------------------------------------------------------------
1372
1373------------------------------------------------------------------------------
1374CHAPTER 3: PER-PROCESS PARAMETERS
1375------------------------------------------------------------------------------
1376
13773.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1378--------------------------------------------------------------------------------
1379
1380These file can be used to adjust the badness heuristic used to select which
1381process gets killed in out of memory conditions.
1382
1383The badness heuristic assigns a value to each candidate task ranging from 0
1384(never kill) to 1000 (always kill) to determine which process is targeted. The
1385units are roughly a proportion along that range of allowed memory the process
1386may allocate from based on an estimation of its current memory and swap use.
1387For example, if a task is using all allowed memory, its badness score will be
13881000. If it is using half of its allowed memory, its score will be 500.
1389
1390There is an additional factor included in the badness score: the current memory
1391and swap usage is discounted by 3% for root processes.
1392
1393The amount of "allowed" memory depends on the context in which the oom killer
1394was called. If it is due to the memory assigned to the allocating task's cpuset
1395being exhausted, the allowed memory represents the set of mems assigned to that
1396cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1397memory represents the set of mempolicy nodes. If it is due to a memory
1398limit (or swap limit) being reached, the allowed memory is that configured
1399limit. Finally, if it is due to the entire system being out of memory, the
1400allowed memory represents all allocatable resources.
1401
1402The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1403is used to determine which task to kill. Acceptable values range from -1000
1404(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1405polarize the preference for oom killing either by always preferring a certain
1406task or completely disabling it. The lowest possible value, -1000, is
1407equivalent to disabling oom killing entirely for that task since it will always
1408report a badness score of 0.
1409
1410Consequently, it is very simple for userspace to define the amount of memory to
1411consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1412example, is roughly equivalent to allowing the remainder of tasks sharing the
1413same system, cpuset, mempolicy, or memory controller resources to use at least
141450% more memory. A value of -500, on the other hand, would be roughly
1415equivalent to discounting 50% of the task's allowed memory from being considered
1416as scoring against the task.
1417
1418For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1419be used to tune the badness score. Its acceptable values range from -16
1420(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1421(OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1422scaled linearly with /proc/<pid>/oom_score_adj.
1423
1424The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1425value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1426requires CAP_SYS_RESOURCE.
1427
1428Caveat: when a parent task is selected, the oom killer will sacrifice any first
1429generation children with separate address spaces instead, if possible. This
1430avoids servers and important system daemons from being killed and loses the
1431minimal amount of work.
1432
1433
14343.2 /proc/<pid>/oom_score - Display current oom-killer score
1435-------------------------------------------------------------
1436
1437This file can be used to check the current score used by the oom-killer is for
1438any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1439process should be killed in an out-of-memory situation.
1440
1441
14423.3 /proc/<pid>/io - Display the IO accounting fields
1443-------------------------------------------------------
1444
1445This file contains IO statistics for each running process
1446
1447Example
1448-------
1449
1450test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1451[1] 3828
1452
1453test:/tmp # cat /proc/3828/io
1454rchar: 323934931
1455wchar: 323929600
1456syscr: 632687
1457syscw: 632675
1458read_bytes: 0
1459write_bytes: 323932160
1460cancelled_write_bytes: 0
1461
1462
1463Description
1464-----------
1465
1466rchar
1467-----
1468
1469I/O counter: chars read
1470The number of bytes which this task has caused to be read from storage. This
1471is simply the sum of bytes which this process passed to read() and pread().
1472It includes things like tty IO and it is unaffected by whether or not actual
1473physical disk IO was required (the read might have been satisfied from
1474pagecache)
1475
1476
1477wchar
1478-----
1479
1480I/O counter: chars written
1481The number of bytes which this task has caused, or shall cause to be written
1482to disk. Similar caveats apply here as with rchar.
1483
1484
1485syscr
1486-----
1487
1488I/O counter: read syscalls
1489Attempt to count the number of read I/O operations, i.e. syscalls like read()
1490and pread().
1491
1492
1493syscw
1494-----
1495
1496I/O counter: write syscalls
1497Attempt to count the number of write I/O operations, i.e. syscalls like
1498write() and pwrite().
1499
1500
1501read_bytes
1502----------
1503
1504I/O counter: bytes read
1505Attempt to count the number of bytes which this process really did cause to
1506be fetched from the storage layer. Done at the submit_bio() level, so it is
1507accurate for block-backed filesystems. <please add status regarding NFS and
1508CIFS at a later time>
1509
1510
1511write_bytes
1512-----------
1513
1514I/O counter: bytes written
1515Attempt to count the number of bytes which this process caused to be sent to
1516the storage layer. This is done at page-dirtying time.
1517
1518
1519cancelled_write_bytes
1520---------------------
1521
1522The big inaccuracy here is truncate. If a process writes 1MB to a file and
1523then deletes the file, it will in fact perform no writeout. But it will have
1524been accounted as having caused 1MB of write.
1525In other words: The number of bytes which this process caused to not happen,
1526by truncating pagecache. A task can cause "negative" IO too. If this task
1527truncates some dirty pagecache, some IO which another task has been accounted
1528for (in its write_bytes) will not be happening. We _could_ just subtract that
1529from the truncating task's write_bytes, but there is information loss in doing
1530that.
1531
1532
1533Note
1534----
1535
1536At its current implementation state, this is a bit racy on 32-bit machines: if
1537process A reads process B's /proc/pid/io while process B is updating one of
1538those 64-bit counters, process A could see an intermediate result.
1539
1540
1541More information about this can be found within the taskstats documentation in
1542Documentation/accounting.
1543
15443.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1545---------------------------------------------------------------
1546When a process is dumped, all anonymous memory is written to a core file as
1547long as the size of the core file isn't limited. But sometimes we don't want
1548to dump some memory segments, for example, huge shared memory. Conversely,
1549sometimes we want to save file-backed memory segments into a core file, not
1550only the individual files.
1551
1552/proc/<pid>/coredump_filter allows you to customize which memory segments
1553will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1554of memory types. If a bit of the bitmask is set, memory segments of the
1555corresponding memory type are dumped, otherwise they are not dumped.
1556
1557The following 7 memory types are supported:
1558 - (bit 0) anonymous private memory
1559 - (bit 1) anonymous shared memory
1560 - (bit 2) file-backed private memory
1561 - (bit 3) file-backed shared memory
1562 - (bit 4) ELF header pages in file-backed private memory areas (it is
1563 effective only if the bit 2 is cleared)
1564 - (bit 5) hugetlb private memory
1565 - (bit 6) hugetlb shared memory
1566
1567 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1568 are always dumped regardless of the bitmask status.
1569
1570 Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
1571 effected by bit 5-6.
1572
1573Default value of coredump_filter is 0x23; this means all anonymous memory
1574segments and hugetlb private memory are dumped.
1575
1576If you don't want to dump all shared memory segments attached to pid 1234,
1577write 0x21 to the process's proc file.
1578
1579 $ echo 0x21 > /proc/1234/coredump_filter
1580
1581When a new process is created, the process inherits the bitmask status from its
1582parent. It is useful to set up coredump_filter before the program runs.
1583For example:
1584
1585 $ echo 0x7 > /proc/self/coredump_filter
1586 $ ./some_program
1587
15883.5 /proc/<pid>/mountinfo - Information about mounts
1589--------------------------------------------------------
1590
1591This file contains lines of the form:
1592
159336 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1594(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1595
1596(1) mount ID: unique identifier of the mount (may be reused after umount)
1597(2) parent ID: ID of parent (or of self for the top of the mount tree)
1598(3) major:minor: value of st_dev for files on filesystem
1599(4) root: root of the mount within the filesystem
1600(5) mount point: mount point relative to the process's root
1601(6) mount options: per mount options
1602(7) optional fields: zero or more fields of the form "tag[:value]"
1603(8) separator: marks the end of the optional fields
1604(9) filesystem type: name of filesystem of the form "type[.subtype]"
1605(10) mount source: filesystem specific information or "none"
1606(11) super options: per super block options
1607
1608Parsers should ignore all unrecognised optional fields. Currently the
1609possible optional fields are:
1610
1611shared:X mount is shared in peer group X
1612master:X mount is slave to peer group X
1613propagate_from:X mount is slave and receives propagation from peer group X (*)
1614unbindable mount is unbindable
1615
1616(*) X is the closest dominant peer group under the process's root. If
1617X is the immediate master of the mount, or if there's no dominant peer
1618group under the same root, then only the "master:X" field is present
1619and not the "propagate_from:X" field.
1620
1621For more information on mount propagation see:
1622
1623 Documentation/filesystems/sharedsubtree.txt
1624
1625
16263.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1627--------------------------------------------------------
1628These files provide a method to access a tasks comm value. It also allows for
1629a task to set its own or one of its thread siblings comm value. The comm value
1630is limited in size compared to the cmdline value, so writing anything longer
1631then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1632comm value.
1633
1634
16353.7 /proc/<pid>/task/<tid>/children - Information about task children
1636-------------------------------------------------------------------------
1637This file provides a fast way to retrieve first level children pids
1638of a task pointed by <pid>/<tid> pair. The format is a space separated
1639stream of pids.
1640
1641Note the "first level" here -- if a child has own children they will
1642not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1643to obtain the descendants.
1644
1645Since this interface is intended to be fast and cheap it doesn't
1646guarantee to provide precise results and some children might be
1647skipped, especially if they've exited right after we printed their
1648pids, so one need to either stop or freeze processes being inspected
1649if precise results are needed.
1650
1651
16523.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
1653---------------------------------------------------------------
1654This file provides information associated with an opened file. The regular
1655files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1656represents the current offset of the opened file in decimal form [see lseek(2)
1657for details], 'flags' denotes the octal O_xxx mask the file has been
1658created with [see open(2) for details] and 'mnt_id' represents mount ID of
1659the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1660for details].
1661
1662A typical output is
1663
1664 pos: 0
1665 flags: 0100002
1666 mnt_id: 19
1667
1668The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1669pair provide additional information particular to the objects they represent.
1670
1671 Eventfd files
1672 ~~~~~~~~~~~~~
1673 pos: 0
1674 flags: 04002
1675 mnt_id: 9
1676 eventfd-count: 5a
1677
1678 where 'eventfd-count' is hex value of a counter.
1679
1680 Signalfd files
1681 ~~~~~~~~~~~~~~
1682 pos: 0
1683 flags: 04002
1684 mnt_id: 9
1685 sigmask: 0000000000000200
1686
1687 where 'sigmask' is hex value of the signal mask associated
1688 with a file.
1689
1690 Epoll files
1691 ~~~~~~~~~~~
1692 pos: 0
1693 flags: 02
1694 mnt_id: 9
1695 tfd: 5 events: 1d data: ffffffffffffffff
1696
1697 where 'tfd' is a target file descriptor number in decimal form,
1698 'events' is events mask being watched and the 'data' is data
1699 associated with a target [see epoll(7) for more details].
1700
1701 Fsnotify files
1702 ~~~~~~~~~~~~~~
1703 For inotify files the format is the following
1704
1705 pos: 0
1706 flags: 02000000
1707 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1708
1709 where 'wd' is a watch descriptor in decimal form, ie a target file
1710 descriptor number, 'ino' and 'sdev' are inode and device where the
1711 target file resides and the 'mask' is the mask of events, all in hex
1712 form [see inotify(7) for more details].
1713
1714 If the kernel was built with exportfs support, the path to the target
1715 file is encoded as a file handle. The file handle is provided by three
1716 fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1717 format.
1718
1719 If the kernel is built without exportfs support the file handle won't be
1720 printed out.
1721
1722 If there is no inotify mark attached yet the 'inotify' line will be omitted.
1723
1724 For fanotify files the format is
1725
1726 pos: 0
1727 flags: 02
1728 mnt_id: 9
1729 fanotify flags:10 event-flags:0
1730 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1731 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1732
1733 where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1734 call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1735 flags associated with mark which are tracked separately from events
1736 mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1737 mask and 'ignored_mask' is the mask of events which are to be ignored.
1738 All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1739 does provide information about flags and mask used in fanotify_mark
1740 call [see fsnotify manpage for details].
1741
1742 While the first three lines are mandatory and always printed, the rest is
1743 optional and may be omitted if no marks created yet.
1744
1745
1746------------------------------------------------------------------------------
1747Configuring procfs
1748------------------------------------------------------------------------------
1749
17504.1 Mount options
1751---------------------
1752
1753The following mount options are supported:
1754
1755 hidepid= Set /proc/<pid>/ access mode.
1756 gid= Set the group authorized to learn processes information.
1757
1758hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1759(default).
1760
1761hidepid=1 means users may not access any /proc/<pid>/ directories but their
1762own. Sensitive files like cmdline, sched*, status are now protected against
1763other users. This makes it impossible to learn whether any user runs
1764specific program (given the program doesn't reveal itself by its behaviour).
1765As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1766poorly written programs passing sensitive information via program arguments are
1767now protected against local eavesdroppers.
1768
1769hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1770users. It doesn't mean that it hides a fact whether a process with a specific
1771pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1772but it hides process' uid and gid, which may be learned by stat()'ing
1773/proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering
1774information about running processes, whether some daemon runs with elevated
1775privileges, whether other user runs some sensitive program, whether other users
1776run any program at all, etc.
1777
1778gid= defines a group authorized to learn processes information otherwise
1779prohibited by hidepid=. If you use some daemon like identd which needs to learn
1780information about processes information, just add identd to this group.