Version:  2.0.40 2.2.26 2.4.37 3.4 3.5 3.6 3.7 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

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          If CONFIG_KALLSYMS is set, a pre-decoded wchan
144  pagemap        Page table
145  stack          Report full stack trace, enable via CONFIG_STACKTRACE
146  smaps          a extension based on maps, showing the memory consumption of
147                 each mapping and flags associated with it
148  numa_maps      an extension based on maps, showing the memory locality and
149                 binding policy as well as mem usage (in pages) of each mapping.
150 ..............................................................................
151 
152 For example, to get the status information of a process, all you have to do is
153 read the file /proc/PID/status:
154 
155   >cat /proc/self/status
156   Name:   cat
157   State:  R (running)
158   Tgid:   5452
159   Pid:    5452
160   PPid:   743
161   TracerPid:      0                                             (2.4)
162   Uid:    501     501     501     501
163   Gid:    100     100     100     100
164   FDSize: 256
165   Groups: 100 14 16
166   VmPeak:     5004 kB
167   VmSize:     5004 kB
168   VmLck:         0 kB
169   VmHWM:       476 kB
170   VmRSS:       476 kB
171   VmData:      156 kB
172   VmStk:        88 kB
173   VmExe:        68 kB
174   VmLib:      1412 kB
175   VmPTE:        20 kb
176   VmSwap:        0 kB
177   Threads:        1
178   SigQ:   0/28578
179   SigPnd: 0000000000000000
180   ShdPnd: 0000000000000000
181   SigBlk: 0000000000000000
182   SigIgn: 0000000000000000
183   SigCgt: 0000000000000000
184   CapInh: 00000000fffffeff
185   CapPrm: 0000000000000000
186   CapEff: 0000000000000000
187   CapBnd: ffffffffffffffff
188   Seccomp:        0
189   voluntary_ctxt_switches:        0
190   nonvoluntary_ctxt_switches:     1
191 
192 This shows you nearly the same information you would get if you viewed it with
193 the ps  command.  In  fact,  ps  uses  the  proc  file  system  to  obtain its
194 information.  But you get a more detailed  view of the  process by reading the
195 file /proc/PID/status. It fields are described in table 1-2.
196 
197 The  statm  file  contains  more  detailed  information about the process
198 memory usage. Its seven fields are explained in Table 1-3.  The stat file
199 contains details information about the process itself.  Its fields are
200 explained in Table 1-4.
201 
202 (for SMP CONFIG users)
203 For making accounting scalable, RSS related information are handled in
204 asynchronous manner and the vaule may not be very precise. To see a precise
205 snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
206 It's slow but very precise.
207 
208 Table 1-2: Contents of the status files (as of 2.6.30-rc7)
209 ..............................................................................
210  Field                       Content
211  Name                        filename of the executable
212  State                       state (R is running, S is sleeping, D is sleeping
213                              in an uninterruptible wait, Z is zombie,
214                              T is traced or stopped)
215  Tgid                        thread group ID
216  Pid                         process id
217  PPid                        process id of the parent process
218  TracerPid                   PID of process tracing this process (0 if not)
219  Uid                         Real, effective, saved set, and  file system UIDs
220  Gid                         Real, effective, saved set, and  file system GIDs
221  FDSize                      number of file descriptor slots currently allocated
222  Groups                      supplementary group list
223  VmPeak                      peak virtual memory size
224  VmSize                      total program size
225  VmLck                       locked memory size
226  VmHWM                       peak resident set size ("high water mark")
227  VmRSS                       size of memory portions
228  VmData                      size of data, stack, and text segments
229  VmStk                       size of data, stack, and text segments
230  VmExe                       size of text segment
231  VmLib                       size of shared library code
232  VmPTE                       size of page table entries
233  VmSwap                      size of swap usage (the number of referred swapents)
234  Threads                     number of threads
235  SigQ                        number of signals queued/max. number for queue
236  SigPnd                      bitmap of pending signals for the thread
237  ShdPnd                      bitmap of shared pending signals for the process
238  SigBlk                      bitmap of blocked signals
239  SigIgn                      bitmap of ignored signals
240  SigCgt                      bitmap of caught signals
241  CapInh                      bitmap of inheritable capabilities
242  CapPrm                      bitmap of permitted capabilities
243  CapEff                      bitmap of effective capabilities
244  CapBnd                      bitmap of capabilities bounding set
245  Seccomp                     seccomp mode, like prctl(PR_GET_SECCOMP, ...)
246  Cpus_allowed                mask of CPUs on which this process may run
247  Cpus_allowed_list           Same as previous, but in "list format"
248  Mems_allowed                mask of memory nodes allowed to this process
249  Mems_allowed_list           Same as previous, but in "list format"
250  voluntary_ctxt_switches     number of voluntary context switches
251  nonvoluntary_ctxt_switches  number of non voluntary context switches
252 ..............................................................................
253 
254 Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
255 ..............................................................................
256  Field    Content
257  size     total program size (pages)            (same as VmSize in status)
258  resident size of memory portions (pages)       (same as VmRSS in status)
259  shared   number of pages that are shared       (i.e. backed by a file)
260  trs      number of pages that are 'code'       (not including libs; broken,
261                                                         includes data segment)
262  lrs      number of pages of library            (always 0 on 2.6)
263  drs      number of pages of data/stack         (including libs; broken,
264                                                         includes library text)
265  dt       number of dirty pages                 (always 0 on 2.6)
266 ..............................................................................
267 
268 
269 Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
270 ..............................................................................
271  Field          Content
272   pid           process id
273   tcomm         filename of the executable
274   state         state (R is running, S is sleeping, D is sleeping in an
275                 uninterruptible wait, Z is zombie, T is traced or stopped)
276   ppid          process id of the parent process
277   pgrp          pgrp of the process
278   sid           session id
279   tty_nr        tty the process uses
280   tty_pgrp      pgrp of the tty
281   flags         task flags
282   min_flt       number of minor faults
283   cmin_flt      number of minor faults with child's
284   maj_flt       number of major faults
285   cmaj_flt      number of major faults with child's
286   utime         user mode jiffies
287   stime         kernel mode jiffies
288   cutime        user mode jiffies with child's
289   cstime        kernel mode jiffies with child's
290   priority      priority level
291   nice          nice level
292   num_threads   number of threads
293   it_real_value (obsolete, always 0)
294   start_time    time the process started after system boot
295   vsize         virtual memory size
296   rss           resident set memory size
297   rsslim        current limit in bytes on the rss
298   start_code    address above which program text can run
299   end_code      address below which program text can run
300   start_stack   address of the start of the main process stack
301   esp           current value of ESP
302   eip           current value of EIP
303   pending       bitmap of pending signals
304   blocked       bitmap of blocked signals
305   sigign        bitmap of ignored signals
306   sigcatch      bitmap of caught signals
307   wchan         address where process went to sleep
308   0             (place holder)
309   0             (place holder)
310   exit_signal   signal to send to parent thread on exit
311   task_cpu      which CPU the task is scheduled on
312   rt_priority   realtime priority
313   policy        scheduling policy (man sched_setscheduler)
314   blkio_ticks   time spent waiting for block IO
315   gtime         guest time of the task in jiffies
316   cgtime        guest time of the task children in jiffies
317   start_data    address above which program data+bss is placed
318   end_data      address below which program data+bss is placed
319   start_brk     address above which program heap can be expanded with brk()
320   arg_start     address above which program command line is placed
321   arg_end       address below which program command line is placed
322   env_start     address above which program environment is placed
323   env_end       address below which program environment is placed
324   exit_code     the thread's exit_code in the form reported by the waitpid system call
325 ..............................................................................
326 
327 The /proc/PID/maps file containing the currently mapped memory regions and
328 their access permissions.
329 
330 The format is:
331 
332 address           perms offset  dev   inode      pathname
333 
334 08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
335 08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
336 0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
337 a7cb1000-a7cb2000 ---p 00000000 00:00 0
338 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
339 a7eb2000-a7eb3000 ---p 00000000 00:00 0
340 a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack:1001]
341 a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
342 a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
343 a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
344 a800b000-a800e000 rw-p 00000000 00:00 0
345 a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
346 a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
347 a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
348 a8024000-a8027000 rw-p 00000000 00:00 0
349 a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
350 a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
351 a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
352 aff35000-aff4a000 rw-p 00000000 00:00 0          [stack]
353 ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
354 
355 where "address" is the address space in the process that it occupies, "perms"
356 is a set of permissions:
357 
358  r = read
359  w = write
360  x = execute
361  s = shared
362  p = private (copy on write)
363 
364 "offset" is the offset into the mapping, "dev" is the device (major:minor), and
365 "inode" is the inode  on that device.  0 indicates that  no inode is associated
366 with the memory region, as the case would be with BSS (uninitialized data).
367 The "pathname" shows the name associated file for this mapping.  If the mapping
368 is not associated with a file:
369 
370  [heap]                   = the heap of the program
371  [stack]                  = the stack of the main process
372  [stack:1001]             = the stack of the thread with tid 1001
373  [vdso]                   = the "virtual dynamic shared object",
374                             the kernel system call handler
375 
376  or if empty, the mapping is anonymous.
377 
378 The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint
379 of the individual tasks of a process. In this file you will see a mapping marked
380 as [stack] if that task sees it as a stack. This is a key difference from the
381 content of /proc/PID/maps, where you will see all mappings that are being used
382 as stack by all of those tasks. Hence, for the example above, the task-level
383 map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this:
384 
385 08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
386 08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
387 0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
388 a7cb1000-a7cb2000 ---p 00000000 00:00 0
389 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
390 a7eb2000-a7eb3000 ---p 00000000 00:00 0
391 a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack]
392 a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
393 a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
394 a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
395 a800b000-a800e000 rw-p 00000000 00:00 0
396 a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
397 a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
398 a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
399 a8024000-a8027000 rw-p 00000000 00:00 0
400 a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
401 a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
402 a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
403 aff35000-aff4a000 rw-p 00000000 00:00 0
404 ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
405 
406 The /proc/PID/smaps is an extension based on maps, showing the memory
407 consumption for each of the process's mappings. For each of mappings there
408 is a series of lines such as the following:
409 
410 08048000-080bc000 r-xp 00000000 03:02 13130      /bin/bash
411 Size:               1084 kB
412 Rss:                 892 kB
413 Pss:                 374 kB
414 Shared_Clean:        892 kB
415 Shared_Dirty:          0 kB
416 Private_Clean:         0 kB
417 Private_Dirty:         0 kB
418 Referenced:          892 kB
419 Anonymous:             0 kB
420 Swap:                  0 kB
421 KernelPageSize:        4 kB
422 MMUPageSize:           4 kB
423 Locked:              374 kB
424 VmFlags: rd ex mr mw me de
425 
426 the first of these lines shows the same information as is displayed for the
427 mapping in /proc/PID/maps.  The remaining lines show the size of the mapping
428 (size), the amount of the mapping that is currently resident in RAM (RSS), the
429 process' proportional share of this mapping (PSS), the number of clean and
430 dirty private pages in the mapping.  Note that even a page which is part of a
431 MAP_SHARED mapping, but has only a single pte mapped, i.e.  is currently used
432 by only one process, is accounted as private and not as shared.  "Referenced"
433 indicates the amount of memory currently marked as referenced or accessed.
434 "Anonymous" shows the amount of memory that does not belong to any file.  Even
435 a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
436 and a page is modified, the file page is replaced by a private anonymous copy.
437 "Swap" shows how much would-be-anonymous memory is also used, but out on
438 swap.
439 
440 "VmFlags" field deserves a separate description. This member represents the kernel
441 flags associated with the particular virtual memory area in two letter encoded
442 manner. The codes are the following:
443     rd  - readable
444     wr  - writeable
445     ex  - executable
446     sh  - shared
447     mr  - may read
448     mw  - may write
449     me  - may execute
450     ms  - may share
451     gd  - stack segment growns down
452     pf  - pure PFN range
453     dw  - disabled write to the mapped file
454     lo  - pages are locked in memory
455     io  - memory mapped I/O area
456     sr  - sequential read advise provided
457     rr  - random read advise provided
458     dc  - do not copy area on fork
459     de  - do not expand area on remapping
460     ac  - area is accountable
461     nr  - swap space is not reserved for the area
462     ht  - area uses huge tlb pages
463     nl  - non-linear mapping
464     ar  - architecture specific flag
465     dd  - do not include area into core dump
466     sd  - soft-dirty flag
467     mm  - mixed map area
468     hg  - huge page advise flag
469     nh  - no-huge page advise flag
470     mg  - mergable advise flag
471 
472 Note that there is no guarantee that every flag and associated mnemonic will
473 be present in all further kernel releases. Things get changed, the flags may
474 be vanished or the reverse -- new added.
475 
476 This file is only present if the CONFIG_MMU kernel configuration option is
477 enabled.
478 
479 The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
480 bits on both physical and virtual pages associated with a process, and the
481 soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details).
482 To clear the bits for all the pages associated with the process
483     > echo 1 > /proc/PID/clear_refs
484 
485 To clear the bits for the anonymous pages associated with the process
486     > echo 2 > /proc/PID/clear_refs
487 
488 To clear the bits for the file mapped pages associated with the process
489     > echo 3 > /proc/PID/clear_refs
490 
491 To clear the soft-dirty bit
492     > echo 4 > /proc/PID/clear_refs
493 
494 To reset the peak resident set size ("high water mark") to the process's
495 current value:
496     > echo 5 > /proc/PID/clear_refs
497 
498 Any other value written to /proc/PID/clear_refs will have no effect.
499 
500 The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
501 using /proc/kpageflags and number of times a page is mapped using
502 /proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
503 
504 The /proc/pid/numa_maps is an extension based on maps, showing the memory
505 locality and binding policy, as well as the memory usage (in pages) of
506 each mapping. The output follows a general format where mapping details get
507 summarized separated by blank spaces, one mapping per each file line:
508 
509 address   policy    mapping details
510 
511 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
512 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
513 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
514 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
515 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
516 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
517 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
518 320698b000 default file=/lib64/libc-2.12.so
519 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
520 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
521 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
522 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
523 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
524 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
525 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
526 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
527 
528 Where:
529 "address" is the starting address for the mapping;
530 "policy" reports the NUMA memory policy set for the mapping (see vm/numa_memory_policy.txt);
531 "mapping details" summarizes mapping data such as mapping type, page usage counters,
532 node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
533 size, in KB, that is backing the mapping up.
534 
535 1.2 Kernel data
536 ---------------
537 
538 Similar to  the  process entries, the kernel data files give information about
539 the running kernel. The files used to obtain this information are contained in
540 /proc and  are  listed  in Table 1-5. Not all of these will be present in your
541 system. It  depends  on the kernel configuration and the loaded modules, which
542 files are there, and which are missing.
543 
544 Table 1-5: Kernel info in /proc
545 ..............................................................................
546  File        Content                                           
547  apm         Advanced power management info                    
548  buddyinfo   Kernel memory allocator information (see text)     (2.5)
549  bus         Directory containing bus specific information     
550  cmdline     Kernel command line                               
551  cpuinfo     Info about the CPU                                
552  devices     Available devices (block and character)           
553  dma         Used DMS channels                                 
554  filesystems Supported filesystems                             
555  driver      Various drivers grouped here, currently rtc (2.4)
556  execdomains Execdomains, related to security                   (2.4)
557  fb          Frame Buffer devices                               (2.4)
558  fs          File system parameters, currently nfs/exports      (2.4)
559  ide         Directory containing info about the IDE subsystem 
560  interrupts  Interrupt usage                                   
561  iomem       Memory map                                         (2.4)
562  ioports     I/O port usage                                    
563  irq         Masks for irq to cpu affinity                      (2.4)(smp?)
564  isapnp      ISA PnP (Plug&Play) Info                           (2.4)
565  kcore       Kernel core image (can be ELF or A.OUT(deprecated in 2.4))   
566  kmsg        Kernel messages                                   
567  ksyms       Kernel symbol table                               
568  loadavg     Load average of last 1, 5 & 15 minutes                
569  locks       Kernel locks                                      
570  meminfo     Memory info                                       
571  misc        Miscellaneous                                     
572  modules     List of loaded modules                            
573  mounts      Mounted filesystems                               
574  net         Networking info (see text)                        
575  pagetypeinfo Additional page allocator information (see text)  (2.5)
576  partitions  Table of partitions known to the system           
577  pci         Deprecated info of PCI bus (new way -> /proc/bus/pci/,
578              decoupled by lspci                                 (2.4)
579  rtc         Real time clock                                   
580  scsi        SCSI info (see text)                              
581  slabinfo    Slab pool info                                    
582  softirqs    softirq usage
583  stat        Overall statistics                                
584  swaps       Swap space utilization                            
585  sys         See chapter 2                                     
586  sysvipc     Info of SysVIPC Resources (msg, sem, shm)          (2.4)
587  tty         Info of tty drivers
588  uptime      Wall clock since boot, combined idle time of all cpus
589  version     Kernel version                                    
590  video       bttv info of video resources                       (2.4)
591  vmallocinfo Show vmalloced areas
592 ..............................................................................
593 
594 You can,  for  example,  check  which interrupts are currently in use and what
595 they are used for by looking in the file /proc/interrupts:
596 
597   > cat /proc/interrupts 
598              CPU0        
599     0:    8728810          XT-PIC  timer 
600     1:        895          XT-PIC  keyboard 
601     2:          0          XT-PIC  cascade 
602     3:     531695          XT-PIC  aha152x 
603     4:    2014133          XT-PIC  serial 
604     5:      44401          XT-PIC  pcnet_cs 
605     8:          2          XT-PIC  rtc 
606    11:          8          XT-PIC  i82365 
607    12:     182918          XT-PIC  PS/2 Mouse 
608    13:          1          XT-PIC  fpu 
609    14:    1232265          XT-PIC  ide0 
610    15:          7          XT-PIC  ide1 
611   NMI:          0 
612 
613 In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
614 output of a SMP machine):
615 
616   > cat /proc/interrupts 
617 
618              CPU0       CPU1       
619     0:    1243498    1214548    IO-APIC-edge  timer
620     1:       8949       8958    IO-APIC-edge  keyboard
621     2:          0          0          XT-PIC  cascade
622     5:      11286      10161    IO-APIC-edge  soundblaster
623     8:          1          0    IO-APIC-edge  rtc
624     9:      27422      27407    IO-APIC-edge  3c503
625    12:     113645     113873    IO-APIC-edge  PS/2 Mouse
626    13:          0          0          XT-PIC  fpu
627    14:      22491      24012    IO-APIC-edge  ide0
628    15:       2183       2415    IO-APIC-edge  ide1
629    17:      30564      30414   IO-APIC-level  eth0
630    18:        177        164   IO-APIC-level  bttv
631   NMI:    2457961    2457959 
632   LOC:    2457882    2457881 
633   ERR:       2155
634 
635 NMI is incremented in this case because every timer interrupt generates a NMI
636 (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
637 
638 LOC is the local interrupt counter of the internal APIC of every CPU.
639 
640 ERR is incremented in the case of errors in the IO-APIC bus (the bus that
641 connects the CPUs in a SMP system. This means that an error has been detected,
642 the IO-APIC automatically retry the transmission, so it should not be a big
643 problem, but you should read the SMP-FAQ.
644 
645 In 2.6.2* /proc/interrupts was expanded again.  This time the goal was for
646 /proc/interrupts to display every IRQ vector in use by the system, not
647 just those considered 'most important'.  The new vectors are:
648 
649   THR -- interrupt raised when a machine check threshold counter
650   (typically counting ECC corrected errors of memory or cache) exceeds
651   a configurable threshold.  Only available on some systems.
652 
653   TRM -- a thermal event interrupt occurs when a temperature threshold
654   has been exceeded for the CPU.  This interrupt may also be generated
655   when the temperature drops back to normal.
656 
657   SPU -- a spurious interrupt is some interrupt that was raised then lowered
658   by some IO device before it could be fully processed by the APIC.  Hence
659   the APIC sees the interrupt but does not know what device it came from.
660   For this case the APIC will generate the interrupt with a IRQ vector
661   of 0xff. This might also be generated by chipset bugs.
662 
663   RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
664   sent from one CPU to another per the needs of the OS.  Typically,
665   their statistics are used by kernel developers and interested users to
666   determine the occurrence of interrupts of the given type.
667 
668 The above IRQ vectors are displayed only when relevant.  For example,
669 the threshold vector does not exist on x86_64 platforms.  Others are
670 suppressed when the system is a uniprocessor.  As of this writing, only
671 i386 and x86_64 platforms support the new IRQ vector displays.
672 
673 Of some interest is the introduction of the /proc/irq directory to 2.4.
674 It could be used to set IRQ to CPU affinity, this means that you can "hook" an
675 IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
676 irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
677 prof_cpu_mask.
678 
679 For example 
680   > ls /proc/irq/
681   0  10  12  14  16  18  2  4  6  8  prof_cpu_mask
682   1  11  13  15  17  19  3  5  7  9  default_smp_affinity
683   > ls /proc/irq/0/
684   smp_affinity
685 
686 smp_affinity is a bitmask, in which you can specify which CPUs can handle the
687 IRQ, you can set it by doing:
688 
689   > echo 1 > /proc/irq/10/smp_affinity
690 
691 This means that only the first CPU will handle the IRQ, but you can also echo
692 5 which means that only the first and fourth CPU can handle the IRQ.
693 
694 The contents of each smp_affinity file is the same by default:
695 
696   > cat /proc/irq/0/smp_affinity
697   ffffffff
698 
699 There is an alternate interface, smp_affinity_list which allows specifying
700 a cpu range instead of a bitmask:
701 
702   > cat /proc/irq/0/smp_affinity_list
703   1024-1031
704 
705 The default_smp_affinity mask applies to all non-active IRQs, which are the
706 IRQs which have not yet been allocated/activated, and hence which lack a
707 /proc/irq/[0-9]* directory.
708 
709 The node file on an SMP system shows the node to which the device using the IRQ
710 reports itself as being attached. This hardware locality information does not
711 include information about any possible driver locality preference.
712 
713 prof_cpu_mask specifies which CPUs are to be profiled by the system wide
714 profiler. Default value is ffffffff (all cpus if there are only 32 of them).
715 
716 The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
717 between all the CPUs which are allowed to handle it. As usual the kernel has
718 more info than you and does a better job than you, so the defaults are the
719 best choice for almost everyone.  [Note this applies only to those IO-APIC's
720 that support "Round Robin" interrupt distribution.]
721 
722 There are  three  more  important subdirectories in /proc: net, scsi, and sys.
723 The general  rule  is  that  the  contents,  or  even  the  existence of these
724 directories, depend  on your kernel configuration. If SCSI is not enabled, the
725 directory scsi  may  not  exist. The same is true with the net, which is there
726 only when networking support is present in the running kernel.
727 
728 The slabinfo  file  gives  information  about  memory usage at the slab level.
729 Linux uses  slab  pools for memory management above page level in version 2.2.
730 Commonly used  objects  have  their  own  slab  pool (such as network buffers,
731 directory cache, and so on).
732 
733 ..............................................................................
734 
735 > cat /proc/buddyinfo
736 
737 Node 0, zone      DMA      0      4      5      4      4      3 ...
738 Node 0, zone   Normal      1      0      0      1    101      8 ...
739 Node 0, zone  HighMem      2      0      0      1      1      0 ...
740 
741 External fragmentation is a problem under some workloads, and buddyinfo is a
742 useful tool for helping diagnose these problems.  Buddyinfo will give you a 
743 clue as to how big an area you can safely allocate, or why a previous
744 allocation failed.
745 
746 Each column represents the number of pages of a certain order which are 
747 available.  In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 
748 ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 
749 available in ZONE_NORMAL, etc... 
750 
751 More information relevant to external fragmentation can be found in
752 pagetypeinfo.
753 
754 > cat /proc/pagetypeinfo
755 Page block order: 9
756 Pages per block:  512
757 
758 Free pages count per migrate type at order       0      1      2      3      4      5      6      7      8      9     10
759 Node    0, zone      DMA, type    Unmovable      0      0      0      1      1      1      1      1      1      1      0
760 Node    0, zone      DMA, type  Reclaimable      0      0      0      0      0      0      0      0      0      0      0
761 Node    0, zone      DMA, type      Movable      1      1      2      1      2      1      1      0      1      0      2
762 Node    0, zone      DMA, type      Reserve      0      0      0      0      0      0      0      0      0      1      0
763 Node    0, zone      DMA, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
764 Node    0, zone    DMA32, type    Unmovable    103     54     77      1      1      1     11      8      7      1      9
765 Node    0, zone    DMA32, type  Reclaimable      0      0      2      1      0      0      0      0      1      0      0
766 Node    0, zone    DMA32, type      Movable    169    152    113     91     77     54     39     13      6      1    452
767 Node    0, zone    DMA32, type      Reserve      1      2      2      2      2      0      1      1      1      1      0
768 Node    0, zone    DMA32, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
769 
770 Number of blocks type     Unmovable  Reclaimable      Movable      Reserve      Isolate
771 Node 0, zone      DMA            2            0            5            1            0
772 Node 0, zone    DMA32           41            6          967            2            0
773 
774 Fragmentation avoidance in the kernel works by grouping pages of different
775 migrate types into the same contiguous regions of memory called page blocks.
776 A page block is typically the size of the default hugepage size e.g. 2MB on
777 X86-64. By keeping pages grouped based on their ability to move, the kernel
778 can reclaim pages within a page block to satisfy a high-order allocation.
779 
780 The pagetypinfo begins with information on the size of a page block. It
781 then gives the same type of information as buddyinfo except broken down
782 by migrate-type and finishes with details on how many page blocks of each
783 type exist.
784 
785 If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
786 from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
787 make an estimate of the likely number of huge pages that can be allocated
788 at a given point in time. All the "Movable" blocks should be allocatable
789 unless memory has been mlock()'d. Some of the Reclaimable blocks should
790 also be allocatable although a lot of filesystem metadata may have to be
791 reclaimed to achieve this.
792 
793 ..............................................................................
794 
795 meminfo:
796 
797 Provides information about distribution and utilization of memory.  This
798 varies by architecture and compile options.  The following is from a
799 16GB PIII, which has highmem enabled.  You may not have all of these fields.
800 
801 > cat /proc/meminfo
802 
803 The "Locked" indicates whether the mapping is locked in memory or not.
804 
805 
806 MemTotal:     16344972 kB
807 MemFree:      13634064 kB
808 MemAvailable: 14836172 kB
809 Buffers:          3656 kB
810 Cached:        1195708 kB
811 SwapCached:          0 kB
812 Active:         891636 kB
813 Inactive:      1077224 kB
814 HighTotal:    15597528 kB
815 HighFree:     13629632 kB
816 LowTotal:       747444 kB
817 LowFree:          4432 kB
818 SwapTotal:           0 kB
819 SwapFree:            0 kB
820 Dirty:             968 kB
821 Writeback:           0 kB
822 AnonPages:      861800 kB
823 Mapped:         280372 kB
824 Slab:           284364 kB
825 SReclaimable:   159856 kB
826 SUnreclaim:     124508 kB
827 PageTables:      24448 kB
828 NFS_Unstable:        0 kB
829 Bounce:              0 kB
830 WritebackTmp:        0 kB
831 CommitLimit:   7669796 kB
832 Committed_AS:   100056 kB
833 VmallocTotal:   112216 kB
834 VmallocUsed:       428 kB
835 VmallocChunk:   111088 kB
836 AnonHugePages:   49152 kB
837 
838     MemTotal: Total usable ram (i.e. physical ram minus a few reserved
839               bits and the kernel binary code)
840      MemFree: The sum of LowFree+HighFree
841 MemAvailable: An estimate of how much memory is available for starting new
842               applications, without swapping. Calculated from MemFree,
843               SReclaimable, the size of the file LRU lists, and the low
844               watermarks in each zone.
845               The estimate takes into account that the system needs some
846               page cache to function well, and that not all reclaimable
847               slab will be reclaimable, due to items being in use. The
848               impact of those factors will vary from system to system.
849      Buffers: Relatively temporary storage for raw disk blocks
850               shouldn't get tremendously large (20MB or so)
851       Cached: in-memory cache for files read from the disk (the
852               pagecache).  Doesn't include SwapCached
853   SwapCached: Memory that once was swapped out, is swapped back in but
854               still also is in the swapfile (if memory is needed it
855               doesn't need to be swapped out AGAIN because it is already
856               in the swapfile. This saves I/O)
857       Active: Memory that has been used more recently and usually not
858               reclaimed unless absolutely necessary.
859     Inactive: Memory which has been less recently used.  It is more
860               eligible to be reclaimed for other purposes
861    HighTotal:
862     HighFree: Highmem is all memory above ~860MB of physical memory
863               Highmem areas are for use by userspace programs, or
864               for the pagecache.  The kernel must use tricks to access
865               this memory, making it slower to access than lowmem.
866     LowTotal:
867      LowFree: Lowmem is memory which can be used for everything that
868               highmem can be used for, but it is also available for the
869               kernel's use for its own data structures.  Among many
870               other things, it is where everything from the Slab is
871               allocated.  Bad things happen when you're out of lowmem.
872    SwapTotal: total amount of swap space available
873     SwapFree: Memory which has been evicted from RAM, and is temporarily
874               on the disk
875        Dirty: Memory which is waiting to get written back to the disk
876    Writeback: Memory which is actively being written back to the disk
877    AnonPages: Non-file backed pages mapped into userspace page tables
878 AnonHugePages: Non-file backed huge pages mapped into userspace page tables
879       Mapped: files which have been mmaped, such as libraries
880         Slab: in-kernel data structures cache
881 SReclaimable: Part of Slab, that might be reclaimed, such as caches
882   SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
883   PageTables: amount of memory dedicated to the lowest level of page
884               tables.
885 NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
886               storage
887       Bounce: Memory used for block device "bounce buffers"
888 WritebackTmp: Memory used by FUSE for temporary writeback buffers
889  CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
890               this is the total amount of  memory currently available to
891               be allocated on the system. This limit is only adhered to
892               if strict overcommit accounting is enabled (mode 2 in
893               'vm.overcommit_memory').
894               The CommitLimit is calculated with the following formula:
895               CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
896                              overcommit_ratio / 100 + [total swap pages]
897               For example, on a system with 1G of physical RAM and 7G
898               of swap with a `vm.overcommit_ratio` of 30 it would
899               yield a CommitLimit of 7.3G.
900               For more details, see the memory overcommit documentation
901               in vm/overcommit-accounting.
902 Committed_AS: The amount of memory presently allocated on the system.
903               The committed memory is a sum of all of the memory which
904               has been allocated by processes, even if it has not been
905               "used" by them as of yet. A process which malloc()'s 1G
906               of memory, but only touches 300M of it will show up as
907               using 1G. This 1G is memory which has been "committed" to
908               by the VM and can be used at any time by the allocating
909               application. With strict overcommit enabled on the system
910               (mode 2 in 'vm.overcommit_memory'),allocations which would
911               exceed the CommitLimit (detailed above) will not be permitted.
912               This is useful if one needs to guarantee that processes will
913               not fail due to lack of memory once that memory has been
914               successfully allocated.
915 VmallocTotal: total size of vmalloc memory area
916  VmallocUsed: amount of vmalloc area which is used
917 VmallocChunk: largest contiguous block of vmalloc area which is free
918 
919 ..............................................................................
920 
921 vmallocinfo:
922 
923 Provides information about vmalloced/vmaped areas. One line per area,
924 containing the virtual address range of the area, size in bytes,
925 caller information of the creator, and optional information depending
926 on the kind of area :
927 
928  pages=nr    number of pages
929  phys=addr   if a physical address was specified
930  ioremap     I/O mapping (ioremap() and friends)
931  vmalloc     vmalloc() area
932  vmap        vmap()ed pages
933  user        VM_USERMAP area
934  vpages      buffer for pages pointers was vmalloced (huge area)
935  N<node>=nr  (Only on NUMA kernels)
936              Number of pages allocated on memory node <node>
937 
938 > cat /proc/vmallocinfo
939 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
940   /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
941 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
942   /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
943 0xffffc20000302000-0xffffc20000304000    8192 acpi_tb_verify_table+0x21/0x4f...
944   phys=7fee8000 ioremap
945 0xffffc20000304000-0xffffc20000307000   12288 acpi_tb_verify_table+0x21/0x4f...
946   phys=7fee7000 ioremap
947 0xffffc2000031d000-0xffffc2000031f000    8192 init_vdso_vars+0x112/0x210
948 0xffffc2000031f000-0xffffc2000032b000   49152 cramfs_uncompress_init+0x2e ...
949   /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
950 0xffffc2000033a000-0xffffc2000033d000   12288 sys_swapon+0x640/0xac0      ...
951   pages=2 vmalloc N1=2
952 0xffffc20000347000-0xffffc2000034c000   20480 xt_alloc_table_info+0xfe ...
953   /0x130 [x_tables] pages=4 vmalloc N0=4
954 0xffffffffa0000000-0xffffffffa000f000   61440 sys_init_module+0xc27/0x1d00 ...
955    pages=14 vmalloc N2=14
956 0xffffffffa000f000-0xffffffffa0014000   20480 sys_init_module+0xc27/0x1d00 ...
957    pages=4 vmalloc N1=4
958 0xffffffffa0014000-0xffffffffa0017000   12288 sys_init_module+0xc27/0x1d00 ...
959    pages=2 vmalloc N1=2
960 0xffffffffa0017000-0xffffffffa0022000   45056 sys_init_module+0xc27/0x1d00 ...
961    pages=10 vmalloc N0=10
962 
963 ..............................................................................
964 
965 softirqs:
966 
967 Provides counts of softirq handlers serviced since boot time, for each cpu.
968 
969 > cat /proc/softirqs
970                 CPU0       CPU1       CPU2       CPU3
971       HI:          0          0          0          0
972    TIMER:      27166      27120      27097      27034
973   NET_TX:          0          0          0         17
974   NET_RX:         42          0          0         39
975    BLOCK:          0          0        107       1121
976  TASKLET:          0          0          0        290
977    SCHED:      27035      26983      26971      26746
978  HRTIMER:          0          0          0          0
979      RCU:       1678       1769       2178       2250
980 
981 
982 1.3 IDE devices in /proc/ide
983 ----------------------------
984 
985 The subdirectory /proc/ide contains information about all IDE devices of which
986 the kernel  is  aware.  There is one subdirectory for each IDE controller, the
987 file drivers  and a link for each IDE device, pointing to the device directory
988 in the controller specific subtree.
989 
990 The file  drivers  contains general information about the drivers used for the
991 IDE devices:
992 
993   > cat /proc/ide/drivers
994   ide-cdrom version 4.53
995   ide-disk version 1.08
996 
997 More detailed  information  can  be  found  in  the  controller  specific
998 subdirectories. These  are  named  ide0,  ide1  and  so  on.  Each  of  these
999 directories contains the files shown in table 1-6.
1000 
1001 
1002 Table 1-6: IDE controller info in  /proc/ide/ide?
1003 ..............................................................................
1004  File    Content                                 
1005  channel IDE channel (0 or 1)                    
1006  config  Configuration (only for PCI/IDE bridge) 
1007  mate    Mate name                               
1008  model   Type/Chipset of IDE controller          
1009 ..............................................................................
1010 
1011 Each device  connected  to  a  controller  has  a separate subdirectory in the
1012 controllers directory.  The  files  listed in table 1-7 are contained in these
1013 directories.
1014 
1015 
1016 Table 1-7: IDE device information
1017 ..............................................................................
1018  File             Content                                    
1019  cache            The cache                                  
1020  capacity         Capacity of the medium (in 512Byte blocks) 
1021  driver           driver and version                         
1022  geometry         physical and logical geometry              
1023  identify         device identify block                      
1024  media            media type                                 
1025  model            device identifier                          
1026  settings         device setup                               
1027  smart_thresholds IDE disk management thresholds             
1028  smart_values     IDE disk management values                 
1029 ..............................................................................
1030 
1031 The most  interesting  file is settings. This file contains a nice overview of
1032 the drive parameters:
1033 
1034   # cat /proc/ide/ide0/hda/settings 
1035   name                    value           min             max             mode 
1036   ----                    -----           ---             ---             ---- 
1037   bios_cyl                526             0               65535           rw 
1038   bios_head               255             0               255             rw 
1039   bios_sect               63              0               63              rw 
1040   breada_readahead        4               0               127             rw 
1041   bswap                   0               0               1               r 
1042   file_readahead          72              0               2097151         rw 
1043   io_32bit                0               0               3               rw 
1044   keepsettings            0               0               1               rw 
1045   max_kb_per_request      122             1               127             rw 
1046   multcount               0               0               8               rw 
1047   nice1                   1               0               1               rw 
1048   nowerr                  0               0               1               rw 
1049   pio_mode                write-only      0               255             w 
1050   slow                    0               0               1               rw 
1051   unmaskirq               0               0               1               rw 
1052   using_dma               0               0               1               rw 
1053 
1054 
1055 1.4 Networking info in /proc/net
1056 --------------------------------
1057 
1058 The subdirectory  /proc/net  follows  the  usual  pattern. Table 1-8 shows the
1059 additional values  you  get  for  IP  version 6 if you configure the kernel to
1060 support this. Table 1-9 lists the files and their meaning.
1061 
1062 
1063 Table 1-8: IPv6 info in /proc/net
1064 ..............................................................................
1065  File       Content                                               
1066  udp6       UDP sockets (IPv6)                                    
1067  tcp6       TCP sockets (IPv6)                                    
1068  raw6       Raw device statistics (IPv6)                          
1069  igmp6      IP multicast addresses, which this host joined (IPv6) 
1070  if_inet6   List of IPv6 interface addresses                      
1071  ipv6_route Kernel routing table for IPv6                         
1072  rt6_stats  Global IPv6 routing tables statistics                 
1073  sockstat6  Socket statistics (IPv6)                              
1074  snmp6      Snmp data (IPv6)                                      
1075 ..............................................................................
1076 
1077 
1078 Table 1-9: Network info in /proc/net
1079 ..............................................................................
1080  File          Content                                                         
1081  arp           Kernel  ARP table                                               
1082  dev           network devices with statistics                                 
1083  dev_mcast     the Layer2 multicast groups a device is listening too
1084                (interface index, label, number of references, number of bound
1085                addresses). 
1086  dev_stat      network device status                                           
1087  ip_fwchains   Firewall chain linkage                                          
1088  ip_fwnames    Firewall chain names                                            
1089  ip_masq       Directory containing the masquerading tables                    
1090  ip_masquerade Major masquerading table                                        
1091  netstat       Network statistics                                              
1092  raw           raw device statistics                                           
1093  route         Kernel routing table                                            
1094  rpc           Directory containing rpc info                                   
1095  rt_cache      Routing cache                                                   
1096  snmp          SNMP data                                                       
1097  sockstat      Socket statistics                                               
1098  tcp           TCP  sockets                                                    
1099  udp           UDP sockets                                                     
1100  unix          UNIX domain sockets                                             
1101  wireless      Wireless interface data (Wavelan etc)                           
1102  igmp          IP multicast addresses, which this host joined                  
1103  psched        Global packet scheduler parameters.                             
1104  netlink       List of PF_NETLINK sockets                                      
1105  ip_mr_vifs    List of multicast virtual interfaces                            
1106  ip_mr_cache   List of multicast routing cache                                 
1107 ..............................................................................
1108 
1109 You can  use  this  information  to see which network devices are available in
1110 your system and how much traffic was routed over those devices:
1111 
1112   > cat /proc/net/dev 
1113   Inter-|Receive                                                   |[... 
1114    face |bytes    packets errs drop fifo frame compressed multicast|[... 
1115       lo:  908188   5596     0    0    0     0          0         0 [...         
1116     ppp0:15475140  20721   410    0    0   410          0         0 [...  
1117     eth0:  614530   7085     0    0    0     0          0         1 [... 
1118    
1119   ...] Transmit 
1120   ...] bytes    packets errs drop fifo colls carrier compressed 
1121   ...]  908188     5596    0    0    0     0       0          0 
1122   ...] 1375103    17405    0    0    0     0       0          0 
1123   ...] 1703981     5535    0    0    0     3       0          0 
1124 
1125 In addition, each Channel Bond interface has its own directory.  For
1126 example, the bond0 device will have a directory called /proc/net/bond0/.
1127 It will contain information that is specific to that bond, such as the
1128 current slaves of the bond, the link status of the slaves, and how
1129 many times the slaves link has failed.
1130 
1131 1.5 SCSI info
1132 -------------
1133 
1134 If you  have  a  SCSI  host adapter in your system, you'll find a subdirectory
1135 named after  the driver for this adapter in /proc/scsi. You'll also see a list
1136 of all recognized SCSI devices in /proc/scsi:
1137 
1138   >cat /proc/scsi/scsi 
1139   Attached devices: 
1140   Host: scsi0 Channel: 00 Id: 00 Lun: 00 
1141     Vendor: IBM      Model: DGHS09U          Rev: 03E0 
1142     Type:   Direct-Access                    ANSI SCSI revision: 03 
1143   Host: scsi0 Channel: 00 Id: 06 Lun: 00 
1144     Vendor: PIONEER  Model: CD-ROM DR-U06S   Rev: 1.04 
1145     Type:   CD-ROM                           ANSI SCSI revision: 02 
1146 
1147 
1148 The directory  named  after  the driver has one file for each adapter found in
1149 the system.  These  files  contain information about the controller, including
1150 the used  IRQ  and  the  IO  address range. The amount of information shown is
1151 dependent on  the adapter you use. The example shows the output for an Adaptec
1152 AHA-2940 SCSI adapter:
1153 
1154   > cat /proc/scsi/aic7xxx/0 
1155    
1156   Adaptec AIC7xxx driver version: 5.1.19/3.2.4 
1157   Compile Options: 
1158     TCQ Enabled By Default : Disabled 
1159     AIC7XXX_PROC_STATS     : Disabled 
1160     AIC7XXX_RESET_DELAY    : 5 
1161   Adapter Configuration: 
1162              SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 
1163                              Ultra Wide Controller 
1164       PCI MMAPed I/O Base: 0xeb001000 
1165    Adapter SEEPROM Config: SEEPROM found and used. 
1166         Adaptec SCSI BIOS: Enabled 
1167                       IRQ: 10 
1168                      SCBs: Active 0, Max Active 2, 
1169                            Allocated 15, HW 16, Page 255 
1170                Interrupts: 160328 
1171         BIOS Control Word: 0x18b6 
1172      Adapter Control Word: 0x005b 
1173      Extended Translation: Enabled 
1174   Disconnect Enable Flags: 0xffff 
1175        Ultra Enable Flags: 0x0001 
1176    Tag Queue Enable Flags: 0x0000 
1177   Ordered Queue Tag Flags: 0x0000 
1178   Default Tag Queue Depth: 8 
1179       Tagged Queue By Device array for aic7xxx host instance 0: 
1180         {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 
1181       Actual queue depth per device for aic7xxx host instance 0: 
1182         {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 
1183   Statistics: 
1184   (scsi0:0:0:0) 
1185     Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 
1186     Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 
1187     Total transfers 160151 (74577 reads and 85574 writes) 
1188   (scsi0:0:6:0) 
1189     Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 
1190     Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 
1191     Total transfers 0 (0 reads and 0 writes) 
1192 
1193 
1194 1.6 Parallel port info in /proc/parport
1195 ---------------------------------------
1196 
1197 The directory  /proc/parport  contains information about the parallel ports of
1198 your system.  It  has  one  subdirectory  for  each port, named after the port
1199 number (0,1,2,...).
1200 
1201 These directories contain the four files shown in Table 1-10.
1202 
1203 
1204 Table 1-10: Files in /proc/parport
1205 ..............................................................................
1206  File      Content                                                             
1207  autoprobe Any IEEE-1284 device ID information that has been acquired.         
1208  devices   list of the device drivers using that port. A + will appear by the
1209            name of the device currently using the port (it might not appear
1210            against any). 
1211  hardware  Parallel port's base address, IRQ line and DMA channel.             
1212  irq       IRQ that parport is using for that port. This is in a separate
1213            file to allow you to alter it by writing a new value in (IRQ
1214            number or none). 
1215 ..............................................................................
1216 
1217 1.7 TTY info in /proc/tty
1218 -------------------------
1219 
1220 Information about  the  available  and actually used tty's can be found in the
1221 directory /proc/tty.You'll  find  entries  for drivers and line disciplines in
1222 this directory, as shown in Table 1-11.
1223 
1224 
1225 Table 1-11: Files in /proc/tty
1226 ..............................................................................
1227  File          Content                                        
1228  drivers       list of drivers and their usage                
1229  ldiscs        registered line disciplines                    
1230  driver/serial usage statistic and status of single tty lines 
1231 ..............................................................................
1232 
1233 To see  which  tty's  are  currently in use, you can simply look into the file
1234 /proc/tty/drivers:
1235 
1236   > cat /proc/tty/drivers 
1237   pty_slave            /dev/pts      136   0-255 pty:slave 
1238   pty_master           /dev/ptm      128   0-255 pty:master 
1239   pty_slave            /dev/ttyp       3   0-255 pty:slave 
1240   pty_master           /dev/pty        2   0-255 pty:master 
1241   serial               /dev/cua        5   64-67 serial:callout 
1242   serial               /dev/ttyS       4   64-67 serial 
1243   /dev/tty0            /dev/tty0       4       0 system:vtmaster 
1244   /dev/ptmx            /dev/ptmx       5       2 system 
1245   /dev/console         /dev/console    5       1 system:console 
1246   /dev/tty             /dev/tty        5       0 system:/dev/tty 
1247   unknown              /dev/tty        4    1-63 console 
1248 
1249 
1250 1.8 Miscellaneous kernel statistics in /proc/stat
1251 -------------------------------------------------
1252 
1253 Various pieces   of  information about  kernel activity  are  available in the
1254 /proc/stat file.  All  of  the numbers reported  in  this file are  aggregates
1255 since the system first booted.  For a quick look, simply cat the file:
1256 
1257   > cat /proc/stat
1258   cpu  2255 34 2290 22625563 6290 127 456 0 0
1259   cpu0 1132 34 1441 11311718 3675 127 438 0 0
1260   cpu1 1123 0 849 11313845 2614 0 18 0 0
1261   intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1262   ctxt 1990473
1263   btime 1062191376
1264   processes 2915
1265   procs_running 1
1266   procs_blocked 0
1267   softirq 183433 0 21755 12 39 1137 231 21459 2263
1268 
1269 The very first  "cpu" line aggregates the  numbers in all  of the other "cpuN"
1270 lines.  These numbers identify the amount of time the CPU has spent performing
1271 different kinds of work.  Time units are in USER_HZ (typically hundredths of a
1272 second).  The meanings of the columns are as follows, from left to right:
1273 
1274 - user: normal processes executing in user mode
1275 - nice: niced processes executing in user mode
1276 - system: processes executing in kernel mode
1277 - idle: twiddling thumbs
1278 - iowait: waiting for I/O to complete
1279 - irq: servicing interrupts
1280 - softirq: servicing softirqs
1281 - steal: involuntary wait
1282 - guest: running a normal guest
1283 - guest_nice: running a niced guest
1284 
1285 The "intr" line gives counts of interrupts  serviced since boot time, for each
1286 of the  possible system interrupts.   The first  column  is the  total of  all
1287 interrupts serviced  including  unnumbered  architecture specific  interrupts;
1288 each  subsequent column is the  total for that particular numbered interrupt.
1289 Unnumbered interrupts are not shown, only summed into the total.
1290 
1291 The "ctxt" line gives the total number of context switches across all CPUs.
1292 
1293 The "btime" line gives  the time at which the  system booted, in seconds since
1294 the Unix epoch.
1295 
1296 The "processes" line gives the number  of processes and threads created, which
1297 includes (but  is not limited  to) those  created by  calls to the  fork() and
1298 clone() system calls.
1299 
1300 The "procs_running" line gives the total number of threads that are
1301 running or ready to run (i.e., the total number of runnable threads).
1302 
1303 The   "procs_blocked" line gives  the  number of  processes currently blocked,
1304 waiting for I/O to complete.
1305 
1306 The "softirq" line gives counts of softirqs serviced since boot time, for each
1307 of the possible system softirqs. The first column is the total of all
1308 softirqs serviced; each subsequent column is the total for that particular
1309 softirq.
1310 
1311 
1312 1.9 Ext4 file system parameters
1313 -------------------------------
1314 
1315 Information about mounted ext4 file systems can be found in
1316 /proc/fs/ext4.  Each mounted filesystem will have a directory in
1317 /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1318 /proc/fs/ext4/dm-0).   The files in each per-device directory are shown
1319 in Table 1-12, below.
1320 
1321 Table 1-12: Files in /proc/fs/ext4/<devname>
1322 ..............................................................................
1323  File            Content                                        
1324  mb_groups       details of multiblock allocator buddy cache of free blocks
1325 ..............................................................................
1326 
1327 2.0 /proc/consoles
1328 ------------------
1329 Shows registered system console lines.
1330 
1331 To see which character device lines are currently used for the system console
1332 /dev/console, you may simply look into the file /proc/consoles:
1333 
1334   > cat /proc/consoles
1335   tty0                 -WU (ECp)       4:7
1336   ttyS0                -W- (Ep)        4:64
1337 
1338 The columns are:
1339 
1340   device               name of the device
1341   operations           R = can do read operations
1342                        W = can do write operations
1343                        U = can do unblank
1344   flags                E = it is enabled
1345                        C = it is preferred console
1346                        B = it is primary boot console
1347                        p = it is used for printk buffer
1348                        b = it is not a TTY but a Braille device
1349                        a = it is safe to use when cpu is offline
1350   major:minor          major and minor number of the device separated by a colon
1351 
1352 ------------------------------------------------------------------------------
1353 Summary
1354 ------------------------------------------------------------------------------
1355 The /proc file system serves information about the running system. It not only
1356 allows access to process data but also allows you to request the kernel status
1357 by reading files in the hierarchy.
1358 
1359 The directory  structure  of /proc reflects the types of information and makes
1360 it easy, if not obvious, where to look for specific data.
1361 ------------------------------------------------------------------------------
1362 
1363 ------------------------------------------------------------------------------
1364 CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1365 ------------------------------------------------------------------------------
1366 
1367 ------------------------------------------------------------------------------
1368 In This Chapter
1369 ------------------------------------------------------------------------------
1370 * Modifying kernel parameters by writing into files found in /proc/sys
1371 * Exploring the files which modify certain parameters
1372 * Review of the /proc/sys file tree
1373 ------------------------------------------------------------------------------
1374 
1375 
1376 A very  interesting part of /proc is the directory /proc/sys. This is not only
1377 a source  of  information,  it also allows you to change parameters within the
1378 kernel. Be  very  careful  when attempting this. You can optimize your system,
1379 but you  can  also  cause  it  to  crash.  Never  alter kernel parameters on a
1380 production system.  Set  up  a  development machine and test to make sure that
1381 everything works  the  way  you want it to. You may have no alternative but to
1382 reboot the machine once an error has been made.
1383 
1384 To change  a  value,  simply  echo  the new value into the file. An example is
1385 given below  in the section on the file system data. You need to be root to do
1386 this. You  can  create  your  own  boot script to perform this every time your
1387 system boots.
1388 
1389 The files  in /proc/sys can be used to fine tune and monitor miscellaneous and
1390 general things  in  the operation of the Linux kernel. Since some of the files
1391 can inadvertently  disrupt  your  system,  it  is  advisable  to  read  both
1392 documentation and  source  before actually making adjustments. In any case, be
1393 very careful  when  writing  to  any  of these files. The entries in /proc may
1394 change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1395 review the kernel documentation in the directory /usr/src/linux/Documentation.
1396 This chapter  is  heavily  based  on the documentation included in the pre 2.2
1397 kernels, and became part of it in version 2.2.1 of the Linux kernel.
1398 
1399 Please see: Documentation/sysctl/ directory for descriptions of these
1400 entries.
1401 
1402 ------------------------------------------------------------------------------
1403 Summary
1404 ------------------------------------------------------------------------------
1405 Certain aspects  of  kernel  behavior  can be modified at runtime, without the
1406 need to  recompile  the kernel, or even to reboot the system. The files in the
1407 /proc/sys tree  can  not only be read, but also modified. You can use the echo
1408 command to write value into these files, thereby changing the default settings
1409 of the kernel.
1410 ------------------------------------------------------------------------------
1411 
1412 ------------------------------------------------------------------------------
1413 CHAPTER 3: PER-PROCESS PARAMETERS
1414 ------------------------------------------------------------------------------
1415 
1416 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1417 --------------------------------------------------------------------------------
1418 
1419 These file can be used to adjust the badness heuristic used to select which
1420 process gets killed in out of memory conditions.
1421 
1422 The badness heuristic assigns a value to each candidate task ranging from 0
1423 (never kill) to 1000 (always kill) to determine which process is targeted.  The
1424 units are roughly a proportion along that range of allowed memory the process
1425 may allocate from based on an estimation of its current memory and swap use.
1426 For example, if a task is using all allowed memory, its badness score will be
1427 1000.  If it is using half of its allowed memory, its score will be 500.
1428 
1429 There is an additional factor included in the badness score: the current memory
1430 and swap usage is discounted by 3% for root processes.
1431 
1432 The amount of "allowed" memory depends on the context in which the oom killer
1433 was called.  If it is due to the memory assigned to the allocating task's cpuset
1434 being exhausted, the allowed memory represents the set of mems assigned to that
1435 cpuset.  If it is due to a mempolicy's node(s) being exhausted, the allowed
1436 memory represents the set of mempolicy nodes.  If it is due to a memory
1437 limit (or swap limit) being reached, the allowed memory is that configured
1438 limit.  Finally, if it is due to the entire system being out of memory, the
1439 allowed memory represents all allocatable resources.
1440 
1441 The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1442 is used to determine which task to kill.  Acceptable values range from -1000
1443 (OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX).  This allows userspace to
1444 polarize the preference for oom killing either by always preferring a certain
1445 task or completely disabling it.  The lowest possible value, -1000, is
1446 equivalent to disabling oom killing entirely for that task since it will always
1447 report a badness score of 0.
1448 
1449 Consequently, it is very simple for userspace to define the amount of memory to
1450 consider for each task.  Setting a /proc/<pid>/oom_score_adj value of +500, for
1451 example, is roughly equivalent to allowing the remainder of tasks sharing the
1452 same system, cpuset, mempolicy, or memory controller resources to use at least
1453 50% more memory.  A value of -500, on the other hand, would be roughly
1454 equivalent to discounting 50% of the task's allowed memory from being considered
1455 as scoring against the task.
1456 
1457 For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1458 be used to tune the badness score.  Its acceptable values range from -16
1459 (OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1460 (OOM_DISABLE) to disable oom killing entirely for that task.  Its value is
1461 scaled linearly with /proc/<pid>/oom_score_adj.
1462 
1463 The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1464 value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1465 requires CAP_SYS_RESOURCE.
1466 
1467 Caveat: when a parent task is selected, the oom killer will sacrifice any first
1468 generation children with separate address spaces instead, if possible.  This
1469 avoids servers and important system daemons from being killed and loses the
1470 minimal amount of work.
1471 
1472 
1473 3.2 /proc/<pid>/oom_score - Display current oom-killer score
1474 -------------------------------------------------------------
1475 
1476 This file can be used to check the current score used by the oom-killer is for
1477 any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1478 process should be killed in an out-of-memory situation.
1479 
1480 
1481 3.3  /proc/<pid>/io - Display the IO accounting fields
1482 -------------------------------------------------------
1483 
1484 This file contains IO statistics for each running process
1485 
1486 Example
1487 -------
1488 
1489 test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1490 [1] 3828
1491 
1492 test:/tmp # cat /proc/3828/io
1493 rchar: 323934931
1494 wchar: 323929600
1495 syscr: 632687
1496 syscw: 632675
1497 read_bytes: 0
1498 write_bytes: 323932160
1499 cancelled_write_bytes: 0
1500 
1501 
1502 Description
1503 -----------
1504 
1505 rchar
1506 -----
1507 
1508 I/O counter: chars read
1509 The number of bytes which this task has caused to be read from storage. This
1510 is simply the sum of bytes which this process passed to read() and pread().
1511 It includes things like tty IO and it is unaffected by whether or not actual
1512 physical disk IO was required (the read might have been satisfied from
1513 pagecache)
1514 
1515 
1516 wchar
1517 -----
1518 
1519 I/O counter: chars written
1520 The number of bytes which this task has caused, or shall cause to be written
1521 to disk. Similar caveats apply here as with rchar.
1522 
1523 
1524 syscr
1525 -----
1526 
1527 I/O counter: read syscalls
1528 Attempt to count the number of read I/O operations, i.e. syscalls like read()
1529 and pread().
1530 
1531 
1532 syscw
1533 -----
1534 
1535 I/O counter: write syscalls
1536 Attempt to count the number of write I/O operations, i.e. syscalls like
1537 write() and pwrite().
1538 
1539 
1540 read_bytes
1541 ----------
1542 
1543 I/O counter: bytes read
1544 Attempt to count the number of bytes which this process really did cause to
1545 be fetched from the storage layer. Done at the submit_bio() level, so it is
1546 accurate for block-backed filesystems. <please add status regarding NFS and
1547 CIFS at a later time>
1548 
1549 
1550 write_bytes
1551 -----------
1552 
1553 I/O counter: bytes written
1554 Attempt to count the number of bytes which this process caused to be sent to
1555 the storage layer. This is done at page-dirtying time.
1556 
1557 
1558 cancelled_write_bytes
1559 ---------------------
1560 
1561 The big inaccuracy here is truncate. If a process writes 1MB to a file and
1562 then deletes the file, it will in fact perform no writeout. But it will have
1563 been accounted as having caused 1MB of write.
1564 In other words: The number of bytes which this process caused to not happen,
1565 by truncating pagecache. A task can cause "negative" IO too. If this task
1566 truncates some dirty pagecache, some IO which another task has been accounted
1567 for (in its write_bytes) will not be happening. We _could_ just subtract that
1568 from the truncating task's write_bytes, but there is information loss in doing
1569 that.
1570 
1571 
1572 Note
1573 ----
1574 
1575 At its current implementation state, this is a bit racy on 32-bit machines: if
1576 process A reads process B's /proc/pid/io while process B is updating one of
1577 those 64-bit counters, process A could see an intermediate result.
1578 
1579 
1580 More information about this can be found within the taskstats documentation in
1581 Documentation/accounting.
1582 
1583 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1584 ---------------------------------------------------------------
1585 When a process is dumped, all anonymous memory is written to a core file as
1586 long as the size of the core file isn't limited. But sometimes we don't want
1587 to dump some memory segments, for example, huge shared memory. Conversely,
1588 sometimes we want to save file-backed memory segments into a core file, not
1589 only the individual files.
1590 
1591 /proc/<pid>/coredump_filter allows you to customize which memory segments
1592 will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1593 of memory types. If a bit of the bitmask is set, memory segments of the
1594 corresponding memory type are dumped, otherwise they are not dumped.
1595 
1596 The following 7 memory types are supported:
1597   - (bit 0) anonymous private memory
1598   - (bit 1) anonymous shared memory
1599   - (bit 2) file-backed private memory
1600   - (bit 3) file-backed shared memory
1601   - (bit 4) ELF header pages in file-backed private memory areas (it is
1602             effective only if the bit 2 is cleared)
1603   - (bit 5) hugetlb private memory
1604   - (bit 6) hugetlb shared memory
1605 
1606   Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1607   are always dumped regardless of the bitmask status.
1608 
1609   Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
1610   effected by bit 5-6.
1611 
1612 Default value of coredump_filter is 0x23; this means all anonymous memory
1613 segments and hugetlb private memory are dumped.
1614 
1615 If you don't want to dump all shared memory segments attached to pid 1234,
1616 write 0x21 to the process's proc file.
1617 
1618   $ echo 0x21 > /proc/1234/coredump_filter
1619 
1620 When a new process is created, the process inherits the bitmask status from its
1621 parent. It is useful to set up coredump_filter before the program runs.
1622 For example:
1623 
1624   $ echo 0x7 > /proc/self/coredump_filter
1625   $ ./some_program
1626 
1627 3.5     /proc/<pid>/mountinfo - Information about mounts
1628 --------------------------------------------------------
1629 
1630 This file contains lines of the form:
1631 
1632 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1633 (1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
1634 
1635 (1) mount ID:  unique identifier of the mount (may be reused after umount)
1636 (2) parent ID:  ID of parent (or of self for the top of the mount tree)
1637 (3) major:minor:  value of st_dev for files on filesystem
1638 (4) root:  root of the mount within the filesystem
1639 (5) mount point:  mount point relative to the process's root
1640 (6) mount options:  per mount options
1641 (7) optional fields:  zero or more fields of the form "tag[:value]"
1642 (8) separator:  marks the end of the optional fields
1643 (9) filesystem type:  name of filesystem of the form "type[.subtype]"
1644 (10) mount source:  filesystem specific information or "none"
1645 (11) super options:  per super block options
1646 
1647 Parsers should ignore all unrecognised optional fields.  Currently the
1648 possible optional fields are:
1649 
1650 shared:X  mount is shared in peer group X
1651 master:X  mount is slave to peer group X
1652 propagate_from:X  mount is slave and receives propagation from peer group X (*)
1653 unbindable  mount is unbindable
1654 
1655 (*) X is the closest dominant peer group under the process's root.  If
1656 X is the immediate master of the mount, or if there's no dominant peer
1657 group under the same root, then only the "master:X" field is present
1658 and not the "propagate_from:X" field.
1659 
1660 For more information on mount propagation see:
1661 
1662   Documentation/filesystems/sharedsubtree.txt
1663 
1664 
1665 3.6     /proc/<pid>/comm  & /proc/<pid>/task/<tid>/comm
1666 --------------------------------------------------------
1667 These files provide a method to access a tasks comm value. It also allows for
1668 a task to set its own or one of its thread siblings comm value. The comm value
1669 is limited in size compared to the cmdline value, so writing anything longer
1670 then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1671 comm value.
1672 
1673 
1674 3.7     /proc/<pid>/task/<tid>/children - Information about task children
1675 -------------------------------------------------------------------------
1676 This file provides a fast way to retrieve first level children pids
1677 of a task pointed by <pid>/<tid> pair. The format is a space separated
1678 stream of pids.
1679 
1680 Note the "first level" here -- if a child has own children they will
1681 not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1682 to obtain the descendants.
1683 
1684 Since this interface is intended to be fast and cheap it doesn't
1685 guarantee to provide precise results and some children might be
1686 skipped, especially if they've exited right after we printed their
1687 pids, so one need to either stop or freeze processes being inspected
1688 if precise results are needed.
1689 
1690 
1691 3.8     /proc/<pid>/fdinfo/<fd> - Information about opened file
1692 ---------------------------------------------------------------
1693 This file provides information associated with an opened file. The regular
1694 files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1695 represents the current offset of the opened file in decimal form [see lseek(2)
1696 for details], 'flags' denotes the octal O_xxx mask the file has been
1697 created with [see open(2) for details] and 'mnt_id' represents mount ID of
1698 the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1699 for details].
1700 
1701 A typical output is
1702 
1703         pos:    0
1704         flags:  0100002
1705         mnt_id: 19
1706 
1707 The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1708 pair provide additional information particular to the objects they represent.
1709 
1710         Eventfd files
1711         ~~~~~~~~~~~~~
1712         pos:    0
1713         flags:  04002
1714         mnt_id: 9
1715         eventfd-count:  5a
1716 
1717         where 'eventfd-count' is hex value of a counter.
1718 
1719         Signalfd files
1720         ~~~~~~~~~~~~~~
1721         pos:    0
1722         flags:  04002
1723         mnt_id: 9
1724         sigmask:        0000000000000200
1725 
1726         where 'sigmask' is hex value of the signal mask associated
1727         with a file.
1728 
1729         Epoll files
1730         ~~~~~~~~~~~
1731         pos:    0
1732         flags:  02
1733         mnt_id: 9
1734         tfd:        5 events:       1d data: ffffffffffffffff
1735 
1736         where 'tfd' is a target file descriptor number in decimal form,
1737         'events' is events mask being watched and the 'data' is data
1738         associated with a target [see epoll(7) for more details].
1739 
1740         Fsnotify files
1741         ~~~~~~~~~~~~~~
1742         For inotify files the format is the following
1743 
1744         pos:    0
1745         flags:  02000000
1746         inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1747 
1748         where 'wd' is a watch descriptor in decimal form, ie a target file
1749         descriptor number, 'ino' and 'sdev' are inode and device where the
1750         target file resides and the 'mask' is the mask of events, all in hex
1751         form [see inotify(7) for more details].
1752 
1753         If the kernel was built with exportfs support, the path to the target
1754         file is encoded as a file handle.  The file handle is provided by three
1755         fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1756         format.
1757 
1758         If the kernel is built without exportfs support the file handle won't be
1759         printed out.
1760 
1761         If there is no inotify mark attached yet the 'inotify' line will be omitted.
1762 
1763         For fanotify files the format is
1764 
1765         pos:    0
1766         flags:  02
1767         mnt_id: 9
1768         fanotify flags:10 event-flags:0
1769         fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1770         fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1771 
1772         where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1773         call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1774         flags associated with mark which are tracked separately from events
1775         mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1776         mask and 'ignored_mask' is the mask of events which are to be ignored.
1777         All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1778         does provide information about flags and mask used in fanotify_mark
1779         call [see fsnotify manpage for details].
1780 
1781         While the first three lines are mandatory and always printed, the rest is
1782         optional and may be omitted if no marks created yet.
1783 
1784         Timerfd files
1785         ~~~~~~~~~~~~~
1786 
1787         pos:    0
1788         flags:  02
1789         mnt_id: 9
1790         clockid: 0
1791         ticks: 0
1792         settime flags: 01
1793         it_value: (0, 49406829)
1794         it_interval: (1, 0)
1795 
1796         where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
1797         that have occurred [see timerfd_create(2) for details]. 'settime flags' are
1798         flags in octal form been used to setup the timer [see timerfd_settime(2) for
1799         details]. 'it_value' is remaining time until the timer exiration.
1800         'it_interval' is the interval for the timer. Note the timer might be set up
1801         with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
1802         still exhibits timer's remaining time.
1803 
1804 3.9     /proc/<pid>/map_files - Information about memory mapped files
1805 ---------------------------------------------------------------------
1806 This directory contains symbolic links which represent memory mapped files
1807 the process is maintaining.  Example output:
1808 
1809      | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
1810      | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
1811      | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
1812      | ...
1813      | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
1814      | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
1815 
1816 The name of a link represents the virtual memory bounds of a mapping, i.e.
1817 vm_area_struct::vm_start-vm_area_struct::vm_end.
1818 
1819 The main purpose of the map_files is to retrieve a set of memory mapped
1820 files in a fast way instead of parsing /proc/<pid>/maps or
1821 /proc/<pid>/smaps, both of which contain many more records.  At the same
1822 time one can open(2) mappings from the listings of two processes and
1823 comparing their inode numbers to figure out which anonymous memory areas
1824 are actually shared.
1825 
1826 ------------------------------------------------------------------------------
1827 Configuring procfs
1828 ------------------------------------------------------------------------------
1829 
1830 4.1     Mount options
1831 ---------------------
1832 
1833 The following mount options are supported:
1834 
1835         hidepid=        Set /proc/<pid>/ access mode.
1836         gid=            Set the group authorized to learn processes information.
1837 
1838 hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1839 (default).
1840 
1841 hidepid=1 means users may not access any /proc/<pid>/ directories but their
1842 own.  Sensitive files like cmdline, sched*, status are now protected against
1843 other users.  This makes it impossible to learn whether any user runs
1844 specific program (given the program doesn't reveal itself by its behaviour).
1845 As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1846 poorly written programs passing sensitive information via program arguments are
1847 now protected against local eavesdroppers.
1848 
1849 hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1850 users.  It doesn't mean that it hides a fact whether a process with a specific
1851 pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1852 but it hides process' uid and gid, which may be learned by stat()'ing
1853 /proc/<pid>/ otherwise.  It greatly complicates an intruder's task of gathering
1854 information about running processes, whether some daemon runs with elevated
1855 privileges, whether other user runs some sensitive program, whether other users
1856 run any program at all, etc.
1857 
1858 gid= defines a group authorized to learn processes information otherwise
1859 prohibited by hidepid=.  If you use some daemon like identd which needs to learn
1860 information about processes information, just add identd to this group.

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