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Based on kernel version 4.8. Page generated on 2016-10-06 23:16 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	
48	  4	Configuring procfs
49	  4.1	Mount options
50	
51	------------------------------------------------------------------------------
52	Preface
53	------------------------------------------------------------------------------
54	
55	0.1 Introduction/Credits
56	------------------------
57	
58	This documentation is  part of a soon (or  so we hope) to be  released book on
59	the SuSE  Linux distribution. As  there is  no complete documentation  for the
60	/proc file system and we've used  many freely available sources to write these
61	chapters, it  seems only fair  to give the work  back to the  Linux community.
62	This work is  based on the 2.2.*  kernel version and the  upcoming 2.4.*. I'm
63	afraid it's still far from complete, but we  hope it will be useful. As far as
64	we know, it is the first 'all-in-one' document about the /proc file system. It
65	is focused  on the Intel  x86 hardware,  so if you  are looking for  PPC, ARM,
66	SPARC, AXP, etc., features, you probably  won't find what you are looking for.
67	It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
68	additions and patches  are welcome and will  be added to this  document if you
69	mail them to Bodo.
70	
71	We'd like  to  thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
72	other people for help compiling this documentation. We'd also like to extend a
73	special thank  you to Andi Kleen for documentation, which we relied on heavily
74	to create  this  document,  as well as the additional information he provided.
75	Thanks to  everybody  else  who contributed source or docs to the Linux kernel
76	and helped create a great piece of software... :)
77	
78	If you  have  any comments, corrections or additions, please don't hesitate to
79	contact Bodo  Bauer  at  bb@ricochet.net.  We'll  be happy to add them to this
80	document.
81	
82	The   latest   version    of   this   document   is    available   online   at
83	http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
84	
85	If  the above  direction does  not works  for you,  you could  try the  kernel
86	mailing  list  at  linux-kernel@vger.kernel.org  and/or try  to  reach  me  at
87	comandante@zaralinux.com.
88	
89	0.2 Legal Stuff
90	---------------
91	
92	We don't  guarantee  the  correctness  of this document, and if you come to us
93	complaining about  how  you  screwed  up  your  system  because  of  incorrect
94	documentation, we won't feel responsible...
95	
96	------------------------------------------------------------------------------
97	CHAPTER 1: COLLECTING SYSTEM INFORMATION
98	------------------------------------------------------------------------------
99	
100	------------------------------------------------------------------------------
101	In This Chapter
102	------------------------------------------------------------------------------
103	* Investigating  the  properties  of  the  pseudo  file  system  /proc and its
104	  ability to provide information on the running Linux system
105	* Examining /proc's structure
106	* Uncovering  various  information  about the kernel and the processes running
107	  on the system
108	------------------------------------------------------------------------------
109	
110	
111	The proc  file  system acts as an interface to internal data structures in the
112	kernel. It  can  be  used to obtain information about the system and to change
113	certain kernel parameters at runtime (sysctl).
114	
115	First, we'll  take  a  look  at the read-only parts of /proc. In Chapter 2, we
116	show you how you can use /proc/sys to change settings.
117	
118	1.1 Process-Specific Subdirectories
119	-----------------------------------
120	
121	The directory  /proc  contains  (among other things) one subdirectory for each
122	process running on the system, which is named after the process ID (PID).
123	
124	The link  self  points  to  the  process reading the file system. Each process
125	subdirectory has the entries listed in Table 1-1.
126	
127	
128	Table 1-1: Process specific entries in /proc
129	..............................................................................
130	 File		Content
131	 clear_refs	Clears page referenced bits shown in smaps output
132	 cmdline	Command line arguments
133	 cpu		Current and last cpu in which it was executed	(2.4)(smp)
134	 cwd		Link to the current working directory
135	 environ	Values of environment variables
136	 exe		Link to the executable of this process
137	 fd		Directory, which contains all file descriptors
138	 maps		Memory maps to executables and library files	(2.4)
139	 mem		Memory held by this process
140	 root		Link to the root directory of this process
141	 stat		Process status
142	 statm		Process memory status information
143	 status		Process status in human readable form
144	 wchan		Present with CONFIG_KALLSYMS=y: it shows the kernel function
145			symbol the task is blocked in - or "0" if not blocked.
146	 pagemap	Page table
147	 stack		Report full stack trace, enable via CONFIG_STACKTRACE
148	 smaps		a extension based on maps, showing the memory consumption of
149			each mapping and flags associated with it
150	 numa_maps	an extension based on maps, showing the memory locality and
151			binding policy as well as mem usage (in pages) of each mapping.
152	..............................................................................
153	
154	For example, to get the status information of a process, all you have to do is
155	read the file /proc/PID/status:
156	
157	  >cat /proc/self/status
158	  Name:   cat
159	  State:  R (running)
160	  Tgid:   5452
161	  Pid:    5452
162	  PPid:   743
163	  TracerPid:      0						(2.4)
164	  Uid:    501     501     501     501
165	  Gid:    100     100     100     100
166	  FDSize: 256
167	  Groups: 100 14 16
168	  VmPeak:     5004 kB
169	  VmSize:     5004 kB
170	  VmLck:         0 kB
171	  VmHWM:       476 kB
172	  VmRSS:       476 kB
173	  RssAnon:             352 kB
174	  RssFile:             120 kB
175	  RssShmem:              4 kB
176	  VmData:      156 kB
177	  VmStk:        88 kB
178	  VmExe:        68 kB
179	  VmLib:      1412 kB
180	  VmPTE:        20 kb
181	  VmSwap:        0 kB
182	  HugetlbPages:          0 kB
183	  Threads:        1
184	  SigQ:   0/28578
185	  SigPnd: 0000000000000000
186	  ShdPnd: 0000000000000000
187	  SigBlk: 0000000000000000
188	  SigIgn: 0000000000000000
189	  SigCgt: 0000000000000000
190	  CapInh: 00000000fffffeff
191	  CapPrm: 0000000000000000
192	  CapEff: 0000000000000000
193	  CapBnd: ffffffffffffffff
194	  Seccomp:        0
195	  voluntary_ctxt_switches:        0
196	  nonvoluntary_ctxt_switches:     1
197	
198	This shows you nearly the same information you would get if you viewed it with
199	the ps  command.  In  fact,  ps  uses  the  proc  file  system  to  obtain its
200	information.  But you get a more detailed  view of the  process by reading the
201	file /proc/PID/status. It fields are described in table 1-2.
202	
203	The  statm  file  contains  more  detailed  information about the process
204	memory usage. Its seven fields are explained in Table 1-3.  The stat file
205	contains details information about the process itself.  Its fields are
206	explained in Table 1-4.
207	
208	(for SMP CONFIG users)
209	For making accounting scalable, RSS related information are handled in an
210	asynchronous manner and the value may not be very precise. To see a precise
211	snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
212	It's slow but very precise.
213	
214	Table 1-2: Contents of the status files (as of 4.1)
215	..............................................................................
216	 Field                       Content
217	 Name                        filename of the executable
218	 State                       state (R is running, S is sleeping, D is sleeping
219	                             in an uninterruptible wait, Z is zombie,
220				     T is traced or stopped)
221	 Tgid                        thread group ID
222	 Ngid                        NUMA group ID (0 if none)
223	 Pid                         process id
224	 PPid                        process id of the parent process
225	 TracerPid                   PID of process tracing this process (0 if not)
226	 Uid                         Real, effective, saved set, and  file system UIDs
227	 Gid                         Real, effective, saved set, and  file system GIDs
228	 Umask                       file mode creation mask
229	 FDSize                      number of file descriptor slots currently allocated
230	 Groups                      supplementary group list
231	 NStgid                      descendant namespace thread group ID hierarchy
232	 NSpid                       descendant namespace process ID hierarchy
233	 NSpgid                      descendant namespace process group ID hierarchy
234	 NSsid                       descendant namespace session ID hierarchy
235	 VmPeak                      peak virtual memory size
236	 VmSize                      total program size
237	 VmLck                       locked memory size
238	 VmHWM                       peak resident set size ("high water mark")
239	 VmRSS                       size of memory portions. It contains the three
240	                             following parts (VmRSS = RssAnon + RssFile + RssShmem)
241	 RssAnon                     size of resident anonymous memory
242	 RssFile                     size of resident file mappings
243	 RssShmem                    size of resident shmem memory (includes SysV shm,
244	                             mapping of tmpfs and shared anonymous mappings)
245	 VmData                      size of private data segments
246	 VmStk                       size of stack segments
247	 VmExe                       size of text segment
248	 VmLib                       size of shared library code
249	 VmPTE                       size of page table entries
250	 VmPMD                       size of second level page tables
251	 VmSwap                      amount of swap used by anonymous private data
252	                             (shmem swap usage is not included)
253	 HugetlbPages                size of hugetlb memory portions
254	 Threads                     number of threads
255	 SigQ                        number of signals queued/max. number for queue
256	 SigPnd                      bitmap of pending signals for the thread
257	 ShdPnd                      bitmap of shared pending signals for the process
258	 SigBlk                      bitmap of blocked signals
259	 SigIgn                      bitmap of ignored signals
260	 SigCgt                      bitmap of caught signals
261	 CapInh                      bitmap of inheritable capabilities
262	 CapPrm                      bitmap of permitted capabilities
263	 CapEff                      bitmap of effective capabilities
264	 CapBnd                      bitmap of capabilities bounding set
265	 Seccomp                     seccomp mode, like prctl(PR_GET_SECCOMP, ...)
266	 Cpus_allowed                mask of CPUs on which this process may run
267	 Cpus_allowed_list           Same as previous, but in "list format"
268	 Mems_allowed                mask of memory nodes allowed to this process
269	 Mems_allowed_list           Same as previous, but in "list format"
270	 voluntary_ctxt_switches     number of voluntary context switches
271	 nonvoluntary_ctxt_switches  number of non voluntary context switches
272	..............................................................................
273	
274	Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
275	..............................................................................
276	 Field    Content
277	 size     total program size (pages)		(same as VmSize in status)
278	 resident size of memory portions (pages)	(same as VmRSS in status)
279	 shared   number of pages that are shared	(i.e. backed by a file, same
280							as RssFile+RssShmem in status)
281	 trs      number of pages that are 'code'	(not including libs; broken,
282								includes data segment)
283	 lrs      number of pages of library		(always 0 on 2.6)
284	 drs      number of pages of data/stack		(including libs; broken,
285								includes library text)
286	 dt       number of dirty pages			(always 0 on 2.6)
287	..............................................................................
288	
289	
290	Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
291	..............................................................................
292	 Field          Content
293	  pid           process id
294	  tcomm         filename of the executable
295	  state         state (R is running, S is sleeping, D is sleeping in an
296	                uninterruptible wait, Z is zombie, T is traced or stopped)
297	  ppid          process id of the parent process
298	  pgrp          pgrp of the process
299	  sid           session id
300	  tty_nr        tty the process uses
301	  tty_pgrp      pgrp of the tty
302	  flags         task flags
303	  min_flt       number of minor faults
304	  cmin_flt      number of minor faults with child's
305	  maj_flt       number of major faults
306	  cmaj_flt      number of major faults with child's
307	  utime         user mode jiffies
308	  stime         kernel mode jiffies
309	  cutime        user mode jiffies with child's
310	  cstime        kernel mode jiffies with child's
311	  priority      priority level
312	  nice          nice level
313	  num_threads   number of threads
314	  it_real_value	(obsolete, always 0)
315	  start_time    time the process started after system boot
316	  vsize         virtual memory size
317	  rss           resident set memory size
318	  rsslim        current limit in bytes on the rss
319	  start_code    address above which program text can run
320	  end_code      address below which program text can run
321	  start_stack   address of the start of the main process stack
322	  esp           current value of ESP
323	  eip           current value of EIP
324	  pending       bitmap of pending signals
325	  blocked       bitmap of blocked signals
326	  sigign        bitmap of ignored signals
327	  sigcatch      bitmap of caught signals
328	  0		(place holder, used to be the wchan address, use /proc/PID/wchan instead)
329	  0             (place holder)
330	  0             (place holder)
331	  exit_signal   signal to send to parent thread on exit
332	  task_cpu      which CPU the task is scheduled on
333	  rt_priority   realtime priority
334	  policy        scheduling policy (man sched_setscheduler)
335	  blkio_ticks   time spent waiting for block IO
336	  gtime         guest time of the task in jiffies
337	  cgtime        guest time of the task children in jiffies
338	  start_data    address above which program data+bss is placed
339	  end_data      address below which program data+bss is placed
340	  start_brk     address above which program heap can be expanded with brk()
341	  arg_start     address above which program command line is placed
342	  arg_end       address below which program command line is placed
343	  env_start     address above which program environment is placed
344	  env_end       address below which program environment is placed
345	  exit_code     the thread's exit_code in the form reported by the waitpid system call
346	..............................................................................
347	
348	The /proc/PID/maps file containing the currently mapped memory regions and
349	their access permissions.
350	
351	The format is:
352	
353	address           perms offset  dev   inode      pathname
354	
355	08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
356	08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
357	0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
358	a7cb1000-a7cb2000 ---p 00000000 00:00 0
359	a7cb2000-a7eb2000 rw-p 00000000 00:00 0
360	a7eb2000-a7eb3000 ---p 00000000 00:00 0
361	a7eb3000-a7ed5000 rw-p 00000000 00:00 0
362	a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
363	a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
364	a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
365	a800b000-a800e000 rw-p 00000000 00:00 0
366	a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
367	a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
368	a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
369	a8024000-a8027000 rw-p 00000000 00:00 0
370	a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
371	a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
372	a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
373	aff35000-aff4a000 rw-p 00000000 00:00 0          [stack]
374	ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
375	
376	where "address" is the address space in the process that it occupies, "perms"
377	is a set of permissions:
378	
379	 r = read
380	 w = write
381	 x = execute
382	 s = shared
383	 p = private (copy on write)
384	
385	"offset" is the offset into the mapping, "dev" is the device (major:minor), and
386	"inode" is the inode  on that device.  0 indicates that  no inode is associated
387	with the memory region, as the case would be with BSS (uninitialized data).
388	The "pathname" shows the name associated file for this mapping.  If the mapping
389	is not associated with a file:
390	
391	 [heap]                   = the heap of the program
392	 [stack]                  = the stack of the main process
393	 [vdso]                   = the "virtual dynamic shared object",
394	                            the kernel system call handler
395	
396	 or if empty, the mapping is anonymous.
397	
398	The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint
399	of the individual tasks of a process. In this file you will see a mapping marked
400	as [stack] if that task sees it as a stack. Hence, for the example above, the
401	task-level map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this:
402	
403	08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
404	08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
405	0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
406	a7cb1000-a7cb2000 ---p 00000000 00:00 0
407	a7cb2000-a7eb2000 rw-p 00000000 00:00 0
408	a7eb2000-a7eb3000 ---p 00000000 00:00 0
409	a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack]
410	a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
411	a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
412	a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
413	a800b000-a800e000 rw-p 00000000 00:00 0
414	a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
415	a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
416	a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
417	a8024000-a8027000 rw-p 00000000 00:00 0
418	a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
419	a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
420	a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
421	aff35000-aff4a000 rw-p 00000000 00:00 0
422	ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
423	
424	The /proc/PID/smaps is an extension based on maps, showing the memory
425	consumption for each of the process's mappings. For each of mappings there
426	is a series of lines such as the following:
427	
428	08048000-080bc000 r-xp 00000000 03:02 13130      /bin/bash
429	Size:               1084 kB
430	Rss:                 892 kB
431	Pss:                 374 kB
432	Shared_Clean:        892 kB
433	Shared_Dirty:          0 kB
434	Private_Clean:         0 kB
435	Private_Dirty:         0 kB
436	Referenced:          892 kB
437	Anonymous:             0 kB
438	AnonHugePages:         0 kB
439	ShmemPmdMapped:        0 kB
440	Shared_Hugetlb:        0 kB
441	Private_Hugetlb:       0 kB
442	Swap:                  0 kB
443	SwapPss:               0 kB
444	KernelPageSize:        4 kB
445	MMUPageSize:           4 kB
446	Locked:                0 kB
447	VmFlags: rd ex mr mw me dw
448	
449	the first of these lines shows the same information as is displayed for the
450	mapping in /proc/PID/maps.  The remaining lines show the size of the mapping
451	(size), the amount of the mapping that is currently resident in RAM (RSS), the
452	process' proportional share of this mapping (PSS), the number of clean and
453	dirty private pages in the mapping.
454	
455	The "proportional set size" (PSS) of a process is the count of pages it has
456	in memory, where each page is divided by the number of processes sharing it.
457	So if a process has 1000 pages all to itself, and 1000 shared with one other
458	process, its PSS will be 1500.
459	Note that even a page which is part of a MAP_SHARED mapping, but has only
460	a single pte mapped, i.e.  is currently used by only one process, is accounted
461	as private and not as shared.
462	"Referenced" indicates the amount of memory currently marked as referenced or
463	accessed.
464	"Anonymous" shows the amount of memory that does not belong to any file.  Even
465	a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
466	and a page is modified, the file page is replaced by a private anonymous copy.
467	"AnonHugePages" shows the ammount of memory backed by transparent hugepage.
468	"ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by
469	huge pages.
470	"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
471	hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
472	reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
473	"Swap" shows how much would-be-anonymous memory is also used, but out on swap.
474	For shmem mappings, "Swap" includes also the size of the mapped (and not
475	replaced by copy-on-write) part of the underlying shmem object out on swap.
476	"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
477	does not take into account swapped out page of underlying shmem objects.
478	"Locked" indicates whether the mapping is locked in memory or not.
479	
480	"VmFlags" field deserves a separate description. This member represents the kernel
481	flags associated with the particular virtual memory area in two letter encoded
482	manner. The codes are the following:
483	    rd  - readable
484	    wr  - writeable
485	    ex  - executable
486	    sh  - shared
487	    mr  - may read
488	    mw  - may write
489	    me  - may execute
490	    ms  - may share
491	    gd  - stack segment growns down
492	    pf  - pure PFN range
493	    dw  - disabled write to the mapped file
494	    lo  - pages are locked in memory
495	    io  - memory mapped I/O area
496	    sr  - sequential read advise provided
497	    rr  - random read advise provided
498	    dc  - do not copy area on fork
499	    de  - do not expand area on remapping
500	    ac  - area is accountable
501	    nr  - swap space is not reserved for the area
502	    ht  - area uses huge tlb pages
503	    ar  - architecture specific flag
504	    dd  - do not include area into core dump
505	    sd  - soft-dirty flag
506	    mm  - mixed map area
507	    hg  - huge page advise flag
508	    nh  - no-huge page advise flag
509	    mg  - mergable advise flag
510	
511	Note that there is no guarantee that every flag and associated mnemonic will
512	be present in all further kernel releases. Things get changed, the flags may
513	be vanished or the reverse -- new added.
514	
515	This file is only present if the CONFIG_MMU kernel configuration option is
516	enabled.
517	
518	The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
519	bits on both physical and virtual pages associated with a process, and the
520	soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details).
521	To clear the bits for all the pages associated with the process
522	    > echo 1 > /proc/PID/clear_refs
523	
524	To clear the bits for the anonymous pages associated with the process
525	    > echo 2 > /proc/PID/clear_refs
526	
527	To clear the bits for the file mapped pages associated with the process
528	    > echo 3 > /proc/PID/clear_refs
529	
530	To clear the soft-dirty bit
531	    > echo 4 > /proc/PID/clear_refs
532	
533	To reset the peak resident set size ("high water mark") to the process's
534	current value:
535	    > echo 5 > /proc/PID/clear_refs
536	
537	Any other value written to /proc/PID/clear_refs will have no effect.
538	
539	The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
540	using /proc/kpageflags and number of times a page is mapped using
541	/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
542	
543	The /proc/pid/numa_maps is an extension based on maps, showing the memory
544	locality and binding policy, as well as the memory usage (in pages) of
545	each mapping. The output follows a general format where mapping details get
546	summarized separated by blank spaces, one mapping per each file line:
547	
548	address   policy    mapping details
549	
550	00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
551	00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
552	3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
553	320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
554	3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
555	3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
556	3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
557	320698b000 default file=/lib64/libc-2.12.so
558	3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
559	3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
560	3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
561	7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
562	7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
563	7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
564	7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
565	7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
566	
567	Where:
568	"address" is the starting address for the mapping;
569	"policy" reports the NUMA memory policy set for the mapping (see vm/numa_memory_policy.txt);
570	"mapping details" summarizes mapping data such as mapping type, page usage counters,
571	node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
572	size, in KB, that is backing the mapping up.
573	
574	1.2 Kernel data
575	---------------
576	
577	Similar to  the  process entries, the kernel data files give information about
578	the running kernel. The files used to obtain this information are contained in
579	/proc and  are  listed  in Table 1-5. Not all of these will be present in your
580	system. It  depends  on the kernel configuration and the loaded modules, which
581	files are there, and which are missing.
582	
583	Table 1-5: Kernel info in /proc
584	..............................................................................
585	 File        Content                                           
586	 apm         Advanced power management info                    
587	 buddyinfo   Kernel memory allocator information (see text)	(2.5)
588	 bus         Directory containing bus specific information     
589	 cmdline     Kernel command line                               
590	 cpuinfo     Info about the CPU                                
591	 devices     Available devices (block and character)           
592	 dma         Used DMS channels                                 
593	 filesystems Supported filesystems                             
594	 driver	     Various drivers grouped here, currently rtc (2.4)
595	 execdomains Execdomains, related to security			(2.4)
596	 fb	     Frame Buffer devices				(2.4)
597	 fs	     File system parameters, currently nfs/exports	(2.4)
598	 ide         Directory containing info about the IDE subsystem 
599	 interrupts  Interrupt usage                                   
600	 iomem	     Memory map						(2.4)
601	 ioports     I/O port usage                                    
602	 irq	     Masks for irq to cpu affinity			(2.4)(smp?)
603	 isapnp	     ISA PnP (Plug&Play) Info				(2.4)
604	 kcore       Kernel core image (can be ELF or A.OUT(deprecated in 2.4))   
605	 kmsg        Kernel messages                                   
606	 ksyms       Kernel symbol table                               
607	 loadavg     Load average of last 1, 5 & 15 minutes                
608	 locks       Kernel locks                                      
609	 meminfo     Memory info                                       
610	 misc        Miscellaneous                                     
611	 modules     List of loaded modules                            
612	 mounts      Mounted filesystems                               
613	 net         Networking info (see text)                        
614	 pagetypeinfo Additional page allocator information (see text)  (2.5)
615	 partitions  Table of partitions known to the system           
616	 pci	     Deprecated info of PCI bus (new way -> /proc/bus/pci/,
617	             decoupled by lspci					(2.4)
618	 rtc         Real time clock                                   
619	 scsi        SCSI info (see text)                              
620	 slabinfo    Slab pool info                                    
621	 softirqs    softirq usage
622	 stat        Overall statistics                                
623	 swaps       Swap space utilization                            
624	 sys         See chapter 2                                     
625	 sysvipc     Info of SysVIPC Resources (msg, sem, shm)		(2.4)
626	 tty	     Info of tty drivers
627	 uptime      Wall clock since boot, combined idle time of all cpus
628	 version     Kernel version                                    
629	 video	     bttv info of video resources			(2.4)
630	 vmallocinfo Show vmalloced areas
631	..............................................................................
632	
633	You can,  for  example,  check  which interrupts are currently in use and what
634	they are used for by looking in the file /proc/interrupts:
635	
636	  > cat /proc/interrupts 
637	             CPU0        
638	    0:    8728810          XT-PIC  timer 
639	    1:        895          XT-PIC  keyboard 
640	    2:          0          XT-PIC  cascade 
641	    3:     531695          XT-PIC  aha152x 
642	    4:    2014133          XT-PIC  serial 
643	    5:      44401          XT-PIC  pcnet_cs 
644	    8:          2          XT-PIC  rtc 
645	   11:          8          XT-PIC  i82365 
646	   12:     182918          XT-PIC  PS/2 Mouse 
647	   13:          1          XT-PIC  fpu 
648	   14:    1232265          XT-PIC  ide0 
649	   15:          7          XT-PIC  ide1 
650	  NMI:          0 
651	
652	In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
653	output of a SMP machine):
654	
655	  > cat /proc/interrupts 
656	
657	             CPU0       CPU1       
658	    0:    1243498    1214548    IO-APIC-edge  timer
659	    1:       8949       8958    IO-APIC-edge  keyboard
660	    2:          0          0          XT-PIC  cascade
661	    5:      11286      10161    IO-APIC-edge  soundblaster
662	    8:          1          0    IO-APIC-edge  rtc
663	    9:      27422      27407    IO-APIC-edge  3c503
664	   12:     113645     113873    IO-APIC-edge  PS/2 Mouse
665	   13:          0          0          XT-PIC  fpu
666	   14:      22491      24012    IO-APIC-edge  ide0
667	   15:       2183       2415    IO-APIC-edge  ide1
668	   17:      30564      30414   IO-APIC-level  eth0
669	   18:        177        164   IO-APIC-level  bttv
670	  NMI:    2457961    2457959 
671	  LOC:    2457882    2457881 
672	  ERR:       2155
673	
674	NMI is incremented in this case because every timer interrupt generates a NMI
675	(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
676	
677	LOC is the local interrupt counter of the internal APIC of every CPU.
678	
679	ERR is incremented in the case of errors in the IO-APIC bus (the bus that
680	connects the CPUs in a SMP system. This means that an error has been detected,
681	the IO-APIC automatically retry the transmission, so it should not be a big
682	problem, but you should read the SMP-FAQ.
683	
684	In 2.6.2* /proc/interrupts was expanded again.  This time the goal was for
685	/proc/interrupts to display every IRQ vector in use by the system, not
686	just those considered 'most important'.  The new vectors are:
687	
688	  THR -- interrupt raised when a machine check threshold counter
689	  (typically counting ECC corrected errors of memory or cache) exceeds
690	  a configurable threshold.  Only available on some systems.
691	
692	  TRM -- a thermal event interrupt occurs when a temperature threshold
693	  has been exceeded for the CPU.  This interrupt may also be generated
694	  when the temperature drops back to normal.
695	
696	  SPU -- a spurious interrupt is some interrupt that was raised then lowered
697	  by some IO device before it could be fully processed by the APIC.  Hence
698	  the APIC sees the interrupt but does not know what device it came from.
699	  For this case the APIC will generate the interrupt with a IRQ vector
700	  of 0xff. This might also be generated by chipset bugs.
701	
702	  RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
703	  sent from one CPU to another per the needs of the OS.  Typically,
704	  their statistics are used by kernel developers and interested users to
705	  determine the occurrence of interrupts of the given type.
706	
707	The above IRQ vectors are displayed only when relevant.  For example,
708	the threshold vector does not exist on x86_64 platforms.  Others are
709	suppressed when the system is a uniprocessor.  As of this writing, only
710	i386 and x86_64 platforms support the new IRQ vector displays.
711	
712	Of some interest is the introduction of the /proc/irq directory to 2.4.
713	It could be used to set IRQ to CPU affinity, this means that you can "hook" an
714	IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
715	irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
716	prof_cpu_mask.
717	
718	For example 
719	  > ls /proc/irq/
720	  0  10  12  14  16  18  2  4  6  8  prof_cpu_mask
721	  1  11  13  15  17  19  3  5  7  9  default_smp_affinity
722	  > ls /proc/irq/0/
723	  smp_affinity
724	
725	smp_affinity is a bitmask, in which you can specify which CPUs can handle the
726	IRQ, you can set it by doing:
727	
728	  > echo 1 > /proc/irq/10/smp_affinity
729	
730	This means that only the first CPU will handle the IRQ, but you can also echo
731	5 which means that only the first and third CPU can handle the IRQ.
732	
733	The contents of each smp_affinity file is the same by default:
734	
735	  > cat /proc/irq/0/smp_affinity
736	  ffffffff
737	
738	There is an alternate interface, smp_affinity_list which allows specifying
739	a cpu range instead of a bitmask:
740	
741	  > cat /proc/irq/0/smp_affinity_list
742	  1024-1031
743	
744	The default_smp_affinity mask applies to all non-active IRQs, which are the
745	IRQs which have not yet been allocated/activated, and hence which lack a
746	/proc/irq/[0-9]* directory.
747	
748	The node file on an SMP system shows the node to which the device using the IRQ
749	reports itself as being attached. This hardware locality information does not
750	include information about any possible driver locality preference.
751	
752	prof_cpu_mask specifies which CPUs are to be profiled by the system wide
753	profiler. Default value is ffffffff (all cpus if there are only 32 of them).
754	
755	The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
756	between all the CPUs which are allowed to handle it. As usual the kernel has
757	more info than you and does a better job than you, so the defaults are the
758	best choice for almost everyone.  [Note this applies only to those IO-APIC's
759	that support "Round Robin" interrupt distribution.]
760	
761	There are  three  more  important subdirectories in /proc: net, scsi, and sys.
762	The general  rule  is  that  the  contents,  or  even  the  existence of these
763	directories, depend  on your kernel configuration. If SCSI is not enabled, the
764	directory scsi  may  not  exist. The same is true with the net, which is there
765	only when networking support is present in the running kernel.
766	
767	The slabinfo  file  gives  information  about  memory usage at the slab level.
768	Linux uses  slab  pools for memory management above page level in version 2.2.
769	Commonly used  objects  have  their  own  slab  pool (such as network buffers,
770	directory cache, and so on).
771	
772	..............................................................................
773	
774	> cat /proc/buddyinfo
775	
776	Node 0, zone      DMA      0      4      5      4      4      3 ...
777	Node 0, zone   Normal      1      0      0      1    101      8 ...
778	Node 0, zone  HighMem      2      0      0      1      1      0 ...
779	
780	External fragmentation is a problem under some workloads, and buddyinfo is a
781	useful tool for helping diagnose these problems.  Buddyinfo will give you a 
782	clue as to how big an area you can safely allocate, or why a previous
783	allocation failed.
784	
785	Each column represents the number of pages of a certain order which are 
786	available.  In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 
787	ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 
788	available in ZONE_NORMAL, etc... 
789	
790	More information relevant to external fragmentation can be found in
791	pagetypeinfo.
792	
793	> cat /proc/pagetypeinfo
794	Page block order: 9
795	Pages per block:  512
796	
797	Free pages count per migrate type at order       0      1      2      3      4      5      6      7      8      9     10
798	Node    0, zone      DMA, type    Unmovable      0      0      0      1      1      1      1      1      1      1      0
799	Node    0, zone      DMA, type  Reclaimable      0      0      0      0      0      0      0      0      0      0      0
800	Node    0, zone      DMA, type      Movable      1      1      2      1      2      1      1      0      1      0      2
801	Node    0, zone      DMA, type      Reserve      0      0      0      0      0      0      0      0      0      1      0
802	Node    0, zone      DMA, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
803	Node    0, zone    DMA32, type    Unmovable    103     54     77      1      1      1     11      8      7      1      9
804	Node    0, zone    DMA32, type  Reclaimable      0      0      2      1      0      0      0      0      1      0      0
805	Node    0, zone    DMA32, type      Movable    169    152    113     91     77     54     39     13      6      1    452
806	Node    0, zone    DMA32, type      Reserve      1      2      2      2      2      0      1      1      1      1      0
807	Node    0, zone    DMA32, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
808	
809	Number of blocks type     Unmovable  Reclaimable      Movable      Reserve      Isolate
810	Node 0, zone      DMA            2            0            5            1            0
811	Node 0, zone    DMA32           41            6          967            2            0
812	
813	Fragmentation avoidance in the kernel works by grouping pages of different
814	migrate types into the same contiguous regions of memory called page blocks.
815	A page block is typically the size of the default hugepage size e.g. 2MB on
816	X86-64. By keeping pages grouped based on their ability to move, the kernel
817	can reclaim pages within a page block to satisfy a high-order allocation.
818	
819	The pagetypinfo begins with information on the size of a page block. It
820	then gives the same type of information as buddyinfo except broken down
821	by migrate-type and finishes with details on how many page blocks of each
822	type exist.
823	
824	If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
825	from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
826	make an estimate of the likely number of huge pages that can be allocated
827	at a given point in time. All the "Movable" blocks should be allocatable
828	unless memory has been mlock()'d. Some of the Reclaimable blocks should
829	also be allocatable although a lot of filesystem metadata may have to be
830	reclaimed to achieve this.
831	
832	..............................................................................
833	
834	meminfo:
835	
836	Provides information about distribution and utilization of memory.  This
837	varies by architecture and compile options.  The following is from a
838	16GB PIII, which has highmem enabled.  You may not have all of these fields.
839	
840	> cat /proc/meminfo
841	
842	MemTotal:     16344972 kB
843	MemFree:      13634064 kB
844	MemAvailable: 14836172 kB
845	Buffers:          3656 kB
846	Cached:        1195708 kB
847	SwapCached:          0 kB
848	Active:         891636 kB
849	Inactive:      1077224 kB
850	HighTotal:    15597528 kB
851	HighFree:     13629632 kB
852	LowTotal:       747444 kB
853	LowFree:          4432 kB
854	SwapTotal:           0 kB
855	SwapFree:            0 kB
856	Dirty:             968 kB
857	Writeback:           0 kB
858	AnonPages:      861800 kB
859	Mapped:         280372 kB
860	Shmem:             644 kB
861	Slab:           284364 kB
862	SReclaimable:   159856 kB
863	SUnreclaim:     124508 kB
864	PageTables:      24448 kB
865	NFS_Unstable:        0 kB
866	Bounce:              0 kB
867	WritebackTmp:        0 kB
868	CommitLimit:   7669796 kB
869	Committed_AS:   100056 kB
870	VmallocTotal:   112216 kB
871	VmallocUsed:       428 kB
872	VmallocChunk:   111088 kB
873	AnonHugePages:   49152 kB
874	ShmemHugePages:      0 kB
875	ShmemPmdMapped:      0 kB
876	
877	
878	    MemTotal: Total usable ram (i.e. physical ram minus a few reserved
879	              bits and the kernel binary code)
880	     MemFree: The sum of LowFree+HighFree
881	MemAvailable: An estimate of how much memory is available for starting new
882	              applications, without swapping. Calculated from MemFree,
883	              SReclaimable, the size of the file LRU lists, and the low
884	              watermarks in each zone.
885	              The estimate takes into account that the system needs some
886	              page cache to function well, and that not all reclaimable
887	              slab will be reclaimable, due to items being in use. The
888	              impact of those factors will vary from system to system.
889	     Buffers: Relatively temporary storage for raw disk blocks
890	              shouldn't get tremendously large (20MB or so)
891	      Cached: in-memory cache for files read from the disk (the
892	              pagecache).  Doesn't include SwapCached
893	  SwapCached: Memory that once was swapped out, is swapped back in but
894	              still also is in the swapfile (if memory is needed it
895	              doesn't need to be swapped out AGAIN because it is already
896	              in the swapfile. This saves I/O)
897	      Active: Memory that has been used more recently and usually not
898	              reclaimed unless absolutely necessary.
899	    Inactive: Memory which has been less recently used.  It is more
900	              eligible to be reclaimed for other purposes
901	   HighTotal:
902	    HighFree: Highmem is all memory above ~860MB of physical memory
903	              Highmem areas are for use by userspace programs, or
904	              for the pagecache.  The kernel must use tricks to access
905	              this memory, making it slower to access than lowmem.
906	    LowTotal:
907	     LowFree: Lowmem is memory which can be used for everything that
908	              highmem can be used for, but it is also available for the
909	              kernel's use for its own data structures.  Among many
910	              other things, it is where everything from the Slab is
911	              allocated.  Bad things happen when you're out of lowmem.
912	   SwapTotal: total amount of swap space available
913	    SwapFree: Memory which has been evicted from RAM, and is temporarily
914	              on the disk
915	       Dirty: Memory which is waiting to get written back to the disk
916	   Writeback: Memory which is actively being written back to the disk
917	   AnonPages: Non-file backed pages mapped into userspace page tables
918	AnonHugePages: Non-file backed huge pages mapped into userspace page tables
919	      Mapped: files which have been mmaped, such as libraries
920	       Shmem: Total memory used by shared memory (shmem) and tmpfs
921	ShmemHugePages: Memory used by shared memory (shmem) and tmpfs allocated
922	              with huge pages
923	ShmemPmdMapped: Shared memory mapped into userspace with huge pages
924	        Slab: in-kernel data structures cache
925	SReclaimable: Part of Slab, that might be reclaimed, such as caches
926	  SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
927	  PageTables: amount of memory dedicated to the lowest level of page
928	              tables.
929	NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
930		      storage
931	      Bounce: Memory used for block device "bounce buffers"
932	WritebackTmp: Memory used by FUSE for temporary writeback buffers
933	 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
934	              this is the total amount of  memory currently available to
935	              be allocated on the system. This limit is only adhered to
936	              if strict overcommit accounting is enabled (mode 2 in
937	              'vm.overcommit_memory').
938	              The CommitLimit is calculated with the following formula:
939	              CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
940	                             overcommit_ratio / 100 + [total swap pages]
941	              For example, on a system with 1G of physical RAM and 7G
942	              of swap with a `vm.overcommit_ratio` of 30 it would
943	              yield a CommitLimit of 7.3G.
944	              For more details, see the memory overcommit documentation
945	              in vm/overcommit-accounting.
946	Committed_AS: The amount of memory presently allocated on the system.
947	              The committed memory is a sum of all of the memory which
948	              has been allocated by processes, even if it has not been
949	              "used" by them as of yet. A process which malloc()'s 1G
950	              of memory, but only touches 300M of it will show up as
951		      using 1G. This 1G is memory which has been "committed" to
952	              by the VM and can be used at any time by the allocating
953	              application. With strict overcommit enabled on the system
954	              (mode 2 in 'vm.overcommit_memory'),allocations which would
955	              exceed the CommitLimit (detailed above) will not be permitted.
956	              This is useful if one needs to guarantee that processes will
957	              not fail due to lack of memory once that memory has been
958	              successfully allocated.
959	VmallocTotal: total size of vmalloc memory area
960	 VmallocUsed: amount of vmalloc area which is used
961	VmallocChunk: largest contiguous block of vmalloc area which is free
962	
963	..............................................................................
964	
965	vmallocinfo:
966	
967	Provides information about vmalloced/vmaped areas. One line per area,
968	containing the virtual address range of the area, size in bytes,
969	caller information of the creator, and optional information depending
970	on the kind of area :
971	
972	 pages=nr    number of pages
973	 phys=addr   if a physical address was specified
974	 ioremap     I/O mapping (ioremap() and friends)
975	 vmalloc     vmalloc() area
976	 vmap        vmap()ed pages
977	 user        VM_USERMAP area
978	 vpages      buffer for pages pointers was vmalloced (huge area)
979	 N<node>=nr  (Only on NUMA kernels)
980	             Number of pages allocated on memory node <node>
981	
982	> cat /proc/vmallocinfo
983	0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
984	  /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
985	0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
986	  /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
987	0xffffc20000302000-0xffffc20000304000    8192 acpi_tb_verify_table+0x21/0x4f...
988	  phys=7fee8000 ioremap
989	0xffffc20000304000-0xffffc20000307000   12288 acpi_tb_verify_table+0x21/0x4f...
990	  phys=7fee7000 ioremap
991	0xffffc2000031d000-0xffffc2000031f000    8192 init_vdso_vars+0x112/0x210
992	0xffffc2000031f000-0xffffc2000032b000   49152 cramfs_uncompress_init+0x2e ...
993	  /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
994	0xffffc2000033a000-0xffffc2000033d000   12288 sys_swapon+0x640/0xac0      ...
995	  pages=2 vmalloc N1=2
996	0xffffc20000347000-0xffffc2000034c000   20480 xt_alloc_table_info+0xfe ...
997	  /0x130 [x_tables] pages=4 vmalloc N0=4
998	0xffffffffa0000000-0xffffffffa000f000   61440 sys_init_module+0xc27/0x1d00 ...
999	   pages=14 vmalloc N2=14
1000	0xffffffffa000f000-0xffffffffa0014000   20480 sys_init_module+0xc27/0x1d00 ...
1001	   pages=4 vmalloc N1=4
1002	0xffffffffa0014000-0xffffffffa0017000   12288 sys_init_module+0xc27/0x1d00 ...
1003	   pages=2 vmalloc N1=2
1004	0xffffffffa0017000-0xffffffffa0022000   45056 sys_init_module+0xc27/0x1d00 ...
1005	   pages=10 vmalloc N0=10
1006	
1007	..............................................................................
1008	
1009	softirqs:
1010	
1011	Provides counts of softirq handlers serviced since boot time, for each cpu.
1012	
1013	> cat /proc/softirqs
1014	                CPU0       CPU1       CPU2       CPU3
1015	      HI:          0          0          0          0
1016	   TIMER:      27166      27120      27097      27034
1017	  NET_TX:          0          0          0         17
1018	  NET_RX:         42          0          0         39
1019	   BLOCK:          0          0        107       1121
1020	 TASKLET:          0          0          0        290
1021	   SCHED:      27035      26983      26971      26746
1022	 HRTIMER:          0          0          0          0
1023	     RCU:       1678       1769       2178       2250
1024	
1025	
1026	1.3 IDE devices in /proc/ide
1027	----------------------------
1028	
1029	The subdirectory /proc/ide contains information about all IDE devices of which
1030	the kernel  is  aware.  There is one subdirectory for each IDE controller, the
1031	file drivers  and a link for each IDE device, pointing to the device directory
1032	in the controller specific subtree.
1033	
1034	The file  drivers  contains general information about the drivers used for the
1035	IDE devices:
1036	
1037	  > cat /proc/ide/drivers
1038	  ide-cdrom version 4.53
1039	  ide-disk version 1.08
1040	
1041	More detailed  information  can  be  found  in  the  controller  specific
1042	subdirectories. These  are  named  ide0,  ide1  and  so  on.  Each  of  these
1043	directories contains the files shown in table 1-6.
1044	
1045	
1046	Table 1-6: IDE controller info in  /proc/ide/ide?
1047	..............................................................................
1048	 File    Content                                 
1049	 channel IDE channel (0 or 1)                    
1050	 config  Configuration (only for PCI/IDE bridge) 
1051	 mate    Mate name                               
1052	 model   Type/Chipset of IDE controller          
1053	..............................................................................
1054	
1055	Each device  connected  to  a  controller  has  a separate subdirectory in the
1056	controllers directory.  The  files  listed in table 1-7 are contained in these
1057	directories.
1058	
1059	
1060	Table 1-7: IDE device information
1061	..............................................................................
1062	 File             Content                                    
1063	 cache            The cache                                  
1064	 capacity         Capacity of the medium (in 512Byte blocks) 
1065	 driver           driver and version                         
1066	 geometry         physical and logical geometry              
1067	 identify         device identify block                      
1068	 media            media type                                 
1069	 model            device identifier                          
1070	 settings         device setup                               
1071	 smart_thresholds IDE disk management thresholds             
1072	 smart_values     IDE disk management values                 
1073	..............................................................................
1074	
1075	The most  interesting  file is settings. This file contains a nice overview of
1076	the drive parameters:
1077	
1078	  # cat /proc/ide/ide0/hda/settings 
1079	  name                    value           min             max             mode 
1080	  ----                    -----           ---             ---             ---- 
1081	  bios_cyl                526             0               65535           rw 
1082	  bios_head               255             0               255             rw 
1083	  bios_sect               63              0               63              rw 
1084	  breada_readahead        4               0               127             rw 
1085	  bswap                   0               0               1               r 
1086	  file_readahead          72              0               2097151         rw 
1087	  io_32bit                0               0               3               rw 
1088	  keepsettings            0               0               1               rw 
1089	  max_kb_per_request      122             1               127             rw 
1090	  multcount               0               0               8               rw 
1091	  nice1                   1               0               1               rw 
1092	  nowerr                  0               0               1               rw 
1093	  pio_mode                write-only      0               255             w 
1094	  slow                    0               0               1               rw 
1095	  unmaskirq               0               0               1               rw 
1096	  using_dma               0               0               1               rw 
1097	
1098	
1099	1.4 Networking info in /proc/net
1100	--------------------------------
1101	
1102	The subdirectory  /proc/net  follows  the  usual  pattern. Table 1-8 shows the
1103	additional values  you  get  for  IP  version 6 if you configure the kernel to
1104	support this. Table 1-9 lists the files and their meaning.
1105	
1106	
1107	Table 1-8: IPv6 info in /proc/net
1108	..............................................................................
1109	 File       Content                                               
1110	 udp6       UDP sockets (IPv6)                                    
1111	 tcp6       TCP sockets (IPv6)                                    
1112	 raw6       Raw device statistics (IPv6)                          
1113	 igmp6      IP multicast addresses, which this host joined (IPv6) 
1114	 if_inet6   List of IPv6 interface addresses                      
1115	 ipv6_route Kernel routing table for IPv6                         
1116	 rt6_stats  Global IPv6 routing tables statistics                 
1117	 sockstat6  Socket statistics (IPv6)                              
1118	 snmp6      Snmp data (IPv6)                                      
1119	..............................................................................
1120	
1121	
1122	Table 1-9: Network info in /proc/net
1123	..............................................................................
1124	 File          Content                                                         
1125	 arp           Kernel  ARP table                                               
1126	 dev           network devices with statistics                                 
1127	 dev_mcast     the Layer2 multicast groups a device is listening too
1128	               (interface index, label, number of references, number of bound
1129	               addresses). 
1130	 dev_stat      network device status                                           
1131	 ip_fwchains   Firewall chain linkage                                          
1132	 ip_fwnames    Firewall chain names                                            
1133	 ip_masq       Directory containing the masquerading tables                    
1134	 ip_masquerade Major masquerading table                                        
1135	 netstat       Network statistics                                              
1136	 raw           raw device statistics                                           
1137	 route         Kernel routing table                                            
1138	 rpc           Directory containing rpc info                                   
1139	 rt_cache      Routing cache                                                   
1140	 snmp          SNMP data                                                       
1141	 sockstat      Socket statistics                                               
1142	 tcp           TCP  sockets                                                    
1143	 udp           UDP sockets                                                     
1144	 unix          UNIX domain sockets                                             
1145	 wireless      Wireless interface data (Wavelan etc)                           
1146	 igmp          IP multicast addresses, which this host joined                  
1147	 psched        Global packet scheduler parameters.                             
1148	 netlink       List of PF_NETLINK sockets                                      
1149	 ip_mr_vifs    List of multicast virtual interfaces                            
1150	 ip_mr_cache   List of multicast routing cache                                 
1151	..............................................................................
1152	
1153	You can  use  this  information  to see which network devices are available in
1154	your system and how much traffic was routed over those devices:
1155	
1156	  > cat /proc/net/dev 
1157	  Inter-|Receive                                                   |[... 
1158	   face |bytes    packets errs drop fifo frame compressed multicast|[... 
1159	      lo:  908188   5596     0    0    0     0          0         0 [...         
1160	    ppp0:15475140  20721   410    0    0   410          0         0 [...  
1161	    eth0:  614530   7085     0    0    0     0          0         1 [... 
1162	   
1163	  ...] Transmit 
1164	  ...] bytes    packets errs drop fifo colls carrier compressed 
1165	  ...]  908188     5596    0    0    0     0       0          0 
1166	  ...] 1375103    17405    0    0    0     0       0          0 
1167	  ...] 1703981     5535    0    0    0     3       0          0 
1168	
1169	In addition, each Channel Bond interface has its own directory.  For
1170	example, the bond0 device will have a directory called /proc/net/bond0/.
1171	It will contain information that is specific to that bond, such as the
1172	current slaves of the bond, the link status of the slaves, and how
1173	many times the slaves link has failed.
1174	
1175	1.5 SCSI info
1176	-------------
1177	
1178	If you  have  a  SCSI  host adapter in your system, you'll find a subdirectory
1179	named after  the driver for this adapter in /proc/scsi. You'll also see a list
1180	of all recognized SCSI devices in /proc/scsi:
1181	
1182	  >cat /proc/scsi/scsi 
1183	  Attached devices: 
1184	  Host: scsi0 Channel: 00 Id: 00 Lun: 00 
1185	    Vendor: IBM      Model: DGHS09U          Rev: 03E0 
1186	    Type:   Direct-Access                    ANSI SCSI revision: 03 
1187	  Host: scsi0 Channel: 00 Id: 06 Lun: 00 
1188	    Vendor: PIONEER  Model: CD-ROM DR-U06S   Rev: 1.04 
1189	    Type:   CD-ROM                           ANSI SCSI revision: 02 
1190	
1191	
1192	The directory  named  after  the driver has one file for each adapter found in
1193	the system.  These  files  contain information about the controller, including
1194	the used  IRQ  and  the  IO  address range. The amount of information shown is
1195	dependent on  the adapter you use. The example shows the output for an Adaptec
1196	AHA-2940 SCSI adapter:
1197	
1198	  > cat /proc/scsi/aic7xxx/0 
1199	   
1200	  Adaptec AIC7xxx driver version: 5.1.19/3.2.4 
1201	  Compile Options: 
1202	    TCQ Enabled By Default : Disabled 
1203	    AIC7XXX_PROC_STATS     : Disabled 
1204	    AIC7XXX_RESET_DELAY    : 5 
1205	  Adapter Configuration: 
1206	             SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 
1207	                             Ultra Wide Controller 
1208	      PCI MMAPed I/O Base: 0xeb001000 
1209	   Adapter SEEPROM Config: SEEPROM found and used. 
1210	        Adaptec SCSI BIOS: Enabled 
1211	                      IRQ: 10 
1212	                     SCBs: Active 0, Max Active 2, 
1213	                           Allocated 15, HW 16, Page 255 
1214	               Interrupts: 160328 
1215	        BIOS Control Word: 0x18b6 
1216	     Adapter Control Word: 0x005b 
1217	     Extended Translation: Enabled 
1218	  Disconnect Enable Flags: 0xffff 
1219	       Ultra Enable Flags: 0x0001 
1220	   Tag Queue Enable Flags: 0x0000 
1221	  Ordered Queue Tag Flags: 0x0000 
1222	  Default Tag Queue Depth: 8 
1223	      Tagged Queue By Device array for aic7xxx host instance 0: 
1224	        {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 
1225	      Actual queue depth per device for aic7xxx host instance 0: 
1226	        {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 
1227	  Statistics: 
1228	  (scsi0:0:0:0) 
1229	    Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 
1230	    Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 
1231	    Total transfers 160151 (74577 reads and 85574 writes) 
1232	  (scsi0:0:6:0) 
1233	    Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 
1234	    Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 
1235	    Total transfers 0 (0 reads and 0 writes) 
1236	
1237	
1238	1.6 Parallel port info in /proc/parport
1239	---------------------------------------
1240	
1241	The directory  /proc/parport  contains information about the parallel ports of
1242	your system.  It  has  one  subdirectory  for  each port, named after the port
1243	number (0,1,2,...).
1244	
1245	These directories contain the four files shown in Table 1-10.
1246	
1247	
1248	Table 1-10: Files in /proc/parport
1249	..............................................................................
1250	 File      Content                                                             
1251	 autoprobe Any IEEE-1284 device ID information that has been acquired.         
1252	 devices   list of the device drivers using that port. A + will appear by the
1253	           name of the device currently using the port (it might not appear
1254	           against any). 
1255	 hardware  Parallel port's base address, IRQ line and DMA channel.             
1256	 irq       IRQ that parport is using for that port. This is in a separate
1257	           file to allow you to alter it by writing a new value in (IRQ
1258	           number or none). 
1259	..............................................................................
1260	
1261	1.7 TTY info in /proc/tty
1262	-------------------------
1263	
1264	Information about  the  available  and actually used tty's can be found in the
1265	directory /proc/tty.You'll  find  entries  for drivers and line disciplines in
1266	this directory, as shown in Table 1-11.
1267	
1268	
1269	Table 1-11: Files in /proc/tty
1270	..............................................................................
1271	 File          Content                                        
1272	 drivers       list of drivers and their usage                
1273	 ldiscs        registered line disciplines                    
1274	 driver/serial usage statistic and status of single tty lines 
1275	..............................................................................
1276	
1277	To see  which  tty's  are  currently in use, you can simply look into the file
1278	/proc/tty/drivers:
1279	
1280	  > cat /proc/tty/drivers 
1281	  pty_slave            /dev/pts      136   0-255 pty:slave 
1282	  pty_master           /dev/ptm      128   0-255 pty:master 
1283	  pty_slave            /dev/ttyp       3   0-255 pty:slave 
1284	  pty_master           /dev/pty        2   0-255 pty:master 
1285	  serial               /dev/cua        5   64-67 serial:callout 
1286	  serial               /dev/ttyS       4   64-67 serial 
1287	  /dev/tty0            /dev/tty0       4       0 system:vtmaster 
1288	  /dev/ptmx            /dev/ptmx       5       2 system 
1289	  /dev/console         /dev/console    5       1 system:console 
1290	  /dev/tty             /dev/tty        5       0 system:/dev/tty 
1291	  unknown              /dev/tty        4    1-63 console 
1292	
1293	
1294	1.8 Miscellaneous kernel statistics in /proc/stat
1295	-------------------------------------------------
1296	
1297	Various pieces   of  information about  kernel activity  are  available in the
1298	/proc/stat file.  All  of  the numbers reported  in  this file are  aggregates
1299	since the system first booted.  For a quick look, simply cat the file:
1300	
1301	  > cat /proc/stat
1302	  cpu  2255 34 2290 22625563 6290 127 456 0 0 0
1303	  cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1304	  cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1305	  intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1306	  ctxt 1990473
1307	  btime 1062191376
1308	  processes 2915
1309	  procs_running 1
1310	  procs_blocked 0
1311	  softirq 183433 0 21755 12 39 1137 231 21459 2263
1312	
1313	The very first  "cpu" line aggregates the  numbers in all  of the other "cpuN"
1314	lines.  These numbers identify the amount of time the CPU has spent performing
1315	different kinds of work.  Time units are in USER_HZ (typically hundredths of a
1316	second).  The meanings of the columns are as follows, from left to right:
1317	
1318	- user: normal processes executing in user mode
1319	- nice: niced processes executing in user mode
1320	- system: processes executing in kernel mode
1321	- idle: twiddling thumbs
1322	- iowait: waiting for I/O to complete
1323	- irq: servicing interrupts
1324	- softirq: servicing softirqs
1325	- steal: involuntary wait
1326	- guest: running a normal guest
1327	- guest_nice: running a niced guest
1328	
1329	The "intr" line gives counts of interrupts  serviced since boot time, for each
1330	of the  possible system interrupts.   The first  column  is the  total of  all
1331	interrupts serviced  including  unnumbered  architecture specific  interrupts;
1332	each  subsequent column is the  total for that particular numbered interrupt.
1333	Unnumbered interrupts are not shown, only summed into the total.
1334	
1335	The "ctxt" line gives the total number of context switches across all CPUs.
1336	
1337	The "btime" line gives  the time at which the  system booted, in seconds since
1338	the Unix epoch.
1339	
1340	The "processes" line gives the number  of processes and threads created, which
1341	includes (but  is not limited  to) those  created by  calls to the  fork() and
1342	clone() system calls.
1343	
1344	The "procs_running" line gives the total number of threads that are
1345	running or ready to run (i.e., the total number of runnable threads).
1346	
1347	The   "procs_blocked" line gives  the  number of  processes currently blocked,
1348	waiting for I/O to complete.
1349	
1350	The "softirq" line gives counts of softirqs serviced since boot time, for each
1351	of the possible system softirqs. The first column is the total of all
1352	softirqs serviced; each subsequent column is the total for that particular
1353	softirq.
1354	
1355	
1356	1.9 Ext4 file system parameters
1357	-------------------------------
1358	
1359	Information about mounted ext4 file systems can be found in
1360	/proc/fs/ext4.  Each mounted filesystem will have a directory in
1361	/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1362	/proc/fs/ext4/dm-0).   The files in each per-device directory are shown
1363	in Table 1-12, below.
1364	
1365	Table 1-12: Files in /proc/fs/ext4/<devname>
1366	..............................................................................
1367	 File            Content                                        
1368	 mb_groups       details of multiblock allocator buddy cache of free blocks
1369	..............................................................................
1370	
1371	2.0 /proc/consoles
1372	------------------
1373	Shows registered system console lines.
1374	
1375	To see which character device lines are currently used for the system console
1376	/dev/console, you may simply look into the file /proc/consoles:
1377	
1378	  > cat /proc/consoles
1379	  tty0                 -WU (ECp)       4:7
1380	  ttyS0                -W- (Ep)        4:64
1381	
1382	The columns are:
1383	
1384	  device               name of the device
1385	  operations           R = can do read operations
1386	                       W = can do write operations
1387	                       U = can do unblank
1388	  flags                E = it is enabled
1389	                       C = it is preferred console
1390	                       B = it is primary boot console
1391	                       p = it is used for printk buffer
1392	                       b = it is not a TTY but a Braille device
1393	                       a = it is safe to use when cpu is offline
1394	  major:minor          major and minor number of the device separated by a colon
1395	
1396	------------------------------------------------------------------------------
1397	Summary
1398	------------------------------------------------------------------------------
1399	The /proc file system serves information about the running system. It not only
1400	allows access to process data but also allows you to request the kernel status
1401	by reading files in the hierarchy.
1402	
1403	The directory  structure  of /proc reflects the types of information and makes
1404	it easy, if not obvious, where to look for specific data.
1405	------------------------------------------------------------------------------
1406	
1407	------------------------------------------------------------------------------
1408	CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1409	------------------------------------------------------------------------------
1410	
1411	------------------------------------------------------------------------------
1412	In This Chapter
1413	------------------------------------------------------------------------------
1414	* Modifying kernel parameters by writing into files found in /proc/sys
1415	* Exploring the files which modify certain parameters
1416	* Review of the /proc/sys file tree
1417	------------------------------------------------------------------------------
1418	
1419	
1420	A very  interesting part of /proc is the directory /proc/sys. This is not only
1421	a source  of  information,  it also allows you to change parameters within the
1422	kernel. Be  very  careful  when attempting this. You can optimize your system,
1423	but you  can  also  cause  it  to  crash.  Never  alter kernel parameters on a
1424	production system.  Set  up  a  development machine and test to make sure that
1425	everything works  the  way  you want it to. You may have no alternative but to
1426	reboot the machine once an error has been made.
1427	
1428	To change  a  value,  simply  echo  the new value into the file. An example is
1429	given below  in the section on the file system data. You need to be root to do
1430	this. You  can  create  your  own  boot script to perform this every time your
1431	system boots.
1432	
1433	The files  in /proc/sys can be used to fine tune and monitor miscellaneous and
1434	general things  in  the operation of the Linux kernel. Since some of the files
1435	can inadvertently  disrupt  your  system,  it  is  advisable  to  read  both
1436	documentation and  source  before actually making adjustments. In any case, be
1437	very careful  when  writing  to  any  of these files. The entries in /proc may
1438	change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1439	review the kernel documentation in the directory /usr/src/linux/Documentation.
1440	This chapter  is  heavily  based  on the documentation included in the pre 2.2
1441	kernels, and became part of it in version 2.2.1 of the Linux kernel.
1442	
1443	Please see: Documentation/sysctl/ directory for descriptions of these
1444	entries.
1445	
1446	------------------------------------------------------------------------------
1447	Summary
1448	------------------------------------------------------------------------------
1449	Certain aspects  of  kernel  behavior  can be modified at runtime, without the
1450	need to  recompile  the kernel, or even to reboot the system. The files in the
1451	/proc/sys tree  can  not only be read, but also modified. You can use the echo
1452	command to write value into these files, thereby changing the default settings
1453	of the kernel.
1454	------------------------------------------------------------------------------
1455	
1456	------------------------------------------------------------------------------
1457	CHAPTER 3: PER-PROCESS PARAMETERS
1458	------------------------------------------------------------------------------
1459	
1460	3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1461	--------------------------------------------------------------------------------
1462	
1463	These file can be used to adjust the badness heuristic used to select which
1464	process gets killed in out of memory conditions.
1465	
1466	The badness heuristic assigns a value to each candidate task ranging from 0
1467	(never kill) to 1000 (always kill) to determine which process is targeted.  The
1468	units are roughly a proportion along that range of allowed memory the process
1469	may allocate from based on an estimation of its current memory and swap use.
1470	For example, if a task is using all allowed memory, its badness score will be
1471	1000.  If it is using half of its allowed memory, its score will be 500.
1472	
1473	There is an additional factor included in the badness score: the current memory
1474	and swap usage is discounted by 3% for root processes.
1475	
1476	The amount of "allowed" memory depends on the context in which the oom killer
1477	was called.  If it is due to the memory assigned to the allocating task's cpuset
1478	being exhausted, the allowed memory represents the set of mems assigned to that
1479	cpuset.  If it is due to a mempolicy's node(s) being exhausted, the allowed
1480	memory represents the set of mempolicy nodes.  If it is due to a memory
1481	limit (or swap limit) being reached, the allowed memory is that configured
1482	limit.  Finally, if it is due to the entire system being out of memory, the
1483	allowed memory represents all allocatable resources.
1484	
1485	The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1486	is used to determine which task to kill.  Acceptable values range from -1000
1487	(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX).  This allows userspace to
1488	polarize the preference for oom killing either by always preferring a certain
1489	task or completely disabling it.  The lowest possible value, -1000, is
1490	equivalent to disabling oom killing entirely for that task since it will always
1491	report a badness score of 0.
1492	
1493	Consequently, it is very simple for userspace to define the amount of memory to
1494	consider for each task.  Setting a /proc/<pid>/oom_score_adj value of +500, for
1495	example, is roughly equivalent to allowing the remainder of tasks sharing the
1496	same system, cpuset, mempolicy, or memory controller resources to use at least
1497	50% more memory.  A value of -500, on the other hand, would be roughly
1498	equivalent to discounting 50% of the task's allowed memory from being considered
1499	as scoring against the task.
1500	
1501	For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1502	be used to tune the badness score.  Its acceptable values range from -16
1503	(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1504	(OOM_DISABLE) to disable oom killing entirely for that task.  Its value is
1505	scaled linearly with /proc/<pid>/oom_score_adj.
1506	
1507	The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1508	value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1509	requires CAP_SYS_RESOURCE.
1510	
1511	Caveat: when a parent task is selected, the oom killer will sacrifice any first
1512	generation children with separate address spaces instead, if possible.  This
1513	avoids servers and important system daemons from being killed and loses the
1514	minimal amount of work.
1515	
1516	
1517	3.2 /proc/<pid>/oom_score - Display current oom-killer score
1518	-------------------------------------------------------------
1519	
1520	This file can be used to check the current score used by the oom-killer is for
1521	any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1522	process should be killed in an out-of-memory situation.
1523	
1524	
1525	3.3  /proc/<pid>/io - Display the IO accounting fields
1526	-------------------------------------------------------
1527	
1528	This file contains IO statistics for each running process
1529	
1530	Example
1531	-------
1532	
1533	test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1534	[1] 3828
1535	
1536	test:/tmp # cat /proc/3828/io
1537	rchar: 323934931
1538	wchar: 323929600
1539	syscr: 632687
1540	syscw: 632675
1541	read_bytes: 0
1542	write_bytes: 323932160
1543	cancelled_write_bytes: 0
1544	
1545	
1546	Description
1547	-----------
1548	
1549	rchar
1550	-----
1551	
1552	I/O counter: chars read
1553	The number of bytes which this task has caused to be read from storage. This
1554	is simply the sum of bytes which this process passed to read() and pread().
1555	It includes things like tty IO and it is unaffected by whether or not actual
1556	physical disk IO was required (the read might have been satisfied from
1557	pagecache)
1558	
1559	
1560	wchar
1561	-----
1562	
1563	I/O counter: chars written
1564	The number of bytes which this task has caused, or shall cause to be written
1565	to disk. Similar caveats apply here as with rchar.
1566	
1567	
1568	syscr
1569	-----
1570	
1571	I/O counter: read syscalls
1572	Attempt to count the number of read I/O operations, i.e. syscalls like read()
1573	and pread().
1574	
1575	
1576	syscw
1577	-----
1578	
1579	I/O counter: write syscalls
1580	Attempt to count the number of write I/O operations, i.e. syscalls like
1581	write() and pwrite().
1582	
1583	
1584	read_bytes
1585	----------
1586	
1587	I/O counter: bytes read
1588	Attempt to count the number of bytes which this process really did cause to
1589	be fetched from the storage layer. Done at the submit_bio() level, so it is
1590	accurate for block-backed filesystems. <please add status regarding NFS and
1591	CIFS at a later time>
1592	
1593	
1594	write_bytes
1595	-----------
1596	
1597	I/O counter: bytes written
1598	Attempt to count the number of bytes which this process caused to be sent to
1599	the storage layer. This is done at page-dirtying time.
1600	
1601	
1602	cancelled_write_bytes
1603	---------------------
1604	
1605	The big inaccuracy here is truncate. If a process writes 1MB to a file and
1606	then deletes the file, it will in fact perform no writeout. But it will have
1607	been accounted as having caused 1MB of write.
1608	In other words: The number of bytes which this process caused to not happen,
1609	by truncating pagecache. A task can cause "negative" IO too. If this task
1610	truncates some dirty pagecache, some IO which another task has been accounted
1611	for (in its write_bytes) will not be happening. We _could_ just subtract that
1612	from the truncating task's write_bytes, but there is information loss in doing
1613	that.
1614	
1615	
1616	Note
1617	----
1618	
1619	At its current implementation state, this is a bit racy on 32-bit machines: if
1620	process A reads process B's /proc/pid/io while process B is updating one of
1621	those 64-bit counters, process A could see an intermediate result.
1622	
1623	
1624	More information about this can be found within the taskstats documentation in
1625	Documentation/accounting.
1626	
1627	3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1628	---------------------------------------------------------------
1629	When a process is dumped, all anonymous memory is written to a core file as
1630	long as the size of the core file isn't limited. But sometimes we don't want
1631	to dump some memory segments, for example, huge shared memory or DAX.
1632	Conversely, sometimes we want to save file-backed memory segments into a core
1633	file, not only the individual files.
1634	
1635	/proc/<pid>/coredump_filter allows you to customize which memory segments
1636	will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1637	of memory types. If a bit of the bitmask is set, memory segments of the
1638	corresponding memory type are dumped, otherwise they are not dumped.
1639	
1640	The following 9 memory types are supported:
1641	  - (bit 0) anonymous private memory
1642	  - (bit 1) anonymous shared memory
1643	  - (bit 2) file-backed private memory
1644	  - (bit 3) file-backed shared memory
1645	  - (bit 4) ELF header pages in file-backed private memory areas (it is
1646	            effective only if the bit 2 is cleared)
1647	  - (bit 5) hugetlb private memory
1648	  - (bit 6) hugetlb shared memory
1649	  - (bit 7) DAX private memory
1650	  - (bit 8) DAX shared memory
1651	
1652	  Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1653	  are always dumped regardless of the bitmask status.
1654	
1655	  Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
1656	  only affected by bit 5-6, and DAX is only affected by bits 7-8.
1657	
1658	The default value of coredump_filter is 0x33; this means all anonymous memory
1659	segments, ELF header pages and hugetlb private memory are dumped.
1660	
1661	If you don't want to dump all shared memory segments attached to pid 1234,
1662	write 0x31 to the process's proc file.
1663	
1664	  $ echo 0x31 > /proc/1234/coredump_filter
1665	
1666	When a new process is created, the process inherits the bitmask status from its
1667	parent. It is useful to set up coredump_filter before the program runs.
1668	For example:
1669	
1670	  $ echo 0x7 > /proc/self/coredump_filter
1671	  $ ./some_program
1672	
1673	3.5	/proc/<pid>/mountinfo - Information about mounts
1674	--------------------------------------------------------
1675	
1676	This file contains lines of the form:
1677	
1678	36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1679	(1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
1680	
1681	(1) mount ID:  unique identifier of the mount (may be reused after umount)
1682	(2) parent ID:  ID of parent (or of self for the top of the mount tree)
1683	(3) major:minor:  value of st_dev for files on filesystem
1684	(4) root:  root of the mount within the filesystem
1685	(5) mount point:  mount point relative to the process's root
1686	(6) mount options:  per mount options
1687	(7) optional fields:  zero or more fields of the form "tag[:value]"
1688	(8) separator:  marks the end of the optional fields
1689	(9) filesystem type:  name of filesystem of the form "type[.subtype]"
1690	(10) mount source:  filesystem specific information or "none"
1691	(11) super options:  per super block options
1692	
1693	Parsers should ignore all unrecognised optional fields.  Currently the
1694	possible optional fields are:
1695	
1696	shared:X  mount is shared in peer group X
1697	master:X  mount is slave to peer group X
1698	propagate_from:X  mount is slave and receives propagation from peer group X (*)
1699	unbindable  mount is unbindable
1700	
1701	(*) X is the closest dominant peer group under the process's root.  If
1702	X is the immediate master of the mount, or if there's no dominant peer
1703	group under the same root, then only the "master:X" field is present
1704	and not the "propagate_from:X" field.
1705	
1706	For more information on mount propagation see:
1707	
1708	  Documentation/filesystems/sharedsubtree.txt
1709	
1710	
1711	3.6	/proc/<pid>/comm  & /proc/<pid>/task/<tid>/comm
1712	--------------------------------------------------------
1713	These files provide a method to access a tasks comm value. It also allows for
1714	a task to set its own or one of its thread siblings comm value. The comm value
1715	is limited in size compared to the cmdline value, so writing anything longer
1716	then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1717	comm value.
1718	
1719	
1720	3.7	/proc/<pid>/task/<tid>/children - Information about task children
1721	-------------------------------------------------------------------------
1722	This file provides a fast way to retrieve first level children pids
1723	of a task pointed by <pid>/<tid> pair. The format is a space separated
1724	stream of pids.
1725	
1726	Note the "first level" here -- if a child has own children they will
1727	not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1728	to obtain the descendants.
1729	
1730	Since this interface is intended to be fast and cheap it doesn't
1731	guarantee to provide precise results and some children might be
1732	skipped, especially if they've exited right after we printed their
1733	pids, so one need to either stop or freeze processes being inspected
1734	if precise results are needed.
1735	
1736	
1737	3.8	/proc/<pid>/fdinfo/<fd> - Information about opened file
1738	---------------------------------------------------------------
1739	This file provides information associated with an opened file. The regular
1740	files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1741	represents the current offset of the opened file in decimal form [see lseek(2)
1742	for details], 'flags' denotes the octal O_xxx mask the file has been
1743	created with [see open(2) for details] and 'mnt_id' represents mount ID of
1744	the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1745	for details].
1746	
1747	A typical output is
1748	
1749		pos:	0
1750		flags:	0100002
1751		mnt_id:	19
1752	
1753	All locks associated with a file descriptor are shown in its fdinfo too.
1754	
1755	lock:       1: FLOCK  ADVISORY  WRITE 359 00:13:11691 0 EOF
1756	
1757	The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1758	pair provide additional information particular to the objects they represent.
1759	
1760		Eventfd files
1761		~~~~~~~~~~~~~
1762		pos:	0
1763		flags:	04002
1764		mnt_id:	9
1765		eventfd-count:	5a
1766	
1767		where 'eventfd-count' is hex value of a counter.
1768	
1769		Signalfd files
1770		~~~~~~~~~~~~~~
1771		pos:	0
1772		flags:	04002
1773		mnt_id:	9
1774		sigmask:	0000000000000200
1775	
1776		where 'sigmask' is hex value of the signal mask associated
1777		with a file.
1778	
1779		Epoll files
1780		~~~~~~~~~~~
1781		pos:	0
1782		flags:	02
1783		mnt_id:	9
1784		tfd:        5 events:       1d data: ffffffffffffffff
1785	
1786		where 'tfd' is a target file descriptor number in decimal form,
1787		'events' is events mask being watched and the 'data' is data
1788		associated with a target [see epoll(7) for more details].
1789	
1790		Fsnotify files
1791		~~~~~~~~~~~~~~
1792		For inotify files the format is the following
1793	
1794		pos:	0
1795		flags:	02000000
1796		inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1797	
1798		where 'wd' is a watch descriptor in decimal form, ie a target file
1799		descriptor number, 'ino' and 'sdev' are inode and device where the
1800		target file resides and the 'mask' is the mask of events, all in hex
1801		form [see inotify(7) for more details].
1802	
1803		If the kernel was built with exportfs support, the path to the target
1804		file is encoded as a file handle.  The file handle is provided by three
1805		fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1806		format.
1807	
1808		If the kernel is built without exportfs support the file handle won't be
1809		printed out.
1810	
1811		If there is no inotify mark attached yet the 'inotify' line will be omitted.
1812	
1813		For fanotify files the format is
1814	
1815		pos:	0
1816		flags:	02
1817		mnt_id:	9
1818		fanotify flags:10 event-flags:0
1819		fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1820		fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1821	
1822		where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1823		call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1824		flags associated with mark which are tracked separately from events
1825		mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1826		mask and 'ignored_mask' is the mask of events which are to be ignored.
1827		All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1828		does provide information about flags and mask used in fanotify_mark
1829		call [see fsnotify manpage for details].
1830	
1831		While the first three lines are mandatory and always printed, the rest is
1832		optional and may be omitted if no marks created yet.
1833	
1834		Timerfd files
1835		~~~~~~~~~~~~~
1836	
1837		pos:	0
1838		flags:	02
1839		mnt_id:	9
1840		clockid: 0
1841		ticks: 0
1842		settime flags: 01
1843		it_value: (0, 49406829)
1844		it_interval: (1, 0)
1845	
1846		where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
1847		that have occurred [see timerfd_create(2) for details]. 'settime flags' are
1848		flags in octal form been used to setup the timer [see timerfd_settime(2) for
1849		details]. 'it_value' is remaining time until the timer exiration.
1850		'it_interval' is the interval for the timer. Note the timer might be set up
1851		with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
1852		still exhibits timer's remaining time.
1853	
1854	3.9	/proc/<pid>/map_files - Information about memory mapped files
1855	---------------------------------------------------------------------
1856	This directory contains symbolic links which represent memory mapped files
1857	the process is maintaining.  Example output:
1858	
1859	     | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
1860	     | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
1861	     | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
1862	     | ...
1863	     | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
1864	     | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
1865	
1866	The name of a link represents the virtual memory bounds of a mapping, i.e.
1867	vm_area_struct::vm_start-vm_area_struct::vm_end.
1868	
1869	The main purpose of the map_files is to retrieve a set of memory mapped
1870	files in a fast way instead of parsing /proc/<pid>/maps or
1871	/proc/<pid>/smaps, both of which contain many more records.  At the same
1872	time one can open(2) mappings from the listings of two processes and
1873	comparing their inode numbers to figure out which anonymous memory areas
1874	are actually shared.
1875	
1876	3.10	/proc/<pid>/timerslack_ns - Task timerslack value
1877	---------------------------------------------------------
1878	This file provides the value of the task's timerslack value in nanoseconds.
1879	This value specifies a amount of time that normal timers may be deferred
1880	in order to coalesce timers and avoid unnecessary wakeups.
1881	
1882	This allows a task's interactivity vs power consumption trade off to be
1883	adjusted.
1884	
1885	Writing 0 to the file will set the tasks timerslack to the default value.
1886	
1887	Valid values are from 0 - ULLONG_MAX
1888	
1889	An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
1890	permissions on the task specified to change its timerslack_ns value.
1891	
1892	
1893	------------------------------------------------------------------------------
1894	Configuring procfs
1895	------------------------------------------------------------------------------
1896	
1897	4.1	Mount options
1898	---------------------
1899	
1900	The following mount options are supported:
1901	
1902		hidepid=	Set /proc/<pid>/ access mode.
1903		gid=		Set the group authorized to learn processes information.
1904	
1905	hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1906	(default).
1907	
1908	hidepid=1 means users may not access any /proc/<pid>/ directories but their
1909	own.  Sensitive files like cmdline, sched*, status are now protected against
1910	other users.  This makes it impossible to learn whether any user runs
1911	specific program (given the program doesn't reveal itself by its behaviour).
1912	As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1913	poorly written programs passing sensitive information via program arguments are
1914	now protected against local eavesdroppers.
1915	
1916	hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1917	users.  It doesn't mean that it hides a fact whether a process with a specific
1918	pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1919	but it hides process' uid and gid, which may be learned by stat()'ing
1920	/proc/<pid>/ otherwise.  It greatly complicates an intruder's task of gathering
1921	information about running processes, whether some daemon runs with elevated
1922	privileges, whether other user runs some sensitive program, whether other users
1923	run any program at all, etc.
1924	
1925	gid= defines a group authorized to learn processes information otherwise
1926	prohibited by hidepid=.  If you use some daemon like identd which needs to learn
1927	information about processes information, just add identd to this group.
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