Version:  2.0.40 2.2.26 2.4.37 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 4.1 4.2

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 an
204 asynchronous manner and the value 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 4.1)
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  Ngid                        NUMA group ID (0 if none)
217  Pid                         process id
218  PPid                        process id of the parent process
219  TracerPid                   PID of process tracing this process (0 if not)
220  Uid                         Real, effective, saved set, and  file system UIDs
221  Gid                         Real, effective, saved set, and  file system GIDs
222  FDSize                      number of file descriptor slots currently allocated
223  Groups                      supplementary group list
224  NStgid                      descendant namespace thread group ID hierarchy
225  NSpid                       descendant namespace process ID hierarchy
226  NSpgid                      descendant namespace process group ID hierarchy
227  NSsid                       descendant namespace session ID hierarchy
228  VmPeak                      peak virtual memory size
229  VmSize                      total program size
230  VmLck                       locked memory size
231  VmHWM                       peak resident set size ("high water mark")
232  VmRSS                       size of memory portions
233  VmData                      size of data, stack, and text segments
234  VmStk                       size of data, stack, and text segments
235  VmExe                       size of text segment
236  VmLib                       size of shared library code
237  VmPTE                       size of page table entries
238  VmPMD                       size of second level page tables
239  VmSwap                      size of swap usage (the number of referred swapents)
240  Threads                     number of threads
241  SigQ                        number of signals queued/max. number for queue
242  SigPnd                      bitmap of pending signals for the thread
243  ShdPnd                      bitmap of shared pending signals for the process
244  SigBlk                      bitmap of blocked signals
245  SigIgn                      bitmap of ignored signals
246  SigCgt                      bitmap of caught signals
247  CapInh                      bitmap of inheritable capabilities
248  CapPrm                      bitmap of permitted capabilities
249  CapEff                      bitmap of effective capabilities
250  CapBnd                      bitmap of capabilities bounding set
251  Seccomp                     seccomp mode, like prctl(PR_GET_SECCOMP, ...)
252  Cpus_allowed                mask of CPUs on which this process may run
253  Cpus_allowed_list           Same as previous, but in "list format"
254  Mems_allowed                mask of memory nodes allowed to this process
255  Mems_allowed_list           Same as previous, but in "list format"
256  voluntary_ctxt_switches     number of voluntary context switches
257  nonvoluntary_ctxt_switches  number of non voluntary context switches
258 ..............................................................................
259 
260 Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
261 ..............................................................................
262  Field    Content
263  size     total program size (pages)            (same as VmSize in status)
264  resident size of memory portions (pages)       (same as VmRSS in status)
265  shared   number of pages that are shared       (i.e. backed by a file)
266  trs      number of pages that are 'code'       (not including libs; broken,
267                                                         includes data segment)
268  lrs      number of pages of library            (always 0 on 2.6)
269  drs      number of pages of data/stack         (including libs; broken,
270                                                         includes library text)
271  dt       number of dirty pages                 (always 0 on 2.6)
272 ..............................................................................
273 
274 
275 Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
276 ..............................................................................
277  Field          Content
278   pid           process id
279   tcomm         filename of the executable
280   state         state (R is running, S is sleeping, D is sleeping in an
281                 uninterruptible wait, Z is zombie, T is traced or stopped)
282   ppid          process id of the parent process
283   pgrp          pgrp of the process
284   sid           session id
285   tty_nr        tty the process uses
286   tty_pgrp      pgrp of the tty
287   flags         task flags
288   min_flt       number of minor faults
289   cmin_flt      number of minor faults with child's
290   maj_flt       number of major faults
291   cmaj_flt      number of major faults with child's
292   utime         user mode jiffies
293   stime         kernel mode jiffies
294   cutime        user mode jiffies with child's
295   cstime        kernel mode jiffies with child's
296   priority      priority level
297   nice          nice level
298   num_threads   number of threads
299   it_real_value (obsolete, always 0)
300   start_time    time the process started after system boot
301   vsize         virtual memory size
302   rss           resident set memory size
303   rsslim        current limit in bytes on the rss
304   start_code    address above which program text can run
305   end_code      address below which program text can run
306   start_stack   address of the start of the main process stack
307   esp           current value of ESP
308   eip           current value of EIP
309   pending       bitmap of pending signals
310   blocked       bitmap of blocked signals
311   sigign        bitmap of ignored signals
312   sigcatch      bitmap of caught signals
313   wchan         address where process went to sleep
314   0             (place holder)
315   0             (place holder)
316   exit_signal   signal to send to parent thread on exit
317   task_cpu      which CPU the task is scheduled on
318   rt_priority   realtime priority
319   policy        scheduling policy (man sched_setscheduler)
320   blkio_ticks   time spent waiting for block IO
321   gtime         guest time of the task in jiffies
322   cgtime        guest time of the task children in jiffies
323   start_data    address above which program data+bss is placed
324   end_data      address below which program data+bss is placed
325   start_brk     address above which program heap can be expanded with brk()
326   arg_start     address above which program command line is placed
327   arg_end       address below which program command line is placed
328   env_start     address above which program environment is placed
329   env_end       address below which program environment is placed
330   exit_code     the thread's exit_code in the form reported by the waitpid system call
331 ..............................................................................
332 
333 The /proc/PID/maps file containing the currently mapped memory regions and
334 their access permissions.
335 
336 The format is:
337 
338 address           perms offset  dev   inode      pathname
339 
340 08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
341 08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
342 0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
343 a7cb1000-a7cb2000 ---p 00000000 00:00 0
344 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
345 a7eb2000-a7eb3000 ---p 00000000 00:00 0
346 a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack:1001]
347 a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
348 a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
349 a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
350 a800b000-a800e000 rw-p 00000000 00:00 0
351 a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
352 a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
353 a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
354 a8024000-a8027000 rw-p 00000000 00:00 0
355 a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
356 a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
357 a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
358 aff35000-aff4a000 rw-p 00000000 00:00 0          [stack]
359 ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
360 
361 where "address" is the address space in the process that it occupies, "perms"
362 is a set of permissions:
363 
364  r = read
365  w = write
366  x = execute
367  s = shared
368  p = private (copy on write)
369 
370 "offset" is the offset into the mapping, "dev" is the device (major:minor), and
371 "inode" is the inode  on that device.  0 indicates that  no inode is associated
372 with the memory region, as the case would be with BSS (uninitialized data).
373 The "pathname" shows the name associated file for this mapping.  If the mapping
374 is not associated with a file:
375 
376  [heap]                   = the heap of the program
377  [stack]                  = the stack of the main process
378  [stack:1001]             = the stack of the thread with tid 1001
379  [vdso]                   = the "virtual dynamic shared object",
380                             the kernel system call handler
381 
382  or if empty, the mapping is anonymous.
383 
384 The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint
385 of the individual tasks of a process. In this file you will see a mapping marked
386 as [stack] if that task sees it as a stack. This is a key difference from the
387 content of /proc/PID/maps, where you will see all mappings that are being used
388 as stack by all of those tasks. Hence, for the example above, the task-level
389 map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this:
390 
391 08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
392 08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
393 0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
394 a7cb1000-a7cb2000 ---p 00000000 00:00 0
395 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
396 a7eb2000-a7eb3000 ---p 00000000 00:00 0
397 a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack]
398 a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
399 a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
400 a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
401 a800b000-a800e000 rw-p 00000000 00:00 0
402 a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
403 a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
404 a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
405 a8024000-a8027000 rw-p 00000000 00:00 0
406 a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
407 a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
408 a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
409 aff35000-aff4a000 rw-p 00000000 00:00 0
410 ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
411 
412 The /proc/PID/smaps is an extension based on maps, showing the memory
413 consumption for each of the process's mappings. For each of mappings there
414 is a series of lines such as the following:
415 
416 08048000-080bc000 r-xp 00000000 03:02 13130      /bin/bash
417 Size:               1084 kB
418 Rss:                 892 kB
419 Pss:                 374 kB
420 Shared_Clean:        892 kB
421 Shared_Dirty:          0 kB
422 Private_Clean:         0 kB
423 Private_Dirty:         0 kB
424 Referenced:          892 kB
425 Anonymous:             0 kB
426 Swap:                  0 kB
427 KernelPageSize:        4 kB
428 MMUPageSize:           4 kB
429 Locked:              374 kB
430 VmFlags: rd ex mr mw me de
431 
432 the first of these lines shows the same information as is displayed for the
433 mapping in /proc/PID/maps.  The remaining lines show the size of the mapping
434 (size), the amount of the mapping that is currently resident in RAM (RSS), the
435 process' proportional share of this mapping (PSS), the number of clean and
436 dirty private pages in the mapping.  Note that even a page which is part of a
437 MAP_SHARED mapping, but has only a single pte mapped, i.e.  is currently used
438 by only one process, is accounted as private and not as shared.  "Referenced"
439 indicates the amount of memory currently marked as referenced or accessed.
440 "Anonymous" shows the amount of memory that does not belong to any file.  Even
441 a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
442 and a page is modified, the file page is replaced by a private anonymous copy.
443 "Swap" shows how much would-be-anonymous memory is also used, but out on
444 swap.
445 
446 "VmFlags" field deserves a separate description. This member represents the kernel
447 flags associated with the particular virtual memory area in two letter encoded
448 manner. The codes are the following:
449     rd  - readable
450     wr  - writeable
451     ex  - executable
452     sh  - shared
453     mr  - may read
454     mw  - may write
455     me  - may execute
456     ms  - may share
457     gd  - stack segment growns down
458     pf  - pure PFN range
459     dw  - disabled write to the mapped file
460     lo  - pages are locked in memory
461     io  - memory mapped I/O area
462     sr  - sequential read advise provided
463     rr  - random read advise provided
464     dc  - do not copy area on fork
465     de  - do not expand area on remapping
466     ac  - area is accountable
467     nr  - swap space is not reserved for the area
468     ht  - area uses huge tlb pages
469     nl  - non-linear mapping
470     ar  - architecture specific flag
471     dd  - do not include area into core dump
472     sd  - soft-dirty flag
473     mm  - mixed map area
474     hg  - huge page advise flag
475     nh  - no-huge page advise flag
476     mg  - mergable advise flag
477 
478 Note that there is no guarantee that every flag and associated mnemonic will
479 be present in all further kernel releases. Things get changed, the flags may
480 be vanished or the reverse -- new added.
481 
482 This file is only present if the CONFIG_MMU kernel configuration option is
483 enabled.
484 
485 The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
486 bits on both physical and virtual pages associated with a process, and the
487 soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details).
488 To clear the bits for all the pages associated with the process
489     > echo 1 > /proc/PID/clear_refs
490 
491 To clear the bits for the anonymous pages associated with the process
492     > echo 2 > /proc/PID/clear_refs
493 
494 To clear the bits for the file mapped pages associated with the process
495     > echo 3 > /proc/PID/clear_refs
496 
497 To clear the soft-dirty bit
498     > echo 4 > /proc/PID/clear_refs
499 
500 To reset the peak resident set size ("high water mark") to the process's
501 current value:
502     > echo 5 > /proc/PID/clear_refs
503 
504 Any other value written to /proc/PID/clear_refs will have no effect.
505 
506 The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
507 using /proc/kpageflags and number of times a page is mapped using
508 /proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
509 
510 The /proc/pid/numa_maps is an extension based on maps, showing the memory
511 locality and binding policy, as well as the memory usage (in pages) of
512 each mapping. The output follows a general format where mapping details get
513 summarized separated by blank spaces, one mapping per each file line:
514 
515 address   policy    mapping details
516 
517 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
518 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
519 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
520 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
521 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
522 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
523 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
524 320698b000 default file=/lib64/libc-2.12.so
525 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
526 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
527 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
528 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
529 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
530 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
531 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
532 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
533 
534 Where:
535 "address" is the starting address for the mapping;
536 "policy" reports the NUMA memory policy set for the mapping (see vm/numa_memory_policy.txt);
537 "mapping details" summarizes mapping data such as mapping type, page usage counters,
538 node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
539 size, in KB, that is backing the mapping up.
540 
541 1.2 Kernel data
542 ---------------
543 
544 Similar to  the  process entries, the kernel data files give information about
545 the running kernel. The files used to obtain this information are contained in
546 /proc and  are  listed  in Table 1-5. Not all of these will be present in your
547 system. It  depends  on the kernel configuration and the loaded modules, which
548 files are there, and which are missing.
549 
550 Table 1-5: Kernel info in /proc
551 ..............................................................................
552  File        Content                                           
553  apm         Advanced power management info                    
554  buddyinfo   Kernel memory allocator information (see text)     (2.5)
555  bus         Directory containing bus specific information     
556  cmdline     Kernel command line                               
557  cpuinfo     Info about the CPU                                
558  devices     Available devices (block and character)           
559  dma         Used DMS channels                                 
560  filesystems Supported filesystems                             
561  driver      Various drivers grouped here, currently rtc (2.4)
562  execdomains Execdomains, related to security                   (2.4)
563  fb          Frame Buffer devices                               (2.4)
564  fs          File system parameters, currently nfs/exports      (2.4)
565  ide         Directory containing info about the IDE subsystem 
566  interrupts  Interrupt usage                                   
567  iomem       Memory map                                         (2.4)
568  ioports     I/O port usage                                    
569  irq         Masks for irq to cpu affinity                      (2.4)(smp?)
570  isapnp      ISA PnP (Plug&Play) Info                           (2.4)
571  kcore       Kernel core image (can be ELF or A.OUT(deprecated in 2.4))   
572  kmsg        Kernel messages                                   
573  ksyms       Kernel symbol table                               
574  loadavg     Load average of last 1, 5 & 15 minutes                
575  locks       Kernel locks                                      
576  meminfo     Memory info                                       
577  misc        Miscellaneous                                     
578  modules     List of loaded modules                            
579  mounts      Mounted filesystems                               
580  net         Networking info (see text)                        
581  pagetypeinfo Additional page allocator information (see text)  (2.5)
582  partitions  Table of partitions known to the system           
583  pci         Deprecated info of PCI bus (new way -> /proc/bus/pci/,
584              decoupled by lspci                                 (2.4)
585  rtc         Real time clock                                   
586  scsi        SCSI info (see text)                              
587  slabinfo    Slab pool info                                    
588  softirqs    softirq usage
589  stat        Overall statistics                                
590  swaps       Swap space utilization                            
591  sys         See chapter 2                                     
592  sysvipc     Info of SysVIPC Resources (msg, sem, shm)          (2.4)
593  tty         Info of tty drivers
594  uptime      Wall clock since boot, combined idle time of all cpus
595  version     Kernel version                                    
596  video       bttv info of video resources                       (2.4)
597  vmallocinfo Show vmalloced areas
598 ..............................................................................
599 
600 You can,  for  example,  check  which interrupts are currently in use and what
601 they are used for by looking in the file /proc/interrupts:
602 
603   > cat /proc/interrupts 
604              CPU0        
605     0:    8728810          XT-PIC  timer 
606     1:        895          XT-PIC  keyboard 
607     2:          0          XT-PIC  cascade 
608     3:     531695          XT-PIC  aha152x 
609     4:    2014133          XT-PIC  serial 
610     5:      44401          XT-PIC  pcnet_cs 
611     8:          2          XT-PIC  rtc 
612    11:          8          XT-PIC  i82365 
613    12:     182918          XT-PIC  PS/2 Mouse 
614    13:          1          XT-PIC  fpu 
615    14:    1232265          XT-PIC  ide0 
616    15:          7          XT-PIC  ide1 
617   NMI:          0 
618 
619 In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
620 output of a SMP machine):
621 
622   > cat /proc/interrupts 
623 
624              CPU0       CPU1       
625     0:    1243498    1214548    IO-APIC-edge  timer
626     1:       8949       8958    IO-APIC-edge  keyboard
627     2:          0          0          XT-PIC  cascade
628     5:      11286      10161    IO-APIC-edge  soundblaster
629     8:          1          0    IO-APIC-edge  rtc
630     9:      27422      27407    IO-APIC-edge  3c503
631    12:     113645     113873    IO-APIC-edge  PS/2 Mouse
632    13:          0          0          XT-PIC  fpu
633    14:      22491      24012    IO-APIC-edge  ide0
634    15:       2183       2415    IO-APIC-edge  ide1
635    17:      30564      30414   IO-APIC-level  eth0
636    18:        177        164   IO-APIC-level  bttv
637   NMI:    2457961    2457959 
638   LOC:    2457882    2457881 
639   ERR:       2155
640 
641 NMI is incremented in this case because every timer interrupt generates a NMI
642 (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
643 
644 LOC is the local interrupt counter of the internal APIC of every CPU.
645 
646 ERR is incremented in the case of errors in the IO-APIC bus (the bus that
647 connects the CPUs in a SMP system. This means that an error has been detected,
648 the IO-APIC automatically retry the transmission, so it should not be a big
649 problem, but you should read the SMP-FAQ.
650 
651 In 2.6.2* /proc/interrupts was expanded again.  This time the goal was for
652 /proc/interrupts to display every IRQ vector in use by the system, not
653 just those considered 'most important'.  The new vectors are:
654 
655   THR -- interrupt raised when a machine check threshold counter
656   (typically counting ECC corrected errors of memory or cache) exceeds
657   a configurable threshold.  Only available on some systems.
658 
659   TRM -- a thermal event interrupt occurs when a temperature threshold
660   has been exceeded for the CPU.  This interrupt may also be generated
661   when the temperature drops back to normal.
662 
663   SPU -- a spurious interrupt is some interrupt that was raised then lowered
664   by some IO device before it could be fully processed by the APIC.  Hence
665   the APIC sees the interrupt but does not know what device it came from.
666   For this case the APIC will generate the interrupt with a IRQ vector
667   of 0xff. This might also be generated by chipset bugs.
668 
669   RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
670   sent from one CPU to another per the needs of the OS.  Typically,
671   their statistics are used by kernel developers and interested users to
672   determine the occurrence of interrupts of the given type.
673 
674 The above IRQ vectors are displayed only when relevant.  For example,
675 the threshold vector does not exist on x86_64 platforms.  Others are
676 suppressed when the system is a uniprocessor.  As of this writing, only
677 i386 and x86_64 platforms support the new IRQ vector displays.
678 
679 Of some interest is the introduction of the /proc/irq directory to 2.4.
680 It could be used to set IRQ to CPU affinity, this means that you can "hook" an
681 IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
682 irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
683 prof_cpu_mask.
684 
685 For example 
686   > ls /proc/irq/
687   0  10  12  14  16  18  2  4  6  8  prof_cpu_mask
688   1  11  13  15  17  19  3  5  7  9  default_smp_affinity
689   > ls /proc/irq/0/
690   smp_affinity
691 
692 smp_affinity is a bitmask, in which you can specify which CPUs can handle the
693 IRQ, you can set it by doing:
694 
695   > echo 1 > /proc/irq/10/smp_affinity
696 
697 This means that only the first CPU will handle the IRQ, but you can also echo
698 5 which means that only the first and fourth CPU can handle the IRQ.
699 
700 The contents of each smp_affinity file is the same by default:
701 
702   > cat /proc/irq/0/smp_affinity
703   ffffffff
704 
705 There is an alternate interface, smp_affinity_list which allows specifying
706 a cpu range instead of a bitmask:
707 
708   > cat /proc/irq/0/smp_affinity_list
709   1024-1031
710 
711 The default_smp_affinity mask applies to all non-active IRQs, which are the
712 IRQs which have not yet been allocated/activated, and hence which lack a
713 /proc/irq/[0-9]* directory.
714 
715 The node file on an SMP system shows the node to which the device using the IRQ
716 reports itself as being attached. This hardware locality information does not
717 include information about any possible driver locality preference.
718 
719 prof_cpu_mask specifies which CPUs are to be profiled by the system wide
720 profiler. Default value is ffffffff (all cpus if there are only 32 of them).
721 
722 The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
723 between all the CPUs which are allowed to handle it. As usual the kernel has
724 more info than you and does a better job than you, so the defaults are the
725 best choice for almost everyone.  [Note this applies only to those IO-APIC's
726 that support "Round Robin" interrupt distribution.]
727 
728 There are  three  more  important subdirectories in /proc: net, scsi, and sys.
729 The general  rule  is  that  the  contents,  or  even  the  existence of these
730 directories, depend  on your kernel configuration. If SCSI is not enabled, the
731 directory scsi  may  not  exist. The same is true with the net, which is there
732 only when networking support is present in the running kernel.
733 
734 The slabinfo  file  gives  information  about  memory usage at the slab level.
735 Linux uses  slab  pools for memory management above page level in version 2.2.
736 Commonly used  objects  have  their  own  slab  pool (such as network buffers,
737 directory cache, and so on).
738 
739 ..............................................................................
740 
741 > cat /proc/buddyinfo
742 
743 Node 0, zone      DMA      0      4      5      4      4      3 ...
744 Node 0, zone   Normal      1      0      0      1    101      8 ...
745 Node 0, zone  HighMem      2      0      0      1      1      0 ...
746 
747 External fragmentation is a problem under some workloads, and buddyinfo is a
748 useful tool for helping diagnose these problems.  Buddyinfo will give you a 
749 clue as to how big an area you can safely allocate, or why a previous
750 allocation failed.
751 
752 Each column represents the number of pages of a certain order which are 
753 available.  In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 
754 ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 
755 available in ZONE_NORMAL, etc... 
756 
757 More information relevant to external fragmentation can be found in
758 pagetypeinfo.
759 
760 > cat /proc/pagetypeinfo
761 Page block order: 9
762 Pages per block:  512
763 
764 Free pages count per migrate type at order       0      1      2      3      4      5      6      7      8      9     10
765 Node    0, zone      DMA, type    Unmovable      0      0      0      1      1      1      1      1      1      1      0
766 Node    0, zone      DMA, type  Reclaimable      0      0      0      0      0      0      0      0      0      0      0
767 Node    0, zone      DMA, type      Movable      1      1      2      1      2      1      1      0      1      0      2
768 Node    0, zone      DMA, type      Reserve      0      0      0      0      0      0      0      0      0      1      0
769 Node    0, zone      DMA, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
770 Node    0, zone    DMA32, type    Unmovable    103     54     77      1      1      1     11      8      7      1      9
771 Node    0, zone    DMA32, type  Reclaimable      0      0      2      1      0      0      0      0      1      0      0
772 Node    0, zone    DMA32, type      Movable    169    152    113     91     77     54     39     13      6      1    452
773 Node    0, zone    DMA32, type      Reserve      1      2      2      2      2      0      1      1      1      1      0
774 Node    0, zone    DMA32, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
775 
776 Number of blocks type     Unmovable  Reclaimable      Movable      Reserve      Isolate
777 Node 0, zone      DMA            2            0            5            1            0
778 Node 0, zone    DMA32           41            6          967            2            0
779 
780 Fragmentation avoidance in the kernel works by grouping pages of different
781 migrate types into the same contiguous regions of memory called page blocks.
782 A page block is typically the size of the default hugepage size e.g. 2MB on
783 X86-64. By keeping pages grouped based on their ability to move, the kernel
784 can reclaim pages within a page block to satisfy a high-order allocation.
785 
786 The pagetypinfo begins with information on the size of a page block. It
787 then gives the same type of information as buddyinfo except broken down
788 by migrate-type and finishes with details on how many page blocks of each
789 type exist.
790 
791 If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
792 from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
793 make an estimate of the likely number of huge pages that can be allocated
794 at a given point in time. All the "Movable" blocks should be allocatable
795 unless memory has been mlock()'d. Some of the Reclaimable blocks should
796 also be allocatable although a lot of filesystem metadata may have to be
797 reclaimed to achieve this.
798 
799 ..............................................................................
800 
801 meminfo:
802 
803 Provides information about distribution and utilization of memory.  This
804 varies by architecture and compile options.  The following is from a
805 16GB PIII, which has highmem enabled.  You may not have all of these fields.
806 
807 > cat /proc/meminfo
808 
809 The "Locked" indicates whether the mapping is locked in memory or not.
810 
811 
812 MemTotal:     16344972 kB
813 MemFree:      13634064 kB
814 MemAvailable: 14836172 kB
815 Buffers:          3656 kB
816 Cached:        1195708 kB
817 SwapCached:          0 kB
818 Active:         891636 kB
819 Inactive:      1077224 kB
820 HighTotal:    15597528 kB
821 HighFree:     13629632 kB
822 LowTotal:       747444 kB
823 LowFree:          4432 kB
824 SwapTotal:           0 kB
825 SwapFree:            0 kB
826 Dirty:             968 kB
827 Writeback:           0 kB
828 AnonPages:      861800 kB
829 Mapped:         280372 kB
830 Slab:           284364 kB
831 SReclaimable:   159856 kB
832 SUnreclaim:     124508 kB
833 PageTables:      24448 kB
834 NFS_Unstable:        0 kB
835 Bounce:              0 kB
836 WritebackTmp:        0 kB
837 CommitLimit:   7669796 kB
838 Committed_AS:   100056 kB
839 VmallocTotal:   112216 kB
840 VmallocUsed:       428 kB
841 VmallocChunk:   111088 kB
842 AnonHugePages:   49152 kB
843 
844     MemTotal: Total usable ram (i.e. physical ram minus a few reserved
845               bits and the kernel binary code)
846      MemFree: The sum of LowFree+HighFree
847 MemAvailable: An estimate of how much memory is available for starting new
848               applications, without swapping. Calculated from MemFree,
849               SReclaimable, the size of the file LRU lists, and the low
850               watermarks in each zone.
851               The estimate takes into account that the system needs some
852               page cache to function well, and that not all reclaimable
853               slab will be reclaimable, due to items being in use. The
854               impact of those factors will vary from system to system.
855      Buffers: Relatively temporary storage for raw disk blocks
856               shouldn't get tremendously large (20MB or so)
857       Cached: in-memory cache for files read from the disk (the
858               pagecache).  Doesn't include SwapCached
859   SwapCached: Memory that once was swapped out, is swapped back in but
860               still also is in the swapfile (if memory is needed it
861               doesn't need to be swapped out AGAIN because it is already
862               in the swapfile. This saves I/O)
863       Active: Memory that has been used more recently and usually not
864               reclaimed unless absolutely necessary.
865     Inactive: Memory which has been less recently used.  It is more
866               eligible to be reclaimed for other purposes
867    HighTotal:
868     HighFree: Highmem is all memory above ~860MB of physical memory
869               Highmem areas are for use by userspace programs, or
870               for the pagecache.  The kernel must use tricks to access
871               this memory, making it slower to access than lowmem.
872     LowTotal:
873      LowFree: Lowmem is memory which can be used for everything that
874               highmem can be used for, but it is also available for the
875               kernel's use for its own data structures.  Among many
876               other things, it is where everything from the Slab is
877               allocated.  Bad things happen when you're out of lowmem.
878    SwapTotal: total amount of swap space available
879     SwapFree: Memory which has been evicted from RAM, and is temporarily
880               on the disk
881        Dirty: Memory which is waiting to get written back to the disk
882    Writeback: Memory which is actively being written back to the disk
883    AnonPages: Non-file backed pages mapped into userspace page tables
884 AnonHugePages: Non-file backed huge pages mapped into userspace page tables
885       Mapped: files which have been mmaped, such as libraries
886         Slab: in-kernel data structures cache
887 SReclaimable: Part of Slab, that might be reclaimed, such as caches
888   SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
889   PageTables: amount of memory dedicated to the lowest level of page
890               tables.
891 NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
892               storage
893       Bounce: Memory used for block device "bounce buffers"
894 WritebackTmp: Memory used by FUSE for temporary writeback buffers
895  CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
896               this is the total amount of  memory currently available to
897               be allocated on the system. This limit is only adhered to
898               if strict overcommit accounting is enabled (mode 2 in
899               'vm.overcommit_memory').
900               The CommitLimit is calculated with the following formula:
901               CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
902                              overcommit_ratio / 100 + [total swap pages]
903               For example, on a system with 1G of physical RAM and 7G
904               of swap with a `vm.overcommit_ratio` of 30 it would
905               yield a CommitLimit of 7.3G.
906               For more details, see the memory overcommit documentation
907               in vm/overcommit-accounting.
908 Committed_AS: The amount of memory presently allocated on the system.
909               The committed memory is a sum of all of the memory which
910               has been allocated by processes, even if it has not been
911               "used" by them as of yet. A process which malloc()'s 1G
912               of memory, but only touches 300M of it will show up as
913               using 1G. This 1G is memory which has been "committed" to
914               by the VM and can be used at any time by the allocating
915               application. With strict overcommit enabled on the system
916               (mode 2 in 'vm.overcommit_memory'),allocations which would
917               exceed the CommitLimit (detailed above) will not be permitted.
918               This is useful if one needs to guarantee that processes will
919               not fail due to lack of memory once that memory has been
920               successfully allocated.
921 VmallocTotal: total size of vmalloc memory area
922  VmallocUsed: amount of vmalloc area which is used
923 VmallocChunk: largest contiguous block of vmalloc area which is free
924 
925 ..............................................................................
926 
927 vmallocinfo:
928 
929 Provides information about vmalloced/vmaped areas. One line per area,
930 containing the virtual address range of the area, size in bytes,
931 caller information of the creator, and optional information depending
932 on the kind of area :
933 
934  pages=nr    number of pages
935  phys=addr   if a physical address was specified
936  ioremap     I/O mapping (ioremap() and friends)
937  vmalloc     vmalloc() area
938  vmap        vmap()ed pages
939  user        VM_USERMAP area
940  vpages      buffer for pages pointers was vmalloced (huge area)
941  N<node>=nr  (Only on NUMA kernels)
942              Number of pages allocated on memory node <node>
943 
944 > cat /proc/vmallocinfo
945 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
946   /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
947 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
948   /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
949 0xffffc20000302000-0xffffc20000304000    8192 acpi_tb_verify_table+0x21/0x4f...
950   phys=7fee8000 ioremap
951 0xffffc20000304000-0xffffc20000307000   12288 acpi_tb_verify_table+0x21/0x4f...
952   phys=7fee7000 ioremap
953 0xffffc2000031d000-0xffffc2000031f000    8192 init_vdso_vars+0x112/0x210
954 0xffffc2000031f000-0xffffc2000032b000   49152 cramfs_uncompress_init+0x2e ...
955   /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
956 0xffffc2000033a000-0xffffc2000033d000   12288 sys_swapon+0x640/0xac0      ...
957   pages=2 vmalloc N1=2
958 0xffffc20000347000-0xffffc2000034c000   20480 xt_alloc_table_info+0xfe ...
959   /0x130 [x_tables] pages=4 vmalloc N0=4
960 0xffffffffa0000000-0xffffffffa000f000   61440 sys_init_module+0xc27/0x1d00 ...
961    pages=14 vmalloc N2=14
962 0xffffffffa000f000-0xffffffffa0014000   20480 sys_init_module+0xc27/0x1d00 ...
963    pages=4 vmalloc N1=4
964 0xffffffffa0014000-0xffffffffa0017000   12288 sys_init_module+0xc27/0x1d00 ...
965    pages=2 vmalloc N1=2
966 0xffffffffa0017000-0xffffffffa0022000   45056 sys_init_module+0xc27/0x1d00 ...
967    pages=10 vmalloc N0=10
968 
969 ..............................................................................
970 
971 softirqs:
972 
973 Provides counts of softirq handlers serviced since boot time, for each cpu.
974 
975 > cat /proc/softirqs
976                 CPU0       CPU1       CPU2       CPU3
977       HI:          0          0          0          0
978    TIMER:      27166      27120      27097      27034
979   NET_TX:          0          0          0         17
980   NET_RX:         42          0          0         39
981    BLOCK:          0          0        107       1121
982  TASKLET:          0          0          0        290
983    SCHED:      27035      26983      26971      26746
984  HRTIMER:          0          0          0          0
985      RCU:       1678       1769       2178       2250
986 
987 
988 1.3 IDE devices in /proc/ide
989 ----------------------------
990 
991 The subdirectory /proc/ide contains information about all IDE devices of which
992 the kernel  is  aware.  There is one subdirectory for each IDE controller, the
993 file drivers  and a link for each IDE device, pointing to the device directory
994 in the controller specific subtree.
995 
996 The file  drivers  contains general information about the drivers used for the
997 IDE devices:
998 
999   > cat /proc/ide/drivers
1000   ide-cdrom version 4.53
1001   ide-disk version 1.08
1002 
1003 More detailed  information  can  be  found  in  the  controller  specific
1004 subdirectories. These  are  named  ide0,  ide1  and  so  on.  Each  of  these
1005 directories contains the files shown in table 1-6.
1006 
1007 
1008 Table 1-6: IDE controller info in  /proc/ide/ide?
1009 ..............................................................................
1010  File    Content                                 
1011  channel IDE channel (0 or 1)                    
1012  config  Configuration (only for PCI/IDE bridge) 
1013  mate    Mate name                               
1014  model   Type/Chipset of IDE controller          
1015 ..............................................................................
1016 
1017 Each device  connected  to  a  controller  has  a separate subdirectory in the
1018 controllers directory.  The  files  listed in table 1-7 are contained in these
1019 directories.
1020 
1021 
1022 Table 1-7: IDE device information
1023 ..............................................................................
1024  File             Content                                    
1025  cache            The cache                                  
1026  capacity         Capacity of the medium (in 512Byte blocks) 
1027  driver           driver and version                         
1028  geometry         physical and logical geometry              
1029  identify         device identify block                      
1030  media            media type                                 
1031  model            device identifier                          
1032  settings         device setup                               
1033  smart_thresholds IDE disk management thresholds             
1034  smart_values     IDE disk management values                 
1035 ..............................................................................
1036 
1037 The most  interesting  file is settings. This file contains a nice overview of
1038 the drive parameters:
1039 
1040   # cat /proc/ide/ide0/hda/settings 
1041   name                    value           min             max             mode 
1042   ----                    -----           ---             ---             ---- 
1043   bios_cyl                526             0               65535           rw 
1044   bios_head               255             0               255             rw 
1045   bios_sect               63              0               63              rw 
1046   breada_readahead        4               0               127             rw 
1047   bswap                   0               0               1               r 
1048   file_readahead          72              0               2097151         rw 
1049   io_32bit                0               0               3               rw 
1050   keepsettings            0               0               1               rw 
1051   max_kb_per_request      122             1               127             rw 
1052   multcount               0               0               8               rw 
1053   nice1                   1               0               1               rw 
1054   nowerr                  0               0               1               rw 
1055   pio_mode                write-only      0               255             w 
1056   slow                    0               0               1               rw 
1057   unmaskirq               0               0               1               rw 
1058   using_dma               0               0               1               rw 
1059 
1060 
1061 1.4 Networking info in /proc/net
1062 --------------------------------
1063 
1064 The subdirectory  /proc/net  follows  the  usual  pattern. Table 1-8 shows the
1065 additional values  you  get  for  IP  version 6 if you configure the kernel to
1066 support this. Table 1-9 lists the files and their meaning.
1067 
1068 
1069 Table 1-8: IPv6 info in /proc/net
1070 ..............................................................................
1071  File       Content                                               
1072  udp6       UDP sockets (IPv6)                                    
1073  tcp6       TCP sockets (IPv6)                                    
1074  raw6       Raw device statistics (IPv6)                          
1075  igmp6      IP multicast addresses, which this host joined (IPv6) 
1076  if_inet6   List of IPv6 interface addresses                      
1077  ipv6_route Kernel routing table for IPv6                         
1078  rt6_stats  Global IPv6 routing tables statistics                 
1079  sockstat6  Socket statistics (IPv6)                              
1080  snmp6      Snmp data (IPv6)                                      
1081 ..............................................................................
1082 
1083 
1084 Table 1-9: Network info in /proc/net
1085 ..............................................................................
1086  File          Content                                                         
1087  arp           Kernel  ARP table                                               
1088  dev           network devices with statistics                                 
1089  dev_mcast     the Layer2 multicast groups a device is listening too
1090                (interface index, label, number of references, number of bound
1091                addresses). 
1092  dev_stat      network device status                                           
1093  ip_fwchains   Firewall chain linkage                                          
1094  ip_fwnames    Firewall chain names                                            
1095  ip_masq       Directory containing the masquerading tables                    
1096  ip_masquerade Major masquerading table                                        
1097  netstat       Network statistics                                              
1098  raw           raw device statistics                                           
1099  route         Kernel routing table                                            
1100  rpc           Directory containing rpc info                                   
1101  rt_cache      Routing cache                                                   
1102  snmp          SNMP data                                                       
1103  sockstat      Socket statistics                                               
1104  tcp           TCP  sockets                                                    
1105  udp           UDP sockets                                                     
1106  unix          UNIX domain sockets                                             
1107  wireless      Wireless interface data (Wavelan etc)                           
1108  igmp          IP multicast addresses, which this host joined                  
1109  psched        Global packet scheduler parameters.                             
1110  netlink       List of PF_NETLINK sockets                                      
1111  ip_mr_vifs    List of multicast virtual interfaces                            
1112  ip_mr_cache   List of multicast routing cache                                 
1113 ..............................................................................
1114 
1115 You can  use  this  information  to see which network devices are available in
1116 your system and how much traffic was routed over those devices:
1117 
1118   > cat /proc/net/dev 
1119   Inter-|Receive                                                   |[... 
1120    face |bytes    packets errs drop fifo frame compressed multicast|[... 
1121       lo:  908188   5596     0    0    0     0          0         0 [...         
1122     ppp0:15475140  20721   410    0    0   410          0         0 [...  
1123     eth0:  614530   7085     0    0    0     0          0         1 [... 
1124    
1125   ...] Transmit 
1126   ...] bytes    packets errs drop fifo colls carrier compressed 
1127   ...]  908188     5596    0    0    0     0       0          0 
1128   ...] 1375103    17405    0    0    0     0       0          0 
1129   ...] 1703981     5535    0    0    0     3       0          0 
1130 
1131 In addition, each Channel Bond interface has its own directory.  For
1132 example, the bond0 device will have a directory called /proc/net/bond0/.
1133 It will contain information that is specific to that bond, such as the
1134 current slaves of the bond, the link status of the slaves, and how
1135 many times the slaves link has failed.
1136 
1137 1.5 SCSI info
1138 -------------
1139 
1140 If you  have  a  SCSI  host adapter in your system, you'll find a subdirectory
1141 named after  the driver for this adapter in /proc/scsi. You'll also see a list
1142 of all recognized SCSI devices in /proc/scsi:
1143 
1144   >cat /proc/scsi/scsi 
1145   Attached devices: 
1146   Host: scsi0 Channel: 00 Id: 00 Lun: 00 
1147     Vendor: IBM      Model: DGHS09U          Rev: 03E0 
1148     Type:   Direct-Access                    ANSI SCSI revision: 03 
1149   Host: scsi0 Channel: 00 Id: 06 Lun: 00 
1150     Vendor: PIONEER  Model: CD-ROM DR-U06S   Rev: 1.04 
1151     Type:   CD-ROM                           ANSI SCSI revision: 02 
1152 
1153 
1154 The directory  named  after  the driver has one file for each adapter found in
1155 the system.  These  files  contain information about the controller, including
1156 the used  IRQ  and  the  IO  address range. The amount of information shown is
1157 dependent on  the adapter you use. The example shows the output for an Adaptec
1158 AHA-2940 SCSI adapter:
1159 
1160   > cat /proc/scsi/aic7xxx/0 
1161    
1162   Adaptec AIC7xxx driver version: 5.1.19/3.2.4 
1163   Compile Options: 
1164     TCQ Enabled By Default : Disabled 
1165     AIC7XXX_PROC_STATS     : Disabled 
1166     AIC7XXX_RESET_DELAY    : 5 
1167   Adapter Configuration: 
1168              SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 
1169                              Ultra Wide Controller 
1170       PCI MMAPed I/O Base: 0xeb001000 
1171    Adapter SEEPROM Config: SEEPROM found and used. 
1172         Adaptec SCSI BIOS: Enabled 
1173                       IRQ: 10 
1174                      SCBs: Active 0, Max Active 2, 
1175                            Allocated 15, HW 16, Page 255 
1176                Interrupts: 160328 
1177         BIOS Control Word: 0x18b6 
1178      Adapter Control Word: 0x005b 
1179      Extended Translation: Enabled 
1180   Disconnect Enable Flags: 0xffff 
1181        Ultra Enable Flags: 0x0001 
1182    Tag Queue Enable Flags: 0x0000 
1183   Ordered Queue Tag Flags: 0x0000 
1184   Default Tag Queue Depth: 8 
1185       Tagged Queue By Device array for aic7xxx host instance 0: 
1186         {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 
1187       Actual queue depth per device for aic7xxx host instance 0: 
1188         {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 
1189   Statistics: 
1190   (scsi0:0:0:0) 
1191     Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 
1192     Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 
1193     Total transfers 160151 (74577 reads and 85574 writes) 
1194   (scsi0:0:6:0) 
1195     Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 
1196     Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 
1197     Total transfers 0 (0 reads and 0 writes) 
1198 
1199 
1200 1.6 Parallel port info in /proc/parport
1201 ---------------------------------------
1202 
1203 The directory  /proc/parport  contains information about the parallel ports of
1204 your system.  It  has  one  subdirectory  for  each port, named after the port
1205 number (0,1,2,...).
1206 
1207 These directories contain the four files shown in Table 1-10.
1208 
1209 
1210 Table 1-10: Files in /proc/parport
1211 ..............................................................................
1212  File      Content                                                             
1213  autoprobe Any IEEE-1284 device ID information that has been acquired.         
1214  devices   list of the device drivers using that port. A + will appear by the
1215            name of the device currently using the port (it might not appear
1216            against any). 
1217  hardware  Parallel port's base address, IRQ line and DMA channel.             
1218  irq       IRQ that parport is using for that port. This is in a separate
1219            file to allow you to alter it by writing a new value in (IRQ
1220            number or none). 
1221 ..............................................................................
1222 
1223 1.7 TTY info in /proc/tty
1224 -------------------------
1225 
1226 Information about  the  available  and actually used tty's can be found in the
1227 directory /proc/tty.You'll  find  entries  for drivers and line disciplines in
1228 this directory, as shown in Table 1-11.
1229 
1230 
1231 Table 1-11: Files in /proc/tty
1232 ..............................................................................
1233  File          Content                                        
1234  drivers       list of drivers and their usage                
1235  ldiscs        registered line disciplines                    
1236  driver/serial usage statistic and status of single tty lines 
1237 ..............................................................................
1238 
1239 To see  which  tty's  are  currently in use, you can simply look into the file
1240 /proc/tty/drivers:
1241 
1242   > cat /proc/tty/drivers 
1243   pty_slave            /dev/pts      136   0-255 pty:slave 
1244   pty_master           /dev/ptm      128   0-255 pty:master 
1245   pty_slave            /dev/ttyp       3   0-255 pty:slave 
1246   pty_master           /dev/pty        2   0-255 pty:master 
1247   serial               /dev/cua        5   64-67 serial:callout 
1248   serial               /dev/ttyS       4   64-67 serial 
1249   /dev/tty0            /dev/tty0       4       0 system:vtmaster 
1250   /dev/ptmx            /dev/ptmx       5       2 system 
1251   /dev/console         /dev/console    5       1 system:console 
1252   /dev/tty             /dev/tty        5       0 system:/dev/tty 
1253   unknown              /dev/tty        4    1-63 console 
1254 
1255 
1256 1.8 Miscellaneous kernel statistics in /proc/stat
1257 -------------------------------------------------
1258 
1259 Various pieces   of  information about  kernel activity  are  available in the
1260 /proc/stat file.  All  of  the numbers reported  in  this file are  aggregates
1261 since the system first booted.  For a quick look, simply cat the file:
1262 
1263   > cat /proc/stat
1264   cpu  2255 34 2290 22625563 6290 127 456 0 0 0
1265   cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1266   cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1267   intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1268   ctxt 1990473
1269   btime 1062191376
1270   processes 2915
1271   procs_running 1
1272   procs_blocked 0
1273   softirq 183433 0 21755 12 39 1137 231 21459 2263
1274 
1275 The very first  "cpu" line aggregates the  numbers in all  of the other "cpuN"
1276 lines.  These numbers identify the amount of time the CPU has spent performing
1277 different kinds of work.  Time units are in USER_HZ (typically hundredths of a
1278 second).  The meanings of the columns are as follows, from left to right:
1279 
1280 - user: normal processes executing in user mode
1281 - nice: niced processes executing in user mode
1282 - system: processes executing in kernel mode
1283 - idle: twiddling thumbs
1284 - iowait: waiting for I/O to complete
1285 - irq: servicing interrupts
1286 - softirq: servicing softirqs
1287 - steal: involuntary wait
1288 - guest: running a normal guest
1289 - guest_nice: running a niced guest
1290 
1291 The "intr" line gives counts of interrupts  serviced since boot time, for each
1292 of the  possible system interrupts.   The first  column  is the  total of  all
1293 interrupts serviced  including  unnumbered  architecture specific  interrupts;
1294 each  subsequent column is the  total for that particular numbered interrupt.
1295 Unnumbered interrupts are not shown, only summed into the total.
1296 
1297 The "ctxt" line gives the total number of context switches across all CPUs.
1298 
1299 The "btime" line gives  the time at which the  system booted, in seconds since
1300 the Unix epoch.
1301 
1302 The "processes" line gives the number  of processes and threads created, which
1303 includes (but  is not limited  to) those  created by  calls to the  fork() and
1304 clone() system calls.
1305 
1306 The "procs_running" line gives the total number of threads that are
1307 running or ready to run (i.e., the total number of runnable threads).
1308 
1309 The   "procs_blocked" line gives  the  number of  processes currently blocked,
1310 waiting for I/O to complete.
1311 
1312 The "softirq" line gives counts of softirqs serviced since boot time, for each
1313 of the possible system softirqs. The first column is the total of all
1314 softirqs serviced; each subsequent column is the total for that particular
1315 softirq.
1316 
1317 
1318 1.9 Ext4 file system parameters
1319 -------------------------------
1320 
1321 Information about mounted ext4 file systems can be found in
1322 /proc/fs/ext4.  Each mounted filesystem will have a directory in
1323 /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1324 /proc/fs/ext4/dm-0).   The files in each per-device directory are shown
1325 in Table 1-12, below.
1326 
1327 Table 1-12: Files in /proc/fs/ext4/<devname>
1328 ..............................................................................
1329  File            Content                                        
1330  mb_groups       details of multiblock allocator buddy cache of free blocks
1331 ..............................................................................
1332 
1333 2.0 /proc/consoles
1334 ------------------
1335 Shows registered system console lines.
1336 
1337 To see which character device lines are currently used for the system console
1338 /dev/console, you may simply look into the file /proc/consoles:
1339 
1340   > cat /proc/consoles
1341   tty0                 -WU (ECp)       4:7
1342   ttyS0                -W- (Ep)        4:64
1343 
1344 The columns are:
1345 
1346   device               name of the device
1347   operations           R = can do read operations
1348                        W = can do write operations
1349                        U = can do unblank
1350   flags                E = it is enabled
1351                        C = it is preferred console
1352                        B = it is primary boot console
1353                        p = it is used for printk buffer
1354                        b = it is not a TTY but a Braille device
1355                        a = it is safe to use when cpu is offline
1356   major:minor          major and minor number of the device separated by a colon
1357 
1358 ------------------------------------------------------------------------------
1359 Summary
1360 ------------------------------------------------------------------------------
1361 The /proc file system serves information about the running system. It not only
1362 allows access to process data but also allows you to request the kernel status
1363 by reading files in the hierarchy.
1364 
1365 The directory  structure  of /proc reflects the types of information and makes
1366 it easy, if not obvious, where to look for specific data.
1367 ------------------------------------------------------------------------------
1368 
1369 ------------------------------------------------------------------------------
1370 CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1371 ------------------------------------------------------------------------------
1372 
1373 ------------------------------------------------------------------------------
1374 In This Chapter
1375 ------------------------------------------------------------------------------
1376 * Modifying kernel parameters by writing into files found in /proc/sys
1377 * Exploring the files which modify certain parameters
1378 * Review of the /proc/sys file tree
1379 ------------------------------------------------------------------------------
1380 
1381 
1382 A very  interesting part of /proc is the directory /proc/sys. This is not only
1383 a source  of  information,  it also allows you to change parameters within the
1384 kernel. Be  very  careful  when attempting this. You can optimize your system,
1385 but you  can  also  cause  it  to  crash.  Never  alter kernel parameters on a
1386 production system.  Set  up  a  development machine and test to make sure that
1387 everything works  the  way  you want it to. You may have no alternative but to
1388 reboot the machine once an error has been made.
1389 
1390 To change  a  value,  simply  echo  the new value into the file. An example is
1391 given below  in the section on the file system data. You need to be root to do
1392 this. You  can  create  your  own  boot script to perform this every time your
1393 system boots.
1394 
1395 The files  in /proc/sys can be used to fine tune and monitor miscellaneous and
1396 general things  in  the operation of the Linux kernel. Since some of the files
1397 can inadvertently  disrupt  your  system,  it  is  advisable  to  read  both
1398 documentation and  source  before actually making adjustments. In any case, be
1399 very careful  when  writing  to  any  of these files. The entries in /proc may
1400 change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1401 review the kernel documentation in the directory /usr/src/linux/Documentation.
1402 This chapter  is  heavily  based  on the documentation included in the pre 2.2
1403 kernels, and became part of it in version 2.2.1 of the Linux kernel.
1404 
1405 Please see: Documentation/sysctl/ directory for descriptions of these
1406 entries.
1407 
1408 ------------------------------------------------------------------------------
1409 Summary
1410 ------------------------------------------------------------------------------
1411 Certain aspects  of  kernel  behavior  can be modified at runtime, without the
1412 need to  recompile  the kernel, or even to reboot the system. The files in the
1413 /proc/sys tree  can  not only be read, but also modified. You can use the echo
1414 command to write value into these files, thereby changing the default settings
1415 of the kernel.
1416 ------------------------------------------------------------------------------
1417 
1418 ------------------------------------------------------------------------------
1419 CHAPTER 3: PER-PROCESS PARAMETERS
1420 ------------------------------------------------------------------------------
1421 
1422 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1423 --------------------------------------------------------------------------------
1424 
1425 These file can be used to adjust the badness heuristic used to select which
1426 process gets killed in out of memory conditions.
1427 
1428 The badness heuristic assigns a value to each candidate task ranging from 0
1429 (never kill) to 1000 (always kill) to determine which process is targeted.  The
1430 units are roughly a proportion along that range of allowed memory the process
1431 may allocate from based on an estimation of its current memory and swap use.
1432 For example, if a task is using all allowed memory, its badness score will be
1433 1000.  If it is using half of its allowed memory, its score will be 500.
1434 
1435 There is an additional factor included in the badness score: the current memory
1436 and swap usage is discounted by 3% for root processes.
1437 
1438 The amount of "allowed" memory depends on the context in which the oom killer
1439 was called.  If it is due to the memory assigned to the allocating task's cpuset
1440 being exhausted, the allowed memory represents the set of mems assigned to that
1441 cpuset.  If it is due to a mempolicy's node(s) being exhausted, the allowed
1442 memory represents the set of mempolicy nodes.  If it is due to a memory
1443 limit (or swap limit) being reached, the allowed memory is that configured
1444 limit.  Finally, if it is due to the entire system being out of memory, the
1445 allowed memory represents all allocatable resources.
1446 
1447 The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1448 is used to determine which task to kill.  Acceptable values range from -1000
1449 (OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX).  This allows userspace to
1450 polarize the preference for oom killing either by always preferring a certain
1451 task or completely disabling it.  The lowest possible value, -1000, is
1452 equivalent to disabling oom killing entirely for that task since it will always
1453 report a badness score of 0.
1454 
1455 Consequently, it is very simple for userspace to define the amount of memory to
1456 consider for each task.  Setting a /proc/<pid>/oom_score_adj value of +500, for
1457 example, is roughly equivalent to allowing the remainder of tasks sharing the
1458 same system, cpuset, mempolicy, or memory controller resources to use at least
1459 50% more memory.  A value of -500, on the other hand, would be roughly
1460 equivalent to discounting 50% of the task's allowed memory from being considered
1461 as scoring against the task.
1462 
1463 For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1464 be used to tune the badness score.  Its acceptable values range from -16
1465 (OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1466 (OOM_DISABLE) to disable oom killing entirely for that task.  Its value is
1467 scaled linearly with /proc/<pid>/oom_score_adj.
1468 
1469 The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1470 value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1471 requires CAP_SYS_RESOURCE.
1472 
1473 Caveat: when a parent task is selected, the oom killer will sacrifice any first
1474 generation children with separate address spaces instead, if possible.  This
1475 avoids servers and important system daemons from being killed and loses the
1476 minimal amount of work.
1477 
1478 
1479 3.2 /proc/<pid>/oom_score - Display current oom-killer score
1480 -------------------------------------------------------------
1481 
1482 This file can be used to check the current score used by the oom-killer is for
1483 any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1484 process should be killed in an out-of-memory situation.
1485 
1486 
1487 3.3  /proc/<pid>/io - Display the IO accounting fields
1488 -------------------------------------------------------
1489 
1490 This file contains IO statistics for each running process
1491 
1492 Example
1493 -------
1494 
1495 test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1496 [1] 3828
1497 
1498 test:/tmp # cat /proc/3828/io
1499 rchar: 323934931
1500 wchar: 323929600
1501 syscr: 632687
1502 syscw: 632675
1503 read_bytes: 0
1504 write_bytes: 323932160
1505 cancelled_write_bytes: 0
1506 
1507 
1508 Description
1509 -----------
1510 
1511 rchar
1512 -----
1513 
1514 I/O counter: chars read
1515 The number of bytes which this task has caused to be read from storage. This
1516 is simply the sum of bytes which this process passed to read() and pread().
1517 It includes things like tty IO and it is unaffected by whether or not actual
1518 physical disk IO was required (the read might have been satisfied from
1519 pagecache)
1520 
1521 
1522 wchar
1523 -----
1524 
1525 I/O counter: chars written
1526 The number of bytes which this task has caused, or shall cause to be written
1527 to disk. Similar caveats apply here as with rchar.
1528 
1529 
1530 syscr
1531 -----
1532 
1533 I/O counter: read syscalls
1534 Attempt to count the number of read I/O operations, i.e. syscalls like read()
1535 and pread().
1536 
1537 
1538 syscw
1539 -----
1540 
1541 I/O counter: write syscalls
1542 Attempt to count the number of write I/O operations, i.e. syscalls like
1543 write() and pwrite().
1544 
1545 
1546 read_bytes
1547 ----------
1548 
1549 I/O counter: bytes read
1550 Attempt to count the number of bytes which this process really did cause to
1551 be fetched from the storage layer. Done at the submit_bio() level, so it is
1552 accurate for block-backed filesystems. <please add status regarding NFS and
1553 CIFS at a later time>
1554 
1555 
1556 write_bytes
1557 -----------
1558 
1559 I/O counter: bytes written
1560 Attempt to count the number of bytes which this process caused to be sent to
1561 the storage layer. This is done at page-dirtying time.
1562 
1563 
1564 cancelled_write_bytes
1565 ---------------------
1566 
1567 The big inaccuracy here is truncate. If a process writes 1MB to a file and
1568 then deletes the file, it will in fact perform no writeout. But it will have
1569 been accounted as having caused 1MB of write.
1570 In other words: The number of bytes which this process caused to not happen,
1571 by truncating pagecache. A task can cause "negative" IO too. If this task
1572 truncates some dirty pagecache, some IO which another task has been accounted
1573 for (in its write_bytes) will not be happening. We _could_ just subtract that
1574 from the truncating task's write_bytes, but there is information loss in doing
1575 that.
1576 
1577 
1578 Note
1579 ----
1580 
1581 At its current implementation state, this is a bit racy on 32-bit machines: if
1582 process A reads process B's /proc/pid/io while process B is updating one of
1583 those 64-bit counters, process A could see an intermediate result.
1584 
1585 
1586 More information about this can be found within the taskstats documentation in
1587 Documentation/accounting.
1588 
1589 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1590 ---------------------------------------------------------------
1591 When a process is dumped, all anonymous memory is written to a core file as
1592 long as the size of the core file isn't limited. But sometimes we don't want
1593 to dump some memory segments, for example, huge shared memory. Conversely,
1594 sometimes we want to save file-backed memory segments into a core file, not
1595 only the individual files.
1596 
1597 /proc/<pid>/coredump_filter allows you to customize which memory segments
1598 will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1599 of memory types. If a bit of the bitmask is set, memory segments of the
1600 corresponding memory type are dumped, otherwise they are not dumped.
1601 
1602 The following 7 memory types are supported:
1603   - (bit 0) anonymous private memory
1604   - (bit 1) anonymous shared memory
1605   - (bit 2) file-backed private memory
1606   - (bit 3) file-backed shared memory
1607   - (bit 4) ELF header pages in file-backed private memory areas (it is
1608             effective only if the bit 2 is cleared)
1609   - (bit 5) hugetlb private memory
1610   - (bit 6) hugetlb shared memory
1611 
1612   Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1613   are always dumped regardless of the bitmask status.
1614 
1615   Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
1616   effected by bit 5-6.
1617 
1618 Default value of coredump_filter is 0x23; this means all anonymous memory
1619 segments and hugetlb private memory are dumped.
1620 
1621 If you don't want to dump all shared memory segments attached to pid 1234,
1622 write 0x21 to the process's proc file.
1623 
1624   $ echo 0x21 > /proc/1234/coredump_filter
1625 
1626 When a new process is created, the process inherits the bitmask status from its
1627 parent. It is useful to set up coredump_filter before the program runs.
1628 For example:
1629 
1630   $ echo 0x7 > /proc/self/coredump_filter
1631   $ ./some_program
1632 
1633 3.5     /proc/<pid>/mountinfo - Information about mounts
1634 --------------------------------------------------------
1635 
1636 This file contains lines of the form:
1637 
1638 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1639 (1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
1640 
1641 (1) mount ID:  unique identifier of the mount (may be reused after umount)
1642 (2) parent ID:  ID of parent (or of self for the top of the mount tree)
1643 (3) major:minor:  value of st_dev for files on filesystem
1644 (4) root:  root of the mount within the filesystem
1645 (5) mount point:  mount point relative to the process's root
1646 (6) mount options:  per mount options
1647 (7) optional fields:  zero or more fields of the form "tag[:value]"
1648 (8) separator:  marks the end of the optional fields
1649 (9) filesystem type:  name of filesystem of the form "type[.subtype]"
1650 (10) mount source:  filesystem specific information or "none"
1651 (11) super options:  per super block options
1652 
1653 Parsers should ignore all unrecognised optional fields.  Currently the
1654 possible optional fields are:
1655 
1656 shared:X  mount is shared in peer group X
1657 master:X  mount is slave to peer group X
1658 propagate_from:X  mount is slave and receives propagation from peer group X (*)
1659 unbindable  mount is unbindable
1660 
1661 (*) X is the closest dominant peer group under the process's root.  If
1662 X is the immediate master of the mount, or if there's no dominant peer
1663 group under the same root, then only the "master:X" field is present
1664 and not the "propagate_from:X" field.
1665 
1666 For more information on mount propagation see:
1667 
1668   Documentation/filesystems/sharedsubtree.txt
1669 
1670 
1671 3.6     /proc/<pid>/comm  & /proc/<pid>/task/<tid>/comm
1672 --------------------------------------------------------
1673 These files provide a method to access a tasks comm value. It also allows for
1674 a task to set its own or one of its thread siblings comm value. The comm value
1675 is limited in size compared to the cmdline value, so writing anything longer
1676 then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1677 comm value.
1678 
1679 
1680 3.7     /proc/<pid>/task/<tid>/children - Information about task children
1681 -------------------------------------------------------------------------
1682 This file provides a fast way to retrieve first level children pids
1683 of a task pointed by <pid>/<tid> pair. The format is a space separated
1684 stream of pids.
1685 
1686 Note the "first level" here -- if a child has own children they will
1687 not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1688 to obtain the descendants.
1689 
1690 Since this interface is intended to be fast and cheap it doesn't
1691 guarantee to provide precise results and some children might be
1692 skipped, especially if they've exited right after we printed their
1693 pids, so one need to either stop or freeze processes being inspected
1694 if precise results are needed.
1695 
1696 
1697 3.8     /proc/<pid>/fdinfo/<fd> - Information about opened file
1698 ---------------------------------------------------------------
1699 This file provides information associated with an opened file. The regular
1700 files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1701 represents the current offset of the opened file in decimal form [see lseek(2)
1702 for details], 'flags' denotes the octal O_xxx mask the file has been
1703 created with [see open(2) for details] and 'mnt_id' represents mount ID of
1704 the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1705 for details].
1706 
1707 A typical output is
1708 
1709         pos:    0
1710         flags:  0100002
1711         mnt_id: 19
1712 
1713 All locks associated with a file descriptor are shown in its fdinfo too.
1714 
1715 lock:       1: FLOCK  ADVISORY  WRITE 359 00:13:11691 0 EOF
1716 
1717 The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1718 pair provide additional information particular to the objects they represent.
1719 
1720         Eventfd files
1721         ~~~~~~~~~~~~~
1722         pos:    0
1723         flags:  04002
1724         mnt_id: 9
1725         eventfd-count:  5a
1726 
1727         where 'eventfd-count' is hex value of a counter.
1728 
1729         Signalfd files
1730         ~~~~~~~~~~~~~~
1731         pos:    0
1732         flags:  04002
1733         mnt_id: 9
1734         sigmask:        0000000000000200
1735 
1736         where 'sigmask' is hex value of the signal mask associated
1737         with a file.
1738 
1739         Epoll files
1740         ~~~~~~~~~~~
1741         pos:    0
1742         flags:  02
1743         mnt_id: 9
1744         tfd:        5 events:       1d data: ffffffffffffffff
1745 
1746         where 'tfd' is a target file descriptor number in decimal form,
1747         'events' is events mask being watched and the 'data' is data
1748         associated with a target [see epoll(7) for more details].
1749 
1750         Fsnotify files
1751         ~~~~~~~~~~~~~~
1752         For inotify files the format is the following
1753 
1754         pos:    0
1755         flags:  02000000
1756         inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1757 
1758         where 'wd' is a watch descriptor in decimal form, ie a target file
1759         descriptor number, 'ino' and 'sdev' are inode and device where the
1760         target file resides and the 'mask' is the mask of events, all in hex
1761         form [see inotify(7) for more details].
1762 
1763         If the kernel was built with exportfs support, the path to the target
1764         file is encoded as a file handle.  The file handle is provided by three
1765         fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1766         format.
1767 
1768         If the kernel is built without exportfs support the file handle won't be
1769         printed out.
1770 
1771         If there is no inotify mark attached yet the 'inotify' line will be omitted.
1772 
1773         For fanotify files the format is
1774 
1775         pos:    0
1776         flags:  02
1777         mnt_id: 9
1778         fanotify flags:10 event-flags:0
1779         fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1780         fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1781 
1782         where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1783         call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1784         flags associated with mark which are tracked separately from events
1785         mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1786         mask and 'ignored_mask' is the mask of events which are to be ignored.
1787         All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1788         does provide information about flags and mask used in fanotify_mark
1789         call [see fsnotify manpage for details].
1790 
1791         While the first three lines are mandatory and always printed, the rest is
1792         optional and may be omitted if no marks created yet.
1793 
1794         Timerfd files
1795         ~~~~~~~~~~~~~
1796 
1797         pos:    0
1798         flags:  02
1799         mnt_id: 9
1800         clockid: 0
1801         ticks: 0
1802         settime flags: 01
1803         it_value: (0, 49406829)
1804         it_interval: (1, 0)
1805 
1806         where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
1807         that have occurred [see timerfd_create(2) for details]. 'settime flags' are
1808         flags in octal form been used to setup the timer [see timerfd_settime(2) for
1809         details]. 'it_value' is remaining time until the timer exiration.
1810         'it_interval' is the interval for the timer. Note the timer might be set up
1811         with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
1812         still exhibits timer's remaining time.
1813 
1814 3.9     /proc/<pid>/map_files - Information about memory mapped files
1815 ---------------------------------------------------------------------
1816 This directory contains symbolic links which represent memory mapped files
1817 the process is maintaining.  Example output:
1818 
1819      | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
1820      | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
1821      | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
1822      | ...
1823      | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
1824      | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
1825 
1826 The name of a link represents the virtual memory bounds of a mapping, i.e.
1827 vm_area_struct::vm_start-vm_area_struct::vm_end.
1828 
1829 The main purpose of the map_files is to retrieve a set of memory mapped
1830 files in a fast way instead of parsing /proc/<pid>/maps or
1831 /proc/<pid>/smaps, both of which contain many more records.  At the same
1832 time one can open(2) mappings from the listings of two processes and
1833 comparing their inode numbers to figure out which anonymous memory areas
1834 are actually shared.
1835 
1836 ------------------------------------------------------------------------------
1837 Configuring procfs
1838 ------------------------------------------------------------------------------
1839 
1840 4.1     Mount options
1841 ---------------------
1842 
1843 The following mount options are supported:
1844 
1845         hidepid=        Set /proc/<pid>/ access mode.
1846         gid=            Set the group authorized to learn processes information.
1847 
1848 hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1849 (default).
1850 
1851 hidepid=1 means users may not access any /proc/<pid>/ directories but their
1852 own.  Sensitive files like cmdline, sched*, status are now protected against
1853 other users.  This makes it impossible to learn whether any user runs
1854 specific program (given the program doesn't reveal itself by its behaviour).
1855 As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1856 poorly written programs passing sensitive information via program arguments are
1857 now protected against local eavesdroppers.
1858 
1859 hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1860 users.  It doesn't mean that it hides a fact whether a process with a specific
1861 pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1862 but it hides process' uid and gid, which may be learned by stat()'ing
1863 /proc/<pid>/ otherwise.  It greatly complicates an intruder's task of gathering
1864 information about running processes, whether some daemon runs with elevated
1865 privileges, whether other user runs some sensitive program, whether other users
1866 run any program at all, etc.
1867 
1868 gid= defines a group authorized to learn processes information otherwise
1869 prohibited by hidepid=.  If you use some daemon like identd which needs to learn
1870 information about processes information, just add identd to this group.

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