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Based on kernel version 4.3. Page generated on 2015-11-02 12:49 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 4.1)
209	..............................................................................
210	 Field                       Content
211	 Name                        filename of the executable
212	 State                       state (R is running, S is sleeping, D is sleeping
213	                             in an uninterruptible wait, Z is zombie,
214				     T is traced or stopped)
215	 Tgid                        thread group ID
216	 Ngid                        NUMA group ID (0 if none)
217	 Pid                         process id
218	 PPid                        process id of the parent process
219	 TracerPid                   PID of process tracing this process (0 if not)
220	 Uid                         Real, effective, saved set, and  file system UIDs
221	 Gid                         Real, effective, saved set, and  file system GIDs
222	 FDSize                      number of file descriptor slots currently allocated
223	 Groups                      supplementary group list
224	 NStgid                      descendant namespace thread group ID hierarchy
225	 NSpid                       descendant namespace process ID hierarchy
226	 NSpgid                      descendant namespace process group ID hierarchy
227	 NSsid                       descendant namespace session ID hierarchy
228	 VmPeak                      peak virtual memory size
229	 VmSize                      total program size
230	 VmLck                       locked memory size
231	 VmHWM                       peak resident set size ("high water mark")
232	 VmRSS                       size of memory portions
233	 VmData                      size of data, stack, and text segments
234	 VmStk                       size of data, stack, and text segments
235	 VmExe                       size of text segment
236	 VmLib                       size of shared library code
237	 VmPTE                       size of page table entries
238	 VmPMD                       size of second level page tables
239	 VmSwap                      size of swap usage (the number of referred swapents)
240	 Threads                     number of threads
241	 SigQ                        number of signals queued/max. number for queue
242	 SigPnd                      bitmap of pending signals for the thread
243	 ShdPnd                      bitmap of shared pending signals for the process
244	 SigBlk                      bitmap of blocked signals
245	 SigIgn                      bitmap of ignored signals
246	 SigCgt                      bitmap of caught signals
247	 CapInh                      bitmap of inheritable capabilities
248	 CapPrm                      bitmap of permitted capabilities
249	 CapEff                      bitmap of effective capabilities
250	 CapBnd                      bitmap of capabilities bounding set
251	 Seccomp                     seccomp mode, like prctl(PR_GET_SECCOMP, ...)
252	 Cpus_allowed                mask of CPUs on which this process may run
253	 Cpus_allowed_list           Same as previous, but in "list format"
254	 Mems_allowed                mask of memory nodes allowed to this process
255	 Mems_allowed_list           Same as previous, but in "list format"
256	 voluntary_ctxt_switches     number of voluntary context switches
257	 nonvoluntary_ctxt_switches  number of non voluntary context switches
258	..............................................................................
259	
260	Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
261	..............................................................................
262	 Field    Content
263	 size     total program size (pages)		(same as VmSize in status)
264	 resident size of memory portions (pages)	(same as VmRSS in status)
265	 shared   number of pages that are shared	(i.e. backed by a file)
266	 trs      number of pages that are 'code'	(not including libs; broken,
267								includes data segment)
268	 lrs      number of pages of library		(always 0 on 2.6)
269	 drs      number of pages of data/stack		(including libs; broken,
270								includes library text)
271	 dt       number of dirty pages			(always 0 on 2.6)
272	..............................................................................
273	
274	
275	Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
276	..............................................................................
277	 Field          Content
278	  pid           process id
279	  tcomm         filename of the executable
280	  state         state (R is running, S is sleeping, D is sleeping in an
281	                uninterruptible wait, Z is zombie, T is traced or stopped)
282	  ppid          process id of the parent process
283	  pgrp          pgrp of the process
284	  sid           session id
285	  tty_nr        tty the process uses
286	  tty_pgrp      pgrp of the tty
287	  flags         task flags
288	  min_flt       number of minor faults
289	  cmin_flt      number of minor faults with child's
290	  maj_flt       number of major faults
291	  cmaj_flt      number of major faults with child's
292	  utime         user mode jiffies
293	  stime         kernel mode jiffies
294	  cutime        user mode jiffies with child's
295	  cstime        kernel mode jiffies with child's
296	  priority      priority level
297	  nice          nice level
298	  num_threads   number of threads
299	  it_real_value	(obsolete, always 0)
300	  start_time    time the process started after system boot
301	  vsize         virtual memory size
302	  rss           resident set memory size
303	  rsslim        current limit in bytes on the rss
304	  start_code    address above which program text can run
305	  end_code      address below which program text can run
306	  start_stack   address of the start of the main process stack
307	  esp           current value of ESP
308	  eip           current value of EIP
309	  pending       bitmap of pending signals
310	  blocked       bitmap of blocked signals
311	  sigign        bitmap of ignored signals
312	  sigcatch      bitmap of caught signals
313	  wchan         address where process went to sleep
314	  0             (place holder)
315	  0             (place holder)
316	  exit_signal   signal to send to parent thread on exit
317	  task_cpu      which CPU the task is scheduled on
318	  rt_priority   realtime priority
319	  policy        scheduling policy (man sched_setscheduler)
320	  blkio_ticks   time spent waiting for block IO
321	  gtime         guest time of the task in jiffies
322	  cgtime        guest time of the task children in jiffies
323	  start_data    address above which program data+bss is placed
324	  end_data      address below which program data+bss is placed
325	  start_brk     address above which program heap can be expanded with brk()
326	  arg_start     address above which program command line is placed
327	  arg_end       address below which program command line is placed
328	  env_start     address above which program environment is placed
329	  env_end       address below which program environment is placed
330	  exit_code     the thread's exit_code in the form reported by the waitpid system call
331	..............................................................................
332	
333	The /proc/PID/maps file containing the currently mapped memory regions and
334	their access permissions.
335	
336	The format is:
337	
338	address           perms offset  dev   inode      pathname
339	
340	08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
341	08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
342	0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
343	a7cb1000-a7cb2000 ---p 00000000 00:00 0
344	a7cb2000-a7eb2000 rw-p 00000000 00:00 0
345	a7eb2000-a7eb3000 ---p 00000000 00:00 0
346	a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack:1001]
347	a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
348	a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
349	a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
350	a800b000-a800e000 rw-p 00000000 00:00 0
351	a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
352	a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
353	a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
354	a8024000-a8027000 rw-p 00000000 00:00 0
355	a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
356	a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
357	a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
358	aff35000-aff4a000 rw-p 00000000 00:00 0          [stack]
359	ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
360	
361	where "address" is the address space in the process that it occupies, "perms"
362	is a set of permissions:
363	
364	 r = read
365	 w = write
366	 x = execute
367	 s = shared
368	 p = private (copy on write)
369	
370	"offset" is the offset into the mapping, "dev" is the device (major:minor), and
371	"inode" is the inode  on that device.  0 indicates that  no inode is associated
372	with the memory region, as the case would be with BSS (uninitialized data).
373	The "pathname" shows the name associated file for this mapping.  If the mapping
374	is not associated with a file:
375	
376	 [heap]                   = the heap of the program
377	 [stack]                  = the stack of the main process
378	 [stack:1001]             = the stack of the thread with tid 1001
379	 [vdso]                   = the "virtual dynamic shared object",
380	                            the kernel system call handler
381	
382	 or if empty, the mapping is anonymous.
383	
384	The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint
385	of the individual tasks of a process. In this file you will see a mapping marked
386	as [stack] if that task sees it as a stack. This is a key difference from the
387	content of /proc/PID/maps, where you will see all mappings that are being used
388	as stack by all of those tasks. Hence, for the example above, the task-level
389	map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this:
390	
391	08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
392	08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
393	0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
394	a7cb1000-a7cb2000 ---p 00000000 00:00 0
395	a7cb2000-a7eb2000 rw-p 00000000 00:00 0
396	a7eb2000-a7eb3000 ---p 00000000 00:00 0
397	a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack]
398	a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
399	a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
400	a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
401	a800b000-a800e000 rw-p 00000000 00:00 0
402	a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
403	a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
404	a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
405	a8024000-a8027000 rw-p 00000000 00:00 0
406	a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
407	a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
408	a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
409	aff35000-aff4a000 rw-p 00000000 00:00 0
410	ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
411	
412	The /proc/PID/smaps is an extension based on maps, showing the memory
413	consumption for each of the process's mappings. For each of mappings there
414	is a series of lines such as the following:
415	
416	08048000-080bc000 r-xp 00000000 03:02 13130      /bin/bash
417	Size:               1084 kB
418	Rss:                 892 kB
419	Pss:                 374 kB
420	Shared_Clean:        892 kB
421	Shared_Dirty:          0 kB
422	Private_Clean:         0 kB
423	Private_Dirty:         0 kB
424	Referenced:          892 kB
425	Anonymous:             0 kB
426	Swap:                  0 kB
427	SwapPss:               0 kB
428	KernelPageSize:        4 kB
429	MMUPageSize:           4 kB
430	Locked:              374 kB
431	VmFlags: rd ex mr mw me de
432	
433	the first of these lines shows the same information as is displayed for the
434	mapping in /proc/PID/maps.  The remaining lines show the size of the mapping
435	(size), the amount of the mapping that is currently resident in RAM (RSS), the
436	process' proportional share of this mapping (PSS), the number of clean and
437	dirty private pages in the mapping.
438	
439	The "proportional set size" (PSS) of a process is the count of pages it has
440	in memory, where each page is divided by the number of processes sharing it.
441	So if a process has 1000 pages all to itself, and 1000 shared with one other
442	process, its PSS will be 1500.
443	Note that even a page which is part of a MAP_SHARED mapping, but has only
444	a single pte mapped, i.e.  is currently used by only one process, is accounted
445	as private and not as shared.
446	"Referenced" indicates the amount of memory currently marked as referenced or
447	accessed.
448	"Anonymous" shows the amount of memory that does not belong to any file.  Even
449	a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
450	and a page is modified, the file page is replaced by a private anonymous copy.
451	"Swap" shows how much would-be-anonymous memory is also used, but out on
452	swap.
453	"SwapPss" shows proportional swap share of this mapping.
454	"VmFlags" field deserves a separate description. This member represents the kernel
455	flags associated with the particular virtual memory area in two letter encoded
456	manner. The codes are the following:
457	    rd  - readable
458	    wr  - writeable
459	    ex  - executable
460	    sh  - shared
461	    mr  - may read
462	    mw  - may write
463	    me  - may execute
464	    ms  - may share
465	    gd  - stack segment growns down
466	    pf  - pure PFN range
467	    dw  - disabled write to the mapped file
468	    lo  - pages are locked in memory
469	    io  - memory mapped I/O area
470	    sr  - sequential read advise provided
471	    rr  - random read advise provided
472	    dc  - do not copy area on fork
473	    de  - do not expand area on remapping
474	    ac  - area is accountable
475	    nr  - swap space is not reserved for the area
476	    ht  - area uses huge tlb pages
477	    nl  - non-linear mapping
478	    ar  - architecture specific flag
479	    dd  - do not include area into core dump
480	    sd  - soft-dirty flag
481	    mm  - mixed map area
482	    hg  - huge page advise flag
483	    nh  - no-huge page advise flag
484	    mg  - mergable advise flag
485	
486	Note that there is no guarantee that every flag and associated mnemonic will
487	be present in all further kernel releases. Things get changed, the flags may
488	be vanished or the reverse -- new added.
489	
490	This file is only present if the CONFIG_MMU kernel configuration option is
491	enabled.
492	
493	The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
494	bits on both physical and virtual pages associated with a process, and the
495	soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details).
496	To clear the bits for all the pages associated with the process
497	    > echo 1 > /proc/PID/clear_refs
498	
499	To clear the bits for the anonymous pages associated with the process
500	    > echo 2 > /proc/PID/clear_refs
501	
502	To clear the bits for the file mapped pages associated with the process
503	    > echo 3 > /proc/PID/clear_refs
504	
505	To clear the soft-dirty bit
506	    > echo 4 > /proc/PID/clear_refs
507	
508	To reset the peak resident set size ("high water mark") to the process's
509	current value:
510	    > echo 5 > /proc/PID/clear_refs
511	
512	Any other value written to /proc/PID/clear_refs will have no effect.
513	
514	The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
515	using /proc/kpageflags and number of times a page is mapped using
516	/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
517	
518	The /proc/pid/numa_maps is an extension based on maps, showing the memory
519	locality and binding policy, as well as the memory usage (in pages) of
520	each mapping. The output follows a general format where mapping details get
521	summarized separated by blank spaces, one mapping per each file line:
522	
523	address   policy    mapping details
524	
525	00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
526	00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
527	3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
528	320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
529	3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
530	3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
531	3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
532	320698b000 default file=/lib64/libc-2.12.so
533	3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
534	3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
535	3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
536	7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
537	7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
538	7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
539	7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
540	7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
541	
542	Where:
543	"address" is the starting address for the mapping;
544	"policy" reports the NUMA memory policy set for the mapping (see vm/numa_memory_policy.txt);
545	"mapping details" summarizes mapping data such as mapping type, page usage counters,
546	node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
547	size, in KB, that is backing the mapping up.
548	
549	1.2 Kernel data
550	---------------
551	
552	Similar to  the  process entries, the kernel data files give information about
553	the running kernel. The files used to obtain this information are contained in
554	/proc and  are  listed  in Table 1-5. Not all of these will be present in your
555	system. It  depends  on the kernel configuration and the loaded modules, which
556	files are there, and which are missing.
557	
558	Table 1-5: Kernel info in /proc
559	..............................................................................
560	 File        Content                                           
561	 apm         Advanced power management info                    
562	 buddyinfo   Kernel memory allocator information (see text)	(2.5)
563	 bus         Directory containing bus specific information     
564	 cmdline     Kernel command line                               
565	 cpuinfo     Info about the CPU                                
566	 devices     Available devices (block and character)           
567	 dma         Used DMS channels                                 
568	 filesystems Supported filesystems                             
569	 driver	     Various drivers grouped here, currently rtc (2.4)
570	 execdomains Execdomains, related to security			(2.4)
571	 fb	     Frame Buffer devices				(2.4)
572	 fs	     File system parameters, currently nfs/exports	(2.4)
573	 ide         Directory containing info about the IDE subsystem 
574	 interrupts  Interrupt usage                                   
575	 iomem	     Memory map						(2.4)
576	 ioports     I/O port usage                                    
577	 irq	     Masks for irq to cpu affinity			(2.4)(smp?)
578	 isapnp	     ISA PnP (Plug&Play) Info				(2.4)
579	 kcore       Kernel core image (can be ELF or A.OUT(deprecated in 2.4))   
580	 kmsg        Kernel messages                                   
581	 ksyms       Kernel symbol table                               
582	 loadavg     Load average of last 1, 5 & 15 minutes                
583	 locks       Kernel locks                                      
584	 meminfo     Memory info                                       
585	 misc        Miscellaneous                                     
586	 modules     List of loaded modules                            
587	 mounts      Mounted filesystems                               
588	 net         Networking info (see text)                        
589	 pagetypeinfo Additional page allocator information (see text)  (2.5)
590	 partitions  Table of partitions known to the system           
591	 pci	     Deprecated info of PCI bus (new way -> /proc/bus/pci/,
592	             decoupled by lspci					(2.4)
593	 rtc         Real time clock                                   
594	 scsi        SCSI info (see text)                              
595	 slabinfo    Slab pool info                                    
596	 softirqs    softirq usage
597	 stat        Overall statistics                                
598	 swaps       Swap space utilization                            
599	 sys         See chapter 2                                     
600	 sysvipc     Info of SysVIPC Resources (msg, sem, shm)		(2.4)
601	 tty	     Info of tty drivers
602	 uptime      Wall clock since boot, combined idle time of all cpus
603	 version     Kernel version                                    
604	 video	     bttv info of video resources			(2.4)
605	 vmallocinfo Show vmalloced areas
606	..............................................................................
607	
608	You can,  for  example,  check  which interrupts are currently in use and what
609	they are used for by looking in the file /proc/interrupts:
610	
611	  > cat /proc/interrupts 
612	             CPU0        
613	    0:    8728810          XT-PIC  timer 
614	    1:        895          XT-PIC  keyboard 
615	    2:          0          XT-PIC  cascade 
616	    3:     531695          XT-PIC  aha152x 
617	    4:    2014133          XT-PIC  serial 
618	    5:      44401          XT-PIC  pcnet_cs 
619	    8:          2          XT-PIC  rtc 
620	   11:          8          XT-PIC  i82365 
621	   12:     182918          XT-PIC  PS/2 Mouse 
622	   13:          1          XT-PIC  fpu 
623	   14:    1232265          XT-PIC  ide0 
624	   15:          7          XT-PIC  ide1 
625	  NMI:          0 
626	
627	In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
628	output of a SMP machine):
629	
630	  > cat /proc/interrupts 
631	
632	             CPU0       CPU1       
633	    0:    1243498    1214548    IO-APIC-edge  timer
634	    1:       8949       8958    IO-APIC-edge  keyboard
635	    2:          0          0          XT-PIC  cascade
636	    5:      11286      10161    IO-APIC-edge  soundblaster
637	    8:          1          0    IO-APIC-edge  rtc
638	    9:      27422      27407    IO-APIC-edge  3c503
639	   12:     113645     113873    IO-APIC-edge  PS/2 Mouse
640	   13:          0          0          XT-PIC  fpu
641	   14:      22491      24012    IO-APIC-edge  ide0
642	   15:       2183       2415    IO-APIC-edge  ide1
643	   17:      30564      30414   IO-APIC-level  eth0
644	   18:        177        164   IO-APIC-level  bttv
645	  NMI:    2457961    2457959 
646	  LOC:    2457882    2457881 
647	  ERR:       2155
648	
649	NMI is incremented in this case because every timer interrupt generates a NMI
650	(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
651	
652	LOC is the local interrupt counter of the internal APIC of every CPU.
653	
654	ERR is incremented in the case of errors in the IO-APIC bus (the bus that
655	connects the CPUs in a SMP system. This means that an error has been detected,
656	the IO-APIC automatically retry the transmission, so it should not be a big
657	problem, but you should read the SMP-FAQ.
658	
659	In 2.6.2* /proc/interrupts was expanded again.  This time the goal was for
660	/proc/interrupts to display every IRQ vector in use by the system, not
661	just those considered 'most important'.  The new vectors are:
662	
663	  THR -- interrupt raised when a machine check threshold counter
664	  (typically counting ECC corrected errors of memory or cache) exceeds
665	  a configurable threshold.  Only available on some systems.
666	
667	  TRM -- a thermal event interrupt occurs when a temperature threshold
668	  has been exceeded for the CPU.  This interrupt may also be generated
669	  when the temperature drops back to normal.
670	
671	  SPU -- a spurious interrupt is some interrupt that was raised then lowered
672	  by some IO device before it could be fully processed by the APIC.  Hence
673	  the APIC sees the interrupt but does not know what device it came from.
674	  For this case the APIC will generate the interrupt with a IRQ vector
675	  of 0xff. This might also be generated by chipset bugs.
676	
677	  RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
678	  sent from one CPU to another per the needs of the OS.  Typically,
679	  their statistics are used by kernel developers and interested users to
680	  determine the occurrence of interrupts of the given type.
681	
682	The above IRQ vectors are displayed only when relevant.  For example,
683	the threshold vector does not exist on x86_64 platforms.  Others are
684	suppressed when the system is a uniprocessor.  As of this writing, only
685	i386 and x86_64 platforms support the new IRQ vector displays.
686	
687	Of some interest is the introduction of the /proc/irq directory to 2.4.
688	It could be used to set IRQ to CPU affinity, this means that you can "hook" an
689	IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
690	irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
691	prof_cpu_mask.
692	
693	For example 
694	  > ls /proc/irq/
695	  0  10  12  14  16  18  2  4  6  8  prof_cpu_mask
696	  1  11  13  15  17  19  3  5  7  9  default_smp_affinity
697	  > ls /proc/irq/0/
698	  smp_affinity
699	
700	smp_affinity is a bitmask, in which you can specify which CPUs can handle the
701	IRQ, you can set it by doing:
702	
703	  > echo 1 > /proc/irq/10/smp_affinity
704	
705	This means that only the first CPU will handle the IRQ, but you can also echo
706	5 which means that only the first and fourth CPU can handle the IRQ.
707	
708	The contents of each smp_affinity file is the same by default:
709	
710	  > cat /proc/irq/0/smp_affinity
711	  ffffffff
712	
713	There is an alternate interface, smp_affinity_list which allows specifying
714	a cpu range instead of a bitmask:
715	
716	  > cat /proc/irq/0/smp_affinity_list
717	  1024-1031
718	
719	The default_smp_affinity mask applies to all non-active IRQs, which are the
720	IRQs which have not yet been allocated/activated, and hence which lack a
721	/proc/irq/[0-9]* directory.
722	
723	The node file on an SMP system shows the node to which the device using the IRQ
724	reports itself as being attached. This hardware locality information does not
725	include information about any possible driver locality preference.
726	
727	prof_cpu_mask specifies which CPUs are to be profiled by the system wide
728	profiler. Default value is ffffffff (all cpus if there are only 32 of them).
729	
730	The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
731	between all the CPUs which are allowed to handle it. As usual the kernel has
732	more info than you and does a better job than you, so the defaults are the
733	best choice for almost everyone.  [Note this applies only to those IO-APIC's
734	that support "Round Robin" interrupt distribution.]
735	
736	There are  three  more  important subdirectories in /proc: net, scsi, and sys.
737	The general  rule  is  that  the  contents,  or  even  the  existence of these
738	directories, depend  on your kernel configuration. If SCSI is not enabled, the
739	directory scsi  may  not  exist. The same is true with the net, which is there
740	only when networking support is present in the running kernel.
741	
742	The slabinfo  file  gives  information  about  memory usage at the slab level.
743	Linux uses  slab  pools for memory management above page level in version 2.2.
744	Commonly used  objects  have  their  own  slab  pool (such as network buffers,
745	directory cache, and so on).
746	
747	..............................................................................
748	
749	> cat /proc/buddyinfo
750	
751	Node 0, zone      DMA      0      4      5      4      4      3 ...
752	Node 0, zone   Normal      1      0      0      1    101      8 ...
753	Node 0, zone  HighMem      2      0      0      1      1      0 ...
754	
755	External fragmentation is a problem under some workloads, and buddyinfo is a
756	useful tool for helping diagnose these problems.  Buddyinfo will give you a 
757	clue as to how big an area you can safely allocate, or why a previous
758	allocation failed.
759	
760	Each column represents the number of pages of a certain order which are 
761	available.  In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 
762	ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 
763	available in ZONE_NORMAL, etc... 
764	
765	More information relevant to external fragmentation can be found in
766	pagetypeinfo.
767	
768	> cat /proc/pagetypeinfo
769	Page block order: 9
770	Pages per block:  512
771	
772	Free pages count per migrate type at order       0      1      2      3      4      5      6      7      8      9     10
773	Node    0, zone      DMA, type    Unmovable      0      0      0      1      1      1      1      1      1      1      0
774	Node    0, zone      DMA, type  Reclaimable      0      0      0      0      0      0      0      0      0      0      0
775	Node    0, zone      DMA, type      Movable      1      1      2      1      2      1      1      0      1      0      2
776	Node    0, zone      DMA, type      Reserve      0      0      0      0      0      0      0      0      0      1      0
777	Node    0, zone      DMA, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
778	Node    0, zone    DMA32, type    Unmovable    103     54     77      1      1      1     11      8      7      1      9
779	Node    0, zone    DMA32, type  Reclaimable      0      0      2      1      0      0      0      0      1      0      0
780	Node    0, zone    DMA32, type      Movable    169    152    113     91     77     54     39     13      6      1    452
781	Node    0, zone    DMA32, type      Reserve      1      2      2      2      2      0      1      1      1      1      0
782	Node    0, zone    DMA32, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
783	
784	Number of blocks type     Unmovable  Reclaimable      Movable      Reserve      Isolate
785	Node 0, zone      DMA            2            0            5            1            0
786	Node 0, zone    DMA32           41            6          967            2            0
787	
788	Fragmentation avoidance in the kernel works by grouping pages of different
789	migrate types into the same contiguous regions of memory called page blocks.
790	A page block is typically the size of the default hugepage size e.g. 2MB on
791	X86-64. By keeping pages grouped based on their ability to move, the kernel
792	can reclaim pages within a page block to satisfy a high-order allocation.
793	
794	The pagetypinfo begins with information on the size of a page block. It
795	then gives the same type of information as buddyinfo except broken down
796	by migrate-type and finishes with details on how many page blocks of each
797	type exist.
798	
799	If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
800	from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
801	make an estimate of the likely number of huge pages that can be allocated
802	at a given point in time. All the "Movable" blocks should be allocatable
803	unless memory has been mlock()'d. Some of the Reclaimable blocks should
804	also be allocatable although a lot of filesystem metadata may have to be
805	reclaimed to achieve this.
806	
807	..............................................................................
808	
809	meminfo:
810	
811	Provides information about distribution and utilization of memory.  This
812	varies by architecture and compile options.  The following is from a
813	16GB PIII, which has highmem enabled.  You may not have all of these fields.
814	
815	> cat /proc/meminfo
816	
817	The "Locked" indicates whether the mapping is locked in memory or not.
818	
819	
820	MemTotal:     16344972 kB
821	MemFree:      13634064 kB
822	MemAvailable: 14836172 kB
823	Buffers:          3656 kB
824	Cached:        1195708 kB
825	SwapCached:          0 kB
826	Active:         891636 kB
827	Inactive:      1077224 kB
828	HighTotal:    15597528 kB
829	HighFree:     13629632 kB
830	LowTotal:       747444 kB
831	LowFree:          4432 kB
832	SwapTotal:           0 kB
833	SwapFree:            0 kB
834	Dirty:             968 kB
835	Writeback:           0 kB
836	AnonPages:      861800 kB
837	Mapped:         280372 kB
838	Slab:           284364 kB
839	SReclaimable:   159856 kB
840	SUnreclaim:     124508 kB
841	PageTables:      24448 kB
842	NFS_Unstable:        0 kB
843	Bounce:              0 kB
844	WritebackTmp:        0 kB
845	CommitLimit:   7669796 kB
846	Committed_AS:   100056 kB
847	VmallocTotal:   112216 kB
848	VmallocUsed:       428 kB
849	VmallocChunk:   111088 kB
850	AnonHugePages:   49152 kB
851	
852	    MemTotal: Total usable ram (i.e. physical ram minus a few reserved
853	              bits and the kernel binary code)
854	     MemFree: The sum of LowFree+HighFree
855	MemAvailable: An estimate of how much memory is available for starting new
856	              applications, without swapping. Calculated from MemFree,
857	              SReclaimable, the size of the file LRU lists, and the low
858	              watermarks in each zone.
859	              The estimate takes into account that the system needs some
860	              page cache to function well, and that not all reclaimable
861	              slab will be reclaimable, due to items being in use. The
862	              impact of those factors will vary from system to system.
863	     Buffers: Relatively temporary storage for raw disk blocks
864	              shouldn't get tremendously large (20MB or so)
865	      Cached: in-memory cache for files read from the disk (the
866	              pagecache).  Doesn't include SwapCached
867	  SwapCached: Memory that once was swapped out, is swapped back in but
868	              still also is in the swapfile (if memory is needed it
869	              doesn't need to be swapped out AGAIN because it is already
870	              in the swapfile. This saves I/O)
871	      Active: Memory that has been used more recently and usually not
872	              reclaimed unless absolutely necessary.
873	    Inactive: Memory which has been less recently used.  It is more
874	              eligible to be reclaimed for other purposes
875	   HighTotal:
876	    HighFree: Highmem is all memory above ~860MB of physical memory
877	              Highmem areas are for use by userspace programs, or
878	              for the pagecache.  The kernel must use tricks to access
879	              this memory, making it slower to access than lowmem.
880	    LowTotal:
881	     LowFree: Lowmem is memory which can be used for everything that
882	              highmem can be used for, but it is also available for the
883	              kernel's use for its own data structures.  Among many
884	              other things, it is where everything from the Slab is
885	              allocated.  Bad things happen when you're out of lowmem.
886	   SwapTotal: total amount of swap space available
887	    SwapFree: Memory which has been evicted from RAM, and is temporarily
888	              on the disk
889	       Dirty: Memory which is waiting to get written back to the disk
890	   Writeback: Memory which is actively being written back to the disk
891	   AnonPages: Non-file backed pages mapped into userspace page tables
892	AnonHugePages: Non-file backed huge pages mapped into userspace page tables
893	      Mapped: files which have been mmaped, such as libraries
894	        Slab: in-kernel data structures cache
895	SReclaimable: Part of Slab, that might be reclaimed, such as caches
896	  SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
897	  PageTables: amount of memory dedicated to the lowest level of page
898	              tables.
899	NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
900		      storage
901	      Bounce: Memory used for block device "bounce buffers"
902	WritebackTmp: Memory used by FUSE for temporary writeback buffers
903	 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
904	              this is the total amount of  memory currently available to
905	              be allocated on the system. This limit is only adhered to
906	              if strict overcommit accounting is enabled (mode 2 in
907	              'vm.overcommit_memory').
908	              The CommitLimit is calculated with the following formula:
909	              CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
910	                             overcommit_ratio / 100 + [total swap pages]
911	              For example, on a system with 1G of physical RAM and 7G
912	              of swap with a `vm.overcommit_ratio` of 30 it would
913	              yield a CommitLimit of 7.3G.
914	              For more details, see the memory overcommit documentation
915	              in vm/overcommit-accounting.
916	Committed_AS: The amount of memory presently allocated on the system.
917	              The committed memory is a sum of all of the memory which
918	              has been allocated by processes, even if it has not been
919	              "used" by them as of yet. A process which malloc()'s 1G
920	              of memory, but only touches 300M of it will show up as
921		      using 1G. This 1G is memory which has been "committed" to
922	              by the VM and can be used at any time by the allocating
923	              application. With strict overcommit enabled on the system
924	              (mode 2 in 'vm.overcommit_memory'),allocations which would
925	              exceed the CommitLimit (detailed above) will not be permitted.
926	              This is useful if one needs to guarantee that processes will
927	              not fail due to lack of memory once that memory has been
928	              successfully allocated.
929	VmallocTotal: total size of vmalloc memory area
930	 VmallocUsed: amount of vmalloc area which is used
931	VmallocChunk: largest contiguous block of vmalloc area which is free
932	
933	..............................................................................
934	
935	vmallocinfo:
936	
937	Provides information about vmalloced/vmaped areas. One line per area,
938	containing the virtual address range of the area, size in bytes,
939	caller information of the creator, and optional information depending
940	on the kind of area :
941	
942	 pages=nr    number of pages
943	 phys=addr   if a physical address was specified
944	 ioremap     I/O mapping (ioremap() and friends)
945	 vmalloc     vmalloc() area
946	 vmap        vmap()ed pages
947	 user        VM_USERMAP area
948	 vpages      buffer for pages pointers was vmalloced (huge area)
949	 N<node>=nr  (Only on NUMA kernels)
950	             Number of pages allocated on memory node <node>
951	
952	> cat /proc/vmallocinfo
953	0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
954	  /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
955	0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
956	  /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
957	0xffffc20000302000-0xffffc20000304000    8192 acpi_tb_verify_table+0x21/0x4f...
958	  phys=7fee8000 ioremap
959	0xffffc20000304000-0xffffc20000307000   12288 acpi_tb_verify_table+0x21/0x4f...
960	  phys=7fee7000 ioremap
961	0xffffc2000031d000-0xffffc2000031f000    8192 init_vdso_vars+0x112/0x210
962	0xffffc2000031f000-0xffffc2000032b000   49152 cramfs_uncompress_init+0x2e ...
963	  /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
964	0xffffc2000033a000-0xffffc2000033d000   12288 sys_swapon+0x640/0xac0      ...
965	  pages=2 vmalloc N1=2
966	0xffffc20000347000-0xffffc2000034c000   20480 xt_alloc_table_info+0xfe ...
967	  /0x130 [x_tables] pages=4 vmalloc N0=4
968	0xffffffffa0000000-0xffffffffa000f000   61440 sys_init_module+0xc27/0x1d00 ...
969	   pages=14 vmalloc N2=14
970	0xffffffffa000f000-0xffffffffa0014000   20480 sys_init_module+0xc27/0x1d00 ...
971	   pages=4 vmalloc N1=4
972	0xffffffffa0014000-0xffffffffa0017000   12288 sys_init_module+0xc27/0x1d00 ...
973	   pages=2 vmalloc N1=2
974	0xffffffffa0017000-0xffffffffa0022000   45056 sys_init_module+0xc27/0x1d00 ...
975	   pages=10 vmalloc N0=10
976	
977	..............................................................................
978	
979	softirqs:
980	
981	Provides counts of softirq handlers serviced since boot time, for each cpu.
982	
983	> cat /proc/softirqs
984	                CPU0       CPU1       CPU2       CPU3
985	      HI:          0          0          0          0
986	   TIMER:      27166      27120      27097      27034
987	  NET_TX:          0          0          0         17
988	  NET_RX:         42          0          0         39
989	   BLOCK:          0          0        107       1121
990	 TASKLET:          0          0          0        290
991	   SCHED:      27035      26983      26971      26746
992	 HRTIMER:          0          0          0          0
993	     RCU:       1678       1769       2178       2250
994	
995	
996	1.3 IDE devices in /proc/ide
997	----------------------------
998	
999	The subdirectory /proc/ide contains information about all IDE devices of which
1000	the kernel  is  aware.  There is one subdirectory for each IDE controller, the
1001	file drivers  and a link for each IDE device, pointing to the device directory
1002	in the controller specific subtree.
1003	
1004	The file  drivers  contains general information about the drivers used for the
1005	IDE devices:
1006	
1007	  > cat /proc/ide/drivers
1008	  ide-cdrom version 4.53
1009	  ide-disk version 1.08
1010	
1011	More detailed  information  can  be  found  in  the  controller  specific
1012	subdirectories. These  are  named  ide0,  ide1  and  so  on.  Each  of  these
1013	directories contains the files shown in table 1-6.
1014	
1015	
1016	Table 1-6: IDE controller info in  /proc/ide/ide?
1017	..............................................................................
1018	 File    Content                                 
1019	 channel IDE channel (0 or 1)                    
1020	 config  Configuration (only for PCI/IDE bridge) 
1021	 mate    Mate name                               
1022	 model   Type/Chipset of IDE controller          
1023	..............................................................................
1024	
1025	Each device  connected  to  a  controller  has  a separate subdirectory in the
1026	controllers directory.  The  files  listed in table 1-7 are contained in these
1027	directories.
1028	
1029	
1030	Table 1-7: IDE device information
1031	..............................................................................
1032	 File             Content                                    
1033	 cache            The cache                                  
1034	 capacity         Capacity of the medium (in 512Byte blocks) 
1035	 driver           driver and version                         
1036	 geometry         physical and logical geometry              
1037	 identify         device identify block                      
1038	 media            media type                                 
1039	 model            device identifier                          
1040	 settings         device setup                               
1041	 smart_thresholds IDE disk management thresholds             
1042	 smart_values     IDE disk management values                 
1043	..............................................................................
1044	
1045	The most  interesting  file is settings. This file contains a nice overview of
1046	the drive parameters:
1047	
1048	  # cat /proc/ide/ide0/hda/settings 
1049	  name                    value           min             max             mode 
1050	  ----                    -----           ---             ---             ---- 
1051	  bios_cyl                526             0               65535           rw 
1052	  bios_head               255             0               255             rw 
1053	  bios_sect               63              0               63              rw 
1054	  breada_readahead        4               0               127             rw 
1055	  bswap                   0               0               1               r 
1056	  file_readahead          72              0               2097151         rw 
1057	  io_32bit                0               0               3               rw 
1058	  keepsettings            0               0               1               rw 
1059	  max_kb_per_request      122             1               127             rw 
1060	  multcount               0               0               8               rw 
1061	  nice1                   1               0               1               rw 
1062	  nowerr                  0               0               1               rw 
1063	  pio_mode                write-only      0               255             w 
1064	  slow                    0               0               1               rw 
1065	  unmaskirq               0               0               1               rw 
1066	  using_dma               0               0               1               rw 
1067	
1068	
1069	1.4 Networking info in /proc/net
1070	--------------------------------
1071	
1072	The subdirectory  /proc/net  follows  the  usual  pattern. Table 1-8 shows the
1073	additional values  you  get  for  IP  version 6 if you configure the kernel to
1074	support this. Table 1-9 lists the files and their meaning.
1075	
1076	
1077	Table 1-8: IPv6 info in /proc/net
1078	..............................................................................
1079	 File       Content                                               
1080	 udp6       UDP sockets (IPv6)                                    
1081	 tcp6       TCP sockets (IPv6)                                    
1082	 raw6       Raw device statistics (IPv6)                          
1083	 igmp6      IP multicast addresses, which this host joined (IPv6) 
1084	 if_inet6   List of IPv6 interface addresses                      
1085	 ipv6_route Kernel routing table for IPv6                         
1086	 rt6_stats  Global IPv6 routing tables statistics                 
1087	 sockstat6  Socket statistics (IPv6)                              
1088	 snmp6      Snmp data (IPv6)                                      
1089	..............................................................................
1090	
1091	
1092	Table 1-9: Network info in /proc/net
1093	..............................................................................
1094	 File          Content                                                         
1095	 arp           Kernel  ARP table                                               
1096	 dev           network devices with statistics                                 
1097	 dev_mcast     the Layer2 multicast groups a device is listening too
1098	               (interface index, label, number of references, number of bound
1099	               addresses). 
1100	 dev_stat      network device status                                           
1101	 ip_fwchains   Firewall chain linkage                                          
1102	 ip_fwnames    Firewall chain names                                            
1103	 ip_masq       Directory containing the masquerading tables                    
1104	 ip_masquerade Major masquerading table                                        
1105	 netstat       Network statistics                                              
1106	 raw           raw device statistics                                           
1107	 route         Kernel routing table                                            
1108	 rpc           Directory containing rpc info                                   
1109	 rt_cache      Routing cache                                                   
1110	 snmp          SNMP data                                                       
1111	 sockstat      Socket statistics                                               
1112	 tcp           TCP  sockets                                                    
1113	 udp           UDP sockets                                                     
1114	 unix          UNIX domain sockets                                             
1115	 wireless      Wireless interface data (Wavelan etc)                           
1116	 igmp          IP multicast addresses, which this host joined                  
1117	 psched        Global packet scheduler parameters.                             
1118	 netlink       List of PF_NETLINK sockets                                      
1119	 ip_mr_vifs    List of multicast virtual interfaces                            
1120	 ip_mr_cache   List of multicast routing cache                                 
1121	..............................................................................
1122	
1123	You can  use  this  information  to see which network devices are available in
1124	your system and how much traffic was routed over those devices:
1125	
1126	  > cat /proc/net/dev 
1127	  Inter-|Receive                                                   |[... 
1128	   face |bytes    packets errs drop fifo frame compressed multicast|[... 
1129	      lo:  908188   5596     0    0    0     0          0         0 [...         
1130	    ppp0:15475140  20721   410    0    0   410          0         0 [...  
1131	    eth0:  614530   7085     0    0    0     0          0         1 [... 
1132	   
1133	  ...] Transmit 
1134	  ...] bytes    packets errs drop fifo colls carrier compressed 
1135	  ...]  908188     5596    0    0    0     0       0          0 
1136	  ...] 1375103    17405    0    0    0     0       0          0 
1137	  ...] 1703981     5535    0    0    0     3       0          0 
1138	
1139	In addition, each Channel Bond interface has its own directory.  For
1140	example, the bond0 device will have a directory called /proc/net/bond0/.
1141	It will contain information that is specific to that bond, such as the
1142	current slaves of the bond, the link status of the slaves, and how
1143	many times the slaves link has failed.
1144	
1145	1.5 SCSI info
1146	-------------
1147	
1148	If you  have  a  SCSI  host adapter in your system, you'll find a subdirectory
1149	named after  the driver for this adapter in /proc/scsi. You'll also see a list
1150	of all recognized SCSI devices in /proc/scsi:
1151	
1152	  >cat /proc/scsi/scsi 
1153	  Attached devices: 
1154	  Host: scsi0 Channel: 00 Id: 00 Lun: 00 
1155	    Vendor: IBM      Model: DGHS09U          Rev: 03E0 
1156	    Type:   Direct-Access                    ANSI SCSI revision: 03 
1157	  Host: scsi0 Channel: 00 Id: 06 Lun: 00 
1158	    Vendor: PIONEER  Model: CD-ROM DR-U06S   Rev: 1.04 
1159	    Type:   CD-ROM                           ANSI SCSI revision: 02 
1160	
1161	
1162	The directory  named  after  the driver has one file for each adapter found in
1163	the system.  These  files  contain information about the controller, including
1164	the used  IRQ  and  the  IO  address range. The amount of information shown is
1165	dependent on  the adapter you use. The example shows the output for an Adaptec
1166	AHA-2940 SCSI adapter:
1167	
1168	  > cat /proc/scsi/aic7xxx/0 
1169	   
1170	  Adaptec AIC7xxx driver version: 5.1.19/3.2.4 
1171	  Compile Options: 
1172	    TCQ Enabled By Default : Disabled 
1173	    AIC7XXX_PROC_STATS     : Disabled 
1174	    AIC7XXX_RESET_DELAY    : 5 
1175	  Adapter Configuration: 
1176	             SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 
1177	                             Ultra Wide Controller 
1178	      PCI MMAPed I/O Base: 0xeb001000 
1179	   Adapter SEEPROM Config: SEEPROM found and used. 
1180	        Adaptec SCSI BIOS: Enabled 
1181	                      IRQ: 10 
1182	                     SCBs: Active 0, Max Active 2, 
1183	                           Allocated 15, HW 16, Page 255 
1184	               Interrupts: 160328 
1185	        BIOS Control Word: 0x18b6 
1186	     Adapter Control Word: 0x005b 
1187	     Extended Translation: Enabled 
1188	  Disconnect Enable Flags: 0xffff 
1189	       Ultra Enable Flags: 0x0001 
1190	   Tag Queue Enable Flags: 0x0000 
1191	  Ordered Queue Tag Flags: 0x0000 
1192	  Default Tag Queue Depth: 8 
1193	      Tagged Queue By Device array for aic7xxx host instance 0: 
1194	        {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 
1195	      Actual queue depth per device for aic7xxx host instance 0: 
1196	        {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 
1197	  Statistics: 
1198	  (scsi0:0:0:0) 
1199	    Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 
1200	    Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 
1201	    Total transfers 160151 (74577 reads and 85574 writes) 
1202	  (scsi0:0:6:0) 
1203	    Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 
1204	    Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 
1205	    Total transfers 0 (0 reads and 0 writes) 
1206	
1207	
1208	1.6 Parallel port info in /proc/parport
1209	---------------------------------------
1210	
1211	The directory  /proc/parport  contains information about the parallel ports of
1212	your system.  It  has  one  subdirectory  for  each port, named after the port
1213	number (0,1,2,...).
1214	
1215	These directories contain the four files shown in Table 1-10.
1216	
1217	
1218	Table 1-10: Files in /proc/parport
1219	..............................................................................
1220	 File      Content                                                             
1221	 autoprobe Any IEEE-1284 device ID information that has been acquired.         
1222	 devices   list of the device drivers using that port. A + will appear by the
1223	           name of the device currently using the port (it might not appear
1224	           against any). 
1225	 hardware  Parallel port's base address, IRQ line and DMA channel.             
1226	 irq       IRQ that parport is using for that port. This is in a separate
1227	           file to allow you to alter it by writing a new value in (IRQ
1228	           number or none). 
1229	..............................................................................
1230	
1231	1.7 TTY info in /proc/tty
1232	-------------------------
1233	
1234	Information about  the  available  and actually used tty's can be found in the
1235	directory /proc/tty.You'll  find  entries  for drivers and line disciplines in
1236	this directory, as shown in Table 1-11.
1237	
1238	
1239	Table 1-11: Files in /proc/tty
1240	..............................................................................
1241	 File          Content                                        
1242	 drivers       list of drivers and their usage                
1243	 ldiscs        registered line disciplines                    
1244	 driver/serial usage statistic and status of single tty lines 
1245	..............................................................................
1246	
1247	To see  which  tty's  are  currently in use, you can simply look into the file
1248	/proc/tty/drivers:
1249	
1250	  > cat /proc/tty/drivers 
1251	  pty_slave            /dev/pts      136   0-255 pty:slave 
1252	  pty_master           /dev/ptm      128   0-255 pty:master 
1253	  pty_slave            /dev/ttyp       3   0-255 pty:slave 
1254	  pty_master           /dev/pty        2   0-255 pty:master 
1255	  serial               /dev/cua        5   64-67 serial:callout 
1256	  serial               /dev/ttyS       4   64-67 serial 
1257	  /dev/tty0            /dev/tty0       4       0 system:vtmaster 
1258	  /dev/ptmx            /dev/ptmx       5       2 system 
1259	  /dev/console         /dev/console    5       1 system:console 
1260	  /dev/tty             /dev/tty        5       0 system:/dev/tty 
1261	  unknown              /dev/tty        4    1-63 console 
1262	
1263	
1264	1.8 Miscellaneous kernel statistics in /proc/stat
1265	-------------------------------------------------
1266	
1267	Various pieces   of  information about  kernel activity  are  available in the
1268	/proc/stat file.  All  of  the numbers reported  in  this file are  aggregates
1269	since the system first booted.  For a quick look, simply cat the file:
1270	
1271	  > cat /proc/stat
1272	  cpu  2255 34 2290 22625563 6290 127 456 0 0 0
1273	  cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1274	  cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1275	  intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1276	  ctxt 1990473
1277	  btime 1062191376
1278	  processes 2915
1279	  procs_running 1
1280	  procs_blocked 0
1281	  softirq 183433 0 21755 12 39 1137 231 21459 2263
1282	
1283	The very first  "cpu" line aggregates the  numbers in all  of the other "cpuN"
1284	lines.  These numbers identify the amount of time the CPU has spent performing
1285	different kinds of work.  Time units are in USER_HZ (typically hundredths of a
1286	second).  The meanings of the columns are as follows, from left to right:
1287	
1288	- user: normal processes executing in user mode
1289	- nice: niced processes executing in user mode
1290	- system: processes executing in kernel mode
1291	- idle: twiddling thumbs
1292	- iowait: waiting for I/O to complete
1293	- irq: servicing interrupts
1294	- softirq: servicing softirqs
1295	- steal: involuntary wait
1296	- guest: running a normal guest
1297	- guest_nice: running a niced guest
1298	
1299	The "intr" line gives counts of interrupts  serviced since boot time, for each
1300	of the  possible system interrupts.   The first  column  is the  total of  all
1301	interrupts serviced  including  unnumbered  architecture specific  interrupts;
1302	each  subsequent column is the  total for that particular numbered interrupt.
1303	Unnumbered interrupts are not shown, only summed into the total.
1304	
1305	The "ctxt" line gives the total number of context switches across all CPUs.
1306	
1307	The "btime" line gives  the time at which the  system booted, in seconds since
1308	the Unix epoch.
1309	
1310	The "processes" line gives the number  of processes and threads created, which
1311	includes (but  is not limited  to) those  created by  calls to the  fork() and
1312	clone() system calls.
1313	
1314	The "procs_running" line gives the total number of threads that are
1315	running or ready to run (i.e., the total number of runnable threads).
1316	
1317	The   "procs_blocked" line gives  the  number of  processes currently blocked,
1318	waiting for I/O to complete.
1319	
1320	The "softirq" line gives counts of softirqs serviced since boot time, for each
1321	of the possible system softirqs. The first column is the total of all
1322	softirqs serviced; each subsequent column is the total for that particular
1323	softirq.
1324	
1325	
1326	1.9 Ext4 file system parameters
1327	-------------------------------
1328	
1329	Information about mounted ext4 file systems can be found in
1330	/proc/fs/ext4.  Each mounted filesystem will have a directory in
1331	/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1332	/proc/fs/ext4/dm-0).   The files in each per-device directory are shown
1333	in Table 1-12, below.
1334	
1335	Table 1-12: Files in /proc/fs/ext4/<devname>
1336	..............................................................................
1337	 File            Content                                        
1338	 mb_groups       details of multiblock allocator buddy cache of free blocks
1339	..............................................................................
1340	
1341	2.0 /proc/consoles
1342	------------------
1343	Shows registered system console lines.
1344	
1345	To see which character device lines are currently used for the system console
1346	/dev/console, you may simply look into the file /proc/consoles:
1347	
1348	  > cat /proc/consoles
1349	  tty0                 -WU (ECp)       4:7
1350	  ttyS0                -W- (Ep)        4:64
1351	
1352	The columns are:
1353	
1354	  device               name of the device
1355	  operations           R = can do read operations
1356	                       W = can do write operations
1357	                       U = can do unblank
1358	  flags                E = it is enabled
1359	                       C = it is preferred console
1360	                       B = it is primary boot console
1361	                       p = it is used for printk buffer
1362	                       b = it is not a TTY but a Braille device
1363	                       a = it is safe to use when cpu is offline
1364	  major:minor          major and minor number of the device separated by a colon
1365	
1366	------------------------------------------------------------------------------
1367	Summary
1368	------------------------------------------------------------------------------
1369	The /proc file system serves information about the running system. It not only
1370	allows access to process data but also allows you to request the kernel status
1371	by reading files in the hierarchy.
1372	
1373	The directory  structure  of /proc reflects the types of information and makes
1374	it easy, if not obvious, where to look for specific data.
1375	------------------------------------------------------------------------------
1376	
1377	------------------------------------------------------------------------------
1378	CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1379	------------------------------------------------------------------------------
1380	
1381	------------------------------------------------------------------------------
1382	In This Chapter
1383	------------------------------------------------------------------------------
1384	* Modifying kernel parameters by writing into files found in /proc/sys
1385	* Exploring the files which modify certain parameters
1386	* Review of the /proc/sys file tree
1387	------------------------------------------------------------------------------
1388	
1389	
1390	A very  interesting part of /proc is the directory /proc/sys. This is not only
1391	a source  of  information,  it also allows you to change parameters within the
1392	kernel. Be  very  careful  when attempting this. You can optimize your system,
1393	but you  can  also  cause  it  to  crash.  Never  alter kernel parameters on a
1394	production system.  Set  up  a  development machine and test to make sure that
1395	everything works  the  way  you want it to. You may have no alternative but to
1396	reboot the machine once an error has been made.
1397	
1398	To change  a  value,  simply  echo  the new value into the file. An example is
1399	given below  in the section on the file system data. You need to be root to do
1400	this. You  can  create  your  own  boot script to perform this every time your
1401	system boots.
1402	
1403	The files  in /proc/sys can be used to fine tune and monitor miscellaneous and
1404	general things  in  the operation of the Linux kernel. Since some of the files
1405	can inadvertently  disrupt  your  system,  it  is  advisable  to  read  both
1406	documentation and  source  before actually making adjustments. In any case, be
1407	very careful  when  writing  to  any  of these files. The entries in /proc may
1408	change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1409	review the kernel documentation in the directory /usr/src/linux/Documentation.
1410	This chapter  is  heavily  based  on the documentation included in the pre 2.2
1411	kernels, and became part of it in version 2.2.1 of the Linux kernel.
1412	
1413	Please see: Documentation/sysctl/ directory for descriptions of these
1414	entries.
1415	
1416	------------------------------------------------------------------------------
1417	Summary
1418	------------------------------------------------------------------------------
1419	Certain aspects  of  kernel  behavior  can be modified at runtime, without the
1420	need to  recompile  the kernel, or even to reboot the system. The files in the
1421	/proc/sys tree  can  not only be read, but also modified. You can use the echo
1422	command to write value into these files, thereby changing the default settings
1423	of the kernel.
1424	------------------------------------------------------------------------------
1425	
1426	------------------------------------------------------------------------------
1427	CHAPTER 3: PER-PROCESS PARAMETERS
1428	------------------------------------------------------------------------------
1429	
1430	3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1431	--------------------------------------------------------------------------------
1432	
1433	These file can be used to adjust the badness heuristic used to select which
1434	process gets killed in out of memory conditions.
1435	
1436	The badness heuristic assigns a value to each candidate task ranging from 0
1437	(never kill) to 1000 (always kill) to determine which process is targeted.  The
1438	units are roughly a proportion along that range of allowed memory the process
1439	may allocate from based on an estimation of its current memory and swap use.
1440	For example, if a task is using all allowed memory, its badness score will be
1441	1000.  If it is using half of its allowed memory, its score will be 500.
1442	
1443	There is an additional factor included in the badness score: the current memory
1444	and swap usage is discounted by 3% for root processes.
1445	
1446	The amount of "allowed" memory depends on the context in which the oom killer
1447	was called.  If it is due to the memory assigned to the allocating task's cpuset
1448	being exhausted, the allowed memory represents the set of mems assigned to that
1449	cpuset.  If it is due to a mempolicy's node(s) being exhausted, the allowed
1450	memory represents the set of mempolicy nodes.  If it is due to a memory
1451	limit (or swap limit) being reached, the allowed memory is that configured
1452	limit.  Finally, if it is due to the entire system being out of memory, the
1453	allowed memory represents all allocatable resources.
1454	
1455	The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1456	is used to determine which task to kill.  Acceptable values range from -1000
1457	(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX).  This allows userspace to
1458	polarize the preference for oom killing either by always preferring a certain
1459	task or completely disabling it.  The lowest possible value, -1000, is
1460	equivalent to disabling oom killing entirely for that task since it will always
1461	report a badness score of 0.
1462	
1463	Consequently, it is very simple for userspace to define the amount of memory to
1464	consider for each task.  Setting a /proc/<pid>/oom_score_adj value of +500, for
1465	example, is roughly equivalent to allowing the remainder of tasks sharing the
1466	same system, cpuset, mempolicy, or memory controller resources to use at least
1467	50% more memory.  A value of -500, on the other hand, would be roughly
1468	equivalent to discounting 50% of the task's allowed memory from being considered
1469	as scoring against the task.
1470	
1471	For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1472	be used to tune the badness score.  Its acceptable values range from -16
1473	(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1474	(OOM_DISABLE) to disable oom killing entirely for that task.  Its value is
1475	scaled linearly with /proc/<pid>/oom_score_adj.
1476	
1477	The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1478	value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1479	requires CAP_SYS_RESOURCE.
1480	
1481	Caveat: when a parent task is selected, the oom killer will sacrifice any first
1482	generation children with separate address spaces instead, if possible.  This
1483	avoids servers and important system daemons from being killed and loses the
1484	minimal amount of work.
1485	
1486	
1487	3.2 /proc/<pid>/oom_score - Display current oom-killer score
1488	-------------------------------------------------------------
1489	
1490	This file can be used to check the current score used by the oom-killer is for
1491	any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1492	process should be killed in an out-of-memory situation.
1493	
1494	
1495	3.3  /proc/<pid>/io - Display the IO accounting fields
1496	-------------------------------------------------------
1497	
1498	This file contains IO statistics for each running process
1499	
1500	Example
1501	-------
1502	
1503	test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1504	[1] 3828
1505	
1506	test:/tmp # cat /proc/3828/io
1507	rchar: 323934931
1508	wchar: 323929600
1509	syscr: 632687
1510	syscw: 632675
1511	read_bytes: 0
1512	write_bytes: 323932160
1513	cancelled_write_bytes: 0
1514	
1515	
1516	Description
1517	-----------
1518	
1519	rchar
1520	-----
1521	
1522	I/O counter: chars read
1523	The number of bytes which this task has caused to be read from storage. This
1524	is simply the sum of bytes which this process passed to read() and pread().
1525	It includes things like tty IO and it is unaffected by whether or not actual
1526	physical disk IO was required (the read might have been satisfied from
1527	pagecache)
1528	
1529	
1530	wchar
1531	-----
1532	
1533	I/O counter: chars written
1534	The number of bytes which this task has caused, or shall cause to be written
1535	to disk. Similar caveats apply here as with rchar.
1536	
1537	
1538	syscr
1539	-----
1540	
1541	I/O counter: read syscalls
1542	Attempt to count the number of read I/O operations, i.e. syscalls like read()
1543	and pread().
1544	
1545	
1546	syscw
1547	-----
1548	
1549	I/O counter: write syscalls
1550	Attempt to count the number of write I/O operations, i.e. syscalls like
1551	write() and pwrite().
1552	
1553	
1554	read_bytes
1555	----------
1556	
1557	I/O counter: bytes read
1558	Attempt to count the number of bytes which this process really did cause to
1559	be fetched from the storage layer. Done at the submit_bio() level, so it is
1560	accurate for block-backed filesystems. <please add status regarding NFS and
1561	CIFS at a later time>
1562	
1563	
1564	write_bytes
1565	-----------
1566	
1567	I/O counter: bytes written
1568	Attempt to count the number of bytes which this process caused to be sent to
1569	the storage layer. This is done at page-dirtying time.
1570	
1571	
1572	cancelled_write_bytes
1573	---------------------
1574	
1575	The big inaccuracy here is truncate. If a process writes 1MB to a file and
1576	then deletes the file, it will in fact perform no writeout. But it will have
1577	been accounted as having caused 1MB of write.
1578	In other words: The number of bytes which this process caused to not happen,
1579	by truncating pagecache. A task can cause "negative" IO too. If this task
1580	truncates some dirty pagecache, some IO which another task has been accounted
1581	for (in its write_bytes) will not be happening. We _could_ just subtract that
1582	from the truncating task's write_bytes, but there is information loss in doing
1583	that.
1584	
1585	
1586	Note
1587	----
1588	
1589	At its current implementation state, this is a bit racy on 32-bit machines: if
1590	process A reads process B's /proc/pid/io while process B is updating one of
1591	those 64-bit counters, process A could see an intermediate result.
1592	
1593	
1594	More information about this can be found within the taskstats documentation in
1595	Documentation/accounting.
1596	
1597	3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1598	---------------------------------------------------------------
1599	When a process is dumped, all anonymous memory is written to a core file as
1600	long as the size of the core file isn't limited. But sometimes we don't want
1601	to dump some memory segments, for example, huge shared memory. Conversely,
1602	sometimes we want to save file-backed memory segments into a core file, not
1603	only the individual files.
1604	
1605	/proc/<pid>/coredump_filter allows you to customize which memory segments
1606	will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1607	of memory types. If a bit of the bitmask is set, memory segments of the
1608	corresponding memory type are dumped, otherwise they are not dumped.
1609	
1610	The following 7 memory types are supported:
1611	  - (bit 0) anonymous private memory
1612	  - (bit 1) anonymous shared memory
1613	  - (bit 2) file-backed private memory
1614	  - (bit 3) file-backed shared memory
1615	  - (bit 4) ELF header pages in file-backed private memory areas (it is
1616	            effective only if the bit 2 is cleared)
1617	  - (bit 5) hugetlb private memory
1618	  - (bit 6) hugetlb shared memory
1619	
1620	  Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1621	  are always dumped regardless of the bitmask status.
1622	
1623	  Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
1624	  effected by bit 5-6.
1625	
1626	Default value of coredump_filter is 0x23; this means all anonymous memory
1627	segments and hugetlb private memory are dumped.
1628	
1629	If you don't want to dump all shared memory segments attached to pid 1234,
1630	write 0x21 to the process's proc file.
1631	
1632	  $ echo 0x21 > /proc/1234/coredump_filter
1633	
1634	When a new process is created, the process inherits the bitmask status from its
1635	parent. It is useful to set up coredump_filter before the program runs.
1636	For example:
1637	
1638	  $ echo 0x7 > /proc/self/coredump_filter
1639	  $ ./some_program
1640	
1641	3.5	/proc/<pid>/mountinfo - Information about mounts
1642	--------------------------------------------------------
1643	
1644	This file contains lines of the form:
1645	
1646	36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1647	(1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
1648	
1649	(1) mount ID:  unique identifier of the mount (may be reused after umount)
1650	(2) parent ID:  ID of parent (or of self for the top of the mount tree)
1651	(3) major:minor:  value of st_dev for files on filesystem
1652	(4) root:  root of the mount within the filesystem
1653	(5) mount point:  mount point relative to the process's root
1654	(6) mount options:  per mount options
1655	(7) optional fields:  zero or more fields of the form "tag[:value]"
1656	(8) separator:  marks the end of the optional fields
1657	(9) filesystem type:  name of filesystem of the form "type[.subtype]"
1658	(10) mount source:  filesystem specific information or "none"
1659	(11) super options:  per super block options
1660	
1661	Parsers should ignore all unrecognised optional fields.  Currently the
1662	possible optional fields are:
1663	
1664	shared:X  mount is shared in peer group X
1665	master:X  mount is slave to peer group X
1666	propagate_from:X  mount is slave and receives propagation from peer group X (*)
1667	unbindable  mount is unbindable
1668	
1669	(*) X is the closest dominant peer group under the process's root.  If
1670	X is the immediate master of the mount, or if there's no dominant peer
1671	group under the same root, then only the "master:X" field is present
1672	and not the "propagate_from:X" field.
1673	
1674	For more information on mount propagation see:
1675	
1676	  Documentation/filesystems/sharedsubtree.txt
1677	
1678	
1679	3.6	/proc/<pid>/comm  & /proc/<pid>/task/<tid>/comm
1680	--------------------------------------------------------
1681	These files provide a method to access a tasks comm value. It also allows for
1682	a task to set its own or one of its thread siblings comm value. The comm value
1683	is limited in size compared to the cmdline value, so writing anything longer
1684	then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1685	comm value.
1686	
1687	
1688	3.7	/proc/<pid>/task/<tid>/children - Information about task children
1689	-------------------------------------------------------------------------
1690	This file provides a fast way to retrieve first level children pids
1691	of a task pointed by <pid>/<tid> pair. The format is a space separated
1692	stream of pids.
1693	
1694	Note the "first level" here -- if a child has own children they will
1695	not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1696	to obtain the descendants.
1697	
1698	Since this interface is intended to be fast and cheap it doesn't
1699	guarantee to provide precise results and some children might be
1700	skipped, especially if they've exited right after we printed their
1701	pids, so one need to either stop or freeze processes being inspected
1702	if precise results are needed.
1703	
1704	
1705	3.8	/proc/<pid>/fdinfo/<fd> - Information about opened file
1706	---------------------------------------------------------------
1707	This file provides information associated with an opened file. The regular
1708	files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1709	represents the current offset of the opened file in decimal form [see lseek(2)
1710	for details], 'flags' denotes the octal O_xxx mask the file has been
1711	created with [see open(2) for details] and 'mnt_id' represents mount ID of
1712	the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1713	for details].
1714	
1715	A typical output is
1716	
1717		pos:	0
1718		flags:	0100002
1719		mnt_id:	19
1720	
1721	All locks associated with a file descriptor are shown in its fdinfo too.
1722	
1723	lock:       1: FLOCK  ADVISORY  WRITE 359 00:13:11691 0 EOF
1724	
1725	The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1726	pair provide additional information particular to the objects they represent.
1727	
1728		Eventfd files
1729		~~~~~~~~~~~~~
1730		pos:	0
1731		flags:	04002
1732		mnt_id:	9
1733		eventfd-count:	5a
1734	
1735		where 'eventfd-count' is hex value of a counter.
1736	
1737		Signalfd files
1738		~~~~~~~~~~~~~~
1739		pos:	0
1740		flags:	04002
1741		mnt_id:	9
1742		sigmask:	0000000000000200
1743	
1744		where 'sigmask' is hex value of the signal mask associated
1745		with a file.
1746	
1747		Epoll files
1748		~~~~~~~~~~~
1749		pos:	0
1750		flags:	02
1751		mnt_id:	9
1752		tfd:        5 events:       1d data: ffffffffffffffff
1753	
1754		where 'tfd' is a target file descriptor number in decimal form,
1755		'events' is events mask being watched and the 'data' is data
1756		associated with a target [see epoll(7) for more details].
1757	
1758		Fsnotify files
1759		~~~~~~~~~~~~~~
1760		For inotify files the format is the following
1761	
1762		pos:	0
1763		flags:	02000000
1764		inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1765	
1766		where 'wd' is a watch descriptor in decimal form, ie a target file
1767		descriptor number, 'ino' and 'sdev' are inode and device where the
1768		target file resides and the 'mask' is the mask of events, all in hex
1769		form [see inotify(7) for more details].
1770	
1771		If the kernel was built with exportfs support, the path to the target
1772		file is encoded as a file handle.  The file handle is provided by three
1773		fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1774		format.
1775	
1776		If the kernel is built without exportfs support the file handle won't be
1777		printed out.
1778	
1779		If there is no inotify mark attached yet the 'inotify' line will be omitted.
1780	
1781		For fanotify files the format is
1782	
1783		pos:	0
1784		flags:	02
1785		mnt_id:	9
1786		fanotify flags:10 event-flags:0
1787		fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1788		fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1789	
1790		where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1791		call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1792		flags associated with mark which are tracked separately from events
1793		mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1794		mask and 'ignored_mask' is the mask of events which are to be ignored.
1795		All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1796		does provide information about flags and mask used in fanotify_mark
1797		call [see fsnotify manpage for details].
1798	
1799		While the first three lines are mandatory and always printed, the rest is
1800		optional and may be omitted if no marks created yet.
1801	
1802		Timerfd files
1803		~~~~~~~~~~~~~
1804	
1805		pos:	0
1806		flags:	02
1807		mnt_id:	9
1808		clockid: 0
1809		ticks: 0
1810		settime flags: 01
1811		it_value: (0, 49406829)
1812		it_interval: (1, 0)
1813	
1814		where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
1815		that have occurred [see timerfd_create(2) for details]. 'settime flags' are
1816		flags in octal form been used to setup the timer [see timerfd_settime(2) for
1817		details]. 'it_value' is remaining time until the timer exiration.
1818		'it_interval' is the interval for the timer. Note the timer might be set up
1819		with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
1820		still exhibits timer's remaining time.
1821	
1822	3.9	/proc/<pid>/map_files - Information about memory mapped files
1823	---------------------------------------------------------------------
1824	This directory contains symbolic links which represent memory mapped files
1825	the process is maintaining.  Example output:
1826	
1827	     | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
1828	     | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
1829	     | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
1830	     | ...
1831	     | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
1832	     | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
1833	
1834	The name of a link represents the virtual memory bounds of a mapping, i.e.
1835	vm_area_struct::vm_start-vm_area_struct::vm_end.
1836	
1837	The main purpose of the map_files is to retrieve a set of memory mapped
1838	files in a fast way instead of parsing /proc/<pid>/maps or
1839	/proc/<pid>/smaps, both of which contain many more records.  At the same
1840	time one can open(2) mappings from the listings of two processes and
1841	comparing their inode numbers to figure out which anonymous memory areas
1842	are actually shared.
1843	
1844	------------------------------------------------------------------------------
1845	Configuring procfs
1846	------------------------------------------------------------------------------
1847	
1848	4.1	Mount options
1849	---------------------
1850	
1851	The following mount options are supported:
1852	
1853		hidepid=	Set /proc/<pid>/ access mode.
1854		gid=		Set the group authorized to learn processes information.
1855	
1856	hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1857	(default).
1858	
1859	hidepid=1 means users may not access any /proc/<pid>/ directories but their
1860	own.  Sensitive files like cmdline, sched*, status are now protected against
1861	other users.  This makes it impossible to learn whether any user runs
1862	specific program (given the program doesn't reveal itself by its behaviour).
1863	As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1864	poorly written programs passing sensitive information via program arguments are
1865	now protected against local eavesdroppers.
1866	
1867	hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1868	users.  It doesn't mean that it hides a fact whether a process with a specific
1869	pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1870	but it hides process' uid and gid, which may be learned by stat()'ing
1871	/proc/<pid>/ otherwise.  It greatly complicates an intruder's task of gathering
1872	information about running processes, whether some daemon runs with elevated
1873	privileges, whether other user runs some sensitive program, whether other users
1874	run any program at all, etc.
1875	
1876	gid= defines a group authorized to learn processes information otherwise
1877	prohibited by hidepid=.  If you use some daemon like identd which needs to learn
1878	information about processes information, just add identd to this group.
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