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Based on kernel version 4.15. Page generated on 2018-01-29 10:00 EST.

1	------------------------------------------------------------------------------
2	                       T H E  /proc   F I L E S Y S T E M
3	------------------------------------------------------------------------------
4	/proc/sys         Terrehon Bowden <terrehon@pacbell.net>        October 7 1999
5	                  Bodo Bauer <bb@ricochet.net>
6	
7	2.4.x update	  Jorge Nerin <comandante@zaralinux.com>      November 14 2000
8	move /proc/sys	  Shen Feng <shen@cn.fujitsu.com>		  April 1 2009
9	------------------------------------------------------------------------------
10	Version 1.3                                              Kernel version 2.2.12
11						      Kernel version 2.4.0-test11-pre4
12	------------------------------------------------------------------------------
13	fixes/update part 1.1  Stefani Seibold <stefani@seibold.net>       June 9 2009
14	
15	Table of Contents
16	-----------------
17	
18	  0     Preface
19	  0.1	Introduction/Credits
20	  0.2	Legal Stuff
21	
22	  1	Collecting System Information
23	  1.1	Process-Specific Subdirectories
24	  1.2	Kernel data
25	  1.3	IDE devices in /proc/ide
26	  1.4	Networking info in /proc/net
27	  1.5	SCSI info
28	  1.6	Parallel port info in /proc/parport
29	  1.7	TTY info in /proc/tty
30	  1.8	Miscellaneous kernel statistics in /proc/stat
31	  1.9	Ext4 file system parameters
32	
33	  2	Modifying System Parameters
34	
35	  3	Per-Process Parameters
36	  3.1	/proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
37									score
38	  3.2	/proc/<pid>/oom_score - Display current oom-killer score
39	  3.3	/proc/<pid>/io - Display the IO accounting fields
40	  3.4	/proc/<pid>/coredump_filter - Core dump filtering settings
41	  3.5	/proc/<pid>/mountinfo - Information about mounts
42	  3.6	/proc/<pid>/comm  & /proc/<pid>/task/<tid>/comm
43	  3.7   /proc/<pid>/task/<tid>/children - Information about task children
44	  3.8   /proc/<pid>/fdinfo/<fd> - Information about opened file
45	  3.9   /proc/<pid>/map_files - Information about memory mapped files
46	  3.10  /proc/<pid>/timerslack_ns - Task timerslack value
47	  3.11	/proc/<pid>/patch_state - Livepatch patch operation state
48	
49	  4	Configuring procfs
50	  4.1	Mount options
51	
52	------------------------------------------------------------------------------
53	Preface
54	------------------------------------------------------------------------------
55	
56	0.1 Introduction/Credits
57	------------------------
58	
59	This documentation is  part of a soon (or  so we hope) to be  released book on
60	the SuSE  Linux distribution. As  there is  no complete documentation  for the
61	/proc file system and we've used  many freely available sources to write these
62	chapters, it  seems only fair  to give the work  back to the  Linux community.
63	This work is  based on the 2.2.*  kernel version and the  upcoming 2.4.*. I'm
64	afraid it's still far from complete, but we  hope it will be useful. As far as
65	we know, it is the first 'all-in-one' document about the /proc file system. It
66	is focused  on the Intel  x86 hardware,  so if you  are looking for  PPC, ARM,
67	SPARC, AXP, etc., features, you probably  won't find what you are looking for.
68	It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
69	additions and patches  are welcome and will  be added to this  document if you
70	mail them to Bodo.
71	
72	We'd like  to  thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
73	other people for help compiling this documentation. We'd also like to extend a
74	special thank  you to Andi Kleen for documentation, which we relied on heavily
75	to create  this  document,  as well as the additional information he provided.
76	Thanks to  everybody  else  who contributed source or docs to the Linux kernel
77	and helped create a great piece of software... :)
78	
79	If you  have  any comments, corrections or additions, please don't hesitate to
80	contact Bodo  Bauer  at  bb@ricochet.net.  We'll  be happy to add them to this
81	document.
82	
83	The   latest   version    of   this   document   is    available   online   at
84	http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
85	
86	If  the above  direction does  not works  for you,  you could  try the  kernel
87	mailing  list  at  linux-kernel@vger.kernel.org  and/or try  to  reach  me  at
88	comandante@zaralinux.com.
89	
90	0.2 Legal Stuff
91	---------------
92	
93	We don't  guarantee  the  correctness  of this document, and if you come to us
94	complaining about  how  you  screwed  up  your  system  because  of  incorrect
95	documentation, we won't feel responsible...
96	
97	------------------------------------------------------------------------------
98	CHAPTER 1: COLLECTING SYSTEM INFORMATION
99	------------------------------------------------------------------------------
100	
101	------------------------------------------------------------------------------
102	In This Chapter
103	------------------------------------------------------------------------------
104	* Investigating  the  properties  of  the  pseudo  file  system  /proc and its
105	  ability to provide information on the running Linux system
106	* Examining /proc's structure
107	* Uncovering  various  information  about the kernel and the processes running
108	  on the system
109	------------------------------------------------------------------------------
110	
111	
112	The proc  file  system acts as an interface to internal data structures in the
113	kernel. It  can  be  used to obtain information about the system and to change
114	certain kernel parameters at runtime (sysctl).
115	
116	First, we'll  take  a  look  at the read-only parts of /proc. In Chapter 2, we
117	show you how you can use /proc/sys to change settings.
118	
119	1.1 Process-Specific Subdirectories
120	-----------------------------------
121	
122	The directory  /proc  contains  (among other things) one subdirectory for each
123	process running on the system, which is named after the process ID (PID).
124	
125	The link  self  points  to  the  process reading the file system. Each process
126	subdirectory has the entries listed in Table 1-1.
127	
128	
129	Table 1-1: Process specific entries in /proc
130	..............................................................................
131	 File		Content
132	 clear_refs	Clears page referenced bits shown in smaps output
133	 cmdline	Command line arguments
134	 cpu		Current and last cpu in which it was executed	(2.4)(smp)
135	 cwd		Link to the current working directory
136	 environ	Values of environment variables
137	 exe		Link to the executable of this process
138	 fd		Directory, which contains all file descriptors
139	 maps		Memory maps to executables and library files	(2.4)
140	 mem		Memory held by this process
141	 root		Link to the root directory of this process
142	 stat		Process status
143	 statm		Process memory status information
144	 status		Process status in human readable form
145	 wchan		Present with CONFIG_KALLSYMS=y: it shows the kernel function
146			symbol the task is blocked in - or "0" if not blocked.
147	 pagemap	Page table
148	 stack		Report full stack trace, enable via CONFIG_STACKTRACE
149	 smaps		an extension based on maps, showing the memory consumption of
150			each mapping and flags associated with it
151	 numa_maps	an extension based on maps, showing the memory locality and
152			binding policy as well as mem usage (in pages) of each mapping.
153	..............................................................................
154	
155	For example, to get the status information of a process, all you have to do is
156	read the file /proc/PID/status:
157	
158	  >cat /proc/self/status
159	  Name:   cat
160	  State:  R (running)
161	  Tgid:   5452
162	  Pid:    5452
163	  PPid:   743
164	  TracerPid:      0						(2.4)
165	  Uid:    501     501     501     501
166	  Gid:    100     100     100     100
167	  FDSize: 256
168	  Groups: 100 14 16
169	  VmPeak:     5004 kB
170	  VmSize:     5004 kB
171	  VmLck:         0 kB
172	  VmHWM:       476 kB
173	  VmRSS:       476 kB
174	  RssAnon:             352 kB
175	  RssFile:             120 kB
176	  RssShmem:              4 kB
177	  VmData:      156 kB
178	  VmStk:        88 kB
179	  VmExe:        68 kB
180	  VmLib:      1412 kB
181	  VmPTE:        20 kb
182	  VmSwap:        0 kB
183	  HugetlbPages:          0 kB
184	  CoreDumping:    0
185	  Threads:        1
186	  SigQ:   0/28578
187	  SigPnd: 0000000000000000
188	  ShdPnd: 0000000000000000
189	  SigBlk: 0000000000000000
190	  SigIgn: 0000000000000000
191	  SigCgt: 0000000000000000
192	  CapInh: 00000000fffffeff
193	  CapPrm: 0000000000000000
194	  CapEff: 0000000000000000
195	  CapBnd: ffffffffffffffff
196	  NoNewPrivs:     0
197	  Seccomp:        0
198	  voluntary_ctxt_switches:        0
199	  nonvoluntary_ctxt_switches:     1
200	
201	This shows you nearly the same information you would get if you viewed it with
202	the ps  command.  In  fact,  ps  uses  the  proc  file  system  to  obtain its
203	information.  But you get a more detailed  view of the  process by reading the
204	file /proc/PID/status. It fields are described in table 1-2.
205	
206	The  statm  file  contains  more  detailed  information about the process
207	memory usage. Its seven fields are explained in Table 1-3.  The stat file
208	contains details information about the process itself.  Its fields are
209	explained in Table 1-4.
210	
211	(for SMP CONFIG users)
212	For making accounting scalable, RSS related information are handled in an
213	asynchronous manner and the value may not be very precise. To see a precise
214	snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
215	It's slow but very precise.
216	
217	Table 1-2: Contents of the status files (as of 4.8)
218	..............................................................................
219	 Field                       Content
220	 Name                        filename of the executable
221	 Umask                       file mode creation mask
222	 State                       state (R is running, S is sleeping, D is sleeping
223	                             in an uninterruptible wait, Z is zombie,
224				     T is traced or stopped)
225	 Tgid                        thread group ID
226	 Ngid                        NUMA group ID (0 if none)
227	 Pid                         process id
228	 PPid                        process id of the parent process
229	 TracerPid                   PID of process tracing this process (0 if not)
230	 Uid                         Real, effective, saved set, and  file system UIDs
231	 Gid                         Real, effective, saved set, and  file system GIDs
232	 FDSize                      number of file descriptor slots currently allocated
233	 Groups                      supplementary group list
234	 NStgid                      descendant namespace thread group ID hierarchy
235	 NSpid                       descendant namespace process ID hierarchy
236	 NSpgid                      descendant namespace process group ID hierarchy
237	 NSsid                       descendant namespace session ID hierarchy
238	 VmPeak                      peak virtual memory size
239	 VmSize                      total program size
240	 VmLck                       locked memory size
241	 VmPin                       pinned memory size
242	 VmHWM                       peak resident set size ("high water mark")
243	 VmRSS                       size of memory portions. It contains the three
244	                             following parts (VmRSS = RssAnon + RssFile + RssShmem)
245	 RssAnon                     size of resident anonymous memory
246	 RssFile                     size of resident file mappings
247	 RssShmem                    size of resident shmem memory (includes SysV shm,
248	                             mapping of tmpfs and shared anonymous mappings)
249	 VmData                      size of private data segments
250	 VmStk                       size of stack segments
251	 VmExe                       size of text segment
252	 VmLib                       size of shared library code
253	 VmPTE                       size of page table entries
254	 VmSwap                      amount of swap used by anonymous private data
255	                             (shmem swap usage is not included)
256	 HugetlbPages                size of hugetlb memory portions
257	 CoreDumping                 process's memory is currently being dumped
258	                             (killing the process may lead to a corrupted core)
259	 Threads                     number of threads
260	 SigQ                        number of signals queued/max. number for queue
261	 SigPnd                      bitmap of pending signals for the thread
262	 ShdPnd                      bitmap of shared pending signals for the process
263	 SigBlk                      bitmap of blocked signals
264	 SigIgn                      bitmap of ignored signals
265	 SigCgt                      bitmap of caught signals
266	 CapInh                      bitmap of inheritable capabilities
267	 CapPrm                      bitmap of permitted capabilities
268	 CapEff                      bitmap of effective capabilities
269	 CapBnd                      bitmap of capabilities bounding set
270	 NoNewPrivs                  no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
271	 Seccomp                     seccomp mode, like prctl(PR_GET_SECCOMP, ...)
272	 Cpus_allowed                mask of CPUs on which this process may run
273	 Cpus_allowed_list           Same as previous, but in "list format"
274	 Mems_allowed                mask of memory nodes allowed to this process
275	 Mems_allowed_list           Same as previous, but in "list format"
276	 voluntary_ctxt_switches     number of voluntary context switches
277	 nonvoluntary_ctxt_switches  number of non voluntary context switches
278	..............................................................................
279	
280	Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
281	..............................................................................
282	 Field    Content
283	 size     total program size (pages)		(same as VmSize in status)
284	 resident size of memory portions (pages)	(same as VmRSS in status)
285	 shared   number of pages that are shared	(i.e. backed by a file, same
286							as RssFile+RssShmem in status)
287	 trs      number of pages that are 'code'	(not including libs; broken,
288								includes data segment)
289	 lrs      number of pages of library		(always 0 on 2.6)
290	 drs      number of pages of data/stack		(including libs; broken,
291								includes library text)
292	 dt       number of dirty pages			(always 0 on 2.6)
293	..............................................................................
294	
295	
296	Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
297	..............................................................................
298	 Field          Content
299	  pid           process id
300	  tcomm         filename of the executable
301	  state         state (R is running, S is sleeping, D is sleeping in an
302	                uninterruptible wait, Z is zombie, T is traced or stopped)
303	  ppid          process id of the parent process
304	  pgrp          pgrp of the process
305	  sid           session id
306	  tty_nr        tty the process uses
307	  tty_pgrp      pgrp of the tty
308	  flags         task flags
309	  min_flt       number of minor faults
310	  cmin_flt      number of minor faults with child's
311	  maj_flt       number of major faults
312	  cmaj_flt      number of major faults with child's
313	  utime         user mode jiffies
314	  stime         kernel mode jiffies
315	  cutime        user mode jiffies with child's
316	  cstime        kernel mode jiffies with child's
317	  priority      priority level
318	  nice          nice level
319	  num_threads   number of threads
320	  it_real_value	(obsolete, always 0)
321	  start_time    time the process started after system boot
322	  vsize         virtual memory size
323	  rss           resident set memory size
324	  rsslim        current limit in bytes on the rss
325	  start_code    address above which program text can run
326	  end_code      address below which program text can run
327	  start_stack   address of the start of the main process stack
328	  esp           current value of ESP
329	  eip           current value of EIP
330	  pending       bitmap of pending signals
331	  blocked       bitmap of blocked signals
332	  sigign        bitmap of ignored signals
333	  sigcatch      bitmap of caught signals
334	  0		(place holder, used to be the wchan address, use /proc/PID/wchan instead)
335	  0             (place holder)
336	  0             (place holder)
337	  exit_signal   signal to send to parent thread on exit
338	  task_cpu      which CPU the task is scheduled on
339	  rt_priority   realtime priority
340	  policy        scheduling policy (man sched_setscheduler)
341	  blkio_ticks   time spent waiting for block IO
342	  gtime         guest time of the task in jiffies
343	  cgtime        guest time of the task children in jiffies
344	  start_data    address above which program data+bss is placed
345	  end_data      address below which program data+bss is placed
346	  start_brk     address above which program heap can be expanded with brk()
347	  arg_start     address above which program command line is placed
348	  arg_end       address below which program command line is placed
349	  env_start     address above which program environment is placed
350	  env_end       address below which program environment is placed
351	  exit_code     the thread's exit_code in the form reported by the waitpid system call
352	..............................................................................
353	
354	The /proc/PID/maps file containing the currently mapped memory regions and
355	their access permissions.
356	
357	The format is:
358	
359	address           perms offset  dev   inode      pathname
360	
361	08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
362	08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
363	0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
364	a7cb1000-a7cb2000 ---p 00000000 00:00 0
365	a7cb2000-a7eb2000 rw-p 00000000 00:00 0
366	a7eb2000-a7eb3000 ---p 00000000 00:00 0
367	a7eb3000-a7ed5000 rw-p 00000000 00:00 0
368	a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
369	a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
370	a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
371	a800b000-a800e000 rw-p 00000000 00:00 0
372	a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
373	a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
374	a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
375	a8024000-a8027000 rw-p 00000000 00:00 0
376	a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
377	a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
378	a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
379	aff35000-aff4a000 rw-p 00000000 00:00 0          [stack]
380	ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
381	
382	where "address" is the address space in the process that it occupies, "perms"
383	is a set of permissions:
384	
385	 r = read
386	 w = write
387	 x = execute
388	 s = shared
389	 p = private (copy on write)
390	
391	"offset" is the offset into the mapping, "dev" is the device (major:minor), and
392	"inode" is the inode  on that device.  0 indicates that  no inode is associated
393	with the memory region, as the case would be with BSS (uninitialized data).
394	The "pathname" shows the name associated file for this mapping.  If the mapping
395	is not associated with a file:
396	
397	 [heap]                   = the heap of the program
398	 [stack]                  = the stack of the main process
399	 [vdso]                   = the "virtual dynamic shared object",
400	                            the kernel system call handler
401	
402	 or if empty, the mapping is anonymous.
403	
404	The /proc/PID/smaps is an extension based on maps, showing the memory
405	consumption for each of the process's mappings. For each of mappings there
406	is a series of lines such as the following:
407	
408	08048000-080bc000 r-xp 00000000 03:02 13130      /bin/bash
409	Size:               1084 kB
410	Rss:                 892 kB
411	Pss:                 374 kB
412	Shared_Clean:        892 kB
413	Shared_Dirty:          0 kB
414	Private_Clean:         0 kB
415	Private_Dirty:         0 kB
416	Referenced:          892 kB
417	Anonymous:             0 kB
418	LazyFree:              0 kB
419	AnonHugePages:         0 kB
420	ShmemPmdMapped:        0 kB
421	Shared_Hugetlb:        0 kB
422	Private_Hugetlb:       0 kB
423	Swap:                  0 kB
424	SwapPss:               0 kB
425	KernelPageSize:        4 kB
426	MMUPageSize:           4 kB
427	Locked:                0 kB
428	VmFlags: rd ex mr mw me dw
429	
430	the first of these lines shows the same information as is displayed for the
431	mapping in /proc/PID/maps.  The remaining lines show the size of the mapping
432	(size), the amount of the mapping that is currently resident in RAM (RSS), the
433	process' proportional share of this mapping (PSS), the number of clean and
434	dirty private pages in the mapping.
435	
436	The "proportional set size" (PSS) of a process is the count of pages it has
437	in memory, where each page is divided by the number of processes sharing it.
438	So if a process has 1000 pages all to itself, and 1000 shared with one other
439	process, its PSS will be 1500.
440	Note that even a page which is part of a MAP_SHARED mapping, but has only
441	a single pte mapped, i.e.  is currently used by only one process, is accounted
442	as private and not as shared.
443	"Referenced" indicates the amount of memory currently marked as referenced or
444	accessed.
445	"Anonymous" shows the amount of memory that does not belong to any file.  Even
446	a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
447	and a page is modified, the file page is replaced by a private anonymous copy.
448	"LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE).
449	The memory isn't freed immediately with madvise(). It's freed in memory
450	pressure if the memory is clean. Please note that the printed value might
451	be lower than the real value due to optimizations used in the current
452	implementation. If this is not desirable please file a bug report.
453	"AnonHugePages" shows the ammount of memory backed by transparent hugepage.
454	"ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by
455	huge pages.
456	"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
457	hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
458	reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
459	"Swap" shows how much would-be-anonymous memory is also used, but out on swap.
460	For shmem mappings, "Swap" includes also the size of the mapped (and not
461	replaced by copy-on-write) part of the underlying shmem object out on swap.
462	"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
463	does not take into account swapped out page of underlying shmem objects.
464	"Locked" indicates whether the mapping is locked in memory or not.
465	
466	"VmFlags" field deserves a separate description. This member represents the kernel
467	flags associated with the particular virtual memory area in two letter encoded
468	manner. The codes are the following:
469	    rd  - readable
470	    wr  - writeable
471	    ex  - executable
472	    sh  - shared
473	    mr  - may read
474	    mw  - may write
475	    me  - may execute
476	    ms  - may share
477	    gd  - stack segment growns down
478	    pf  - pure PFN range
479	    dw  - disabled write to the mapped file
480	    lo  - pages are locked in memory
481	    io  - memory mapped I/O area
482	    sr  - sequential read advise provided
483	    rr  - random read advise provided
484	    dc  - do not copy area on fork
485	    de  - do not expand area on remapping
486	    ac  - area is accountable
487	    nr  - swap space is not reserved for the area
488	    ht  - area uses huge tlb pages
489	    ar  - architecture specific flag
490	    dd  - do not include area into core dump
491	    sd  - soft-dirty flag
492	    mm  - mixed map area
493	    hg  - huge page advise flag
494	    nh  - no-huge page advise flag
495	    mg  - mergable advise flag
496	
497	Note that there is no guarantee that every flag and associated mnemonic will
498	be present in all further kernel releases. Things get changed, the flags may
499	be vanished or the reverse -- new added.
500	
501	This file is only present if the CONFIG_MMU kernel configuration option is
502	enabled.
503	
504	Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent
505	output can be achieved only in the single read call).
506	This typically manifests when doing partial reads of these files while the
507	memory map is being modified.  Despite the races, we do provide the following
508	guarantees:
509	
510	1) The mapped addresses never go backwards, which implies no two
511	   regions will ever overlap.
512	2) If there is something at a given vaddr during the entirety of the
513	   life of the smaps/maps walk, there will be some output for it.
514	
515	
516	The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
517	bits on both physical and virtual pages associated with a process, and the
518	soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details).
519	To clear the bits for all the pages associated with the process
520	    > echo 1 > /proc/PID/clear_refs
521	
522	To clear the bits for the anonymous pages associated with the process
523	    > echo 2 > /proc/PID/clear_refs
524	
525	To clear the bits for the file mapped pages associated with the process
526	    > echo 3 > /proc/PID/clear_refs
527	
528	To clear the soft-dirty bit
529	    > echo 4 > /proc/PID/clear_refs
530	
531	To reset the peak resident set size ("high water mark") to the process's
532	current value:
533	    > echo 5 > /proc/PID/clear_refs
534	
535	Any other value written to /proc/PID/clear_refs will have no effect.
536	
537	The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
538	using /proc/kpageflags and number of times a page is mapped using
539	/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
540	
541	The /proc/pid/numa_maps is an extension based on maps, showing the memory
542	locality and binding policy, as well as the memory usage (in pages) of
543	each mapping. The output follows a general format where mapping details get
544	summarized separated by blank spaces, one mapping per each file line:
545	
546	address   policy    mapping details
547	
548	00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
549	00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
550	3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
551	320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
552	3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
553	3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
554	3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
555	320698b000 default file=/lib64/libc-2.12.so
556	3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
557	3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
558	3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
559	7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
560	7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
561	7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
562	7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
563	7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
564	
565	Where:
566	"address" is the starting address for the mapping;
567	"policy" reports the NUMA memory policy set for the mapping (see vm/numa_memory_policy.txt);
568	"mapping details" summarizes mapping data such as mapping type, page usage counters,
569	node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
570	size, in KB, that is backing the mapping up.
571	
572	1.2 Kernel data
573	---------------
574	
575	Similar to  the  process entries, the kernel data files give information about
576	the running kernel. The files used to obtain this information are contained in
577	/proc and  are  listed  in Table 1-5. Not all of these will be present in your
578	system. It  depends  on the kernel configuration and the loaded modules, which
579	files are there, and which are missing.
580	
581	Table 1-5: Kernel info in /proc
582	..............................................................................
583	 File        Content                                           
584	 apm         Advanced power management info                    
585	 buddyinfo   Kernel memory allocator information (see text)	(2.5)
586	 bus         Directory containing bus specific information     
587	 cmdline     Kernel command line                               
588	 cpuinfo     Info about the CPU                                
589	 devices     Available devices (block and character)           
590	 dma         Used DMS channels                                 
591	 filesystems Supported filesystems                             
592	 driver	     Various drivers grouped here, currently rtc (2.4)
593	 execdomains Execdomains, related to security			(2.4)
594	 fb	     Frame Buffer devices				(2.4)
595	 fs	     File system parameters, currently nfs/exports	(2.4)
596	 ide         Directory containing info about the IDE subsystem 
597	 interrupts  Interrupt usage                                   
598	 iomem	     Memory map						(2.4)
599	 ioports     I/O port usage                                    
600	 irq	     Masks for irq to cpu affinity			(2.4)(smp?)
601	 isapnp	     ISA PnP (Plug&Play) Info				(2.4)
602	 kcore       Kernel core image (can be ELF or A.OUT(deprecated in 2.4))   
603	 kmsg        Kernel messages                                   
604	 ksyms       Kernel symbol table                               
605	 loadavg     Load average of last 1, 5 & 15 minutes                
606	 locks       Kernel locks                                      
607	 meminfo     Memory info                                       
608	 misc        Miscellaneous                                     
609	 modules     List of loaded modules                            
610	 mounts      Mounted filesystems                               
611	 net         Networking info (see text)                        
612	 pagetypeinfo Additional page allocator information (see text)  (2.5)
613	 partitions  Table of partitions known to the system           
614	 pci	     Deprecated info of PCI bus (new way -> /proc/bus/pci/,
615	             decoupled by lspci					(2.4)
616	 rtc         Real time clock                                   
617	 scsi        SCSI info (see text)                              
618	 slabinfo    Slab pool info                                    
619	 softirqs    softirq usage
620	 stat        Overall statistics                                
621	 swaps       Swap space utilization                            
622	 sys         See chapter 2                                     
623	 sysvipc     Info of SysVIPC Resources (msg, sem, shm)		(2.4)
624	 tty	     Info of tty drivers
625	 uptime      Wall clock since boot, combined idle time of all cpus
626	 version     Kernel version                                    
627	 video	     bttv info of video resources			(2.4)
628	 vmallocinfo Show vmalloced areas
629	..............................................................................
630	
631	You can,  for  example,  check  which interrupts are currently in use and what
632	they are used for by looking in the file /proc/interrupts:
633	
634	  > cat /proc/interrupts 
635	             CPU0        
636	    0:    8728810          XT-PIC  timer 
637	    1:        895          XT-PIC  keyboard 
638	    2:          0          XT-PIC  cascade 
639	    3:     531695          XT-PIC  aha152x 
640	    4:    2014133          XT-PIC  serial 
641	    5:      44401          XT-PIC  pcnet_cs 
642	    8:          2          XT-PIC  rtc 
643	   11:          8          XT-PIC  i82365 
644	   12:     182918          XT-PIC  PS/2 Mouse 
645	   13:          1          XT-PIC  fpu 
646	   14:    1232265          XT-PIC  ide0 
647	   15:          7          XT-PIC  ide1 
648	  NMI:          0 
649	
650	In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
651	output of a SMP machine):
652	
653	  > cat /proc/interrupts 
654	
655	             CPU0       CPU1       
656	    0:    1243498    1214548    IO-APIC-edge  timer
657	    1:       8949       8958    IO-APIC-edge  keyboard
658	    2:          0          0          XT-PIC  cascade
659	    5:      11286      10161    IO-APIC-edge  soundblaster
660	    8:          1          0    IO-APIC-edge  rtc
661	    9:      27422      27407    IO-APIC-edge  3c503
662	   12:     113645     113873    IO-APIC-edge  PS/2 Mouse
663	   13:          0          0          XT-PIC  fpu
664	   14:      22491      24012    IO-APIC-edge  ide0
665	   15:       2183       2415    IO-APIC-edge  ide1
666	   17:      30564      30414   IO-APIC-level  eth0
667	   18:        177        164   IO-APIC-level  bttv
668	  NMI:    2457961    2457959 
669	  LOC:    2457882    2457881 
670	  ERR:       2155
671	
672	NMI is incremented in this case because every timer interrupt generates a NMI
673	(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
674	
675	LOC is the local interrupt counter of the internal APIC of every CPU.
676	
677	ERR is incremented in the case of errors in the IO-APIC bus (the bus that
678	connects the CPUs in a SMP system. This means that an error has been detected,
679	the IO-APIC automatically retry the transmission, so it should not be a big
680	problem, but you should read the SMP-FAQ.
681	
682	In 2.6.2* /proc/interrupts was expanded again.  This time the goal was for
683	/proc/interrupts to display every IRQ vector in use by the system, not
684	just those considered 'most important'.  The new vectors are:
685	
686	  THR -- interrupt raised when a machine check threshold counter
687	  (typically counting ECC corrected errors of memory or cache) exceeds
688	  a configurable threshold.  Only available on some systems.
689	
690	  TRM -- a thermal event interrupt occurs when a temperature threshold
691	  has been exceeded for the CPU.  This interrupt may also be generated
692	  when the temperature drops back to normal.
693	
694	  SPU -- a spurious interrupt is some interrupt that was raised then lowered
695	  by some IO device before it could be fully processed by the APIC.  Hence
696	  the APIC sees the interrupt but does not know what device it came from.
697	  For this case the APIC will generate the interrupt with a IRQ vector
698	  of 0xff. This might also be generated by chipset bugs.
699	
700	  RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
701	  sent from one CPU to another per the needs of the OS.  Typically,
702	  their statistics are used by kernel developers and interested users to
703	  determine the occurrence of interrupts of the given type.
704	
705	The above IRQ vectors are displayed only when relevant.  For example,
706	the threshold vector does not exist on x86_64 platforms.  Others are
707	suppressed when the system is a uniprocessor.  As of this writing, only
708	i386 and x86_64 platforms support the new IRQ vector displays.
709	
710	Of some interest is the introduction of the /proc/irq directory to 2.4.
711	It could be used to set IRQ to CPU affinity, this means that you can "hook" an
712	IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
713	irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
714	prof_cpu_mask.
715	
716	For example 
717	  > ls /proc/irq/
718	  0  10  12  14  16  18  2  4  6  8  prof_cpu_mask
719	  1  11  13  15  17  19  3  5  7  9  default_smp_affinity
720	  > ls /proc/irq/0/
721	  smp_affinity
722	
723	smp_affinity is a bitmask, in which you can specify which CPUs can handle the
724	IRQ, you can set it by doing:
725	
726	  > echo 1 > /proc/irq/10/smp_affinity
727	
728	This means that only the first CPU will handle the IRQ, but you can also echo
729	5 which means that only the first and third CPU can handle the IRQ.
730	
731	The contents of each smp_affinity file is the same by default:
732	
733	  > cat /proc/irq/0/smp_affinity
734	  ffffffff
735	
736	There is an alternate interface, smp_affinity_list which allows specifying
737	a cpu range instead of a bitmask:
738	
739	  > cat /proc/irq/0/smp_affinity_list
740	  1024-1031
741	
742	The default_smp_affinity mask applies to all non-active IRQs, which are the
743	IRQs which have not yet been allocated/activated, and hence which lack a
744	/proc/irq/[0-9]* directory.
745	
746	The node file on an SMP system shows the node to which the device using the IRQ
747	reports itself as being attached. This hardware locality information does not
748	include information about any possible driver locality preference.
749	
750	prof_cpu_mask specifies which CPUs are to be profiled by the system wide
751	profiler. Default value is ffffffff (all cpus if there are only 32 of them).
752	
753	The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
754	between all the CPUs which are allowed to handle it. As usual the kernel has
755	more info than you and does a better job than you, so the defaults are the
756	best choice for almost everyone.  [Note this applies only to those IO-APIC's
757	that support "Round Robin" interrupt distribution.]
758	
759	There are  three  more  important subdirectories in /proc: net, scsi, and sys.
760	The general  rule  is  that  the  contents,  or  even  the  existence of these
761	directories, depend  on your kernel configuration. If SCSI is not enabled, the
762	directory scsi  may  not  exist. The same is true with the net, which is there
763	only when networking support is present in the running kernel.
764	
765	The slabinfo  file  gives  information  about  memory usage at the slab level.
766	Linux uses  slab  pools for memory management above page level in version 2.2.
767	Commonly used  objects  have  their  own  slab  pool (such as network buffers,
768	directory cache, and so on).
769	
770	..............................................................................
771	
772	> cat /proc/buddyinfo
773	
774	Node 0, zone      DMA      0      4      5      4      4      3 ...
775	Node 0, zone   Normal      1      0      0      1    101      8 ...
776	Node 0, zone  HighMem      2      0      0      1      1      0 ...
777	
778	External fragmentation is a problem under some workloads, and buddyinfo is a
779	useful tool for helping diagnose these problems.  Buddyinfo will give you a 
780	clue as to how big an area you can safely allocate, or why a previous
781	allocation failed.
782	
783	Each column represents the number of pages of a certain order which are 
784	available.  In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 
785	ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 
786	available in ZONE_NORMAL, etc... 
787	
788	More information relevant to external fragmentation can be found in
789	pagetypeinfo.
790	
791	> cat /proc/pagetypeinfo
792	Page block order: 9
793	Pages per block:  512
794	
795	Free pages count per migrate type at order       0      1      2      3      4      5      6      7      8      9     10
796	Node    0, zone      DMA, type    Unmovable      0      0      0      1      1      1      1      1      1      1      0
797	Node    0, zone      DMA, type  Reclaimable      0      0      0      0      0      0      0      0      0      0      0
798	Node    0, zone      DMA, type      Movable      1      1      2      1      2      1      1      0      1      0      2
799	Node    0, zone      DMA, type      Reserve      0      0      0      0      0      0      0      0      0      1      0
800	Node    0, zone      DMA, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
801	Node    0, zone    DMA32, type    Unmovable    103     54     77      1      1      1     11      8      7      1      9
802	Node    0, zone    DMA32, type  Reclaimable      0      0      2      1      0      0      0      0      1      0      0
803	Node    0, zone    DMA32, type      Movable    169    152    113     91     77     54     39     13      6      1    452
804	Node    0, zone    DMA32, type      Reserve      1      2      2      2      2      0      1      1      1      1      0
805	Node    0, zone    DMA32, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
806	
807	Number of blocks type     Unmovable  Reclaimable      Movable      Reserve      Isolate
808	Node 0, zone      DMA            2            0            5            1            0
809	Node 0, zone    DMA32           41            6          967            2            0
810	
811	Fragmentation avoidance in the kernel works by grouping pages of different
812	migrate types into the same contiguous regions of memory called page blocks.
813	A page block is typically the size of the default hugepage size e.g. 2MB on
814	X86-64. By keeping pages grouped based on their ability to move, the kernel
815	can reclaim pages within a page block to satisfy a high-order allocation.
816	
817	The pagetypinfo begins with information on the size of a page block. It
818	then gives the same type of information as buddyinfo except broken down
819	by migrate-type and finishes with details on how many page blocks of each
820	type exist.
821	
822	If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
823	from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
824	make an estimate of the likely number of huge pages that can be allocated
825	at a given point in time. All the "Movable" blocks should be allocatable
826	unless memory has been mlock()'d. Some of the Reclaimable blocks should
827	also be allocatable although a lot of filesystem metadata may have to be
828	reclaimed to achieve this.
829	
830	..............................................................................
831	
832	meminfo:
833	
834	Provides information about distribution and utilization of memory.  This
835	varies by architecture and compile options.  The following is from a
836	16GB PIII, which has highmem enabled.  You may not have all of these fields.
837	
838	> cat /proc/meminfo
839	
840	MemTotal:     16344972 kB
841	MemFree:      13634064 kB
842	MemAvailable: 14836172 kB
843	Buffers:          3656 kB
844	Cached:        1195708 kB
845	SwapCached:          0 kB
846	Active:         891636 kB
847	Inactive:      1077224 kB
848	HighTotal:    15597528 kB
849	HighFree:     13629632 kB
850	LowTotal:       747444 kB
851	LowFree:          4432 kB
852	SwapTotal:           0 kB
853	SwapFree:            0 kB
854	Dirty:             968 kB
855	Writeback:           0 kB
856	AnonPages:      861800 kB
857	Mapped:         280372 kB
858	Shmem:             644 kB
859	Slab:           284364 kB
860	SReclaimable:   159856 kB
861	SUnreclaim:     124508 kB
862	PageTables:      24448 kB
863	NFS_Unstable:        0 kB
864	Bounce:              0 kB
865	WritebackTmp:        0 kB
866	CommitLimit:   7669796 kB
867	Committed_AS:   100056 kB
868	VmallocTotal:   112216 kB
869	VmallocUsed:       428 kB
870	VmallocChunk:   111088 kB
871	AnonHugePages:   49152 kB
872	ShmemHugePages:      0 kB
873	ShmemPmdMapped:      0 kB
874	
875	
876	    MemTotal: Total usable ram (i.e. physical ram minus a few reserved
877	              bits and the kernel binary code)
878	     MemFree: The sum of LowFree+HighFree
879	MemAvailable: An estimate of how much memory is available for starting new
880	              applications, without swapping. Calculated from MemFree,
881	              SReclaimable, the size of the file LRU lists, and the low
882	              watermarks in each zone.
883	              The estimate takes into account that the system needs some
884	              page cache to function well, and that not all reclaimable
885	              slab will be reclaimable, due to items being in use. The
886	              impact of those factors will vary from system to system.
887	     Buffers: Relatively temporary storage for raw disk blocks
888	              shouldn't get tremendously large (20MB or so)
889	      Cached: in-memory cache for files read from the disk (the
890	              pagecache).  Doesn't include SwapCached
891	  SwapCached: Memory that once was swapped out, is swapped back in but
892	              still also is in the swapfile (if memory is needed it
893	              doesn't need to be swapped out AGAIN because it is already
894	              in the swapfile. This saves I/O)
895	      Active: Memory that has been used more recently and usually not
896	              reclaimed unless absolutely necessary.
897	    Inactive: Memory which has been less recently used.  It is more
898	              eligible to be reclaimed for other purposes
899	   HighTotal:
900	    HighFree: Highmem is all memory above ~860MB of physical memory
901	              Highmem areas are for use by userspace programs, or
902	              for the pagecache.  The kernel must use tricks to access
903	              this memory, making it slower to access than lowmem.
904	    LowTotal:
905	     LowFree: Lowmem is memory which can be used for everything that
906	              highmem can be used for, but it is also available for the
907	              kernel's use for its own data structures.  Among many
908	              other things, it is where everything from the Slab is
909	              allocated.  Bad things happen when you're out of lowmem.
910	   SwapTotal: total amount of swap space available
911	    SwapFree: Memory which has been evicted from RAM, and is temporarily
912	              on the disk
913	       Dirty: Memory which is waiting to get written back to the disk
914	   Writeback: Memory which is actively being written back to the disk
915	   AnonPages: Non-file backed pages mapped into userspace page tables
916	AnonHugePages: Non-file backed huge pages mapped into userspace page tables
917	      Mapped: files which have been mmaped, such as libraries
918	       Shmem: Total memory used by shared memory (shmem) and tmpfs
919	ShmemHugePages: Memory used by shared memory (shmem) and tmpfs allocated
920	              with huge pages
921	ShmemPmdMapped: Shared memory mapped into userspace with huge pages
922	        Slab: in-kernel data structures cache
923	SReclaimable: Part of Slab, that might be reclaimed, such as caches
924	  SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
925	  PageTables: amount of memory dedicated to the lowest level of page
926	              tables.
927	NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
928		      storage
929	      Bounce: Memory used for block device "bounce buffers"
930	WritebackTmp: Memory used by FUSE for temporary writeback buffers
931	 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
932	              this is the total amount of  memory currently available to
933	              be allocated on the system. This limit is only adhered to
934	              if strict overcommit accounting is enabled (mode 2 in
935	              'vm.overcommit_memory').
936	              The CommitLimit is calculated with the following formula:
937	              CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
938	                             overcommit_ratio / 100 + [total swap pages]
939	              For example, on a system with 1G of physical RAM and 7G
940	              of swap with a `vm.overcommit_ratio` of 30 it would
941	              yield a CommitLimit of 7.3G.
942	              For more details, see the memory overcommit documentation
943	              in vm/overcommit-accounting.
944	Committed_AS: The amount of memory presently allocated on the system.
945	              The committed memory is a sum of all of the memory which
946	              has been allocated by processes, even if it has not been
947	              "used" by them as of yet. A process which malloc()'s 1G
948	              of memory, but only touches 300M of it will show up as
949		      using 1G. This 1G is memory which has been "committed" to
950	              by the VM and can be used at any time by the allocating
951	              application. With strict overcommit enabled on the system
952	              (mode 2 in 'vm.overcommit_memory'),allocations which would
953	              exceed the CommitLimit (detailed above) will not be permitted.
954	              This is useful if one needs to guarantee that processes will
955	              not fail due to lack of memory once that memory has been
956	              successfully allocated.
957	VmallocTotal: total size of vmalloc memory area
958	 VmallocUsed: amount of vmalloc area which is used
959	VmallocChunk: largest contiguous block of vmalloc area which is free
960	
961	..............................................................................
962	
963	vmallocinfo:
964	
965	Provides information about vmalloced/vmaped areas. One line per area,
966	containing the virtual address range of the area, size in bytes,
967	caller information of the creator, and optional information depending
968	on the kind of area :
969	
970	 pages=nr    number of pages
971	 phys=addr   if a physical address was specified
972	 ioremap     I/O mapping (ioremap() and friends)
973	 vmalloc     vmalloc() area
974	 vmap        vmap()ed pages
975	 user        VM_USERMAP area
976	 vpages      buffer for pages pointers was vmalloced (huge area)
977	 N<node>=nr  (Only on NUMA kernels)
978	             Number of pages allocated on memory node <node>
979	
980	> cat /proc/vmallocinfo
981	0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
982	  /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
983	0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
984	  /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
985	0xffffc20000302000-0xffffc20000304000    8192 acpi_tb_verify_table+0x21/0x4f...
986	  phys=7fee8000 ioremap
987	0xffffc20000304000-0xffffc20000307000   12288 acpi_tb_verify_table+0x21/0x4f...
988	  phys=7fee7000 ioremap
989	0xffffc2000031d000-0xffffc2000031f000    8192 init_vdso_vars+0x112/0x210
990	0xffffc2000031f000-0xffffc2000032b000   49152 cramfs_uncompress_init+0x2e ...
991	  /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
992	0xffffc2000033a000-0xffffc2000033d000   12288 sys_swapon+0x640/0xac0      ...
993	  pages=2 vmalloc N1=2
994	0xffffc20000347000-0xffffc2000034c000   20480 xt_alloc_table_info+0xfe ...
995	  /0x130 [x_tables] pages=4 vmalloc N0=4
996	0xffffffffa0000000-0xffffffffa000f000   61440 sys_init_module+0xc27/0x1d00 ...
997	   pages=14 vmalloc N2=14
998	0xffffffffa000f000-0xffffffffa0014000   20480 sys_init_module+0xc27/0x1d00 ...
999	   pages=4 vmalloc N1=4
1000	0xffffffffa0014000-0xffffffffa0017000   12288 sys_init_module+0xc27/0x1d00 ...
1001	   pages=2 vmalloc N1=2
1002	0xffffffffa0017000-0xffffffffa0022000   45056 sys_init_module+0xc27/0x1d00 ...
1003	   pages=10 vmalloc N0=10
1004	
1005	..............................................................................
1006	
1007	softirqs:
1008	
1009	Provides counts of softirq handlers serviced since boot time, for each cpu.
1010	
1011	> cat /proc/softirqs
1012	                CPU0       CPU1       CPU2       CPU3
1013	      HI:          0          0          0          0
1014	   TIMER:      27166      27120      27097      27034
1015	  NET_TX:          0          0          0         17
1016	  NET_RX:         42          0          0         39
1017	   BLOCK:          0          0        107       1121
1018	 TASKLET:          0          0          0        290
1019	   SCHED:      27035      26983      26971      26746
1020	 HRTIMER:          0          0          0          0
1021	     RCU:       1678       1769       2178       2250
1022	
1023	
1024	1.3 IDE devices in /proc/ide
1025	----------------------------
1026	
1027	The subdirectory /proc/ide contains information about all IDE devices of which
1028	the kernel  is  aware.  There is one subdirectory for each IDE controller, the
1029	file drivers  and a link for each IDE device, pointing to the device directory
1030	in the controller specific subtree.
1031	
1032	The file  drivers  contains general information about the drivers used for the
1033	IDE devices:
1034	
1035	  > cat /proc/ide/drivers
1036	  ide-cdrom version 4.53
1037	  ide-disk version 1.08
1038	
1039	More detailed  information  can  be  found  in  the  controller  specific
1040	subdirectories. These  are  named  ide0,  ide1  and  so  on.  Each  of  these
1041	directories contains the files shown in table 1-6.
1042	
1043	
1044	Table 1-6: IDE controller info in  /proc/ide/ide?
1045	..............................................................................
1046	 File    Content                                 
1047	 channel IDE channel (0 or 1)                    
1048	 config  Configuration (only for PCI/IDE bridge) 
1049	 mate    Mate name                               
1050	 model   Type/Chipset of IDE controller          
1051	..............................................................................
1052	
1053	Each device  connected  to  a  controller  has  a separate subdirectory in the
1054	controllers directory.  The  files  listed in table 1-7 are contained in these
1055	directories.
1056	
1057	
1058	Table 1-7: IDE device information
1059	..............................................................................
1060	 File             Content                                    
1061	 cache            The cache                                  
1062	 capacity         Capacity of the medium (in 512Byte blocks) 
1063	 driver           driver and version                         
1064	 geometry         physical and logical geometry              
1065	 identify         device identify block                      
1066	 media            media type                                 
1067	 model            device identifier                          
1068	 settings         device setup                               
1069	 smart_thresholds IDE disk management thresholds             
1070	 smart_values     IDE disk management values                 
1071	..............................................................................
1072	
1073	The most  interesting  file is settings. This file contains a nice overview of
1074	the drive parameters:
1075	
1076	  # cat /proc/ide/ide0/hda/settings 
1077	  name                    value           min             max             mode 
1078	  ----                    -----           ---             ---             ---- 
1079	  bios_cyl                526             0               65535           rw 
1080	  bios_head               255             0               255             rw 
1081	  bios_sect               63              0               63              rw 
1082	  breada_readahead        4               0               127             rw 
1083	  bswap                   0               0               1               r 
1084	  file_readahead          72              0               2097151         rw 
1085	  io_32bit                0               0               3               rw 
1086	  keepsettings            0               0               1               rw 
1087	  max_kb_per_request      122             1               127             rw 
1088	  multcount               0               0               8               rw 
1089	  nice1                   1               0               1               rw 
1090	  nowerr                  0               0               1               rw 
1091	  pio_mode                write-only      0               255             w 
1092	  slow                    0               0               1               rw 
1093	  unmaskirq               0               0               1               rw 
1094	  using_dma               0               0               1               rw 
1095	
1096	
1097	1.4 Networking info in /proc/net
1098	--------------------------------
1099	
1100	The subdirectory  /proc/net  follows  the  usual  pattern. Table 1-8 shows the
1101	additional values  you  get  for  IP  version 6 if you configure the kernel to
1102	support this. Table 1-9 lists the files and their meaning.
1103	
1104	
1105	Table 1-8: IPv6 info in /proc/net
1106	..............................................................................
1107	 File       Content                                               
1108	 udp6       UDP sockets (IPv6)                                    
1109	 tcp6       TCP sockets (IPv6)                                    
1110	 raw6       Raw device statistics (IPv6)                          
1111	 igmp6      IP multicast addresses, which this host joined (IPv6) 
1112	 if_inet6   List of IPv6 interface addresses                      
1113	 ipv6_route Kernel routing table for IPv6                         
1114	 rt6_stats  Global IPv6 routing tables statistics                 
1115	 sockstat6  Socket statistics (IPv6)                              
1116	 snmp6      Snmp data (IPv6)                                      
1117	..............................................................................
1118	
1119	
1120	Table 1-9: Network info in /proc/net
1121	..............................................................................
1122	 File          Content                                                         
1123	 arp           Kernel  ARP table                                               
1124	 dev           network devices with statistics                                 
1125	 dev_mcast     the Layer2 multicast groups a device is listening too
1126	               (interface index, label, number of references, number of bound
1127	               addresses). 
1128	 dev_stat      network device status                                           
1129	 ip_fwchains   Firewall chain linkage                                          
1130	 ip_fwnames    Firewall chain names                                            
1131	 ip_masq       Directory containing the masquerading tables                    
1132	 ip_masquerade Major masquerading table                                        
1133	 netstat       Network statistics                                              
1134	 raw           raw device statistics                                           
1135	 route         Kernel routing table                                            
1136	 rpc           Directory containing rpc info                                   
1137	 rt_cache      Routing cache                                                   
1138	 snmp          SNMP data                                                       
1139	 sockstat      Socket statistics                                               
1140	 tcp           TCP  sockets                                                    
1141	 udp           UDP sockets                                                     
1142	 unix          UNIX domain sockets                                             
1143	 wireless      Wireless interface data (Wavelan etc)                           
1144	 igmp          IP multicast addresses, which this host joined                  
1145	 psched        Global packet scheduler parameters.                             
1146	 netlink       List of PF_NETLINK sockets                                      
1147	 ip_mr_vifs    List of multicast virtual interfaces                            
1148	 ip_mr_cache   List of multicast routing cache                                 
1149	..............................................................................
1150	
1151	You can  use  this  information  to see which network devices are available in
1152	your system and how much traffic was routed over those devices:
1153	
1154	  > cat /proc/net/dev 
1155	  Inter-|Receive                                                   |[... 
1156	   face |bytes    packets errs drop fifo frame compressed multicast|[... 
1157	      lo:  908188   5596     0    0    0     0          0         0 [...         
1158	    ppp0:15475140  20721   410    0    0   410          0         0 [...  
1159	    eth0:  614530   7085     0    0    0     0          0         1 [... 
1160	   
1161	  ...] Transmit 
1162	  ...] bytes    packets errs drop fifo colls carrier compressed 
1163	  ...]  908188     5596    0    0    0     0       0          0 
1164	  ...] 1375103    17405    0    0    0     0       0          0 
1165	  ...] 1703981     5535    0    0    0     3       0          0 
1166	
1167	In addition, each Channel Bond interface has its own directory.  For
1168	example, the bond0 device will have a directory called /proc/net/bond0/.
1169	It will contain information that is specific to that bond, such as the
1170	current slaves of the bond, the link status of the slaves, and how
1171	many times the slaves link has failed.
1172	
1173	1.5 SCSI info
1174	-------------
1175	
1176	If you  have  a  SCSI  host adapter in your system, you'll find a subdirectory
1177	named after  the driver for this adapter in /proc/scsi. You'll also see a list
1178	of all recognized SCSI devices in /proc/scsi:
1179	
1180	  >cat /proc/scsi/scsi 
1181	  Attached devices: 
1182	  Host: scsi0 Channel: 00 Id: 00 Lun: 00 
1183	    Vendor: IBM      Model: DGHS09U          Rev: 03E0 
1184	    Type:   Direct-Access                    ANSI SCSI revision: 03 
1185	  Host: scsi0 Channel: 00 Id: 06 Lun: 00 
1186	    Vendor: PIONEER  Model: CD-ROM DR-U06S   Rev: 1.04 
1187	    Type:   CD-ROM                           ANSI SCSI revision: 02 
1188	
1189	
1190	The directory  named  after  the driver has one file for each adapter found in
1191	the system.  These  files  contain information about the controller, including
1192	the used  IRQ  and  the  IO  address range. The amount of information shown is
1193	dependent on  the adapter you use. The example shows the output for an Adaptec
1194	AHA-2940 SCSI adapter:
1195	
1196	  > cat /proc/scsi/aic7xxx/0 
1197	   
1198	  Adaptec AIC7xxx driver version: 5.1.19/3.2.4 
1199	  Compile Options: 
1200	    TCQ Enabled By Default : Disabled 
1201	    AIC7XXX_PROC_STATS     : Disabled 
1202	    AIC7XXX_RESET_DELAY    : 5 
1203	  Adapter Configuration: 
1204	             SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 
1205	                             Ultra Wide Controller 
1206	      PCI MMAPed I/O Base: 0xeb001000 
1207	   Adapter SEEPROM Config: SEEPROM found and used. 
1208	        Adaptec SCSI BIOS: Enabled 
1209	                      IRQ: 10 
1210	                     SCBs: Active 0, Max Active 2, 
1211	                           Allocated 15, HW 16, Page 255 
1212	               Interrupts: 160328 
1213	        BIOS Control Word: 0x18b6 
1214	     Adapter Control Word: 0x005b 
1215	     Extended Translation: Enabled 
1216	  Disconnect Enable Flags: 0xffff 
1217	       Ultra Enable Flags: 0x0001 
1218	   Tag Queue Enable Flags: 0x0000 
1219	  Ordered Queue Tag Flags: 0x0000 
1220	  Default Tag Queue Depth: 8 
1221	      Tagged Queue By Device array for aic7xxx host instance 0: 
1222	        {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 
1223	      Actual queue depth per device for aic7xxx host instance 0: 
1224	        {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 
1225	  Statistics: 
1226	  (scsi0:0:0:0) 
1227	    Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 
1228	    Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 
1229	    Total transfers 160151 (74577 reads and 85574 writes) 
1230	  (scsi0:0:6:0) 
1231	    Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 
1232	    Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 
1233	    Total transfers 0 (0 reads and 0 writes) 
1234	
1235	
1236	1.6 Parallel port info in /proc/parport
1237	---------------------------------------
1238	
1239	The directory  /proc/parport  contains information about the parallel ports of
1240	your system.  It  has  one  subdirectory  for  each port, named after the port
1241	number (0,1,2,...).
1242	
1243	These directories contain the four files shown in Table 1-10.
1244	
1245	
1246	Table 1-10: Files in /proc/parport
1247	..............................................................................
1248	 File      Content                                                             
1249	 autoprobe Any IEEE-1284 device ID information that has been acquired.         
1250	 devices   list of the device drivers using that port. A + will appear by the
1251	           name of the device currently using the port (it might not appear
1252	           against any). 
1253	 hardware  Parallel port's base address, IRQ line and DMA channel.             
1254	 irq       IRQ that parport is using for that port. This is in a separate
1255	           file to allow you to alter it by writing a new value in (IRQ
1256	           number or none). 
1257	..............................................................................
1258	
1259	1.7 TTY info in /proc/tty
1260	-------------------------
1261	
1262	Information about  the  available  and actually used tty's can be found in the
1263	directory /proc/tty.You'll  find  entries  for drivers and line disciplines in
1264	this directory, as shown in Table 1-11.
1265	
1266	
1267	Table 1-11: Files in /proc/tty
1268	..............................................................................
1269	 File          Content                                        
1270	 drivers       list of drivers and their usage                
1271	 ldiscs        registered line disciplines                    
1272	 driver/serial usage statistic and status of single tty lines 
1273	..............................................................................
1274	
1275	To see  which  tty's  are  currently in use, you can simply look into the file
1276	/proc/tty/drivers:
1277	
1278	  > cat /proc/tty/drivers 
1279	  pty_slave            /dev/pts      136   0-255 pty:slave 
1280	  pty_master           /dev/ptm      128   0-255 pty:master 
1281	  pty_slave            /dev/ttyp       3   0-255 pty:slave 
1282	  pty_master           /dev/pty        2   0-255 pty:master 
1283	  serial               /dev/cua        5   64-67 serial:callout 
1284	  serial               /dev/ttyS       4   64-67 serial 
1285	  /dev/tty0            /dev/tty0       4       0 system:vtmaster 
1286	  /dev/ptmx            /dev/ptmx       5       2 system 
1287	  /dev/console         /dev/console    5       1 system:console 
1288	  /dev/tty             /dev/tty        5       0 system:/dev/tty 
1289	  unknown              /dev/tty        4    1-63 console 
1290	
1291	
1292	1.8 Miscellaneous kernel statistics in /proc/stat
1293	-------------------------------------------------
1294	
1295	Various pieces   of  information about  kernel activity  are  available in the
1296	/proc/stat file.  All  of  the numbers reported  in  this file are  aggregates
1297	since the system first booted.  For a quick look, simply cat the file:
1298	
1299	  > cat /proc/stat
1300	  cpu  2255 34 2290 22625563 6290 127 456 0 0 0
1301	  cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1302	  cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1303	  intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1304	  ctxt 1990473
1305	  btime 1062191376
1306	  processes 2915
1307	  procs_running 1
1308	  procs_blocked 0
1309	  softirq 183433 0 21755 12 39 1137 231 21459 2263
1310	
1311	The very first  "cpu" line aggregates the  numbers in all  of the other "cpuN"
1312	lines.  These numbers identify the amount of time the CPU has spent performing
1313	different kinds of work.  Time units are in USER_HZ (typically hundredths of a
1314	second).  The meanings of the columns are as follows, from left to right:
1315	
1316	- user: normal processes executing in user mode
1317	- nice: niced processes executing in user mode
1318	- system: processes executing in kernel mode
1319	- idle: twiddling thumbs
1320	- iowait: In a word, iowait stands for waiting for I/O to complete. But there
1321	  are several problems:
1322	  1. Cpu will not wait for I/O to complete, iowait is the time that a task is
1323	     waiting for I/O to complete. When cpu goes into idle state for
1324	     outstanding task io, another task will be scheduled on this CPU.
1325	  2. In a multi-core CPU, the task waiting for I/O to complete is not running
1326	     on any CPU, so the iowait of each CPU is difficult to calculate.
1327	  3. The value of iowait field in /proc/stat will decrease in certain
1328	     conditions.
1329	  So, the iowait is not reliable by reading from /proc/stat.
1330	- irq: servicing interrupts
1331	- softirq: servicing softirqs
1332	- steal: involuntary wait
1333	- guest: running a normal guest
1334	- guest_nice: running a niced guest
1335	
1336	The "intr" line gives counts of interrupts  serviced since boot time, for each
1337	of the  possible system interrupts.   The first  column  is the  total of  all
1338	interrupts serviced  including  unnumbered  architecture specific  interrupts;
1339	each  subsequent column is the  total for that particular numbered interrupt.
1340	Unnumbered interrupts are not shown, only summed into the total.
1341	
1342	The "ctxt" line gives the total number of context switches across all CPUs.
1343	
1344	The "btime" line gives  the time at which the  system booted, in seconds since
1345	the Unix epoch.
1346	
1347	The "processes" line gives the number  of processes and threads created, which
1348	includes (but  is not limited  to) those  created by  calls to the  fork() and
1349	clone() system calls.
1350	
1351	The "procs_running" line gives the total number of threads that are
1352	running or ready to run (i.e., the total number of runnable threads).
1353	
1354	The   "procs_blocked" line gives  the  number of  processes currently blocked,
1355	waiting for I/O to complete.
1356	
1357	The "softirq" line gives counts of softirqs serviced since boot time, for each
1358	of the possible system softirqs. The first column is the total of all
1359	softirqs serviced; each subsequent column is the total for that particular
1360	softirq.
1361	
1362	
1363	1.9 Ext4 file system parameters
1364	-------------------------------
1365	
1366	Information about mounted ext4 file systems can be found in
1367	/proc/fs/ext4.  Each mounted filesystem will have a directory in
1368	/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1369	/proc/fs/ext4/dm-0).   The files in each per-device directory are shown
1370	in Table 1-12, below.
1371	
1372	Table 1-12: Files in /proc/fs/ext4/<devname>
1373	..............................................................................
1374	 File            Content                                        
1375	 mb_groups       details of multiblock allocator buddy cache of free blocks
1376	..............................................................................
1377	
1378	2.0 /proc/consoles
1379	------------------
1380	Shows registered system console lines.
1381	
1382	To see which character device lines are currently used for the system console
1383	/dev/console, you may simply look into the file /proc/consoles:
1384	
1385	  > cat /proc/consoles
1386	  tty0                 -WU (ECp)       4:7
1387	  ttyS0                -W- (Ep)        4:64
1388	
1389	The columns are:
1390	
1391	  device               name of the device
1392	  operations           R = can do read operations
1393	                       W = can do write operations
1394	                       U = can do unblank
1395	  flags                E = it is enabled
1396	                       C = it is preferred console
1397	                       B = it is primary boot console
1398	                       p = it is used for printk buffer
1399	                       b = it is not a TTY but a Braille device
1400	                       a = it is safe to use when cpu is offline
1401	  major:minor          major and minor number of the device separated by a colon
1402	
1403	------------------------------------------------------------------------------
1404	Summary
1405	------------------------------------------------------------------------------
1406	The /proc file system serves information about the running system. It not only
1407	allows access to process data but also allows you to request the kernel status
1408	by reading files in the hierarchy.
1409	
1410	The directory  structure  of /proc reflects the types of information and makes
1411	it easy, if not obvious, where to look for specific data.
1412	------------------------------------------------------------------------------
1413	
1414	------------------------------------------------------------------------------
1415	CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1416	------------------------------------------------------------------------------
1417	
1418	------------------------------------------------------------------------------
1419	In This Chapter
1420	------------------------------------------------------------------------------
1421	* Modifying kernel parameters by writing into files found in /proc/sys
1422	* Exploring the files which modify certain parameters
1423	* Review of the /proc/sys file tree
1424	------------------------------------------------------------------------------
1425	
1426	
1427	A very  interesting part of /proc is the directory /proc/sys. This is not only
1428	a source  of  information,  it also allows you to change parameters within the
1429	kernel. Be  very  careful  when attempting this. You can optimize your system,
1430	but you  can  also  cause  it  to  crash.  Never  alter kernel parameters on a
1431	production system.  Set  up  a  development machine and test to make sure that
1432	everything works  the  way  you want it to. You may have no alternative but to
1433	reboot the machine once an error has been made.
1434	
1435	To change  a  value,  simply  echo  the new value into the file. An example is
1436	given below  in the section on the file system data. You need to be root to do
1437	this. You  can  create  your  own  boot script to perform this every time your
1438	system boots.
1439	
1440	The files  in /proc/sys can be used to fine tune and monitor miscellaneous and
1441	general things  in  the operation of the Linux kernel. Since some of the files
1442	can inadvertently  disrupt  your  system,  it  is  advisable  to  read  both
1443	documentation and  source  before actually making adjustments. In any case, be
1444	very careful  when  writing  to  any  of these files. The entries in /proc may
1445	change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1446	review the kernel documentation in the directory /usr/src/linux/Documentation.
1447	This chapter  is  heavily  based  on the documentation included in the pre 2.2
1448	kernels, and became part of it in version 2.2.1 of the Linux kernel.
1449	
1450	Please see: Documentation/sysctl/ directory for descriptions of these
1451	entries.
1452	
1453	------------------------------------------------------------------------------
1454	Summary
1455	------------------------------------------------------------------------------
1456	Certain aspects  of  kernel  behavior  can be modified at runtime, without the
1457	need to  recompile  the kernel, or even to reboot the system. The files in the
1458	/proc/sys tree  can  not only be read, but also modified. You can use the echo
1459	command to write value into these files, thereby changing the default settings
1460	of the kernel.
1461	------------------------------------------------------------------------------
1462	
1463	------------------------------------------------------------------------------
1464	CHAPTER 3: PER-PROCESS PARAMETERS
1465	------------------------------------------------------------------------------
1466	
1467	3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1468	--------------------------------------------------------------------------------
1469	
1470	These file can be used to adjust the badness heuristic used to select which
1471	process gets killed in out of memory conditions.
1472	
1473	The badness heuristic assigns a value to each candidate task ranging from 0
1474	(never kill) to 1000 (always kill) to determine which process is targeted.  The
1475	units are roughly a proportion along that range of allowed memory the process
1476	may allocate from based on an estimation of its current memory and swap use.
1477	For example, if a task is using all allowed memory, its badness score will be
1478	1000.  If it is using half of its allowed memory, its score will be 500.
1479	
1480	There is an additional factor included in the badness score: the current memory
1481	and swap usage is discounted by 3% for root processes.
1482	
1483	The amount of "allowed" memory depends on the context in which the oom killer
1484	was called.  If it is due to the memory assigned to the allocating task's cpuset
1485	being exhausted, the allowed memory represents the set of mems assigned to that
1486	cpuset.  If it is due to a mempolicy's node(s) being exhausted, the allowed
1487	memory represents the set of mempolicy nodes.  If it is due to a memory
1488	limit (or swap limit) being reached, the allowed memory is that configured
1489	limit.  Finally, if it is due to the entire system being out of memory, the
1490	allowed memory represents all allocatable resources.
1491	
1492	The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1493	is used to determine which task to kill.  Acceptable values range from -1000
1494	(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX).  This allows userspace to
1495	polarize the preference for oom killing either by always preferring a certain
1496	task or completely disabling it.  The lowest possible value, -1000, is
1497	equivalent to disabling oom killing entirely for that task since it will always
1498	report a badness score of 0.
1499	
1500	Consequently, it is very simple for userspace to define the amount of memory to
1501	consider for each task.  Setting a /proc/<pid>/oom_score_adj value of +500, for
1502	example, is roughly equivalent to allowing the remainder of tasks sharing the
1503	same system, cpuset, mempolicy, or memory controller resources to use at least
1504	50% more memory.  A value of -500, on the other hand, would be roughly
1505	equivalent to discounting 50% of the task's allowed memory from being considered
1506	as scoring against the task.
1507	
1508	For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1509	be used to tune the badness score.  Its acceptable values range from -16
1510	(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1511	(OOM_DISABLE) to disable oom killing entirely for that task.  Its value is
1512	scaled linearly with /proc/<pid>/oom_score_adj.
1513	
1514	The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1515	value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1516	requires CAP_SYS_RESOURCE.
1517	
1518	Caveat: when a parent task is selected, the oom killer will sacrifice any first
1519	generation children with separate address spaces instead, if possible.  This
1520	avoids servers and important system daemons from being killed and loses the
1521	minimal amount of work.
1522	
1523	
1524	3.2 /proc/<pid>/oom_score - Display current oom-killer score
1525	-------------------------------------------------------------
1526	
1527	This file can be used to check the current score used by the oom-killer is for
1528	any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1529	process should be killed in an out-of-memory situation.
1530	
1531	
1532	3.3  /proc/<pid>/io - Display the IO accounting fields
1533	-------------------------------------------------------
1534	
1535	This file contains IO statistics for each running process
1536	
1537	Example
1538	-------
1539	
1540	test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1541	[1] 3828
1542	
1543	test:/tmp # cat /proc/3828/io
1544	rchar: 323934931
1545	wchar: 323929600
1546	syscr: 632687
1547	syscw: 632675
1548	read_bytes: 0
1549	write_bytes: 323932160
1550	cancelled_write_bytes: 0
1551	
1552	
1553	Description
1554	-----------
1555	
1556	rchar
1557	-----
1558	
1559	I/O counter: chars read
1560	The number of bytes which this task has caused to be read from storage. This
1561	is simply the sum of bytes which this process passed to read() and pread().
1562	It includes things like tty IO and it is unaffected by whether or not actual
1563	physical disk IO was required (the read might have been satisfied from
1564	pagecache)
1565	
1566	
1567	wchar
1568	-----
1569	
1570	I/O counter: chars written
1571	The number of bytes which this task has caused, or shall cause to be written
1572	to disk. Similar caveats apply here as with rchar.
1573	
1574	
1575	syscr
1576	-----
1577	
1578	I/O counter: read syscalls
1579	Attempt to count the number of read I/O operations, i.e. syscalls like read()
1580	and pread().
1581	
1582	
1583	syscw
1584	-----
1585	
1586	I/O counter: write syscalls
1587	Attempt to count the number of write I/O operations, i.e. syscalls like
1588	write() and pwrite().
1589	
1590	
1591	read_bytes
1592	----------
1593	
1594	I/O counter: bytes read
1595	Attempt to count the number of bytes which this process really did cause to
1596	be fetched from the storage layer. Done at the submit_bio() level, so it is
1597	accurate for block-backed filesystems. <please add status regarding NFS and
1598	CIFS at a later time>
1599	
1600	
1601	write_bytes
1602	-----------
1603	
1604	I/O counter: bytes written
1605	Attempt to count the number of bytes which this process caused to be sent to
1606	the storage layer. This is done at page-dirtying time.
1607	
1608	
1609	cancelled_write_bytes
1610	---------------------
1611	
1612	The big inaccuracy here is truncate. If a process writes 1MB to a file and
1613	then deletes the file, it will in fact perform no writeout. But it will have
1614	been accounted as having caused 1MB of write.
1615	In other words: The number of bytes which this process caused to not happen,
1616	by truncating pagecache. A task can cause "negative" IO too. If this task
1617	truncates some dirty pagecache, some IO which another task has been accounted
1618	for (in its write_bytes) will not be happening. We _could_ just subtract that
1619	from the truncating task's write_bytes, but there is information loss in doing
1620	that.
1621	
1622	
1623	Note
1624	----
1625	
1626	At its current implementation state, this is a bit racy on 32-bit machines: if
1627	process A reads process B's /proc/pid/io while process B is updating one of
1628	those 64-bit counters, process A could see an intermediate result.
1629	
1630	
1631	More information about this can be found within the taskstats documentation in
1632	Documentation/accounting.
1633	
1634	3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1635	---------------------------------------------------------------
1636	When a process is dumped, all anonymous memory is written to a core file as
1637	long as the size of the core file isn't limited. But sometimes we don't want
1638	to dump some memory segments, for example, huge shared memory or DAX.
1639	Conversely, sometimes we want to save file-backed memory segments into a core
1640	file, not only the individual files.
1641	
1642	/proc/<pid>/coredump_filter allows you to customize which memory segments
1643	will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1644	of memory types. If a bit of the bitmask is set, memory segments of the
1645	corresponding memory type are dumped, otherwise they are not dumped.
1646	
1647	The following 9 memory types are supported:
1648	  - (bit 0) anonymous private memory
1649	  - (bit 1) anonymous shared memory
1650	  - (bit 2) file-backed private memory
1651	  - (bit 3) file-backed shared memory
1652	  - (bit 4) ELF header pages in file-backed private memory areas (it is
1653	            effective only if the bit 2 is cleared)
1654	  - (bit 5) hugetlb private memory
1655	  - (bit 6) hugetlb shared memory
1656	  - (bit 7) DAX private memory
1657	  - (bit 8) DAX shared memory
1658	
1659	  Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1660	  are always dumped regardless of the bitmask status.
1661	
1662	  Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
1663	  only affected by bit 5-6, and DAX is only affected by bits 7-8.
1664	
1665	The default value of coredump_filter is 0x33; this means all anonymous memory
1666	segments, ELF header pages and hugetlb private memory are dumped.
1667	
1668	If you don't want to dump all shared memory segments attached to pid 1234,
1669	write 0x31 to the process's proc file.
1670	
1671	  $ echo 0x31 > /proc/1234/coredump_filter
1672	
1673	When a new process is created, the process inherits the bitmask status from its
1674	parent. It is useful to set up coredump_filter before the program runs.
1675	For example:
1676	
1677	  $ echo 0x7 > /proc/self/coredump_filter
1678	  $ ./some_program
1679	
1680	3.5	/proc/<pid>/mountinfo - Information about mounts
1681	--------------------------------------------------------
1682	
1683	This file contains lines of the form:
1684	
1685	36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1686	(1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
1687	
1688	(1) mount ID:  unique identifier of the mount (may be reused after umount)
1689	(2) parent ID:  ID of parent (or of self for the top of the mount tree)
1690	(3) major:minor:  value of st_dev for files on filesystem
1691	(4) root:  root of the mount within the filesystem
1692	(5) mount point:  mount point relative to the process's root
1693	(6) mount options:  per mount options
1694	(7) optional fields:  zero or more fields of the form "tag[:value]"
1695	(8) separator:  marks the end of the optional fields
1696	(9) filesystem type:  name of filesystem of the form "type[.subtype]"
1697	(10) mount source:  filesystem specific information or "none"
1698	(11) super options:  per super block options
1699	
1700	Parsers should ignore all unrecognised optional fields.  Currently the
1701	possible optional fields are:
1702	
1703	shared:X  mount is shared in peer group X
1704	master:X  mount is slave to peer group X
1705	propagate_from:X  mount is slave and receives propagation from peer group X (*)
1706	unbindable  mount is unbindable
1707	
1708	(*) X is the closest dominant peer group under the process's root.  If
1709	X is the immediate master of the mount, or if there's no dominant peer
1710	group under the same root, then only the "master:X" field is present
1711	and not the "propagate_from:X" field.
1712	
1713	For more information on mount propagation see:
1714	
1715	  Documentation/filesystems/sharedsubtree.txt
1716	
1717	
1718	3.6	/proc/<pid>/comm  & /proc/<pid>/task/<tid>/comm
1719	--------------------------------------------------------
1720	These files provide a method to access a tasks comm value. It also allows for
1721	a task to set its own or one of its thread siblings comm value. The comm value
1722	is limited in size compared to the cmdline value, so writing anything longer
1723	then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1724	comm value.
1725	
1726	
1727	3.7	/proc/<pid>/task/<tid>/children - Information about task children
1728	-------------------------------------------------------------------------
1729	This file provides a fast way to retrieve first level children pids
1730	of a task pointed by <pid>/<tid> pair. The format is a space separated
1731	stream of pids.
1732	
1733	Note the "first level" here -- if a child has own children they will
1734	not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1735	to obtain the descendants.
1736	
1737	Since this interface is intended to be fast and cheap it doesn't
1738	guarantee to provide precise results and some children might be
1739	skipped, especially if they've exited right after we printed their
1740	pids, so one need to either stop or freeze processes being inspected
1741	if precise results are needed.
1742	
1743	
1744	3.8	/proc/<pid>/fdinfo/<fd> - Information about opened file
1745	---------------------------------------------------------------
1746	This file provides information associated with an opened file. The regular
1747	files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1748	represents the current offset of the opened file in decimal form [see lseek(2)
1749	for details], 'flags' denotes the octal O_xxx mask the file has been
1750	created with [see open(2) for details] and 'mnt_id' represents mount ID of
1751	the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1752	for details].
1753	
1754	A typical output is
1755	
1756		pos:	0
1757		flags:	0100002
1758		mnt_id:	19
1759	
1760	All locks associated with a file descriptor are shown in its fdinfo too.
1761	
1762	lock:       1: FLOCK  ADVISORY  WRITE 359 00:13:11691 0 EOF
1763	
1764	The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1765	pair provide additional information particular to the objects they represent.
1766	
1767		Eventfd files
1768		~~~~~~~~~~~~~
1769		pos:	0
1770		flags:	04002
1771		mnt_id:	9
1772		eventfd-count:	5a
1773	
1774		where 'eventfd-count' is hex value of a counter.
1775	
1776		Signalfd files
1777		~~~~~~~~~~~~~~
1778		pos:	0
1779		flags:	04002
1780		mnt_id:	9
1781		sigmask:	0000000000000200
1782	
1783		where 'sigmask' is hex value of the signal mask associated
1784		with a file.
1785	
1786		Epoll files
1787		~~~~~~~~~~~
1788		pos:	0
1789		flags:	02
1790		mnt_id:	9
1791		tfd:        5 events:       1d data: ffffffffffffffff pos:0 ino:61af sdev:7
1792	
1793		where 'tfd' is a target file descriptor number in decimal form,
1794		'events' is events mask being watched and the 'data' is data
1795		associated with a target [see epoll(7) for more details].
1796	
1797		The 'pos' is current offset of the target file in decimal form
1798		[see lseek(2)], 'ino' and 'sdev' are inode and device numbers
1799		where target file resides, all in hex format.
1800	
1801		Fsnotify files
1802		~~~~~~~~~~~~~~
1803		For inotify files the format is the following
1804	
1805		pos:	0
1806		flags:	02000000
1807		inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1808	
1809		where 'wd' is a watch descriptor in decimal form, ie a target file
1810		descriptor number, 'ino' and 'sdev' are inode and device where the
1811		target file resides and the 'mask' is the mask of events, all in hex
1812		form [see inotify(7) for more details].
1813	
1814		If the kernel was built with exportfs support, the path to the target
1815		file is encoded as a file handle.  The file handle is provided by three
1816		fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1817		format.
1818	
1819		If the kernel is built without exportfs support the file handle won't be
1820		printed out.
1821	
1822		If there is no inotify mark attached yet the 'inotify' line will be omitted.
1823	
1824		For fanotify files the format is
1825	
1826		pos:	0
1827		flags:	02
1828		mnt_id:	9
1829		fanotify flags:10 event-flags:0
1830		fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1831		fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1832	
1833		where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1834		call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1835		flags associated with mark which are tracked separately from events
1836		mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1837		mask and 'ignored_mask' is the mask of events which are to be ignored.
1838		All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1839		does provide information about flags and mask used in fanotify_mark
1840		call [see fsnotify manpage for details].
1841	
1842		While the first three lines are mandatory and always printed, the rest is
1843		optional and may be omitted if no marks created yet.
1844	
1845		Timerfd files
1846		~~~~~~~~~~~~~
1847	
1848		pos:	0
1849		flags:	02
1850		mnt_id:	9
1851		clockid: 0
1852		ticks: 0
1853		settime flags: 01
1854		it_value: (0, 49406829)
1855		it_interval: (1, 0)
1856	
1857		where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
1858		that have occurred [see timerfd_create(2) for details]. 'settime flags' are
1859		flags in octal form been used to setup the timer [see timerfd_settime(2) for
1860		details]. 'it_value' is remaining time until the timer exiration.
1861		'it_interval' is the interval for the timer. Note the timer might be set up
1862		with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
1863		still exhibits timer's remaining time.
1864	
1865	3.9	/proc/<pid>/map_files - Information about memory mapped files
1866	---------------------------------------------------------------------
1867	This directory contains symbolic links which represent memory mapped files
1868	the process is maintaining.  Example output:
1869	
1870	     | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
1871	     | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
1872	     | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
1873	     | ...
1874	     | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
1875	     | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
1876	
1877	The name of a link represents the virtual memory bounds of a mapping, i.e.
1878	vm_area_struct::vm_start-vm_area_struct::vm_end.
1879	
1880	The main purpose of the map_files is to retrieve a set of memory mapped
1881	files in a fast way instead of parsing /proc/<pid>/maps or
1882	/proc/<pid>/smaps, both of which contain many more records.  At the same
1883	time one can open(2) mappings from the listings of two processes and
1884	comparing their inode numbers to figure out which anonymous memory areas
1885	are actually shared.
1886	
1887	3.10	/proc/<pid>/timerslack_ns - Task timerslack value
1888	---------------------------------------------------------
1889	This file provides the value of the task's timerslack value in nanoseconds.
1890	This value specifies a amount of time that normal timers may be deferred
1891	in order to coalesce timers and avoid unnecessary wakeups.
1892	
1893	This allows a task's interactivity vs power consumption trade off to be
1894	adjusted.
1895	
1896	Writing 0 to the file will set the tasks timerslack to the default value.
1897	
1898	Valid values are from 0 - ULLONG_MAX
1899	
1900	An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
1901	permissions on the task specified to change its timerslack_ns value.
1902	
1903	3.11	/proc/<pid>/patch_state - Livepatch patch operation state
1904	-----------------------------------------------------------------
1905	When CONFIG_LIVEPATCH is enabled, this file displays the value of the
1906	patch state for the task.
1907	
1908	A value of '-1' indicates that no patch is in transition.
1909	
1910	A value of '0' indicates that a patch is in transition and the task is
1911	unpatched.  If the patch is being enabled, then the task hasn't been
1912	patched yet.  If the patch is being disabled, then the task has already
1913	been unpatched.
1914	
1915	A value of '1' indicates that a patch is in transition and the task is
1916	patched.  If the patch is being enabled, then the task has already been
1917	patched.  If the patch is being disabled, then the task hasn't been
1918	unpatched yet.
1919	
1920	
1921	------------------------------------------------------------------------------
1922	Configuring procfs
1923	------------------------------------------------------------------------------
1924	
1925	4.1	Mount options
1926	---------------------
1927	
1928	The following mount options are supported:
1929	
1930		hidepid=	Set /proc/<pid>/ access mode.
1931		gid=		Set the group authorized to learn processes information.
1932	
1933	hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1934	(default).
1935	
1936	hidepid=1 means users may not access any /proc/<pid>/ directories but their
1937	own.  Sensitive files like cmdline, sched*, status are now protected against
1938	other users.  This makes it impossible to learn whether any user runs
1939	specific program (given the program doesn't reveal itself by its behaviour).
1940	As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1941	poorly written programs passing sensitive information via program arguments are
1942	now protected against local eavesdroppers.
1943	
1944	hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1945	users.  It doesn't mean that it hides a fact whether a process with a specific
1946	pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1947	but it hides process' uid and gid, which may be learned by stat()'ing
1948	/proc/<pid>/ otherwise.  It greatly complicates an intruder's task of gathering
1949	information about running processes, whether some daemon runs with elevated
1950	privileges, whether other user runs some sensitive program, whether other users
1951	run any program at all, etc.
1952	
1953	gid= defines a group authorized to learn processes information otherwise
1954	prohibited by hidepid=.  If you use some daemon like identd which needs to learn
1955	information about processes information, just add identd to this group.
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