About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / filesystems / proc.txt




Custom Search

Based on kernel version 4.9. Page generated on 2016-12-21 14:34 EST.

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

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.