diff options
Diffstat (limited to 'Documentation/filesystems/proc.rst')
| -rw-r--r-- | Documentation/filesystems/proc.rst | 2169 |
1 files changed, 2169 insertions, 0 deletions
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst new file mode 100644 index 000000000000..38b606991065 --- /dev/null +++ b/Documentation/filesystems/proc.rst @@ -0,0 +1,2169 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==================== +The /proc Filesystem +==================== + +===================== ======================================= ================ +/proc/sys Terrehon Bowden <terrehon@pacbell.net>, October 7 1999 + Bodo Bauer <bb@ricochet.net> +2.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000 +move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009 +fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009 +===================== ======================================= ================ + + + +.. Table of Contents + + 0 Preface + 0.1 Introduction/Credits + 0.2 Legal Stuff + + 1 Collecting System Information + 1.1 Process-Specific Subdirectories + 1.2 Kernel data + 1.3 IDE devices in /proc/ide + 1.4 Networking info in /proc/net + 1.5 SCSI info + 1.6 Parallel port info in /proc/parport + 1.7 TTY info in /proc/tty + 1.8 Miscellaneous kernel statistics in /proc/stat + 1.9 Ext4 file system parameters + + 2 Modifying System Parameters + + 3 Per-Process Parameters + 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer + score + 3.2 /proc/<pid>/oom_score - Display current oom-killer score + 3.3 /proc/<pid>/io - Display the IO accounting fields + 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings + 3.5 /proc/<pid>/mountinfo - Information about mounts + 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm + 3.7 /proc/<pid>/task/<tid>/children - Information about task children + 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file + 3.9 /proc/<pid>/map_files - Information about memory mapped files + 3.10 /proc/<pid>/timerslack_ns - Task timerslack value + 3.11 /proc/<pid>/patch_state - Livepatch patch operation state + 3.12 /proc/<pid>/arch_status - Task architecture specific information + + 4 Configuring procfs + 4.1 Mount options + +Preface +======= + +0.1 Introduction/Credits +------------------------ + +This documentation is part of a soon (or so we hope) to be released book on +the SuSE Linux distribution. As there is no complete documentation for the +/proc file system and we've used many freely available sources to write these +chapters, it seems only fair to give the work back to the Linux community. +This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm +afraid it's still far from complete, but we hope it will be useful. As far as +we know, it is the first 'all-in-one' document about the /proc file system. It +is focused on the Intel x86 hardware, so if you are looking for PPC, ARM, +SPARC, AXP, etc., features, you probably won't find what you are looking for. +It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But +additions and patches are welcome and will be added to this document if you +mail them to Bodo. + +We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of +other people for help compiling this documentation. We'd also like to extend a +special thank you to Andi Kleen for documentation, which we relied on heavily +to create this document, as well as the additional information he provided. +Thanks to everybody else who contributed source or docs to the Linux kernel +and helped create a great piece of software... :) + +If you have any comments, corrections or additions, please don't hesitate to +contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this +document. + +The latest version of this document is available online at +http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html + +If the above direction does not works for you, you could try the kernel +mailing list at linux-kernel@vger.kernel.org and/or try to reach me at +comandante@zaralinux.com. + +0.2 Legal Stuff +--------------- + +We don't guarantee the correctness of this document, and if you come to us +complaining about how you screwed up your system because of incorrect +documentation, we won't feel responsible... + +Chapter 1: Collecting System Information +======================================== + +In This Chapter +--------------- +* Investigating the properties of the pseudo file system /proc and its + ability to provide information on the running Linux system +* Examining /proc's structure +* Uncovering various information about the kernel and the processes running + on the system + +------------------------------------------------------------------------------ + +The proc file system acts as an interface to internal data structures in the +kernel. It can be used to obtain information about the system and to change +certain kernel parameters at runtime (sysctl). + +First, we'll take a look at the read-only parts of /proc. In Chapter 2, we +show you how you can use /proc/sys to change settings. + +1.1 Process-Specific Subdirectories +----------------------------------- + +The directory /proc contains (among other things) one subdirectory for each +process running on the system, which is named after the process ID (PID). + +The link self points to the process reading the file system. Each process +subdirectory has the entries listed in Table 1-1. + +Note that an open a file descriptor to /proc/<pid> or to any of its +contained files or subdirectories does not prevent <pid> being reused +for some other process in the event that <pid> exits. Operations on +open /proc/<pid> file descriptors corresponding to dead processes +never act on any new process that the kernel may, through chance, have +also assigned the process ID <pid>. Instead, operations on these FDs +usually fail with ESRCH. + +.. table:: Table 1-1: Process specific entries in /proc + + ============= =============================================================== + File Content + ============= =============================================================== + clear_refs Clears page referenced bits shown in smaps output + cmdline Command line arguments + cpu Current and last cpu in which it was executed (2.4)(smp) + cwd Link to the current working directory + environ Values of environment variables + exe Link to the executable of this process + fd Directory, which contains all file descriptors + maps Memory maps to executables and library files (2.4) + mem Memory held by this process + root Link to the root directory of this process + stat Process status + statm Process memory status information + status Process status in human readable form + wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function + symbol the task is blocked in - or "0" if not blocked. + pagemap Page table + stack Report full stack trace, enable via CONFIG_STACKTRACE + smaps An extension based on maps, showing the memory consumption of + each mapping and flags associated with it + smaps_rollup Accumulated smaps stats for all mappings of the process. This + can be derived from smaps, but is faster and more convenient + numa_maps An extension based on maps, showing the memory locality and + binding policy as well as mem usage (in pages) of each mapping. + ============= =============================================================== + +For example, to get the status information of a process, all you have to do is +read the file /proc/PID/status:: + + >cat /proc/self/status + Name: cat + State: R (running) + Tgid: 5452 + Pid: 5452 + PPid: 743 + TracerPid: 0 (2.4) + Uid: 501 501 501 501 + Gid: 100 100 100 100 + FDSize: 256 + Groups: 100 14 16 + VmPeak: 5004 kB + VmSize: 5004 kB + VmLck: 0 kB + VmHWM: 476 kB + VmRSS: 476 kB + RssAnon: 352 kB + RssFile: 120 kB + RssShmem: 4 kB + VmData: 156 kB + VmStk: 88 kB + VmExe: 68 kB + VmLib: 1412 kB + VmPTE: 20 kb + VmSwap: 0 kB + HugetlbPages: 0 kB + CoreDumping: 0 + THP_enabled: 1 + Threads: 1 + SigQ: 0/28578 + SigPnd: 0000000000000000 + ShdPnd: 0000000000000000 + SigBlk: 0000000000000000 + SigIgn: 0000000000000000 + SigCgt: 0000000000000000 + CapInh: 00000000fffffeff + CapPrm: 0000000000000000 + CapEff: 0000000000000000 + CapBnd: ffffffffffffffff + CapAmb: 0000000000000000 + NoNewPrivs: 0 + Seccomp: 0 + Speculation_Store_Bypass: thread vulnerable + voluntary_ctxt_switches: 0 + nonvoluntary_ctxt_switches: 1 + +This shows you nearly the same information you would get if you viewed it with +the ps command. In fact, ps uses the proc file system to obtain its +information. But you get a more detailed view of the process by reading the +file /proc/PID/status. It fields are described in table 1-2. + +The statm file contains more detailed information about the process +memory usage. Its seven fields are explained in Table 1-3. The stat file +contains details information about the process itself. Its fields are +explained in Table 1-4. + +(for SMP CONFIG users) + +For making accounting scalable, RSS related information are handled in an +asynchronous manner and the value may not be very precise. To see a precise +snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table. +It's slow but very precise. + +.. table:: Table 1-2: Contents of the status files (as of 4.19) + + ========================== =================================================== + Field Content + ========================== =================================================== + Name filename of the executable + Umask file mode creation mask + State state (R is running, S is sleeping, D is sleeping + in an uninterruptible wait, Z is zombie, + T is traced or stopped) + Tgid thread group ID + Ngid NUMA group ID (0 if none) + Pid process id + PPid process id of the parent process + TracerPid PID of process tracing this process (0 if not) + Uid Real, effective, saved set, and file system UIDs + Gid Real, effective, saved set, and file system GIDs + FDSize number of file descriptor slots currently allocated + Groups supplementary group list + NStgid descendant namespace thread group ID hierarchy + NSpid descendant namespace process ID hierarchy + NSpgid descendant namespace process group ID hierarchy + NSsid descendant namespace session ID hierarchy + VmPeak peak virtual memory size + VmSize total program size + VmLck locked memory size + VmPin pinned memory size + VmHWM peak resident set size ("high water mark") + VmRSS size of memory portions. It contains the three + following parts + (VmRSS = RssAnon + RssFile + RssShmem) + RssAnon size of resident anonymous memory + RssFile size of resident file mappings + RssShmem size of resident shmem memory (includes SysV shm, + mapping of tmpfs and shared anonymous mappings) + VmData size of private data segments + VmStk size of stack segments + VmExe size of text segment + VmLib size of shared library code + VmPTE size of page table entries + VmSwap amount of swap used by anonymous private data + (shmem swap usage is not included) + HugetlbPages size of hugetlb memory portions + CoreDumping process's memory is currently being dumped + (killing the process may lead to a corrupted core) + THP_enabled process is allowed to use THP (returns 0 when + PR_SET_THP_DISABLE is set on the process + Threads number of threads + SigQ number of signals queued/max. number for queue + SigPnd bitmap of pending signals for the thread + ShdPnd bitmap of shared pending signals for the process + SigBlk bitmap of blocked signals + SigIgn bitmap of ignored signals + SigCgt bitmap of caught signals + CapInh bitmap of inheritable capabilities + CapPrm bitmap of permitted capabilities + CapEff bitmap of effective capabilities + CapBnd bitmap of capabilities bounding set + CapAmb bitmap of ambient capabilities + NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...) + Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...) + Speculation_Store_Bypass speculative store bypass mitigation status + Cpus_allowed mask of CPUs on which this process may run + Cpus_allowed_list Same as previous, but in "list format" + Mems_allowed mask of memory nodes allowed to this process + Mems_allowed_list Same as previous, but in "list format" + voluntary_ctxt_switches number of voluntary context switches + nonvoluntary_ctxt_switches number of non voluntary context switches + ========================== =================================================== + + +.. table:: Table 1-3: Contents of the statm files (as of 2.6.8-rc3) + + ======== =============================== ============================== + Field Content + ======== =============================== ============================== + size total program size (pages) (same as VmSize in status) + resident size of memory portions (pages) (same as VmRSS in status) + shared number of pages that are shared (i.e. backed by a file, same + as RssFile+RssShmem in status) + trs number of pages that are 'code' (not including libs; broken, + includes data segment) + lrs number of pages of library (always 0 on 2.6) + drs number of pages of data/stack (including libs; broken, + includes library text) + dt number of dirty pages (always 0 on 2.6) + ======== =============================== ============================== + + +.. table:: Table 1-4: Contents of the stat files (as of 2.6.30-rc7) + + ============= =============================================================== + Field Content + ============= =============================================================== + pid process id + tcomm filename of the executable + state state (R is running, S is sleeping, D is sleeping in an + uninterruptible wait, Z is zombie, T is traced or stopped) + ppid process id of the parent process + pgrp pgrp of the process + sid session id + tty_nr tty the process uses + tty_pgrp pgrp of the tty + flags task flags + min_flt number of minor faults + cmin_flt number of minor faults with child's + maj_flt number of major faults + cmaj_flt number of major faults with child's + utime user mode jiffies + stime kernel mode jiffies + cutime user mode jiffies with child's + cstime kernel mode jiffies with child's + priority priority level + nice nice level + num_threads number of threads + it_real_value (obsolete, always 0) + start_time time the process started after system boot + vsize virtual memory size + rss resident set memory size + rsslim current limit in bytes on the rss + start_code address above which program text can run + end_code address below which program text can run + start_stack address of the start of the main process stack + esp current value of ESP + eip current value of EIP + pending bitmap of pending signals + blocked bitmap of blocked signals + sigign bitmap of ignored signals + sigcatch bitmap of caught signals + 0 (place holder, used to be the wchan address, + use /proc/PID/wchan instead) + 0 (place holder) + 0 (place holder) + exit_signal signal to send to parent thread on exit + task_cpu which CPU the task is scheduled on + rt_priority realtime priority + policy scheduling policy (man sched_setscheduler) + blkio_ticks time spent waiting for block IO + gtime guest time of the task in jiffies + cgtime guest time of the task children in jiffies + start_data address above which program data+bss is placed + end_data address below which program data+bss is placed + start_brk address above which program heap can be expanded with brk() + arg_start address above which program command line is placed + arg_end address below which program command line is placed + env_start address above which program environment is placed + env_end address below which program environment is placed + exit_code the thread's exit_code in the form reported by the waitpid + system call + ============= =============================================================== + +The /proc/PID/maps file contains the currently mapped memory regions and +their access permissions. + +The format is:: + + address perms offset dev inode pathname + + 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test + 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test + 0804a000-0806b000 rw-p 00000000 00:00 0 [heap] + a7cb1000-a7cb2000 ---p 00000000 00:00 0 + a7cb2000-a7eb2000 rw-p 00000000 00:00 0 + a7eb2000-a7eb3000 ---p 00000000 00:00 0 + a7eb3000-a7ed5000 rw-p 00000000 00:00 0 + a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 + a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 + a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 + a800b000-a800e000 rw-p 00000000 00:00 0 + a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 + a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 + a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 + a8024000-a8027000 rw-p 00000000 00:00 0 + a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 + a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 + a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 + aff35000-aff4a000 rw-p 00000000 00:00 0 [stack] + ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] + +where "address" is the address space in the process that it occupies, "perms" +is a set of permissions:: + + r = read + w = write + x = execute + s = shared + p = private (copy on write) + +"offset" is the offset into the mapping, "dev" is the device (major:minor), and +"inode" is the inode on that device. 0 indicates that no inode is associated +with the memory region, as the case would be with BSS (uninitialized data). +The "pathname" shows the name associated file for this mapping. If the mapping +is not associated with a file: + + ======= ==================================== + [heap] the heap of the program + [stack] the stack of the main process + [vdso] the "virtual dynamic shared object", + the kernel system call handler + ======= ==================================== + + or if empty, the mapping is anonymous. + +The /proc/PID/smaps is an extension based on maps, showing the memory +consumption for each of the process's mappings. For each mapping (aka Virtual +Memory Area, or VMA) there is a series of lines such as the following:: + + 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash + + Size: 1084 kB + KernelPageSize: 4 kB + MMUPageSize: 4 kB + Rss: 892 kB + Pss: 374 kB + Shared_Clean: 892 kB + Shared_Dirty: 0 kB + Private_Clean: 0 kB + Private_Dirty: 0 kB + Referenced: 892 kB + Anonymous: 0 kB + LazyFree: 0 kB + AnonHugePages: 0 kB + ShmemPmdMapped: 0 kB + Shared_Hugetlb: 0 kB + Private_Hugetlb: 0 kB + Swap: 0 kB + SwapPss: 0 kB + KernelPageSize: 4 kB + MMUPageSize: 4 kB + Locked: 0 kB + THPeligible: 0 + VmFlags: rd ex mr mw me dw + +The first of these lines shows the same information as is displayed for the +mapping in /proc/PID/maps. Following lines show the size of the mapping +(size); the size of each page allocated when backing a VMA (KernelPageSize), +which is usually the same as the size in the page table entries; the page size +used by the MMU when backing a VMA (in most cases, the same as KernelPageSize); +the amount of the mapping that is currently resident in RAM (RSS); the +process' proportional share of this mapping (PSS); and the number of clean and +dirty shared and private pages in the mapping. + +The "proportional set size" (PSS) of a process is the count of pages it has +in memory, where each page is divided by the number of processes sharing it. +So if a process has 1000 pages all to itself, and 1000 shared with one other +process, its PSS will be 1500. + +Note that even a page which is part of a MAP_SHARED mapping, but has only +a single pte mapped, i.e. is currently used by only one process, is accounted +as private and not as shared. + +"Referenced" indicates the amount of memory currently marked as referenced or +accessed. + +"Anonymous" shows the amount of memory that does not belong to any file. Even +a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE +and a page is modified, the file page is replaced by a private anonymous copy. + +"LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE). +The memory isn't freed immediately with madvise(). It's freed in memory +pressure if the memory is clean. Please note that the printed value might +be lower than the real value due to optimizations used in the current +implementation. If this is not desirable please file a bug report. + +"AnonHugePages" shows the ammount of memory backed by transparent hugepage. + +"ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by +huge pages. + +"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by +hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical +reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field. + +"Swap" shows how much would-be-anonymous memory is also used, but out on swap. + +For shmem mappings, "Swap" includes also the size of the mapped (and not +replaced by copy-on-write) part of the underlying shmem object out on swap. +"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this +does not take into account swapped out page of underlying shmem objects. +"Locked" indicates whether the mapping is locked in memory or not. +"THPeligible" indicates whether the mapping is eligible for allocating THP +pages - 1 if true, 0 otherwise. It just shows the current status. + +"VmFlags" field deserves a separate description. This member represents the +kernel flags associated with the particular virtual memory area in two letter +encoded manner. The codes are the following: + + == ======================================= + rd readable + wr writeable + ex executable + sh shared + mr may read + mw may write + me may execute + ms may share + gd stack segment growns down + pf pure PFN range + dw disabled write to the mapped file + lo pages are locked in memory + io memory mapped I/O area + sr sequential read advise provided + rr random read advise provided + dc do not copy area on fork + de do not expand area on remapping + ac area is accountable + nr swap space is not reserved for the area + ht area uses huge tlb pages + ar architecture specific flag + dd do not include area into core dump + sd soft dirty flag + mm mixed map area + hg huge page advise flag + nh no huge page advise flag + mg mergable advise flag + == ======================================= + +Note that there is no guarantee that every flag and associated mnemonic will +be present in all further kernel releases. Things get changed, the flags may +be vanished or the reverse -- new added. Interpretation of their meaning +might change in future as well. So each consumer of these flags has to +follow each specific kernel version for the exact semantic. + +This file is only present if the CONFIG_MMU kernel configuration option is +enabled. + +Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent +output can be achieved only in the single read call). + +This typically manifests when doing partial reads of these files while the +memory map is being modified. Despite the races, we do provide the following +guarantees: + +1) The mapped addresses never go backwards, which implies no two + regions will ever overlap. +2) If there is something at a given vaddr during the entirety of the + life of the smaps/maps walk, there will be some output for it. + +The /proc/PID/smaps_rollup file includes the same fields as /proc/PID/smaps, +but their values are the sums of the corresponding values for all mappings of +the process. Additionally, it contains these fields: + +- Pss_Anon +- Pss_File +- Pss_Shmem + +They represent the proportional shares of anonymous, file, and shmem pages, as +described for smaps above. These fields are omitted in smaps since each +mapping identifies the type (anon, file, or shmem) of all pages it contains. +Thus all information in smaps_rollup can be derived from smaps, but at a +significantly higher cost. + +The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG +bits on both physical and virtual pages associated with a process, and the +soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst +for details). +To clear the bits for all the pages associated with the process:: + + > echo 1 > /proc/PID/clear_refs + +To clear the bits for the anonymous pages associated with the process:: + + > echo 2 > /proc/PID/clear_refs + +To clear the bits for the file mapped pages associated with the process:: + + > echo 3 > /proc/PID/clear_refs + +To clear the soft-dirty bit:: + + > echo 4 > /proc/PID/clear_refs + +To reset the peak resident set size ("high water mark") to the process's +current value:: + + > echo 5 > /proc/PID/clear_refs + +Any other value written to /proc/PID/clear_refs will have no effect. + +The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags +using /proc/kpageflags and number of times a page is mapped using +/proc/kpagecount. For detailed explanation, see +Documentation/admin-guide/mm/pagemap.rst. + +The /proc/pid/numa_maps is an extension based on maps, showing the memory +locality and binding policy, as well as the memory usage (in pages) of +each mapping. The output follows a general format where mapping details get +summarized separated by blank spaces, one mapping per each file line:: + + address policy mapping details + + 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4 + 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4 + 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4 + 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 + 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 + 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4 + 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4 + 320698b000 default file=/lib64/libc-2.12.so + 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4 + 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 + 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4 + 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4 + 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4 + 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048 + 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4 + 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4 + +Where: + +"address" is the starting address for the mapping; + +"policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst); + +"mapping details" summarizes mapping data such as mapping type, page usage counters, +node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page +size, in KB, that is backing the mapping up. + +1.2 Kernel data +--------------- + +Similar to the process entries, the kernel data files give information about +the running kernel. The files used to obtain this information are contained in +/proc and are listed in Table 1-5. Not all of these will be present in your +system. It depends on the kernel configuration and the loaded modules, which +files are there, and which are missing. + +.. table:: Table 1-5: Kernel info in /proc + + ============ =============================================================== + File Content + ============ =============================================================== + apm Advanced power management info + buddyinfo Kernel memory allocator information (see text) (2.5) + bus Directory containing bus specific information + cmdline Kernel command line + cpuinfo Info about the CPU + devices Available devices (block and character) + dma Used DMS channels + filesystems Supported filesystems + driver Various drivers grouped here, currently rtc (2.4) + execdomains Execdomains, related to security (2.4) + fb Frame Buffer devices (2.4) + fs File system parameters, currently nfs/exports (2.4) + ide Directory containing info about the IDE subsystem + interrupts Interrupt usage + iomem Memory map (2.4) + ioports I/O port usage + irq Masks for irq to cpu affinity (2.4)(smp?) + isapnp ISA PnP (Plug&Play) Info (2.4) + kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) + kmsg Kernel messages + ksyms Kernel symbol table + loadavg Load average of last 1, 5 & 15 minutes + locks Kernel locks + meminfo Memory info + misc Miscellaneous + modules List of loaded modules + mounts Mounted filesystems + net Networking info (see text) + pagetypeinfo Additional page allocator information (see text) (2.5) + partitions Table of partitions known to the system + pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, + decoupled by lspci (2.4) + rtc Real time clock + scsi SCSI info (see text) + slabinfo Slab pool info + softirqs softirq usage + stat Overall statistics + swaps Swap space utilization + sys See chapter 2 + sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) + tty Info of tty drivers + uptime Wall clock since boot, combined idle time of all cpus + version Kernel version + video bttv info of video resources (2.4) + vmallocinfo Show vmalloced areas + ============ =============================================================== + +You can, for example, check which interrupts are currently in use and what +they are used for by looking in the file /proc/interrupts:: + + > cat /proc/interrupts + CPU0 + 0: 8728810 XT-PIC timer + 1: 895 XT-PIC keyboard + 2: 0 XT-PIC cascade + 3: 531695 XT-PIC aha152x + 4: 2014133 XT-PIC serial + 5: 44401 XT-PIC pcnet_cs + 8: 2 XT-PIC rtc + 11: 8 XT-PIC i82365 + 12: 182918 XT-PIC PS/2 Mouse + 13: 1 XT-PIC fpu + 14: 1232265 XT-PIC ide0 + 15: 7 XT-PIC ide1 + NMI: 0 + +In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the +output of a SMP machine):: + + > cat /proc/interrupts + + CPU0 CPU1 + 0: 1243498 1214548 IO-APIC-edge timer + 1: 8949 8958 IO-APIC-edge keyboard + 2: 0 0 XT-PIC cascade + 5: 11286 10161 IO-APIC-edge soundblaster + 8: 1 0 IO-APIC-edge rtc + 9: 27422 27407 IO-APIC-edge 3c503 + 12: 113645 113873 IO-APIC-edge PS/2 Mouse + 13: 0 0 XT-PIC fpu + 14: 22491 24012 IO-APIC-edge ide0 + 15: 2183 2415 IO-APIC-edge ide1 + 17: 30564 30414 IO-APIC-level eth0 + 18: 177 164 IO-APIC-level bttv + NMI: 2457961 2457959 + LOC: 2457882 2457881 + ERR: 2155 + +NMI is incremented in this case because every timer interrupt generates a NMI +(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. + +LOC is the local interrupt counter of the internal APIC of every CPU. + +ERR is incremented in the case of errors in the IO-APIC bus (the bus that +connects the CPUs in a SMP system. This means that an error has been detected, +the IO-APIC automatically retry the transmission, so it should not be a big +problem, but you should read the SMP-FAQ. + +In 2.6.2* /proc/interrupts was expanded again. This time the goal was for +/proc/interrupts to display every IRQ vector in use by the system, not +just those considered 'most important'. The new vectors are: + +THR + interrupt raised when a machine check threshold counter + (typically counting ECC corrected errors of memory or cache) exceeds + a configurable threshold. Only available on some systems. + +TRM + a thermal event interrupt occurs when a temperature threshold + has been exceeded for the CPU. This interrupt may also be generated + when the temperature drops back to normal. + +SPU + a spurious interrupt is some interrupt that was raised then lowered + by some IO device before it could be fully processed by the APIC. Hence + the APIC sees the interrupt but does not know what device it came from. + For this case the APIC will generate the interrupt with a IRQ vector + of 0xff. This might also be generated by chipset bugs. + +RES, CAL, TLB] + rescheduling, call and TLB flush interrupts are + sent from one CPU to another per the needs of the OS. Typically, + their statistics are used by kernel developers and interested users to + determine the occurrence of interrupts of the given type. + +The above IRQ vectors are displayed only when relevant. For example, +the threshold vector does not exist on x86_64 platforms. Others are +suppressed when the system is a uniprocessor. As of this writing, only +i386 and x86_64 platforms support the new IRQ vector displays. + +Of some interest is the introduction of the /proc/irq directory to 2.4. +It could be used to set IRQ to CPU affinity, this means that you can "hook" an +IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the +irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and +prof_cpu_mask. + +For example:: + + > ls /proc/irq/ + 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask + 1 11 13 15 17 19 3 5 7 9 default_smp_affinity + > ls /proc/irq/0/ + smp_affinity + +smp_affinity is a bitmask, in which you can specify which CPUs can handle the +IRQ, you can set it by doing:: + + > echo 1 > /proc/irq/10/smp_affinity + +This means that only the first CPU will handle the IRQ, but you can also echo +5 which means that only the first and third CPU can handle the IRQ. + +The contents of each smp_affinity file is the same by default:: + + > cat /proc/irq/0/smp_affinity + ffffffff + +There is an alternate interface, smp_affinity_list which allows specifying +a cpu range instead of a bitmask:: + + > cat /proc/irq/0/smp_affinity_list + 1024-1031 + +The default_smp_affinity mask applies to all non-active IRQs, which are the +IRQs which have not yet been allocated/activated, and hence which lack a +/proc/irq/[0-9]* directory. + +The node file on an SMP system shows the node to which the device using the IRQ +reports itself as being attached. This hardware locality information does not +include information about any possible driver locality preference. + +prof_cpu_mask specifies which CPUs are to be profiled by the system wide +profiler. Default value is ffffffff (all cpus if there are only 32 of them). + +The way IRQs are routed is handled by the IO-APIC, and it's Round Robin +between all the CPUs which are allowed to handle it. As usual the kernel has +more info than you and does a better job than you, so the defaults are the +best choice for almost everyone. [Note this applies only to those IO-APIC's +that support "Round Robin" interrupt distribution.] + +There are three more important subdirectories in /proc: net, scsi, and sys. +The general rule is that the contents, or even the existence of these +directories, depend on your kernel configuration. If SCSI is not enabled, the +directory scsi may not exist. The same is true with the net, which is there +only when networking support is present in the running kernel. + +The slabinfo file gives information about memory usage at the slab level. +Linux uses slab pools for memory management above page level in version 2.2. +Commonly used objects have their own slab pool (such as network buffers, +directory cache, and so on). + +:: + + > cat /proc/buddyinfo + + Node 0, zone DMA 0 4 5 4 4 3 ... + Node 0, zone Normal 1 0 0 1 101 8 ... + Node 0, zone HighMem 2 0 0 1 1 0 ... + +External fragmentation is a problem under some workloads, and buddyinfo is a +useful tool for helping diagnose these problems. Buddyinfo will give you a +clue as to how big an area you can safely allocate, or why a previous +allocation failed. + +Each column represents the number of pages of a certain order which are +available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in +ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE +available in ZONE_NORMAL, etc... + +More information relevant to external fragmentation can be found in +pagetypeinfo:: + + > cat /proc/pagetypeinfo + Page block order: 9 + Pages per block: 512 + + Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10 + Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0 + Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 |