1 .. SPDX-License-Identifier: GPL-2.0
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 ===================== ======================================= ================
20 0.1 Introduction/Credits
23 1 Collecting System Information
24 1.1 Process-Specific Subdirectories
26 1.3 IDE devices in /proc/ide
27 1.4 Networking info in /proc/net
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
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
59 0.1 Introduction/Credits
60 ------------------------
62 This documentation is part of a soon (or so we hope) to be released book on
63 the SuSE Linux distribution. As there is no complete documentation for the
64 /proc file system and we've used many freely available sources to write these
65 chapters, it seems only fair to give the work back to the Linux community.
66 This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
67 afraid it's still far from complete, but we hope it will be useful. As far as
68 we know, it is the first 'all-in-one' document about the /proc file system. It
69 is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
70 SPARC, AXP, etc., features, you probably won't find what you are looking for.
71 It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
72 additions and patches are welcome and will be added to this document if you
75 We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
76 other people for help compiling this documentation. We'd also like to extend a
77 special thank you to Andi Kleen for documentation, which we relied on heavily
78 to create this document, as well as the additional information he provided.
79 Thanks to everybody else who contributed source or docs to the Linux kernel
80 and helped create a great piece of software... :)
82 If you have any comments, corrections or additions, please don't hesitate to
83 contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
86 The latest version of this document is available online at
87 http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
89 If the above direction does not works for you, you could try the kernel
90 mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
91 comandante@zaralinux.com.
96 We don't guarantee the correctness of this document, and if you come to us
97 complaining about how you screwed up your system because of incorrect
98 documentation, we won't feel responsible...
100 Chapter 1: Collecting System Information
101 ========================================
105 * Investigating the properties of the pseudo file system /proc and its
106 ability to provide information on the running Linux system
107 * Examining /proc's structure
108 * Uncovering various information about the kernel and the processes running
111 ------------------------------------------------------------------------------
113 The proc file system acts as an interface to internal data structures in the
114 kernel. It can be used to obtain information about the system and to change
115 certain kernel parameters at runtime (sysctl).
117 First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
118 show you how you can use /proc/sys to change settings.
120 1.1 Process-Specific Subdirectories
121 -----------------------------------
123 The directory /proc contains (among other things) one subdirectory for each
124 process running on the system, which is named after the process ID (PID).
126 The link 'self' points to the process reading the file system. Each process
127 subdirectory has the entries listed in Table 1-1.
129 Note that an open file descriptor to /proc/<pid> or to any of its
130 contained files or subdirectories does not prevent <pid> being reused
131 for some other process in the event that <pid> exits. Operations on
132 open /proc/<pid> file descriptors corresponding to dead processes
133 never act on any new process that the kernel may, through chance, have
134 also assigned the process ID <pid>. Instead, operations on these FDs
135 usually fail with ESRCH.
137 .. table:: Table 1-1: Process specific entries in /proc
139 ============= ===============================================================
141 ============= ===============================================================
142 clear_refs Clears page referenced bits shown in smaps output
143 cmdline Command line arguments
144 cpu Current and last cpu in which it was executed (2.4)(smp)
145 cwd Link to the current working directory
146 environ Values of environment variables
147 exe Link to the executable of this process
148 fd Directory, which contains all file descriptors
149 maps Memory maps to executables and library files (2.4)
150 mem Memory held by this process
151 root Link to the root directory of this process
153 statm Process memory status information
154 status Process status in human readable form
155 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function
156 symbol the task is blocked in - or "0" if not blocked.
158 stack Report full stack trace, enable via CONFIG_STACKTRACE
159 smaps An extension based on maps, showing the memory consumption of
160 each mapping and flags associated with it
161 smaps_rollup Accumulated smaps stats for all mappings of the process. This
162 can be derived from smaps, but is faster and more convenient
163 numa_maps An extension based on maps, showing the memory locality and
164 binding policy as well as mem usage (in pages) of each mapping.
165 ============= ===============================================================
167 For example, to get the status information of a process, all you have to do is
168 read the file /proc/PID/status::
170 >cat /proc/self/status
200 SigPnd: 0000000000000000
201 ShdPnd: 0000000000000000
202 SigBlk: 0000000000000000
203 SigIgn: 0000000000000000
204 SigCgt: 0000000000000000
205 CapInh: 00000000fffffeff
206 CapPrm: 0000000000000000
207 CapEff: 0000000000000000
208 CapBnd: ffffffffffffffff
209 CapAmb: 0000000000000000
212 Speculation_Store_Bypass: thread vulnerable
213 SpeculationIndirectBranch: conditional enabled
214 voluntary_ctxt_switches: 0
215 nonvoluntary_ctxt_switches: 1
217 This shows you nearly the same information you would get if you viewed it with
218 the ps command. In fact, ps uses the proc file system to obtain its
219 information. But you get a more detailed view of the process by reading the
220 file /proc/PID/status. It fields are described in table 1-2.
222 The statm file contains more detailed information about the process
223 memory usage. Its seven fields are explained in Table 1-3. The stat file
224 contains detailed information about the process itself. Its fields are
225 explained in Table 1-4.
227 (for SMP CONFIG users)
229 For making accounting scalable, RSS related information are handled in an
230 asynchronous manner and the value may not be very precise. To see a precise
231 snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
232 It's slow but very precise.
234 .. table:: Table 1-2: Contents of the status files (as of 4.19)
236 ========================== ===================================================
238 ========================== ===================================================
239 Name filename of the executable
240 Umask file mode creation mask
241 State state (R is running, S is sleeping, D is sleeping
242 in an uninterruptible wait, Z is zombie,
243 T is traced or stopped)
245 Ngid NUMA group ID (0 if none)
247 PPid process id of the parent process
248 TracerPid PID of process tracing this process (0 if not)
249 Uid Real, effective, saved set, and file system UIDs
250 Gid Real, effective, saved set, and file system GIDs
251 FDSize number of file descriptor slots currently allocated
252 Groups supplementary group list
253 NStgid descendant namespace thread group ID hierarchy
254 NSpid descendant namespace process ID hierarchy
255 NSpgid descendant namespace process group ID hierarchy
256 NSsid descendant namespace session ID hierarchy
257 VmPeak peak virtual memory size
258 VmSize total program size
259 VmLck locked memory size
260 VmPin pinned memory size
261 VmHWM peak resident set size ("high water mark")
262 VmRSS size of memory portions. It contains the three
264 (VmRSS = RssAnon + RssFile + RssShmem)
265 RssAnon size of resident anonymous memory
266 RssFile size of resident file mappings
267 RssShmem size of resident shmem memory (includes SysV shm,
268 mapping of tmpfs and shared anonymous mappings)
269 VmData size of private data segments
270 VmStk size of stack segments
271 VmExe size of text segment
272 VmLib size of shared library code
273 VmPTE size of page table entries
274 VmSwap amount of swap used by anonymous private data
275 (shmem swap usage is not included)
276 HugetlbPages size of hugetlb memory portions
277 CoreDumping process's memory is currently being dumped
278 (killing the process may lead to a corrupted core)
279 THP_enabled process is allowed to use THP (returns 0 when
280 PR_SET_THP_DISABLE is set on the process
281 Threads number of threads
282 SigQ number of signals queued/max. number for queue
283 SigPnd bitmap of pending signals for the thread
284 ShdPnd bitmap of shared pending signals for the process
285 SigBlk bitmap of blocked signals
286 SigIgn bitmap of ignored signals
287 SigCgt bitmap of caught signals
288 CapInh bitmap of inheritable capabilities
289 CapPrm bitmap of permitted capabilities
290 CapEff bitmap of effective capabilities
291 CapBnd bitmap of capabilities bounding set
292 CapAmb bitmap of ambient capabilities
293 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
294 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
295 Speculation_Store_Bypass speculative store bypass mitigation status
296 SpeculationIndirectBranch indirect branch speculation mode
297 Cpus_allowed mask of CPUs on which this process may run
298 Cpus_allowed_list Same as previous, but in "list format"
299 Mems_allowed mask of memory nodes allowed to this process
300 Mems_allowed_list Same as previous, but in "list format"
301 voluntary_ctxt_switches number of voluntary context switches
302 nonvoluntary_ctxt_switches number of non voluntary context switches
303 ========================== ===================================================
306 .. table:: Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
308 ======== =============================== ==============================
310 ======== =============================== ==============================
311 size total program size (pages) (same as VmSize in status)
312 resident size of memory portions (pages) (same as VmRSS in status)
313 shared number of pages that are shared (i.e. backed by a file, same
314 as RssFile+RssShmem in status)
315 trs number of pages that are 'code' (not including libs; broken,
316 includes data segment)
317 lrs number of pages of library (always 0 on 2.6)
318 drs number of pages of data/stack (including libs; broken,
319 includes library text)
320 dt number of dirty pages (always 0 on 2.6)
321 ======== =============================== ==============================
324 .. table:: Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
326 ============= ===============================================================
328 ============= ===============================================================
330 tcomm filename of the executable
331 state state (R is running, S is sleeping, D is sleeping in an
332 uninterruptible wait, Z is zombie, T is traced or stopped)
333 ppid process id of the parent process
334 pgrp pgrp of the process
336 tty_nr tty the process uses
337 tty_pgrp pgrp of the tty
339 min_flt number of minor faults
340 cmin_flt number of minor faults with child's
341 maj_flt number of major faults
342 cmaj_flt number of major faults with child's
343 utime user mode jiffies
344 stime kernel mode jiffies
345 cutime user mode jiffies with child's
346 cstime kernel mode jiffies with child's
347 priority priority level
349 num_threads number of threads
350 it_real_value (obsolete, always 0)
351 start_time time the process started after system boot
352 vsize virtual memory size
353 rss resident set memory size
354 rsslim current limit in bytes on the rss
355 start_code address above which program text can run
356 end_code address below which program text can run
357 start_stack address of the start of the main process stack
358 esp current value of ESP
359 eip current value of EIP
360 pending bitmap of pending signals
361 blocked bitmap of blocked signals
362 sigign bitmap of ignored signals
363 sigcatch bitmap of caught signals
364 0 (place holder, used to be the wchan address,
365 use /proc/PID/wchan instead)
368 exit_signal signal to send to parent thread on exit
369 task_cpu which CPU the task is scheduled on
370 rt_priority realtime priority
371 policy scheduling policy (man sched_setscheduler)
372 blkio_ticks time spent waiting for block IO
373 gtime guest time of the task in jiffies
374 cgtime guest time of the task children in jiffies
375 start_data address above which program data+bss is placed
376 end_data address below which program data+bss is placed
377 start_brk address above which program heap can be expanded with brk()
378 arg_start address above which program command line is placed
379 arg_end address below which program command line is placed
380 env_start address above which program environment is placed
381 env_end address below which program environment is placed
382 exit_code the thread's exit_code in the form reported by the waitpid
384 ============= ===============================================================
386 The /proc/PID/maps file contains the currently mapped memory regions and
387 their access permissions.
391 address perms offset dev inode pathname
393 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test
394 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
395 0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
396 a7cb1000-a7cb2000 ---p 00000000 00:00 0
397 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
398 a7eb2000-a7eb3000 ---p 00000000 00:00 0
399 a7eb3000-a7ed5000 rw-p 00000000 00:00 0
400 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
401 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
402 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
403 a800b000-a800e000 rw-p 00000000 00:00 0
404 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
405 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
406 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
407 a8024000-a8027000 rw-p 00000000 00:00 0
408 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
409 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
410 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
411 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
412 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
414 where "address" is the address space in the process that it occupies, "perms"
415 is a set of permissions::
421 p = private (copy on write)
423 "offset" is the offset into the mapping, "dev" is the device (major:minor), and
424 "inode" is the inode on that device. 0 indicates that no inode is associated
425 with the memory region, as the case would be with BSS (uninitialized data).
426 The "pathname" shows the name associated file for this mapping. If the mapping
427 is not associated with a file:
429 ======= ====================================
430 [heap] the heap of the program
431 [stack] the stack of the main process
432 [vdso] the "virtual dynamic shared object",
433 the kernel system call handler
434 ======= ====================================
436 or if empty, the mapping is anonymous.
438 The /proc/PID/smaps is an extension based on maps, showing the memory
439 consumption for each of the process's mappings. For each mapping (aka Virtual
440 Memory Area, or VMA) there is a series of lines such as the following::
442 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
459 Private_Hugetlb: 0 kB
466 VmFlags: rd ex mr mw me dw
468 The first of these lines shows the same information as is displayed for the
469 mapping in /proc/PID/maps. Following lines show the size of the mapping
470 (size); the size of each page allocated when backing a VMA (KernelPageSize),
471 which is usually the same as the size in the page table entries; the page size
472 used by the MMU when backing a VMA (in most cases, the same as KernelPageSize);
473 the amount of the mapping that is currently resident in RAM (RSS); the
474 process' proportional share of this mapping (PSS); and the number of clean and
475 dirty shared and private pages in the mapping.
477 The "proportional set size" (PSS) of a process is the count of pages it has
478 in memory, where each page is divided by the number of processes sharing it.
479 So if a process has 1000 pages all to itself, and 1000 shared with one other
480 process, its PSS will be 1500.
482 Note that even a page which is part of a MAP_SHARED mapping, but has only
483 a single pte mapped, i.e. is currently used by only one process, is accounted
484 as private and not as shared.
486 "Referenced" indicates the amount of memory currently marked as referenced or
489 "Anonymous" shows the amount of memory that does not belong to any file. Even
490 a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
491 and a page is modified, the file page is replaced by a private anonymous copy.
493 "LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE).
494 The memory isn't freed immediately with madvise(). It's freed in memory
495 pressure if the memory is clean. Please note that the printed value might
496 be lower than the real value due to optimizations used in the current
497 implementation. If this is not desirable please file a bug report.
499 "AnonHugePages" shows the ammount of memory backed by transparent hugepage.
501 "ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by
504 "Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
505 hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
506 reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
508 "Swap" shows how much would-be-anonymous memory is also used, but out on swap.
510 For shmem mappings, "Swap" includes also the size of the mapped (and not
511 replaced by copy-on-write) part of the underlying shmem object out on swap.
512 "SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
513 does not take into account swapped out page of underlying shmem objects.
514 "Locked" indicates whether the mapping is locked in memory or not.
515 "THPeligible" indicates whether the mapping is eligible for allocating THP
516 pages - 1 if true, 0 otherwise. It just shows the current status.
518 "VmFlags" field deserves a separate description. This member represents the
519 kernel flags associated with the particular virtual memory area in two letter
520 encoded manner. The codes are the following:
522 == =======================================
531 gd stack segment growns down
533 dw disabled write to the mapped file
534 lo pages are locked in memory
535 io memory mapped I/O area
536 sr sequential read advise provided
537 rr random read advise provided
538 dc do not copy area on fork
539 de do not expand area on remapping
540 ac area is accountable
541 nr swap space is not reserved for the area
542 ht area uses huge tlb pages
543 ar architecture specific flag
544 dd do not include area into core dump
547 hg huge page advise flag
548 nh no huge page advise flag
549 mg mergable advise flag
550 bt arm64 BTI guarded page
551 mt arm64 MTE allocation tags are enabled
552 == =======================================
554 Note that there is no guarantee that every flag and associated mnemonic will
555 be present in all further kernel releases. Things get changed, the flags may
556 be vanished or the reverse -- new added. Interpretation of their meaning
557 might change in future as well. So each consumer of these flags has to
558 follow each specific kernel version for the exact semantic.
560 This file is only present if the CONFIG_MMU kernel configuration option is
563 Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent
564 output can be achieved only in the single read call).
566 This typically manifests when doing partial reads of these files while the
567 memory map is being modified. Despite the races, we do provide the following
570 1) The mapped addresses never go backwards, which implies no two
571 regions will ever overlap.
572 2) If there is something at a given vaddr during the entirety of the
573 life of the smaps/maps walk, there will be some output for it.
575 The /proc/PID/smaps_rollup file includes the same fields as /proc/PID/smaps,
576 but their values are the sums of the corresponding values for all mappings of
577 the process. Additionally, it contains these fields:
583 They represent the proportional shares of anonymous, file, and shmem pages, as
584 described for smaps above. These fields are omitted in smaps since each
585 mapping identifies the type (anon, file, or shmem) of all pages it contains.
586 Thus all information in smaps_rollup can be derived from smaps, but at a
587 significantly higher cost.
589 The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
590 bits on both physical and virtual pages associated with a process, and the
591 soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst
593 To clear the bits for all the pages associated with the process::
595 > echo 1 > /proc/PID/clear_refs
597 To clear the bits for the anonymous pages associated with the process::
599 > echo 2 > /proc/PID/clear_refs
601 To clear the bits for the file mapped pages associated with the process::
603 > echo 3 > /proc/PID/clear_refs
605 To clear the soft-dirty bit::
607 > echo 4 > /proc/PID/clear_refs
609 To reset the peak resident set size ("high water mark") to the process's
612 > echo 5 > /proc/PID/clear_refs
614 Any other value written to /proc/PID/clear_refs will have no effect.
616 The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
617 using /proc/kpageflags and number of times a page is mapped using
618 /proc/kpagecount. For detailed explanation, see
619 Documentation/admin-guide/mm/pagemap.rst.
621 The /proc/pid/numa_maps is an extension based on maps, showing the memory
622 locality and binding policy, as well as the memory usage (in pages) of
623 each mapping. The output follows a general format where mapping details get
624 summarized separated by blank spaces, one mapping per each file line::
626 address policy mapping details
628 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
629 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
630 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
631 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
632 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
633 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
634 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
635 320698b000 default file=/lib64/libc-2.12.so
636 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
637 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
638 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
639 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
640 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
641 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
642 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
643 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
647 "address" is the starting address for the mapping;
649 "policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst);
651 "mapping details" summarizes mapping data such as mapping type, page usage counters,
652 node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
653 size, in KB, that is backing the mapping up.
658 Similar to the process entries, the kernel data files give information about
659 the running kernel. The files used to obtain this information are contained in
660 /proc and are listed in Table 1-5. Not all of these will be present in your
661 system. It depends on the kernel configuration and the loaded modules, which
662 files are there, and which are missing.
664 .. table:: Table 1-5: Kernel info in /proc
666 ============ ===============================================================
668 ============ ===============================================================
669 apm Advanced power management info
670 buddyinfo Kernel memory allocator information (see text) (2.5)
671 bus Directory containing bus specific information
672 cmdline Kernel command line
673 cpuinfo Info about the CPU
674 devices Available devices (block and character)
675 dma Used DMS channels
676 filesystems Supported filesystems
677 driver Various drivers grouped here, currently rtc (2.4)
678 execdomains Execdomains, related to security (2.4)
679 fb Frame Buffer devices (2.4)
680 fs File system parameters, currently nfs/exports (2.4)
681 ide Directory containing info about the IDE subsystem
682 interrupts Interrupt usage
683 iomem Memory map (2.4)
684 ioports I/O port usage
685 irq Masks for irq to cpu affinity (2.4)(smp?)
686 isapnp ISA PnP (Plug&Play) Info (2.4)
687 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
689 ksyms Kernel symbol table
690 loadavg Load average of last 1, 5 & 15 minutes
694 modules List of loaded modules
695 mounts Mounted filesystems
696 net Networking info (see text)
697 pagetypeinfo Additional page allocator information (see text) (2.5)
698 partitions Table of partitions known to the system
699 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
700 decoupled by lspci (2.4)
702 scsi SCSI info (see text)
703 slabinfo Slab pool info
704 softirqs softirq usage
705 stat Overall statistics
706 swaps Swap space utilization
708 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
709 tty Info of tty drivers
710 uptime Wall clock since boot, combined idle time of all cpus
711 version Kernel version
712 video bttv info of video resources (2.4)
713 vmallocinfo Show vmalloced areas
714 ============ ===============================================================
716 You can, for example, check which interrupts are currently in use and what
717 they are used for by looking in the file /proc/interrupts::
719 > cat /proc/interrupts
721 0: 8728810 XT-PIC timer
722 1: 895 XT-PIC keyboard
724 3: 531695 XT-PIC aha152x
725 4: 2014133 XT-PIC serial
726 5: 44401 XT-PIC pcnet_cs
729 12: 182918 XT-PIC PS/2 Mouse
731 14: 1232265 XT-PIC ide0
735 In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
736 output of a SMP machine)::
738 > cat /proc/interrupts
741 0: 1243498 1214548 IO-APIC-edge timer
742 1: 8949 8958 IO-APIC-edge keyboard
743 2: 0 0 XT-PIC cascade
744 5: 11286 10161 IO-APIC-edge soundblaster
745 8: 1 0 IO-APIC-edge rtc
746 9: 27422 27407 IO-APIC-edge 3c503
747 12: 113645 113873 IO-APIC-edge PS/2 Mouse
749 14: 22491 24012 IO-APIC-edge ide0
750 15: 2183 2415 IO-APIC-edge ide1
751 17: 30564 30414 IO-APIC-level eth0
752 18: 177 164 IO-APIC-level bttv
757 NMI is incremented in this case because every timer interrupt generates a NMI
758 (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
760 LOC is the local interrupt counter of the internal APIC of every CPU.
762 ERR is incremented in the case of errors in the IO-APIC bus (the bus that
763 connects the CPUs in a SMP system. This means that an error has been detected,
764 the IO-APIC automatically retry the transmission, so it should not be a big
765 problem, but you should read the SMP-FAQ.
767 In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
768 /proc/interrupts to display every IRQ vector in use by the system, not
769 just those considered 'most important'. The new vectors are:
772 interrupt raised when a machine check threshold counter
773 (typically counting ECC corrected errors of memory or cache) exceeds
774 a configurable threshold. Only available on some systems.
777 a thermal event interrupt occurs when a temperature threshold
778 has been exceeded for the CPU. This interrupt may also be generated
779 when the temperature drops back to normal.
782 a spurious interrupt is some interrupt that was raised then lowered
783 by some IO device before it could be fully processed by the APIC. Hence
784 the APIC sees the interrupt but does not know what device it came from.
785 For this case the APIC will generate the interrupt with a IRQ vector
786 of 0xff. This might also be generated by chipset bugs.
789 rescheduling, call and TLB flush interrupts are
790 sent from one CPU to another per the needs of the OS. Typically,
791 their statistics are used by kernel developers and interested users to
792 determine the occurrence of interrupts of the given type.
794 The above IRQ vectors are displayed only when relevant. For example,
795 the threshold vector does not exist on x86_64 platforms. Others are
796 suppressed when the system is a uniprocessor. As of this writing, only
797 i386 and x86_64 platforms support the new IRQ vector displays.
799 Of some interest is the introduction of the /proc/irq directory to 2.4.
800 It could be used to set IRQ to CPU affinity. This means that you can "hook" an
801 IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
802 irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
808 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
809 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
813 smp_affinity is a bitmask, in which you can specify which CPUs can handle the
814 IRQ. You can set it by doing::
816 > echo 1 > /proc/irq/10/smp_affinity
818 This means that only the first CPU will handle the IRQ, but you can also echo
819 5 which means that only the first and third CPU can handle the IRQ.
821 The contents of each smp_affinity file is the same by default::
823 > cat /proc/irq/0/smp_affinity
826 There is an alternate interface, smp_affinity_list which allows specifying
827 a CPU range instead of a bitmask::
829 > cat /proc/irq/0/smp_affinity_list
832 The default_smp_affinity mask applies to all non-active IRQs, which are the
833 IRQs which have not yet been allocated/activated, and hence which lack a
834 /proc/irq/[0-9]* directory.
836 The node file on an SMP system shows the node to which the device using the IRQ
837 reports itself as being attached. This hardware locality information does not
838 include information about any possible driver locality preference.
840 prof_cpu_mask specifies which CPUs are to be profiled by the system wide
841 profiler. Default value is ffffffff (all CPUs if there are only 32 of them).
843 The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
844 between all the CPUs which are allowed to handle it. As usual the kernel has
845 more info than you and does a better job than you, so the defaults are the
846 best choice for almost everyone. [Note this applies only to those IO-APIC's
847 that support "Round Robin" interrupt distribution.]
849 There are three more important subdirectories in /proc: net, scsi, and sys.
850 The general rule is that the contents, or even the existence of these
851 directories, depend on your kernel configuration. If SCSI is not enabled, the
852 directory scsi may not exist. The same is true with the net, which is there
853 only when networking support is present in the running kernel.
855 The slabinfo file gives information about memory usage at the slab level.
856 Linux uses slab pools for memory management above page level in version 2.2.
857 Commonly used objects have their own slab pool (such as network buffers,
858 directory cache, and so on).
862 > cat /proc/buddyinfo
864 Node 0, zone DMA 0 4 5 4 4 3 ...
865 Node 0, zone Normal 1 0 0 1 101 8 ...
866 Node 0, zone HighMem 2 0 0 1 1 0 ...
868 External fragmentation is a problem under some workloads, and buddyinfo is a
869 useful tool for helping diagnose these problems. Buddyinfo will give you a
870 clue as to how big an area you can safely allocate, or why a previous
873 Each column represents the number of pages of a certain order which are
874 available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
875 ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
876 available in ZONE_NORMAL, etc...
878 More information relevant to external fragmentation can be found in
881 > cat /proc/pagetypeinfo
885 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
886 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
887 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
888 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
889 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
890 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
891 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
892 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
893 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
894 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
895 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
897 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
898 Node 0, zone DMA 2 0 5 1 0
899 Node 0, zone DMA32 41 6 967 2 0
901 Fragmentation avoidance in the kernel works by grouping pages of different
902 migrate types into the same contiguous regions of memory called page blocks.
903 A page block is typically the size of the default hugepage size, e.g. 2MB on
904 X86-64. By keeping pages grouped based on their ability to move, the kernel
905 can reclaim pages within a page block to satisfy a high-order allocation.
907 The pagetypinfo begins with information on the size of a page block. It
908 then gives the same type of information as buddyinfo except broken down
909 by migrate-type and finishes with details on how many page blocks of each
912 If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
913 from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
914 make an estimate of the likely number of huge pages that can be allocated
915 at a given point in time. All the "Movable" blocks should be allocatable
916 unless memory has been mlock()'d. Some of the Reclaimable blocks should
917 also be allocatable although a lot of filesystem metadata may have to be
918 reclaimed to achieve this.
924 Provides information about distribution and utilization of memory. This
925 varies by architecture and compile options. The following is from a
926 16GB PIII, which has highmem enabled. You may not have all of these fields.
932 MemTotal: 16344972 kB
934 MemAvailable: 14836172 kB
940 HighTotal: 15597528 kB
941 HighFree: 13629632 kB
951 KReclaimable: 168048 kB
953 SReclaimable: 159856 kB
954 SUnreclaim: 124508 kB
959 CommitLimit: 7669796 kB
960 Committed_AS: 100056 kB
961 VmallocTotal: 112216 kB
963 VmallocChunk: 111088 kB
965 HardwareCorrupted: 0 kB
966 AnonHugePages: 49152 kB
971 Total usable RAM (i.e. physical RAM minus a few reserved
972 bits and the kernel binary code)
974 The sum of LowFree+HighFree
976 An estimate of how much memory is available for starting new
977 applications, without swapping. Calculated from MemFree,
978 SReclaimable, the size of the file LRU lists, and the low
979 watermarks in each zone.
980 The estimate takes into account that the system needs some
981 page cache to function well, and that not all reclaimable
982 slab will be reclaimable, due to items being in use. The
983 impact of those factors will vary from system to system.
985 Relatively temporary storage for raw disk blocks
986 shouldn't get tremendously large (20MB or so)
988 in-memory cache for files read from the disk (the
989 pagecache). Doesn't include SwapCached
991 Memory that once was swapped out, is swapped back in but
992 still also is in the swapfile (if memory is needed it
993 doesn't need to be swapped out AGAIN because it is already
994 in the swapfile. This saves I/O)
996 Memory that has been used more recently and usually not
997 reclaimed unless absolutely necessary.
999 Memory which has been less recently used. It is more
1000 eligible to be reclaimed for other purposes
1002 Highmem is all memory above ~860MB of physical memory.
1003 Highmem areas are for use by userspace programs, or
1004 for the pagecache. The kernel must use tricks to access
1005 this memory, making it slower to access than lowmem.
1007 Lowmem is memory which can be used for everything that
1008 highmem can be used for, but it is also available for the
1009 kernel's use for its own data structures. Among many
1010 other things, it is where everything from the Slab is
1011 allocated. Bad things happen when you're out of lowmem.
1013 total amount of swap space available
1015 Memory which has been evicted from RAM, and is temporarily
1018 Memory which is waiting to get written back to the disk
1020 Memory which is actively being written back to the disk
1022 Non-file backed pages mapped into userspace page tables
1024 The amount of RAM/memory in KB, the kernel identifies as
1027 Non-file backed huge pages mapped into userspace page tables
1029 files which have been mmaped, such as libraries
1031 Total memory used by shared memory (shmem) and tmpfs
1033 Memory used by shared memory (shmem) and tmpfs allocated
1036 Shared memory mapped into userspace with huge pages
1038 Kernel allocations that the kernel will attempt to reclaim
1039 under memory pressure. Includes SReclaimable (below), and other
1040 direct allocations with a shrinker.
1042 in-kernel data structures cache
1044 Part of Slab, that might be reclaimed, such as caches
1046 Part of Slab, that cannot be reclaimed on memory pressure
1048 amount of memory dedicated to the lowest level of page
1051 Always zero. Previous counted pages which had been written to
1052 the server, but has not been committed to stable storage.
1054 Memory used for block device "bounce buffers"
1056 Memory used by FUSE for temporary writeback buffers
1058 Based on the overcommit ratio ('vm.overcommit_ratio'),
1059 this is the total amount of memory currently available to
1060 be allocated on the system. This limit is only adhered to
1061 if strict overcommit accounting is enabled (mode 2 in
1062 'vm.overcommit_memory').
1064 The CommitLimit is calculated with the following formula::
1066 CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
1067 overcommit_ratio / 100 + [total swap pages]
1069 For example, on a system with 1G of physical RAM and 7G
1070 of swap with a `vm.overcommit_ratio` of 30 it would
1071 yield a CommitLimit of 7.3G.
1073 For more details, see the memory overcommit documentation
1074 in vm/overcommit-accounting.
1076 The amount of memory presently allocated on the system.
1077 The committed memory is a sum of all of the memory which
1078 has been allocated by processes, even if it has not been
1079 "used" by them as of yet. A process which malloc()'s 1G
1080 of memory, but only touches 300M of it will show up as
1081 using 1G. This 1G is memory which has been "committed" to
1082 by the VM and can be used at any time by the allocating
1083 application. With strict overcommit enabled on the system
1084 (mode 2 in 'vm.overcommit_memory'), allocations which would
1085 exceed the CommitLimit (detailed above) will not be permitted.
1086 This is useful if one needs to guarantee that processes will
1087 not fail due to lack of memory once that memory has been
1088 successfully allocated.
1090 total size of vmalloc memory area
1092 amount of vmalloc area which is used
1094 largest contiguous block of vmalloc area which is free
1096 Memory allocated to the percpu allocator used to back percpu
1097 allocations. This stat excludes the cost of metadata.
1102 Provides information about vmalloced/vmaped areas. One line per area,
1103 containing the virtual address range of the area, size in bytes,
1104 caller information of the creator, and optional information depending
1105 on the kind of area:
1107 ========== ===================================================
1108 pages=nr number of pages
1109 phys=addr if a physical address was specified
1110 ioremap I/O mapping (ioremap() and friends)
1111 vmalloc vmalloc() area
1113 user VM_USERMAP area
1114 vpages buffer for pages pointers was vmalloced (huge area)
1115 N<node>=nr (Only on NUMA kernels)
1116 Number of pages allocated on memory node <node>
1117 ========== ===================================================
1121 > cat /proc/vmallocinfo
1122 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
1123 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
1124 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
1125 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
1126 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
1127 phys=7fee8000 ioremap
1128 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
1129 phys=7fee7000 ioremap
1130 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
1131 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
1132 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
1133 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
1134 pages=2 vmalloc N1=2
1135 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
1136 /0x130 [x_tables] pages=4 vmalloc N0=4
1137 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
1138 pages=14 vmalloc N2=14
1139 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
1140 pages=4 vmalloc N1=4
1141 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
1142 pages=2 vmalloc N1=2
1143 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
1144 pages=10 vmalloc N0=10
1150 Provides counts of softirq handlers serviced since boot time, for each CPU.
1154 > cat /proc/softirqs
1157 TIMER: 27166 27120 27097 27034
1162 SCHED: 27035 26983 26971 26746
1164 RCU: 1678 1769 2178 2250
1167 1.3 IDE devices in /proc/ide
1168 ----------------------------
1170 The subdirectory /proc/ide contains information about all IDE devices of which
1171 the kernel is aware. There is one subdirectory for each IDE controller, the
1172 file drivers and a link for each IDE device, pointing to the device directory
1173 in the controller specific subtree.
1175 The file 'drivers' contains general information about the drivers used for the
1178 > cat /proc/ide/drivers
1179 ide-cdrom version 4.53
1180 ide-disk version 1.08
1182 More detailed information can be found in the controller specific
1183 subdirectories. These are named ide0, ide1 and so on. Each of these
1184 directories contains the files shown in table 1-6.
1187 .. table:: Table 1-6: IDE controller info in /proc/ide/ide?
1189 ======= =======================================
1191 ======= =======================================
1192 channel IDE channel (0 or 1)
1193 config Configuration (only for PCI/IDE bridge)
1195 model Type/Chipset of IDE controller
1196 ======= =======================================
1198 Each device connected to a controller has a separate subdirectory in the
1199 controllers directory. The files listed in table 1-7 are contained in these
1203 .. table:: Table 1-7: IDE device information
1205 ================ ==========================================
1207 ================ ==========================================
1209 capacity Capacity of the medium (in 512Byte blocks)
1210 driver driver and version
1211 geometry physical and logical geometry
1212 identify device identify block
1214 model device identifier
1215 settings device setup
1216 smart_thresholds IDE disk management thresholds
1217 smart_values IDE disk management values
1218 ================ ==========================================
1220 The most interesting file is ``settings``. This file contains a nice
1221 overview of the drive parameters::
1223 # cat /proc/ide/ide0/hda/settings
1224 name value min max mode
1225 ---- ----- --- --- ----
1226 bios_cyl 526 0 65535 rw
1227 bios_head 255 0 255 rw
1228 bios_sect 63 0 63 rw
1229 breada_readahead 4 0 127 rw
1231 file_readahead 72 0 2097151 rw
1233 keepsettings 0 0 1 rw
1234 max_kb_per_request 122 1 127 rw
1238 pio_mode write-only 0 255 w
1244 1.4 Networking info in /proc/net
1245 --------------------------------
1247 The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
1248 additional values you get for IP version 6 if you configure the kernel to
1249 support this. Table 1-9 lists the files and their meaning.
1252 .. table:: Table 1-8: IPv6 info in /proc/net
1254 ========== =====================================================
1256 ========== =====================================================
1257 udp6 UDP sockets (IPv6)
1258 tcp6 TCP sockets (IPv6)
1259 raw6 Raw device statistics (IPv6)
1260 igmp6 IP multicast addresses, which this host joined (IPv6)
1261 if_inet6 List of IPv6 interface addresses
1262 ipv6_route Kernel routing table for IPv6
1263 rt6_stats Global IPv6 routing tables statistics
1264 sockstat6 Socket statistics (IPv6)
1265 snmp6 Snmp data (IPv6)
1266 ========== =====================================================
1268 .. table:: Table 1-9: Network info in /proc/net
1270 ============= ================================================================
1272 ============= ================================================================
1273 arp Kernel ARP table
1274 dev network devices with statistics
1275 dev_mcast the Layer2 multicast groups a device is listening too
1276 (interface index, label, number of references, number of bound
1278 dev_stat network device status
1279 ip_fwchains Firewall chain linkage
1280 ip_fwnames Firewall chain names
1281 ip_masq Directory containing the masquerading tables
1282 ip_masquerade Major masquerading table
1283 netstat Network statistics
1284 raw raw device statistics
1285 route Kernel routing table
1286 rpc Directory containing rpc info
1287 rt_cache Routing cache
1289 sockstat Socket statistics
1292 unix UNIX domain sockets
1293 wireless Wireless interface data (Wavelan etc)
1294 igmp IP multicast addresses, which this host joined
1295 psched Global packet scheduler parameters.
1296 netlink List of PF_NETLINK sockets
1297 ip_mr_vifs List of multicast virtual interfaces
1298 ip_mr_cache List of multicast routing cache
1299 ============= ================================================================
1301 You can use this information to see which network devices are available in
1302 your system and how much traffic was routed over those devices::
1305 Inter-|Receive |[...
1306 face |bytes packets errs drop fifo frame compressed multicast|[...
1307 lo: 908188 5596 0 0 0 0 0 0 [...
1308 ppp0:15475140 20721 410 0 0 410 0 0 [...
1309 eth0: 614530 7085 0 0 0 0 0 1 [...
1312 ...] bytes packets errs drop fifo colls carrier compressed
1313 ...] 908188 5596 0 0 0 0 0 0
1314 ...] 1375103 17405 0 0 0 0 0 0
1315 ...] 1703981 5535 0 0 0 3 0 0
1317 In addition, each Channel Bond interface has its own directory. For
1318 example, the bond0 device will have a directory called /proc/net/bond0/.
1319 It will contain information that is specific to that bond, such as the
1320 current slaves of the bond, the link status of the slaves, and how
1321 many times the slaves link has failed.
1326 If you have a SCSI host adapter in your system, you'll find a subdirectory
1327 named after the driver for this adapter in /proc/scsi. You'll also see a list
1328 of all recognized SCSI devices in /proc/scsi::
1330 >cat /proc/scsi/scsi
1332 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1333 Vendor: IBM Model: DGHS09U Rev: 03E0
1334 Type: Direct-Access ANSI SCSI revision: 03
1335 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1336 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1337 Type: CD-ROM ANSI SCSI revision: 02
1340 The directory named after the driver has one file for each adapter found in
1341 the system. These files contain information about the controller, including
1342 the used IRQ and the IO address range. The amount of information shown is
1343 dependent on the adapter you use. The example shows the output for an Adaptec
1344 AHA-2940 SCSI adapter::
1346 > cat /proc/scsi/aic7xxx/0
1348 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1350 TCQ Enabled By Default : Disabled
1351 AIC7XXX_PROC_STATS : Disabled
1352 AIC7XXX_RESET_DELAY : 5
1353 Adapter Configuration:
1354 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1355 Ultra Wide Controller
1356 PCI MMAPed I/O Base: 0xeb001000
1357 Adapter SEEPROM Config: SEEPROM found and used.
1358 Adaptec SCSI BIOS: Enabled
1360 SCBs: Active 0, Max Active 2,
1361 Allocated 15, HW 16, Page 255
1363 BIOS Control Word: 0x18b6
1364 Adapter Control Word: 0x005b
1365 Extended Translation: Enabled
1366 Disconnect Enable Flags: 0xffff
1367 Ultra Enable Flags: 0x0001
1368 Tag Queue Enable Flags: 0x0000
1369 Ordered Queue Tag Flags: 0x0000
1370 Default Tag Queue Depth: 8
1371 Tagged Queue By Device array for aic7xxx host instance 0:
1372 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1373 Actual queue depth per device for aic7xxx host instance 0:
1374 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1377 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1378 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1379 Total transfers 160151 (74577 reads and 85574 writes)
1381 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1382 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1383 Total transfers 0 (0 reads and 0 writes)
1386 1.6 Parallel port info in /proc/parport
1387 ---------------------------------------
1389 The directory /proc/parport contains information about the parallel ports of
1390 your system. It has one subdirectory for each port, named after the port
1393 These directories contain the four files shown in Table 1-10.
1396 .. table:: Table 1-10: Files in /proc/parport
1398 ========= ====================================================================
1400 ========= ====================================================================
1401 autoprobe Any IEEE-1284 device ID information that has been acquired.
1402 devices list of the device drivers using that port. A + will appear by the
1403 name of the device currently using the port (it might not appear
1405 hardware Parallel port's base address, IRQ line and DMA channel.
1406 irq IRQ that parport is using for that port. This is in a separate
1407 file to allow you to alter it by writing a new value in (IRQ
1409 ========= ====================================================================
1411 1.7 TTY info in /proc/tty
1412 -------------------------
1414 Information about the available and actually used tty's can be found in the
1415 directory /proc/tty. You'll find entries for drivers and line disciplines in
1416 this directory, as shown in Table 1-11.
1419 .. table:: Table 1-11: Files in /proc/tty
1421 ============= ==============================================
1423 ============= ==============================================
1424 drivers list of drivers and their usage
1425 ldiscs registered line disciplines
1426 driver/serial usage statistic and status of single tty lines
1427 ============= ==============================================
1429 To see which tty's are currently in use, you can simply look into the file
1432 > cat /proc/tty/drivers
1433 pty_slave /dev/pts 136 0-255 pty:slave
1434 pty_master /dev/ptm 128 0-255 pty:master
1435 pty_slave /dev/ttyp 3 0-255 pty:slave
1436 pty_master /dev/pty 2 0-255 pty:master
1437 serial /dev/cua 5 64-67 serial:callout
1438 serial /dev/ttyS 4 64-67 serial
1439 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1440 /dev/ptmx /dev/ptmx 5 2 system
1441 /dev/console /dev/console 5 1 system:console
1442 /dev/tty /dev/tty 5 0 system:/dev/tty
1443 unknown /dev/tty 4 1-63 console
1446 1.8 Miscellaneous kernel statistics in /proc/stat
1447 -------------------------------------------------
1449 Various pieces of information about kernel activity are available in the
1450 /proc/stat file. All of the numbers reported in this file are aggregates
1451 since the system first booted. For a quick look, simply cat the file::
1454 cpu 2255 34 2290 22625563 6290 127 456 0 0 0
1455 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1456 cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1457 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1463 softirq 183433 0 21755 12 39 1137 231 21459 2263
1465 The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1466 lines. These numbers identify the amount of time the CPU has spent performing
1467 different kinds of work. Time units are in USER_HZ (typically hundredths of a
1468 second). The meanings of the columns are as follows, from left to right:
1470 - user: normal processes executing in user mode
1471 - nice: niced processes executing in user mode
1472 - system: processes executing in kernel mode
1473 - idle: twiddling thumbs
1474 - iowait: In a word, iowait stands for waiting for I/O to complete. But there
1475 are several problems:
1477 1. CPU will not wait for I/O to complete, iowait is the time that a task is
1478 waiting for I/O to complete. When CPU goes into idle state for
1479 outstanding task I/O, another task will be scheduled on this CPU.
1480 2. In a multi-core CPU, the task waiting for I/O to complete is not running
1481 on any CPU, so the iowait of each CPU is difficult to calculate.
1482 3. The value of iowait field in /proc/stat will decrease in certain
1485 So, the iowait is not reliable by reading from /proc/stat.
1486 - irq: servicing interrupts
1487 - softirq: servicing softirqs
1488 - steal: involuntary wait
1489 - guest: running a normal guest
1490 - guest_nice: running a niced guest
1492 The "intr" line gives counts of interrupts serviced since boot time, for each
1493 of the possible system interrupts. The first column is the total of all
1494 interrupts serviced including unnumbered architecture specific interrupts;
1495 each subsequent column is the total for that particular numbered interrupt.
1496 Unnumbered interrupts are not shown, only summed into the total.
1498 The "ctxt" line gives the total number of context switches across all CPUs.
1500 The "btime" line gives the time at which the system booted, in seconds since
1503 The "processes" line gives the number of processes and threads created, which
1504 includes (but is not limited to) those created by calls to the fork() and
1505 clone() system calls.
1507 The "procs_running" line gives the total number of threads that are
1508 running or ready to run (i.e., the total number of runnable threads).
1510 The "procs_blocked" line gives the number of processes currently blocked,
1511 waiting for I/O to complete.
1513 The "softirq" line gives counts of softirqs serviced since boot time, for each
1514 of the possible system softirqs. The first column is the total of all
1515 softirqs serviced; each subsequent column is the total for that particular
1519 1.9 Ext4 file system parameters
1520 -------------------------------
1522 Information about mounted ext4 file systems can be found in
1523 /proc/fs/ext4. Each mounted filesystem will have a directory in
1524 /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1525 /proc/fs/ext4/dm-0). The files in each per-device directory are shown
1526 in Table 1-12, below.
1528 .. table:: Table 1-12: Files in /proc/fs/ext4/<devname>
1530 ============== ==========================================================
1532 mb_groups details of multiblock allocator buddy cache of free blocks
1533 ============== ==========================================================
1537 Shows registered system console lines.
1539 To see which character device lines are currently used for the system console
1540 /dev/console, you may simply look into the file /proc/consoles::
1542 > cat /proc/consoles
1548 +--------------------+-------------------------------------------------------+
1549 | device | name of the device |
1550 +====================+=======================================================+
1551 | operations | * R = can do read operations |
1552 | | * W = can do write operations |
1553 | | * U = can do unblank |
1554 +--------------------+-------------------------------------------------------+
1555 | flags | * E = it is enabled |
1556 | | * C = it is preferred console |
1557 | | * B = it is primary boot console |
1558 | | * p = it is used for printk buffer |
1559 | | * b = it is not a TTY but a Braille device |
1560 | | * a = it is safe to use when cpu is offline |
1561 +--------------------+-------------------------------------------------------+
1562 | major:minor | major and minor number of the device separated by a |
1564 +--------------------+-------------------------------------------------------+
1569 The /proc file system serves information about the running system. It not only
1570 allows access to process data but also allows you to request the kernel status
1571 by reading files in the hierarchy.
1573 The directory structure of /proc reflects the types of information and makes
1574 it easy, if not obvious, where to look for specific data.
1576 Chapter 2: Modifying System Parameters
1577 ======================================
1582 * Modifying kernel parameters by writing into files found in /proc/sys
1583 * Exploring the files which modify certain parameters
1584 * Review of the /proc/sys file tree
1586 ------------------------------------------------------------------------------
1588 A very interesting part of /proc is the directory /proc/sys. This is not only
1589 a source of information, it also allows you to change parameters within the
1590 kernel. Be very careful when attempting this. You can optimize your system,
1591 but you can also cause it to crash. Never alter kernel parameters on a
1592 production system. Set up a development machine and test to make sure that
1593 everything works the way you want it to. You may have no alternative but to
1594 reboot the machine once an error has been made.
1596 To change a value, simply echo the new value into the file.
1597 You need to be root to do this. You can create your own boot script
1598 to perform this every time your system boots.
1600 The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1601 general things in the operation of the Linux kernel. Since some of the files
1602 can inadvertently disrupt your system, it is advisable to read both
1603 documentation and source before actually making adjustments. In any case, be
1604 very careful when writing to any of these files. The entries in /proc may
1605 change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1606 review the kernel documentation in the directory /usr/src/linux/Documentation.
1607 This chapter is heavily based on the documentation included in the pre 2.2
1608 kernels, and became part of it in version 2.2.1 of the Linux kernel.
1610 Please see: Documentation/admin-guide/sysctl/ directory for descriptions of these
1616 Certain aspects of kernel behavior can be modified at runtime, without the
1617 need to recompile the kernel, or even to reboot the system. The files in the
1618 /proc/sys tree can not only be read, but also modified. You can use the echo
1619 command to write value into these files, thereby changing the default settings
1623 Chapter 3: Per-process Parameters
1624 =================================
1626 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1627 --------------------------------------------------------------------------------
1629 These files can be used to adjust the badness heuristic used to select which
1630 process gets killed in out of memory (oom) conditions.
1632 The badness heuristic assigns a value to each candidate task ranging from 0
1633 (never kill) to 1000 (always kill) to determine which process is targeted. The
1634 units are roughly a proportion along that range of allowed memory the process
1635 may allocate from based on an estimation of its current memory and swap use.
1636 For example, if a task is using all allowed memory, its badness score will be
1637 1000. If it is using half of its allowed memory, its score will be 500.
1639 The amount of "allowed" memory depends on the context in which the oom killer
1640 was called. If it is due to the memory assigned to the allocating task's cpuset
1641 being exhausted, the allowed memory represents the set of mems assigned to that
1642 cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1643 memory represents the set of mempolicy nodes. If it is due to a memory
1644 limit (or swap limit) being reached, the allowed memory is that configured
1645 limit. Finally, if it is due to the entire system being out of memory, the
1646 allowed memory represents all allocatable resources.
1648 The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1649 is used to determine which task to kill. Acceptable values range from -1000
1650 (OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1651 polarize the preference for oom killing either by always preferring a certain
1652 task or completely disabling it. The lowest possible value, -1000, is
1653 equivalent to disabling oom killing entirely for that task since it will always
1654 report a badness score of 0.
1656 Consequently, it is very simple for userspace to define the amount of memory to
1657 consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1658 example, is roughly equivalent to allowing the remainder of tasks sharing the
1659 same system, cpuset, mempolicy, or memory controller resources to use at least
1660 50% more memory. A value of -500, on the other hand, would be roughly
1661 equivalent to discounting 50% of the task's allowed memory from being considered
1662 as scoring against the task.
1664 For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1665 be used to tune the badness score. Its acceptable values range from -16
1666 (OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1667 (OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1668 scaled linearly with /proc/<pid>/oom_score_adj.
1670 The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1671 value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1672 requires CAP_SYS_RESOURCE.
1675 3.2 /proc/<pid>/oom_score - Display current oom-killer score
1676 -------------------------------------------------------------
1678 This file can be used to check the current score used by the oom-killer for
1679 any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1680 process should be killed in an out-of-memory situation.
1682 Please note that the exported value includes oom_score_adj so it is
1683 effectively in range [0,2000].
1686 3.3 /proc/<pid>/io - Display the IO accounting fields
1687 -------------------------------------------------------
1689 This file contains IO statistics for each running process.
1696 test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1699 test:/tmp # cat /proc/3828/io
1705 write_bytes: 323932160
1706 cancelled_write_bytes: 0
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
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.
1734 I/O counter: read syscalls
1735 Attempt to count the number of read I/O operations, i.e. syscalls like read()
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().
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>
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
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.
1833 $ echo 0x7 > /proc/self/coredump_filter
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.rst
1876 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1877 --------------------------------------------------------
1878 These files provide a method to access a task's 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
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
1891 Note the "first level" here -- if a child has its 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 needs 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
1912 A typical output is::
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.
1935 where 'eventfd-count' is hex value of a counter.
1945 sigmask: 0000000000000200
1947 where 'sigmask' is hex value of the signal mask associated
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.
1970 For inotify files the format is the following::
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, i.e. 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
1986 If the kernel is built without exportfs support the file handle won't be
1989 If there is no inotify mark attached yet the 'inotify' line will be omitted.
1991 For fanotify files the format is::
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' and '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 are in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
2006 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.
2023 it_value: (0, 49406829)
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 expiration.
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
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 an 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 tradeoff to be
2065 Writing 0 to the file will set the task's 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
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
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.
2099 $ cat /proc/6753/arch_status
2100 AVX512_elapsed_ms: 8
2105 x86 specific entries
2106 ~~~~~~~~~~~~~~~~~~~~~
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
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 Chapter 4: Configuring procfs
2135 =============================
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 subset= Show only the specified subset of procfs.
2146 ========= ========================================================
2148 hidepid=off or hidepid=0 means classic mode - everybody may access all
2149 /proc/<pid>/ directories (default).
2151 hidepid=noaccess or hidepid=1 means users may not access any /proc/<pid>/
2152 directories but their own. Sensitive files like cmdline, sched*, status are now
2153 protected against other users. This makes it impossible to learn whether any
2154 user runs specific program (given the program doesn't reveal itself by its
2155 behaviour). As an additional bonus, as /proc/<pid>/cmdline is unaccessible for
2156 other users, poorly written programs passing sensitive information via program
2157 arguments are now protected against local eavesdroppers.
2159 hidepid=invisible or hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be
2160 fully invisible to other users. It doesn't mean that it hides a fact whether a
2161 process with a specific pid value exists (it can be learned by other means, e.g.
2162 by "kill -0 $PID"), but it hides process' uid and gid, which may be learned by
2163 stat()'ing /proc/<pid>/ otherwise. It greatly complicates an intruder's task of
2164 gathering information about running processes, whether some daemon runs with
2165 elevated privileges, whether other user runs some sensitive program, whether
2166 other users run any program at all, etc.
2168 hidepid=ptraceable or hidepid=4 means that procfs should only contain
2169 /proc/<pid>/ directories that the caller can ptrace.
2171 gid= defines a group authorized to learn processes information otherwise
2172 prohibited by hidepid=. If you use some daemon like identd which needs to learn
2173 information about processes information, just add identd to this group.
2175 subset=pid hides all top level files and directories in the procfs that
2176 are not related to tasks.
2178 Chapter 5: Filesystem behavior
2179 ==============================
2181 Originally, before the advent of pid namepsace, procfs was a global file
2182 system. It means that there was only one procfs instance in the system.
2184 When pid namespace was added, a separate procfs instance was mounted in
2185 each pid namespace. So, procfs mount options are global among all
2186 mountpoints within the same namespace::
2188 # grep ^proc /proc/mounts
2189 proc /proc proc rw,relatime,hidepid=2 0 0
2191 # strace -e mount mount -o hidepid=1 -t proc proc /tmp/proc
2192 mount("proc", "/tmp/proc", "proc", 0, "hidepid=1") = 0
2193 +++ exited with 0 +++
2195 # grep ^proc /proc/mounts
2196 proc /proc proc rw,relatime,hidepid=2 0 0
2197 proc /tmp/proc proc rw,relatime,hidepid=2 0 0
2199 and only after remounting procfs mount options will change at all
2202 # mount -o remount,hidepid=1 -t proc proc /tmp/proc
2204 # grep ^proc /proc/mounts
2205 proc /proc proc rw,relatime,hidepid=1 0 0
2206 proc /tmp/proc proc rw,relatime,hidepid=1 0 0
2208 This behavior is different from the behavior of other filesystems.
2210 The new procfs behavior is more like other filesystems. Each procfs mount
2211 creates a new procfs instance. Mount options affect own procfs instance.
2212 It means that it became possible to have several procfs instances
2213 displaying tasks with different filtering options in one pid namespace::
2215 # mount -o hidepid=invisible -t proc proc /proc
2216 # mount -o hidepid=noaccess -t proc proc /tmp/proc
2217 # grep ^proc /proc/mounts
2218 proc /proc proc rw,relatime,hidepid=invisible 0 0
2219 proc /tmp/proc proc rw,relatime,hidepid=noaccess 0 0
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