| blob | 38b606991065b3df4f075bb3120dc9e5db09bf71 |
1 .. SPDX-License-Identifier: GPL-2.0
3 ====================
4 The /proc Filesystem
5 ====================
7 ===================== ======================================= ================
8 /proc/sys Terrehon Bowden <terrehon@pacbell.net>, October 7 1999
9 Bodo Bauer <bb@ricochet.net>
10 2.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
11 move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
12 fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009
13 ===================== ======================================= ================
17 .. Table of Contents
19 0 Preface
20 0.1 Introduction/Credits
21 0.2 Legal Stuff
23 1 Collecting System Information
24 1.1 Process-Specific Subdirectories
25 1.2 Kernel data
26 1.3 IDE devices in /proc/ide
27 1.4 Networking info in /proc/net
28 1.5 SCSI info
29 1.6 Parallel port info in /proc/parport
30 1.7 TTY info in /proc/tty
31 1.8 Miscellaneous kernel statistics in /proc/stat
32 1.9 Ext4 file system parameters
34 2 Modifying System Parameters
36 3 Per-Process Parameters
37 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
38 score
39 3.2 /proc/<pid>/oom_score - Display current oom-killer score
40 3.3 /proc/<pid>/io - Display the IO accounting fields
41 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
42 3.5 /proc/<pid>/mountinfo - Information about mounts
43 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
44 3.7 /proc/<pid>/task/<tid>/children - Information about task children
45 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
46 3.9 /proc/<pid>/map_files - Information about memory mapped files
47 3.10 /proc/<pid>/timerslack_ns - Task timerslack value
48 3.11 /proc/<pid>/patch_state - Livepatch patch operation state
49 3.12 /proc/<pid>/arch_status - Task architecture specific information
51 4 Configuring procfs
52 4.1 Mount options
54 Preface
55 =======
57 0.1 Introduction/Credits
58 ------------------------
60 This documentation is part of a soon (or so we hope) to be released book on
61 the SuSE Linux distribution. As there is no complete documentation for the
62 /proc file system and we've used many freely available sources to write these
63 chapters, it seems only fair to give the work back to the Linux community.
64 This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
65 afraid it's still far from complete, but we hope it will be useful. As far as
66 we know, it is the first 'all-in-one' document about the /proc file system. It
67 is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
68 SPARC, AXP, etc., features, you probably won't find what you are looking for.
69 It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
70 additions and patches are welcome and will be added to this document if you
71 mail them to Bodo.
73 We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
74 other people for help compiling this documentation. We'd also like to extend a
75 special thank you to Andi Kleen for documentation, which we relied on heavily
76 to create this document, as well as the additional information he provided.
77 Thanks to everybody else who contributed source or docs to the Linux kernel
78 and helped create a great piece of software... :)
80 If you have any comments, corrections or additions, please don't hesitate to
81 contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
82 document.
84 The latest version of this document is available online at
85 http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
87 If the above direction does not works for you, you could try the kernel
88 mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
89 comandante@zaralinux.com.
91 0.2 Legal Stuff
92 ---------------
94 We don't guarantee the correctness of this document, and if you come to us
95 complaining about how you screwed up your system because of incorrect
96 documentation, we won't feel responsible...
98 Chapter 1: Collecting System Information
99 ========================================
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
109 ------------------------------------------------------------------------------
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).
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.
118 1.1 Process-Specific Subdirectories
119 -----------------------------------
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).
124 The link self points to the process reading the file system. Each process
125 subdirectory has the entries listed in Table 1-1.
127 Note that an open a file descriptor to /proc/<pid> or to any of its
128 contained files or subdirectories does not prevent <pid> being reused
129 for some other process in the event that <pid> exits. Operations on
130 open /proc/<pid> file descriptors corresponding to dead processes
131 never act on any new process that the kernel may, through chance, have
132 also assigned the process ID <pid>. Instead, operations on these FDs
133 usually fail with ESRCH.
135 .. table:: Table 1-1: Process specific entries in /proc
137 ============= ===============================================================
138 File Content
139 ============= ===============================================================
140 clear_refs Clears page referenced bits shown in smaps output
141 cmdline Command line arguments
142 cpu Current and last cpu in which it was executed (2.4)(smp)
143 cwd Link to the current working directory
144 environ Values of environment variables
145 exe Link to the executable of this process
146 fd Directory, which contains all file descriptors
147 maps Memory maps to executables and library files (2.4)
148 mem Memory held by this process
149 root Link to the root directory of this process
150 stat Process status
151 statm Process memory status information
152 status Process status in human readable form
153 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function
154 symbol the task is blocked in - or "0" if not blocked.
155 pagemap Page table
156 stack Report full stack trace, enable via CONFIG_STACKTRACE
157 smaps An extension based on maps, showing the memory consumption of
158 each mapping and flags associated with it
159 smaps_rollup Accumulated smaps stats for all mappings of the process. This
160 can be derived from smaps, but is faster and more convenient
161 numa_maps An extension based on maps, showing the memory locality and
162 binding policy as well as mem usage (in pages) of each mapping.
163 ============= ===============================================================
165 For example, to get the status information of a process, all you have to do is
166 read the file /proc/PID/status::
168 >cat /proc/self/status
169 Name: cat
170 State: R (running)
171 Tgid: 5452
172 Pid: 5452
173 PPid: 743
174 TracerPid: 0 (2.4)
175 Uid: 501 501 501 501
176 Gid: 100 100 100 100
177 FDSize: 256
178 Groups: 100 14 16
179 VmPeak: 5004 kB
180 VmSize: 5004 kB
181 VmLck: 0 kB
182 VmHWM: 476 kB
183 VmRSS: 476 kB
184 RssAnon: 352 kB
185 RssFile: 120 kB
186 RssShmem: 4 kB
187 VmData: 156 kB
188 VmStk: 88 kB
189 VmExe: 68 kB
190 VmLib: 1412 kB
191 VmPTE: 20 kb
192 VmSwap: 0 kB
193 HugetlbPages: 0 kB
194 CoreDumping: 0
195 THP_enabled: 1
196 Threads: 1
197 SigQ: 0/28578
198 SigPnd: 0000000000000000
199 ShdPnd: 0000000000000000
200 SigBlk: 0000000000000000
201 SigIgn: 0000000000000000
202 SigCgt: 0000000000000000
203 CapInh: 00000000fffffeff
204 CapPrm: 0000000000000000
205 CapEff: 0000000000000000
206 CapBnd: ffffffffffffffff
207 CapAmb: 0000000000000000
208 NoNewPrivs: 0
209 Seccomp: 0
210 Speculation_Store_Bypass: thread vulnerable
211 voluntary_ctxt_switches: 0
212 nonvoluntary_ctxt_switches: 1
214 This shows you nearly the same information you would get if you viewed it with
215 the ps command. In fact, ps uses the proc file system to obtain its
216 information. But you get a more detailed view of the process by reading the
217 file /proc/PID/status. It fields are described in table 1-2.
219 The statm file contains more detailed information about the process
220 memory usage. Its seven fields are explained in Table 1-3. The stat file
221 contains details information about the process itself. Its fields are
222 explained in Table 1-4.
224 (for SMP CONFIG users)
226 For making accounting scalable, RSS related information are handled in an
227 asynchronous manner and the value may not be very precise. To see a precise
228 snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
229 It's slow but very precise.
231 .. table:: Table 1-2: Contents of the status files (as of 4.19)
233 ========================== ===================================================
234 Field Content
235 ========================== ===================================================
236 Name filename of the executable
237 Umask file mode creation mask
238 State state (R is running, S is sleeping, D is sleeping
239 in an uninterruptible wait, Z is zombie,
240 T is traced or stopped)
241 Tgid thread group ID
242 Ngid NUMA group ID (0 if none)
243 Pid process id
244 PPid process id of the parent process
245 TracerPid PID of process tracing this process (0 if not)
246 Uid Real, effective, saved set, and file system UIDs
247 Gid Real, effective, saved set, and file system GIDs
248 FDSize number of file descriptor slots currently allocated
249 Groups supplementary group list
250 NStgid descendant namespace thread group ID hierarchy
251 NSpid descendant namespace process ID hierarchy
252 NSpgid descendant namespace process group ID hierarchy
253 NSsid descendant namespace session ID hierarchy
254 VmPeak peak virtual memory size
255 VmSize total program size
256 VmLck locked memory size
257 VmPin pinned memory size
258 VmHWM peak resident set size ("high water mark")
259 VmRSS size of memory portions. It contains the three
260 following parts
261 (VmRSS = RssAnon + RssFile + RssShmem)
262 RssAnon size of resident anonymous memory
263 RssFile size of resident file mappings
264 RssShmem size of resident shmem memory (includes SysV shm,
265 mapping of tmpfs and shared anonymous mappings)
266 VmData size of private data segments
267 VmStk size of stack segments
268 VmExe size of text segment
269 VmLib size of shared library code
270 VmPTE size of page table entries
271 VmSwap amount of swap used by anonymous private data
272 (shmem swap usage is not included)
273 HugetlbPages size of hugetlb memory portions
274 CoreDumping process's memory is currently being dumped
275 (killing the process may lead to a corrupted core)
276 THP_enabled process is allowed to use THP (returns 0 when
277 PR_SET_THP_DISABLE is set on the process
278 Threads number of threads
279 SigQ number of signals queued/max. number for queue
280 SigPnd bitmap of pending signals for the thread
281 ShdPnd bitmap of shared pending signals for the process
282 SigBlk bitmap of blocked signals
283 SigIgn bitmap of ignored signals
284 SigCgt bitmap of caught signals
285 CapInh bitmap of inheritable capabilities
286 CapPrm bitmap of permitted capabilities
287 CapEff bitmap of effective capabilities
288 CapBnd bitmap of capabilities bounding set
289 CapAmb bitmap of ambient capabilities
290 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
291 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
292 Speculation_Store_Bypass speculative store bypass mitigation status
293 Cpus_allowed mask of CPUs on which this process may run
294 Cpus_allowed_list Same as previous, but in "list format"
295 Mems_allowed mask of memory nodes allowed to this process
296 Mems_allowed_list Same as previous, but in "list format"
297 voluntary_ctxt_switches number of voluntary context switches
298 nonvoluntary_ctxt_switches number of non voluntary context switches
299 ========================== ===================================================
302 .. table:: Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
304 ======== =============================== ==============================
305 Field Content
306 ======== =============================== ==============================
307 size total program size (pages) (same as VmSize in status)
308 resident size of memory portions (pages) (same as VmRSS in status)
309 shared number of pages that are shared (i.e. backed by a file, same
310 as RssFile+RssShmem in status)
311 trs number of pages that are 'code' (not including libs; broken,
312 includes data segment)
313 lrs number of pages of library (always 0 on 2.6)
314 drs number of pages of data/stack (including libs; broken,
315 includes library text)
316 dt number of dirty pages (always 0 on 2.6)
317 ======== =============================== ==============================
320 .. table:: Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
322 ============= ===============================================================
323 Field Content
324 ============= ===============================================================
325 pid process id
326 tcomm filename of the executable
327 state state (R is running, S is sleeping, D is sleeping in an
328 uninterruptible wait, Z is zombie, T is traced or stopped)
329 ppid process id of the parent process
330 pgrp pgrp of the process
331 sid session id
332 tty_nr tty the process uses
333 tty_pgrp pgrp of the tty
334 flags task flags
335 min_flt number of minor faults
336 cmin_flt number of minor faults with child's
337 maj_flt number of major faults
338 cmaj_flt number of major faults with child's
339 utime user mode jiffies
340 stime kernel mode jiffies
341 cutime user mode jiffies with child's
342 cstime kernel mode jiffies with child's
343 priority priority level
344 nice nice level
345 num_threads number of threads
346 it_real_value (obsolete, always 0)
347 start_time time the process started after system boot
348 vsize virtual memory size
349 rss resident set memory size
350 rsslim current limit in bytes on the rss
351 start_code address above which program text can run
352 end_code address below which program text can run
353 start_stack address of the start of the main process stack
354 esp current value of ESP
355 eip current value of EIP
356 pending bitmap of pending signals
357 blocked bitmap of blocked signals
358 sigign bitmap of ignored signals
359 sigcatch bitmap of caught signals
360 0 (place holder, used to be the wchan address,
361 use /proc/PID/wchan instead)
362 0 (place holder)
363 0 (place holder)
364 exit_signal signal to send to parent thread on exit
365 task_cpu which CPU the task is scheduled on
366 rt_priority realtime priority
367 policy scheduling policy (man sched_setscheduler)
368 blkio_ticks time spent waiting for block IO
369 gtime guest time of the task in jiffies
370 cgtime guest time of the task children in jiffies
371 start_data address above which program data+bss is placed
372 end_data address below which program data+bss is placed
373 start_brk address above which program heap can be expanded with brk()
374 arg_start address above which program command line is placed
375 arg_end address below which program command line is placed
376 env_start address above which program environment is placed
377 env_end address below which program environment is placed
378 exit_code the thread's exit_code in the form reported by the waitpid
379 system call
380 ============= ===============================================================
382 The /proc/PID/maps file contains the currently mapped memory regions and
383 their access permissions.
385 The format is::
387 address perms offset dev inode pathname
389 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test
390 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
391 0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
392 a7cb1000-a7cb2000 ---p 00000000 00:00 0
393 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
394 a7eb2000-a7eb3000 ---p 00000000 00:00 0
395 a7eb3000-a7ed5000 rw-p 00000000 00:00 0
396 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
397 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
398 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
399 a800b000-a800e000 rw-p 00000000 00:00 0
400 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
401 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
402 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
403 a8024000-a8027000 rw-p 00000000 00:00 0
404 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
405 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
406 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
407 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
408 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
410 where "address" is the address space in the process that it occupies, "perms"
411 is a set of permissions::
413 r = read
414 w = write
415 x = execute
416 s = shared
417 p = private (copy on write)
419 "offset" is the offset into the mapping, "dev" is the device (major:minor), and
420 "inode" is the inode on that device. 0 indicates that no inode is associated
421 with the memory region, as the case would be with BSS (uninitialized data).
422 The "pathname" shows the name associated file for this mapping. If the mapping
423 is not associated with a file:
425 ======= ====================================
426 [heap] the heap of the program
427 [stack] the stack of the main process
428 [vdso] the "virtual dynamic shared object",
429 the kernel system call handler
430 ======= ====================================
432 or if empty, the mapping is anonymous.
434 The /proc/PID/smaps is an extension based on maps, showing the memory
435 consumption for each of the process's mappings. For each mapping (aka Virtual
436 Memory Area, or VMA) there is a series of lines such as the following::
438 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
440 Size: 1084 kB
441 KernelPageSize: 4 kB
442 MMUPageSize: 4 kB
443 Rss: 892 kB
444 Pss: 374 kB
445 Shared_Clean: 892 kB
446 Shared_Dirty: 0 kB
447 Private_Clean: 0 kB
448 Private_Dirty: 0 kB
449 Referenced: 892 kB
450 Anonymous: 0 kB
451 LazyFree: 0 kB
452 AnonHugePages: 0 kB
453 ShmemPmdMapped: 0 kB
454 Shared_Hugetlb: 0 kB
455 Private_Hugetlb: 0 kB
456 Swap: 0 kB
457 SwapPss: 0 kB
458 KernelPageSize: 4 kB
459 MMUPageSize: 4 kB
460 Locked: 0 kB
461 THPeligible: 0
462 VmFlags: rd ex mr mw me dw
464 The first of these lines shows the same information as is displayed for the
465 mapping in /proc/PID/maps. Following lines show the size of the mapping
466 (size); the size of each page allocated when backing a VMA (KernelPageSize),
467 which is usually the same as the size in the page table entries; the page size
468 used by the MMU when backing a VMA (in most cases, the same as KernelPageSize);
469 the amount of the mapping that is currently resident in RAM (RSS); the
470 process' proportional share of this mapping (PSS); and the number of clean and
471 dirty shared and private pages in the mapping.
473 The "proportional set size" (PSS) of a process is the count of pages it has
474 in memory, where each page is divided by the number of processes sharing it.
475 So if a process has 1000 pages all to itself, and 1000 shared with one other
476 process, its PSS will be 1500.
478 Note that even a page which is part of a MAP_SHARED mapping, but has only
479 a single pte mapped, i.e. is currently used by only one process, is accounted
480 as private and not as shared.
482 "Referenced" indicates the amount of memory currently marked as referenced or
483 accessed.
485 "Anonymous" shows the amount of memory that does not belong to any file. Even
486 a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
487 and a page is modified, the file page is replaced by a private anonymous copy.
489 "LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE).
490 The memory isn't freed immediately with madvise(). It's freed in memory
491 pressure if the memory is clean. Please note that the printed value might
492 be lower than the real value due to optimizations used in the current
493 implementation. If this is not desirable please file a bug report.
495 "AnonHugePages" shows the ammount of memory backed by transparent hugepage.
497 "ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by
498 huge pages.
500 "Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
501 hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
502 reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
504 "Swap" shows how much would-be-anonymous memory is also used, but out on swap.
506 For shmem mappings, "Swap" includes also the size of the mapped (and not
507 replaced by copy-on-write) part of the underlying shmem object out on swap.
508 "SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
509 does not take into account swapped out page of underlying shmem objects.
510 "Locked" indicates whether the mapping is locked in memory or not.
511 "THPeligible" indicates whether the mapping is eligible for allocating THP
512 pages - 1 if true, 0 otherwise. It just shows the current status.
514 "VmFlags" field deserves a separate description. This member represents the
515 kernel flags associated with the particular virtual memory area in two letter
516 encoded manner. The codes are the following:
518 == =======================================
519 rd readable
520 wr writeable
521 ex executable
522 sh shared
523 mr may read
524 mw may write
525 me may execute
526 ms may share
527 gd stack segment growns down
528 pf pure PFN range
529 dw disabled write to the mapped file
530 lo pages are locked in memory
531 io memory mapped I/O area
532 sr sequential read advise provided
533 rr random read advise provided
534 dc do not copy area on fork
535 de do not expand area on remapping
536 ac area is accountable
537 nr swap space is not reserved for the area
538 ht area uses huge tlb pages
539 ar architecture specific flag
540 dd do not include area into core dump
541 sd soft dirty flag
542 mm mixed map area
543 hg huge page advise flag
544 nh no huge page advise flag
545 mg mergable advise flag
546 == =======================================
548 Note that there is no guarantee that every flag and associated mnemonic will
549 be present in all further kernel releases. Things get changed, the flags may
550 be vanished or the reverse -- new added. Interpretation of their meaning
551 might change in future as well. So each consumer of these flags has to
552 follow each specific kernel version for the exact semantic.
554 This file is only present if the CONFIG_MMU kernel configuration option is
555 enabled.
557 Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent
558 output can be achieved only in the single read call).
560 This typically manifests when doing partial reads of these files while the
561 memory map is being modified. Despite the races, we do provide the following
562 guarantees:
564 1) The mapped addresses never go backwards, which implies no two
565 regions will ever overlap.
566 2) If there is something at a given vaddr during the entirety of the
567 life of the smaps/maps walk, there will be some output for it.
569 The /proc/PID/smaps_rollup file includes the same fields as /proc/PID/smaps,
570 but their values are the sums of the corresponding values for all mappings of
571 the process. Additionally, it contains these fields:
573 - Pss_Anon
574 - Pss_File
575 - Pss_Shmem
577 They represent the proportional shares of anonymous, file, and shmem pages, as
578 described for smaps above. These fields are omitted in smaps since each
579 mapping identifies the type (anon, file, or shmem) of all pages it contains.
580 Thus all information in smaps_rollup can be derived from smaps, but at a
581 significantly higher cost.
583 The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
584 bits on both physical and virtual pages associated with a process, and the
585 soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst
586 for details).
587 To clear the bits for all the pages associated with the process::
589 > echo 1 > /proc/PID/clear_refs
591 To clear the bits for the anonymous pages associated with the process::
593 > echo 2 > /proc/PID/clear_refs
595 To clear the bits for the file mapped pages associated with the process::
597 > echo 3 > /proc/PID/clear_refs
599 To clear the soft-dirty bit::
601 > echo 4 > /proc/PID/clear_refs
603 To reset the peak resident set size ("high water mark") to the process's
604 current value::
606 > echo 5 > /proc/PID/clear_refs
608 Any other value written to /proc/PID/clear_refs will have no effect.
610 The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
611 using /proc/kpageflags and number of times a page is mapped using
612 /proc/kpagecount. For detailed explanation, see
613 Documentation/admin-guide/mm/pagemap.rst.
615 The /proc/pid/numa_maps is an extension based on maps, showing the memory
616 locality and binding policy, as well as the memory usage (in pages) of
617 each mapping. The output follows a general format where mapping details get
618 summarized separated by blank spaces, one mapping per each file line::
620 address policy mapping details
622 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
623 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
624 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
625 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
626 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
627 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
628 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
629 320698b000 default file=/lib64/libc-2.12.so
630 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
631 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
632 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
633 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
634 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
635 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
636 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
637 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
639 Where:
641 "address" is the starting address for the mapping;
643 "policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst);
645 "mapping details" summarizes mapping data such as mapping type, page usage counters,
646 node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
647 size, in KB, that is backing the mapping up.
649 1.2 Kernel data
650 ---------------
652 Similar to the process entries, the kernel data files give information about
653 the running kernel. The files used to obtain this information are contained in
654 /proc and are listed in Table 1-5. Not all of these will be present in your
655 system. It depends on the kernel configuration and the loaded modules, which
656 files are there, and which are missing.
658 .. table:: Table 1-5: Kernel info in /proc
660 ============ ===============================================================
661 File Content
662 ============ ===============================================================
663 apm Advanced power management info
664 buddyinfo Kernel memory allocator information (see text) (2.5)
665 bus Directory containing bus specific information
666 cmdline Kernel command line
667 cpuinfo Info about the CPU
668 devices Available devices (block and character)
669 dma Used DMS channels
670 filesystems Supported filesystems
671 driver Various drivers grouped here, currently rtc (2.4)
672 execdomains Execdomains, related to security (2.4)
673 fb Frame Buffer devices (2.4)
674 fs File system parameters, currently nfs/exports (2.4)
675 ide Directory containing info about the IDE subsystem
676 interrupts Interrupt usage
677 iomem Memory map (2.4)
678 ioports I/O port usage
679 irq Masks for irq to cpu affinity (2.4)(smp?)
680 isapnp ISA PnP (Plug&Play) Info (2.4)
681 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
682 kmsg Kernel messages
683 ksyms Kernel symbol table
684 loadavg Load average of last 1, 5 & 15 minutes
685 locks Kernel locks
686 meminfo Memory info
687 misc Miscellaneous
688 modules List of loaded modules
689 mounts Mounted filesystems
690 net Networking info (see text)
691 pagetypeinfo Additional page allocator information (see text) (2.5)
692 partitions Table of partitions known to the system
693 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
694 decoupled by lspci (2.4)
695 rtc Real time clock
696 scsi SCSI info (see text)
697 slabinfo Slab pool info
698 softirqs softirq usage
699 stat Overall statistics
700 swaps Swap space utilization
701 sys See chapter 2
702 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
703 tty Info of tty drivers
704 uptime Wall clock since boot, combined idle time of all cpus
705 version Kernel version
706 video bttv info of video resources (2.4)
707 vmallocinfo Show vmalloced areas
708 ============ ===============================================================
710 You can, for example, check which interrupts are currently in use and what
711 they are used for by looking in the file /proc/interrupts::
713 > cat /proc/interrupts
714 CPU0
715 0: 8728810 XT-PIC timer
716 1: 895 XT-PIC keyboard
717 2: 0 XT-PIC cascade
718 3: 531695 XT-PIC aha152x
719 4: 2014133 XT-PIC serial
720 5: 44401 XT-PIC pcnet_cs
721 8: 2 XT-PIC rtc
722 11: 8 XT-PIC i82365
723 12: 182918 XT-PIC PS/2 Mouse
724 13: 1 XT-PIC fpu
725 14: 1232265 XT-PIC ide0
726 15: 7 XT-PIC ide1
727 NMI: 0
729 In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
730 output of a SMP machine)::
732 > cat /proc/interrupts
734 CPU0 CPU1
735 0: 1243498 1214548 IO-APIC-edge timer
736 1: 8949 8958 IO-APIC-edge keyboard
737 2: 0 0 XT-PIC cascade
738 5: 11286 10161 IO-APIC-edge soundblaster
739 8: 1 0 IO-APIC-edge rtc
740 9: 27422 27407 IO-APIC-edge 3c503
741 12: 113645 113873 IO-APIC-edge PS/2 Mouse
742 13: 0 0 XT-PIC fpu
743 14: 22491 24012 IO-APIC-edge ide0
744 15: 2183 2415 IO-APIC-edge ide1
745 17: 30564 30414 IO-APIC-level eth0
746 18: 177 164 IO-APIC-level bttv
747 NMI: 2457961 2457959
748 LOC: 2457882 2457881
749 ERR: 2155
751 NMI is incremented in this case because every timer interrupt generates a NMI
752 (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
754 LOC is the local interrupt counter of the internal APIC of every CPU.
756 ERR is incremented in the case of errors in the IO-APIC bus (the bus that
757 connects the CPUs in a SMP system. This means that an error has been detected,
758 the IO-APIC automatically retry the transmission, so it should not be a big
759 problem, but you should read the SMP-FAQ.
761 In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
762 /proc/interrupts to display every IRQ vector in use by the system, not
763 just those considered 'most important'. The new vectors are:
765 THR
766 interrupt raised when a machine check threshold counter
767 (typically counting ECC corrected errors of memory or cache) exceeds
768 a configurable threshold. Only available on some systems.
770 TRM
771 a thermal event interrupt occurs when a temperature threshold
772 has been exceeded for the CPU. This interrupt may also be generated
773 when the temperature drops back to normal.
775 SPU
776 a spurious interrupt is some interrupt that was raised then lowered
777 by some IO device before it could be fully processed by the APIC. Hence
778 the APIC sees the interrupt but does not know what device it came from.
779 For this case the APIC will generate the interrupt with a IRQ vector
780 of 0xff. This might also be generated by chipset bugs.
782 RES, CAL, TLB]
783 rescheduling, call and TLB flush interrupts are
784 sent from one CPU to another per the needs of the OS. Typically,
785 their statistics are used by kernel developers and interested users to
786 determine the occurrence of interrupts of the given type.
788 The above IRQ vectors are displayed only when relevant. For example,
789 the threshold vector does not exist on x86_64 platforms. Others are
790 suppressed when the system is a uniprocessor. As of this writing, only
791 i386 and x86_64 platforms support the new IRQ vector displays.
793 Of some interest is the introduction of the /proc/irq directory to 2.4.
794 It could be used to set IRQ to CPU affinity, this means that you can "hook" an
795 IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
796 irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
797 prof_cpu_mask.
799 For example::
801 > ls /proc/irq/
802 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
803 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
804 > ls /proc/irq/0/
805 smp_affinity
807 smp_affinity is a bitmask, in which you can specify which CPUs can handle the
808 IRQ, you can set it by doing::
810 > echo 1 > /proc/irq/10/smp_affinity
812 This means that only the first CPU will handle the IRQ, but you can also echo
813 5 which means that only the first and third CPU can handle the IRQ.
815 The contents of each smp_affinity file is the same by default::
817 > cat /proc/irq/0/smp_affinity
818 ffffffff
820 There is an alternate interface, smp_affinity_list which allows specifying
821 a cpu range instead of a bitmask::
823 > cat /proc/irq/0/smp_affinity_list
824 1024-1031
826 The default_smp_affinity mask applies to all non-active IRQs, which are the
827 IRQs which have not yet been allocated/activated, and hence which lack a
828 /proc/irq/[0-9]* directory.
830 The node file on an SMP system shows the node to which the device using the IRQ
831 reports itself as being attached. This hardware locality information does not
832 include information about any possible driver locality preference.
834 prof_cpu_mask specifies which CPUs are to be profiled by the system wide
835 profiler. Default value is ffffffff (all cpus if there are only 32 of them).
837 The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
838 between all the CPUs which are allowed to handle it. As usual the kernel has
839 more info than you and does a better job than you, so the defaults are the
840 best choice for almost everyone. [Note this applies only to those IO-APIC's
841 that support "Round Robin" interrupt distribution.]
843 There are three more important subdirectories in /proc: net, scsi, and sys.
844 The general rule is that the contents, or even the existence of these
845 directories, depend on your kernel configuration. If SCSI is not enabled, the
846 directory scsi may not exist. The same is true with the net, which is there
847 only when networking support is present in the running kernel.
849 The slabinfo file gives information about memory usage at the slab level.
850 Linux uses slab pools for memory management above page level in version 2.2.
851 Commonly used objects have their own slab pool (such as network buffers,
852 directory cache, and so on).
854 ::
856 > cat /proc/buddyinfo
858 Node 0, zone DMA 0 4 5 4 4 3 ...
859 Node 0, zone Normal 1 0 0 1 101 8 ...
860 Node 0, zone HighMem 2 0 0 1 1 0 ...
862 External fragmentation is a problem under some workloads, and buddyinfo is a
863 useful tool for helping diagnose these problems. Buddyinfo will give you a
864 clue as to how big an area you can safely allocate, or why a previous
865 allocation failed.
867 Each column represents the number of pages of a certain order which are
868 available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
869 ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
870 available in ZONE_NORMAL, etc...
872 More information relevant to external fragmentation can be found in
873 pagetypeinfo::
875 > cat /proc/pagetypeinfo
876 Page block order: 9
877 Pages per block: 512
879 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
880 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
881 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
882 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
883 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
884 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
885 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
886 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
887 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
888 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
889 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
891 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
892 Node 0, zone DMA 2 0 5 1 0
893 Node 0, zone DMA32 41 6 967 2 0
895 Fragmentation avoidance in the kernel works by grouping pages of different
896 migrate types into the same contiguous regions of memory called page blocks.
897 A page block is typically the size of the default hugepage size e.g. 2MB on
898 X86-64. By keeping pages grouped based on their ability to move, the kernel
899 can reclaim pages within a page block to satisfy a high-order allocation.
901 The pagetypinfo begins with information on the size of a page block. It
902 then gives the same type of information as buddyinfo except broken down
903 by migrate-type and finishes with details on how many page blocks of each
904 type exist.
906 If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
907 from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
908 make an estimate of the likely number of huge pages that can be allocated
909 at a given point in time. All the "Movable" blocks should be allocatable
910 unless memory has been mlock()'d. Some of the Reclaimable blocks should
911 also be allocatable although a lot of filesystem metadata may have to be
912 reclaimed to achieve this.
915 meminfo
916 ~~~~~~~
918 Provides information about distribution and utilization of memory. This
919 varies by architecture and compile options. The following is from a
920 16GB PIII, which has highmem enabled. You may not have all of these fields.
922 ::
924 > cat /proc/meminfo
926 MemTotal: 16344972 kB
927 MemFree: 13634064 kB
928 MemAvailable: 14836172 kB
929 Buffers: 3656 kB
930 Cached: 1195708 kB
931 SwapCached: 0 kB
932 Active: 891636 kB
933 Inactive: 1077224 kB
934 HighTotal: 15597528 kB
935 HighFree: 13629632 kB
936 LowTotal: 747444 kB
937 LowFree: 4432 kB
938 SwapTotal: 0 kB
939 SwapFree: 0 kB
940 Dirty: 968 kB
941 Writeback: 0 kB
942 AnonPages: 861800 kB
943 Mapped: 280372 kB
944 Shmem: 644 kB
945 KReclaimable: 168048 kB
946 Slab: 284364 kB
947 SReclaimable: 159856 kB
948 SUnreclaim: 124508 kB
949 PageTables: 24448 kB
950 NFS_Unstable: 0 kB
951 Bounce: 0 kB
952 WritebackTmp: 0 kB
953 CommitLimit: 7669796 kB
954 Committed_AS: 100056 kB
955 VmallocTotal: 112216 kB
956 VmallocUsed: 428 kB
957 VmallocChunk: 111088 kB
958 Percpu: 62080 kB
959 HardwareCorrupted: 0 kB
960 AnonHugePages: 49152 kB
961 ShmemHugePages: 0 kB
962 ShmemPmdMapped: 0 kB
964 MemTotal
965 Total usable ram (i.e. physical ram minus a few reserved
966 bits and the kernel binary code)
967 MemFree
968 The sum of LowFree+HighFree
969 MemAvailable
970 An estimate of how much memory is available for starting new
971 applications, without swapping. Calculated from MemFree,
972 SReclaimable, the size of the file LRU lists, and the low
973 watermarks in each zone.
974 The estimate takes into account that the system needs some
975 page cache to function well, and that not all reclaimable
976 slab will be reclaimable, due to items being in use. The
977 impact of those factors will vary from system to system.
978 Buffers
979 Relatively temporary storage for raw disk blocks
980 shouldn't get tremendously large (20MB or so)
981 Cached
982 in-memory cache for files read from the disk (the
983 pagecache). Doesn't include SwapCached
984 SwapCached
985 Memory that once was swapped out, is swapped back in but
986 still also is in the swapfile (if memory is needed it
987 doesn't need to be swapped out AGAIN because it is already
988 in the swapfile. This saves I/O)
989 Active
990 Memory that has been used more recently and usually not
991 reclaimed unless absolutely necessary.
992 Inactive
993 Memory which has been less recently used. It is more
994 eligible to be reclaimed for other purposes
995 HighTotal, HighFree
996 Highmem is all memory above ~860MB of physical memory
997 Highmem areas are for use by userspace programs, or
998 for the pagecache. The kernel must use tricks to access
999 this memory, making it slower to access than lowmem.
1000 LowTotal, LowFree
1001 Lowmem is memory which can be used for everything that
1002 highmem can be used for, but it is also available for the
1003 kernel's use for its own data structures. Among many
1004 other things, it is where everything from the Slab is
1005 allocated. Bad things happen when you're out of lowmem.
1006 SwapTotal
1007 total amount of swap space available
1008 SwapFree
1009 Memory which has been evicted from RAM, and is temporarily
1010 on the disk
1011 Dirty
1012 Memory which is waiting to get written back to the disk
1013 Writeback
1014 Memory which is actively being written back to the disk
1015 AnonPages
1016 Non-file backed pages mapped into userspace page tables
1017 HardwareCorrupted
1018 The amount of RAM/memory in KB, the kernel identifies as
1019 corrupted.
1020 AnonHugePages
1021 Non-file backed huge pages mapped into userspace page tables
1022 Mapped
1023 files which have been mmaped, such as libraries
1024 Shmem
1025 Total memory used by shared memory (shmem) and tmpfs
1026 ShmemHugePages
1027 Memory used by shared memory (shmem) and tmpfs allocated
1028 with huge pages
1029 ShmemPmdMapped
1030 Shared memory mapped into userspace with huge pages
1031 KReclaimable
1032 Kernel allocations that the kernel will attempt to reclaim
1033 under memory pressure. Includes SReclaimable (below), and other
1034 direct allocations with a shrinker.
1035 Slab
1036 in-kernel data structures cache
1037 SReclaimable
1038 Part of Slab, that might be reclaimed, such as caches
1039 SUnreclaim
1040 Part of Slab, that cannot be reclaimed on memory pressure
1041 PageTables
1042 amount of memory dedicated to the lowest level of page
1043 tables.
1044 NFS_Unstable
1045 NFS pages sent to the server, but not yet committed to stable
1046 storage
1047 Bounce
1048 Memory used for block device "bounce buffers"
1049 WritebackTmp
1050 Memory used by FUSE for temporary writeback buffers
1051 CommitLimit
1052 Based on the overcommit ratio ('vm.overcommit_ratio'),
1053 this is the total amount of memory currently available to
1054 be allocated on the system. This limit is only adhered to
1055 if strict overcommit accounting is enabled (mode 2 in
1056 'vm.overcommit_memory').
1058 The CommitLimit is calculated with the following formula::
1060 CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
1061 overcommit_ratio / 100 + [total swap pages]
1063 For example, on a system with 1G of physical RAM and 7G
1064 of swap with a `vm.overcommit_ratio` of 30 it would
1065 yield a CommitLimit of 7.3G.
1067 For more details, see the memory overcommit documentation
1068 in vm/overcommit-accounting.
1069 Committed_AS
1070 The amount of memory presently allocated on the system.
1071 The committed memory is a sum of all of the memory which
1072 has been allocated by processes, even if it has not been
1073 "used" by them as of yet. A process which malloc()'s 1G
1074 of memory, but only touches 300M of it will show up as
1075 using 1G. This 1G is memory which has been "committed" to
1076 by the VM and can be used at any time by the allocating
1077 application. With strict overcommit enabled on the system
1078 (mode 2 in 'vm.overcommit_memory'),allocations which would
1079 exceed the CommitLimit (detailed above) will not be permitted.
1080 This is useful if one needs to guarantee that processes will
1081 not fail due to lack of memory once that memory has been
1082 successfully allocated.
1083 VmallocTotal
1084 total size of vmalloc memory area
1085 VmallocUsed
1086 amount of vmalloc area which is used
1087 VmallocChunk
1088 largest contiguous block of vmalloc area which is free
1089 Percpu
1090 Memory allocated to the percpu allocator used to back percpu
1091 allocations. This stat excludes the cost of metadata.
1093 vmallocinfo
1094 ~~~~~~~~~~~
1096 Provides information about vmalloced/vmaped areas. One line per area,
1097 containing the virtual address range of the area, size in bytes,
1098 caller information of the creator, and optional information depending
1099 on the kind of area :
1101 ========== ===================================================
1102 pages=nr number of pages
1103 phys=addr if a physical address was specified
1104 ioremap I/O mapping (ioremap() and friends)
1105 vmalloc vmalloc() area
1106 vmap vmap()ed pages
1107 user VM_USERMAP area
1108 vpages buffer for pages pointers was vmalloced (huge area)
1109 N<node>=nr (Only on NUMA kernels)
1110 Number of pages allocated on memory node <node>
1111 ========== ===================================================
1113 ::
1115 > cat /proc/vmallocinfo
1116 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
1117 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
1118 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
1119 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
1120 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
1121 phys=7fee8000 ioremap
1122 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
1123 phys=7fee7000 ioremap
1124 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
1125 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
1126 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
1127 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
1128 pages=2 vmalloc N1=2
1129 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
1130 /0x130 [x_tables] pages=4 vmalloc N0=4
1131 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
1132 pages=14 vmalloc N2=14
1133 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
1134 pages=4 vmalloc N1=4
1135 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
1136 pages=2 vmalloc N1=2
1137 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
1138 pages=10 vmalloc N0=10
1141 softirqs
1142 ~~~~~~~~
1144 Provides counts of softirq handlers serviced since boot time, for each cpu.
1146 ::
1148 > cat /proc/softirqs
1149 CPU0 CPU1 CPU2 CPU3
1150 HI: 0 0 0 0
1151 TIMER: 27166 27120 27097 27034
1152 NET_TX: 0 0 0 17
1153 NET_RX: 42 0 0 39
1154 BLOCK: 0 0 107 1121
1155 TASKLET: 0 0 0 290
1156 SCHED: 27035 26983 26971 26746
1157 HRTIMER: 0 0 0 0
1158 RCU: 1678 1769 2178 2250
1161 1.3 IDE devices in /proc/ide
1162 ----------------------------
1164 The subdirectory /proc/ide contains information about all IDE devices of which
1165 the kernel is aware. There is one subdirectory for each IDE controller, the
1166 file drivers and a link for each IDE device, pointing to the device directory
1167 in the controller specific subtree.
1169 The file drivers contains general information about the drivers used for the
1170 IDE devices::
1172 > cat /proc/ide/drivers
1173 ide-cdrom version 4.53
1174 ide-disk version 1.08
1176 More detailed information can be found in the controller specific
1177 subdirectories. These are named ide0, ide1 and so on. Each of these
1178 directories contains the files shown in table 1-6.
1181 .. table:: Table 1-6: IDE controller info in /proc/ide/ide?
1183 ======= =======================================
1184 File Content
1185 ======= =======================================
1186 channel IDE channel (0 or 1)
1187 config Configuration (only for PCI/IDE bridge)
1188 mate Mate name
1189 model Type/Chipset of IDE controller
1190 ======= =======================================
1192 Each device connected to a controller has a separate subdirectory in the
1193 controllers directory. The files listed in table 1-7 are contained in these
1194 directories.
1197 .. table:: Table 1-7: IDE device information
1199 ================ ==========================================
1200 File Content
1201 ================ ==========================================
1202 cache The cache
1203 capacity Capacity of the medium (in 512Byte blocks)
1204 driver driver and version
1205 geometry physical and logical geometry
1206 identify device identify block
1207 media media type
1208 model device identifier
1209 settings device setup
1210 smart_thresholds IDE disk management thresholds
1211 smart_values IDE disk management values
1212 ================ ==========================================
1214 The most interesting file is ``settings``. This file contains a nice
1215 overview of the drive parameters::
1217 # cat /proc/ide/ide0/hda/settings
1218 name value min max mode
1219 ---- ----- --- --- ----
1220 bios_cyl 526 0 65535 rw
1221 bios_head 255 0 255 rw
1222 bios_sect 63 0 63 rw
1223 breada_readahead 4 0 127 rw
1224 bswap 0 0 1 r
1225 file_readahead 72 0 2097151 rw
1226 io_32bit 0 0 3 rw
1227 keepsettings 0 0 1 rw
1228 max_kb_per_request 122 1 127 rw
1229 multcount 0 0 8 rw
1230 nice1 1 0 1 rw
1231 nowerr 0 0 1 rw
1232 pio_mode write-only 0 255 w
1233 slow 0 0 1 rw
1234 unmaskirq 0 0 1 rw
1235 using_dma 0 0 1 rw
1238 1.4 Networking info in /proc/net
1239 --------------------------------
1241 The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
1242 additional values you get for IP version 6 if you configure the kernel to
1243 support this. Table 1-9 lists the files and their meaning.
1246 .. table:: Table 1-8: IPv6 info in /proc/net
1248 ========== =====================================================
1249 File Content
1250 ========== =====================================================
1251 udp6 UDP sockets (IPv6)
1252 tcp6 TCP sockets (IPv6)
1253 raw6 Raw device statistics (IPv6)
1254 igmp6 IP multicast addresses, which this host joined (IPv6)
1255 if_inet6 List of IPv6 interface addresses
1256 ipv6_route Kernel routing table for IPv6
1257 rt6_stats Global IPv6 routing tables statistics
1258 sockstat6 Socket statistics (IPv6)
1259 snmp6 Snmp data (IPv6)
1260 ========== =====================================================
1262 .. table:: Table 1-9: Network info in /proc/net
1264 ============= ================================================================
1265 File Content
1266 ============= ================================================================
1267 arp Kernel ARP table
1268 dev network devices with statistics
1269 dev_mcast the Layer2 multicast groups a device is listening too
1270 (interface index, label, number of references, number of bound
1271 addresses).
1272 dev_stat network device status
1273 ip_fwchains Firewall chain linkage
1274 ip_fwnames Firewall chain names
1275 ip_masq Directory containing the masquerading tables
1276 ip_masquerade Major masquerading table
1277 netstat Network statistics
1278 raw raw device statistics
1279 route Kernel routing table
1280 rpc Directory containing rpc info
1281 rt_cache Routing cache
1282 snmp SNMP data
1283 sockstat Socket statistics
1284 tcp TCP sockets
1285 udp UDP sockets
1286 unix UNIX domain sockets
1287 wireless Wireless interface data (Wavelan etc)
1288 igmp IP multicast addresses, which this host joined
1289 psched Global packet scheduler parameters.
1290 netlink List of PF_NETLINK sockets
1291 ip_mr_vifs List of multicast virtual interfaces
1292 ip_mr_cache List of multicast routing cache
1293 ============= ================================================================
1295 You can use this information to see which network devices are available in
1296 your system and how much traffic was routed over those devices::
1298 > cat /proc/net/dev
1299 Inter-|Receive |[...
1300 face |bytes packets errs drop fifo frame compressed multicast|[...
1301 lo: 908188 5596 0 0 0 0 0 0 [...
1302 ppp0:15475140 20721 410 0 0 410 0 0 [...
1303 eth0: 614530 7085 0 0 0 0 0 1 [...
1305 ...] Transmit
1306 ...] bytes packets errs drop fifo colls carrier compressed
1307 ...] 908188 5596 0 0 0 0 0 0
1308 ...] 1375103 17405 0 0 0 0 0 0
1309 ...] 1703981 5535 0 0 0 3 0 0
1311 In addition, each Channel Bond interface has its own directory. For
1312 example, the bond0 device will have a directory called /proc/net/bond0/.
1313 It will contain information that is specific to that bond, such as the
1314 current slaves of the bond, the link status of the slaves, and how
1315 many times the slaves link has failed.
1317 1.5 SCSI info
1318 -------------
1320 If you have a SCSI host adapter in your system, you'll find a subdirectory
1321 named after the driver for this adapter in /proc/scsi. You'll also see a list
1322 of all recognized SCSI devices in /proc/scsi::
1324 >cat /proc/scsi/scsi
1325 Attached devices:
1326 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1327 Vendor: IBM Model: DGHS09U Rev: 03E0
1328 Type: Direct-Access ANSI SCSI revision: 03
1329 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1330 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1331 Type: CD-ROM ANSI SCSI revision: 02
1334 The directory named after the driver has one file for each adapter found in
1335 the system. These files contain information about the controller, including
1336 the used IRQ and the IO address range. The amount of information shown is
1337 dependent on the adapter you use. The example shows the output for an Adaptec
1338 AHA-2940 SCSI adapter::
1340 > cat /proc/scsi/aic7xxx/0
1342 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1343 Compile Options:
1344 TCQ Enabled By Default : Disabled
1345 AIC7XXX_PROC_STATS : Disabled
1346 AIC7XXX_RESET_DELAY : 5
1347 Adapter Configuration:
1348 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1349 Ultra Wide Controller
1350 PCI MMAPed I/O Base: 0xeb001000
1351 Adapter SEEPROM Config: SEEPROM found and used.
1352 Adaptec SCSI BIOS: Enabled
1353 IRQ: 10
1354 SCBs: Active 0, Max Active 2,
1355 Allocated 15, HW 16, Page 255
1356 Interrupts: 160328
1357 BIOS Control Word: 0x18b6
1358 Adapter Control Word: 0x005b
1359 Extended Translation: Enabled
1360 Disconnect Enable Flags: 0xffff
1361 Ultra Enable Flags: 0x0001
1362 Tag Queue Enable Flags: 0x0000
1363 Ordered Queue Tag Flags: 0x0000
1364 Default Tag Queue Depth: 8
1365 Tagged Queue By Device array for aic7xxx host instance 0:
1366 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1367 Actual queue depth per device for aic7xxx host instance 0:
1368 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1369 Statistics:
1370 (scsi0:0:0:0)
1371 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1372 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1373 Total transfers 160151 (74577 reads and 85574 writes)
1374 (scsi0:0:6:0)
1375 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1376 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1377 Total transfers 0 (0 reads and 0 writes)
1380 1.6 Parallel port info in /proc/parport
1381 ---------------------------------------
1383 The directory /proc/parport contains information about the parallel ports of
1384 your system. It has one subdirectory for each port, named after the port
1385 number (0,1,2,...).
1387 These directories contain the four files shown in Table 1-10.
1390 .. table:: Table 1-10: Files in /proc/parport
1392 ========= ====================================================================
1393 File Content
1394 ========= ====================================================================
1395 autoprobe Any IEEE-1284 device ID information that has been acquired.
1396 devices list of the device drivers using that port. A + will appear by the
1397 name of the device currently using the port (it might not appear
1398 against any).
1399 hardware Parallel port's base address, IRQ line and DMA channel.
1400 irq IRQ that parport is using for that port. This is in a separate
1401 file to allow you to alter it by writing a new value in (IRQ
1402 number or none).
1403 ========= ====================================================================
1405 1.7 TTY info in /proc/tty
1406 -------------------------
1408 Information about the available and actually used tty's can be found in the
1409 directory /proc/tty.You'll find entries for drivers and line disciplines in
1410 this directory, as shown in Table 1-11.
1413 .. table:: Table 1-11: Files in /proc/tty
1415 ============= ==============================================
1416 File Content
1417 ============= ==============================================
1418 drivers list of drivers and their usage
1419 ldiscs registered line disciplines
1420 driver/serial usage statistic and status of single tty lines
1421 ============= ==============================================
1423 To see which tty's are currently in use, you can simply look into the file
1424 /proc/tty/drivers::
1426 > cat /proc/tty/drivers
1427 pty_slave /dev/pts 136 0-255 pty:slave
1428 pty_master /dev/ptm 128 0-255 pty:master
1429 pty_slave /dev/ttyp 3 0-255 pty:slave
1430 pty_master /dev/pty 2 0-255 pty:master
1431 serial /dev/cua 5 64-67 serial:callout
1432 serial /dev/ttyS 4 64-67 serial
1433 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1434 /dev/ptmx /dev/ptmx 5 2 system
1435 /dev/console /dev/console 5 1 system:console
1436 /dev/tty /dev/tty 5 0 system:/dev/tty
1437 unknown /dev/tty 4 1-63 console
1440 1.8 Miscellaneous kernel statistics in /proc/stat
1441 -------------------------------------------------
1443 Various pieces of information about kernel activity are available in the
1444 /proc/stat file. All of the numbers reported in this file are aggregates
1445 since the system first booted. For a quick look, simply cat the file::
1447 > cat /proc/stat
1448 cpu 2255 34 2290 22625563 6290 127 456 0 0 0
1449 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1450 cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1451 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1452 ctxt 1990473
1453 btime 1062191376
1454 processes 2915
1455 procs_running 1
1456 procs_blocked 0
1457 softirq 183433 0 21755 12 39 1137 231 21459 2263
1459 The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1460 lines. These numbers identify the amount of time the CPU has spent performing
1461 different kinds of work. Time units are in USER_HZ (typically hundredths of a
1462 second). The meanings of the columns are as follows, from left to right:
1464 - user: normal processes executing in user mode
1465 - nice: niced processes executing in user mode
1466 - system: processes executing in kernel mode
1467 - idle: twiddling thumbs
1468 - iowait: In a word, iowait stands for waiting for I/O to complete. But there
1469 are several problems:
1471 1. Cpu will not wait for I/O to complete, iowait is the time that a task is
1472 waiting for I/O to complete. When cpu goes into idle state for
1473 outstanding task io, another task will be scheduled on this CPU.
1474 2. In a multi-core CPU, the task waiting for I/O to complete is not running
1475 on any CPU, so the iowait of each CPU is difficult to calculate.
1476 3. The value of iowait field in /proc/stat will decrease in certain
1477 conditions.
1479 So, the iowait is not reliable by reading from /proc/stat.
1480 - irq: servicing interrupts
1481 - softirq: servicing softirqs
1482 - steal: involuntary wait
1483 - guest: running a normal guest
1484 - guest_nice: running a niced guest
1486 The "intr" line gives counts of interrupts serviced since boot time, for each
1487 of the possible system interrupts. The first column is the total of all
1488 interrupts serviced including unnumbered architecture specific interrupts;
1489 each subsequent column is the total for that particular numbered interrupt.
1490 Unnumbered interrupts are not shown, only summed into the total.
1492 The "ctxt" line gives the total number of context switches across all CPUs.
1494 The "btime" line gives the time at which the system booted, in seconds since
1495 the Unix epoch.
1497 The "processes" line gives the number of processes and threads created, which
1498 includes (but is not limited to) those created by calls to the fork() and
1499 clone() system calls.
1501 The "procs_running" line gives the total number of threads that are
1502 running or ready to run (i.e., the total number of runnable threads).
1504 The "procs_blocked" line gives the number of processes currently blocked,
1505 waiting for I/O to complete.
1507 The "softirq" line gives counts of softirqs serviced since boot time, for each
1508 of the possible system softirqs. The first column is the total of all
1509 softirqs serviced; each subsequent column is the total for that particular
1510 softirq.
1513 1.9 Ext4 file system parameters
1514 -------------------------------
1516 Information about mounted ext4 file systems can be found in
1517 /proc/fs/ext4. Each mounted filesystem will have a directory in
1518 /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1519 /proc/fs/ext4/dm-0). The files in each per-device directory are shown
1520 in Table 1-12, below.
1522 .. table:: Table 1-12: Files in /proc/fs/ext4/<devname>
1524 ============== ==========================================================
1525 File Content
1526 mb_groups details of multiblock allocator buddy cache of free blocks
1527 ============== ==========================================================
1529 2.0 /proc/consoles
1530 ------------------
1531 Shows registered system console lines.
1533 To see which character device lines are currently used for the system console
1534 /dev/console, you may simply look into the file /proc/consoles::
1536 > cat /proc/consoles
1537 tty0 -WU (ECp) 4:7
1538 ttyS0 -W- (Ep) 4:64
1540 The columns are:
1542 +--------------------+-------------------------------------------------------+
1543 | device | name of the device |
1544 +====================+=======================================================+
1545 | operations | * R = can do read operations |
1546 | | * W = can do write operations |
1547 | | * U = can do unblank |
1548 +--------------------+-------------------------------------------------------+
1549 | flags | * E = it is enabled |
1550 | | * C = it is preferred console |
1551 | | * B = it is primary boot console |
1552 | | * p = it is used for printk buffer |
1553 | | * b = it is not a TTY but a Braille device |
1554 | | * a = it is safe to use when cpu is offline |
1555 +--------------------+-------------------------------------------------------+
1556 | major:minor | major and minor number of the device separated by a |
1557 | | colon |
1558 +--------------------+-------------------------------------------------------+
1560 Summary
1561 -------
1563 The /proc file system serves information about the running system. It not only
1564 allows access to process data but also allows you to request the kernel status
1565 by reading files in the hierarchy.
1567 The directory structure of /proc reflects the types of information and makes
1568 it easy, if not obvious, where to look for specific data.
1570 Chapter 2: Modifying System Parameters
1571 ======================================
1573 In This Chapter
1574 ---------------
1576 * Modifying kernel parameters by writing into files found in /proc/sys
1577 * Exploring the files which modify certain parameters
1578 * Review of the /proc/sys file tree
1580 ------------------------------------------------------------------------------
1582 A very interesting part of /proc is the directory /proc/sys. This is not only
1583 a source of information, it also allows you to change parameters within the
1584 kernel. Be very careful when attempting this. You can optimize your system,
1585 but you can also cause it to crash. Never alter kernel parameters on a
1586 production system. Set up a development machine and test to make sure that
1587 everything works the way you want it to. You may have no alternative but to
1588 reboot the machine once an error has been made.
1590 To change a value, simply echo the new value into the file. An example is
1591 given below in the section on the file system data. You need to be root to do
1592 this. You can create your own boot script to perform this every time your
1593 system boots.
1595 The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1596 general things in the operation of the Linux kernel. Since some of the files
1597 can inadvertently disrupt your system, it is advisable to read both
1598 documentation and source before actually making adjustments. In any case, be
1599 very careful when writing to any of these files. The entries in /proc may
1600 change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1601 review the kernel documentation in the directory /usr/src/linux/Documentation.
1602 This chapter is heavily based on the documentation included in the pre 2.2
1603 kernels, and became part of it in version 2.2.1 of the Linux kernel.
1605 Please see: Documentation/admin-guide/sysctl/ directory for descriptions of these
1606 entries.
1608 Summary
1609 -------
1611 Certain aspects of kernel behavior can be modified at runtime, without the
1612 need to recompile the kernel, or even to reboot the system. The files in the
1613 /proc/sys tree can not only be read, but also modified. You can use the echo
1614 command to write value into these files, thereby changing the default settings
1615 of the kernel.
1618 Chapter 3: Per-process Parameters
1619 =================================
1621 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1622 --------------------------------------------------------------------------------
1624 These file can be used to adjust the badness heuristic used to select which
1625 process gets killed in out of memory conditions.
1627 The badness heuristic assigns a value to each candidate task ranging from 0
1628 (never kill) to 1000 (always kill) to determine which process is targeted. The
1629 units are roughly a proportion along that range of allowed memory the process
1630 may allocate from based on an estimation of its current memory and swap use.
1631 For example, if a task is using all allowed memory, its badness score will be
1632 1000. If it is using half of its allowed memory, its score will be 500.
1634 There is an additional factor included in the badness score: the current memory
1635 and swap usage is discounted by 3% for root processes.
1637 The amount of "allowed" memory depends on the context in which the oom killer
1638 was called. If it is due to the memory assigned to the allocating task's cpuset
1639 being exhausted, the allowed memory represents the set of mems assigned to that
1640 cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1641 memory represents the set of mempolicy nodes. If it is due to a memory
1642 limit (or swap limit) being reached, the allowed memory is that configured
1643 limit. Finally, if it is due to the entire system being out of memory, the
1644 allowed memory represents all allocatable resources.
1646 The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1647 is used to determine which task to kill. Acceptable values range from -1000
1648 (OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1649 polarize the preference for oom killing either by always preferring a certain
1650 task or completely disabling it. The lowest possible value, -1000, is
1651 equivalent to disabling oom killing entirely for that task since it will always
1652 report a badness score of 0.
1654 Consequently, it is very simple for userspace to define the amount of memory to
1655 consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1656 example, is roughly equivalent to allowing the remainder of tasks sharing the
1657 same system, cpuset, mempolicy, or memory controller resources to use at least
1658 50% more memory. A value of -500, on the other hand, would be roughly
1659 equivalent to discounting 50% of the task's allowed memory from being considered
1660 as scoring against the task.
1662 For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1663 be used to tune the badness score. Its acceptable values range from -16
1664 (OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1665 (OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1666 scaled linearly with /proc/<pid>/oom_score_adj.
1668 The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1669 value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1670 requires CAP_SYS_RESOURCE.
1672 Caveat: when a parent task is selected, the oom killer will sacrifice any first
1673 generation children with separate address spaces instead, if possible. This
1674 avoids servers and important system daemons from being killed and loses the
1675 minimal amount of work.
1678 3.2 /proc/<pid>/oom_score - Display current oom-killer score
1679 -------------------------------------------------------------
1681 This file can be used to check the current score used by the oom-killer is for
1682 any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1683 process should be killed in an out-of-memory situation.
1686 3.3 /proc/<pid>/io - Display the IO accounting fields
1687 -------------------------------------------------------
1689 This file contains IO statistics for each running process
1691 Example
1692 ~~~~~~~
1694 ::
1696 test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1697 [1] 3828
1699 test:/tmp # cat /proc/3828/io
1700 rchar: 323934931
1701 wchar: 323929600
1702 syscr: 632687
1703 syscw: 632675
1704 read_bytes: 0
1705 write_bytes: 323932160
1706 cancelled_write_bytes: 0
1709 Description
1710 ~~~~~~~~~~~
1712 rchar
1713 ^^^^^
1715 I/O counter: chars read
1716 The number of bytes which this task has caused to be read from storage. This
1717 is simply the sum of bytes which this process passed to read() and pread().
1718 It includes things like tty IO and it is unaffected by whether or not actual
1719 physical disk IO was required (the read might have been satisfied from
1720 pagecache)
1723 wchar
1724 ^^^^^
1726 I/O counter: chars written
1727 The number of bytes which this task has caused, or shall cause to be written
1728 to disk. Similar caveats apply here as with rchar.
1731 syscr
1732 ^^^^^
1734 I/O counter: read syscalls
1735 Attempt to count the number of read I/O operations, i.e. syscalls like read()
1736 and pread().
1739 syscw
1740 ^^^^^
1742 I/O counter: write syscalls
1743 Attempt to count the number of write I/O operations, i.e. syscalls like
1744 write() and pwrite().
1747 read_bytes
1748 ^^^^^^^^^^
1750 I/O counter: bytes read
1751 Attempt to count the number of bytes which this process really did cause to
1752 be fetched from the storage layer. Done at the submit_bio() level, so it is
1753 accurate for block-backed filesystems. <please add status regarding NFS and
1754 CIFS at a later time>
1757 write_bytes
1758 ^^^^^^^^^^^
1760 I/O counter: bytes written
1761 Attempt to count the number of bytes which this process caused to be sent to
1762 the storage layer. This is done at page-dirtying time.
1765 cancelled_write_bytes
1766 ^^^^^^^^^^^^^^^^^^^^^
1768 The big inaccuracy here is truncate. If a process writes 1MB to a file and
1769 then deletes the file, it will in fact perform no writeout. But it will have
1770 been accounted as having caused 1MB of write.
1771 In other words: The number of bytes which this process caused to not happen,
1772 by truncating pagecache. A task can cause "negative" IO too. If this task
1773 truncates some dirty pagecache, some IO which another task has been accounted
1774 for (in its write_bytes) will not be happening. We _could_ just subtract that
1775 from the truncating task's write_bytes, but there is information loss in doing
1776 that.
1779 .. Note::
1781 At its current implementation state, this is a bit racy on 32-bit machines:
1782 if process A reads process B's /proc/pid/io while process B is updating one
1783 of those 64-bit counters, process A could see an intermediate result.
1786 More information about this can be found within the taskstats documentation in
1787 Documentation/accounting.
1789 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1790 ---------------------------------------------------------------
1791 When a process is dumped, all anonymous memory is written to a core file as
1792 long as the size of the core file isn't limited. But sometimes we don't want
1793 to dump some memory segments, for example, huge shared memory or DAX.
1794 Conversely, sometimes we want to save file-backed memory segments into a core
1795 file, not only the individual files.
1797 /proc/<pid>/coredump_filter allows you to customize which memory segments
1798 will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1799 of memory types. If a bit of the bitmask is set, memory segments of the
1800 corresponding memory type are dumped, otherwise they are not dumped.
1802 The following 9 memory types are supported:
1804 - (bit 0) anonymous private memory
1805 - (bit 1) anonymous shared memory
1806 - (bit 2) file-backed private memory
1807 - (bit 3) file-backed shared memory
1808 - (bit 4) ELF header pages in file-backed private memory areas (it is
1809 effective only if the bit 2 is cleared)
1810 - (bit 5) hugetlb private memory
1811 - (bit 6) hugetlb shared memory
1812 - (bit 7) DAX private memory
1813 - (bit 8) DAX shared memory
1815 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1816 are always dumped regardless of the bitmask status.
1818 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
1819 only affected by bit 5-6, and DAX is only affected by bits 7-8.
1821 The default value of coredump_filter is 0x33; this means all anonymous memory
1822 segments, ELF header pages and hugetlb private memory are dumped.
1824 If you don't want to dump all shared memory segments attached to pid 1234,
1825 write 0x31 to the process's proc file::
1827 $ echo 0x31 > /proc/1234/coredump_filter
1829 When a new process is created, the process inherits the bitmask status from its
1830 parent. It is useful to set up coredump_filter before the program runs.
1831 For example::
1833 $ echo 0x7 > /proc/self/coredump_filter
1834 $ ./some_program
1836 3.5 /proc/<pid>/mountinfo - Information about mounts
1837 --------------------------------------------------------
1839 This file contains lines of the form::
1841 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1842 (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1844 (1) mount ID: unique identifier of the mount (may be reused after umount)
1845 (2) parent ID: ID of parent (or of self for the top of the mount tree)
1846 (3) major:minor: value of st_dev for files on filesystem
1847 (4) root: root of the mount within the filesystem
1848 (5) mount point: mount point relative to the process's root
1849 (6) mount options: per mount options
1850 (7) optional fields: zero or more fields of the form "tag[:value]"
1851 (8) separator: marks the end of the optional fields
1852 (9) filesystem type: name of filesystem of the form "type[.subtype]"
1853 (10) mount source: filesystem specific information or "none"
1854 (11) super options: per super block options
1856 Parsers should ignore all unrecognised optional fields. Currently the
1857 possible optional fields are:
1859 ================ ==============================================================
1860 shared:X mount is shared in peer group X
1861 master:X mount is slave to peer group X
1862 propagate_from:X mount is slave and receives propagation from peer group X [#]_
1863 unbindable mount is unbindable
1864 ================ ==============================================================
1866 .. [#] X is the closest dominant peer group under the process's root. If
1867 X is the immediate master of the mount, or if there's no dominant peer
1868 group under the same root, then only the "master:X" field is present
1869 and not the "propagate_from:X" field.
1871 For more information on mount propagation see:
1873 Documentation/filesystems/sharedsubtree.txt
1876 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1877 --------------------------------------------------------
1878 These files provide a method to access a tasks comm value. It also allows for
1879 a task to set its own or one of its thread siblings comm value. The comm value
1880 is limited in size compared to the cmdline value, so writing anything longer
1881 then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1882 comm value.
1885 3.7 /proc/<pid>/task/<tid>/children - Information about task children
1886 -------------------------------------------------------------------------
1887 This file provides a fast way to retrieve first level children pids
1888 of a task pointed by <pid>/<tid> pair. The format is a space separated
1889 stream of pids.
1891 Note the "first level" here -- if a child has own children they will
1892 not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1893 to obtain the descendants.
1895 Since this interface is intended to be fast and cheap it doesn't
1896 guarantee to provide precise results and some children might be
1897 skipped, especially if they've exited right after we printed their
1898 pids, so one need to either stop or freeze processes being inspected
1899 if precise results are needed.
1902 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
1903 ---------------------------------------------------------------
1904 This file provides information associated with an opened file. The regular
1905 files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1906 represents the current offset of the opened file in decimal form [see lseek(2)
1907 for details], 'flags' denotes the octal O_xxx mask the file has been
1908 created with [see open(2) for details] and 'mnt_id' represents mount ID of
1909 the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1910 for details].
1912 A typical output is::
1914 pos: 0
1915 flags: 0100002
1916 mnt_id: 19
1918 All locks associated with a file descriptor are shown in its fdinfo too::
1920 lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF
1922 The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1923 pair provide additional information particular to the objects they represent.
1925 Eventfd files
1926 ~~~~~~~~~~~~~
1928 ::
1930 pos: 0
1931 flags: 04002
1932 mnt_id: 9
1933 eventfd-count: 5a
1935 where 'eventfd-count' is hex value of a counter.
1937 Signalfd files
1938 ~~~~~~~~~~~~~~
1940 ::
1942 pos: 0
1943 flags: 04002
1944 mnt_id: 9
1945 sigmask: 0000000000000200
1947 where 'sigmask' is hex value of the signal mask associated
1948 with a file.
1950 Epoll files
1951 ~~~~~~~~~~~
1953 ::
1955 pos: 0
1956 flags: 02
1957 mnt_id: 9
1958 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7
1960 where 'tfd' is a target file descriptor number in decimal form,
1961 'events' is events mask being watched and the 'data' is data
1962 associated with a target [see epoll(7) for more details].
1964 The 'pos' is current offset of the target file in decimal form
1965 [see lseek(2)], 'ino' and 'sdev' are inode and device numbers
1966 where target file resides, all in hex format.
1968 Fsnotify files
1969 ~~~~~~~~~~~~~~
1970 For inotify files the format is the following::
1972 pos: 0
1973 flags: 02000000
1974 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1976 where 'wd' is a watch descriptor in decimal form, ie a target file
1977 descriptor number, 'ino' and 'sdev' are inode and device where the
1978 target file resides and the 'mask' is the mask of events, all in hex
1979 form [see inotify(7) for more details].
1981 If the kernel was built with exportfs support, the path to the target
1982 file is encoded as a file handle. The file handle is provided by three
1983 fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1984 format.
1986 If the kernel is built without exportfs support the file handle won't be
1987 printed out.
1989 If there is no inotify mark attached yet the 'inotify' line will be omitted.
1991 For fanotify files the format is::
1993 pos: 0
1994 flags: 02
1995 mnt_id: 9
1996 fanotify flags:10 event-flags:0
1997 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1998 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
2000 where fanotify 'flags' and 'event-flags' are values used in fanotify_init
2001 call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
2002 flags associated with mark which are tracked separately from events
2003 mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
2004 mask and 'ignored_mask' is the mask of events which are to be ignored.
2005 All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
2006 does provide information about flags and mask used in fanotify_mark
2007 call [see fsnotify manpage for details].
2009 While the first three lines are mandatory and always printed, the rest is
2010 optional and may be omitted if no marks created yet.
2012 Timerfd files
2013 ~~~~~~~~~~~~~
2015 ::
2017 pos: 0
2018 flags: 02
2019 mnt_id: 9
2020 clockid: 0
2021 ticks: 0
2022 settime flags: 01
2023 it_value: (0, 49406829)
2024 it_interval: (1, 0)
2026 where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
2027 that have occurred [see timerfd_create(2) for details]. 'settime flags' are
2028 flags in octal form been used to setup the timer [see timerfd_settime(2) for
2029 details]. 'it_value' is remaining time until the timer exiration.
2030 'it_interval' is the interval for the timer. Note the timer might be set up
2031 with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
2032 still exhibits timer's remaining time.
2034 3.9 /proc/<pid>/map_files - Information about memory mapped files
2035 ---------------------------------------------------------------------
2036 This directory contains symbolic links which represent memory mapped files
2037 the process is maintaining. Example output::
2039 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
2040 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
2041 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
2042 | ...
2043 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
2044 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
2046 The name of a link represents the virtual memory bounds of a mapping, i.e.
2047 vm_area_struct::vm_start-vm_area_struct::vm_end.
2049 The main purpose of the map_files is to retrieve a set of memory mapped
2050 files in a fast way instead of parsing /proc/<pid>/maps or
2051 /proc/<pid>/smaps, both of which contain many more records. At the same
2052 time one can open(2) mappings from the listings of two processes and
2053 comparing their inode numbers to figure out which anonymous memory areas
2054 are actually shared.
2056 3.10 /proc/<pid>/timerslack_ns - Task timerslack value
2057 ---------------------------------------------------------
2058 This file provides the value of the task's timerslack value in nanoseconds.
2059 This value specifies a amount of time that normal timers may be deferred
2060 in order to coalesce timers and avoid unnecessary wakeups.
2062 This allows a task's interactivity vs power consumption trade off to be
2063 adjusted.
2065 Writing 0 to the file will set the tasks timerslack to the default value.
2067 Valid values are from 0 - ULLONG_MAX
2069 An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
2070 permissions on the task specified to change its timerslack_ns value.
2072 3.11 /proc/<pid>/patch_state - Livepatch patch operation state
2073 -----------------------------------------------------------------
2074 When CONFIG_LIVEPATCH is enabled, this file displays the value of the
2075 patch state for the task.
2077 A value of '-1' indicates that no patch is in transition.
2079 A value of '0' indicates that a patch is in transition and the task is
2080 unpatched. If the patch is being enabled, then the task hasn't been
2081 patched yet. If the patch is being disabled, then the task has already
2082 been unpatched.
2084 A value of '1' indicates that a patch is in transition and the task is
2085 patched. If the patch is being enabled, then the task has already been
2086 patched. If the patch is being disabled, then the task hasn't been
2087 unpatched yet.
2089 3.12 /proc/<pid>/arch_status - task architecture specific status
2090 -------------------------------------------------------------------
2091 When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the
2092 architecture specific status of the task.
2094 Example
2095 ~~~~~~~
2097 ::
2099 $ cat /proc/6753/arch_status
2100 AVX512_elapsed_ms: 8
2102 Description
2103 ~~~~~~~~~~~
2105 x86 specific entries:
2106 ~~~~~~~~~~~~~~~~~~~~~
2108 AVX512_elapsed_ms:
2109 ^^^^^^^^^^^^^^^^^^
2111 If AVX512 is supported on the machine, this entry shows the milliseconds
2112 elapsed since the last time AVX512 usage was recorded. The recording
2113 happens on a best effort basis when a task is scheduled out. This means
2114 that the value depends on two factors:
2116 1) The time which the task spent on the CPU without being scheduled
2117 out. With CPU isolation and a single runnable task this can take
2118 several seconds.
2120 2) The time since the task was scheduled out last. Depending on the
2121 reason for being scheduled out (time slice exhausted, syscall ...)
2122 this can be arbitrary long time.
2124 As a consequence the value cannot be considered precise and authoritative
2125 information. The application which uses this information has to be aware
2126 of the overall scenario on the system in order to determine whether a
2127 task is a real AVX512 user or not. Precise information can be obtained
2128 with performance counters.
2130 A special value of '-1' indicates that no AVX512 usage was recorded, thus
2131 the task is unlikely an AVX512 user, but depends on the workload and the
2132 scheduling scenario, it also could be a false negative mentioned above.
2134 Configuring procfs
2135 ------------------
2137 4.1 Mount options
2138 ---------------------
2140 The following mount options are supported:
2142 ========= ========================================================
2143 hidepid= Set /proc/<pid>/ access mode.
2144 gid= Set the group authorized to learn processes information.
2145 ========= ========================================================
2147 hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
2148 (default).
2150 hidepid=1 means users may not access any /proc/<pid>/ directories but their
2151 own. Sensitive files like cmdline, sched*, status are now protected against
2152 other users. This makes it impossible to learn whether any user runs
2153 specific program (given the program doesn't reveal itself by its behaviour).
2154 As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
2155 poorly written programs passing sensitive information via program arguments are
2156 now protected against local eavesdroppers.
2158 hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
2159 users. It doesn't mean that it hides a fact whether a process with a specific
2160 pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
2161 but it hides process' uid and gid, which may be learned by stat()'ing
2162 /proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering
2163 information about running processes, whether some daemon runs with elevated
2164 privileges, whether other user runs some sensitive program, whether other users
2165 run any program at all, etc.
2167 gid= defines a group authorized to learn processes information otherwise
2168 prohibited by hidepid=. If you use some daemon like identd which needs to learn
2169 information about processes information, just add identd to this group.