Version:  2.0.40 2.2.26 2.4.37 3.8 3.9 3.10 3.11 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

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

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