Version:  2.0.40 2.2.26 2.4.37 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9

Linux/Documentation/filesystems/proc.txt

  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 
  7 2.4.x update      Jorge Nerin <comandante@zaralinux.com>      November 14 2000
  8 move /proc/sys    Shen Feng <shen@cn.fujitsu.com>                 April 1 2009
  9 ------------------------------------------------------------------------------
 10 Version 1.3                                              Kernel version 2.2.12
 11                                               Kernel version 2.4.0-test11-pre4
 12 ------------------------------------------------------------------------------
 13 fixes/update part 1.1  Stefani Seibold <stefani@seibold.net>       June 9 2009
 14 
 15 Table 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 ------------------------------------------------------------------------------
 52 Preface
 53 ------------------------------------------------------------------------------
 54 
 55 0.1 Introduction/Credits
 56 ------------------------
 57 
 58 This documentation is  part of a soon (or  so we hope) to be  released book on
 59 the 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
 61 chapters, it  seems only fair  to give the work  back to the  Linux community.
 62 This work is  based on the 2.2.*  kernel version and the  upcoming 2.4.*. I'm
 63 afraid it's still far from complete, but we  hope it will be useful. As far as
 64 we know, it is the first 'all-in-one' document about the /proc file system. It
 65 is focused  on the Intel  x86 hardware,  so if you  are looking for  PPC, ARM,
 66 SPARC, AXP, etc., features, you probably  won't find what you are looking for.
 67 It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
 68 additions and patches  are welcome and will  be added to this  document if you
 69 mail them to Bodo.
 70 
 71 We'd like  to  thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
 72 other people for help compiling this documentation. We'd also like to extend a
 73 special thank  you to Andi Kleen for documentation, which we relied on heavily
 74 to create  this  document,  as well as the additional information he provided.
 75 Thanks to  everybody  else  who contributed source or docs to the Linux kernel
 76 and helped create a great piece of software... :)
 77 
 78 If you  have  any comments, corrections or additions, please don't hesitate to
 79 contact Bodo  Bauer  at  bb@ricochet.net.  We'll  be happy to add them to this
 80 document.
 81 
 82 The   latest   version    of   this   document   is    available   online   at
 83 http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
 84 
 85 If  the above  direction does  not works  for you,  you could  try the  kernel
 86 mailing  list  at  linux-kernel@vger.kernel.org  and/or try  to  reach  me  at
 87 comandante@zaralinux.com.
 88 
 89 0.2 Legal Stuff
 90 ---------------
 91 
 92 We don't  guarantee  the  correctness  of this document, and if you come to us
 93 complaining about  how  you  screwed  up  your  system  because  of  incorrect
 94 documentation, we won't feel responsible...
 95 
 96 ------------------------------------------------------------------------------
 97 CHAPTER 1: COLLECTING SYSTEM INFORMATION
 98 ------------------------------------------------------------------------------
 99 
100 ------------------------------------------------------------------------------
101 In 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 
111 The proc  file  system acts as an interface to internal data structures in the
112 kernel. It  can  be  used to obtain information about the system and to change
113 certain kernel parameters at runtime (sysctl).
114 
115 First, we'll  take  a  look  at the read-only parts of /proc. In Chapter 2, we
116 show you how you can use /proc/sys to change settings.
117 
118 1.1 Process-Specific Subdirectories
119 -----------------------------------
120 
121 The directory  /proc  contains  (among other things) one subdirectory for each
122 process running on the system, which is named after the process ID (PID).
123 
124 The link  self  points  to  the  process reading the file system. Each process
125 subdirectory has the entries listed in Table 1-1.
126 
127 
128 Table 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          an 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 
154 For example, to get the status information of a process, all you have to do is
155 read 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 
198 This shows you nearly the same information you would get if you viewed it with
199 the ps  command.  In  fact,  ps  uses  the  proc  file  system  to  obtain its
200 information.  But you get a more detailed  view of the  process by reading the
201 file /proc/PID/status. It fields are described in table 1-2.
202 
203 The  statm  file  contains  more  detailed  information about the process
204 memory usage. Its seven fields are explained in Table 1-3.  The stat file
205 contains details information about the process itself.  Its fields are
206 explained in Table 1-4.
207 
208 (for SMP CONFIG users)
209 For making accounting scalable, RSS related information are handled in an
210 asynchronous manner and the value may not be very precise. To see a precise
211 snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
212 It's slow but very precise.
213 
214 Table 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  Umask                       file mode creation mask
229  FDSize                      number of file descriptor slots currently allocated
230  Groups                      supplementary group list
231  NStgid                      descendant namespace thread group ID hierarchy
232  NSpid                       descendant namespace process ID hierarchy
233  NSpgid                      descendant namespace process group ID hierarchy
234  NSsid                       descendant namespace session ID hierarchy
235  VmPeak                      peak virtual memory size
236  VmSize                      total program size
237  VmLck                       locked memory size
238  VmHWM                       peak resident set size ("high water mark")
239  VmRSS                       size of memory portions. It contains the three
240                              following parts (VmRSS = RssAnon + RssFile + RssShmem)
241  RssAnon                     size of resident anonymous memory
242  RssFile                     size of resident file mappings
243  RssShmem                    size of resident shmem memory (includes SysV shm,
244                              mapping of tmpfs and shared anonymous mappings)
245  VmData                      size of private data segments
246  VmStk                       size of stack segments
247  VmExe                       size of text segment
248  VmLib                       size of shared library code
249  VmPTE                       size of page table entries
250  VmPMD                       size of second level page tables
251  VmSwap                      amount of swap used by anonymous private data
252                              (shmem swap usage is not included)
253  HugetlbPages                size of hugetlb memory portions
254  Threads                     number of threads
255  SigQ                        number of signals queued/max. number for queue
256  SigPnd                      bitmap of pending signals for the thread
257  ShdPnd                      bitmap of shared pending signals for the process
258  SigBlk                      bitmap of blocked signals
259  SigIgn                      bitmap of ignored signals
260  SigCgt                      bitmap of caught signals
261  CapInh                      bitmap of inheritable capabilities
262  CapPrm                      bitmap of permitted capabilities
263  CapEff                      bitmap of effective capabilities
264  CapBnd                      bitmap of capabilities bounding set
265  Seccomp                     seccomp mode, like prctl(PR_GET_SECCOMP, ...)
266  Cpus_allowed                mask of CPUs on which this process may run
267  Cpus_allowed_list           Same as previous, but in "list format"
268  Mems_allowed                mask of memory nodes allowed to this process
269  Mems_allowed_list           Same as previous, but in "list format"
270  voluntary_ctxt_switches     number of voluntary context switches
271  nonvoluntary_ctxt_switches  number of non voluntary context switches
272 ..............................................................................
273 
274 Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
275 ..............................................................................
276  Field    Content
277  size     total program size (pages)            (same as VmSize in status)
278  resident size of memory portions (pages)       (same as VmRSS in status)
279  shared   number of pages that are shared       (i.e. backed by a file, same
280                                                 as RssFile+RssShmem in status)
281  trs      number of pages that are 'code'       (not including libs; broken,
282                                                         includes data segment)
283  lrs      number of pages of library            (always 0 on 2.6)
284  drs      number of pages of data/stack         (including libs; broken,
285                                                         includes library text)
286  dt       number of dirty pages                 (always 0 on 2.6)
287 ..............................................................................
288 
289 
290 Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
291 ..............................................................................
292  Field          Content
293   pid           process id
294   tcomm         filename of the executable
295   state         state (R is running, S is sleeping, D is sleeping in an
296                 uninterruptible wait, Z is zombie, T is traced or stopped)
297   ppid          process id of the parent process
298   pgrp          pgrp of the process
299   sid           session id
300   tty_nr        tty the process uses
301   tty_pgrp      pgrp of the tty
302   flags         task flags
303   min_flt       number of minor faults
304   cmin_flt      number of minor faults with child's
305   maj_flt       number of major faults
306   cmaj_flt      number of major faults with child's
307   utime         user mode jiffies
308   stime         kernel mode jiffies
309   cutime        user mode jiffies with child's
310   cstime        kernel mode jiffies with child's
311   priority      priority level
312   nice          nice level
313   num_threads   number of threads
314   it_real_value (obsolete, always 0)
315   start_time    time the process started after system boot
316   vsize         virtual memory size
317   rss           resident set memory size
318   rsslim        current limit in bytes on the rss
319   start_code    address above which program text can run
320   end_code      address below which program text can run
321   start_stack   address of the start of the main process stack
322   esp           current value of ESP
323   eip           current value of EIP
324   pending       bitmap of pending signals
325   blocked       bitmap of blocked signals
326   sigign        bitmap of ignored signals
327   sigcatch      bitmap of caught signals
328   0             (place holder, used to be the wchan address, use /proc/PID/wchan instead)
329   0             (place holder)
330   0             (place holder)
331   exit_signal   signal to send to parent thread on exit
332   task_cpu      which CPU the task is scheduled on
333   rt_priority   realtime priority
334   policy        scheduling policy (man sched_setscheduler)
335   blkio_ticks   time spent waiting for block IO
336   gtime         guest time of the task in jiffies
337   cgtime        guest time of the task children in jiffies
338   start_data    address above which program data+bss is placed
339   end_data      address below which program data+bss is placed
340   start_brk     address above which program heap can be expanded with brk()
341   arg_start     address above which program command line is placed
342   arg_end       address below which program command line is placed
343   env_start     address above which program environment is placed
344   env_end       address below which program environment is placed
345   exit_code     the thread's exit_code in the form reported by the waitpid system call
346 ..............................................................................
347 
348 The /proc/PID/maps file containing the currently mapped memory regions and
349 their access permissions.
350 
351 The format is:
352 
353 address           perms offset  dev   inode      pathname
354 
355 08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
356 08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
357 0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
358 a7cb1000-a7cb2000 ---p 00000000 00:00 0
359 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
360 a7eb2000-a7eb3000 ---p 00000000 00:00 0
361 a7eb3000-a7ed5000 rw-p 00000000 00:00 0
362 a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
363 a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
364 a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
365 a800b000-a800e000 rw-p 00000000 00:00 0
366 a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
367 a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
368 a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
369 a8024000-a8027000 rw-p 00000000 00:00 0
370 a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
371 a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
372 a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
373 aff35000-aff4a000 rw-p 00000000 00:00 0          [stack]
374 ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
375 
376 where "address" is the address space in the process that it occupies, "perms"
377 is a set of permissions:
378 
379  r = read
380  w = write
381  x = execute
382  s = shared
383  p = private (copy on write)
384 
385 "offset" is the offset into the mapping, "dev" is the device (major:minor), and
386 "inode" is the inode  on that device.  0 indicates that  no inode is associated
387 with the memory region, as the case would be with BSS (uninitialized data).
388 The "pathname" shows the name associated file for this mapping.  If the mapping
389 is not associated with a file:
390 
391  [heap]                   = the heap of the program
392  [stack]                  = the stack of the main process
393  [vdso]                   = the "virtual dynamic shared object",
394                             the kernel system call handler
395 
396  or if empty, the mapping is anonymous.
397 
398 The /proc/PID/smaps is an extension based on maps, showing the memory
399 consumption for each of the process's mappings. For each of mappings there
400 is a series of lines such as the following:
401 
402 08048000-080bc000 r-xp 00000000 03:02 13130      /bin/bash
403 Size:               1084 kB
404 Rss:                 892 kB
405 Pss:                 374 kB
406 Shared_Clean:        892 kB
407 Shared_Dirty:          0 kB
408 Private_Clean:         0 kB
409 Private_Dirty:         0 kB
410 Referenced:          892 kB
411 Anonymous:             0 kB
412 AnonHugePages:         0 kB
413 ShmemPmdMapped:        0 kB
414 Shared_Hugetlb:        0 kB
415 Private_Hugetlb:       0 kB
416 Swap:                  0 kB
417 SwapPss:               0 kB
418 KernelPageSize:        4 kB
419 MMUPageSize:           4 kB
420 Locked:                0 kB
421 VmFlags: rd ex mr mw me dw
422 
423 the first of these lines shows the same information as is displayed for the
424 mapping 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
426 process' proportional share of this mapping (PSS), the number of clean and
427 dirty private pages in the mapping.
428 
429 The "proportional set size" (PSS) of a process is the count of pages it has
430 in memory, where each page is divided by the number of processes sharing it.
431 So if a process has 1000 pages all to itself, and 1000 shared with one other
432 process, its PSS will be 1500.
433 Note that even a page which is part of a MAP_SHARED mapping, but has only
434 a single pte mapped, i.e.  is currently used by only one process, is accounted
435 as private and not as shared.
436 "Referenced" indicates the amount of memory currently marked as referenced or
437 accessed.
438 "Anonymous" shows the amount of memory that does not belong to any file.  Even
439 a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
440 and a page is modified, the file page is replaced by a private anonymous copy.
441 "AnonHugePages" shows the ammount of memory backed by transparent hugepage.
442 "ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by
443 huge pages.
444 "Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
445 hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
446 reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
447 "Swap" shows how much would-be-anonymous memory is also used, but out on swap.
448 For shmem mappings, "Swap" includes also the size of the mapped (and not
449 replaced by copy-on-write) part of the underlying shmem object out on swap.
450 "SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
451 does not take into account swapped out page of underlying shmem objects.
452 "Locked" indicates whether the mapping is locked in memory or not.
453 
454 "VmFlags" field deserves a separate description. This member represents the kernel
455 flags associated with the particular virtual memory area in two letter encoded
456 manner. The codes are the following:
457     rd  - readable
458     wr  - writeable
459     ex  - executable
460     sh  - shared
461     mr  - may read
462     mw  - may write
463     me  - may execute
464     ms  - may share
465     gd  - stack segment growns down
466     pf  - pure PFN range
467     dw  - disabled write to the mapped file
468     lo  - pages are locked in memory
469     io  - memory mapped I/O area
470     sr  - sequential read advise provided
471     rr  - random read advise provided
472     dc  - do not copy area on fork
473     de  - do not expand area on remapping
474     ac  - area is accountable
475     nr  - swap space is not reserved for the area
476     ht  - area uses huge tlb pages
477     ar  - architecture specific flag
478     dd  - do not include area into core dump
479     sd  - soft-dirty flag
480     mm  - mixed map area
481     hg  - huge page advise flag
482     nh  - no-huge page advise flag
483     mg  - mergable advise flag
484 
485 Note that there is no guarantee that every flag and associated mnemonic will
486 be present in all further kernel releases. Things get changed, the flags may
487 be vanished or the reverse -- new added.
488 
489 This file is only present if the CONFIG_MMU kernel configuration option is
490 enabled.
491 
492 Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent
493 output can be achieved only in the single read call).
494 This typically manifests when doing partial reads of these files while the
495 memory map is being modified.  Despite the races, we do provide the following
496 guarantees:
497 
498 1) The mapped addresses never go backwards, which implies no two
499    regions will ever overlap.
500 2) If there is something at a given vaddr during the entirety of the
501    life of the smaps/maps walk, there will be some output for it.
502 
503 
504 The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
505 bits on both physical and virtual pages associated with a process, and the
506 soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details).
507 To clear the bits for all the pages associated with the process
508     > echo 1 > /proc/PID/clear_refs
509 
510 To clear the bits for the anonymous pages associated with the process
511     > echo 2 > /proc/PID/clear_refs
512 
513 To clear the bits for the file mapped pages associated with the process
514     > echo 3 > /proc/PID/clear_refs
515 
516 To clear the soft-dirty bit
517     > echo 4 > /proc/PID/clear_refs
518 
519 To reset the peak resident set size ("high water mark") to the process's
520 current value:
521     > echo 5 > /proc/PID/clear_refs
522 
523 Any other value written to /proc/PID/clear_refs will have no effect.
524 
525 The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
526 using /proc/kpageflags and number of times a page is mapped using
527 /proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
528 
529 The /proc/pid/numa_maps is an extension based on maps, showing the memory
530 locality and binding policy, as well as the memory usage (in pages) of
531 each mapping. The output follows a general format where mapping details get
532 summarized separated by blank spaces, one mapping per each file line:
533 
534 address   policy    mapping details
535 
536 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
537 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
538 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
539 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
540 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
541 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
542 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
543 320698b000 default file=/lib64/libc-2.12.so
544 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
545 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
546 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
547 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
548 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
549 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
550 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
551 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
552 
553 Where:
554 "address" is the starting address for the mapping;
555 "policy" reports the NUMA memory policy set for the mapping (see vm/numa_memory_policy.txt);
556 "mapping details" summarizes mapping data such as mapping type, page usage counters,
557 node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
558 size, in KB, that is backing the mapping up.
559 
560 1.2 Kernel data
561 ---------------
562 
563 Similar to  the  process entries, the kernel data files give information about
564 the running kernel. The files used to obtain this information are contained in
565 /proc and  are  listed  in Table 1-5. Not all of these will be present in your
566 system. It  depends  on the kernel configuration and the loaded modules, which
567 files are there, and which are missing.
568 
569 Table 1-5: Kernel info in /proc
570 ..............................................................................
571  File        Content                                           
572  apm         Advanced power management info                    
573  buddyinfo   Kernel memory allocator information (see text)     (2.5)
574  bus         Directory containing bus specific information     
575  cmdline     Kernel command line                               
576  cpuinfo     Info about the CPU                                
577  devices     Available devices (block and character)           
578  dma         Used DMS channels                                 
579  filesystems Supported filesystems                             
580  driver      Various drivers grouped here, currently rtc (2.4)
581  execdomains Execdomains, related to security                   (2.4)
582  fb          Frame Buffer devices                               (2.4)
583  fs          File system parameters, currently nfs/exports      (2.4)
584  ide         Directory containing info about the IDE subsystem 
585  interrupts  Interrupt usage                                   
586  iomem       Memory map                                         (2.4)
587  ioports     I/O port usage                                    
588  irq         Masks for irq to cpu affinity                      (2.4)(smp?)
589  isapnp      ISA PnP (Plug&Play) Info                           (2.4)
590  kcore       Kernel core image (can be ELF or A.OUT(deprecated in 2.4))   
591  kmsg        Kernel messages                                   
592  ksyms       Kernel symbol table                               
593  loadavg     Load average of last 1, 5 & 15 minutes                
594  locks       Kernel locks                                      
595  meminfo     Memory info                                       
596  misc        Miscellaneous                                     
597  modules     List of loaded modules                            
598  mounts      Mounted filesystems                               
599  net         Networking info (see text)                        
600  pagetypeinfo Additional page allocator information (see text)  (2.5)
601  partitions  Table of partitions known to the system           
602  pci         Deprecated info of PCI bus (new way -> /proc/bus/pci/,
603              decoupled by lspci                                 (2.4)
604  rtc         Real time clock                                   
605  scsi        SCSI info (see text)                              
606  slabinfo    Slab pool info                                    
607  softirqs    softirq usage
608  stat        Overall statistics                                
609  swaps       Swap space utilization                            
610  sys         See chapter 2                                     
611  sysvipc     Info of SysVIPC Resources (msg, sem, shm)          (2.4)
612  tty         Info of tty drivers
613  uptime      Wall clock since boot, combined idle time of all cpus
614  version     Kernel version                                    
615  video       bttv info of video resources                       (2.4)
616  vmallocinfo Show vmalloced areas
617 ..............................................................................
618 
619 You can,  for  example,  check  which interrupts are currently in use and what
620 they are used for by looking in the file /proc/interrupts:
621 
622   > cat /proc/interrupts 
623              CPU0        
624     0:    8728810          XT-PIC  timer 
625     1:        895          XT-PIC  keyboard 
626     2:          0          XT-PIC  cascade 
627     3:     531695          XT-PIC  aha152x 
628     4:    2014133          XT-PIC  serial 
629     5:      44401          XT-PIC  pcnet_cs 
630     8:          2          XT-PIC  rtc 
631    11:          8          XT-PIC  i82365 
632    12:     182918          XT-PIC  PS/2 Mouse 
633    13:          1          XT-PIC  fpu 
634    14:    1232265          XT-PIC  ide0 
635    15:          7          XT-PIC  ide1 
636   NMI:          0 
637 
638 In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
639 output of a SMP machine):
640 
641   > cat /proc/interrupts 
642 
643              CPU0       CPU1       
644     0:    1243498    1214548    IO-APIC-edge  timer
645     1:       8949       8958    IO-APIC-edge  keyboard
646     2:          0          0          XT-PIC  cascade
647     5:      11286      10161    IO-APIC-edge  soundblaster
648     8:          1          0    IO-APIC-edge  rtc
649     9:      27422      27407    IO-APIC-edge  3c503
650    12:     113645     113873    IO-APIC-edge  PS/2 Mouse
651    13:          0          0          XT-PIC  fpu
652    14:      22491      24012    IO-APIC-edge  ide0
653    15:       2183       2415    IO-APIC-edge  ide1
654    17:      30564      30414   IO-APIC-level  eth0
655    18:        177        164   IO-APIC-level  bttv
656   NMI:    2457961    2457959 
657   LOC:    2457882    2457881 
658   ERR:       2155
659 
660 NMI is incremented in this case because every timer interrupt generates a NMI
661 (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
662 
663 LOC is the local interrupt counter of the internal APIC of every CPU.
664 
665 ERR is incremented in the case of errors in the IO-APIC bus (the bus that
666 connects the CPUs in a SMP system. This means that an error has been detected,
667 the IO-APIC automatically retry the transmission, so it should not be a big
668 problem, but you should read the SMP-FAQ.
669 
670 In 2.6.2* /proc/interrupts was expanded again.  This time the goal was for
671 /proc/interrupts to display every IRQ vector in use by the system, not
672 just those considered 'most important'.  The new vectors are:
673 
674   THR -- interrupt raised when a machine check threshold counter
675   (typically counting ECC corrected errors of memory or cache) exceeds
676   a configurable threshold.  Only available on some systems.
677 
678   TRM -- a thermal event interrupt occurs when a temperature threshold
679   has been exceeded for the CPU.  This interrupt may also be generated
680   when the temperature drops back to normal.
681 
682   SPU -- a spurious interrupt is some interrupt that was raised then lowered
683   by some IO device before it could be fully processed by the APIC.  Hence
684   the APIC sees the interrupt but does not know what device it came from.
685   For this case the APIC will generate the interrupt with a IRQ vector
686   of 0xff. This might also be generated by chipset bugs.
687 
688   RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
689   sent from one CPU to another per the needs of the OS.  Typically,
690   their statistics are used by kernel developers and interested users to
691   determine the occurrence of interrupts of the given type.
692 
693 The above IRQ vectors are displayed only when relevant.  For example,
694 the threshold vector does not exist on x86_64 platforms.  Others are
695 suppressed when the system is a uniprocessor.  As of this writing, only
696 i386 and x86_64 platforms support the new IRQ vector displays.
697 
698 Of some interest is the introduction of the /proc/irq directory to 2.4.
699 It could be used to set IRQ to CPU affinity, this means that you can "hook" an
700 IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
701 irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
702 prof_cpu_mask.
703 
704 For example 
705   > ls /proc/irq/
706   0  10  12  14  16  18  2  4  6  8  prof_cpu_mask
707   1  11  13  15  17  19  3  5  7  9  default_smp_affinity
708   > ls /proc/irq/0/
709   smp_affinity
710 
711 smp_affinity is a bitmask, in which you can specify which CPUs can handle the
712 IRQ, you can set it by doing:
713 
714   > echo 1 > /proc/irq/10/smp_affinity
715 
716 This means that only the first CPU will handle the IRQ, but you can also echo
717 5 which means that only the first and third CPU can handle the IRQ.
718 
719 The contents of each smp_affinity file is the same by default:
720 
721   > cat /proc/irq/0/smp_affinity
722   ffffffff
723 
724 There is an alternate interface, smp_affinity_list which allows specifying
725 a cpu range instead of a bitmask:
726 
727   > cat /proc/irq/0/smp_affinity_list
728   1024-1031
729 
730 The default_smp_affinity mask applies to all non-active IRQs, which are the
731 IRQs which have not yet been allocated/activated, and hence which lack a
732 /proc/irq/[0-9]* directory.
733 
734 The node file on an SMP system shows the node to which the device using the IRQ
735 reports itself as being attached. This hardware locality information does not
736 include information about any possible driver locality preference.
737 
738 prof_cpu_mask specifies which CPUs are to be profiled by the system wide
739 profiler. Default value is ffffffff (all cpus if there are only 32 of them).
740 
741 The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
742 between all the CPUs which are allowed to handle it. As usual the kernel has
743 more info than you and does a better job than you, so the defaults are the
744 best choice for almost everyone.  [Note this applies only to those IO-APIC's
745 that support "Round Robin" interrupt distribution.]
746 
747 There are  three  more  important subdirectories in /proc: net, scsi, and sys.
748 The general  rule  is  that  the  contents,  or  even  the  existence of these
749 directories, depend  on your kernel configuration. If SCSI is not enabled, the
750 directory scsi  may  not  exist. The same is true with the net, which is there
751 only when networking support is present in the running kernel.
752 
753 The slabinfo  file  gives  information  about  memory usage at the slab level.
754 Linux uses  slab  pools for memory management above page level in version 2.2.
755 Commonly used  objects  have  their  own  slab  pool (such as network buffers,
756 directory cache, and so on).
757 
758 ..............................................................................
759 
760 > cat /proc/buddyinfo
761 
762 Node 0, zone      DMA      0      4      5      4      4      3 ...
763 Node 0, zone   Normal      1      0      0      1    101      8 ...
764 Node 0, zone  HighMem      2      0      0      1      1      0 ...
765 
766 External fragmentation is a problem under some workloads, and buddyinfo is a
767 useful tool for helping diagnose these problems.  Buddyinfo will give you a 
768 clue as to how big an area you can safely allocate, or why a previous
769 allocation failed.
770 
771 Each column represents the number of pages of a certain order which are 
772 available.  In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 
773 ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 
774 available in ZONE_NORMAL, etc... 
775 
776 More information relevant to external fragmentation can be found in
777 pagetypeinfo.
778 
779 > cat /proc/pagetypeinfo
780 Page block order: 9
781 Pages per block:  512
782 
783 Free pages count per migrate type at order       0      1      2      3      4      5      6      7      8      9     10
784 Node    0, zone      DMA, type    Unmovable      0      0      0      1      1      1      1      1      1      1      0
785 Node    0, zone      DMA, type  Reclaimable      0      0      0      0      0      0      0      0      0      0      0
786 Node    0, zone      DMA, type      Movable      1      1      2      1      2      1      1      0      1      0      2
787 Node    0, zone      DMA, type      Reserve      0      0      0      0      0      0      0      0      0      1      0
788 Node    0, zone      DMA, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
789 Node    0, zone    DMA32, type    Unmovable    103     54     77      1      1      1     11      8      7      1      9
790 Node    0, zone    DMA32, type  Reclaimable      0      0      2      1      0      0      0      0      1      0      0
791 Node    0, zone    DMA32, type      Movable    169    152    113     91     77     54     39     13      6      1    452
792 Node    0, zone    DMA32, type      Reserve      1      2      2      2      2      0      1      1      1      1      0
793 Node    0, zone    DMA32, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
794 
795 Number of blocks type     Unmovable  Reclaimable      Movable      Reserve      Isolate
796 Node 0, zone      DMA            2            0            5            1            0
797 Node 0, zone    DMA32           41            6          967            2            0
798 
799 Fragmentation avoidance in the kernel works by grouping pages of different
800 migrate types into the same contiguous regions of memory called page blocks.
801 A page block is typically the size of the default hugepage size e.g. 2MB on
802 X86-64. By keeping pages grouped based on their ability to move, the kernel
803 can reclaim pages within a page block to satisfy a high-order allocation.
804 
805 The pagetypinfo begins with information on the size of a page block. It
806 then gives the same type of information as buddyinfo except broken down
807 by migrate-type and finishes with details on how many page blocks of each
808 type exist.
809 
810 If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
811 from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
812 make an estimate of the likely number of huge pages that can be allocated
813 at a given point in time. All the "Movable" blocks should be allocatable
814 unless memory has been mlock()'d. Some of the Reclaimable blocks should
815 also be allocatable although a lot of filesystem metadata may have to be
816 reclaimed to achieve this.
817 
818 ..............................................................................
819 
820 meminfo:
821 
822 Provides information about distribution and utilization of memory.  This
823 varies by architecture and compile options.  The following is from a
824 16GB PIII, which has highmem enabled.  You may not have all of these fields.
825 
826 > cat /proc/meminfo
827 
828 MemTotal:     16344972 kB
829 MemFree:      13634064 kB
830 MemAvailable: 14836172 kB
831 Buffers:          3656 kB
832 Cached:        1195708 kB
833 SwapCached:          0 kB
834 Active:         891636 kB
835 Inactive:      1077224 kB
836 HighTotal:    15597528 kB
837 HighFree:     13629632 kB
838 LowTotal:       747444 kB
839 LowFree:          4432 kB
840 SwapTotal:           0 kB
841 SwapFree:            0 kB
842 Dirty:             968 kB
843 Writeback:           0 kB
844 AnonPages:      861800 kB
845 Mapped:         280372 kB
846 Shmem:             644 kB
847 Slab:           284364 kB
848 SReclaimable:   159856 kB
849 SUnreclaim:     124508 kB
850 PageTables:      24448 kB
851 NFS_Unstable:        0 kB
852 Bounce:              0 kB
853 WritebackTmp:        0 kB
854 CommitLimit:   7669796 kB
855 Committed_AS:   100056 kB
856 VmallocTotal:   112216 kB
857 VmallocUsed:       428 kB
858 VmallocChunk:   111088 kB
859 AnonHugePages:   49152 kB
860 ShmemHugePages:      0 kB
861 ShmemPmdMapped:      0 kB
862 
863 
864     MemTotal: Total usable ram (i.e. physical ram minus a few reserved
865               bits and the kernel binary code)
866      MemFree: The sum of LowFree+HighFree
867 MemAvailable: An estimate of how much memory is available for starting new
868               applications, without swapping. Calculated from MemFree,
869               SReclaimable, the size of the file LRU lists, and the low
870               watermarks in each zone.
871               The estimate takes into account that the system needs some
872               page cache to function well, and that not all reclaimable
873               slab will be reclaimable, due to items being in use. The
874               impact of those factors will vary from system to system.
875      Buffers: Relatively temporary storage for raw disk blocks
876               shouldn't get tremendously large (20MB or so)
877       Cached: in-memory cache for files read from the disk (the
878               pagecache).  Doesn't include SwapCached
879   SwapCached: Memory that once was swapped out, is swapped back in but
880               still also is in the swapfile (if memory is needed it
881               doesn't need to be swapped out AGAIN because it is already
882               in the swapfile. This saves I/O)
883       Active: Memory that has been used more recently and usually not
884               reclaimed unless absolutely necessary.
885     Inactive: Memory which has been less recently used.  It is more
886               eligible to be reclaimed for other purposes
887    HighTotal:
888     HighFree: Highmem is all memory above ~860MB of physical memory
889               Highmem areas are for use by userspace programs, or
890               for the pagecache.  The kernel must use tricks to access
891               this memory, making it slower to access than lowmem.
892     LowTotal:
893      LowFree: Lowmem is memory which can be used for everything that
894               highmem can be used for, but it is also available for the
895               kernel's use for its own data structures.  Among many
896               other things, it is where everything from the Slab is
897               allocated.  Bad things happen when you're out of lowmem.
898    SwapTotal: total amount of swap space available
899     SwapFree: Memory which has been evicted from RAM, and is temporarily
900               on the disk
901        Dirty: Memory which is waiting to get written back to the disk
902    Writeback: Memory which is actively being written back to the disk
903    AnonPages: Non-file backed pages mapped into userspace page tables
904 AnonHugePages: Non-file backed huge pages mapped into userspace page tables
905       Mapped: files which have been mmaped, such as libraries
906        Shmem: Total memory used by shared memory (shmem) and tmpfs
907 ShmemHugePages: Memory used by shared memory (shmem) and tmpfs allocated
908               with huge pages
909 ShmemPmdMapped: Shared memory mapped into userspace with huge pages
910         Slab: in-kernel data structures cache
911 SReclaimable: Part of Slab, that might be reclaimed, such as caches
912   SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
913   PageTables: amount of memory dedicated to the lowest level of page
914               tables.
915 NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
916               storage
917       Bounce: Memory used for block device "bounce buffers"
918 WritebackTmp: Memory used by FUSE for temporary writeback buffers
919  CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
920               this is the total amount of  memory currently available to
921               be allocated on the system. This limit is only adhered to
922               if strict overcommit accounting is enabled (mode 2 in
923               'vm.overcommit_memory').
924               The CommitLimit is calculated with the following formula:
925               CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
926                              overcommit_ratio / 100 + [total swap pages]
927               For example, on a system with 1G of physical RAM and 7G
928               of swap with a `vm.overcommit_ratio` of 30 it would
929               yield a CommitLimit of 7.3G.
930               For more details, see the memory overcommit documentation
931               in vm/overcommit-accounting.
932 Committed_AS: The amount of memory presently allocated on the system.
933               The committed memory is a sum of all of the memory which
934               has been allocated by processes, even if it has not been
935               "used" by them as of yet. A process which malloc()'s 1G
936               of memory, but only touches 300M of it will show up as
937               using 1G. This 1G is memory which has been "committed" to
938               by the VM and can be used at any time by the allocating
939               application. With strict overcommit enabled on the system
940               (mode 2 in 'vm.overcommit_memory'),allocations which would
941               exceed the CommitLimit (detailed above) will not be permitted.
942               This is useful if one needs to guarantee that processes will
943               not fail due to lack of memory once that memory has been
944               successfully allocated.
945 VmallocTotal: total size of vmalloc memory area
946  VmallocUsed: amount of vmalloc area which is used
947 VmallocChunk: largest contiguous block of vmalloc area which is free
948 
949 ..............................................................................
950 
951 vmallocinfo:
952 
953 Provides information about vmalloced/vmaped areas. One line per area,
954 containing the virtual address range of the area, size in bytes,
955 caller information of the creator, and optional information depending
956 on the kind of area :
957 
958  pages=nr    number of pages
959  phys=addr   if a physical address was specified
960  ioremap     I/O mapping (ioremap() and friends)
961  vmalloc     vmalloc() area
962  vmap        vmap()ed pages
963  user        VM_USERMAP area
964  vpages      buffer for pages pointers was vmalloced (huge area)
965  N<node>=nr  (Only on NUMA kernels)
966              Number of pages allocated on memory node <node>
967 
968 > cat /proc/vmallocinfo
969 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
970   /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
971 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
972   /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
973 0xffffc20000302000-0xffffc20000304000    8192 acpi_tb_verify_table+0x21/0x4f...
974   phys=7fee8000 ioremap
975 0xffffc20000304000-0xffffc20000307000   12288 acpi_tb_verify_table+0x21/0x4f...
976   phys=7fee7000 ioremap
977 0xffffc2000031d000-0xffffc2000031f000    8192 init_vdso_vars+0x112/0x210
978 0xffffc2000031f000-0xffffc2000032b000   49152 cramfs_uncompress_init+0x2e ...
979   /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
980 0xffffc2000033a000-0xffffc2000033d000   12288 sys_swapon+0x640/0xac0      ...
981   pages=2 vmalloc N1=2
982 0xffffc20000347000-0xffffc2000034c000   20480 xt_alloc_table_info+0xfe ...
983   /0x130 [x_tables] pages=4 vmalloc N0=4
984 0xffffffffa0000000-0xffffffffa000f000   61440 sys_init_module+0xc27/0x1d00 ...
985    pages=14 vmalloc N2=14
986 0xffffffffa000f000-0xffffffffa0014000   20480 sys_init_module+0xc27/0x1d00 ...
987    pages=4 vmalloc N1=4
988 0xffffffffa0014000-0xffffffffa0017000   12288 sys_init_module+0xc27/0x1d00 ...
989    pages=2 vmalloc N1=2
990 0xffffffffa0017000-0xffffffffa0022000   45056 sys_init_module+0xc27/0x1d00 ...
991    pages=10 vmalloc N0=10
992 
993 ..............................................................................
994 
995 softirqs:
996 
997 Provides counts of softirq handlers serviced since boot time, for each cpu.
998 
999 > cat /proc/softirqs
1000                 CPU0       CPU1       CPU2       CPU3
1001       HI:          0          0          0          0
1002    TIMER:      27166      27120      27097      27034
1003   NET_TX:          0          0          0         17
1004   NET_RX:         42          0          0         39
1005    BLOCK:          0          0        107       1121
1006  TASKLET:          0          0          0        290
1007    SCHED:      27035      26983      26971      26746
1008  HRTIMER:          0          0          0          0
1009      RCU:       1678       1769       2178       2250
1010 
1011 
1012 1.3 IDE devices in /proc/ide
1013 ----------------------------
1014 
1015 The subdirectory /proc/ide contains information about all IDE devices of which
1016 the kernel  is  aware.  There is one subdirectory for each IDE controller, the
1017 file drivers  and a link for each IDE device, pointing to the device directory
1018 in the controller specific subtree.
1019 
1020 The file  drivers  contains general information about the drivers used for the
1021 IDE devices:
1022 
1023   > cat /proc/ide/drivers
1024   ide-cdrom version 4.53
1025   ide-disk version 1.08
1026 
1027 More detailed  information  can  be  found  in  the  controller  specific
1028 subdirectories. These  are  named  ide0,  ide1  and  so  on.  Each  of  these
1029 directories contains the files shown in table 1-6.
1030 
1031 
1032 Table 1-6: IDE controller info in  /proc/ide/ide?
1033 ..............................................................................
1034  File    Content                                 
1035  channel IDE channel (0 or 1)                    
1036  config  Configuration (only for PCI/IDE bridge) 
1037  mate    Mate name                               
1038  model   Type/Chipset of IDE controller          
1039 ..............................................................................
1040 
1041 Each device  connected  to  a  controller  has  a separate subdirectory in the
1042 controllers directory.  The  files  listed in table 1-7 are contained in these
1043 directories.
1044 
1045 
1046 Table 1-7: IDE device information
1047 ..............................................................................
1048  File             Content                                    
1049  cache            The cache                                  
1050  capacity         Capacity of the medium (in 512Byte blocks) 
1051  driver           driver and version                         
1052  geometry         physical and logical geometry              
1053  identify         device identify block                      
1054  media            media type                                 
1055  model            device identifier                          
1056  settings         device setup                               
1057  smart_thresholds IDE disk management thresholds             
1058  smart_values     IDE disk management values                 
1059 ..............................................................................
1060 
1061 The most  interesting  file is settings. This file contains a nice overview of
1062 the drive parameters:
1063 
1064   # cat /proc/ide/ide0/hda/settings 
1065   name                    value           min             max             mode 
1066   ----                    -----           ---             ---             ---- 
1067   bios_cyl                526             0               65535           rw 
1068   bios_head               255             0               255             rw 
1069   bios_sect               63              0               63              rw 
1070   breada_readahead        4               0               127             rw 
1071   bswap                   0               0               1               r 
1072   file_readahead          72              0               2097151         rw 
1073   io_32bit                0               0               3               rw 
1074   keepsettings            0               0               1               rw 
1075   max_kb_per_request      122             1               127             rw 
1076   multcount               0               0               8               rw 
1077   nice1                   1               0               1               rw 
1078   nowerr                  0               0               1               rw 
1079   pio_mode                write-only      0               255             w 
1080   slow                    0               0               1               rw 
1081   unmaskirq               0               0               1               rw 
1082   using_dma               0               0               1               rw 
1083 
1084 
1085 1.4 Networking info in /proc/net
1086 --------------------------------
1087 
1088 The subdirectory  /proc/net  follows  the  usual  pattern. Table 1-8 shows the
1089 additional values  you  get  for  IP  version 6 if you configure the kernel to
1090 support this. Table 1-9 lists the files and their meaning.
1091 
1092 
1093 Table 1-8: IPv6 info in /proc/net
1094 ..............................................................................
1095  File       Content                                               
1096  udp6       UDP sockets (IPv6)                                    
1097  tcp6       TCP sockets (IPv6)                                    
1098  raw6       Raw device statistics (IPv6)                          
1099  igmp6      IP multicast addresses, which this host joined (IPv6) 
1100  if_inet6   List of IPv6 interface addresses                      
1101  ipv6_route Kernel routing table for IPv6                         
1102  rt6_stats  Global IPv6 routing tables statistics                 
1103  sockstat6  Socket statistics (IPv6)                              
1104  snmp6      Snmp data (IPv6)                                      
1105 ..............................................................................
1106 
1107 
1108 Table 1-9: Network info in /proc/net
1109 ..............................................................................
1110  File          Content                                                         
1111  arp           Kernel  ARP table                                               
1112  dev           network devices with statistics                                 
1113  dev_mcast     the Layer2 multicast groups a device is listening too
1114                (interface index, label, number of references, number of bound
1115                addresses). 
1116  dev_stat      network device status                                           
1117  ip_fwchains   Firewall chain linkage                                          
1118  ip_fwnames    Firewall chain names                                            
1119  ip_masq       Directory containing the masquerading tables                    
1120  ip_masquerade Major masquerading table                                        
1121  netstat       Network statistics                                              
1122  raw           raw device statistics                                           
1123  route         Kernel routing table                                            
1124  rpc           Directory containing rpc info                                   
1125  rt_cache      Routing cache                                                   
1126  snmp          SNMP data                                                       
1127  sockstat      Socket statistics                                               
1128  tcp           TCP  sockets                                                    
1129  udp           UDP sockets                                                     
1130  unix          UNIX domain sockets                                             
1131  wireless      Wireless interface data (Wavelan etc)                           
1132  igmp          IP multicast addresses, which this host joined                  
1133  psched        Global packet scheduler parameters.                             
1134  netlink       List of PF_NETLINK sockets                                      
1135  ip_mr_vifs    List of multicast virtual interfaces                            
1136  ip_mr_cache   List of multicast routing cache                                 
1137 ..............................................................................
1138 
1139 You can  use  this  information  to see which network devices are available in
1140 your system and how much traffic was routed over those devices:
1141 
1142   > cat /proc/net/dev 
1143   Inter-|Receive                                                   |[... 
1144    face |bytes    packets errs drop fifo frame compressed multicast|[... 
1145       lo:  908188   5596     0    0    0     0          0         0 [...         
1146     ppp0:15475140  20721   410    0    0   410          0         0 [...  
1147     eth0:  614530   7085     0    0    0     0          0         1 [... 
1148    
1149   ...] Transmit 
1150   ...] bytes    packets errs drop fifo colls carrier compressed 
1151   ...]  908188     5596    0    0    0     0       0          0 
1152   ...] 1375103    17405    0    0    0     0       0          0 
1153   ...] 1703981     5535    0    0    0     3       0          0 
1154 
1155 In addition, each Channel Bond interface has its own directory.  For
1156 example, the bond0 device will have a directory called /proc/net/bond0/.
1157 It will contain information that is specific to that bond, such as the
1158 current slaves of the bond, the link status of the slaves, and how
1159 many times the slaves link has failed.
1160 
1161 1.5 SCSI info
1162 -------------
1163 
1164 If you  have  a  SCSI  host adapter in your system, you'll find a subdirectory
1165 named after  the driver for this adapter in /proc/scsi. You'll also see a list
1166 of all recognized SCSI devices in /proc/scsi:
1167 
1168   >cat /proc/scsi/scsi 
1169   Attached devices: 
1170   Host: scsi0 Channel: 00 Id: 00 Lun: 00 
1171     Vendor: IBM      Model: DGHS09U          Rev: 03E0 
1172     Type:   Direct-Access                    ANSI SCSI revision: 03 
1173   Host: scsi0 Channel: 00 Id: 06 Lun: 00 
1174     Vendor: PIONEER  Model: CD-ROM DR-U06S   Rev: 1.04 
1175     Type:   CD-ROM                           ANSI SCSI revision: 02 
1176 
1177 
1178 The directory  named  after  the driver has one file for each adapter found in
1179 the system.  These  files  contain information about the controller, including
1180 the used  IRQ  and  the  IO  address range. The amount of information shown is
1181 dependent on  the adapter you use. The example shows the output for an Adaptec
1182 AHA-2940 SCSI adapter:
1183 
1184   > cat /proc/scsi/aic7xxx/0 
1185    
1186   Adaptec AIC7xxx driver version: 5.1.19/3.2.4 
1187   Compile Options: 
1188     TCQ Enabled By Default : Disabled 
1189     AIC7XXX_PROC_STATS     : Disabled 
1190     AIC7XXX_RESET_DELAY    : 5 
1191   Adapter Configuration: 
1192              SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 
1193                              Ultra Wide Controller 
1194       PCI MMAPed I/O Base: 0xeb001000 
1195    Adapter SEEPROM Config: SEEPROM found and used. 
1196         Adaptec SCSI BIOS: Enabled 
1197                       IRQ: 10 
1198                      SCBs: Active 0, Max Active 2, 
1199                            Allocated 15, HW 16, Page 255 
1200                Interrupts: 160328 
1201         BIOS Control Word: 0x18b6 
1202      Adapter Control Word: 0x005b 
1203      Extended Translation: Enabled 
1204   Disconnect Enable Flags: 0xffff 
1205        Ultra Enable Flags: 0x0001 
1206    Tag Queue Enable Flags: 0x0000 
1207   Ordered Queue Tag Flags: 0x0000 
1208   Default Tag Queue Depth: 8 
1209       Tagged Queue By Device array for aic7xxx host instance 0: 
1210         {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 
1211       Actual queue depth per device for aic7xxx host instance 0: 
1212         {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 
1213   Statistics: 
1214   (scsi0:0:0:0) 
1215     Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 
1216     Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 
1217     Total transfers 160151 (74577 reads and 85574 writes) 
1218   (scsi0:0:6:0) 
1219     Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 
1220     Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 
1221     Total transfers 0 (0 reads and 0 writes) 
1222 
1223 
1224 1.6 Parallel port info in /proc/parport
1225 ---------------------------------------
1226 
1227 The directory  /proc/parport  contains information about the parallel ports of
1228 your system.  It  has  one  subdirectory  for  each port, named after the port
1229 number (0,1,2,...).
1230 
1231 These directories contain the four files shown in Table 1-10.
1232 
1233 
1234 Table 1-10: Files in /proc/parport
1235 ..............................................................................
1236  File      Content                                                             
1237  autoprobe Any IEEE-1284 device ID information that has been acquired.         
1238  devices   list of the device drivers using that port. A + will appear by the
1239            name of the device currently using the port (it might not appear
1240            against any). 
1241  hardware  Parallel port's base address, IRQ line and DMA channel.             
1242  irq       IRQ that parport is using for that port. This is in a separate
1243            file to allow you to alter it by writing a new value in (IRQ
1244            number or none). 
1245 ..............................................................................
1246 
1247 1.7 TTY info in /proc/tty
1248 -------------------------
1249 
1250 Information about  the  available  and actually used tty's can be found in the
1251 directory /proc/tty.You'll  find  entries  for drivers and line disciplines in
1252 this directory, as shown in Table 1-11.
1253 
1254 
1255 Table 1-11: Files in /proc/tty
1256 ..............................................................................
1257  File          Content                                        
1258  drivers       list of drivers and their usage                
1259  ldiscs        registered line disciplines                    
1260  driver/serial usage statistic and status of single tty lines 
1261 ..............................................................................
1262 
1263 To see  which  tty's  are  currently in use, you can simply look into the file
1264 /proc/tty/drivers:
1265 
1266   > cat /proc/tty/drivers 
1267   pty_slave            /dev/pts      136   0-255 pty:slave 
1268   pty_master           /dev/ptm      128   0-255 pty:master 
1269   pty_slave            /dev/ttyp       3   0-255 pty:slave 
1270   pty_master           /dev/pty        2   0-255 pty:master 
1271   serial               /dev/cua        5   64-67 serial:callout 
1272   serial               /dev/ttyS       4   64-67 serial 
1273   /dev/tty0            /dev/tty0       4       0 system:vtmaster 
1274   /dev/ptmx            /dev/ptmx       5       2 system 
1275   /dev/console         /dev/console    5       1 system:console 
1276   /dev/tty             /dev/tty        5       0 system:/dev/tty 
1277   unknown              /dev/tty        4    1-63 console 
1278 
1279 
1280 1.8 Miscellaneous kernel statistics in /proc/stat
1281 -------------------------------------------------
1282 
1283 Various pieces   of  information about  kernel activity  are  available in the
1284 /proc/stat file.  All  of  the numbers reported  in  this file are  aggregates
1285 since the system first booted.  For a quick look, simply cat the file:
1286 
1287   > cat /proc/stat
1288   cpu  2255 34 2290 22625563 6290 127 456 0 0 0
1289   cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1290   cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1291   intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1292   ctxt 1990473
1293   btime 1062191376
1294   processes 2915
1295   procs_running 1
1296   procs_blocked 0
1297   softirq 183433 0 21755 12 39 1137 231 21459 2263
1298 
1299 The very first  "cpu" line aggregates the  numbers in all  of the other "cpuN"
1300 lines.  These numbers identify the amount of time the CPU has spent performing
1301 different kinds of work.  Time units are in USER_HZ (typically hundredths of a
1302 second).  The meanings of the columns are as follows, from left to right:
1303 
1304 - user: normal processes executing in user mode
1305 - nice: niced processes executing in user mode
1306 - system: processes executing in kernel mode
1307 - idle: twiddling thumbs
1308 - iowait: waiting for I/O to complete
1309 - irq: servicing interrupts
1310 - softirq: servicing softirqs
1311 - steal: involuntary wait
1312 - guest: running a normal guest
1313 - guest_nice: running a niced guest
1314 
1315 The "intr" line gives counts of interrupts  serviced since boot time, for each
1316 of the  possible system interrupts.   The first  column  is the  total of  all
1317 interrupts serviced  including  unnumbered  architecture specific  interrupts;
1318 each  subsequent column is the  total for that particular numbered interrupt.
1319 Unnumbered interrupts are not shown, only summed into the total.
1320 
1321 The "ctxt" line gives the total number of context switches across all CPUs.
1322 
1323 The "btime" line gives  the time at which the  system booted, in seconds since
1324 the Unix epoch.
1325 
1326 The "processes" line gives the number  of processes and threads created, which
1327 includes (but  is not limited  to) those  created by  calls to the  fork() and
1328 clone() system calls.
1329 
1330 The "procs_running" line gives the total number of threads that are
1331 running or ready to run (i.e., the total number of runnable threads).
1332 
1333 The   "procs_blocked" line gives  the  number of  processes currently blocked,
1334 waiting for I/O to complete.
1335 
1336 The "softirq" line gives counts of softirqs serviced since boot time, for each
1337 of the possible system softirqs. The first column is the total of all
1338 softirqs serviced; each subsequent column is the total for that particular
1339 softirq.
1340 
1341 
1342 1.9 Ext4 file system parameters
1343 -------------------------------
1344 
1345 Information about mounted ext4 file systems can be found in
1346 /proc/fs/ext4.  Each mounted filesystem will have a directory in
1347 /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1348 /proc/fs/ext4/dm-0).   The files in each per-device directory are shown
1349 in Table 1-12, below.
1350 
1351 Table 1-12: Files in /proc/fs/ext4/<devname>
1352 ..............................................................................
1353  File            Content                                        
1354  mb_groups       details of multiblock allocator buddy cache of free blocks
1355 ..............................................................................
1356 
1357 2.0 /proc/consoles
1358 ------------------
1359 Shows registered system console lines.
1360 
1361 To see which character device lines are currently used for the system console
1362 /dev/console, you may simply look into the file /proc/consoles:
1363 
1364   > cat /proc/consoles
1365   tty0                 -WU (ECp)       4:7
1366   ttyS0                -W- (Ep)        4:64
1367 
1368 The columns are:
1369 
1370   device               name of the device
1371   operations           R = can do read operations
1372                        W = can do write operations
1373                        U = can do unblank
1374   flags                E = it is enabled
1375                        C = it is preferred console
1376                        B = it is primary boot console
1377                        p = it is used for printk buffer
1378                        b = it is not a TTY but a Braille device
1379                        a = it is safe to use when cpu is offline
1380   major:minor          major and minor number of the device separated by a colon
1381 
1382 ------------------------------------------------------------------------------
1383 Summary
1384 ------------------------------------------------------------------------------
1385 The /proc file system serves information about the running system. It not only
1386 allows access to process data but also allows you to request the kernel status
1387 by reading files in the hierarchy.
1388 
1389 The directory  structure  of /proc reflects the types of information and makes
1390 it easy, if not obvious, where to look for specific data.
1391 ------------------------------------------------------------------------------
1392 
1393 ------------------------------------------------------------------------------
1394 CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1395 ------------------------------------------------------------------------------
1396 
1397 ------------------------------------------------------------------------------
1398 In This Chapter
1399 ------------------------------------------------------------------------------
1400 * Modifying kernel parameters by writing into files found in /proc/sys
1401 * Exploring the files which modify certain parameters
1402 * Review of the /proc/sys file tree
1403 ------------------------------------------------------------------------------
1404 
1405 
1406 A very  interesting part of /proc is the directory /proc/sys. This is not only
1407 a source  of  information,  it also allows you to change parameters within the
1408 kernel. Be  very  careful  when attempting this. You can optimize your system,
1409 but you  can  also  cause  it  to  crash.  Never  alter kernel parameters on a
1410 production system.  Set  up  a  development machine and test to make sure that
1411 everything works  the  way  you want it to. You may have no alternative but to
1412 reboot the machine once an error has been made.
1413 
1414 To change  a  value,  simply  echo  the new value into the file. An example is
1415 given below  in the section on the file system data. You need to be root to do
1416 this. You  can  create  your  own  boot script to perform this every time your
1417 system boots.
1418 
1419 The files  in /proc/sys can be used to fine tune and monitor miscellaneous and
1420 general things  in  the operation of the Linux kernel. Since some of the files
1421 can inadvertently  disrupt  your  system,  it  is  advisable  to  read  both
1422 documentation and  source  before actually making adjustments. In any case, be
1423 very careful  when  writing  to  any  of these files. The entries in /proc may
1424 change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1425 review the kernel documentation in the directory /usr/src/linux/Documentation.
1426 This chapter  is  heavily  based  on the documentation included in the pre 2.2
1427 kernels, and became part of it in version 2.2.1 of the Linux kernel.
1428 
1429 Please see: Documentation/sysctl/ directory for descriptions of these
1430 entries.
1431 
1432 ------------------------------------------------------------------------------
1433 Summary
1434 ------------------------------------------------------------------------------
1435 Certain aspects  of  kernel  behavior  can be modified at runtime, without the
1436 need to  recompile  the kernel, or even to reboot the system. The files in the
1437 /proc/sys tree  can  not only be read, but also modified. You can use the echo
1438 command to write value into these files, thereby changing the default settings
1439 of the kernel.
1440 ------------------------------------------------------------------------------
1441 
1442 ------------------------------------------------------------------------------
1443 CHAPTER 3: PER-PROCESS PARAMETERS
1444 ------------------------------------------------------------------------------
1445 
1446 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1447 --------------------------------------------------------------------------------
1448 
1449 These file can be used to adjust the badness heuristic used to select which
1450 process gets killed in out of memory conditions.
1451 
1452 The badness heuristic assigns a value to each candidate task ranging from 0
1453 (never kill) to 1000 (always kill) to determine which process is targeted.  The
1454 units are roughly a proportion along that range of allowed memory the process
1455 may allocate from based on an estimation of its current memory and swap use.
1456 For example, if a task is using all allowed memory, its badness score will be
1457 1000.  If it is using half of its allowed memory, its score will be 500.
1458 
1459 There is an additional factor included in the badness score: the current memory
1460 and swap usage is discounted by 3% for root processes.
1461 
1462 The amount of "allowed" memory depends on the context in which the oom killer
1463 was called.  If it is due to the memory assigned to the allocating task's cpuset
1464 being exhausted, the allowed memory represents the set of mems assigned to that
1465 cpuset.  If it is due to a mempolicy's node(s) being exhausted, the allowed
1466 memory represents the set of mempolicy nodes.  If it is due to a memory
1467 limit (or swap limit) being reached, the allowed memory is that configured
1468 limit.  Finally, if it is due to the entire system being out of memory, the
1469 allowed memory represents all allocatable resources.
1470 
1471 The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1472 is used to determine which task to kill.  Acceptable values range from -1000
1473 (OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX).  This allows userspace to
1474 polarize the preference for oom killing either by always preferring a certain
1475 task or completely disabling it.  The lowest possible value, -1000, is
1476 equivalent to disabling oom killing entirely for that task since it will always
1477 report a badness score of 0.
1478 
1479 Consequently, it is very simple for userspace to define the amount of memory to
1480 consider for each task.  Setting a /proc/<pid>/oom_score_adj value of +500, for
1481 example, is roughly equivalent to allowing the remainder of tasks sharing the
1482 same system, cpuset, mempolicy, or memory controller resources to use at least
1483 50% more memory.  A value of -500, on the other hand, would be roughly
1484 equivalent to discounting 50% of the task's allowed memory from being considered
1485 as scoring against the task.
1486 
1487 For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1488 be used to tune the badness score.  Its acceptable values range from -16
1489 (OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1490 (OOM_DISABLE) to disable oom killing entirely for that task.  Its value is
1491 scaled linearly with /proc/<pid>/oom_score_adj.
1492 
1493 The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1494 value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1495 requires CAP_SYS_RESOURCE.
1496 
1497 Caveat: when a parent task is selected, the oom killer will sacrifice any first
1498 generation children with separate address spaces instead, if possible.  This
1499 avoids servers and important system daemons from being killed and loses the
1500 minimal amount of work.
1501 
1502 
1503 3.2 /proc/<pid>/oom_score - Display current oom-killer score
1504 -------------------------------------------------------------
1505 
1506 This file can be used to check the current score used by the oom-killer is for
1507 any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1508 process should be killed in an out-of-memory situation.
1509 
1510 
1511 3.3  /proc/<pid>/io - Display the IO accounting fields
1512 -------------------------------------------------------
1513 
1514 This file contains IO statistics for each running process
1515 
1516 Example
1517 -------
1518 
1519 test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1520 [1] 3828
1521 
1522 test:/tmp # cat /proc/3828/io
1523 rchar: 323934931
1524 wchar: 323929600
1525 syscr: 632687
1526 syscw: 632675
1527 read_bytes: 0
1528 write_bytes: 323932160
1529 cancelled_write_bytes: 0
1530 
1531 
1532 Description
1533 -----------
1534 
1535 rchar
1536 -----
1537 
1538 I/O counter: chars read
1539 The number of bytes which this task has caused to be read from storage. This
1540 is simply the sum of bytes which this process passed to read() and pread().
1541 It includes things like tty IO and it is unaffected by whether or not actual
1542 physical disk IO was required (the read might have been satisfied from
1543 pagecache)
1544 
1545 
1546 wchar
1547 -----
1548 
1549 I/O counter: chars written
1550 The number of bytes which this task has caused, or shall cause to be written
1551 to disk. Similar caveats apply here as with rchar.
1552 
1553 
1554 syscr
1555 -----
1556 
1557 I/O counter: read syscalls
1558 Attempt to count the number of read I/O operations, i.e. syscalls like read()
1559 and pread().
1560 
1561 
1562 syscw
1563 -----
1564 
1565 I/O counter: write syscalls
1566 Attempt to count the number of write I/O operations, i.e. syscalls like
1567 write() and pwrite().
1568 
1569 
1570 read_bytes
1571 ----------
1572 
1573 I/O counter: bytes read
1574 Attempt to count the number of bytes which this process really did cause to
1575 be fetched from the storage layer. Done at the submit_bio() level, so it is
1576 accurate for block-backed filesystems. <please add status regarding NFS and
1577 CIFS at a later time>
1578 
1579 
1580 write_bytes
1581 -----------
1582 
1583 I/O counter: bytes written
1584 Attempt to count the number of bytes which this process caused to be sent to
1585 the storage layer. This is done at page-dirtying time.
1586 
1587 
1588 cancelled_write_bytes
1589 ---------------------
1590 
1591 The big inaccuracy here is truncate. If a process writes 1MB to a file and
1592 then deletes the file, it will in fact perform no writeout. But it will have
1593 been accounted as having caused 1MB of write.
1594 In other words: The number of bytes which this process caused to not happen,
1595 by truncating pagecache. A task can cause "negative" IO too. If this task
1596 truncates some dirty pagecache, some IO which another task has been accounted
1597 for (in its write_bytes) will not be happening. We _could_ just subtract that
1598 from the truncating task's write_bytes, but there is information loss in doing
1599 that.
1600 
1601 
1602 Note
1603 ----
1604 
1605 At its current implementation state, this is a bit racy on 32-bit machines: if
1606 process A reads process B's /proc/pid/io while process B is updating one of
1607 those 64-bit counters, process A could see an intermediate result.
1608 
1609 
1610 More information about this can be found within the taskstats documentation in
1611 Documentation/accounting.
1612 
1613 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1614 ---------------------------------------------------------------
1615 When a process is dumped, all anonymous memory is written to a core file as
1616 long as the size of the core file isn't limited. But sometimes we don't want
1617 to dump some memory segments, for example, huge shared memory or DAX.
1618 Conversely, sometimes we want to save file-backed memory segments into a core
1619 file, not only the individual files.
1620 
1621 /proc/<pid>/coredump_filter allows you to customize which memory segments
1622 will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1623 of memory types. If a bit of the bitmask is set, memory segments of the
1624 corresponding memory type are dumped, otherwise they are not dumped.
1625 
1626 The following 9 memory types are supported:
1627   - (bit 0) anonymous private memory
1628   - (bit 1) anonymous shared memory
1629   - (bit 2) file-backed private memory
1630   - (bit 3) file-backed shared memory
1631   - (bit 4) ELF header pages in file-backed private memory areas (it is
1632             effective only if the bit 2 is cleared)
1633   - (bit 5) hugetlb private memory
1634   - (bit 6) hugetlb shared memory
1635   - (bit 7) DAX private memory
1636   - (bit 8) DAX shared memory
1637 
1638   Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1639   are always dumped regardless of the bitmask status.
1640 
1641   Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
1642   only affected by bit 5-6, and DAX is only affected by bits 7-8.
1643 
1644 The default value of coredump_filter is 0x33; this means all anonymous memory
1645 segments, ELF header pages and hugetlb private memory are dumped.
1646 
1647 If you don't want to dump all shared memory segments attached to pid 1234,
1648 write 0x31 to the process's proc file.
1649 
1650   $ echo 0x31 > /proc/1234/coredump_filter
1651 
1652 When a new process is created, the process inherits the bitmask status from its
1653 parent. It is useful to set up coredump_filter before the program runs.
1654 For example:
1655 
1656   $ echo 0x7 > /proc/self/coredump_filter
1657   $ ./some_program
1658 
1659 3.5     /proc/<pid>/mountinfo - Information about mounts
1660 --------------------------------------------------------
1661 
1662 This file contains lines of the form:
1663 
1664 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1665 (1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
1666 
1667 (1) mount ID:  unique identifier of the mount (may be reused after umount)
1668 (2) parent ID:  ID of parent (or of self for the top of the mount tree)
1669 (3) major:minor:  value of st_dev for files on filesystem
1670 (4) root:  root of the mount within the filesystem
1671 (5) mount point:  mount point relative to the process's root
1672 (6) mount options:  per mount options
1673 (7) optional fields:  zero or more fields of the form "tag[:value]"
1674 (8) separator:  marks the end of the optional fields
1675 (9) filesystem type:  name of filesystem of the form "type[.subtype]"
1676 (10) mount source:  filesystem specific information or "none"
1677 (11) super options:  per super block options
1678 
1679 Parsers should ignore all unrecognised optional fields.  Currently the
1680 possible optional fields are:
1681 
1682 shared:X  mount is shared in peer group X
1683 master:X  mount is slave to peer group X
1684 propagate_from:X  mount is slave and receives propagation from peer group X (*)
1685 unbindable  mount is unbindable
1686 
1687 (*) X is the closest dominant peer group under the process's root.  If
1688 X is the immediate master of the mount, or if there's no dominant peer
1689 group under the same root, then only the "master:X" field is present
1690 and not the "propagate_from:X" field.
1691 
1692 For more information on mount propagation see:
1693 
1694   Documentation/filesystems/sharedsubtree.txt
1695 
1696 
1697 3.6     /proc/<pid>/comm  & /proc/<pid>/task/<tid>/comm
1698 --------------------------------------------------------
1699 These files provide a method to access a tasks comm value. It also allows for
1700 a task to set its own or one of its thread siblings comm value. The comm value
1701 is limited in size compared to the cmdline value, so writing anything longer
1702 then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1703 comm value.
1704 
1705 
1706 3.7     /proc/<pid>/task/<tid>/children - Information about task children
1707 -------------------------------------------------------------------------
1708 This file provides a fast way to retrieve first level children pids
1709 of a task pointed by <pid>/<tid> pair. The format is a space separated
1710 stream of pids.
1711 
1712 Note the "first level" here -- if a child has own children they will
1713 not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1714 to obtain the descendants.
1715 
1716 Since this interface is intended to be fast and cheap it doesn't
1717 guarantee to provide precise results and some children might be
1718 skipped, especially if they've exited right after we printed their
1719 pids, so one need to either stop or freeze processes being inspected
1720 if precise results are needed.
1721 
1722 
1723 3.8     /proc/<pid>/fdinfo/<fd> - Information about opened file
1724 ---------------------------------------------------------------
1725 This file provides information associated with an opened file. The regular
1726 files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1727 represents the current offset of the opened file in decimal form [see lseek(2)
1728 for details], 'flags' denotes the octal O_xxx mask the file has been
1729 created with [see open(2) for details] and 'mnt_id' represents mount ID of
1730 the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1731 for details].
1732 
1733 A typical output is
1734 
1735         pos:    0
1736         flags:  0100002
1737         mnt_id: 19
1738 
1739 All locks associated with a file descriptor are shown in its fdinfo too.
1740 
1741 lock:       1: FLOCK  ADVISORY  WRITE 359 00:13:11691 0 EOF
1742 
1743 The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1744 pair provide additional information particular to the objects they represent.
1745 
1746         Eventfd files
1747         ~~~~~~~~~~~~~
1748         pos:    0
1749         flags:  04002
1750         mnt_id: 9
1751         eventfd-count:  5a
1752 
1753         where 'eventfd-count' is hex value of a counter.
1754 
1755         Signalfd files
1756         ~~~~~~~~~~~~~~
1757         pos:    0
1758         flags:  04002
1759         mnt_id: 9
1760         sigmask:        0000000000000200
1761 
1762         where 'sigmask' is hex value of the signal mask associated
1763         with a file.
1764 
1765         Epoll files
1766         ~~~~~~~~~~~
1767         pos:    0
1768         flags:  02
1769         mnt_id: 9
1770         tfd:        5 events:       1d data: ffffffffffffffff
1771 
1772         where 'tfd' is a target file descriptor number in decimal form,
1773         'events' is events mask being watched and the 'data' is data
1774         associated with a target [see epoll(7) for more details].
1775 
1776         Fsnotify files
1777         ~~~~~~~~~~~~~~
1778         For inotify files the format is the following
1779 
1780         pos:    0
1781         flags:  02000000
1782         inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1783 
1784         where 'wd' is a watch descriptor in decimal form, ie a target file
1785         descriptor number, 'ino' and 'sdev' are inode and device where the
1786         target file resides and the 'mask' is the mask of events, all in hex
1787         form [see inotify(7) for more details].
1788 
1789         If the kernel was built with exportfs support, the path to the target
1790         file is encoded as a file handle.  The file handle is provided by three
1791         fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1792         format.
1793 
1794         If the kernel is built without exportfs support the file handle won't be
1795         printed out.
1796 
1797         If there is no inotify mark attached yet the 'inotify' line will be omitted.
1798 
1799         For fanotify files the format is
1800 
1801         pos:    0
1802         flags:  02
1803         mnt_id: 9
1804         fanotify flags:10 event-flags:0
1805         fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1806         fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1807 
1808         where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1809         call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1810         flags associated with mark which are tracked separately from events
1811         mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1812         mask and 'ignored_mask' is the mask of events which are to be ignored.
1813         All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1814         does provide information about flags and mask used in fanotify_mark
1815         call [see fsnotify manpage for details].
1816 
1817         While the first three lines are mandatory and always printed, the rest is
1818         optional and may be omitted if no marks created yet.
1819 
1820         Timerfd files
1821         ~~~~~~~~~~~~~
1822 
1823         pos:    0
1824         flags:  02
1825         mnt_id: 9
1826         clockid: 0
1827         ticks: 0
1828         settime flags: 01
1829         it_value: (0, 49406829)
1830         it_interval: (1, 0)
1831 
1832         where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
1833         that have occurred [see timerfd_create(2) for details]. 'settime flags' are
1834         flags in octal form been used to setup the timer [see timerfd_settime(2) for
1835         details]. 'it_value' is remaining time until the timer exiration.
1836         'it_interval' is the interval for the timer. Note the timer might be set up
1837         with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
1838         still exhibits timer's remaining time.
1839 
1840 3.9     /proc/<pid>/map_files - Information about memory mapped files
1841 ---------------------------------------------------------------------
1842 This directory contains symbolic links which represent memory mapped files
1843 the process is maintaining.  Example output:
1844 
1845      | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
1846      | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
1847      | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
1848      | ...
1849      | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
1850      | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
1851 
1852 The name of a link represents the virtual memory bounds of a mapping, i.e.
1853 vm_area_struct::vm_start-vm_area_struct::vm_end.
1854 
1855 The main purpose of the map_files is to retrieve a set of memory mapped
1856 files in a fast way instead of parsing /proc/<pid>/maps or
1857 /proc/<pid>/smaps, both of which contain many more records.  At the same
1858 time one can open(2) mappings from the listings of two processes and
1859 comparing their inode numbers to figure out which anonymous memory areas
1860 are actually shared.
1861 
1862 3.10    /proc/<pid>/timerslack_ns - Task timerslack value
1863 ---------------------------------------------------------
1864 This file provides the value of the task's timerslack value in nanoseconds.
1865 This value specifies a amount of time that normal timers may be deferred
1866 in order to coalesce timers and avoid unnecessary wakeups.
1867 
1868 This allows a task's interactivity vs power consumption trade off to be
1869 adjusted.
1870 
1871 Writing 0 to the file will set the tasks timerslack to the default value.
1872 
1873 Valid values are from 0 - ULLONG_MAX
1874 
1875 An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
1876 permissions on the task specified to change its timerslack_ns value.
1877 
1878 
1879 ------------------------------------------------------------------------------
1880 Configuring procfs
1881 ------------------------------------------------------------------------------
1882 
1883 4.1     Mount options
1884 ---------------------
1885 
1886 The following mount options are supported:
1887 
1888         hidepid=        Set /proc/<pid>/ access mode.
1889         gid=            Set the group authorized to learn processes information.
1890 
1891 hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1892 (default).
1893 
1894 hidepid=1 means users may not access any /proc/<pid>/ directories but their
1895 own.  Sensitive files like cmdline, sched*, status are now protected against
1896 other users.  This makes it impossible to learn whether any user runs
1897 specific program (given the program doesn't reveal itself by its behaviour).
1898 As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1899 poorly written programs passing sensitive information via program arguments are
1900 now protected against local eavesdroppers.
1901 
1902 hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1903 users.  It doesn't mean that it hides a fact whether a process with a specific
1904 pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1905 but it hides process' uid and gid, which may be learned by stat()'ing
1906 /proc/<pid>/ otherwise.  It greatly complicates an intruder's task of gathering
1907 information about running processes, whether some daemon runs with elevated
1908 privileges, whether other user runs some sensitive program, whether other users
1909 run any program at all, etc.
1910 
1911 gid= defines a group authorized to learn processes information otherwise
1912 prohibited by hidepid=.  If you use some daemon like identd which needs to learn
1913 information about processes information, just add identd to this group.

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