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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
72.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
8move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
9------------------------------------------------------------------------------
10Version 1.3 Kernel version 2.2.12
11 Kernel version 2.4.0-test11-pre4
12------------------------------------------------------------------------------
13fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009
14
15Table of Contents
16-----------------
17
18 0 Preface
19 0.1 Introduction/Credits
20 0.2 Legal Stuff
21
22 1 Collecting System Information
23 1.1 Process-Specific Subdirectories
24 1.2 Kernel data
25 1.3 IDE devices in /proc/ide
26 1.4 Networking info in /proc/net
27 1.5 SCSI info
28 1.6 Parallel port info in /proc/parport
29 1.7 TTY info in /proc/tty
30 1.8 Miscellaneous kernel statistics in /proc/stat
31 1.9 Ext4 file system parameters
32
33 2 Modifying System Parameters
34
35 3 Per-Process Parameters
36 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
37 score
38 3.2 /proc/<pid>/oom_score - Display current oom-killer score
39 3.3 /proc/<pid>/io - Display the IO accounting fields
40 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
41 3.5 /proc/<pid>/mountinfo - Information about mounts
42 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
43 3.7 /proc/<pid>/task/<tid>/children - Information about task children
44 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
45 3.9 /proc/<pid>/map_files - Information about memory mapped files
46 3.10 /proc/<pid>/timerslack_ns - Task timerslack value
47 3.11 /proc/<pid>/patch_state - Livepatch patch operation state
48
49 4 Configuring procfs
50 4.1 Mount options
51
52------------------------------------------------------------------------------
53Preface
54------------------------------------------------------------------------------
55
560.1 Introduction/Credits
57------------------------
58
59This documentation is part of a soon (or so we hope) to be released book on
60the SuSE Linux distribution. As there is no complete documentation for the
61/proc file system and we've used many freely available sources to write these
62chapters, it seems only fair to give the work back to the Linux community.
63This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
64afraid it's still far from complete, but we hope it will be useful. As far as
65we know, it is the first 'all-in-one' document about the /proc file system. It
66is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
67SPARC, AXP, etc., features, you probably won't find what you are looking for.
68It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
69additions and patches are welcome and will be added to this document if you
70mail them to Bodo.
71
72We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
73other people for help compiling this documentation. We'd also like to extend a
74special thank you to Andi Kleen for documentation, which we relied on heavily
75to create this document, as well as the additional information he provided.
76Thanks to everybody else who contributed source or docs to the Linux kernel
77and helped create a great piece of software... :)
78
79If you have any comments, corrections or additions, please don't hesitate to
80contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
81document.
82
83The latest version of this document is available online at
84http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
85
86If the above direction does not works for you, you could try the kernel
87mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
88comandante@zaralinux.com.
89
900.2 Legal Stuff
91---------------
92
93We don't guarantee the correctness of this document, and if you come to us
94complaining about how you screwed up your system because of incorrect
95documentation, we won't feel responsible...
96
97------------------------------------------------------------------------------
98CHAPTER 1: COLLECTING SYSTEM INFORMATION
99------------------------------------------------------------------------------
100
101------------------------------------------------------------------------------
102In This Chapter
103------------------------------------------------------------------------------
104* Investigating the properties of the pseudo file system /proc and its
105 ability to provide information on the running Linux system
106* Examining /proc's structure
107* Uncovering various information about the kernel and the processes running
108 on the system
109------------------------------------------------------------------------------
110
111
112The proc file system acts as an interface to internal data structures in the
113kernel. It can be used to obtain information about the system and to change
114certain kernel parameters at runtime (sysctl).
115
116First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
117show you how you can use /proc/sys to change settings.
118
1191.1 Process-Specific Subdirectories
120-----------------------------------
121
122The directory /proc contains (among other things) one subdirectory for each
123process running on the system, which is named after the process ID (PID).
124
125The link self points to the process reading the file system. Each process
126subdirectory has the entries listed in Table 1-1.
127
128
129Table 1-1: Process specific entries in /proc
130..............................................................................
131 File Content
132 clear_refs Clears page referenced bits shown in smaps output
133 cmdline Command line arguments
134 cpu Current and last cpu in which it was executed (2.4)(smp)
135 cwd Link to the current working directory
136 environ Values of environment variables
137 exe Link to the executable of this process
138 fd Directory, which contains all file descriptors
139 maps Memory maps to executables and library files (2.4)
140 mem Memory held by this process
141 root Link to the root directory of this process
142 stat Process status
143 statm Process memory status information
144 status Process status in human readable form
145 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function
146 symbol the task is blocked in - or "0" if not blocked.
147 pagemap Page table
148 stack Report full stack trace, enable via CONFIG_STACKTRACE
149 smaps an extension based on maps, showing the memory consumption of
150 each mapping and flags associated with it
151 numa_maps an extension based on maps, showing the memory locality and
152 binding policy as well as mem usage (in pages) of each mapping.
153..............................................................................
154
155For example, to get the status information of a process, all you have to do is
156read the file /proc/PID/status:
157
158 >cat /proc/self/status
159 Name: cat
160 State: R (running)
161 Tgid: 5452
162 Pid: 5452
163 PPid: 743
164 TracerPid: 0 (2.4)
165 Uid: 501 501 501 501
166 Gid: 100 100 100 100
167 FDSize: 256
168 Groups: 100 14 16
169 VmPeak: 5004 kB
170 VmSize: 5004 kB
171 VmLck: 0 kB
172 VmHWM: 476 kB
173 VmRSS: 476 kB
174 RssAnon: 352 kB
175 RssFile: 120 kB
176 RssShmem: 4 kB
177 VmData: 156 kB
178 VmStk: 88 kB
179 VmExe: 68 kB
180 VmLib: 1412 kB
181 VmPTE: 20 kb
182 VmSwap: 0 kB
183 HugetlbPages: 0 kB
184 CoreDumping: 0
185 Threads: 1
186 SigQ: 0/28578
187 SigPnd: 0000000000000000
188 ShdPnd: 0000000000000000
189 SigBlk: 0000000000000000
190 SigIgn: 0000000000000000
191 SigCgt: 0000000000000000
192 CapInh: 00000000fffffeff
193 CapPrm: 0000000000000000
194 CapEff: 0000000000000000
195 CapBnd: ffffffffffffffff
196 NoNewPrivs: 0
197 Seccomp: 0
198 voluntary_ctxt_switches: 0
199 nonvoluntary_ctxt_switches: 1
200
201This shows you nearly the same information you would get if you viewed it with
202the ps command. In fact, ps uses the proc file system to obtain its
203information. But you get a more detailed view of the process by reading the
204file /proc/PID/status. It fields are described in table 1-2.
205
206The statm file contains more detailed information about the process
207memory usage. Its seven fields are explained in Table 1-3. The stat file
208contains details information about the process itself. Its fields are
209explained in Table 1-4.
210
211(for SMP CONFIG users)
212For making accounting scalable, RSS related information are handled in an
213asynchronous manner and the value may not be very precise. To see a precise
214snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
215It's slow but very precise.
216
217Table 1-2: Contents of the status files (as of 4.8)
218..............................................................................
219 Field Content
220 Name filename of the executable
221 Umask file mode creation mask
222 State state (R is running, S is sleeping, D is sleeping
223 in an uninterruptible wait, Z is zombie,
224 T is traced or stopped)
225 Tgid thread group ID
226 Ngid NUMA group ID (0 if none)
227 Pid process id
228 PPid process id of the parent process
229 TracerPid PID of process tracing this process (0 if not)
230 Uid Real, effective, saved set, and file system UIDs
231 Gid Real, effective, saved set, and file system GIDs
232 FDSize number of file descriptor slots currently allocated
233 Groups supplementary group list
234 NStgid descendant namespace thread group ID hierarchy
235 NSpid descendant namespace process ID hierarchy
236 NSpgid descendant namespace process group ID hierarchy
237 NSsid descendant namespace session ID hierarchy
238 VmPeak peak virtual memory size
239 VmSize total program size
240 VmLck locked memory size
241 VmPin pinned memory size
242 VmHWM peak resident set size ("high water mark")
243 VmRSS size of memory portions. It contains the three
244 following parts (VmRSS = RssAnon + RssFile + RssShmem)
245 RssAnon size of resident anonymous memory
246 RssFile size of resident file mappings
247 RssShmem size of resident shmem memory (includes SysV shm,
248 mapping of tmpfs and shared anonymous mappings)
249 VmData size of private data segments
250 VmStk size of stack segments
251 VmExe size of text segment
252 VmLib size of shared library code
253 VmPTE size of page table entries
254 VmSwap amount of swap used by anonymous private data
255 (shmem swap usage is not included)
256 HugetlbPages size of hugetlb memory portions
257 CoreDumping process's memory is currently being dumped
258 (killing the process may lead to a corrupted core)
259 Threads number of threads
260 SigQ number of signals queued/max. number for queue
261 SigPnd bitmap of pending signals for the thread
262 ShdPnd bitmap of shared pending signals for the process
263 SigBlk bitmap of blocked signals
264 SigIgn bitmap of ignored signals
265 SigCgt bitmap of caught signals
266 CapInh bitmap of inheritable capabilities
267 CapPrm bitmap of permitted capabilities
268 CapEff bitmap of effective capabilities
269 CapBnd bitmap of capabilities bounding set
270 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
271 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
272 Cpus_allowed mask of CPUs on which this process may run
273 Cpus_allowed_list Same as previous, but in "list format"
274 Mems_allowed mask of memory nodes allowed to this process
275 Mems_allowed_list Same as previous, but in "list format"
276 voluntary_ctxt_switches number of voluntary context switches
277 nonvoluntary_ctxt_switches number of non voluntary context switches
278..............................................................................
279
280Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
281..............................................................................
282 Field Content
283 size total program size (pages) (same as VmSize in status)
284 resident size of memory portions (pages) (same as VmRSS in status)
285 shared number of pages that are shared (i.e. backed by a file, same
286 as RssFile+RssShmem in status)
287 trs number of pages that are 'code' (not including libs; broken,
288 includes data segment)
289 lrs number of pages of library (always 0 on 2.6)
290 drs number of pages of data/stack (including libs; broken,
291 includes library text)
292 dt number of dirty pages (always 0 on 2.6)
293..............................................................................
294
295
296Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
297..............................................................................
298 Field Content
299 pid process id
300 tcomm filename of the executable
301 state state (R is running, S is sleeping, D is sleeping in an
302 uninterruptible wait, Z is zombie, T is traced or stopped)
303 ppid process id of the parent process
304 pgrp pgrp of the process
305 sid session id
306 tty_nr tty the process uses
307 tty_pgrp pgrp of the tty
308 flags task flags
309 min_flt number of minor faults
310 cmin_flt number of minor faults with child's
311 maj_flt number of major faults
312 cmaj_flt number of major faults with child's
313 utime user mode jiffies
314 stime kernel mode jiffies
315 cutime user mode jiffies with child's
316 cstime kernel mode jiffies with child's
317 priority priority level
318 nice nice level
319 num_threads number of threads
320 it_real_value (obsolete, always 0)
321 start_time time the process started after system boot
322 vsize virtual memory size
323 rss resident set memory size
324 rsslim current limit in bytes on the rss
325 start_code address above which program text can run
326 end_code address below which program text can run
327 start_stack address of the start of the main process stack
328 esp current value of ESP
329 eip current value of EIP
330 pending bitmap of pending signals
331 blocked bitmap of blocked signals
332 sigign bitmap of ignored signals
333 sigcatch bitmap of caught signals
334 0 (place holder, used to be the wchan address, use /proc/PID/wchan instead)
335 0 (place holder)
336 0 (place holder)
337 exit_signal signal to send to parent thread on exit
338 task_cpu which CPU the task is scheduled on
339 rt_priority realtime priority
340 policy scheduling policy (man sched_setscheduler)
341 blkio_ticks time spent waiting for block IO
342 gtime guest time of the task in jiffies
343 cgtime guest time of the task children in jiffies
344 start_data address above which program data+bss is placed
345 end_data address below which program data+bss is placed
346 start_brk address above which program heap can be expanded with brk()
347 arg_start address above which program command line is placed
348 arg_end address below which program command line is placed
349 env_start address above which program environment is placed
350 env_end address below which program environment is placed
351 exit_code the thread's exit_code in the form reported by the waitpid system call
352..............................................................................
353
354The /proc/PID/maps file containing the currently mapped memory regions and
355their access permissions.
356
357The format is:
358
359address perms offset dev inode pathname
360
36108048000-08049000 r-xp 00000000 03:00 8312 /opt/test
36208049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
3630804a000-0806b000 rw-p 00000000 00:00 0 [heap]
364a7cb1000-a7cb2000 ---p 00000000 00:00 0
365a7cb2000-a7eb2000 rw-p 00000000 00:00 0
366a7eb2000-a7eb3000 ---p 00000000 00:00 0
367a7eb3000-a7ed5000 rw-p 00000000 00:00 0
368a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
369a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
370a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
371a800b000-a800e000 rw-p 00000000 00:00 0
372a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
373a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
374a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
375a8024000-a8027000 rw-p 00000000 00:00 0
376a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
377a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
378a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
379aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
380ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
381
382where "address" is the address space in the process that it occupies, "perms"
383is a set of permissions:
384
385 r = read
386 w = write
387 x = execute
388 s = shared
389 p = private (copy on write)
390
391"offset" is the offset into the mapping, "dev" is the device (major:minor), and
392"inode" is the inode on that device. 0 indicates that no inode is associated
393with the memory region, as the case would be with BSS (uninitialized data).
394The "pathname" shows the name associated file for this mapping. If the mapping
395is not associated with a file:
396
397 [heap] = the heap of the program
398 [stack] = the stack of the main process
399 [vdso] = the "virtual dynamic shared object",
400 the kernel system call handler
401 [anon:<name>] = an anonymous mapping that has been
402 named by userspace
403
404 or if empty, the mapping is anonymous.
405
406The /proc/PID/smaps is an extension based on maps, showing the memory
407consumption for each of the process's mappings. For each of mappings there
408is a series of lines such as the following:
409
41008048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
411Size: 1084 kB
412Rss: 892 kB
413Pss: 374 kB
414Shared_Clean: 892 kB
415Shared_Dirty: 0 kB
416Private_Clean: 0 kB
417Private_Dirty: 0 kB
418Referenced: 892 kB
419Anonymous: 0 kB
420LazyFree: 0 kB
421AnonHugePages: 0 kB
422ShmemPmdMapped: 0 kB
423Shared_Hugetlb: 0 kB
424Private_Hugetlb: 0 kB
425Swap: 0 kB
426SwapPss: 0 kB
427KernelPageSize: 4 kB
428MMUPageSize: 4 kB
429Locked: 0 kB
430THPeligible: 0
431VmFlags: rd ex mr mw me dw
432Name: name from userspace
433
434the first of these lines shows the same information as is displayed for the
435mapping in /proc/PID/maps. The remaining lines show the size of the mapping
436(size), the amount of the mapping that is currently resident in RAM (RSS), the
437process' proportional share of this mapping (PSS), the number of clean and
438dirty private pages in the mapping.
439
440The "proportional set size" (PSS) of a process is the count of pages it has
441in memory, where each page is divided by the number of processes sharing it.
442So if a process has 1000 pages all to itself, and 1000 shared with one other
443process, its PSS will be 1500.
444Note that even a page which is part of a MAP_SHARED mapping, but has only
445a single pte mapped, i.e. is currently used by only one process, is accounted
446as private and not as shared.
447"Referenced" indicates the amount of memory currently marked as referenced or
448accessed.
449"Anonymous" shows the amount of memory that does not belong to any file. Even
450a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
451and a page is modified, the file page is replaced by a private anonymous copy.
452"LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE).
453The memory isn't freed immediately with madvise(). It's freed in memory
454pressure if the memory is clean. Please note that the printed value might
455be lower than the real value due to optimizations used in the current
456implementation. If this is not desirable please file a bug report.
457"AnonHugePages" shows the ammount of memory backed by transparent hugepage.
458"ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by
459huge pages.
460"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
461hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
462reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
463"Swap" shows how much would-be-anonymous memory is also used, but out on swap.
464For shmem mappings, "Swap" includes also the size of the mapped (and not
465replaced by copy-on-write) part of the underlying shmem object out on swap.
466"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
467does not take into account swapped out page of underlying shmem objects.
468"Locked" indicates whether the mapping is locked in memory or not.
469"THPeligible" indicates whether the mapping is eligible for THP pages - 1 if
470true, 0 otherwise.
471
472"VmFlags" field deserves a separate description. This member represents the kernel
473flags associated with the particular virtual memory area in two letter encoded
474manner. The codes are the following:
475 rd - readable
476 wr - writeable
477 ex - executable
478 sh - shared
479 mr - may read
480 mw - may write
481 me - may execute
482 ms - may share
483 gd - stack segment growns down
484 pf - pure PFN range
485 dw - disabled write to the mapped file
486 lo - pages are locked in memory
487 io - memory mapped I/O area
488 sr - sequential read advise provided
489 rr - random read advise provided
490 dc - do not copy area on fork
491 de - do not expand area on remapping
492 ac - area is accountable
493 nr - swap space is not reserved for the area
494 ht - area uses huge tlb pages
495 ar - architecture specific flag
496 dd - do not include area into core dump
497 sd - soft-dirty flag
498 mm - mixed map area
499 hg - huge page advise flag
500 nh - no-huge page advise flag
501 mg - mergable advise flag
502
503Note that there is no guarantee that every flag and associated mnemonic will
504be present in all further kernel releases. Things get changed, the flags may
505be vanished or the reverse -- new added. Interpretation of their meaning
506might change in future as well. So each consumer of these flags has to
507follow each specific kernel version for the exact semantic.
508
509The "Name" field will only be present on a mapping that has been named by
510userspace, and will show the name passed in by userspace.
511
512This file is only present if the CONFIG_MMU kernel configuration option is
513enabled.
514
515Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent
516output can be achieved only in the single read call).
517This typically manifests when doing partial reads of these files while the
518memory map is being modified. Despite the races, we do provide the following
519guarantees:
520
5211) The mapped addresses never go backwards, which implies no two
522 regions will ever overlap.
5232) If there is something at a given vaddr during the entirety of the
524 life of the smaps/maps walk, there will be some output for it.
525
526
527The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
528bits on both physical and virtual pages associated with a process, and the
529soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst
530for details).
531To clear the bits for all the pages associated with the process
532 > echo 1 > /proc/PID/clear_refs
533
534To clear the bits for the anonymous pages associated with the process
535 > echo 2 > /proc/PID/clear_refs
536
537To clear the bits for the file mapped pages associated with the process
538 > echo 3 > /proc/PID/clear_refs
539
540To clear the soft-dirty bit
541 > echo 4 > /proc/PID/clear_refs
542
543To reset the peak resident set size ("high water mark") to the process's
544current value:
545 > echo 5 > /proc/PID/clear_refs
546
547Any other value written to /proc/PID/clear_refs will have no effect.
548
549The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
550using /proc/kpageflags and number of times a page is mapped using
551/proc/kpagecount. For detailed explanation, see
552Documentation/admin-guide/mm/pagemap.rst.
553
554The /proc/pid/numa_maps is an extension based on maps, showing the memory
555locality and binding policy, as well as the memory usage (in pages) of
556each mapping. The output follows a general format where mapping details get
557summarized separated by blank spaces, one mapping per each file line:
558
559address policy mapping details
560
56100400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
56200600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5633206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
564320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5653206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5663206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5673206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
568320698b000 default file=/lib64/libc-2.12.so
5693206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
5703206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
5713206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
5727f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
5737f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
5747f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
5757fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
5767fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
577
578Where:
579"address" is the starting address for the mapping;
580"policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst);
581"mapping details" summarizes mapping data such as mapping type, page usage counters,
582node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
583size, in KB, that is backing the mapping up.
584
5851.2 Kernel data
586---------------
587
588Similar to the process entries, the kernel data files give information about
589the running kernel. The files used to obtain this information are contained in
590/proc and are listed in Table 1-5. Not all of these will be present in your
591system. It depends on the kernel configuration and the loaded modules, which
592files are there, and which are missing.
593
594Table 1-5: Kernel info in /proc
595..............................................................................
596 File Content
597 apm Advanced power management info
598 buddyinfo Kernel memory allocator information (see text) (2.5)
599 bus Directory containing bus specific information
600 cmdline Kernel command line
601 cpuinfo Info about the CPU
602 devices Available devices (block and character)
603 dma Used DMS channels
604 filesystems Supported filesystems
605 driver Various drivers grouped here, currently rtc (2.4)
606 execdomains Execdomains, related to security (2.4)
607 fb Frame Buffer devices (2.4)
608 fs File system parameters, currently nfs/exports (2.4)
609 ide Directory containing info about the IDE subsystem
610 interrupts Interrupt usage
611 iomem Memory map (2.4)
612 ioports I/O port usage
613 irq Masks for irq to cpu affinity (2.4)(smp?)
614 isapnp ISA PnP (Plug&Play) Info (2.4)
615 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
616 kmsg Kernel messages
617 ksyms Kernel symbol table
618 loadavg Load average of last 1, 5 & 15 minutes
619 locks Kernel locks
620 meminfo Memory info
621 misc Miscellaneous
622 modules List of loaded modules
623 mounts Mounted filesystems
624 net Networking info (see text)
625 pagetypeinfo Additional page allocator information (see text) (2.5)
626 partitions Table of partitions known to the system
627 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
628 decoupled by lspci (2.4)
629 rtc Real time clock
630 scsi SCSI info (see text)
631 slabinfo Slab pool info
632 softirqs softirq usage
633 stat Overall statistics
634 swaps Swap space utilization
635 sys See chapter 2
636 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
637 tty Info of tty drivers
638 uptime Wall clock since boot, combined idle time of all cpus
639 version Kernel version
640 video bttv info of video resources (2.4)
641 vmallocinfo Show vmalloced areas
642..............................................................................
643
644You can, for example, check which interrupts are currently in use and what
645they are used for by looking in the file /proc/interrupts:
646
647 > cat /proc/interrupts
648 CPU0
649 0: 8728810 XT-PIC timer
650 1: 895 XT-PIC keyboard
651 2: 0 XT-PIC cascade
652 3: 531695 XT-PIC aha152x
653 4: 2014133 XT-PIC serial
654 5: 44401 XT-PIC pcnet_cs
655 8: 2 XT-PIC rtc
656 11: 8 XT-PIC i82365
657 12: 182918 XT-PIC PS/2 Mouse
658 13: 1 XT-PIC fpu
659 14: 1232265 XT-PIC ide0
660 15: 7 XT-PIC ide1
661 NMI: 0
662
663In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
664output of a SMP machine):
665
666 > cat /proc/interrupts
667
668 CPU0 CPU1
669 0: 1243498 1214548 IO-APIC-edge timer
670 1: 8949 8958 IO-APIC-edge keyboard
671 2: 0 0 XT-PIC cascade
672 5: 11286 10161 IO-APIC-edge soundblaster
673 8: 1 0 IO-APIC-edge rtc
674 9: 27422 27407 IO-APIC-edge 3c503
675 12: 113645 113873 IO-APIC-edge PS/2 Mouse
676 13: 0 0 XT-PIC fpu
677 14: 22491 24012 IO-APIC-edge ide0
678 15: 2183 2415 IO-APIC-edge ide1
679 17: 30564 30414 IO-APIC-level eth0
680 18: 177 164 IO-APIC-level bttv
681 NMI: 2457961 2457959
682 LOC: 2457882 2457881
683 ERR: 2155
684
685NMI is incremented in this case because every timer interrupt generates a NMI
686(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
687
688LOC is the local interrupt counter of the internal APIC of every CPU.
689
690ERR is incremented in the case of errors in the IO-APIC bus (the bus that
691connects the CPUs in a SMP system. This means that an error has been detected,
692the IO-APIC automatically retry the transmission, so it should not be a big
693problem, but you should read the SMP-FAQ.
694
695In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
696/proc/interrupts to display every IRQ vector in use by the system, not
697just those considered 'most important'. The new vectors are:
698
699 THR -- interrupt raised when a machine check threshold counter
700 (typically counting ECC corrected errors of memory or cache) exceeds
701 a configurable threshold. Only available on some systems.
702
703 TRM -- a thermal event interrupt occurs when a temperature threshold
704 has been exceeded for the CPU. This interrupt may also be generated
705 when the temperature drops back to normal.
706
707 SPU -- a spurious interrupt is some interrupt that was raised then lowered
708 by some IO device before it could be fully processed by the APIC. Hence
709 the APIC sees the interrupt but does not know what device it came from.
710 For this case the APIC will generate the interrupt with a IRQ vector
711 of 0xff. This might also be generated by chipset bugs.
712
713 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
714 sent from one CPU to another per the needs of the OS. Typically,
715 their statistics are used by kernel developers and interested users to
716 determine the occurrence of interrupts of the given type.
717
718The above IRQ vectors are displayed only when relevant. For example,
719the threshold vector does not exist on x86_64 platforms. Others are
720suppressed when the system is a uniprocessor. As of this writing, only
721i386 and x86_64 platforms support the new IRQ vector displays.
722
723Of some interest is the introduction of the /proc/irq directory to 2.4.
724It could be used to set IRQ to CPU affinity, this means that you can "hook" an
725IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
726irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
727prof_cpu_mask.
728
729For example
730 > ls /proc/irq/
731 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
732 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
733 > ls /proc/irq/0/
734 smp_affinity
735
736smp_affinity is a bitmask, in which you can specify which CPUs can handle the
737IRQ, you can set it by doing:
738
739 > echo 1 > /proc/irq/10/smp_affinity
740
741This means that only the first CPU will handle the IRQ, but you can also echo
7425 which means that only the first and third CPU can handle the IRQ.
743
744The contents of each smp_affinity file is the same by default:
745
746 > cat /proc/irq/0/smp_affinity
747 ffffffff
748
749There is an alternate interface, smp_affinity_list which allows specifying
750a cpu range instead of a bitmask:
751
752 > cat /proc/irq/0/smp_affinity_list
753 1024-1031
754
755The default_smp_affinity mask applies to all non-active IRQs, which are the
756IRQs which have not yet been allocated/activated, and hence which lack a
757/proc/irq/[0-9]* directory.
758
759The node file on an SMP system shows the node to which the device using the IRQ
760reports itself as being attached. This hardware locality information does not
761include information about any possible driver locality preference.
762
763prof_cpu_mask specifies which CPUs are to be profiled by the system wide
764profiler. Default value is ffffffff (all cpus if there are only 32 of them).
765
766The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
767between all the CPUs which are allowed to handle it. As usual the kernel has
768more info than you and does a better job than you, so the defaults are the
769best choice for almost everyone. [Note this applies only to those IO-APIC's
770that support "Round Robin" interrupt distribution.]
771
772There are three more important subdirectories in /proc: net, scsi, and sys.
773The general rule is that the contents, or even the existence of these
774directories, depend on your kernel configuration. If SCSI is not enabled, the
775directory scsi may not exist. The same is true with the net, which is there
776only when networking support is present in the running kernel.
777
778The slabinfo file gives information about memory usage at the slab level.
779Linux uses slab pools for memory management above page level in version 2.2.
780Commonly used objects have their own slab pool (such as network buffers,
781directory cache, and so on).
782
783..............................................................................
784
785> cat /proc/buddyinfo
786
787Node 0, zone DMA 0 4 5 4 4 3 ...
788Node 0, zone Normal 1 0 0 1 101 8 ...
789Node 0, zone HighMem 2 0 0 1 1 0 ...
790
791External fragmentation is a problem under some workloads, and buddyinfo is a
792useful tool for helping diagnose these problems. Buddyinfo will give you a
793clue as to how big an area you can safely allocate, or why a previous
794allocation failed.
795
796Each column represents the number of pages of a certain order which are
797available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
798ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
799available in ZONE_NORMAL, etc...
800
801More information relevant to external fragmentation can be found in
802pagetypeinfo.
803
804> cat /proc/pagetypeinfo
805Page block order: 9
806Pages per block: 512
807
808Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
809Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
810Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
811Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
812Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
813Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
814Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
815Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
816Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
817Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
818Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
819
820Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
821Node 0, zone DMA 2 0 5 1 0
822Node 0, zone DMA32 41 6 967 2 0
823
824Fragmentation avoidance in the kernel works by grouping pages of different
825migrate types into the same contiguous regions of memory called page blocks.
826A page block is typically the size of the default hugepage size e.g. 2MB on
827X86-64. By keeping pages grouped based on their ability to move, the kernel
828can reclaim pages within a page block to satisfy a high-order allocation.
829
830The pagetypinfo begins with information on the size of a page block. It
831then gives the same type of information as buddyinfo except broken down
832by migrate-type and finishes with details on how many page blocks of each
833type exist.
834
835If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
836from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
837make an estimate of the likely number of huge pages that can be allocated
838at a given point in time. All the "Movable" blocks should be allocatable
839unless memory has been mlock()'d. Some of the Reclaimable blocks should
840also be allocatable although a lot of filesystem metadata may have to be
841reclaimed to achieve this.
842
843..............................................................................
844
845meminfo:
846
847Provides information about distribution and utilization of memory. This
848varies by architecture and compile options. The following is from a
84916GB PIII, which has highmem enabled. You may not have all of these fields.
850
851> cat /proc/meminfo
852
853MemTotal: 16344972 kB
854MemFree: 13634064 kB
855MemAvailable: 14836172 kB
856Buffers: 3656 kB
857Cached: 1195708 kB
858SwapCached: 0 kB
859Active: 891636 kB
860Inactive: 1077224 kB
861HighTotal: 15597528 kB
862HighFree: 13629632 kB
863LowTotal: 747444 kB
864LowFree: 4432 kB
865SwapTotal: 0 kB
866SwapFree: 0 kB
867Dirty: 968 kB
868Writeback: 0 kB
869AnonPages: 861800 kB
870Mapped: 280372 kB
871Shmem: 644 kB
872KReclaimable: 168048 kB
873Slab: 284364 kB
874SReclaimable: 159856 kB
875SUnreclaim: 124508 kB
876PageTables: 24448 kB
877NFS_Unstable: 0 kB
878Bounce: 0 kB
879WritebackTmp: 0 kB
880CommitLimit: 7669796 kB
881Committed_AS: 100056 kB
882VmallocTotal: 112216 kB
883VmallocUsed: 428 kB
884VmallocChunk: 111088 kB
885Percpu: 62080 kB
886HardwareCorrupted: 0 kB
887AnonHugePages: 49152 kB
888ShmemHugePages: 0 kB
889ShmemPmdMapped: 0 kB
890
891
892 MemTotal: Total usable ram (i.e. physical ram minus a few reserved
893 bits and the kernel binary code)
894 MemFree: The sum of LowFree+HighFree
895MemAvailable: An estimate of how much memory is available for starting new
896 applications, without swapping. Calculated from MemFree,
897 SReclaimable, the size of the file LRU lists, and the low
898 watermarks in each zone.
899 The estimate takes into account that the system needs some
900 page cache to function well, and that not all reclaimable
901 slab will be reclaimable, due to items being in use. The
902 impact of those factors will vary from system to system.
903 Buffers: Relatively temporary storage for raw disk blocks
904 shouldn't get tremendously large (20MB or so)
905 Cached: in-memory cache for files read from the disk (the
906 pagecache). Doesn't include SwapCached
907 SwapCached: Memory that once was swapped out, is swapped back in but
908 still also is in the swapfile (if memory is needed it
909 doesn't need to be swapped out AGAIN because it is already
910 in the swapfile. This saves I/O)
911 Active: Memory that has been used more recently and usually not
912 reclaimed unless absolutely necessary.
913 Inactive: Memory which has been less recently used. It is more
914 eligible to be reclaimed for other purposes
915 HighTotal:
916 HighFree: Highmem is all memory above ~860MB of physical memory
917 Highmem areas are for use by userspace programs, or
918 for the pagecache. The kernel must use tricks to access
919 this memory, making it slower to access than lowmem.
920 LowTotal:
921 LowFree: Lowmem is memory which can be used for everything that
922 highmem can be used for, but it is also available for the
923 kernel's use for its own data structures. Among many
924 other things, it is where everything from the Slab is
925 allocated. Bad things happen when you're out of lowmem.
926 SwapTotal: total amount of swap space available
927 SwapFree: Memory which has been evicted from RAM, and is temporarily
928 on the disk
929 Dirty: Memory which is waiting to get written back to the disk
930 Writeback: Memory which is actively being written back to the disk
931 AnonPages: Non-file backed pages mapped into userspace page tables
932HardwareCorrupted: The amount of RAM/memory in KB, the kernel identifies as
933 corrupted.
934AnonHugePages: Non-file backed huge pages mapped into userspace page tables
935 Mapped: files which have been mmaped, such as libraries
936 Shmem: Total memory used by shared memory (shmem) and tmpfs
937ShmemHugePages: Memory used by shared memory (shmem) and tmpfs allocated
938 with huge pages
939ShmemPmdMapped: Shared memory mapped into userspace with huge pages
940KReclaimable: Kernel allocations that the kernel will attempt to reclaim
941 under memory pressure. Includes SReclaimable (below), and other
942 direct allocations with a shrinker.
943 Slab: in-kernel data structures cache
944SReclaimable: Part of Slab, that might be reclaimed, such as caches
945 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
946 PageTables: amount of memory dedicated to the lowest level of page
947 tables.
948NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
949 storage
950 Bounce: Memory used for block device "bounce buffers"
951WritebackTmp: Memory used by FUSE for temporary writeback buffers
952 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
953 this is the total amount of memory currently available to
954 be allocated on the system. This limit is only adhered to
955 if strict overcommit accounting is enabled (mode 2 in
956 'vm.overcommit_memory').
957 The CommitLimit is calculated with the following formula:
958 CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
959 overcommit_ratio / 100 + [total swap pages]
960 For example, on a system with 1G of physical RAM and 7G
961 of swap with a `vm.overcommit_ratio` of 30 it would
962 yield a CommitLimit of 7.3G.
963 For more details, see the memory overcommit documentation
964 in vm/overcommit-accounting.
965Committed_AS: The amount of memory presently allocated on the system.
966 The committed memory is a sum of all of the memory which
967 has been allocated by processes, even if it has not been
968 "used" by them as of yet. A process which malloc()'s 1G
969 of memory, but only touches 300M of it will show up as
970 using 1G. This 1G is memory which has been "committed" to
971 by the VM and can be used at any time by the allocating
972 application. With strict overcommit enabled on the system
973 (mode 2 in 'vm.overcommit_memory'),allocations which would
974 exceed the CommitLimit (detailed above) will not be permitted.
975 This is useful if one needs to guarantee that processes will
976 not fail due to lack of memory once that memory has been
977 successfully allocated.
978VmallocTotal: total size of vmalloc memory area
979 VmallocUsed: amount of vmalloc area which is used
980VmallocChunk: largest contiguous block of vmalloc area which is free
981 Percpu: Memory allocated to the percpu allocator used to back percpu
982 allocations. This stat excludes the cost of metadata.
983
984..............................................................................
985
986vmallocinfo:
987
988Provides information about vmalloced/vmaped areas. One line per area,
989containing the virtual address range of the area, size in bytes,
990caller information of the creator, and optional information depending
991on the kind of area :
992
993 pages=nr number of pages
994 phys=addr if a physical address was specified
995 ioremap I/O mapping (ioremap() and friends)
996 vmalloc vmalloc() area
997 vmap vmap()ed pages
998 user VM_USERMAP area
999 vpages buffer for pages pointers was vmalloced (huge area)
1000 N<node>=nr (Only on NUMA kernels)
1001 Number of pages allocated on memory node <node>
1002
1003> cat /proc/vmallocinfo
10040xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
1005 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
10060xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
1007 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
10080xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
1009 phys=7fee8000 ioremap
10100xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
1011 phys=7fee7000 ioremap
10120xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
10130xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
1014 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
10150xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
1016 pages=2 vmalloc N1=2
10170xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
1018 /0x130 [x_tables] pages=4 vmalloc N0=4
10190xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
1020 pages=14 vmalloc N2=14
10210xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
1022 pages=4 vmalloc N1=4
10230xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
1024 pages=2 vmalloc N1=2
10250xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
1026 pages=10 vmalloc N0=10
1027
1028..............................................................................
1029
1030softirqs:
1031
1032Provides counts of softirq handlers serviced since boot time, for each cpu.
1033
1034> cat /proc/softirqs
1035 CPU0 CPU1 CPU2 CPU3
1036 HI: 0 0 0 0
1037 TIMER: 27166 27120 27097 27034
1038 NET_TX: 0 0 0 17
1039 NET_RX: 42 0 0 39
1040 BLOCK: 0 0 107 1121
1041 TASKLET: 0 0 0 290
1042 SCHED: 27035 26983 26971 26746
1043 HRTIMER: 0 0 0 0
1044 RCU: 1678 1769 2178 2250
1045
1046
10471.3 IDE devices in /proc/ide
1048----------------------------
1049
1050The subdirectory /proc/ide contains information about all IDE devices of which
1051the kernel is aware. There is one subdirectory for each IDE controller, the
1052file drivers and a link for each IDE device, pointing to the device directory
1053in the controller specific subtree.
1054
1055The file drivers contains general information about the drivers used for the
1056IDE devices:
1057
1058 > cat /proc/ide/drivers
1059 ide-cdrom version 4.53
1060 ide-disk version 1.08
1061
1062More detailed information can be found in the controller specific
1063subdirectories. These are named ide0, ide1 and so on. Each of these
1064directories contains the files shown in table 1-6.
1065
1066
1067Table 1-6: IDE controller info in /proc/ide/ide?
1068..............................................................................
1069 File Content
1070 channel IDE channel (0 or 1)
1071 config Configuration (only for PCI/IDE bridge)
1072 mate Mate name
1073 model Type/Chipset of IDE controller
1074..............................................................................
1075
1076Each device connected to a controller has a separate subdirectory in the
1077controllers directory. The files listed in table 1-7 are contained in these
1078directories.
1079
1080
1081Table 1-7: IDE device information
1082..............................................................................
1083 File Content
1084 cache The cache
1085 capacity Capacity of the medium (in 512Byte blocks)
1086 driver driver and version
1087 geometry physical and logical geometry
1088 identify device identify block
1089 media media type
1090 model device identifier
1091 settings device setup
1092 smart_thresholds IDE disk management thresholds
1093 smart_values IDE disk management values
1094..............................................................................
1095
1096The most interesting file is settings. This file contains a nice overview of
1097the drive parameters:
1098
1099 # cat /proc/ide/ide0/hda/settings
1100 name value min max mode
1101 ---- ----- --- --- ----
1102 bios_cyl 526 0 65535 rw
1103 bios_head 255 0 255 rw
1104 bios_sect 63 0 63 rw
1105 breada_readahead 4 0 127 rw
1106 bswap 0 0 1 r
1107 file_readahead 72 0 2097151 rw
1108 io_32bit 0 0 3 rw
1109 keepsettings 0 0 1 rw
1110 max_kb_per_request 122 1 127 rw
1111 multcount 0 0 8 rw
1112 nice1 1 0 1 rw
1113 nowerr 0 0 1 rw
1114 pio_mode write-only 0 255 w
1115 slow 0 0 1 rw
1116 unmaskirq 0 0 1 rw
1117 using_dma 0 0 1 rw
1118
1119
11201.4 Networking info in /proc/net
1121--------------------------------
1122
1123The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
1124additional values you get for IP version 6 if you configure the kernel to
1125support this. Table 1-9 lists the files and their meaning.
1126
1127
1128Table 1-8: IPv6 info in /proc/net
1129..............................................................................
1130 File Content
1131 udp6 UDP sockets (IPv6)
1132 tcp6 TCP sockets (IPv6)
1133 raw6 Raw device statistics (IPv6)
1134 igmp6 IP multicast addresses, which this host joined (IPv6)
1135 if_inet6 List of IPv6 interface addresses
1136 ipv6_route Kernel routing table for IPv6
1137 rt6_stats Global IPv6 routing tables statistics
1138 sockstat6 Socket statistics (IPv6)
1139 snmp6 Snmp data (IPv6)
1140..............................................................................
1141
1142
1143Table 1-9: Network info in /proc/net
1144..............................................................................
1145 File Content
1146 arp Kernel ARP table
1147 dev network devices with statistics
1148 dev_mcast the Layer2 multicast groups a device is listening too
1149 (interface index, label, number of references, number of bound
1150 addresses).
1151 dev_stat network device status
1152 ip_fwchains Firewall chain linkage
1153 ip_fwnames Firewall chain names
1154 ip_masq Directory containing the masquerading tables
1155 ip_masquerade Major masquerading table
1156 netstat Network statistics
1157 raw raw device statistics
1158 route Kernel routing table
1159 rpc Directory containing rpc info
1160 rt_cache Routing cache
1161 snmp SNMP data
1162 sockstat Socket statistics
1163 tcp TCP sockets
1164 udp UDP sockets
1165 unix UNIX domain sockets
1166 wireless Wireless interface data (Wavelan etc)
1167 igmp IP multicast addresses, which this host joined
1168 psched Global packet scheduler parameters.
1169 netlink List of PF_NETLINK sockets
1170 ip_mr_vifs List of multicast virtual interfaces
1171 ip_mr_cache List of multicast routing cache
1172..............................................................................
1173
1174You can use this information to see which network devices are available in
1175your system and how much traffic was routed over those devices:
1176
1177 > cat /proc/net/dev
1178 Inter-|Receive |[...
1179 face |bytes packets errs drop fifo frame compressed multicast|[...
1180 lo: 908188 5596 0 0 0 0 0 0 [...
1181 ppp0:15475140 20721 410 0 0 410 0 0 [...
1182 eth0: 614530 7085 0 0 0 0 0 1 [...
1183
1184 ...] Transmit
1185 ...] bytes packets errs drop fifo colls carrier compressed
1186 ...] 908188 5596 0 0 0 0 0 0
1187 ...] 1375103 17405 0 0 0 0 0 0
1188 ...] 1703981 5535 0 0 0 3 0 0
1189
1190In addition, each Channel Bond interface has its own directory. For
1191example, the bond0 device will have a directory called /proc/net/bond0/.
1192It will contain information that is specific to that bond, such as the
1193current slaves of the bond, the link status of the slaves, and how
1194many times the slaves link has failed.
1195
11961.5 SCSI info
1197-------------
1198
1199If you have a SCSI host adapter in your system, you'll find a subdirectory
1200named after the driver for this adapter in /proc/scsi. You'll also see a list
1201of all recognized SCSI devices in /proc/scsi:
1202
1203 >cat /proc/scsi/scsi
1204 Attached devices:
1205 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1206 Vendor: IBM Model: DGHS09U Rev: 03E0
1207 Type: Direct-Access ANSI SCSI revision: 03
1208 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1209 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1210 Type: CD-ROM ANSI SCSI revision: 02
1211
1212
1213The directory named after the driver has one file for each adapter found in
1214the system. These files contain information about the controller, including
1215the used IRQ and the IO address range. The amount of information shown is
1216dependent on the adapter you use. The example shows the output for an Adaptec
1217AHA-2940 SCSI adapter:
1218
1219 > cat /proc/scsi/aic7xxx/0
1220
1221 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1222 Compile Options:
1223 TCQ Enabled By Default : Disabled
1224 AIC7XXX_PROC_STATS : Disabled
1225 AIC7XXX_RESET_DELAY : 5
1226 Adapter Configuration:
1227 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1228 Ultra Wide Controller
1229 PCI MMAPed I/O Base: 0xeb001000
1230 Adapter SEEPROM Config: SEEPROM found and used.
1231 Adaptec SCSI BIOS: Enabled
1232 IRQ: 10
1233 SCBs: Active 0, Max Active 2,
1234 Allocated 15, HW 16, Page 255
1235 Interrupts: 160328
1236 BIOS Control Word: 0x18b6
1237 Adapter Control Word: 0x005b
1238 Extended Translation: Enabled
1239 Disconnect Enable Flags: 0xffff
1240 Ultra Enable Flags: 0x0001
1241 Tag Queue Enable Flags: 0x0000
1242 Ordered Queue Tag Flags: 0x0000
1243 Default Tag Queue Depth: 8
1244 Tagged Queue By Device array for aic7xxx host instance 0:
1245 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1246 Actual queue depth per device for aic7xxx host instance 0:
1247 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1248 Statistics:
1249 (scsi0:0:0:0)
1250 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1251 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1252 Total transfers 160151 (74577 reads and 85574 writes)
1253 (scsi0:0:6:0)
1254 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1255 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1256 Total transfers 0 (0 reads and 0 writes)
1257
1258
12591.6 Parallel port info in /proc/parport
1260---------------------------------------
1261
1262The directory /proc/parport contains information about the parallel ports of
1263your system. It has one subdirectory for each port, named after the port
1264number (0,1,2,...).
1265
1266These directories contain the four files shown in Table 1-10.
1267
1268
1269Table 1-10: Files in /proc/parport
1270..............................................................................
1271 File Content
1272 autoprobe Any IEEE-1284 device ID information that has been acquired.
1273 devices list of the device drivers using that port. A + will appear by the
1274 name of the device currently using the port (it might not appear
1275 against any).
1276 hardware Parallel port's base address, IRQ line and DMA channel.
1277 irq IRQ that parport is using for that port. This is in a separate
1278 file to allow you to alter it by writing a new value in (IRQ
1279 number or none).
1280..............................................................................
1281
12821.7 TTY info in /proc/tty
1283-------------------------
1284
1285Information about the available and actually used tty's can be found in the
1286directory /proc/tty.You'll find entries for drivers and line disciplines in
1287this directory, as shown in Table 1-11.
1288
1289
1290Table 1-11: Files in /proc/tty
1291..............................................................................
1292 File Content
1293 drivers list of drivers and their usage
1294 ldiscs registered line disciplines
1295 driver/serial usage statistic and status of single tty lines
1296..............................................................................
1297
1298To see which tty's are currently in use, you can simply look into the file
1299/proc/tty/drivers:
1300
1301 > cat /proc/tty/drivers
1302 pty_slave /dev/pts 136 0-255 pty:slave
1303 pty_master /dev/ptm 128 0-255 pty:master
1304 pty_slave /dev/ttyp 3 0-255 pty:slave
1305 pty_master /dev/pty 2 0-255 pty:master
1306 serial /dev/cua 5 64-67 serial:callout
1307 serial /dev/ttyS 4 64-67 serial
1308 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1309 /dev/ptmx /dev/ptmx 5 2 system
1310 /dev/console /dev/console 5 1 system:console
1311 /dev/tty /dev/tty 5 0 system:/dev/tty
1312 unknown /dev/tty 4 1-63 console
1313
1314
13151.8 Miscellaneous kernel statistics in /proc/stat
1316-------------------------------------------------
1317
1318Various pieces of information about kernel activity are available in the
1319/proc/stat file. All of the numbers reported in this file are aggregates
1320since the system first booted. For a quick look, simply cat the file:
1321
1322 > cat /proc/stat
1323 cpu 2255 34 2290 22625563 6290 127 456 0 0 0
1324 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1325 cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1326 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1327 ctxt 1990473
1328 btime 1062191376
1329 processes 2915
1330 procs_running 1
1331 procs_blocked 0
1332 softirq 183433 0 21755 12 39 1137 231 21459 2263
1333
1334The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1335lines. These numbers identify the amount of time the CPU has spent performing
1336different kinds of work. Time units are in USER_HZ (typically hundredths of a
1337second). The meanings of the columns are as follows, from left to right:
1338
1339- user: normal processes executing in user mode
1340- nice: niced processes executing in user mode
1341- system: processes executing in kernel mode
1342- idle: twiddling thumbs
1343- iowait: In a word, iowait stands for waiting for I/O to complete. But there
1344 are several problems:
1345 1. Cpu will not wait for I/O to complete, iowait is the time that a task is
1346 waiting for I/O to complete. When cpu goes into idle state for
1347 outstanding task io, another task will be scheduled on this CPU.
1348 2. In a multi-core CPU, the task waiting for I/O to complete is not running
1349 on any CPU, so the iowait of each CPU is difficult to calculate.
1350 3. The value of iowait field in /proc/stat will decrease in certain
1351 conditions.
1352 So, the iowait is not reliable by reading from /proc/stat.
1353- irq: servicing interrupts
1354- softirq: servicing softirqs
1355- steal: involuntary wait
1356- guest: running a normal guest
1357- guest_nice: running a niced guest
1358
1359The "intr" line gives counts of interrupts serviced since boot time, for each
1360of the possible system interrupts. The first column is the total of all
1361interrupts serviced including unnumbered architecture specific interrupts;
1362each subsequent column is the total for that particular numbered interrupt.
1363Unnumbered interrupts are not shown, only summed into the total.
1364
1365The "ctxt" line gives the total number of context switches across all CPUs.
1366
1367The "btime" line gives the time at which the system booted, in seconds since
1368the Unix epoch.
1369
1370The "processes" line gives the number of processes and threads created, which
1371includes (but is not limited to) those created by calls to the fork() and
1372clone() system calls.
1373
1374The "procs_running" line gives the total number of threads that are
1375running or ready to run (i.e., the total number of runnable threads).
1376
1377The "procs_blocked" line gives the number of processes currently blocked,
1378waiting for I/O to complete.
1379
1380The "softirq" line gives counts of softirqs serviced since boot time, for each
1381of the possible system softirqs. The first column is the total of all
1382softirqs serviced; each subsequent column is the total for that particular
1383softirq.
1384
1385
13861.9 Ext4 file system parameters
1387-------------------------------
1388
1389Information about mounted ext4 file systems can be found in
1390/proc/fs/ext4. Each mounted filesystem will have a directory in
1391/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1392/proc/fs/ext4/dm-0). The files in each per-device directory are shown
1393in Table 1-12, below.
1394
1395Table 1-12: Files in /proc/fs/ext4/<devname>
1396..............................................................................
1397 File Content
1398 mb_groups details of multiblock allocator buddy cache of free blocks
1399..............................................................................
1400
14012.0 /proc/consoles
1402------------------
1403Shows registered system console lines.
1404
1405To see which character device lines are currently used for the system console
1406/dev/console, you may simply look into the file /proc/consoles:
1407
1408 > cat /proc/consoles
1409 tty0 -WU (ECp) 4:7
1410 ttyS0 -W- (Ep) 4:64
1411
1412The columns are:
1413
1414 device name of the device
1415 operations R = can do read operations
1416 W = can do write operations
1417 U = can do unblank
1418 flags E = it is enabled
1419 C = it is preferred console
1420 B = it is primary boot console
1421 p = it is used for printk buffer
1422 b = it is not a TTY but a Braille device
1423 a = it is safe to use when cpu is offline
1424 major:minor major and minor number of the device separated by a colon
1425
1426------------------------------------------------------------------------------
1427Summary
1428------------------------------------------------------------------------------
1429The /proc file system serves information about the running system. It not only
1430allows access to process data but also allows you to request the kernel status
1431by reading files in the hierarchy.
1432
1433The directory structure of /proc reflects the types of information and makes
1434it easy, if not obvious, where to look for specific data.
1435------------------------------------------------------------------------------
1436
1437------------------------------------------------------------------------------
1438CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1439------------------------------------------------------------------------------
1440
1441------------------------------------------------------------------------------
1442In This Chapter
1443------------------------------------------------------------------------------
1444* Modifying kernel parameters by writing into files found in /proc/sys
1445* Exploring the files which modify certain parameters
1446* Review of the /proc/sys file tree
1447------------------------------------------------------------------------------
1448
1449
1450A very interesting part of /proc is the directory /proc/sys. This is not only
1451a source of information, it also allows you to change parameters within the
1452kernel. Be very careful when attempting this. You can optimize your system,
1453but you can also cause it to crash. Never alter kernel parameters on a
1454production system. Set up a development machine and test to make sure that
1455everything works the way you want it to. You may have no alternative but to
1456reboot the machine once an error has been made.
1457
1458To change a value, simply echo the new value into the file. An example is
1459given below in the section on the file system data. You need to be root to do
1460this. You can create your own boot script to perform this every time your
1461system boots.
1462
1463The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1464general things in the operation of the Linux kernel. Since some of the files
1465can inadvertently disrupt your system, it is advisable to read both
1466documentation and source before actually making adjustments. In any case, be
1467very careful when writing to any of these files. The entries in /proc may
1468change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1469review the kernel documentation in the directory /usr/src/linux/Documentation.
1470This chapter is heavily based on the documentation included in the pre 2.2
1471kernels, and became part of it in version 2.2.1 of the Linux kernel.
1472
1473Please see: Documentation/sysctl/ directory for descriptions of these
1474entries.
1475
1476------------------------------------------------------------------------------
1477Summary
1478------------------------------------------------------------------------------
1479Certain aspects of kernel behavior can be modified at runtime, without the
1480need to recompile the kernel, or even to reboot the system. The files in the
1481/proc/sys tree can not only be read, but also modified. You can use the echo
1482command to write value into these files, thereby changing the default settings
1483of the kernel.
1484------------------------------------------------------------------------------
1485
1486------------------------------------------------------------------------------
1487CHAPTER 3: PER-PROCESS PARAMETERS
1488------------------------------------------------------------------------------
1489
14903.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1491--------------------------------------------------------------------------------
1492
1493These file can be used to adjust the badness heuristic used to select which
1494process gets killed in out of memory conditions.
1495
1496The badness heuristic assigns a value to each candidate task ranging from 0
1497(never kill) to 1000 (always kill) to determine which process is targeted. The
1498units are roughly a proportion along that range of allowed memory the process
1499may allocate from based on an estimation of its current memory and swap use.
1500For example, if a task is using all allowed memory, its badness score will be
15011000. If it is using half of its allowed memory, its score will be 500.
1502
1503There is an additional factor included in the badness score: the current memory
1504and swap usage is discounted by 3% for root processes.
1505
1506The amount of "allowed" memory depends on the context in which the oom killer
1507was called. If it is due to the memory assigned to the allocating task's cpuset
1508being exhausted, the allowed memory represents the set of mems assigned to that
1509cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1510memory represents the set of mempolicy nodes. If it is due to a memory
1511limit (or swap limit) being reached, the allowed memory is that configured
1512limit. Finally, if it is due to the entire system being out of memory, the
1513allowed memory represents all allocatable resources.
1514
1515The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1516is used to determine which task to kill. Acceptable values range from -1000
1517(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1518polarize the preference for oom killing either by always preferring a certain
1519task or completely disabling it. The lowest possible value, -1000, is
1520equivalent to disabling oom killing entirely for that task since it will always
1521report a badness score of 0.
1522
1523Consequently, it is very simple for userspace to define the amount of memory to
1524consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1525example, is roughly equivalent to allowing the remainder of tasks sharing the
1526same system, cpuset, mempolicy, or memory controller resources to use at least
152750% more memory. A value of -500, on the other hand, would be roughly
1528equivalent to discounting 50% of the task's allowed memory from being considered
1529as scoring against the task.
1530
1531For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1532be used to tune the badness score. Its acceptable values range from -16
1533(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1534(OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1535scaled linearly with /proc/<pid>/oom_score_adj.
1536
1537The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1538value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1539requires CAP_SYS_RESOURCE.
1540
1541Caveat: when a parent task is selected, the oom killer will sacrifice any first
1542generation children with separate address spaces instead, if possible. This
1543avoids servers and important system daemons from being killed and loses the
1544minimal amount of work.
1545
1546
15473.2 /proc/<pid>/oom_score - Display current oom-killer score
1548-------------------------------------------------------------
1549
1550This file can be used to check the current score used by the oom-killer is for
1551any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1552process should be killed in an out-of-memory situation.
1553
1554
15553.3 /proc/<pid>/io - Display the IO accounting fields
1556-------------------------------------------------------
1557
1558This file contains IO statistics for each running process
1559
1560Example
1561-------
1562
1563test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1564[1] 3828
1565
1566test:/tmp # cat /proc/3828/io
1567rchar: 323934931
1568wchar: 323929600
1569syscr: 632687
1570syscw: 632675
1571read_bytes: 0
1572write_bytes: 323932160
1573cancelled_write_bytes: 0
1574
1575
1576Description
1577-----------
1578
1579rchar
1580-----
1581
1582I/O counter: chars read
1583The number of bytes which this task has caused to be read from storage. This
1584is simply the sum of bytes which this process passed to read() and pread().
1585It includes things like tty IO and it is unaffected by whether or not actual
1586physical disk IO was required (the read might have been satisfied from
1587pagecache)
1588
1589
1590wchar
1591-----
1592
1593I/O counter: chars written
1594The number of bytes which this task has caused, or shall cause to be written
1595to disk. Similar caveats apply here as with rchar.
1596
1597
1598syscr
1599-----
1600
1601I/O counter: read syscalls
1602Attempt to count the number of read I/O operations, i.e. syscalls like read()
1603and pread().
1604
1605
1606syscw
1607-----
1608
1609I/O counter: write syscalls
1610Attempt to count the number of write I/O operations, i.e. syscalls like
1611write() and pwrite().
1612
1613
1614read_bytes
1615----------
1616
1617I/O counter: bytes read
1618Attempt to count the number of bytes which this process really did cause to
1619be fetched from the storage layer. Done at the submit_bio() level, so it is
1620accurate for block-backed filesystems. <please add status regarding NFS and
1621CIFS at a later time>
1622
1623
1624write_bytes
1625-----------
1626
1627I/O counter: bytes written
1628Attempt to count the number of bytes which this process caused to be sent to
1629the storage layer. This is done at page-dirtying time.
1630
1631
1632cancelled_write_bytes
1633---------------------
1634
1635The big inaccuracy here is truncate. If a process writes 1MB to a file and
1636then deletes the file, it will in fact perform no writeout. But it will have
1637been accounted as having caused 1MB of write.
1638In other words: The number of bytes which this process caused to not happen,
1639by truncating pagecache. A task can cause "negative" IO too. If this task
1640truncates some dirty pagecache, some IO which another task has been accounted
1641for (in its write_bytes) will not be happening. We _could_ just subtract that
1642from the truncating task's write_bytes, but there is information loss in doing
1643that.
1644
1645
1646Note
1647----
1648
1649At its current implementation state, this is a bit racy on 32-bit machines: if
1650process A reads process B's /proc/pid/io while process B is updating one of
1651those 64-bit counters, process A could see an intermediate result.
1652
1653
1654More information about this can be found within the taskstats documentation in
1655Documentation/accounting.
1656
16573.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1658---------------------------------------------------------------
1659When a process is dumped, all anonymous memory is written to a core file as
1660long as the size of the core file isn't limited. But sometimes we don't want
1661to dump some memory segments, for example, huge shared memory or DAX.
1662Conversely, sometimes we want to save file-backed memory segments into a core
1663file, not only the individual files.
1664
1665/proc/<pid>/coredump_filter allows you to customize which memory segments
1666will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1667of memory types. If a bit of the bitmask is set, memory segments of the
1668corresponding memory type are dumped, otherwise they are not dumped.
1669
1670The following 9 memory types are supported:
1671 - (bit 0) anonymous private memory
1672 - (bit 1) anonymous shared memory
1673 - (bit 2) file-backed private memory
1674 - (bit 3) file-backed shared memory
1675 - (bit 4) ELF header pages in file-backed private memory areas (it is
1676 effective only if the bit 2 is cleared)
1677 - (bit 5) hugetlb private memory
1678 - (bit 6) hugetlb shared memory
1679 - (bit 7) DAX private memory
1680 - (bit 8) DAX shared memory
1681
1682 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1683 are always dumped regardless of the bitmask status.
1684
1685 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
1686 only affected by bit 5-6, and DAX is only affected by bits 7-8.
1687
1688The default value of coredump_filter is 0x33; this means all anonymous memory
1689segments, ELF header pages and hugetlb private memory are dumped.
1690
1691If you don't want to dump all shared memory segments attached to pid 1234,
1692write 0x31 to the process's proc file.
1693
1694 $ echo 0x31 > /proc/1234/coredump_filter
1695
1696When a new process is created, the process inherits the bitmask status from its
1697parent. It is useful to set up coredump_filter before the program runs.
1698For example:
1699
1700 $ echo 0x7 > /proc/self/coredump_filter
1701 $ ./some_program
1702
17033.5 /proc/<pid>/mountinfo - Information about mounts
1704--------------------------------------------------------
1705
1706This file contains lines of the form:
1707
170836 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1709(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1710
1711(1) mount ID: unique identifier of the mount (may be reused after umount)
1712(2) parent ID: ID of parent (or of self for the top of the mount tree)
1713(3) major:minor: value of st_dev for files on filesystem
1714(4) root: root of the mount within the filesystem
1715(5) mount point: mount point relative to the process's root
1716(6) mount options: per mount options
1717(7) optional fields: zero or more fields of the form "tag[:value]"
1718(8) separator: marks the end of the optional fields
1719(9) filesystem type: name of filesystem of the form "type[.subtype]"
1720(10) mount source: filesystem specific information or "none"
1721(11) super options: per super block options
1722
1723Parsers should ignore all unrecognised optional fields. Currently the
1724possible optional fields are:
1725
1726shared:X mount is shared in peer group X
1727master:X mount is slave to peer group X
1728propagate_from:X mount is slave and receives propagation from peer group X (*)
1729unbindable mount is unbindable
1730
1731(*) X is the closest dominant peer group under the process's root. If
1732X is the immediate master of the mount, or if there's no dominant peer
1733group under the same root, then only the "master:X" field is present
1734and not the "propagate_from:X" field.
1735
1736For more information on mount propagation see:
1737
1738 Documentation/filesystems/sharedsubtree.txt
1739
1740
17413.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1742--------------------------------------------------------
1743These files provide a method to access a tasks comm value. It also allows for
1744a task to set its own or one of its thread siblings comm value. The comm value
1745is limited in size compared to the cmdline value, so writing anything longer
1746then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1747comm value.
1748
1749
17503.7 /proc/<pid>/task/<tid>/children - Information about task children
1751-------------------------------------------------------------------------
1752This file provides a fast way to retrieve first level children pids
1753of a task pointed by <pid>/<tid> pair. The format is a space separated
1754stream of pids.
1755
1756Note the "first level" here -- if a child has own children they will
1757not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1758to obtain the descendants.
1759
1760Since this interface is intended to be fast and cheap it doesn't
1761guarantee to provide precise results and some children might be
1762skipped, especially if they've exited right after we printed their
1763pids, so one need to either stop or freeze processes being inspected
1764if precise results are needed.
1765
1766
17673.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
1768---------------------------------------------------------------
1769This file provides information associated with an opened file. The regular
1770files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1771represents the current offset of the opened file in decimal form [see lseek(2)
1772for details], 'flags' denotes the octal O_xxx mask the file has been
1773created with [see open(2) for details] and 'mnt_id' represents mount ID of
1774the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1775for details].
1776
1777A typical output is
1778
1779 pos: 0
1780 flags: 0100002
1781 mnt_id: 19
1782
1783All locks associated with a file descriptor are shown in its fdinfo too.
1784
1785lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF
1786
1787The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1788pair provide additional information particular to the objects they represent.
1789
1790 Eventfd files
1791 ~~~~~~~~~~~~~
1792 pos: 0
1793 flags: 04002
1794 mnt_id: 9
1795 eventfd-count: 5a
1796
1797 where 'eventfd-count' is hex value of a counter.
1798
1799 Signalfd files
1800 ~~~~~~~~~~~~~~
1801 pos: 0
1802 flags: 04002
1803 mnt_id: 9
1804 sigmask: 0000000000000200
1805
1806 where 'sigmask' is hex value of the signal mask associated
1807 with a file.
1808
1809 Epoll files
1810 ~~~~~~~~~~~
1811 pos: 0
1812 flags: 02
1813 mnt_id: 9
1814 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7
1815
1816 where 'tfd' is a target file descriptor number in decimal form,
1817 'events' is events mask being watched and the 'data' is data
1818 associated with a target [see epoll(7) for more details].
1819
1820 The 'pos' is current offset of the target file in decimal form
1821 [see lseek(2)], 'ino' and 'sdev' are inode and device numbers
1822 where target file resides, all in hex format.
1823
1824 Fsnotify files
1825 ~~~~~~~~~~~~~~
1826 For inotify files the format is the following
1827
1828 pos: 0
1829 flags: 02000000
1830 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1831
1832 where 'wd' is a watch descriptor in decimal form, ie a target file
1833 descriptor number, 'ino' and 'sdev' are inode and device where the
1834 target file resides and the 'mask' is the mask of events, all in hex
1835 form [see inotify(7) for more details].
1836
1837 If the kernel was built with exportfs support, the path to the target
1838 file is encoded as a file handle. The file handle is provided by three
1839 fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1840 format.
1841
1842 If the kernel is built without exportfs support the file handle won't be
1843 printed out.
1844
1845 If there is no inotify mark attached yet the 'inotify' line will be omitted.
1846
1847 For fanotify files the format is
1848
1849 pos: 0
1850 flags: 02
1851 mnt_id: 9
1852 fanotify flags:10 event-flags:0
1853 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1854 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1855
1856 where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1857 call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1858 flags associated with mark which are tracked separately from events
1859 mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1860 mask and 'ignored_mask' is the mask of events which are to be ignored.
1861 All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1862 does provide information about flags and mask used in fanotify_mark
1863 call [see fsnotify manpage for details].
1864
1865 While the first three lines are mandatory and always printed, the rest is
1866 optional and may be omitted if no marks created yet.
1867
1868 Timerfd files
1869 ~~~~~~~~~~~~~
1870
1871 pos: 0
1872 flags: 02
1873 mnt_id: 9
1874 clockid: 0
1875 ticks: 0
1876 settime flags: 01
1877 it_value: (0, 49406829)
1878 it_interval: (1, 0)
1879
1880 where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
1881 that have occurred [see timerfd_create(2) for details]. 'settime flags' are
1882 flags in octal form been used to setup the timer [see timerfd_settime(2) for
1883 details]. 'it_value' is remaining time until the timer exiration.
1884 'it_interval' is the interval for the timer. Note the timer might be set up
1885 with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
1886 still exhibits timer's remaining time.
1887
18883.9 /proc/<pid>/map_files - Information about memory mapped files
1889---------------------------------------------------------------------
1890This directory contains symbolic links which represent memory mapped files
1891the process is maintaining. Example output:
1892
1893 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
1894 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
1895 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
1896 | ...
1897 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
1898 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
1899
1900The name of a link represents the virtual memory bounds of a mapping, i.e.
1901vm_area_struct::vm_start-vm_area_struct::vm_end.
1902
1903The main purpose of the map_files is to retrieve a set of memory mapped
1904files in a fast way instead of parsing /proc/<pid>/maps or
1905/proc/<pid>/smaps, both of which contain many more records. At the same
1906time one can open(2) mappings from the listings of two processes and
1907comparing their inode numbers to figure out which anonymous memory areas
1908are actually shared.
1909
19103.10 /proc/<pid>/timerslack_ns - Task timerslack value
1911---------------------------------------------------------
1912This file provides the value of the task's timerslack value in nanoseconds.
1913This value specifies a amount of time that normal timers may be deferred
1914in order to coalesce timers and avoid unnecessary wakeups.
1915
1916This allows a task's interactivity vs power consumption trade off to be
1917adjusted.
1918
1919Writing 0 to the file will set the tasks timerslack to the default value.
1920
1921Valid values are from 0 - ULLONG_MAX
1922
1923An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
1924permissions on the task specified to change its timerslack_ns value.
1925
19263.11 /proc/<pid>/patch_state - Livepatch patch operation state
1927-----------------------------------------------------------------
1928When CONFIG_LIVEPATCH is enabled, this file displays the value of the
1929patch state for the task.
1930
1931A value of '-1' indicates that no patch is in transition.
1932
1933A value of '0' indicates that a patch is in transition and the task is
1934unpatched. If the patch is being enabled, then the task hasn't been
1935patched yet. If the patch is being disabled, then the task has already
1936been unpatched.
1937
1938A value of '1' indicates that a patch is in transition and the task is
1939patched. If the patch is being enabled, then the task has already been
1940patched. If the patch is being disabled, then the task hasn't been
1941unpatched yet.
1942
1943
1944------------------------------------------------------------------------------
1945Configuring procfs
1946------------------------------------------------------------------------------
1947
19484.1 Mount options
1949---------------------
1950
1951The following mount options are supported:
1952
1953 hidepid= Set /proc/<pid>/ access mode.
1954 gid= Set the group authorized to learn processes information.
1955
1956hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1957(default).
1958
1959hidepid=1 means users may not access any /proc/<pid>/ directories but their
1960own. Sensitive files like cmdline, sched*, status are now protected against
1961other users. This makes it impossible to learn whether any user runs
1962specific program (given the program doesn't reveal itself by its behaviour).
1963As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1964poorly written programs passing sensitive information via program arguments are
1965now protected against local eavesdroppers.
1966
1967hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1968users. It doesn't mean that it hides a fact whether a process with a specific
1969pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1970but it hides process' uid and gid, which may be learned by stat()'ing
1971/proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering
1972information about running processes, whether some daemon runs with elevated
1973privileges, whether other user runs some sensitive program, whether other users
1974run any program at all, etc.
1975
1976gid= defines a group authorized to learn processes information otherwise
1977prohibited by hidepid=. If you use some daemon like identd which needs to learn
1978information about processes information, just add identd to this group.