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 a 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 voluntary_ctxt_switches: 0
214 nonvoluntary_ctxt_switches: 1
216 This shows you nearly the same information you would get if you viewed it with
217 the ps command. In fact, ps uses the proc file system to obtain its
218 information. But you get a more detailed view of the process by reading the
219 file /proc/PID/status. It fields are described in table 1-2.
221 The statm file contains more detailed information about the process
222 memory usage. Its seven fields are explained in Table 1-3. The stat file
223 contains details information about the process itself. Its fields are
224 explained in Table 1-4.
226 (for SMP CONFIG users)
228 For making accounting scalable, RSS related information are handled in an
229 asynchronous manner and the value may not be very precise. To see a precise
230 snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
231 It's slow but very precise.
233 .. table:: Table 1-2: Contents of the status files (as of 4.19)
235 ========================== ===================================================
237 ========================== ===================================================
238 Name filename of the executable
239 Umask file mode creation mask
240 State state (R is running, S is sleeping, D is sleeping
241 in an uninterruptible wait, Z is zombie,
242 T is traced or stopped)
244 Ngid NUMA group ID (0 if none)
246 PPid process id of the parent process
247 TracerPid PID of process tracing this process (0 if not)
248 Uid Real, effective, saved set, and file system UIDs
249 Gid Real, effective, saved set, and file system GIDs
250 FDSize number of file descriptor slots currently allocated
251 Groups supplementary group list
252 NStgid descendant namespace thread group ID hierarchy
253 NSpid descendant namespace process ID hierarchy
254 NSpgid descendant namespace process group ID hierarchy
255 NSsid descendant namespace session ID hierarchy
256 VmPeak peak virtual memory size
257 VmSize total program size
258 VmLck locked memory size
259 VmPin pinned memory size
260 VmHWM peak resident set size ("high water mark")
261 VmRSS size of memory portions. It contains the three
263 (VmRSS = RssAnon + RssFile + RssShmem)
264 RssAnon size of resident anonymous memory
265 RssFile size of resident file mappings
266 RssShmem size of resident shmem memory (includes SysV shm,
267 mapping of tmpfs and shared anonymous mappings)
268 VmData size of private data segments
269 VmStk size of stack segments
270 VmExe size of text segment
271 VmLib size of shared library code
272 VmPTE size of page table entries
273 VmSwap amount of swap used by anonymous private data
274 (shmem swap usage is not included)
275 HugetlbPages size of hugetlb memory portions
276 CoreDumping process's memory is currently being dumped
277 (killing the process may lead to a corrupted core)
278 THP_enabled process is allowed to use THP (returns 0 when
279 PR_SET_THP_DISABLE is set on the process
280 Threads number of threads
281 SigQ number of signals queued/max. number for queue
282 SigPnd bitmap of pending signals for the thread
283 ShdPnd bitmap of shared pending signals for the process
284 SigBlk bitmap of blocked signals
285 SigIgn bitmap of ignored signals
286 SigCgt bitmap of caught signals
287 CapInh bitmap of inheritable capabilities
288 CapPrm bitmap of permitted capabilities
289 CapEff bitmap of effective capabilities
290 CapBnd bitmap of capabilities bounding set
291 CapAmb bitmap of ambient capabilities
292 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
293 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
294 Speculation_Store_Bypass speculative store bypass mitigation status
295 Cpus_allowed mask of CPUs on which this process may run
296 Cpus_allowed_list Same as previous, but in "list format"
297 Mems_allowed mask of memory nodes allowed to this process
298 Mems_allowed_list Same as previous, but in "list format"
299 voluntary_ctxt_switches number of voluntary context switches
300 nonvoluntary_ctxt_switches number of non voluntary context switches
301 ========================== ===================================================
304 .. table:: Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
306 ======== =============================== ==============================
308 ======== =============================== ==============================
309 size total program size (pages) (same as VmSize in status)
310 resident size of memory portions (pages) (same as VmRSS in status)
311 shared number of pages that are shared (i.e. backed by a file, same
312 as RssFile+RssShmem in status)
313 trs number of pages that are 'code' (not including libs; broken,
314 includes data segment)
315 lrs number of pages of library (always 0 on 2.6)
316 drs number of pages of data/stack (including libs; broken,
317 includes library text)
318 dt number of dirty pages (always 0 on 2.6)
319 ======== =============================== ==============================
322 .. table:: Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
324 ============= ===============================================================
326 ============= ===============================================================
328 tcomm filename of the executable
329 state state (R is running, S is sleeping, D is sleeping in an
330 uninterruptible wait, Z is zombie, T is traced or stopped)
331 ppid process id of the parent process
332 pgrp pgrp of the process
334 tty_nr tty the process uses
335 tty_pgrp pgrp of the tty
337 min_flt number of minor faults
338 cmin_flt number of minor faults with child's
339 maj_flt number of major faults
340 cmaj_flt number of major faults with child's
341 utime user mode jiffies
342 stime kernel mode jiffies
343 cutime user mode jiffies with child's
344 cstime kernel mode jiffies with child's
345 priority priority level
347 num_threads number of threads
348 it_real_value (obsolete, always 0)
349 start_time time the process started after system boot
350 vsize virtual memory size
351 rss resident set memory size
352 rsslim current limit in bytes on the rss
353 start_code address above which program text can run
354 end_code address below which program text can run
355 start_stack address of the start of the main process stack
356 esp current value of ESP
357 eip current value of EIP
358 pending bitmap of pending signals
359 blocked bitmap of blocked signals
360 sigign bitmap of ignored signals
361 sigcatch bitmap of caught signals
362 0 (place holder, used to be the wchan address,
363 use /proc/PID/wchan instead)
366 exit_signal signal to send to parent thread on exit
367 task_cpu which CPU the task is scheduled on
368 rt_priority realtime priority
369 policy scheduling policy (man sched_setscheduler)
370 blkio_ticks time spent waiting for block IO
371 gtime guest time of the task in jiffies
372 cgtime guest time of the task children in jiffies
373 start_data address above which program data+bss is placed
374 end_data address below which program data+bss is placed
375 start_brk address above which program heap can be expanded with brk()
376 arg_start address above which program command line is placed
377 arg_end address below which program command line is placed
378 env_start address above which program environment is placed
379 env_end address below which program environment is placed
380 exit_code the thread's exit_code in the form reported by the waitpid
382 ============= ===============================================================
384 The /proc/PID/maps file contains the currently mapped memory regions and
385 their access permissions.
389 address perms offset dev inode pathname
391 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test
392 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
393 0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
394 a7cb1000-a7cb2000 ---p 00000000 00:00 0
395 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
396 a7eb2000-a7eb3000 ---p 00000000 00:00 0
397 a7eb3000-a7ed5000 rw-p 00000000 00:00 0
398 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
399 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
400 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
401 a800b000-a800e000 rw-p 00000000 00:00 0
402 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
403 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
404 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
405 a8024000-a8027000 rw-p 00000000 00:00 0
406 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
407 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
408 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
409 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
410 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
412 where "address" is the address space in the process that it occupies, "perms"
413 is a set of permissions::
419 p = private (copy on write)
421 "offset" is the offset into the mapping, "dev" is the device (major:minor), and
422 "inode" is the inode on that device. 0 indicates that no inode is associated
423 with the memory region, as the case would be with BSS (uninitialized data).
424 The "pathname" shows the name associated file for this mapping. If the mapping
425 is not associated with a file:
427 ======= ====================================
428 [heap] the heap of the program
429 [stack] the stack of the main process
430 [vdso] the "virtual dynamic shared object",
431 the kernel system call handler
432 ======= ====================================
434 or if empty, the mapping is anonymous.
436 The /proc/PID/smaps is an extension based on maps, showing the memory
437 consumption for each of the process's mappings. For each mapping (aka Virtual
438 Memory Area, or VMA) there is a series of lines such as the following::
440 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
457 Private_Hugetlb: 0 kB
464 VmFlags: rd ex mr mw me dw
466 The first of these lines shows the same information as is displayed for the
467 mapping in /proc/PID/maps. Following lines show the size of the mapping
468 (size); the size of each page allocated when backing a VMA (KernelPageSize),
469 which is usually the same as the size in the page table entries; the page size
470 used by the MMU when backing a VMA (in most cases, the same as KernelPageSize);
471 the amount of the mapping that is currently resident in RAM (RSS); the
472 process' proportional share of this mapping (PSS); and the number of clean and
473 dirty shared and private pages in the mapping.
475 The "proportional set size" (PSS) of a process is the count of pages it has
476 in memory, where each page is divided by the number of processes sharing it.
477 So if a process has 1000 pages all to itself, and 1000 shared with one other
478 process, its PSS will be 1500.
480 Note that even a page which is part of a MAP_SHARED mapping, but has only
481 a single pte mapped, i.e. is currently used by only one process, is accounted
482 as private and not as shared.
484 "Referenced" indicates the amount of memory currently marked as referenced or
487 "Anonymous" shows the amount of memory that does not belong to any file. Even
488 a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
489 and a page is modified, the file page is replaced by a private anonymous copy.
491 "LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE).
492 The memory isn't freed immediately with madvise(). It's freed in memory
493 pressure if the memory is clean. Please note that the printed value might
494 be lower than the real value due to optimizations used in the current
495 implementation. If this is not desirable please file a bug report.
497 "AnonHugePages" shows the ammount of memory backed by transparent hugepage.
499 "ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by
502 "Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
503 hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
504 reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
506 "Swap" shows how much would-be-anonymous memory is also used, but out on swap.
508 For shmem mappings, "Swap" includes also the size of the mapped (and not
509 replaced by copy-on-write) part of the underlying shmem object out on swap.
510 "SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
511 does not take into account swapped out page of underlying shmem objects.
512 "Locked" indicates whether the mapping is locked in memory or not.
513 "THPeligible" indicates whether the mapping is eligible for allocating THP
514 pages - 1 if true, 0 otherwise. It just shows the current status.
516 "VmFlags" field deserves a separate description. This member represents the
517 kernel flags associated with the particular virtual memory area in two letter
518 encoded manner. The codes are the following:
520 == =======================================
529 gd stack segment growns down
531 dw disabled write to the mapped file
532 lo pages are locked in memory
533 io memory mapped I/O area
534 sr sequential read advise provided
535 rr random read advise provided
536 dc do not copy area on fork
537 de do not expand area on remapping
538 ac area is accountable
539 nr swap space is not reserved for the area
540 ht area uses huge tlb pages
541 ar architecture specific flag
542 dd do not include area into core dump
545 hg huge page advise flag
546 nh no huge page advise flag
547 mg mergable advise flag
548 bt - arm64 BTI guarded page
549 == =======================================
551 Note that there is no guarantee that every flag and associated mnemonic will
552 be present in all further kernel releases. Things get changed, the flags may
553 be vanished or the reverse -- new added. Interpretation of their meaning
554 might change in future as well. So each consumer of these flags has to
555 follow each specific kernel version for the exact semantic.
557 This file is only present if the CONFIG_MMU kernel configuration option is
560 Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent
561 output can be achieved only in the single read call).
563 This typically manifests when doing partial reads of these files while the
564 memory map is being modified. Despite the races, we do provide the following
567 1) The mapped addresses never go backwards, which implies no two
568 regions will ever overlap.
569 2) If there is something at a given vaddr during the entirety of the
570 life of the smaps/maps walk, there will be some output for it.
572 The /proc/PID/smaps_rollup file includes the same fields as /proc/PID/smaps,
573 but their values are the sums of the corresponding values for all mappings of
574 the process. Additionally, it contains these fields:
580 They represent the proportional shares of anonymous, file, and shmem pages, as
581 described for smaps above. These fields are omitted in smaps since each
582 mapping identifies the type (anon, file, or shmem) of all pages it contains.
583 Thus all information in smaps_rollup can be derived from smaps, but at a
584 significantly higher cost.
586 The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
587 bits on both physical and virtual pages associated with a process, and the
588 soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst
590 To clear the bits for all the pages associated with the process::
592 > echo 1 > /proc/PID/clear_refs
594 To clear the bits for the anonymous pages associated with the process::
596 > echo 2 > /proc/PID/clear_refs
598 To clear the bits for the file mapped pages associated with the process::
600 > echo 3 > /proc/PID/clear_refs
602 To clear the soft-dirty bit::
604 > echo 4 > /proc/PID/clear_refs
606 To reset the peak resident set size ("high water mark") to the process's
609 > echo 5 > /proc/PID/clear_refs
611 Any other value written to /proc/PID/clear_refs will have no effect.
613 The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
614 using /proc/kpageflags and number of times a page is mapped using
615 /proc/kpagecount. For detailed explanation, see
616 Documentation/admin-guide/mm/pagemap.rst.
618 The /proc/pid/numa_maps is an extension based on maps, showing the memory
619 locality and binding policy, as well as the memory usage (in pages) of
620 each mapping. The output follows a general format where mapping details get
621 summarized separated by blank spaces, one mapping per each file line::
623 address policy mapping details
625 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
626 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
627 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
628 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
629 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
630 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
631 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
632 320698b000 default file=/lib64/libc-2.12.so
633 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
634 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
635 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
636 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
637 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
638 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
639 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
640 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
644 "address" is the starting address for the mapping;
646 "policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst);
648 "mapping details" summarizes mapping data such as mapping type, page usage counters,
649 node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
650 size, in KB, that is backing the mapping up.
655 Similar to the process entries, the kernel data files give information about
656 the running kernel. The files used to obtain this information are contained in
657 /proc and are listed in Table 1-5. Not all of these will be present in your
658 system. It depends on the kernel configuration and the loaded modules, which
659 files are there, and which are missing.
661 .. table:: Table 1-5: Kernel info in /proc
663 ============ ===============================================================
665 ============ ===============================================================
666 apm Advanced power management info
667 buddyinfo Kernel memory allocator information (see text) (2.5)
668 bus Directory containing bus specific information
669 cmdline Kernel command line
670 cpuinfo Info about the CPU
671 devices Available devices (block and character)
672 dma Used DMS channels
673 filesystems Supported filesystems
674 driver Various drivers grouped here, currently rtc (2.4)
675 execdomains Execdomains, related to security (2.4)
676 fb Frame Buffer devices (2.4)
677 fs File system parameters, currently nfs/exports (2.4)
678 ide Directory containing info about the IDE subsystem
679 interrupts Interrupt usage
680 iomem Memory map (2.4)
681 ioports I/O port usage
682 irq Masks for irq to cpu affinity (2.4)(smp?)
683 isapnp ISA PnP (Plug&Play) Info (2.4)
684 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
686 ksyms Kernel symbol table
687 loadavg Load average of last 1, 5 & 15 minutes
691 modules List of loaded modules
692 mounts Mounted filesystems
693 net Networking info (see text)
694 pagetypeinfo Additional page allocator information (see text) (2.5)
695 partitions Table of partitions known to the system
696 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
697 decoupled by lspci (2.4)
699 scsi SCSI info (see text)
700 slabinfo Slab pool info
701 softirqs softirq usage
702 stat Overall statistics
703 swaps Swap space utilization
705 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
706 tty Info of tty drivers
707 uptime Wall clock since boot, combined idle time of all cpus
708 version Kernel version
709 video bttv info of video resources (2.4)
710 vmallocinfo Show vmalloced areas
711 ============ ===============================================================
713 You can, for example, check which interrupts are currently in use and what
714 they are used for by looking in the file /proc/interrupts::
716 > cat /proc/interrupts
718 0: 8728810 XT-PIC timer
719 1: 895 XT-PIC keyboard
721 3: 531695 XT-PIC aha152x
722 4: 2014133 XT-PIC serial
723 5: 44401 XT-PIC pcnet_cs
726 12: 182918 XT-PIC PS/2 Mouse
728 14: 1232265 XT-PIC ide0
732 In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
733 output of a SMP machine)::
735 > cat /proc/interrupts
738 0: 1243498 1214548 IO-APIC-edge timer
739 1: 8949 8958 IO-APIC-edge keyboard
740 2: 0 0 XT-PIC cascade
741 5: 11286 10161 IO-APIC-edge soundblaster
742 8: 1 0 IO-APIC-edge rtc
743 9: 27422 27407 IO-APIC-edge 3c503
744 12: 113645 113873 IO-APIC-edge PS/2 Mouse
746 14: 22491 24012 IO-APIC-edge ide0
747 15: 2183 2415 IO-APIC-edge ide1
748 17: 30564 30414 IO-APIC-level eth0
749 18: 177 164 IO-APIC-level bttv
754 NMI is incremented in this case because every timer interrupt generates a NMI
755 (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
757 LOC is the local interrupt counter of the internal APIC of every CPU.
759 ERR is incremented in the case of errors in the IO-APIC bus (the bus that
760 connects the CPUs in a SMP system. This means that an error has been detected,
761 the IO-APIC automatically retry the transmission, so it should not be a big
762 problem, but you should read the SMP-FAQ.
764 In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
765 /proc/interrupts to display every IRQ vector in use by the system, not
766 just those considered 'most important'. The new vectors are:
769 interrupt raised when a machine check threshold counter
770 (typically counting ECC corrected errors of memory or cache) exceeds
771 a configurable threshold. Only available on some systems.
774 a thermal event interrupt occurs when a temperature threshold
775 has been exceeded for the CPU. This interrupt may also be generated
776 when the temperature drops back to normal.
779 a spurious interrupt is some interrupt that was raised then lowered
780 by some IO device before it could be fully processed by the APIC. Hence
781 the APIC sees the interrupt but does not know what device it came from.
782 For this case the APIC will generate the interrupt with a IRQ vector
783 of 0xff. This might also be generated by chipset bugs.
786 rescheduling, call and TLB flush interrupts are
787 sent from one CPU to another per the needs of the OS. Typically,
788 their statistics are used by kernel developers and interested users to
789 determine the occurrence of interrupts of the given type.
791 The above IRQ vectors are displayed only when relevant. For example,
792 the threshold vector does not exist on x86_64 platforms. Others are
793 suppressed when the system is a uniprocessor. As of this writing, only
794 i386 and x86_64 platforms support the new IRQ vector displays.
796 Of some interest is the introduction of the /proc/irq directory to 2.4.
797 It could be used to set IRQ to CPU affinity, this means that you can "hook" an
798 IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
799 irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
805 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
806 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
810 smp_affinity is a bitmask, in which you can specify which CPUs can handle the
811 IRQ, you can set it by doing::
813 > echo 1 > /proc/irq/10/smp_affinity
815 This means that only the first CPU will handle the IRQ, but you can also echo
816 5 which means that only the first and third CPU can handle the IRQ.
818 The contents of each smp_affinity file is the same by default::
820 > cat /proc/irq/0/smp_affinity
823 There is an alternate interface, smp_affinity_list which allows specifying
824 a cpu range instead of a bitmask::
826 > cat /proc/irq/0/smp_affinity_list
829 The default_smp_affinity mask applies to all non-active IRQs, which are the
830 IRQs which have not yet been allocated/activated, and hence which lack a
831 /proc/irq/[0-9]* directory.
833 The node file on an SMP system shows the node to which the device using the IRQ
834 reports itself as being attached. This hardware locality information does not
835 include information about any possible driver locality preference.
837 prof_cpu_mask specifies which CPUs are to be profiled by the system wide
838 profiler. Default value is ffffffff (all cpus if there are only 32 of them).
840 The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
841 between all the CPUs which are allowed to handle it. As usual the kernel has
842 more info than you and does a better job than you, so the defaults are the
843 best choice for almost everyone. [Note this applies only to those IO-APIC's
844 that support "Round Robin" interrupt distribution.]
846 There are three more important subdirectories in /proc: net, scsi, and sys.
847 The general rule is that the contents, or even the existence of these
848 directories, depend on your kernel configuration. If SCSI is not enabled, the
849 directory scsi may not exist. The same is true with the net, which is there
850 only when networking support is present in the running kernel.
852 The slabinfo file gives information about memory usage at the slab level.
853 Linux uses slab pools for memory management above page level in version 2.2.
854 Commonly used objects have their own slab pool (such as network buffers,
855 directory cache, and so on).
859 > cat /proc/buddyinfo
861 Node 0, zone DMA 0 4 5 4 4 3 ...
862 Node 0, zone Normal 1 0 0 1 101 8 ...
863 Node 0, zone HighMem 2 0 0 1 1 0 ...
865 External fragmentation is a problem under some workloads, and buddyinfo is a
866 useful tool for helping diagnose these problems. Buddyinfo will give you a
867 clue as to how big an area you can safely allocate, or why a previous
870 Each column represents the number of pages of a certain order which are
871 available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
872 ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
873 available in ZONE_NORMAL, etc...
875 More information relevant to external fragmentation can be found in
878 > cat /proc/pagetypeinfo
882 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
883 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
884 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
885 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
886 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
887 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
888 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
889 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
890 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
891 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
892 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
894 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
895 Node 0, zone DMA 2 0 5 1 0
896 Node 0, zone DMA32 41 6 967 2 0
898 Fragmentation avoidance in the kernel works by grouping pages of different
899 migrate types into the same contiguous regions of memory called page blocks.
900 A page block is typically the size of the default hugepage size e.g. 2MB on
901 X86-64. By keeping pages grouped based on their ability to move, the kernel
902 can reclaim pages within a page block to satisfy a high-order allocation.
904 The pagetypinfo begins with information on the size of a page block. It
905 then gives the same type of information as buddyinfo except broken down
906 by migrate-type and finishes with details on how many page blocks of each
909 If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
910 from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
911 make an estimate of the likely number of huge pages that can be allocated
912 at a given point in time. All the "Movable" blocks should be allocatable
913 unless memory has been mlock()'d. Some of the Reclaimable blocks should
914 also be allocatable although a lot of filesystem metadata may have to be
915 reclaimed to achieve this.
921 Provides information about distribution and utilization of memory. This
922 varies by architecture and compile options. The following is from a
923 16GB PIII, which has highmem enabled. You may not have all of these fields.
929 MemTotal: 16344972 kB
931 MemAvailable: 14836172 kB
937 HighTotal: 15597528 kB
938 HighFree: 13629632 kB
948 KReclaimable: 168048 kB
950 SReclaimable: 159856 kB
951 SUnreclaim: 124508 kB
956 CommitLimit: 7669796 kB
957 Committed_AS: 100056 kB
958 VmallocTotal: 112216 kB
960 VmallocChunk: 111088 kB
962 HardwareCorrupted: 0 kB
963 AnonHugePages: 49152 kB
968 Total usable ram (i.e. physical ram minus a few reserved
969 bits and the kernel binary code)
971 The sum of LowFree+HighFree
973 An estimate of how much memory is available for starting new
974 applications, without swapping. Calculated from MemFree,
975 SReclaimable, the size of the file LRU lists, and the low
976 watermarks in each zone.
977 The estimate takes into account that the system needs some
978 page cache to function well, and that not all reclaimable
979 slab will be reclaimable, due to items being in use. The
980 impact of those factors will vary from system to system.
982 Relatively temporary storage for raw disk blocks
983 shouldn't get tremendously large (20MB or so)
985 in-memory cache for files read from the disk (the
986 pagecache). Doesn't include SwapCached
988 Memory that once was swapped out, is swapped back in but
989 still also is in the swapfile (if memory is needed it
990 doesn't need to be swapped out AGAIN because it is already
991 in the swapfile. This saves I/O)
993 Memory that has been used more recently and usually not
994 reclaimed unless absolutely necessary.
996 Memory which has been less recently used. It is more
997 eligible to be reclaimed for other purposes
999 Highmem is all memory above ~860MB of physical memory
1000 Highmem areas are for use by userspace programs, or
1001 for the pagecache. The kernel must use tricks to access
1002 this memory, making it slower to access than lowmem.
1004 Lowmem is memory which can be used for everything that
1005 highmem can be used for, but it is also available for the
1006 kernel's use for its own data structures. Among many
1007 other things, it is where everything from the Slab is
1008 allocated. Bad things happen when you're out of lowmem.
1010 total amount of swap space available
1012 Memory which has been evicted from RAM, and is temporarily
1015 Memory which is waiting to get written back to the disk
1017 Memory which is actively being written back to the disk
1019 Non-file backed pages mapped into userspace page tables
1021 The amount of RAM/memory in KB, the kernel identifies as
1024 Non-file backed huge pages mapped into userspace page tables
1026 files which have been mmaped, such as libraries
1028 Total memory used by shared memory (shmem) and tmpfs
1030 Memory used by shared memory (shmem) and tmpfs allocated
1033 Shared memory mapped into userspace with huge pages
1035 Kernel allocations that the kernel will attempt to reclaim
1036 under memory pressure. Includes SReclaimable (below), and other
1037 direct allocations with a shrinker.
1039 in-kernel data structures cache
1041 Part of Slab, that might be reclaimed, such as caches
1043 Part of Slab, that cannot be reclaimed on memory pressure
1045 amount of memory dedicated to the lowest level of page
1048 Always zero. Previous counted pages which had been written to
1049 the server, but has not been committed to stable storage.
1051 Memory used for block device "bounce buffers"
1053 Memory used by FUSE for temporary writeback buffers
1055 Based on the overcommit ratio ('vm.overcommit_ratio'),
1056 this is the total amount of memory currently available to
1057 be allocated on the system. This limit is only adhered to
1058 if strict overcommit accounting is enabled (mode 2 in
1059 'vm.overcommit_memory').
1061 The CommitLimit is calculated with the following formula::
1063 CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
1064 overcommit_ratio / 100 + [total swap pages]
1066 For example, on a system with 1G of physical RAM and 7G
1067 of swap with a `vm.overcommit_ratio` of 30 it would
1068 yield a CommitLimit of 7.3G.
1070 For more details, see the memory overcommit documentation
1071 in vm/overcommit-accounting.
1073 The amount of memory presently allocated on the system.
1074 The committed memory is a sum of all of the memory which
1075 has been allocated by processes, even if it has not been
1076 "used" by them as of yet. A process which malloc()'s 1G
1077 of memory, but only touches 300M of it will show up as
1078 using 1G. This 1G is memory which has been "committed" to
1079 by the VM and can be used at any time by the allocating
1080 application. With strict overcommit enabled on the system
1081 (mode 2 in 'vm.overcommit_memory'),allocations which would
1082 exceed the CommitLimit (detailed above) will not be permitted.
1083 This is useful if one needs to guarantee that processes will
1084 not fail due to lack of memory once that memory has been
1085 successfully allocated.
1087 total size of vmalloc memory area
1089 amount of vmalloc area which is used
1091 largest contiguous block of vmalloc area which is free
1093 Memory allocated to the percpu allocator used to back percpu
1094 allocations. This stat excludes the cost of metadata.
1099 Provides information about vmalloced/vmaped areas. One line per area,
1100 containing the virtual address range of the area, size in bytes,
1101 caller information of the creator, and optional information depending
1102 on the kind of area :
1104 ========== ===================================================
1105 pages=nr number of pages
1106 phys=addr if a physical address was specified
1107 ioremap I/O mapping (ioremap() and friends)
1108 vmalloc vmalloc() area
1110 user VM_USERMAP area
1111 vpages buffer for pages pointers was vmalloced (huge area)
1112 N<node>=nr (Only on NUMA kernels)
1113 Number of pages allocated on memory node <node>
1114 ========== ===================================================
1118 > cat /proc/vmallocinfo
1119 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
1120 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
1121 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
1122 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
1123 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
1124 phys=7fee8000 ioremap
1125 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
1126 phys=7fee7000 ioremap
1127 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
1128 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
1129 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
1130 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
1131 pages=2 vmalloc N1=2
1132 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
1133 /0x130 [x_tables] pages=4 vmalloc N0=4
1134 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
1135 pages=14 vmalloc N2=14
1136 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
1137 pages=4 vmalloc N1=4
1138 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
1139 pages=2 vmalloc N1=2
1140 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
1141 pages=10 vmalloc N0=10
1147 Provides counts of softirq handlers serviced since boot time, for each cpu.
1151 > cat /proc/softirqs
1154 TIMER: 27166 27120 27097 27034
1159 SCHED: 27035 26983 26971 26746
1161 RCU: 1678 1769 2178 2250
1164 1.3 IDE devices in /proc/ide
1165 ----------------------------
1167 The subdirectory /proc/ide contains information about all IDE devices of which
1168 the kernel is aware. There is one subdirectory for each IDE controller, the
1169 file drivers and a link for each IDE device, pointing to the device directory
1170 in the controller specific subtree.
1172 The file drivers contains general information about the drivers used for the
1175 > cat /proc/ide/drivers
1176 ide-cdrom version 4.53
1177 ide-disk version 1.08
1179 More detailed information can be found in the controller specific
1180 subdirectories. These are named ide0, ide1 and so on. Each of these
1181 directories contains the files shown in table 1-6.
1184 .. table:: Table 1-6: IDE controller info in /proc/ide/ide?
1186 ======= =======================================
1188 ======= =======================================
1189 channel IDE channel (0 or 1)
1190 config Configuration (only for PCI/IDE bridge)
1192 model Type/Chipset of IDE controller
1193 ======= =======================================
1195 Each device connected to a controller has a separate subdirectory in the
1196 controllers directory. The files listed in table 1-7 are contained in these
1200 .. table:: Table 1-7: IDE device information
1202 ================ ==========================================
1204 ================ ==========================================
1206 capacity Capacity of the medium (in 512Byte blocks)
1207 driver driver and version
1208 geometry physical and logical geometry
1209 identify device identify block
1211 model device identifier
1212 settings device setup
1213 smart_thresholds IDE disk management thresholds
1214 smart_values IDE disk management values
1215 ================ ==========================================
1217 The most interesting file is ``settings``. This file contains a nice
1218 overview of the drive parameters::
1220 # cat /proc/ide/ide0/hda/settings
1221 name value min max mode
1222 ---- ----- --- --- ----
1223 bios_cyl 526 0 65535 rw
1224 bios_head 255 0 255 rw
1225 bios_sect 63 0 63 rw
1226 breada_readahead 4 0 127 rw
1228 file_readahead 72 0 2097151 rw
1230 keepsettings 0 0 1 rw
1231 max_kb_per_request 122 1 127 rw
1235 pio_mode write-only 0 255 w
1241 1.4 Networking info in /proc/net
1242 --------------------------------
1244 The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
1245 additional values you get for IP version 6 if you configure the kernel to
1246 support this. Table 1-9 lists the files and their meaning.
1249 .. table:: Table 1-8: IPv6 info in /proc/net
1251 ========== =====================================================
1253 ========== =====================================================
1254 udp6 UDP sockets (IPv6)
1255 tcp6 TCP sockets (IPv6)
1256 raw6 Raw device statistics (IPv6)
1257 igmp6 IP multicast addresses, which this host joined (IPv6)
1258 if_inet6 List of IPv6 interface addresses
1259 ipv6_route Kernel routing table for IPv6
1260 rt6_stats Global IPv6 routing tables statistics
1261 sockstat6 Socket statistics (IPv6)
1262 snmp6 Snmp data (IPv6)
1263 ========== =====================================================
1265 .. table:: Table 1-9: Network info in /proc/net
1267 ============= ================================================================
1269 ============= ================================================================
1270 arp Kernel ARP table
1271 dev network devices with statistics
1272 dev_mcast the Layer2 multicast groups a device is listening too
1273 (interface index, label, number of references, number of bound
1275 dev_stat network device status
1276 ip_fwchains Firewall chain linkage
1277 ip_fwnames Firewall chain names
1278 ip_masq Directory containing the masquerading tables
1279 ip_masquerade Major masquerading table
1280 netstat Network statistics
1281 raw raw device statistics
1282 route Kernel routing table
1283 rpc Directory containing rpc info
1284 rt_cache Routing cache
1286 sockstat Socket statistics
1289 unix UNIX domain sockets
1290 wireless Wireless interface data (Wavelan etc)
1291 igmp IP multicast addresses, which this host joined
1292 psched Global packet scheduler parameters.
1293 netlink List of PF_NETLINK sockets
1294 ip_mr_vifs List of multicast virtual interfaces
1295 ip_mr_cache List of multicast routing cache
1296 ============= ================================================================
1298 You can use this information to see which network devices are available in
1299 your system and how much traffic was routed over those devices::
1302 Inter-|Receive |[...
1303 face |bytes packets errs drop fifo frame compressed multicast|[...
1304 lo: 908188 5596 0 0 0 0 0 0 [...
1305 ppp0:15475140 20721 410 0 0 410 0 0 [...
1306 eth0: 614530 7085 0 0 0 0 0 1 [...
1309 ...] bytes packets errs drop fifo colls carrier compressed
1310 ...] 908188 5596 0 0 0 0 0 0
1311 ...] 1375103 17405 0 0 0 0 0 0
1312 ...] 1703981 5535 0 0 0 3 0 0
1314 In addition, each Channel Bond interface has its own directory. For
1315 example, the bond0 device will have a directory called /proc/net/bond0/.
1316 It will contain information that is specific to that bond, such as the
1317 current slaves of the bond, the link status of the slaves, and how
1318 many times the slaves link has failed.
1323 If you have a SCSI host adapter in your system, you'll find a subdirectory
1324 named after the driver for this adapter in /proc/scsi. You'll also see a list
1325 of all recognized SCSI devices in /proc/scsi::
1327 >cat /proc/scsi/scsi
1329 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1330 Vendor: IBM Model: DGHS09U Rev: 03E0
1331 Type: Direct-Access ANSI SCSI revision: 03
1332 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1333 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1334 Type: CD-ROM ANSI SCSI revision: 02
1337 The directory named after the driver has one file for each adapter found in
1338 the system. These files contain information about the controller, including
1339 the used IRQ and the IO address range. The amount of information shown is
1340 dependent on the adapter you use. The example shows the output for an Adaptec
1341 AHA-2940 SCSI adapter::
1343 > cat /proc/scsi/aic7xxx/0
1345 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1347 TCQ Enabled By Default : Disabled
1348 AIC7XXX_PROC_STATS : Disabled
1349 AIC7XXX_RESET_DELAY : 5
1350 Adapter Configuration:
1351 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1352 Ultra Wide Controller
1353 PCI MMAPed I/O Base: 0xeb001000
1354 Adapter SEEPROM Config: SEEPROM found and used.
1355 Adaptec SCSI BIOS: Enabled
1357 SCBs: Active 0, Max Active 2,
1358 Allocated 15, HW 16, Page 255
1360 BIOS Control Word: 0x18b6
1361 Adapter Control Word: 0x005b
1362 Extended Translation: Enabled
1363 Disconnect Enable Flags: 0xffff
1364 Ultra Enable Flags: 0x0001
1365 Tag Queue Enable Flags: 0x0000
1366 Ordered Queue Tag Flags: 0x0000
1367 Default Tag Queue Depth: 8
1368 Tagged Queue By Device array for aic7xxx host instance 0:
1369 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1370 Actual queue depth per device for aic7xxx host instance 0:
1371 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1374 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1375 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1376 Total transfers 160151 (74577 reads and 85574 writes)
1378 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1379 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1380 Total transfers 0 (0 reads and 0 writes)
1383 1.6 Parallel port info in /proc/parport
1384 ---------------------------------------
1386 The directory /proc/parport contains information about the parallel ports of
1387 your system. It has one subdirectory for each port, named after the port
1390 These directories contain the four files shown in Table 1-10.
1393 .. table:: Table 1-10: Files in /proc/parport
1395 ========= ====================================================================
1397 ========= ====================================================================
1398 autoprobe Any IEEE-1284 device ID information that has been acquired.
1399 devices list of the device drivers using that port. A + will appear by the
1400 name of the device currently using the port (it might not appear
1402 hardware Parallel port's base address, IRQ line and DMA channel.
1403 irq IRQ that parport is using for that port. This is in a separate
1404 file to allow you to alter it by writing a new value in (IRQ
1406 ========= ====================================================================
1408 1.7 TTY info in /proc/tty
1409 -------------------------
1411 Information about the available and actually used tty's can be found in the
1412 directory /proc/tty.You'll find entries for drivers and line disciplines in
1413 this directory, as shown in Table 1-11.
1416 .. table:: Table 1-11: Files in /proc/tty
1418 ============= ==============================================
1420 ============= ==============================================
1421 drivers list of drivers and their usage
1422 ldiscs registered line disciplines
1423 driver/serial usage statistic and status of single tty lines
1424 ============= ==============================================
1426 To see which tty's are currently in use, you can simply look into the file
1429 > cat /proc/tty/drivers
1430 pty_slave /dev/pts 136 0-255 pty:slave
1431 pty_master /dev/ptm 128 0-255 pty:master
1432 pty_slave /dev/ttyp 3 0-255 pty:slave
1433 pty_master /dev/pty 2 0-255 pty:master
1434 serial /dev/cua 5 64-67 serial:callout
1435 serial /dev/ttyS 4 64-67 serial
1436 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1437 /dev/ptmx /dev/ptmx 5 2 system
1438 /dev/console /dev/console 5 1 system:console
1439 /dev/tty /dev/tty 5 0 system:/dev/tty
1440 unknown /dev/tty 4 1-63 console
1443 1.8 Miscellaneous kernel statistics in /proc/stat
1444 -------------------------------------------------
1446 Various pieces of information about kernel activity are available in the
1447 /proc/stat file. All of the numbers reported in this file are aggregates
1448 since the system first booted. For a quick look, simply cat the file::
1451 cpu 2255 34 2290 22625563 6290 127 456 0 0 0
1452 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1453 cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1454 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1460 softirq 183433 0 21755 12 39 1137 231 21459 2263
1462 The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1463 lines. These numbers identify the amount of time the CPU has spent performing
1464 different kinds of work. Time units are in USER_HZ (typically hundredths of a
1465 second). The meanings of the columns are as follows, from left to right:
1467 - user: normal processes executing in user mode
1468 - nice: niced processes executing in user mode
1469 - system: processes executing in kernel mode
1470 - idle: twiddling thumbs
1471 - iowait: In a word, iowait stands for waiting for I/O to complete. But there
1472 are several problems:
1474 1. Cpu will not wait for I/O to complete, iowait is the time that a task is
1475 waiting for I/O to complete. When cpu goes into idle state for
1476 outstanding task io, another task will be scheduled on this CPU.
1477 2. In a multi-core CPU, the task waiting for I/O to complete is not running
1478 on any CPU, so the iowait of each CPU is difficult to calculate.
1479 3. The value of iowait field in /proc/stat will decrease in certain
1482 So, the iowait is not reliable by reading from /proc/stat.
1483 - irq: servicing interrupts
1484 - softirq: servicing softirqs
1485 - steal: involuntary wait
1486 - guest: running a normal guest
1487 - guest_nice: running a niced guest
1489 The "intr" line gives counts of interrupts serviced since boot time, for each
1490 of the possible system interrupts. The first column is the total of all
1491 interrupts serviced including unnumbered architecture specific interrupts;
1492 each subsequent column is the total for that particular numbered interrupt.
1493 Unnumbered interrupts are not shown, only summed into the total.
1495 The "ctxt" line gives the total number of context switches across all CPUs.
1497 The "btime" line gives the time at which the system booted, in seconds since
1500 The "processes" line gives the number of processes and threads created, which
1501 includes (but is not limited to) those created by calls to the fork() and
1502 clone() system calls.
1504 The "procs_running" line gives the total number of threads that are
1505 running or ready to run (i.e., the total number of runnable threads).
1507 The "procs_blocked" line gives the number of processes currently blocked,
1508 waiting for I/O to complete.
1510 The "softirq" line gives counts of softirqs serviced since boot time, for each
1511 of the possible system softirqs. The first column is the total of all
1512 softirqs serviced; each subsequent column is the total for that particular
1516 1.9 Ext4 file system parameters
1517 -------------------------------
1519 Information about mounted ext4 file systems can be found in
1520 /proc/fs/ext4. Each mounted filesystem will have a directory in
1521 /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1522 /proc/fs/ext4/dm-0). The files in each per-device directory are shown
1523 in Table 1-12, below.
1525 .. table:: Table 1-12: Files in /proc/fs/ext4/<devname>
1527 ============== ==========================================================
1529 mb_groups details of multiblock allocator buddy cache of free blocks
1530 ============== ==========================================================
1534 Shows registered system console lines.
1536 To see which character device lines are currently used for the system console
1537 /dev/console, you may simply look into the file /proc/consoles::
1539 > cat /proc/consoles
1545 +--------------------+-------------------------------------------------------+
1546 | device | name of the device |
1547 +====================+=======================================================+
1548 | operations | * R = can do read operations |
1549 | | * W = can do write operations |
1550 | | * U = can do unblank |
1551 +--------------------+-------------------------------------------------------+
1552 | flags | * E = it is enabled |
1553 | | * C = it is preferred console |
1554 | | * B = it is primary boot console |
1555 | | * p = it is used for printk buffer |
1556 | | * b = it is not a TTY but a Braille device |
1557 | | * a = it is safe to use when cpu is offline |
1558 +--------------------+-------------------------------------------------------+
1559 | major:minor | major and minor number of the device separated by a |
1561 +--------------------+-------------------------------------------------------+
1566 The /proc file system serves information about the running system. It not only
1567 allows access to process data but also allows you to request the kernel status
1568 by reading files in the hierarchy.
1570 The directory structure of /proc reflects the types of information and makes
1571 it easy, if not obvious, where to look for specific data.
1573 Chapter 2: Modifying System Parameters
1574 ======================================
1579 * Modifying kernel parameters by writing into files found in /proc/sys
1580 * Exploring the files which modify certain parameters
1581 * Review of the /proc/sys file tree
1583 ------------------------------------------------------------------------------
1585 A very interesting part of /proc is the directory /proc/sys. This is not only
1586 a source of information, it also allows you to change parameters within the
1587 kernel. Be very careful when attempting this. You can optimize your system,
1588 but you can also cause it to crash. Never alter kernel parameters on a
1589 production system. Set up a development machine and test to make sure that
1590 everything works the way you want it to. You may have no alternative but to
1591 reboot the machine once an error has been made.
1593 To change a value, simply echo the new value into the file. An example is
1594 given below in the section on the file system data. You need to be root to do
1595 this. You can create your own boot script to perform this every time your
1598 The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1599 general things in the operation of the Linux kernel. Since some of the files
1600 can inadvertently disrupt your system, it is advisable to read both
1601 documentation and source before actually making adjustments. In any case, be
1602 very careful when writing to any of these files. The entries in /proc may
1603 change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1604 review the kernel documentation in the directory /usr/src/linux/Documentation.
1605 This chapter is heavily based on the documentation included in the pre 2.2
1606 kernels, and became part of it in version 2.2.1 of the Linux kernel.
1608 Please see: Documentation/admin-guide/sysctl/ directory for descriptions of these
1614 Certain aspects of kernel behavior can be modified at runtime, without the
1615 need to recompile the kernel, or even to reboot the system. The files in the
1616 /proc/sys tree can not only be read, but also modified. You can use the echo
1617 command to write value into these files, thereby changing the default settings
1621 Chapter 3: Per-process Parameters
1622 =================================
1624 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1625 --------------------------------------------------------------------------------
1627 These file can be used to adjust the badness heuristic used to select which
1628 process gets killed in out of memory conditions.
1630 The badness heuristic assigns a value to each candidate task ranging from 0
1631 (never kill) to 1000 (always kill) to determine which process is targeted. The
1632 units are roughly a proportion along that range of allowed memory the process
1633 may allocate from based on an estimation of its current memory and swap use.
1634 For example, if a task is using all allowed memory, its badness score will be
1635 1000. If it is using half of its allowed memory, its score will be 500.
1637 There is an additional factor included in the badness score: the current memory
1638 and swap usage is discounted by 3% for root processes.
1640 The amount of "allowed" memory depends on the context in which the oom killer
1641 was called. If it is due to the memory assigned to the allocating task's cpuset
1642 being exhausted, the allowed memory represents the set of mems assigned to that
1643 cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1644 memory represents the set of mempolicy nodes. If it is due to a memory
1645 limit (or swap limit) being reached, the allowed memory is that configured
1646 limit. Finally, if it is due to the entire system being out of memory, the
1647 allowed memory represents all allocatable resources.
1649 The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1650 is used to determine which task to kill. Acceptable values range from -1000
1651 (OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1652 polarize the preference for oom killing either by always preferring a certain
1653 task or completely disabling it. The lowest possible value, -1000, is
1654 equivalent to disabling oom killing entirely for that task since it will always
1655 report a badness score of 0.
1657 Consequently, it is very simple for userspace to define the amount of memory to
1658 consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1659 example, is roughly equivalent to allowing the remainder of tasks sharing the
1660 same system, cpuset, mempolicy, or memory controller resources to use at least
1661 50% more memory. A value of -500, on the other hand, would be roughly
1662 equivalent to discounting 50% of the task's allowed memory from being considered
1663 as scoring against the task.
1665 For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1666 be used to tune the badness score. Its acceptable values range from -16
1667 (OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1668 (OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1669 scaled linearly with /proc/<pid>/oom_score_adj.
1671 The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1672 value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1673 requires CAP_SYS_RESOURCE.
1675 Caveat: when a parent task is selected, the oom killer will sacrifice any first
1676 generation children with separate address spaces instead, if possible. This
1677 avoids servers and important system daemons from being killed and loses the
1678 minimal amount of work.
1681 3.2 /proc/<pid>/oom_score - Display current oom-killer score
1682 -------------------------------------------------------------
1684 This file can be used to check the current score used by the oom-killer is for
1685 any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1686 process should be killed in an out-of-memory situation.
1689 3.3 /proc/<pid>/io - Display the IO accounting fields
1690 -------------------------------------------------------
1692 This file contains IO statistics for each running process
1699 test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1702 test:/tmp # cat /proc/3828/io
1708 write_bytes: 323932160
1709 cancelled_write_bytes: 0
1718 I/O counter: chars read
1719 The number of bytes which this task has caused to be read from storage. This
1720 is simply the sum of bytes which this process passed to read() and pread().
1721 It includes things like tty IO and it is unaffected by whether or not actual
1722 physical disk IO was required (the read might have been satisfied from
1729 I/O counter: chars written
1730 The number of bytes which this task has caused, or shall cause to be written
1731 to disk. Similar caveats apply here as with rchar.
1737 I/O counter: read syscalls
1738 Attempt to count the number of read I/O operations, i.e. syscalls like read()
1745 I/O counter: write syscalls
1746 Attempt to count the number of write I/O operations, i.e. syscalls like
1747 write() and pwrite().
1753 I/O counter: bytes read
1754 Attempt to count the number of bytes which this process really did cause to
1755 be fetched from the storage layer. Done at the submit_bio() level, so it is
1756 accurate for block-backed filesystems. <please add status regarding NFS and
1757 CIFS at a later time>
1763 I/O counter: bytes written
1764 Attempt to count the number of bytes which this process caused to be sent to
1765 the storage layer. This is done at page-dirtying time.
1768 cancelled_write_bytes
1769 ^^^^^^^^^^^^^^^^^^^^^
1771 The big inaccuracy here is truncate. If a process writes 1MB to a file and
1772 then deletes the file, it will in fact perform no writeout. But it will have
1773 been accounted as having caused 1MB of write.
1774 In other words: The number of bytes which this process caused to not happen,
1775 by truncating pagecache. A task can cause "negative" IO too. If this task
1776 truncates some dirty pagecache, some IO which another task has been accounted
1777 for (in its write_bytes) will not be happening. We _could_ just subtract that
1778 from the truncating task's write_bytes, but there is information loss in doing
1784 At its current implementation state, this is a bit racy on 32-bit machines:
1785 if process A reads process B's /proc/pid/io while process B is updating one
1786 of those 64-bit counters, process A could see an intermediate result.
1789 More information about this can be found within the taskstats documentation in
1790 Documentation/accounting.
1792 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1793 ---------------------------------------------------------------
1794 When a process is dumped, all anonymous memory is written to a core file as
1795 long as the size of the core file isn't limited. But sometimes we don't want
1796 to dump some memory segments, for example, huge shared memory or DAX.
1797 Conversely, sometimes we want to save file-backed memory segments into a core
1798 file, not only the individual files.
1800 /proc/<pid>/coredump_filter allows you to customize which memory segments
1801 will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1802 of memory types. If a bit of the bitmask is set, memory segments of the
1803 corresponding memory type are dumped, otherwise they are not dumped.
1805 The following 9 memory types are supported:
1807 - (bit 0) anonymous private memory
1808 - (bit 1) anonymous shared memory
1809 - (bit 2) file-backed private memory
1810 - (bit 3) file-backed shared memory
1811 - (bit 4) ELF header pages in file-backed private memory areas (it is
1812 effective only if the bit 2 is cleared)
1813 - (bit 5) hugetlb private memory
1814 - (bit 6) hugetlb shared memory
1815 - (bit 7) DAX private memory
1816 - (bit 8) DAX shared memory
1818 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1819 are always dumped regardless of the bitmask status.
1821 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
1822 only affected by bit 5-6, and DAX is only affected by bits 7-8.
1824 The default value of coredump_filter is 0x33; this means all anonymous memory
1825 segments, ELF header pages and hugetlb private memory are dumped.
1827 If you don't want to dump all shared memory segments attached to pid 1234,
1828 write 0x31 to the process's proc file::
1830 $ echo 0x31 > /proc/1234/coredump_filter
1832 When a new process is created, the process inherits the bitmask status from its
1833 parent. It is useful to set up coredump_filter before the program runs.
1836 $ echo 0x7 > /proc/self/coredump_filter
1839 3.5 /proc/<pid>/mountinfo - Information about mounts
1840 --------------------------------------------------------
1842 This file contains lines of the form::
1844 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1845 (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1847 (1) mount ID: unique identifier of the mount (may be reused after umount)
1848 (2) parent ID: ID of parent (or of self for the top of the mount tree)
1849 (3) major:minor: value of st_dev for files on filesystem
1850 (4) root: root of the mount within the filesystem
1851 (5) mount point: mount point relative to the process's root
1852 (6) mount options: per mount options
1853 (7) optional fields: zero or more fields of the form "tag[:value]"
1854 (8) separator: marks the end of the optional fields
1855 (9) filesystem type: name of filesystem of the form "type[.subtype]"
1856 (10) mount source: filesystem specific information or "none"
1857 (11) super options: per super block options
1859 Parsers should ignore all unrecognised optional fields. Currently the
1860 possible optional fields are:
1862 ================ ==============================================================
1863 shared:X mount is shared in peer group X
1864 master:X mount is slave to peer group X
1865 propagate_from:X mount is slave and receives propagation from peer group X [#]_
1866 unbindable mount is unbindable
1867 ================ ==============================================================
1869 .. [#] X is the closest dominant peer group under the process's root. If
1870 X is the immediate master of the mount, or if there's no dominant peer
1871 group under the same root, then only the "master:X" field is present
1872 and not the "propagate_from:X" field.
1874 For more information on mount propagation see:
1876 Documentation/filesystems/sharedsubtree.rst
1879 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1880 --------------------------------------------------------
1881 These files provide a method to access a tasks comm value. It also allows for
1882 a task to set its own or one of its thread siblings comm value. The comm value
1883 is limited in size compared to the cmdline value, so writing anything longer
1884 then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1888 3.7 /proc/<pid>/task/<tid>/children - Information about task children
1889 -------------------------------------------------------------------------
1890 This file provides a fast way to retrieve first level children pids
1891 of a task pointed by <pid>/<tid> pair. The format is a space separated
1894 Note the "first level" here -- if a child has own children they will
1895 not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1896 to obtain the descendants.
1898 Since this interface is intended to be fast and cheap it doesn't
1899 guarantee to provide precise results and some children might be
1900 skipped, especially if they've exited right after we printed their
1901 pids, so one need to either stop or freeze processes being inspected
1902 if precise results are needed.
1905 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
1906 ---------------------------------------------------------------
1907 This file provides information associated with an opened file. The regular
1908 files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1909 represents the current offset of the opened file in decimal form [see lseek(2)
1910 for details], 'flags' denotes the octal O_xxx mask the file has been
1911 created with [see open(2) for details] and 'mnt_id' represents mount ID of
1912 the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1915 A typical output is::
1921 All locks associated with a file descriptor are shown in its fdinfo too::
1923 lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF
1925 The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1926 pair provide additional information particular to the objects they represent.
1938 where 'eventfd-count' is hex value of a counter.
1948 sigmask: 0000000000000200
1950 where 'sigmask' is hex value of the signal mask associated
1961 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7
1963 where 'tfd' is a target file descriptor number in decimal form,
1964 'events' is events mask being watched and the 'data' is data
1965 associated with a target [see epoll(7) for more details].
1967 The 'pos' is current offset of the target file in decimal form
1968 [see lseek(2)], 'ino' and 'sdev' are inode and device numbers
1969 where target file resides, all in hex format.
1973 For inotify files the format is the following::
1977 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1979 where 'wd' is a watch descriptor in decimal form, ie a target file
1980 descriptor number, 'ino' and 'sdev' are inode and device where the
1981 target file resides and the 'mask' is the mask of events, all in hex
1982 form [see inotify(7) for more details].
1984 If the kernel was built with exportfs support, the path to the target
1985 file is encoded as a file handle. The file handle is provided by three
1986 fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1989 If the kernel is built without exportfs support the file handle won't be
1992 If there is no inotify mark attached yet the 'inotify' line will be omitted.
1994 For fanotify files the format is::
1999 fanotify flags:10 event-flags:0
2000 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
2001 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
2003 where fanotify 'flags' and 'event-flags' are values used in fanotify_init
2004 call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
2005 flags associated with mark which are tracked separately from events
2006 mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
2007 mask and 'ignored_mask' is the mask of events which are to be ignored.
2008 All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
2009 does provide information about flags and mask used in fanotify_mark
2010 call [see fsnotify manpage for details].
2012 While the first three lines are mandatory and always printed, the rest is
2013 optional and may be omitted if no marks created yet.
2026 it_value: (0, 49406829)
2029 where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
2030 that have occurred [see timerfd_create(2) for details]. 'settime flags' are
2031 flags in octal form been used to setup the timer [see timerfd_settime(2) for
2032 details]. 'it_value' is remaining time until the timer exiration.
2033 'it_interval' is the interval for the timer. Note the timer might be set up
2034 with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
2035 still exhibits timer's remaining time.
2037 3.9 /proc/<pid>/map_files - Information about memory mapped files
2038 ---------------------------------------------------------------------
2039 This directory contains symbolic links which represent memory mapped files
2040 the process is maintaining. Example output::
2042 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
2043 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
2044 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
2046 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
2047 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
2049 The name of a link represents the virtual memory bounds of a mapping, i.e.
2050 vm_area_struct::vm_start-vm_area_struct::vm_end.
2052 The main purpose of the map_files is to retrieve a set of memory mapped
2053 files in a fast way instead of parsing /proc/<pid>/maps or
2054 /proc/<pid>/smaps, both of which contain many more records. At the same
2055 time one can open(2) mappings from the listings of two processes and
2056 comparing their inode numbers to figure out which anonymous memory areas
2057 are actually shared.
2059 3.10 /proc/<pid>/timerslack_ns - Task timerslack value
2060 ---------------------------------------------------------
2061 This file provides the value of the task's timerslack value in nanoseconds.
2062 This value specifies a amount of time that normal timers may be deferred
2063 in order to coalesce timers and avoid unnecessary wakeups.
2065 This allows a task's interactivity vs power consumption trade off to be
2068 Writing 0 to the file will set the tasks timerslack to the default value.
2070 Valid values are from 0 - ULLONG_MAX
2072 An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
2073 permissions on the task specified to change its timerslack_ns value.
2075 3.11 /proc/<pid>/patch_state - Livepatch patch operation state
2076 -----------------------------------------------------------------
2077 When CONFIG_LIVEPATCH is enabled, this file displays the value of the
2078 patch state for the task.
2080 A value of '-1' indicates that no patch is in transition.
2082 A value of '0' indicates that a patch is in transition and the task is
2083 unpatched. If the patch is being enabled, then the task hasn't been
2084 patched yet. If the patch is being disabled, then the task has already
2087 A value of '1' indicates that a patch is in transition and the task is
2088 patched. If the patch is being enabled, then the task has already been
2089 patched. If the patch is being disabled, then the task hasn't been
2092 3.12 /proc/<pid>/arch_status - task architecture specific status
2093 -------------------------------------------------------------------
2094 When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the
2095 architecture specific status of the task.
2102 $ cat /proc/6753/arch_status
2103 AVX512_elapsed_ms: 8
2108 x86 specific entries:
2109 ~~~~~~~~~~~~~~~~~~~~~
2114 If AVX512 is supported on the machine, this entry shows the milliseconds
2115 elapsed since the last time AVX512 usage was recorded. The recording
2116 happens on a best effort basis when a task is scheduled out. This means
2117 that the value depends on two factors:
2119 1) The time which the task spent on the CPU without being scheduled
2120 out. With CPU isolation and a single runnable task this can take
2123 2) The time since the task was scheduled out last. Depending on the
2124 reason for being scheduled out (time slice exhausted, syscall ...)
2125 this can be arbitrary long time.
2127 As a consequence the value cannot be considered precise and authoritative
2128 information. The application which uses this information has to be aware
2129 of the overall scenario on the system in order to determine whether a
2130 task is a real AVX512 user or not. Precise information can be obtained
2131 with performance counters.
2133 A special value of '-1' indicates that no AVX512 usage was recorded, thus
2134 the task is unlikely an AVX512 user, but depends on the workload and the
2135 scheduling scenario, it also could be a false negative mentioned above.
2141 ---------------------
2143 The following mount options are supported:
2145 ========= ========================================================
2146 hidepid= Set /proc/<pid>/ access mode.
2147 gid= Set the group authorized to learn processes information.
2148 subset= Show only the specified subset of procfs.
2149 ========= ========================================================
2151 hidepid=off or hidepid=0 means classic mode - everybody may access all
2152 /proc/<pid>/ directories (default).
2154 hidepid=noaccess or hidepid=1 means users may not access any /proc/<pid>/
2155 directories but their own. Sensitive files like cmdline, sched*, status are now
2156 protected against other users. This makes it impossible to learn whether any
2157 user runs specific program (given the program doesn't reveal itself by its
2158 behaviour). As an additional bonus, as /proc/<pid>/cmdline is unaccessible for
2159 other users, poorly written programs passing sensitive information via program
2160 arguments are now protected against local eavesdroppers.
2162 hidepid=invisible or hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be
2163 fully invisible to other users. It doesn't mean that it hides a fact whether a
2164 process with a specific pid value exists (it can be learned by other means, e.g.
2165 by "kill -0 $PID"), but it hides process' uid and gid, which may be learned by
2166 stat()'ing /proc/<pid>/ otherwise. It greatly complicates an intruder's task of
2167 gathering information about running processes, whether some daemon runs with
2168 elevated privileges, whether other user runs some sensitive program, whether
2169 other users run any program at all, etc.
2171 hidepid=ptraceable or hidepid=4 means that procfs should only contain
2172 /proc/<pid>/ directories that the caller can ptrace.
2174 gid= defines a group authorized to learn processes information otherwise
2175 prohibited by hidepid=. If you use some daemon like identd which needs to learn
2176 information about processes information, just add identd to this group.
2178 subset=pid hides all top level files and directories in the procfs that
2179 are not related to tasks.
2181 5 Filesystem behavior
2182 ----------------------------
2184 Originally, before the advent of pid namepsace, procfs was a global file
2185 system. It means that there was only one procfs instance in the system.
2187 When pid namespace was added, a separate procfs instance was mounted in
2188 each pid namespace. So, procfs mount options are global among all
2189 mountpoints within the same namespace.
2193 # grep ^proc /proc/mounts
2194 proc /proc proc rw,relatime,hidepid=2 0 0
2196 # strace -e mount mount -o hidepid=1 -t proc proc /tmp/proc
2197 mount("proc", "/tmp/proc", "proc", 0, "hidepid=1") = 0
2198 +++ exited with 0 +++
2200 # grep ^proc /proc/mounts
2201 proc /proc proc rw,relatime,hidepid=2 0 0
2202 proc /tmp/proc proc rw,relatime,hidepid=2 0 0
2204 and only after remounting procfs mount options will change at all
2207 # mount -o remount,hidepid=1 -t proc proc /tmp/proc
2209 # grep ^proc /proc/mounts
2210 proc /proc proc rw,relatime,hidepid=1 0 0
2211 proc /tmp/proc proc rw,relatime,hidepid=1 0 0
2213 This behavior is different from the behavior of other filesystems.
2215 The new procfs behavior is more like other filesystems. Each procfs mount
2216 creates a new procfs instance. Mount options affect own procfs instance.
2217 It means that it became possible to have several procfs instances
2218 displaying tasks with different filtering options in one pid namespace.
2220 # mount -o hidepid=invisible -t proc proc /proc
2221 # mount -o hidepid=noaccess -t proc proc /tmp/proc
2222 # grep ^proc /proc/mounts
2223 proc /proc proc rw,relatime,hidepid=invisible 0 0
2224 proc /tmp/proc proc rw,relatime,hidepid=noaccess 0 0
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