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Based on kernel version 4.1. Page generated on 2015-06-28 12:12 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	
47	  4	Configuring procfs
48	  4.1	Mount options
49	
50	------------------------------------------------------------------------------
51	Preface
52	------------------------------------------------------------------------------
53	
54	0.1 Introduction/Credits
55	------------------------
56	
57	This documentation is  part of a soon (or  so we hope) to be  released book on
58	the SuSE  Linux distribution. As  there is  no complete documentation  for the
59	/proc file system and we've used  many freely available sources to write these
60	chapters, it  seems only fair  to give the work  back to the  Linux community.
61	This work is  based on the 2.2.*  kernel version and the  upcoming 2.4.*. I'm
62	afraid it's still far from complete, but we  hope it will be useful. As far as
63	we know, it is the first 'all-in-one' document about the /proc file system. It
64	is focused  on the Intel  x86 hardware,  so if you  are looking for  PPC, ARM,
65	SPARC, AXP, etc., features, you probably  won't find what you are looking for.
66	It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
67	additions and patches  are welcome and will  be added to this  document if you
68	mail them to Bodo.
69	
70	We'd like  to  thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
71	other people for help compiling this documentation. We'd also like to extend a
72	special thank  you to Andi Kleen for documentation, which we relied on heavily
73	to create  this  document,  as well as the additional information he provided.
74	Thanks to  everybody  else  who contributed source or docs to the Linux kernel
75	and helped create a great piece of software... :)
76	
77	If you  have  any comments, corrections or additions, please don't hesitate to
78	contact Bodo  Bauer  at  bb@ricochet.net.  We'll  be happy to add them to this
79	document.
80	
81	The   latest   version    of   this   document   is    available   online   at
82	http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
83	
84	If  the above  direction does  not works  for you,  you could  try the  kernel
85	mailing  list  at  linux-kernel@vger.kernel.org  and/or try  to  reach  me  at
86	comandante@zaralinux.com.
87	
88	0.2 Legal Stuff
89	---------------
90	
91	We don't  guarantee  the  correctness  of this document, and if you come to us
92	complaining about  how  you  screwed  up  your  system  because  of  incorrect
93	documentation, we won't feel responsible...
94	
95	------------------------------------------------------------------------------
96	CHAPTER 1: COLLECTING SYSTEM INFORMATION
97	------------------------------------------------------------------------------
98	
99	------------------------------------------------------------------------------
100	In This Chapter
101	------------------------------------------------------------------------------
102	* Investigating  the  properties  of  the  pseudo  file  system  /proc and its
103	  ability to provide information on the running Linux system
104	* Examining /proc's structure
105	* Uncovering  various  information  about the kernel and the processes running
106	  on the system
107	------------------------------------------------------------------------------
108	
109	
110	The proc  file  system acts as an interface to internal data structures in the
111	kernel. It  can  be  used to obtain information about the system and to change
112	certain kernel parameters at runtime (sysctl).
113	
114	First, we'll  take  a  look  at the read-only parts of /proc. In Chapter 2, we
115	show you how you can use /proc/sys to change settings.
116	
117	1.1 Process-Specific Subdirectories
118	-----------------------------------
119	
120	The directory  /proc  contains  (among other things) one subdirectory for each
121	process running on the system, which is named after the process ID (PID).
122	
123	The link  self  points  to  the  process reading the file system. Each process
124	subdirectory has the entries listed in Table 1-1.
125	
126	
127	Table 1-1: Process specific entries in /proc
128	..............................................................................
129	 File		Content
130	 clear_refs	Clears page referenced bits shown in smaps output
131	 cmdline	Command line arguments
132	 cpu		Current and last cpu in which it was executed	(2.4)(smp)
133	 cwd		Link to the current working directory
134	 environ	Values of environment variables
135	 exe		Link to the executable of this process
136	 fd		Directory, which contains all file descriptors
137	 maps		Memory maps to executables and library files	(2.4)
138	 mem		Memory held by this process
139	 root		Link to the root directory of this process
140	 stat		Process status
141	 statm		Process memory status information
142	 status		Process status in human readable form
143	 wchan		If CONFIG_KALLSYMS is set, a pre-decoded wchan
144	 pagemap	Page table
145	 stack		Report full stack trace, enable via CONFIG_STACKTRACE
146	 smaps		a extension based on maps, showing the memory consumption of
147			each mapping and flags associated with it
148	 numa_maps	an extension based on maps, showing the memory locality and
149			binding policy as well as mem usage (in pages) of each mapping.
150	..............................................................................
151	
152	For example, to get the status information of a process, all you have to do is
153	read the file /proc/PID/status:
154	
155	  >cat /proc/self/status
156	  Name:   cat
157	  State:  R (running)
158	  Tgid:   5452
159	  Pid:    5452
160	  PPid:   743
161	  TracerPid:      0						(2.4)
162	  Uid:    501     501     501     501
163	  Gid:    100     100     100     100
164	  FDSize: 256
165	  Groups: 100 14 16
166	  VmPeak:     5004 kB
167	  VmSize:     5004 kB
168	  VmLck:         0 kB
169	  VmHWM:       476 kB
170	  VmRSS:       476 kB
171	  VmData:      156 kB
172	  VmStk:        88 kB
173	  VmExe:        68 kB
174	  VmLib:      1412 kB
175	  VmPTE:        20 kb
176	  VmSwap:        0 kB
177	  Threads:        1
178	  SigQ:   0/28578
179	  SigPnd: 0000000000000000
180	  ShdPnd: 0000000000000000
181	  SigBlk: 0000000000000000
182	  SigIgn: 0000000000000000
183	  SigCgt: 0000000000000000
184	  CapInh: 00000000fffffeff
185	  CapPrm: 0000000000000000
186	  CapEff: 0000000000000000
187	  CapBnd: ffffffffffffffff
188	  Seccomp:        0
189	  voluntary_ctxt_switches:        0
190	  nonvoluntary_ctxt_switches:     1
191	
192	This shows you nearly the same information you would get if you viewed it with
193	the ps  command.  In  fact,  ps  uses  the  proc  file  system  to  obtain its
194	information.  But you get a more detailed  view of the  process by reading the
195	file /proc/PID/status. It fields are described in table 1-2.
196	
197	The  statm  file  contains  more  detailed  information about the process
198	memory usage. Its seven fields are explained in Table 1-3.  The stat file
199	contains details information about the process itself.  Its fields are
200	explained in Table 1-4.
201	
202	(for SMP CONFIG users)
203	For making accounting scalable, RSS related information are handled in an
204	asynchronous manner and the value may not be very precise. To see a precise
205	snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
206	It's slow but very precise.
207	
208	Table 1-2: Contents of the status files (as of 3.20.0)
209	..............................................................................
210	 Field                       Content
211	 Name                        filename of the executable
212	 State                       state (R is running, S is sleeping, D is sleeping
213	                             in an uninterruptible wait, Z is zombie,
214				     T is traced or stopped)
215	 Tgid                        thread group ID
216	 Ngid                        NUMA group ID (0 if none)
217	 Pid                         process id
218	 PPid                        process id of the parent process
219	 TracerPid                   PID of process tracing this process (0 if not)
220	 Uid                         Real, effective, saved set, and  file system UIDs
221	 Gid                         Real, effective, saved set, and  file system GIDs
222	 FDSize                      number of file descriptor slots currently allocated
223	 Groups                      supplementary group list
224	 NStgid                      descendant namespace thread group ID hierarchy
225	 NSpid                       descendant namespace process ID hierarchy
226	 NSpgid                      descendant namespace process group ID hierarchy
227	 NSsid                       descendant namespace session ID hierarchy
228	 VmPeak                      peak virtual memory size
229	 VmSize                      total program size
230	 VmLck                       locked memory size
231	 VmHWM                       peak resident set size ("high water mark")
232	 VmRSS                       size of memory portions
233	 VmData                      size of data, stack, and text segments
234	 VmStk                       size of data, stack, and text segments
235	 VmExe                       size of text segment
236	 VmLib                       size of shared library code
237	 VmPTE                       size of page table entries
238	 VmSwap                      size of swap usage (the number of referred swapents)
239	 Threads                     number of threads
240	 SigQ                        number of signals queued/max. number for queue
241	 SigPnd                      bitmap of pending signals for the thread
242	 ShdPnd                      bitmap of shared pending signals for the process
243	 SigBlk                      bitmap of blocked signals
244	 SigIgn                      bitmap of ignored signals
245	 SigCgt                      bitmap of caught signals
246	 CapInh                      bitmap of inheritable capabilities
247	 CapPrm                      bitmap of permitted capabilities
248	 CapEff                      bitmap of effective capabilities
249	 CapBnd                      bitmap of capabilities bounding set
250	 Seccomp                     seccomp mode, like prctl(PR_GET_SECCOMP, ...)
251	 Cpus_allowed                mask of CPUs on which this process may run
252	 Cpus_allowed_list           Same as previous, but in "list format"
253	 Mems_allowed                mask of memory nodes allowed to this process
254	 Mems_allowed_list           Same as previous, but in "list format"
255	 voluntary_ctxt_switches     number of voluntary context switches
256	 nonvoluntary_ctxt_switches  number of non voluntary context switches
257	..............................................................................
258	
259	Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
260	..............................................................................
261	 Field    Content
262	 size     total program size (pages)		(same as VmSize in status)
263	 resident size of memory portions (pages)	(same as VmRSS in status)
264	 shared   number of pages that are shared	(i.e. backed by a file)
265	 trs      number of pages that are 'code'	(not including libs; broken,
266								includes data segment)
267	 lrs      number of pages of library		(always 0 on 2.6)
268	 drs      number of pages of data/stack		(including libs; broken,
269								includes library text)
270	 dt       number of dirty pages			(always 0 on 2.6)
271	..............................................................................
272	
273	
274	Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
275	..............................................................................
276	 Field          Content
277	  pid           process id
278	  tcomm         filename of the executable
279	  state         state (R is running, S is sleeping, D is sleeping in an
280	                uninterruptible wait, Z is zombie, T is traced or stopped)
281	  ppid          process id of the parent process
282	  pgrp          pgrp of the process
283	  sid           session id
284	  tty_nr        tty the process uses
285	  tty_pgrp      pgrp of the tty
286	  flags         task flags
287	  min_flt       number of minor faults
288	  cmin_flt      number of minor faults with child's
289	  maj_flt       number of major faults
290	  cmaj_flt      number of major faults with child's
291	  utime         user mode jiffies
292	  stime         kernel mode jiffies
293	  cutime        user mode jiffies with child's
294	  cstime        kernel mode jiffies with child's
295	  priority      priority level
296	  nice          nice level
297	  num_threads   number of threads
298	  it_real_value	(obsolete, always 0)
299	  start_time    time the process started after system boot
300	  vsize         virtual memory size
301	  rss           resident set memory size
302	  rsslim        current limit in bytes on the rss
303	  start_code    address above which program text can run
304	  end_code      address below which program text can run
305	  start_stack   address of the start of the main process stack
306	  esp           current value of ESP
307	  eip           current value of EIP
308	  pending       bitmap of pending signals
309	  blocked       bitmap of blocked signals
310	  sigign        bitmap of ignored signals
311	  sigcatch      bitmap of caught signals
312	  wchan         address where process went to sleep
313	  0             (place holder)
314	  0             (place holder)
315	  exit_signal   signal to send to parent thread on exit
316	  task_cpu      which CPU the task is scheduled on
317	  rt_priority   realtime priority
318	  policy        scheduling policy (man sched_setscheduler)
319	  blkio_ticks   time spent waiting for block IO
320	  gtime         guest time of the task in jiffies
321	  cgtime        guest time of the task children in jiffies
322	  start_data    address above which program data+bss is placed
323	  end_data      address below which program data+bss is placed
324	  start_brk     address above which program heap can be expanded with brk()
325	  arg_start     address above which program command line is placed
326	  arg_end       address below which program command line is placed
327	  env_start     address above which program environment is placed
328	  env_end       address below which program environment is placed
329	  exit_code     the thread's exit_code in the form reported by the waitpid system call
330	..............................................................................
331	
332	The /proc/PID/maps file containing the currently mapped memory regions and
333	their access permissions.
334	
335	The format is:
336	
337	address           perms offset  dev   inode      pathname
338	
339	08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
340	08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
341	0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
342	a7cb1000-a7cb2000 ---p 00000000 00:00 0
343	a7cb2000-a7eb2000 rw-p 00000000 00:00 0
344	a7eb2000-a7eb3000 ---p 00000000 00:00 0
345	a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack:1001]
346	a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
347	a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
348	a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
349	a800b000-a800e000 rw-p 00000000 00:00 0
350	a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
351	a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
352	a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
353	a8024000-a8027000 rw-p 00000000 00:00 0
354	a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
355	a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
356	a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
357	aff35000-aff4a000 rw-p 00000000 00:00 0          [stack]
358	ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
359	
360	where "address" is the address space in the process that it occupies, "perms"
361	is a set of permissions:
362	
363	 r = read
364	 w = write
365	 x = execute
366	 s = shared
367	 p = private (copy on write)
368	
369	"offset" is the offset into the mapping, "dev" is the device (major:minor), and
370	"inode" is the inode  on that device.  0 indicates that  no inode is associated
371	with the memory region, as the case would be with BSS (uninitialized data).
372	The "pathname" shows the name associated file for this mapping.  If the mapping
373	is not associated with a file:
374	
375	 [heap]                   = the heap of the program
376	 [stack]                  = the stack of the main process
377	 [stack:1001]             = the stack of the thread with tid 1001
378	 [vdso]                   = the "virtual dynamic shared object",
379	                            the kernel system call handler
380	
381	 or if empty, the mapping is anonymous.
382	
383	The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint
384	of the individual tasks of a process. In this file you will see a mapping marked
385	as [stack] if that task sees it as a stack. This is a key difference from the
386	content of /proc/PID/maps, where you will see all mappings that are being used
387	as stack by all of those tasks. Hence, for the example above, the task-level
388	map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this:
389	
390	08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
391	08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
392	0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
393	a7cb1000-a7cb2000 ---p 00000000 00:00 0
394	a7cb2000-a7eb2000 rw-p 00000000 00:00 0
395	a7eb2000-a7eb3000 ---p 00000000 00:00 0
396	a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack]
397	a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
398	a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
399	a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
400	a800b000-a800e000 rw-p 00000000 00:00 0
401	a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
402	a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
403	a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
404	a8024000-a8027000 rw-p 00000000 00:00 0
405	a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
406	a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
407	a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
408	aff35000-aff4a000 rw-p 00000000 00:00 0
409	ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
410	
411	The /proc/PID/smaps is an extension based on maps, showing the memory
412	consumption for each of the process's mappings. For each of mappings there
413	is a series of lines such as the following:
414	
415	08048000-080bc000 r-xp 00000000 03:02 13130      /bin/bash
416	Size:               1084 kB
417	Rss:                 892 kB
418	Pss:                 374 kB
419	Shared_Clean:        892 kB
420	Shared_Dirty:          0 kB
421	Private_Clean:         0 kB
422	Private_Dirty:         0 kB
423	Referenced:          892 kB
424	Anonymous:             0 kB
425	Swap:                  0 kB
426	KernelPageSize:        4 kB
427	MMUPageSize:           4 kB
428	Locked:              374 kB
429	VmFlags: rd ex mr mw me de
430	
431	the first of these lines shows the same information as is displayed for the
432	mapping in /proc/PID/maps.  The remaining lines show the size of the mapping
433	(size), the amount of the mapping that is currently resident in RAM (RSS), the
434	process' proportional share of this mapping (PSS), the number of clean and
435	dirty private pages in the mapping.  Note that even a page which is part of a
436	MAP_SHARED mapping, but has only a single pte mapped, i.e.  is currently used
437	by only one process, is accounted as private and not as shared.  "Referenced"
438	indicates the amount of memory currently marked as referenced or accessed.
439	"Anonymous" shows the amount of memory that does not belong to any file.  Even
440	a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
441	and a page is modified, the file page is replaced by a private anonymous copy.
442	"Swap" shows how much would-be-anonymous memory is also used, but out on
443	swap.
444	
445	"VmFlags" field deserves a separate description. This member represents the kernel
446	flags associated with the particular virtual memory area in two letter encoded
447	manner. The codes are the following:
448	    rd  - readable
449	    wr  - writeable
450	    ex  - executable
451	    sh  - shared
452	    mr  - may read
453	    mw  - may write
454	    me  - may execute
455	    ms  - may share
456	    gd  - stack segment growns down
457	    pf  - pure PFN range
458	    dw  - disabled write to the mapped file
459	    lo  - pages are locked in memory
460	    io  - memory mapped I/O area
461	    sr  - sequential read advise provided
462	    rr  - random read advise provided
463	    dc  - do not copy area on fork
464	    de  - do not expand area on remapping
465	    ac  - area is accountable
466	    nr  - swap space is not reserved for the area
467	    ht  - area uses huge tlb pages
468	    nl  - non-linear mapping
469	    ar  - architecture specific flag
470	    dd  - do not include area into core dump
471	    sd  - soft-dirty flag
472	    mm  - mixed map area
473	    hg  - huge page advise flag
474	    nh  - no-huge page advise flag
475	    mg  - mergable advise flag
476	
477	Note that there is no guarantee that every flag and associated mnemonic will
478	be present in all further kernel releases. Things get changed, the flags may
479	be vanished or the reverse -- new added.
480	
481	This file is only present if the CONFIG_MMU kernel configuration option is
482	enabled.
483	
484	The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
485	bits on both physical and virtual pages associated with a process, and the
486	soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details).
487	To clear the bits for all the pages associated with the process
488	    > echo 1 > /proc/PID/clear_refs
489	
490	To clear the bits for the anonymous pages associated with the process
491	    > echo 2 > /proc/PID/clear_refs
492	
493	To clear the bits for the file mapped pages associated with the process
494	    > echo 3 > /proc/PID/clear_refs
495	
496	To clear the soft-dirty bit
497	    > echo 4 > /proc/PID/clear_refs
498	
499	To reset the peak resident set size ("high water mark") to the process's
500	current value:
501	    > echo 5 > /proc/PID/clear_refs
502	
503	Any other value written to /proc/PID/clear_refs will have no effect.
504	
505	The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
506	using /proc/kpageflags and number of times a page is mapped using
507	/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
508	
509	The /proc/pid/numa_maps is an extension based on maps, showing the memory
510	locality and binding policy, as well as the memory usage (in pages) of
511	each mapping. The output follows a general format where mapping details get
512	summarized separated by blank spaces, one mapping per each file line:
513	
514	address   policy    mapping details
515	
516	00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
517	00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
518	3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
519	320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
520	3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
521	3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
522	3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
523	320698b000 default file=/lib64/libc-2.12.so
524	3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
525	3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
526	3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
527	7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
528	7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
529	7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
530	7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
531	7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
532	
533	Where:
534	"address" is the starting address for the mapping;
535	"policy" reports the NUMA memory policy set for the mapping (see vm/numa_memory_policy.txt);
536	"mapping details" summarizes mapping data such as mapping type, page usage counters,
537	node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
538	size, in KB, that is backing the mapping up.
539	
540	1.2 Kernel data
541	---------------
542	
543	Similar to  the  process entries, the kernel data files give information about
544	the running kernel. The files used to obtain this information are contained in
545	/proc and  are  listed  in Table 1-5. Not all of these will be present in your
546	system. It  depends  on the kernel configuration and the loaded modules, which
547	files are there, and which are missing.
548	
549	Table 1-5: Kernel info in /proc
550	..............................................................................
551	 File        Content                                           
552	 apm         Advanced power management info                    
553	 buddyinfo   Kernel memory allocator information (see text)	(2.5)
554	 bus         Directory containing bus specific information     
555	 cmdline     Kernel command line                               
556	 cpuinfo     Info about the CPU                                
557	 devices     Available devices (block and character)           
558	 dma         Used DMS channels                                 
559	 filesystems Supported filesystems                             
560	 driver	     Various drivers grouped here, currently rtc (2.4)
561	 execdomains Execdomains, related to security			(2.4)
562	 fb	     Frame Buffer devices				(2.4)
563	 fs	     File system parameters, currently nfs/exports	(2.4)
564	 ide         Directory containing info about the IDE subsystem 
565	 interrupts  Interrupt usage                                   
566	 iomem	     Memory map						(2.4)
567	 ioports     I/O port usage                                    
568	 irq	     Masks for irq to cpu affinity			(2.4)(smp?)
569	 isapnp	     ISA PnP (Plug&Play) Info				(2.4)
570	 kcore       Kernel core image (can be ELF or A.OUT(deprecated in 2.4))   
571	 kmsg        Kernel messages                                   
572	 ksyms       Kernel symbol table                               
573	 loadavg     Load average of last 1, 5 & 15 minutes                
574	 locks       Kernel locks                                      
575	 meminfo     Memory info                                       
576	 misc        Miscellaneous                                     
577	 modules     List of loaded modules                            
578	 mounts      Mounted filesystems                               
579	 net         Networking info (see text)                        
580	 pagetypeinfo Additional page allocator information (see text)  (2.5)
581	 partitions  Table of partitions known to the system           
582	 pci	     Deprecated info of PCI bus (new way -> /proc/bus/pci/,
583	             decoupled by lspci					(2.4)
584	 rtc         Real time clock                                   
585	 scsi        SCSI info (see text)                              
586	 slabinfo    Slab pool info                                    
587	 softirqs    softirq usage
588	 stat        Overall statistics                                
589	 swaps       Swap space utilization                            
590	 sys         See chapter 2                                     
591	 sysvipc     Info of SysVIPC Resources (msg, sem, shm)		(2.4)
592	 tty	     Info of tty drivers
593	 uptime      Wall clock since boot, combined idle time of all cpus
594	 version     Kernel version                                    
595	 video	     bttv info of video resources			(2.4)
596	 vmallocinfo Show vmalloced areas
597	..............................................................................
598	
599	You can,  for  example,  check  which interrupts are currently in use and what
600	they are used for by looking in the file /proc/interrupts:
601	
602	  > cat /proc/interrupts 
603	             CPU0        
604	    0:    8728810          XT-PIC  timer 
605	    1:        895          XT-PIC  keyboard 
606	    2:          0          XT-PIC  cascade 
607	    3:     531695          XT-PIC  aha152x 
608	    4:    2014133          XT-PIC  serial 
609	    5:      44401          XT-PIC  pcnet_cs 
610	    8:          2          XT-PIC  rtc 
611	   11:          8          XT-PIC  i82365 
612	   12:     182918          XT-PIC  PS/2 Mouse 
613	   13:          1          XT-PIC  fpu 
614	   14:    1232265          XT-PIC  ide0 
615	   15:          7          XT-PIC  ide1 
616	  NMI:          0 
617	
618	In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
619	output of a SMP machine):
620	
621	  > cat /proc/interrupts 
622	
623	             CPU0       CPU1       
624	    0:    1243498    1214548    IO-APIC-edge  timer
625	    1:       8949       8958    IO-APIC-edge  keyboard
626	    2:          0          0          XT-PIC  cascade
627	    5:      11286      10161    IO-APIC-edge  soundblaster
628	    8:          1          0    IO-APIC-edge  rtc
629	    9:      27422      27407    IO-APIC-edge  3c503
630	   12:     113645     113873    IO-APIC-edge  PS/2 Mouse
631	   13:          0          0          XT-PIC  fpu
632	   14:      22491      24012    IO-APIC-edge  ide0
633	   15:       2183       2415    IO-APIC-edge  ide1
634	   17:      30564      30414   IO-APIC-level  eth0
635	   18:        177        164   IO-APIC-level  bttv
636	  NMI:    2457961    2457959 
637	  LOC:    2457882    2457881 
638	  ERR:       2155
639	
640	NMI is incremented in this case because every timer interrupt generates a NMI
641	(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
642	
643	LOC is the local interrupt counter of the internal APIC of every CPU.
644	
645	ERR is incremented in the case of errors in the IO-APIC bus (the bus that
646	connects the CPUs in a SMP system. This means that an error has been detected,
647	the IO-APIC automatically retry the transmission, so it should not be a big
648	problem, but you should read the SMP-FAQ.
649	
650	In 2.6.2* /proc/interrupts was expanded again.  This time the goal was for
651	/proc/interrupts to display every IRQ vector in use by the system, not
652	just those considered 'most important'.  The new vectors are:
653	
654	  THR -- interrupt raised when a machine check threshold counter
655	  (typically counting ECC corrected errors of memory or cache) exceeds
656	  a configurable threshold.  Only available on some systems.
657	
658	  TRM -- a thermal event interrupt occurs when a temperature threshold
659	  has been exceeded for the CPU.  This interrupt may also be generated
660	  when the temperature drops back to normal.
661	
662	  SPU -- a spurious interrupt is some interrupt that was raised then lowered
663	  by some IO device before it could be fully processed by the APIC.  Hence
664	  the APIC sees the interrupt but does not know what device it came from.
665	  For this case the APIC will generate the interrupt with a IRQ vector
666	  of 0xff. This might also be generated by chipset bugs.
667	
668	  RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
669	  sent from one CPU to another per the needs of the OS.  Typically,
670	  their statistics are used by kernel developers and interested users to
671	  determine the occurrence of interrupts of the given type.
672	
673	The above IRQ vectors are displayed only when relevant.  For example,
674	the threshold vector does not exist on x86_64 platforms.  Others are
675	suppressed when the system is a uniprocessor.  As of this writing, only
676	i386 and x86_64 platforms support the new IRQ vector displays.
677	
678	Of some interest is the introduction of the /proc/irq directory to 2.4.
679	It could be used to set IRQ to CPU affinity, this means that you can "hook" an
680	IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
681	irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
682	prof_cpu_mask.
683	
684	For example 
685	  > ls /proc/irq/
686	  0  10  12  14  16  18  2  4  6  8  prof_cpu_mask
687	  1  11  13  15  17  19  3  5  7  9  default_smp_affinity
688	  > ls /proc/irq/0/
689	  smp_affinity
690	
691	smp_affinity is a bitmask, in which you can specify which CPUs can handle the
692	IRQ, you can set it by doing:
693	
694	  > echo 1 > /proc/irq/10/smp_affinity
695	
696	This means that only the first CPU will handle the IRQ, but you can also echo
697	5 which means that only the first and fourth CPU can handle the IRQ.
698	
699	The contents of each smp_affinity file is the same by default:
700	
701	  > cat /proc/irq/0/smp_affinity
702	  ffffffff
703	
704	There is an alternate interface, smp_affinity_list which allows specifying
705	a cpu range instead of a bitmask:
706	
707	  > cat /proc/irq/0/smp_affinity_list
708	  1024-1031
709	
710	The default_smp_affinity mask applies to all non-active IRQs, which are the
711	IRQs which have not yet been allocated/activated, and hence which lack a
712	/proc/irq/[0-9]* directory.
713	
714	The node file on an SMP system shows the node to which the device using the IRQ
715	reports itself as being attached. This hardware locality information does not
716	include information about any possible driver locality preference.
717	
718	prof_cpu_mask specifies which CPUs are to be profiled by the system wide
719	profiler. Default value is ffffffff (all cpus if there are only 32 of them).
720	
721	The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
722	between all the CPUs which are allowed to handle it. As usual the kernel has
723	more info than you and does a better job than you, so the defaults are the
724	best choice for almost everyone.  [Note this applies only to those IO-APIC's
725	that support "Round Robin" interrupt distribution.]
726	
727	There are  three  more  important subdirectories in /proc: net, scsi, and sys.
728	The general  rule  is  that  the  contents,  or  even  the  existence of these
729	directories, depend  on your kernel configuration. If SCSI is not enabled, the
730	directory scsi  may  not  exist. The same is true with the net, which is there
731	only when networking support is present in the running kernel.
732	
733	The slabinfo  file  gives  information  about  memory usage at the slab level.
734	Linux uses  slab  pools for memory management above page level in version 2.2.
735	Commonly used  objects  have  their  own  slab  pool (such as network buffers,
736	directory cache, and so on).
737	
738	..............................................................................
739	
740	> cat /proc/buddyinfo
741	
742	Node 0, zone      DMA      0      4      5      4      4      3 ...
743	Node 0, zone   Normal      1      0      0      1    101      8 ...
744	Node 0, zone  HighMem      2      0      0      1      1      0 ...
745	
746	External fragmentation is a problem under some workloads, and buddyinfo is a
747	useful tool for helping diagnose these problems.  Buddyinfo will give you a 
748	clue as to how big an area you can safely allocate, or why a previous
749	allocation failed.
750	
751	Each column represents the number of pages of a certain order which are 
752	available.  In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 
753	ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 
754	available in ZONE_NORMAL, etc... 
755	
756	More information relevant to external fragmentation can be found in
757	pagetypeinfo.
758	
759	> cat /proc/pagetypeinfo
760	Page block order: 9
761	Pages per block:  512
762	
763	Free pages count per migrate type at order       0      1      2      3      4      5      6      7      8      9     10
764	Node    0, zone      DMA, type    Unmovable      0      0      0      1      1      1      1      1      1      1      0
765	Node    0, zone      DMA, type  Reclaimable      0      0      0      0      0      0      0      0      0      0      0
766	Node    0, zone      DMA, type      Movable      1      1      2      1      2      1      1      0      1      0      2
767	Node    0, zone      DMA, type      Reserve      0      0      0      0      0      0      0      0      0      1      0
768	Node    0, zone      DMA, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
769	Node    0, zone    DMA32, type    Unmovable    103     54     77      1      1      1     11      8      7      1      9
770	Node    0, zone    DMA32, type  Reclaimable      0      0      2      1      0      0      0      0      1      0      0
771	Node    0, zone    DMA32, type      Movable    169    152    113     91     77     54     39     13      6      1    452
772	Node    0, zone    DMA32, type      Reserve      1      2      2      2      2      0      1      1      1      1      0
773	Node    0, zone    DMA32, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
774	
775	Number of blocks type     Unmovable  Reclaimable      Movable      Reserve      Isolate
776	Node 0, zone      DMA            2            0            5            1            0
777	Node 0, zone    DMA32           41            6          967            2            0
778	
779	Fragmentation avoidance in the kernel works by grouping pages of different
780	migrate types into the same contiguous regions of memory called page blocks.
781	A page block is typically the size of the default hugepage size e.g. 2MB on
782	X86-64. By keeping pages grouped based on their ability to move, the kernel
783	can reclaim pages within a page block to satisfy a high-order allocation.
784	
785	The pagetypinfo begins with information on the size of a page block. It
786	then gives the same type of information as buddyinfo except broken down
787	by migrate-type and finishes with details on how many page blocks of each
788	type exist.
789	
790	If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
791	from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
792	make an estimate of the likely number of huge pages that can be allocated
793	at a given point in time. All the "Movable" blocks should be allocatable
794	unless memory has been mlock()'d. Some of the Reclaimable blocks should
795	also be allocatable although a lot of filesystem metadata may have to be
796	reclaimed to achieve this.
797	
798	..............................................................................
799	
800	meminfo:
801	
802	Provides information about distribution and utilization of memory.  This
803	varies by architecture and compile options.  The following is from a
804	16GB PIII, which has highmem enabled.  You may not have all of these fields.
805	
806	> cat /proc/meminfo
807	
808	The "Locked" indicates whether the mapping is locked in memory or not.
809	
810	
811	MemTotal:     16344972 kB
812	MemFree:      13634064 kB
813	MemAvailable: 14836172 kB
814	Buffers:          3656 kB
815	Cached:        1195708 kB
816	SwapCached:          0 kB
817	Active:         891636 kB
818	Inactive:      1077224 kB
819	HighTotal:    15597528 kB
820	HighFree:     13629632 kB
821	LowTotal:       747444 kB
822	LowFree:          4432 kB
823	SwapTotal:           0 kB
824	SwapFree:            0 kB
825	Dirty:             968 kB
826	Writeback:           0 kB
827	AnonPages:      861800 kB
828	Mapped:         280372 kB
829	Slab:           284364 kB
830	SReclaimable:   159856 kB
831	SUnreclaim:     124508 kB
832	PageTables:      24448 kB
833	NFS_Unstable:        0 kB
834	Bounce:              0 kB
835	WritebackTmp:        0 kB
836	CommitLimit:   7669796 kB
837	Committed_AS:   100056 kB
838	VmallocTotal:   112216 kB
839	VmallocUsed:       428 kB
840	VmallocChunk:   111088 kB
841	AnonHugePages:   49152 kB
842	
843	    MemTotal: Total usable ram (i.e. physical ram minus a few reserved
844	              bits and the kernel binary code)
845	     MemFree: The sum of LowFree+HighFree
846	MemAvailable: An estimate of how much memory is available for starting new
847	              applications, without swapping. Calculated from MemFree,
848	              SReclaimable, the size of the file LRU lists, and the low
849	              watermarks in each zone.
850	              The estimate takes into account that the system needs some
851	              page cache to function well, and that not all reclaimable
852	              slab will be reclaimable, due to items being in use. The
853	              impact of those factors will vary from system to system.
854	     Buffers: Relatively temporary storage for raw disk blocks
855	              shouldn't get tremendously large (20MB or so)
856	      Cached: in-memory cache for files read from the disk (the
857	              pagecache).  Doesn't include SwapCached
858	  SwapCached: Memory that once was swapped out, is swapped back in but
859	              still also is in the swapfile (if memory is needed it
860	              doesn't need to be swapped out AGAIN because it is already
861	              in the swapfile. This saves I/O)
862	      Active: Memory that has been used more recently and usually not
863	              reclaimed unless absolutely necessary.
864	    Inactive: Memory which has been less recently used.  It is more
865	              eligible to be reclaimed for other purposes
866	   HighTotal:
867	    HighFree: Highmem is all memory above ~860MB of physical memory
868	              Highmem areas are for use by userspace programs, or
869	              for the pagecache.  The kernel must use tricks to access
870	              this memory, making it slower to access than lowmem.
871	    LowTotal:
872	     LowFree: Lowmem is memory which can be used for everything that
873	              highmem can be used for, but it is also available for the
874	              kernel's use for its own data structures.  Among many
875	              other things, it is where everything from the Slab is
876	              allocated.  Bad things happen when you're out of lowmem.
877	   SwapTotal: total amount of swap space available
878	    SwapFree: Memory which has been evicted from RAM, and is temporarily
879	              on the disk
880	       Dirty: Memory which is waiting to get written back to the disk
881	   Writeback: Memory which is actively being written back to the disk
882	   AnonPages: Non-file backed pages mapped into userspace page tables
883	AnonHugePages: Non-file backed huge pages mapped into userspace page tables
884	      Mapped: files which have been mmaped, such as libraries
885	        Slab: in-kernel data structures cache
886	SReclaimable: Part of Slab, that might be reclaimed, such as caches
887	  SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
888	  PageTables: amount of memory dedicated to the lowest level of page
889	              tables.
890	NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
891		      storage
892	      Bounce: Memory used for block device "bounce buffers"
893	WritebackTmp: Memory used by FUSE for temporary writeback buffers
894	 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
895	              this is the total amount of  memory currently available to
896	              be allocated on the system. This limit is only adhered to
897	              if strict overcommit accounting is enabled (mode 2 in
898	              'vm.overcommit_memory').
899	              The CommitLimit is calculated with the following formula:
900	              CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
901	                             overcommit_ratio / 100 + [total swap pages]
902	              For example, on a system with 1G of physical RAM and 7G
903	              of swap with a `vm.overcommit_ratio` of 30 it would
904	              yield a CommitLimit of 7.3G.
905	              For more details, see the memory overcommit documentation
906	              in vm/overcommit-accounting.
907	Committed_AS: The amount of memory presently allocated on the system.
908	              The committed memory is a sum of all of the memory which
909	              has been allocated by processes, even if it has not been
910	              "used" by them as of yet. A process which malloc()'s 1G
911	              of memory, but only touches 300M of it will show up as
912		      using 1G. This 1G is memory which has been "committed" to
913	              by the VM and can be used at any time by the allocating
914	              application. With strict overcommit enabled on the system
915	              (mode 2 in 'vm.overcommit_memory'),allocations which would
916	              exceed the CommitLimit (detailed above) will not be permitted.
917	              This is useful if one needs to guarantee that processes will
918	              not fail due to lack of memory once that memory has been
919	              successfully allocated.
920	VmallocTotal: total size of vmalloc memory area
921	 VmallocUsed: amount of vmalloc area which is used
922	VmallocChunk: largest contiguous block of vmalloc area which is free
923	
924	..............................................................................
925	
926	vmallocinfo:
927	
928	Provides information about vmalloced/vmaped areas. One line per area,
929	containing the virtual address range of the area, size in bytes,
930	caller information of the creator, and optional information depending
931	on the kind of area :
932	
933	 pages=nr    number of pages
934	 phys=addr   if a physical address was specified
935	 ioremap     I/O mapping (ioremap() and friends)
936	 vmalloc     vmalloc() area
937	 vmap        vmap()ed pages
938	 user        VM_USERMAP area
939	 vpages      buffer for pages pointers was vmalloced (huge area)
940	 N<node>=nr  (Only on NUMA kernels)
941	             Number of pages allocated on memory node <node>
942	
943	> cat /proc/vmallocinfo
944	0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
945	  /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
946	0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
947	  /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
948	0xffffc20000302000-0xffffc20000304000    8192 acpi_tb_verify_table+0x21/0x4f...
949	  phys=7fee8000 ioremap
950	0xffffc20000304000-0xffffc20000307000   12288 acpi_tb_verify_table+0x21/0x4f...
951	  phys=7fee7000 ioremap
952	0xffffc2000031d000-0xffffc2000031f000    8192 init_vdso_vars+0x112/0x210
953	0xffffc2000031f000-0xffffc2000032b000   49152 cramfs_uncompress_init+0x2e ...
954	  /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
955	0xffffc2000033a000-0xffffc2000033d000   12288 sys_swapon+0x640/0xac0      ...
956	  pages=2 vmalloc N1=2
957	0xffffc20000347000-0xffffc2000034c000   20480 xt_alloc_table_info+0xfe ...
958	  /0x130 [x_tables] pages=4 vmalloc N0=4
959	0xffffffffa0000000-0xffffffffa000f000   61440 sys_init_module+0xc27/0x1d00 ...
960	   pages=14 vmalloc N2=14
961	0xffffffffa000f000-0xffffffffa0014000   20480 sys_init_module+0xc27/0x1d00 ...
962	   pages=4 vmalloc N1=4
963	0xffffffffa0014000-0xffffffffa0017000   12288 sys_init_module+0xc27/0x1d00 ...
964	   pages=2 vmalloc N1=2
965	0xffffffffa0017000-0xffffffffa0022000   45056 sys_init_module+0xc27/0x1d00 ...
966	   pages=10 vmalloc N0=10
967	
968	..............................................................................
969	
970	softirqs:
971	
972	Provides counts of softirq handlers serviced since boot time, for each cpu.
973	
974	> cat /proc/softirqs
975	                CPU0       CPU1       CPU2       CPU3
976	      HI:          0          0          0          0
977	   TIMER:      27166      27120      27097      27034
978	  NET_TX:          0          0          0         17
979	  NET_RX:         42          0          0         39
980	   BLOCK:          0          0        107       1121
981	 TASKLET:          0          0          0        290
982	   SCHED:      27035      26983      26971      26746
983	 HRTIMER:          0          0          0          0
984	     RCU:       1678       1769       2178       2250
985	
986	
987	1.3 IDE devices in /proc/ide
988	----------------------------
989	
990	The subdirectory /proc/ide contains information about all IDE devices of which
991	the kernel  is  aware.  There is one subdirectory for each IDE controller, the
992	file drivers  and a link for each IDE device, pointing to the device directory
993	in the controller specific subtree.
994	
995	The file  drivers  contains general information about the drivers used for the
996	IDE devices:
997	
998	  > cat /proc/ide/drivers
999	  ide-cdrom version 4.53
1000	  ide-disk version 1.08
1001	
1002	More detailed  information  can  be  found  in  the  controller  specific
1003	subdirectories. These  are  named  ide0,  ide1  and  so  on.  Each  of  these
1004	directories contains the files shown in table 1-6.
1005	
1006	
1007	Table 1-6: IDE controller info in  /proc/ide/ide?
1008	..............................................................................
1009	 File    Content                                 
1010	 channel IDE channel (0 or 1)                    
1011	 config  Configuration (only for PCI/IDE bridge) 
1012	 mate    Mate name                               
1013	 model   Type/Chipset of IDE controller          
1014	..............................................................................
1015	
1016	Each device  connected  to  a  controller  has  a separate subdirectory in the
1017	controllers directory.  The  files  listed in table 1-7 are contained in these
1018	directories.
1019	
1020	
1021	Table 1-7: IDE device information
1022	..............................................................................
1023	 File             Content                                    
1024	 cache            The cache                                  
1025	 capacity         Capacity of the medium (in 512Byte blocks) 
1026	 driver           driver and version                         
1027	 geometry         physical and logical geometry              
1028	 identify         device identify block                      
1029	 media            media type                                 
1030	 model            device identifier                          
1031	 settings         device setup                               
1032	 smart_thresholds IDE disk management thresholds             
1033	 smart_values     IDE disk management values                 
1034	..............................................................................
1035	
1036	The most  interesting  file is settings. This file contains a nice overview of
1037	the drive parameters:
1038	
1039	  # cat /proc/ide/ide0/hda/settings 
1040	  name                    value           min             max             mode 
1041	  ----                    -----           ---             ---             ---- 
1042	  bios_cyl                526             0               65535           rw 
1043	  bios_head               255             0               255             rw 
1044	  bios_sect               63              0               63              rw 
1045	  breada_readahead        4               0               127             rw 
1046	  bswap                   0               0               1               r 
1047	  file_readahead          72              0               2097151         rw 
1048	  io_32bit                0               0               3               rw 
1049	  keepsettings            0               0               1               rw 
1050	  max_kb_per_request      122             1               127             rw 
1051	  multcount               0               0               8               rw 
1052	  nice1                   1               0               1               rw 
1053	  nowerr                  0               0               1               rw 
1054	  pio_mode                write-only      0               255             w 
1055	  slow                    0               0               1               rw 
1056	  unmaskirq               0               0               1               rw 
1057	  using_dma               0               0               1               rw 
1058	
1059	
1060	1.4 Networking info in /proc/net
1061	--------------------------------
1062	
1063	The subdirectory  /proc/net  follows  the  usual  pattern. Table 1-8 shows the
1064	additional values  you  get  for  IP  version 6 if you configure the kernel to
1065	support this. Table 1-9 lists the files and their meaning.
1066	
1067	
1068	Table 1-8: IPv6 info in /proc/net
1069	..............................................................................
1070	 File       Content                                               
1071	 udp6       UDP sockets (IPv6)                                    
1072	 tcp6       TCP sockets (IPv6)                                    
1073	 raw6       Raw device statistics (IPv6)                          
1074	 igmp6      IP multicast addresses, which this host joined (IPv6) 
1075	 if_inet6   List of IPv6 interface addresses                      
1076	 ipv6_route Kernel routing table for IPv6                         
1077	 rt6_stats  Global IPv6 routing tables statistics                 
1078	 sockstat6  Socket statistics (IPv6)                              
1079	 snmp6      Snmp data (IPv6)                                      
1080	..............................................................................
1081	
1082	
1083	Table 1-9: Network info in /proc/net
1084	..............................................................................
1085	 File          Content                                                         
1086	 arp           Kernel  ARP table                                               
1087	 dev           network devices with statistics                                 
1088	 dev_mcast     the Layer2 multicast groups a device is listening too
1089	               (interface index, label, number of references, number of bound
1090	               addresses). 
1091	 dev_stat      network device status                                           
1092	 ip_fwchains   Firewall chain linkage                                          
1093	 ip_fwnames    Firewall chain names                                            
1094	 ip_masq       Directory containing the masquerading tables                    
1095	 ip_masquerade Major masquerading table                                        
1096	 netstat       Network statistics                                              
1097	 raw           raw device statistics                                           
1098	 route         Kernel routing table                                            
1099	 rpc           Directory containing rpc info                                   
1100	 rt_cache      Routing cache                                                   
1101	 snmp          SNMP data                                                       
1102	 sockstat      Socket statistics                                               
1103	 tcp           TCP  sockets                                                    
1104	 udp           UDP sockets                                                     
1105	 unix          UNIX domain sockets                                             
1106	 wireless      Wireless interface data (Wavelan etc)                           
1107	 igmp          IP multicast addresses, which this host joined                  
1108	 psched        Global packet scheduler parameters.                             
1109	 netlink       List of PF_NETLINK sockets                                      
1110	 ip_mr_vifs    List of multicast virtual interfaces                            
1111	 ip_mr_cache   List of multicast routing cache                                 
1112	..............................................................................
1113	
1114	You can  use  this  information  to see which network devices are available in
1115	your system and how much traffic was routed over those devices:
1116	
1117	  > cat /proc/net/dev 
1118	  Inter-|Receive                                                   |[... 
1119	   face |bytes    packets errs drop fifo frame compressed multicast|[... 
1120	      lo:  908188   5596     0    0    0     0          0         0 [...         
1121	    ppp0:15475140  20721   410    0    0   410          0         0 [...  
1122	    eth0:  614530   7085     0    0    0     0          0         1 [... 
1123	   
1124	  ...] Transmit 
1125	  ...] bytes    packets errs drop fifo colls carrier compressed 
1126	  ...]  908188     5596    0    0    0     0       0          0 
1127	  ...] 1375103    17405    0    0    0     0       0          0 
1128	  ...] 1703981     5535    0    0    0     3       0          0 
1129	
1130	In addition, each Channel Bond interface has its own directory.  For
1131	example, the bond0 device will have a directory called /proc/net/bond0/.
1132	It will contain information that is specific to that bond, such as the
1133	current slaves of the bond, the link status of the slaves, and how
1134	many times the slaves link has failed.
1135	
1136	1.5 SCSI info
1137	-------------
1138	
1139	If you  have  a  SCSI  host adapter in your system, you'll find a subdirectory
1140	named after  the driver for this adapter in /proc/scsi. You'll also see a list
1141	of all recognized SCSI devices in /proc/scsi:
1142	
1143	  >cat /proc/scsi/scsi 
1144	  Attached devices: 
1145	  Host: scsi0 Channel: 00 Id: 00 Lun: 00 
1146	    Vendor: IBM      Model: DGHS09U          Rev: 03E0 
1147	    Type:   Direct-Access                    ANSI SCSI revision: 03 
1148	  Host: scsi0 Channel: 00 Id: 06 Lun: 00 
1149	    Vendor: PIONEER  Model: CD-ROM DR-U06S   Rev: 1.04 
1150	    Type:   CD-ROM                           ANSI SCSI revision: 02 
1151	
1152	
1153	The directory  named  after  the driver has one file for each adapter found in
1154	the system.  These  files  contain information about the controller, including
1155	the used  IRQ  and  the  IO  address range. The amount of information shown is
1156	dependent on  the adapter you use. The example shows the output for an Adaptec
1157	AHA-2940 SCSI adapter:
1158	
1159	  > cat /proc/scsi/aic7xxx/0 
1160	   
1161	  Adaptec AIC7xxx driver version: 5.1.19/3.2.4 
1162	  Compile Options: 
1163	    TCQ Enabled By Default : Disabled 
1164	    AIC7XXX_PROC_STATS     : Disabled 
1165	    AIC7XXX_RESET_DELAY    : 5 
1166	  Adapter Configuration: 
1167	             SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 
1168	                             Ultra Wide Controller 
1169	      PCI MMAPed I/O Base: 0xeb001000 
1170	   Adapter SEEPROM Config: SEEPROM found and used. 
1171	        Adaptec SCSI BIOS: Enabled 
1172	                      IRQ: 10 
1173	                     SCBs: Active 0, Max Active 2, 
1174	                           Allocated 15, HW 16, Page 255 
1175	               Interrupts: 160328 
1176	        BIOS Control Word: 0x18b6 
1177	     Adapter Control Word: 0x005b 
1178	     Extended Translation: Enabled 
1179	  Disconnect Enable Flags: 0xffff 
1180	       Ultra Enable Flags: 0x0001 
1181	   Tag Queue Enable Flags: 0x0000 
1182	  Ordered Queue Tag Flags: 0x0000 
1183	  Default Tag Queue Depth: 8 
1184	      Tagged Queue By Device array for aic7xxx host instance 0: 
1185	        {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 
1186	      Actual queue depth per device for aic7xxx host instance 0: 
1187	        {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 
1188	  Statistics: 
1189	  (scsi0:0:0:0) 
1190	    Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 
1191	    Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 
1192	    Total transfers 160151 (74577 reads and 85574 writes) 
1193	  (scsi0:0:6:0) 
1194	    Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 
1195	    Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 
1196	    Total transfers 0 (0 reads and 0 writes) 
1197	
1198	
1199	1.6 Parallel port info in /proc/parport
1200	---------------------------------------
1201	
1202	The directory  /proc/parport  contains information about the parallel ports of
1203	your system.  It  has  one  subdirectory  for  each port, named after the port
1204	number (0,1,2,...).
1205	
1206	These directories contain the four files shown in Table 1-10.
1207	
1208	
1209	Table 1-10: Files in /proc/parport
1210	..............................................................................
1211	 File      Content                                                             
1212	 autoprobe Any IEEE-1284 device ID information that has been acquired.         
1213	 devices   list of the device drivers using that port. A + will appear by the
1214	           name of the device currently using the port (it might not appear
1215	           against any). 
1216	 hardware  Parallel port's base address, IRQ line and DMA channel.             
1217	 irq       IRQ that parport is using for that port. This is in a separate
1218	           file to allow you to alter it by writing a new value in (IRQ
1219	           number or none). 
1220	..............................................................................
1221	
1222	1.7 TTY info in /proc/tty
1223	-------------------------
1224	
1225	Information about  the  available  and actually used tty's can be found in the
1226	directory /proc/tty.You'll  find  entries  for drivers and line disciplines in
1227	this directory, as shown in Table 1-11.
1228	
1229	
1230	Table 1-11: Files in /proc/tty
1231	..............................................................................
1232	 File          Content                                        
1233	 drivers       list of drivers and their usage                
1234	 ldiscs        registered line disciplines                    
1235	 driver/serial usage statistic and status of single tty lines 
1236	..............................................................................
1237	
1238	To see  which  tty's  are  currently in use, you can simply look into the file
1239	/proc/tty/drivers:
1240	
1241	  > cat /proc/tty/drivers 
1242	  pty_slave            /dev/pts      136   0-255 pty:slave 
1243	  pty_master           /dev/ptm      128   0-255 pty:master 
1244	  pty_slave            /dev/ttyp       3   0-255 pty:slave 
1245	  pty_master           /dev/pty        2   0-255 pty:master 
1246	  serial               /dev/cua        5   64-67 serial:callout 
1247	  serial               /dev/ttyS       4   64-67 serial 
1248	  /dev/tty0            /dev/tty0       4       0 system:vtmaster 
1249	  /dev/ptmx            /dev/ptmx       5       2 system 
1250	  /dev/console         /dev/console    5       1 system:console 
1251	  /dev/tty             /dev/tty        5       0 system:/dev/tty 
1252	  unknown              /dev/tty        4    1-63 console 
1253	
1254	
1255	1.8 Miscellaneous kernel statistics in /proc/stat
1256	-------------------------------------------------
1257	
1258	Various pieces   of  information about  kernel activity  are  available in the
1259	/proc/stat file.  All  of  the numbers reported  in  this file are  aggregates
1260	since the system first booted.  For a quick look, simply cat the file:
1261	
1262	  > cat /proc/stat
1263	  cpu  2255 34 2290 22625563 6290 127 456 0 0 0
1264	  cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1265	  cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1266	  intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1267	  ctxt 1990473
1268	  btime 1062191376
1269	  processes 2915
1270	  procs_running 1
1271	  procs_blocked 0
1272	  softirq 183433 0 21755 12 39 1137 231 21459 2263
1273	
1274	The very first  "cpu" line aggregates the  numbers in all  of the other "cpuN"
1275	lines.  These numbers identify the amount of time the CPU has spent performing
1276	different kinds of work.  Time units are in USER_HZ (typically hundredths of a
1277	second).  The meanings of the columns are as follows, from left to right:
1278	
1279	- user: normal processes executing in user mode
1280	- nice: niced processes executing in user mode
1281	- system: processes executing in kernel mode
1282	- idle: twiddling thumbs
1283	- iowait: waiting for I/O to complete
1284	- irq: servicing interrupts
1285	- softirq: servicing softirqs
1286	- steal: involuntary wait
1287	- guest: running a normal guest
1288	- guest_nice: running a niced guest
1289	
1290	The "intr" line gives counts of interrupts  serviced since boot time, for each
1291	of the  possible system interrupts.   The first  column  is the  total of  all
1292	interrupts serviced  including  unnumbered  architecture specific  interrupts;
1293	each  subsequent column is the  total for that particular numbered interrupt.
1294	Unnumbered interrupts are not shown, only summed into the total.
1295	
1296	The "ctxt" line gives the total number of context switches across all CPUs.
1297	
1298	The "btime" line gives  the time at which the  system booted, in seconds since
1299	the Unix epoch.
1300	
1301	The "processes" line gives the number  of processes and threads created, which
1302	includes (but  is not limited  to) those  created by  calls to the  fork() and
1303	clone() system calls.
1304	
1305	The "procs_running" line gives the total number of threads that are
1306	running or ready to run (i.e., the total number of runnable threads).
1307	
1308	The   "procs_blocked" line gives  the  number of  processes currently blocked,
1309	waiting for I/O to complete.
1310	
1311	The "softirq" line gives counts of softirqs serviced since boot time, for each
1312	of the possible system softirqs. The first column is the total of all
1313	softirqs serviced; each subsequent column is the total for that particular
1314	softirq.
1315	
1316	
1317	1.9 Ext4 file system parameters
1318	-------------------------------
1319	
1320	Information about mounted ext4 file systems can be found in
1321	/proc/fs/ext4.  Each mounted filesystem will have a directory in
1322	/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1323	/proc/fs/ext4/dm-0).   The files in each per-device directory are shown
1324	in Table 1-12, below.
1325	
1326	Table 1-12: Files in /proc/fs/ext4/<devname>
1327	..............................................................................
1328	 File            Content                                        
1329	 mb_groups       details of multiblock allocator buddy cache of free blocks
1330	..............................................................................
1331	
1332	2.0 /proc/consoles
1333	------------------
1334	Shows registered system console lines.
1335	
1336	To see which character device lines are currently used for the system console
1337	/dev/console, you may simply look into the file /proc/consoles:
1338	
1339	  > cat /proc/consoles
1340	  tty0                 -WU (ECp)       4:7
1341	  ttyS0                -W- (Ep)        4:64
1342	
1343	The columns are:
1344	
1345	  device               name of the device
1346	  operations           R = can do read operations
1347	                       W = can do write operations
1348	                       U = can do unblank
1349	  flags                E = it is enabled
1350	                       C = it is preferred console
1351	                       B = it is primary boot console
1352	                       p = it is used for printk buffer
1353	                       b = it is not a TTY but a Braille device
1354	                       a = it is safe to use when cpu is offline
1355	  major:minor          major and minor number of the device separated by a colon
1356	
1357	------------------------------------------------------------------------------
1358	Summary
1359	------------------------------------------------------------------------------
1360	The /proc file system serves information about the running system. It not only
1361	allows access to process data but also allows you to request the kernel status
1362	by reading files in the hierarchy.
1363	
1364	The directory  structure  of /proc reflects the types of information and makes
1365	it easy, if not obvious, where to look for specific data.
1366	------------------------------------------------------------------------------
1367	
1368	------------------------------------------------------------------------------
1369	CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1370	------------------------------------------------------------------------------
1371	
1372	------------------------------------------------------------------------------
1373	In This Chapter
1374	------------------------------------------------------------------------------
1375	* Modifying kernel parameters by writing into files found in /proc/sys
1376	* Exploring the files which modify certain parameters
1377	* Review of the /proc/sys file tree
1378	------------------------------------------------------------------------------
1379	
1380	
1381	A very  interesting part of /proc is the directory /proc/sys. This is not only
1382	a source  of  information,  it also allows you to change parameters within the
1383	kernel. Be  very  careful  when attempting this. You can optimize your system,
1384	but you  can  also  cause  it  to  crash.  Never  alter kernel parameters on a
1385	production system.  Set  up  a  development machine and test to make sure that
1386	everything works  the  way  you want it to. You may have no alternative but to
1387	reboot the machine once an error has been made.
1388	
1389	To change  a  value,  simply  echo  the new value into the file. An example is
1390	given below  in the section on the file system data. You need to be root to do
1391	this. You  can  create  your  own  boot script to perform this every time your
1392	system boots.
1393	
1394	The files  in /proc/sys can be used to fine tune and monitor miscellaneous and
1395	general things  in  the operation of the Linux kernel. Since some of the files
1396	can inadvertently  disrupt  your  system,  it  is  advisable  to  read  both
1397	documentation and  source  before actually making adjustments. In any case, be
1398	very careful  when  writing  to  any  of these files. The entries in /proc may
1399	change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1400	review the kernel documentation in the directory /usr/src/linux/Documentation.
1401	This chapter  is  heavily  based  on the documentation included in the pre 2.2
1402	kernels, and became part of it in version 2.2.1 of the Linux kernel.
1403	
1404	Please see: Documentation/sysctl/ directory for descriptions of these
1405	entries.
1406	
1407	------------------------------------------------------------------------------
1408	Summary
1409	------------------------------------------------------------------------------
1410	Certain aspects  of  kernel  behavior  can be modified at runtime, without the
1411	need to  recompile  the kernel, or even to reboot the system. The files in the
1412	/proc/sys tree  can  not only be read, but also modified. You can use the echo
1413	command to write value into these files, thereby changing the default settings
1414	of the kernel.
1415	------------------------------------------------------------------------------
1416	
1417	------------------------------------------------------------------------------
1418	CHAPTER 3: PER-PROCESS PARAMETERS
1419	------------------------------------------------------------------------------
1420	
1421	3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1422	--------------------------------------------------------------------------------
1423	
1424	These file can be used to adjust the badness heuristic used to select which
1425	process gets killed in out of memory conditions.
1426	
1427	The badness heuristic assigns a value to each candidate task ranging from 0
1428	(never kill) to 1000 (always kill) to determine which process is targeted.  The
1429	units are roughly a proportion along that range of allowed memory the process
1430	may allocate from based on an estimation of its current memory and swap use.
1431	For example, if a task is using all allowed memory, its badness score will be
1432	1000.  If it is using half of its allowed memory, its score will be 500.
1433	
1434	There is an additional factor included in the badness score: the current memory
1435	and swap usage is discounted by 3% for root processes.
1436	
1437	The amount of "allowed" memory depends on the context in which the oom killer
1438	was called.  If it is due to the memory assigned to the allocating task's cpuset
1439	being exhausted, the allowed memory represents the set of mems assigned to that
1440	cpuset.  If it is due to a mempolicy's node(s) being exhausted, the allowed
1441	memory represents the set of mempolicy nodes.  If it is due to a memory
1442	limit (or swap limit) being reached, the allowed memory is that configured
1443	limit.  Finally, if it is due to the entire system being out of memory, the
1444	allowed memory represents all allocatable resources.
1445	
1446	The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1447	is used to determine which task to kill.  Acceptable values range from -1000
1448	(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX).  This allows userspace to
1449	polarize the preference for oom killing either by always preferring a certain
1450	task or completely disabling it.  The lowest possible value, -1000, is
1451	equivalent to disabling oom killing entirely for that task since it will always
1452	report a badness score of 0.
1453	
1454	Consequently, it is very simple for userspace to define the amount of memory to
1455	consider for each task.  Setting a /proc/<pid>/oom_score_adj value of +500, for
1456	example, is roughly equivalent to allowing the remainder of tasks sharing the
1457	same system, cpuset, mempolicy, or memory controller resources to use at least
1458	50% more memory.  A value of -500, on the other hand, would be roughly
1459	equivalent to discounting 50% of the task's allowed memory from being considered
1460	as scoring against the task.
1461	
1462	For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1463	be used to tune the badness score.  Its acceptable values range from -16
1464	(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1465	(OOM_DISABLE) to disable oom killing entirely for that task.  Its value is
1466	scaled linearly with /proc/<pid>/oom_score_adj.
1467	
1468	The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1469	value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1470	requires CAP_SYS_RESOURCE.
1471	
1472	Caveat: when a parent task is selected, the oom killer will sacrifice any first
1473	generation children with separate address spaces instead, if possible.  This
1474	avoids servers and important system daemons from being killed and loses the
1475	minimal amount of work.
1476	
1477	
1478	3.2 /proc/<pid>/oom_score - Display current oom-killer score
1479	-------------------------------------------------------------
1480	
1481	This file can be used to check the current score used by the oom-killer is for
1482	any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1483	process should be killed in an out-of-memory situation.
1484	
1485	
1486	3.3  /proc/<pid>/io - Display the IO accounting fields
1487	-------------------------------------------------------
1488	
1489	This file contains IO statistics for each running process
1490	
1491	Example
1492	-------
1493	
1494	test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1495	[1] 3828
1496	
1497	test:/tmp # cat /proc/3828/io
1498	rchar: 323934931
1499	wchar: 323929600
1500	syscr: 632687
1501	syscw: 632675
1502	read_bytes: 0
1503	write_bytes: 323932160
1504	cancelled_write_bytes: 0
1505	
1506	
1507	Description
1508	-----------
1509	
1510	rchar
1511	-----
1512	
1513	I/O counter: chars read
1514	The number of bytes which this task has caused to be read from storage. This
1515	is simply the sum of bytes which this process passed to read() and pread().
1516	It includes things like tty IO and it is unaffected by whether or not actual
1517	physical disk IO was required (the read might have been satisfied from
1518	pagecache)
1519	
1520	
1521	wchar
1522	-----
1523	
1524	I/O counter: chars written
1525	The number of bytes which this task has caused, or shall cause to be written
1526	to disk. Similar caveats apply here as with rchar.
1527	
1528	
1529	syscr
1530	-----
1531	
1532	I/O counter: read syscalls
1533	Attempt to count the number of read I/O operations, i.e. syscalls like read()
1534	and pread().
1535	
1536	
1537	syscw
1538	-----
1539	
1540	I/O counter: write syscalls
1541	Attempt to count the number of write I/O operations, i.e. syscalls like
1542	write() and pwrite().
1543	
1544	
1545	read_bytes
1546	----------
1547	
1548	I/O counter: bytes read
1549	Attempt to count the number of bytes which this process really did cause to
1550	be fetched from the storage layer. Done at the submit_bio() level, so it is
1551	accurate for block-backed filesystems. <please add status regarding NFS and
1552	CIFS at a later time>
1553	
1554	
1555	write_bytes
1556	-----------
1557	
1558	I/O counter: bytes written
1559	Attempt to count the number of bytes which this process caused to be sent to
1560	the storage layer. This is done at page-dirtying time.
1561	
1562	
1563	cancelled_write_bytes
1564	---------------------
1565	
1566	The big inaccuracy here is truncate. If a process writes 1MB to a file and
1567	then deletes the file, it will in fact perform no writeout. But it will have
1568	been accounted as having caused 1MB of write.
1569	In other words: The number of bytes which this process caused to not happen,
1570	by truncating pagecache. A task can cause "negative" IO too. If this task
1571	truncates some dirty pagecache, some IO which another task has been accounted
1572	for (in its write_bytes) will not be happening. We _could_ just subtract that
1573	from the truncating task's write_bytes, but there is information loss in doing
1574	that.
1575	
1576	
1577	Note
1578	----
1579	
1580	At its current implementation state, this is a bit racy on 32-bit machines: if
1581	process A reads process B's /proc/pid/io while process B is updating one of
1582	those 64-bit counters, process A could see an intermediate result.
1583	
1584	
1585	More information about this can be found within the taskstats documentation in
1586	Documentation/accounting.
1587	
1588	3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1589	---------------------------------------------------------------
1590	When a process is dumped, all anonymous memory is written to a core file as
1591	long as the size of the core file isn't limited. But sometimes we don't want
1592	to dump some memory segments, for example, huge shared memory. Conversely,
1593	sometimes we want to save file-backed memory segments into a core file, not
1594	only the individual files.
1595	
1596	/proc/<pid>/coredump_filter allows you to customize which memory segments
1597	will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1598	of memory types. If a bit of the bitmask is set, memory segments of the
1599	corresponding memory type are dumped, otherwise they are not dumped.
1600	
1601	The following 7 memory types are supported:
1602	  - (bit 0) anonymous private memory
1603	  - (bit 1) anonymous shared memory
1604	  - (bit 2) file-backed private memory
1605	  - (bit 3) file-backed shared memory
1606	  - (bit 4) ELF header pages in file-backed private memory areas (it is
1607	            effective only if the bit 2 is cleared)
1608	  - (bit 5) hugetlb private memory
1609	  - (bit 6) hugetlb shared memory
1610	
1611	  Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1612	  are always dumped regardless of the bitmask status.
1613	
1614	  Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
1615	  effected by bit 5-6.
1616	
1617	Default value of coredump_filter is 0x23; this means all anonymous memory
1618	segments and hugetlb private memory are dumped.
1619	
1620	If you don't want to dump all shared memory segments attached to pid 1234,
1621	write 0x21 to the process's proc file.
1622	
1623	  $ echo 0x21 > /proc/1234/coredump_filter
1624	
1625	When a new process is created, the process inherits the bitmask status from its
1626	parent. It is useful to set up coredump_filter before the program runs.
1627	For example:
1628	
1629	  $ echo 0x7 > /proc/self/coredump_filter
1630	  $ ./some_program
1631	
1632	3.5	/proc/<pid>/mountinfo - Information about mounts
1633	--------------------------------------------------------
1634	
1635	This file contains lines of the form:
1636	
1637	36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1638	(1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
1639	
1640	(1) mount ID:  unique identifier of the mount (may be reused after umount)
1641	(2) parent ID:  ID of parent (or of self for the top of the mount tree)
1642	(3) major:minor:  value of st_dev for files on filesystem
1643	(4) root:  root of the mount within the filesystem
1644	(5) mount point:  mount point relative to the process's root
1645	(6) mount options:  per mount options
1646	(7) optional fields:  zero or more fields of the form "tag[:value]"
1647	(8) separator:  marks the end of the optional fields
1648	(9) filesystem type:  name of filesystem of the form "type[.subtype]"
1649	(10) mount source:  filesystem specific information or "none"
1650	(11) super options:  per super block options
1651	
1652	Parsers should ignore all unrecognised optional fields.  Currently the
1653	possible optional fields are:
1654	
1655	shared:X  mount is shared in peer group X
1656	master:X  mount is slave to peer group X
1657	propagate_from:X  mount is slave and receives propagation from peer group X (*)
1658	unbindable  mount is unbindable
1659	
1660	(*) X is the closest dominant peer group under the process's root.  If
1661	X is the immediate master of the mount, or if there's no dominant peer
1662	group under the same root, then only the "master:X" field is present
1663	and not the "propagate_from:X" field.
1664	
1665	For more information on mount propagation see:
1666	
1667	  Documentation/filesystems/sharedsubtree.txt
1668	
1669	
1670	3.6	/proc/<pid>/comm  & /proc/<pid>/task/<tid>/comm
1671	--------------------------------------------------------
1672	These files provide a method to access a tasks comm value. It also allows for
1673	a task to set its own or one of its thread siblings comm value. The comm value
1674	is limited in size compared to the cmdline value, so writing anything longer
1675	then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1676	comm value.
1677	
1678	
1679	3.7	/proc/<pid>/task/<tid>/children - Information about task children
1680	-------------------------------------------------------------------------
1681	This file provides a fast way to retrieve first level children pids
1682	of a task pointed by <pid>/<tid> pair. The format is a space separated
1683	stream of pids.
1684	
1685	Note the "first level" here -- if a child has own children they will
1686	not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1687	to obtain the descendants.
1688	
1689	Since this interface is intended to be fast and cheap it doesn't
1690	guarantee to provide precise results and some children might be
1691	skipped, especially if they've exited right after we printed their
1692	pids, so one need to either stop or freeze processes being inspected
1693	if precise results are needed.
1694	
1695	
1696	3.8	/proc/<pid>/fdinfo/<fd> - Information about opened file
1697	---------------------------------------------------------------
1698	This file provides information associated with an opened file. The regular
1699	files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1700	represents the current offset of the opened file in decimal form [see lseek(2)
1701	for details], 'flags' denotes the octal O_xxx mask the file has been
1702	created with [see open(2) for details] and 'mnt_id' represents mount ID of
1703	the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1704	for details].
1705	
1706	A typical output is
1707	
1708		pos:	0
1709		flags:	0100002
1710		mnt_id:	19
1711	
1712	All locks associated with a file descriptor are shown in its fdinfo too.
1713	
1714	lock:       1: FLOCK  ADVISORY  WRITE 359 00:13:11691 0 EOF
1715	
1716	The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1717	pair provide additional information particular to the objects they represent.
1718	
1719		Eventfd files
1720		~~~~~~~~~~~~~
1721		pos:	0
1722		flags:	04002
1723		mnt_id:	9
1724		eventfd-count:	5a
1725	
1726		where 'eventfd-count' is hex value of a counter.
1727	
1728		Signalfd files
1729		~~~~~~~~~~~~~~
1730		pos:	0
1731		flags:	04002
1732		mnt_id:	9
1733		sigmask:	0000000000000200
1734	
1735		where 'sigmask' is hex value of the signal mask associated
1736		with a file.
1737	
1738		Epoll files
1739		~~~~~~~~~~~
1740		pos:	0
1741		flags:	02
1742		mnt_id:	9
1743		tfd:        5 events:       1d data: ffffffffffffffff
1744	
1745		where 'tfd' is a target file descriptor number in decimal form,
1746		'events' is events mask being watched and the 'data' is data
1747		associated with a target [see epoll(7) for more details].
1748	
1749		Fsnotify files
1750		~~~~~~~~~~~~~~
1751		For inotify files the format is the following
1752	
1753		pos:	0
1754		flags:	02000000
1755		inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1756	
1757		where 'wd' is a watch descriptor in decimal form, ie a target file
1758		descriptor number, 'ino' and 'sdev' are inode and device where the
1759		target file resides and the 'mask' is the mask of events, all in hex
1760		form [see inotify(7) for more details].
1761	
1762		If the kernel was built with exportfs support, the path to the target
1763		file is encoded as a file handle.  The file handle is provided by three
1764		fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1765		format.
1766	
1767		If the kernel is built without exportfs support the file handle won't be
1768		printed out.
1769	
1770		If there is no inotify mark attached yet the 'inotify' line will be omitted.
1771	
1772		For fanotify files the format is
1773	
1774		pos:	0
1775		flags:	02
1776		mnt_id:	9
1777		fanotify flags:10 event-flags:0
1778		fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1779		fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1780	
1781		where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1782		call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1783		flags associated with mark which are tracked separately from events
1784		mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1785		mask and 'ignored_mask' is the mask of events which are to be ignored.
1786		All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1787		does provide information about flags and mask used in fanotify_mark
1788		call [see fsnotify manpage for details].
1789	
1790		While the first three lines are mandatory and always printed, the rest is
1791		optional and may be omitted if no marks created yet.
1792	
1793		Timerfd files
1794		~~~~~~~~~~~~~
1795	
1796		pos:	0
1797		flags:	02
1798		mnt_id:	9
1799		clockid: 0
1800		ticks: 0
1801		settime flags: 01
1802		it_value: (0, 49406829)
1803		it_interval: (1, 0)
1804	
1805		where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
1806		that have occurred [see timerfd_create(2) for details]. 'settime flags' are
1807		flags in octal form been used to setup the timer [see timerfd_settime(2) for
1808		details]. 'it_value' is remaining time until the timer exiration.
1809		'it_interval' is the interval for the timer. Note the timer might be set up
1810		with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
1811		still exhibits timer's remaining time.
1812	
1813	3.9	/proc/<pid>/map_files - Information about memory mapped files
1814	---------------------------------------------------------------------
1815	This directory contains symbolic links which represent memory mapped files
1816	the process is maintaining.  Example output:
1817	
1818	     | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
1819	     | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
1820	     | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
1821	     | ...
1822	     | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
1823	     | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
1824	
1825	The name of a link represents the virtual memory bounds of a mapping, i.e.
1826	vm_area_struct::vm_start-vm_area_struct::vm_end.
1827	
1828	The main purpose of the map_files is to retrieve a set of memory mapped
1829	files in a fast way instead of parsing /proc/<pid>/maps or
1830	/proc/<pid>/smaps, both of which contain many more records.  At the same
1831	time one can open(2) mappings from the listings of two processes and
1832	comparing their inode numbers to figure out which anonymous memory areas
1833	are actually shared.
1834	
1835	------------------------------------------------------------------------------
1836	Configuring procfs
1837	------------------------------------------------------------------------------
1838	
1839	4.1	Mount options
1840	---------------------
1841	
1842	The following mount options are supported:
1843	
1844		hidepid=	Set /proc/<pid>/ access mode.
1845		gid=		Set the group authorized to learn processes information.
1846	
1847	hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1848	(default).
1849	
1850	hidepid=1 means users may not access any /proc/<pid>/ directories but their
1851	own.  Sensitive files like cmdline, sched*, status are now protected against
1852	other users.  This makes it impossible to learn whether any user runs
1853	specific program (given the program doesn't reveal itself by its behaviour).
1854	As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1855	poorly written programs passing sensitive information via program arguments are
1856	now protected against local eavesdroppers.
1857	
1858	hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1859	users.  It doesn't mean that it hides a fact whether a process with a specific
1860	pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1861	but it hides process' uid and gid, which may be learned by stat()'ing
1862	/proc/<pid>/ otherwise.  It greatly complicates an intruder's task of gathering
1863	information about running processes, whether some daemon runs with elevated
1864	privileges, whether other user runs some sensitive program, whether other users
1865	run any program at all, etc.
1866	
1867	gid= defines a group authorized to learn processes information otherwise
1868	prohibited by hidepid=.  If you use some daemon like identd which needs to learn
1869	information about processes information, just add identd to this group.
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