| .. 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 |
| 3.13 /proc/<pid>/fd - List of symlinks to open files |
| |
| 4 Configuring procfs |
| 4.1 Mount options |
| |
| 5 Filesystem behavior |
| |
| 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 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 |
| SpeculationIndirectBranch: conditional enabled |
| 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 detailed 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, or |
| the tracer is outside of the current pid namespace) |
| 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 |
| SpeculationIndirectBranch indirect branch speculation mode |
| 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 |
| [anon:<name>] a private anonymous mapping that has been |
| named by userspace |
| [anon_shmem:<name>] an anonymous shared memory mapping that has |
| been named by userspace |
| =================== =========================================== |
| |
| 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 |
| Pss_Dirty: 0 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. "Pss_Dirty" is the portion of PSS which |
| consists of dirty pages. ("Pss_Clean" is not included, but it can be |
| calculated by subtracting "Pss_Dirty" from "Pss".) |
| |
| 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 as well as the THP is PMD mappable or not - 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 |
| sf synchronous page fault |
| ar architecture specific flag |
| wf wipe on fork |
| 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 |
| bt arm64 BTI guarded page |
| mt arm64 MTE allocation tags are enabled |
| um userfaultfd missing tracking |
| uw userfaultfd wr-protect tracking |
| == ======================================= |
| |
| 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; |
| number of processes currently runnable (running or on ready queue); |
| total number of processes in system; |
| last pid created. |
| All fields are separated by one space except "number of |
| processes currently runnable" and "total number of processes |
| in system", which are separated by a slash ('/'). Example: |
| 0.61 0.61 0.55 3/828 22084 |
| 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 0 0 0 0 0 |
| Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2 |
| Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0 |
| Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0 |
| Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9 |
| Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0 |
| Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452 |
| Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0 |
| Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0 |
| |
| Number of blocks type Unmovable Reclaimable Movable Reserve Isolate |
| Node 0, zone DMA 2 0 5 1 0 |
| Node 0, zone DMA32 41 6 967 2 0 |
| |
| Fragmentation avoidance in the kernel works by grouping pages of different |
| migrate types into the same contiguous regions of memory called page blocks. |
| A page block is typically the size of the default hugepage size, e.g. 2MB on |
| X86-64. By keeping pages grouped based on their ability to move, the kernel |
| can reclaim pages within a page block to satisfy a high-order allocation. |
| |
| The pagetypinfo begins with information on the size of a page block. It |
| then gives the same type of information as buddyinfo except broken down |
| by migrate-type and finishes with details on how many page blocks of each |
| type exist. |
| |
| If min_free_kbytes has been tuned correctly (recommendations made by hugeadm |
| from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can |
| make an estimate of the likely number of huge pages that can be allocated |
| at a given point in time. All the "Movable" blocks should be allocatable |
| unless memory has been mlock()'d. Some of the Reclaimable blocks should |
| also be allocatable although a lot of filesystem metadata may have to be |
| reclaimed to achieve this. |
| |
| |
| meminfo |
| ~~~~~~~ |
| |
| Provides information about distribution and utilization of memory. This |
| varies by architecture and compile options. Some of the counters reported |
| here overlap. The memory reported by the non overlapping counters may not |
| add up to the overall memory usage and the difference for some workloads |
| can be substantial. In many cases there are other means to find out |
| additional memory using subsystem specific interfaces, for instance |
| /proc/net/sockstat for TCP memory allocations. |
| |
| Example output. You may not have all of these fields. |
| |
| :: |
| |
| > cat /proc/meminfo |
| |
| MemTotal: 32858820 kB |
| MemFree: 21001236 kB |
| MemAvailable: 27214312 kB |
| Buffers: 581092 kB |
| Cached: 5587612 kB |
| SwapCached: 0 kB |
| Active: 3237152 kB |
| Inactive: 7586256 kB |
| Active(anon): 94064 kB |
| Inactive(anon): 4570616 kB |
| Active(file): 3143088 kB |
| Inactive(file): 3015640 kB |
| Unevictable: 0 kB |
| Mlocked: 0 kB |
| SwapTotal: 0 kB |
| SwapFree: 0 kB |
| Zswap: 1904 kB |
| Zswapped: 7792 kB |
| Dirty: 12 kB |
| Writeback: 0 kB |
| AnonPages: 4654780 kB |
| Mapped: 266244 kB |
| Shmem: 9976 kB |
| KReclaimable: 517708 kB |
| Slab: 660044 kB |
| SReclaimable: 517708 kB |
| SUnreclaim: 142336 kB |
| KernelStack: 11168 kB |
| PageTables: 20540 kB |
| SecPageTables: 0 kB |
| NFS_Unstable: 0 kB |
| Bounce: 0 kB |
| WritebackTmp: 0 kB |
| CommitLimit: 16429408 kB |
| Committed_AS: 7715148 kB |
| VmallocTotal: 34359738367 kB |
| VmallocUsed: 40444 kB |
| VmallocChunk: 0 kB |
| Percpu: 29312 kB |
| HardwareCorrupted: 0 kB |
| AnonHugePages: 4149248 kB |
| ShmemHugePages: 0 kB |
| ShmemPmdMapped: 0 kB |
| FileHugePages: 0 kB |
| FilePmdMapped: 0 kB |
| CmaTotal: 0 kB |
| CmaFree: 0 kB |
| HugePages_Total: 0 |
| HugePages_Free: 0 |
| HugePages_Rsvd: 0 |
| HugePages_Surp: 0 |
| Hugepagesize: 2048 kB |
| Hugetlb: 0 kB |
| DirectMap4k: 401152 kB |
| DirectMap2M: 10008576 kB |
| DirectMap1G: 24117248 kB |
| |
| MemTotal |
| Total usable RAM (i.e. physical RAM minus a few reserved |
| bits and the kernel binary code) |
| MemFree |
| Total free RAM. On highmem systems, the sum of LowFree+HighFree |
| MemAvailable |
| An estimate of how much memory is available for starting new |
| applications, without swapping. Calculated from MemFree, |
| SReclaimable, the size of the file LRU lists, and the low |
| watermarks in each zone. |
| The estimate takes into account that the system needs some |
| page cache to function well, and that not all reclaimable |
| slab will be reclaimable, due to items being in use. The |
| impact of those factors will vary from system to system. |
| Buffers |
| Relatively temporary storage for raw disk blocks |
| shouldn't get tremendously large (20MB or so) |
| Cached |
| In-memory cache for files read from the disk (the |
| pagecache) as well as tmpfs & shmem. |
| Doesn't include SwapCached. |
| SwapCached |
| Memory that once was swapped out, is swapped back in but |
| still also is in the swapfile (if memory is needed it |
| doesn't need to be swapped out AGAIN because it is already |
| in the swapfile. This saves I/O) |
| Active |
| Memory that has been used more recently and usually not |
| reclaimed unless absolutely necessary. |
| Inactive |
| Memory which has been less recently used. It is more |
| eligible to be reclaimed for other purposes |
| Unevictable |
| Memory allocated for userspace which cannot be reclaimed, such |
| as mlocked pages, ramfs backing pages, secret memfd pages etc. |
| Mlocked |
| Memory locked with mlock(). |
| HighTotal, HighFree |
| Highmem is all memory above ~860MB of physical memory. |
| Highmem areas are for use by userspace programs, or |
| for the pagecache. The kernel must use tricks to access |
| this memory, making it slower to access than lowmem. |
| LowTotal, LowFree |
| Lowmem is memory which can be used for everything that |
| highmem can be used for, but it is also available for the |
| kernel's use for its own data structures. Among many |
| other things, it is where everything from the Slab is |
| allocated. Bad things happen when you're out of lowmem. |
| SwapTotal |
| total amount of swap space available |
| SwapFree |
| Memory which has been evicted from RAM, and is temporarily |
| on the disk |
| Zswap |
| Memory consumed by the zswap backend (compressed size) |
| Zswapped |
| Amount of anonymous memory stored in zswap (original size) |
| Dirty |
| Memory which is waiting to get written back to the disk |
| Writeback |
| Memory which is actively being written back to the disk |
| AnonPages |
| Non-file backed pages mapped into userspace page tables |
| Mapped |
| files which have been mmaped, such as libraries |
| Shmem |
| Total memory used by shared memory (shmem) and tmpfs |
| KReclaimable |
| Kernel allocations that the kernel will attempt to reclaim |
| under memory pressure. Includes SReclaimable (below), and other |
| direct allocations with a shrinker. |
| Slab |
| in-kernel data structures cache |
| SReclaimable |
| Part of Slab, that might be reclaimed, such as caches |
| SUnreclaim |
| Part of Slab, that cannot be reclaimed on memory pressure |
| KernelStack |
| Memory consumed by the kernel stacks of all tasks |
| PageTables |
| Memory consumed by userspace page tables |
| SecPageTables |
| Memory consumed by secondary page tables, this currently |
| currently includes KVM mmu allocations on x86 and arm64. |
| NFS_Unstable |
| Always zero. Previous counted pages which had been written to |
| the server, but has not been committed to stable storage. |
| Bounce |
| Memory used for block device "bounce buffers" |
| WritebackTmp |
| Memory used by FUSE for temporary writeback buffers |
| CommitLimit |
| Based on the overcommit ratio ('vm.overcommit_ratio'), |
| this is the total amount of memory currently available to |
| be allocated on the system. This limit is only adhered to |
| if strict overcommit accounting is enabled (mode 2 in |
| 'vm.overcommit_memory'). |
| |
| The CommitLimit is calculated with the following formula:: |
| |
| CommitLimit = ([total RAM pages] - [total huge TLB pages]) * |
| overcommit_ratio / 100 + [total swap pages] |
| |
| For example, on a system with 1G of physical RAM and 7G |
| of swap with a `vm.overcommit_ratio` of 30 it would |
| yield a CommitLimit of 7.3G. |
| |
| For more details, see the memory overcommit documentation |
| in mm/overcommit-accounting. |
| Committed_AS |
| The amount of memory presently allocated on the system. |
| The committed memory is a sum of all of the memory which |
| has been allocated by processes, even if it has not been |
| "used" by them as of yet. A process which malloc()'s 1G |
| of memory, but only touches 300M of it will show up as |
| using 1G. This 1G is memory which has been "committed" to |
| by the VM and can be used at any time by the allocating |
| application. With strict overcommit enabled on the system |
| (mode 2 in 'vm.overcommit_memory'), allocations which would |
| exceed the CommitLimit (detailed above) will not be permitted. |
| This is useful if one needs to guarantee that processes will |
| not fail due to lack of memory once that memory has been |
| successfully allocated. |
| VmallocTotal |
| total size of vmalloc virtual address space |
| VmallocUsed |
| amount of vmalloc area which is used |
| VmallocChunk |
| largest contiguous block of vmalloc area which is free |
| Percpu |
| Memory allocated to the percpu allocator used to back percpu |
| allocations. This stat excludes the cost of metadata. |
| HardwareCorrupted |
| The amount of RAM/memory in KB, the kernel identifies as |
| corrupted. |
| AnonHugePages |
| Non-file backed huge pages mapped into userspace page tables |
| ShmemHugePages |
| Memory used by shared memory (shmem) and tmpfs allocated |
| with huge pages |
| ShmemPmdMapped |
| Shared memory mapped into userspace with huge pages |
| FileHugePages |
| Memory used for filesystem data (page cache) allocated |
| with huge pages |
| FilePmdMapped |
| Page cache mapped into userspace with huge pages |
| CmaTotal |
| Memory reserved for the Contiguous Memory Allocator (CMA) |
| CmaFree |
| Free remaining memory in the CMA reserves |
| HugePages_Total, HugePages_Free, HugePages_Rsvd, HugePages_Surp, Hugepagesize, Hugetlb |
| See Documentation/admin-guide/mm/hugetlbpage.rst. |
| DirectMap4k, DirectMap2M, DirectMap1G |
| Breakdown of page table sizes used in the kernel's |
| identity mapping of RAM |
| |
| vmallocinfo |
| ~~~~~~~~~~~ |
| |
| Provides information about vmalloced/vmaped areas. One line per area, |
| containing the virtual address range of the area, size in bytes, |
| caller information of the creator, and optional information depending |
| on the kind of area: |
| |
| ========== =================================================== |
| pages=nr number of pages |
| phys=addr if a physical address was specified |
| ioremap I/O mapping (ioremap() and friends) |
| vmalloc vmalloc() area |
| vmap vmap()ed pages |
| user VM_USERMAP area |
| vpages buffer for pages pointers was vmalloced (huge area) |
| N<node>=nr (Only on NUMA kernels) |
| Number of pages allocated on memory node <node> |
| ========== =================================================== |
| |
| :: |
| |
| > cat /proc/vmallocinfo |
| 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... |
| /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 |
| 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... |
| /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 |
| 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... |
| phys=7fee8000 ioremap |
| 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... |
| phys=7fee7000 ioremap |
| 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 |
| 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... |
| /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 |
| 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... |
| pages=2 vmalloc N1=2 |
| 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... |
| /0x130 [x_tables] pages=4 vmalloc N0=4 |
| 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... |
| pages=14 vmalloc N2=14 |
| 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... |
| pages=4 vmalloc N1=4 |
| 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... |
| pages=2 vmalloc N1=2 |
| 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... |
| pages=10 vmalloc N0=10 |
| |
| |
| softirqs |
| ~~~~~~~~ |
| |
| Provides counts of softirq handlers serviced since boot time, for each CPU. |
| |
| :: |
| |
| > cat /proc/softirqs |
| CPU0 CPU1 CPU2 CPU3 |
| HI: 0 0 0 0 |
| TIMER: 27166 27120 27097 27034 |
| NET_TX: 0 0 0 17 |
| NET_RX: 42 0 0 39 |
| BLOCK: 0 0 107 1121 |
| TASKLET: 0 0 0 290 |
| SCHED: 27035 26983 26971 26746 |
| HRTIMER: 0 0 0 0 |
| RCU: 1678 1769 2178 2250 |
| |
| 1.3 Networking info in /proc/net |
| -------------------------------- |
| |
| The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the |
| additional values you get for IP version 6 if you configure the kernel to |
| support this. Table 1-9 lists the files and their meaning. |
| |
| |
| .. table:: Table 1-8: IPv6 info in /proc/net |
| |
| ========== ===================================================== |
| File Content |
| ========== ===================================================== |
| udp6 UDP sockets (IPv6) |
| tcp6 TCP sockets (IPv6) |
| raw6 Raw device statistics (IPv6) |
| igmp6 IP multicast addresses, which this host joined (IPv6) |
| if_inet6 List of IPv6 interface addresses |
| ipv6_route Kernel routing table for IPv6 |
| rt6_stats Global IPv6 routing tables statistics |
| sockstat6 Socket statistics (IPv6) |
| snmp6 Snmp data (IPv6) |
| ========== ===================================================== |
| |
| .. table:: Table 1-9: Network info in /proc/net |
| |
| ============= ================================================================ |
| File Content |
| ============= ================================================================ |
| arp Kernel ARP table |
| dev network devices with statistics |
| dev_mcast the Layer2 multicast groups a device is listening too |
| (interface index, label, number of references, number of bound |
| addresses). |
| dev_stat network device status |
| ip_fwchains Firewall chain linkage |
| ip_fwnames Firewall chain names |
| ip_masq Directory containing the masquerading tables |
| ip_masquerade Major masquerading table |
| netstat Network statistics |
| raw raw device statistics |
| route Kernel routing table |
| rpc Directory containing rpc info |
| rt_cache Routing cache |
| snmp SNMP data |
| sockstat Socket statistics |
| softnet_stat Per-CPU incoming packets queues statistics of online CPUs |
| tcp TCP sockets |
| udp UDP sockets |
| unix UNIX domain sockets |
| wireless Wireless interface data (Wavelan etc) |
| igmp IP multicast addresses, which this host joined |
| psched Global packet scheduler parameters. |
| netlink List of PF_NETLINK sockets |
| ip_mr_vifs List of multicast virtual interfaces |
| ip_mr_cache List of multicast routing cache |
| ============= ================================================================ |
| |
| You can use this information to see which network devices are available in |
| your system and how much traffic was routed over those devices:: |
| |
| > cat /proc/net/dev |
| Inter-|Receive |[... |
| face |bytes packets errs drop fifo frame compressed multicast|[... |
| lo: 908188 5596 0 0 0 0 0 0 [... |
| ppp0:15475140 20721 410 0 0 410 0 0 [... |
| eth0: 614530 7085 0 0 0 0 0 1 [... |
| |
| ...] Transmit |
| ...] bytes packets errs drop fifo colls carrier compressed |
| ...] 908188 5596 0 0 0 0 0 0 |
| ...] 1375103 17405 0 0 0 0 0 0 |
| ...] 1703981 5535 0 0 0 3 0 0 |
| |
| In addition, each Channel Bond interface has its own directory. For |
| example, the bond0 device will have a directory called /proc/net/bond0/. |
| It will contain information that is specific to that bond, such as the |
| current slaves of the bond, the link status of the slaves, and how |
| many times the slaves link has failed. |
| |
| 1.4 SCSI info |
| ------------- |
| |
| If you have a SCSI host adapter in your system, you'll find a subdirectory |
| named after the driver for this adapter in /proc/scsi. You'll also see a list |
| of all recognized SCSI devices in /proc/scsi:: |
| |
| >cat /proc/scsi/scsi |
| Attached devices: |
| Host: scsi0 Channel: 00 Id: 00 Lun: 00 |
| Vendor: IBM Model: DGHS09U Rev: 03E0 |
| Type: Direct-Access ANSI SCSI revision: 03 |
| Host: scsi0 Channel: 00 Id: 06 Lun: 00 |
| Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 |
| Type: CD-ROM ANSI SCSI revision: 02 |
| |
| |
| The directory named after the driver has one file for each adapter found in |
| the system. These files contain information about the controller, including |
| the used IRQ and the IO address range. The amount of information shown is |
| dependent on the adapter you use. The example shows the output for an Adaptec |
| AHA-2940 SCSI adapter:: |
| |
| > cat /proc/scsi/aic7xxx/0 |
| |
| Adaptec AIC7xxx driver version: 5.1.19/3.2.4 |
| Compile Options: |
| TCQ Enabled By Default : Disabled |
| AIC7XXX_PROC_STATS : Disabled |
| AIC7XXX_RESET_DELAY : 5 |
| Adapter Configuration: |
| SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter |
| Ultra Wide Controller |
| PCI MMAPed I/O Base: 0xeb001000 |
| Adapter SEEPROM Config: SEEPROM found and used. |
| Adaptec SCSI BIOS: Enabled |
| IRQ: 10 |
| SCBs: Active 0, Max Active 2, |
| Allocated 15, HW 16, Page 255 |
| Interrupts: 160328 |
| BIOS Control Word: 0x18b6 |
| Adapter Control Word: 0x005b |
| Extended Translation: Enabled |
| Disconnect Enable Flags: 0xffff |
| Ultra Enable Flags: 0x0001 |
| Tag Queue Enable Flags: 0x0000 |
| Ordered Queue Tag Flags: 0x0000 |
| Default Tag Queue Depth: 8 |
| Tagged Queue By Device array for aic7xxx host instance 0: |
| {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} |
| Actual queue depth per device for aic7xxx host instance 0: |
| {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} |
| Statistics: |
| (scsi0:0:0:0) |
| Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 |
| Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) |
| Total transfers 160151 (74577 reads and 85574 writes) |
| (scsi0:0:6:0) |
| Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 |
| Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) |
| Total transfers 0 (0 reads and 0 writes) |
| |
| |
| 1.5 Parallel port info in /proc/parport |
| --------------------------------------- |
| |
| The directory /proc/parport contains information about the parallel ports of |
| your system. It has one subdirectory for each port, named after the port |
| number (0,1,2,...). |
| |
| These directories contain the four files shown in Table 1-10. |
| |
| |
| .. table:: Table 1-10: Files in /proc/parport |
| |
| ========= ==================================================================== |
| File Content |
| ========= ==================================================================== |
| autoprobe Any IEEE-1284 device ID information that has been acquired. |
| devices list of the device drivers using that port. A + will appear by the |
| name of the device currently using the port (it might not appear |
| against any). |
| hardware Parallel port's base address, IRQ line and DMA channel. |
| irq IRQ that parport is using for that port. This is in a separate |
| file to allow you to alter it by writing a new value in (IRQ |
| number or none). |
| ========= ==================================================================== |
| |
| 1.6 TTY info in /proc/tty |
| ------------------------- |
| |
| Information about the available and actually used tty's can be found in the |
| directory /proc/tty. You'll find entries for drivers and line disciplines in |
| this directory, as shown in Table 1-11. |
| |
| |
| .. table:: Table 1-11: Files in /proc/tty |
| |
| ============= ============================================== |
| File Content |
| ============= ============================================== |
| drivers list of drivers and their usage |
| ldiscs registered line disciplines |
| driver/serial usage statistic and status of single tty lines |
| ============= ============================================== |
| |
| To see which tty's are currently in use, you can simply look into the file |
| /proc/tty/drivers:: |
| |
| > cat /proc/tty/drivers |
| pty_slave /dev/pts 136 0-255 pty:slave |
| pty_master /dev/ptm 128 0-255 pty:master |
| pty_slave /dev/ttyp 3 0-255 pty:slave |
| pty_master /dev/pty 2 0-255 pty:master |
| serial /dev/cua 5 64-67 serial:callout |
| serial /dev/ttyS 4 64-67 serial |
| /dev/tty0 /dev/tty0 4 0 system:vtmaster |
| /dev/ptmx /dev/ptmx 5 2 system |
| /dev/console /dev/console 5 1 system:console |
| /dev/tty /dev/tty 5 0 system:/dev/tty |
| unknown /dev/tty 4 1-63 console |
| |
| |
| 1.7 Miscellaneous kernel statistics in /proc/stat |
| ------------------------------------------------- |
| |
| Various pieces of information about kernel activity are available in the |
| /proc/stat file. All of the numbers reported in this file are aggregates |
| since the system first booted. For a quick look, simply cat the file:: |
| |
| > cat /proc/stat |
| cpu 2255 34 2290 22625563 6290 127 456 0 0 0 |
| cpu0 1132 34 1441 11311718 3675 127 438 0 0 0 |
| cpu1 1123 0 849 11313845 2614 0 18 0 0 0 |
| intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] |
| ctxt 1990473 |
| btime 1062191376 |
| processes 2915 |
| procs_running 1 |
| procs_blocked 0 |
| softirq 183433 0 21755 12 39 1137 231 21459 2263 |
| |
| The very first "cpu" line aggregates the numbers in all of the other "cpuN" |
| lines. These numbers identify the amount of time the CPU has spent performing |
| different kinds of work. Time units are in USER_HZ (typically hundredths of a |
| second). The meanings of the columns are as follows, from left to right: |
| |
| - user: normal processes executing in user mode |
| - nice: niced processes executing in user mode |
| - system: processes executing in kernel mode |
| - idle: twiddling thumbs |
| - iowait: In a word, iowait stands for waiting for I/O to complete. But there |
| are several problems: |
| |
| 1. CPU will not wait for I/O to complete, iowait is the time that a task is |
| waiting for I/O to complete. When CPU goes into idle state for |
| outstanding task I/O, another task will be scheduled on this CPU. |
| 2. In a multi-core CPU, the task waiting for I/O to complete is not running |
| on any CPU, so the iowait of each CPU is difficult to calculate. |
| 3. The value of iowait field in /proc/stat will decrease in certain |
| conditions. |
| |
| So, the iowait is not reliable by reading from /proc/stat. |
| - irq: servicing interrupts |
| - softirq: servicing softirqs |
| - steal: involuntary wait |
| - guest: running a normal guest |
| - guest_nice: running a niced guest |
| |
| The "intr" line gives counts of interrupts serviced since boot time, for each |
| of the possible system interrupts. The first column is the total of all |
| interrupts serviced including unnumbered architecture specific interrupts; |
| each subsequent column is the total for that particular numbered interrupt. |
| Unnumbered interrupts are not shown, only summed into the total. |
| |
| The "ctxt" line gives the total number of context switches across all CPUs. |
| |
| The "btime" line gives the time at which the system booted, in seconds since |
| the Unix epoch. |
| |
| The "processes" line gives the number of processes and threads created, which |
| includes (but is not limited to) those created by calls to the fork() and |
| clone() system calls. |
| |
| The "procs_running" line gives the total number of threads that are |
| running or ready to run (i.e., the total number of runnable threads). |
| |
| The "procs_blocked" line gives the number of processes currently blocked, |
| waiting for I/O to complete. |
| |
| The "softirq" line gives counts of softirqs serviced since boot time, for each |
| of the possible system softirqs. The first column is the total of all |
| softirqs serviced; each subsequent column is the total for that particular |
| softirq. |
| |
| |
| 1.8 Ext4 file system parameters |
| ------------------------------- |
| |
| Information about mounted ext4 file systems can be found in |
| /proc/fs/ext4. Each mounted filesystem will have a directory in |
| /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or |
| /proc/fs/ext4/dm-0). The files in each per-device directory are shown |
| in Table 1-12, below. |
| |
| .. table:: Table 1-12: Files in /proc/fs/ext4/<devname> |
| |
| ============== ========================================================== |
| File Content |
| mb_groups details of multiblock allocator buddy cache of free blocks |
| ============== ========================================================== |
| |
| 1.9 /proc/consoles |
| ------------------- |
| Shows registered system console lines. |
| |
| To see which character device lines are currently used for the system console |
| /dev/console, you may simply look into the file /proc/consoles:: |
| |
| > cat /proc/consoles |
| tty0 -WU (ECp) 4:7 |
| ttyS0 -W- (Ep) 4:64 |
| |
| The columns are: |
| |
| +--------------------+-------------------------------------------------------+ |
| | device | name of the device | |
| +====================+=======================================================+ |
| | operations | * R = can do read operations | |
| | | * W = can do write operations | |
| | | * U = can do unblank | |
| +--------------------+-------------------------------------------------------+ |
| | flags | * E = it is enabled | |
| | | * C = it is preferred console | |
| | | * B = it is primary boot console | |
| | | * p = it is used for printk buffer | |
| | | * b = it is not a TTY but a Braille device | |
| | | * a = it is safe to use when cpu is offline | |
| +--------------------+-------------------------------------------------------+ |
| | major:minor | major and minor number of the device separated by a | |
| | | colon | |
| +--------------------+-------------------------------------------------------+ |
| |
| Summary |
| ------- |
| |
| The /proc file system serves information about the running system. It not only |
| allows access to process data but also allows you to request the kernel status |
| by reading files in the hierarchy. |
| |
| The directory structure of /proc reflects the types of information and makes |
| it easy, if not obvious, where to look for specific data. |
| |
| Chapter 2: Modifying System Parameters |
| ====================================== |
| |
| In This Chapter |
| --------------- |
| |
| * Modifying kernel parameters by writing into files found in /proc/sys |
| * Exploring the files which modify certain parameters |
| * Review of the /proc/sys file tree |
| |
| ------------------------------------------------------------------------------ |
| |
| A very interesting part of /proc is the directory /proc/sys. This is not only |
| a source of information, it also allows you to change parameters within the |
| kernel. Be very careful when attempting this. You can optimize your system, |
| but you can also cause it to crash. Never alter kernel parameters on a |
| production system. Set up a development machine and test to make sure that |
| everything works the way you want it to. You may have no alternative but to |
| reboot the machine once an error has been made. |
| |
| To change a value, simply echo the new value into the file. |
| You need to be root to do this. You can create your own boot script |
| to perform this every time your system boots. |
| |
| The files in /proc/sys can be used to fine tune and monitor miscellaneous and |
| general things in the operation of the Linux kernel. Since some of the files |
| can inadvertently disrupt your system, it is advisable to read both |
| documentation and source before actually making adjustments. In any case, be |
| very careful when writing to any of these files. The entries in /proc may |
| change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt |
| review the kernel documentation in the directory /usr/src/linux/Documentation. |
| This chapter is heavily based on the documentation included in the pre 2.2 |
| kernels, and became part of it in version 2.2.1 of the Linux kernel. |
| |
| Please see: Documentation/admin-guide/sysctl/ directory for descriptions of these |
| entries. |
| |
| Summary |
| ------- |
| |
| Certain aspects of kernel behavior can be modified at runtime, without the |
| need to recompile the kernel, or even to reboot the system. The files in the |
| /proc/sys tree can not only be read, but also modified. You can use the echo |
| command to write value into these files, thereby changing the default settings |
| of the kernel. |
| |
| |
| Chapter 3: Per-process Parameters |
| ================================= |
| |
| 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score |
| -------------------------------------------------------------------------------- |
| |
| These files can be used to adjust the badness heuristic used to select which |
| process gets killed in out of memory (oom) conditions. |
| |
| The badness heuristic assigns a value to each candidate task ranging from 0 |
| (never kill) to 1000 (always kill) to determine which process is targeted. The |
| units are roughly a proportion along that range of allowed memory the process |
| may allocate from based on an estimation of its current memory and swap use. |
| For example, if a task is using all allowed memory, its badness score will be |
| 1000. If it is using half of its allowed memory, its score will be 500. |
| |
| The amount of "allowed" memory depends on the context in which the oom killer |
| was called. If it is due to the memory assigned to the allocating task's cpuset |
| being exhausted, the allowed memory represents the set of mems assigned to that |
| cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed |
| memory represents the set of mempolicy nodes. If it is due to a memory |
| limit (or swap limit) being reached, the allowed memory is that configured |
| limit. Finally, if it is due to the entire system being out of memory, the |
| allowed memory represents all allocatable resources. |
| |
| The value of /proc/<pid>/oom_score_adj is added to the badness score before it |
| is used to determine which task to kill. Acceptable values range from -1000 |
| (OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to |
| polarize the preference for oom killing either by always preferring a certain |
| task or completely disabling it. The lowest possible value, -1000, is |
| equivalent to disabling oom killing entirely for that task since it will always |
| report a badness score of 0. |
| |
| Consequently, it is very simple for userspace to define the amount of memory to |
| consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for |
| example, is roughly equivalent to allowing the remainder of tasks sharing the |
| same system, cpuset, mempolicy, or memory controller resources to use at least |
| 50% more memory. A value of -500, on the other hand, would be roughly |
| equivalent to discounting 50% of the task's allowed memory from being considered |
| as scoring against the task. |
| |
| For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also |
| be used to tune the badness score. Its acceptable values range from -16 |
| (OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17 |
| (OOM_DISABLE) to disable oom killing entirely for that task. Its value is |
| scaled linearly with /proc/<pid>/oom_score_adj. |
| |
| The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last |
| value set by a CAP_SYS_RESOURCE process. To reduce the value any lower |
| requires CAP_SYS_RESOURCE. |
| |
| |
| 3.2 /proc/<pid>/oom_score - Display current oom-killer score |
| ------------------------------------------------------------- |
| |
| This file can be used to check the current score used by the oom-killer for |
| any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which |
| process should be killed in an out-of-memory situation. |
| |
| Please note that the exported value includes oom_score_adj so it is |
| effectively in range [0,2000]. |
| |
| |
| 3.3 /proc/<pid>/io - Display the IO accounting fields |
| ------------------------------------------------------- |
| |
| This file contains IO statistics for each running process. |
| |
| Example |
| ~~~~~~~ |
| |
| :: |
| |
| test:/tmp # dd if=/dev/zero of=/tmp/test.dat & |
| [1] 3828 |
| |
| test:/tmp # cat /proc/3828/io |
| rchar: 323934931 |
| wchar: 323929600 |
| syscr: 632687 |
| syscw: 632675 |
| read_bytes: 0 |
| write_bytes: 323932160 |
| cancelled_write_bytes: 0 |
| |
| |
| Description |
| ~~~~~~~~~~~ |
| |
| rchar |
| ^^^^^ |
| |
| I/O counter: chars read |
| The number of bytes which this task has caused to be read from storage. This |
| is simply the sum of bytes which this process passed to read() and pread(). |
| It includes things like tty IO and it is unaffected by whether or not actual |
| physical disk IO was required (the read might have been satisfied from |
| pagecache). |
| |
| |
| wchar |
| ^^^^^ |
| |
| I/O counter: chars written |
| The number of bytes which this task has caused, or shall cause to be written |
| to disk. Similar caveats apply here as with rchar. |
| |
| |
| syscr |
| ^^^^^ |
| |
| I/O counter: read syscalls |
| Attempt to count the number of read I/O operations, i.e. syscalls like read() |
| and pread(). |
| |
| |
| syscw |
| ^^^^^ |
| |
| I/O counter: write syscalls |
| Attempt to count the number of write I/O operations, i.e. syscalls like |
| write() and pwrite(). |
| |
| |
| read_bytes |
| ^^^^^^^^^^ |
| |
| I/O counter: bytes read |
| Attempt to count the number of bytes which this process really did cause to |
| be fetched from the storage layer. Done at the submit_bio() level, so it is |
| accurate for block-backed filesystems. <please add status regarding NFS and |
| CIFS at a later time> |
| |
| |
| write_bytes |
| ^^^^^^^^^^^ |
| |
| I/O counter: bytes written |
| Attempt to count the number of bytes which this process caused to be sent to |
| the storage layer. This is done at page-dirtying time. |
| |
| |
| cancelled_write_bytes |
| ^^^^^^^^^^^^^^^^^^^^^ |
| |
| The big inaccuracy here is truncate. If a process writes 1MB to a file and |
| then deletes the file, it will in fact perform no writeout. But it will have |
| been accounted as having caused 1MB of write. |
| In other words: The number of bytes which this process caused to not happen, |
| by truncating pagecache. A task can cause "negative" IO too. If this task |
| truncates some dirty pagecache, some IO which another task has been accounted |
| for (in its write_bytes) will not be happening. We _could_ just subtract that |
| from the truncating task's write_bytes, but there is information loss in doing |
| that. |
| |
| |
| .. Note:: |
| |
| At its current implementation state, this is a bit racy on 32-bit machines: |
| if process A reads process B's /proc/pid/io while process B is updating one |
| of those 64-bit counters, process A could see an intermediate result. |
| |
| |
| More information about this can be found within the taskstats documentation in |
| Documentation/accounting. |
| |
| 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings |
| --------------------------------------------------------------- |
| When a process is dumped, all anonymous memory is written to a core file as |
| long as the size of the core file isn't limited. But sometimes we don't want |
| to dump some memory segments, for example, huge shared memory or DAX. |
| Conversely, sometimes we want to save file-backed memory segments into a core |
| file, not only the individual files. |
| |
| /proc/<pid>/coredump_filter allows you to customize which memory segments |
| will be dumped when the <pid> process is dumped. coredump_filter is a bitmask |
| of memory types. If a bit of the bitmask is set, memory segments of the |
| corresponding memory type are dumped, otherwise they are not dumped. |
| |
| The following 9 memory types are supported: |
| |
| - (bit 0) anonymous private memory |
| - (bit 1) anonymous shared memory |
| - (bit 2) file-backed private memory |
| - (bit 3) file-backed shared memory |
| - (bit 4) ELF header pages in file-backed private memory areas (it is |
| effective only if the bit 2 is cleared) |
| - (bit 5) hugetlb private memory |
| - (bit 6) hugetlb shared memory |
| - (bit 7) DAX private memory |
| - (bit 8) DAX shared memory |
| |
| Note that MMIO pages such as frame buffer are never dumped and vDSO pages |
| are always dumped regardless of the bitmask status. |
| |
| Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is |
| only affected by bit 5-6, and DAX is only affected by bits 7-8. |
| |
| The default value of coredump_filter is 0x33; this means all anonymous memory |
| segments, ELF header pages and hugetlb private memory are dumped. |
| |
| If you don't want to dump all shared memory segments attached to pid 1234, |
| write 0x31 to the process's proc file:: |
| |
| $ echo 0x31 > /proc/1234/coredump_filter |
| |
| When a new process is created, the process inherits the bitmask status from its |
| parent. It is useful to set up coredump_filter before the program runs. |
| For example:: |
| |
| $ echo 0x7 > /proc/self/coredump_filter |
| $ ./some_program |
| |
| 3.5 /proc/<pid>/mountinfo - Information about mounts |
| -------------------------------------------------------- |
| |
| This file contains lines of the form:: |
| |
| 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue |
| (1)(2)(3) (4) (5) (6) (n…m) (m+1)(m+2) (m+3) (m+4) |
| |
| (1) mount ID: unique identifier of the mount (may be reused after umount) |
| (2) parent ID: ID of parent (or of self for the top of the mount tree) |
| (3) major:minor: value of st_dev for files on filesystem |
| (4) root: root of the mount within the filesystem |
| (5) mount point: mount point relative to the process's root |
| (6) mount options: per mount options |
| (n…m) optional fields: zero or more fields of the form "tag[:value]" |
| (m+1) separator: marks the end of the optional fields |
| (m+2) filesystem type: name of filesystem of the form "type[.subtype]" |
| (m+3) mount source: filesystem specific information or "none" |
| (m+4) super options: per super block options |
| |
| Parsers should ignore all unrecognised optional fields. Currently the |
| possible optional fields are: |
| |
| ================ ============================================================== |
| shared:X mount is shared in peer group X |
| master:X mount is slave to peer group X |
| propagate_from:X mount is slave and receives propagation from peer group X [#]_ |
| unbindable mount is unbindable |
| ================ ============================================================== |
| |
| .. [#] X is the closest dominant peer group under the process's root. If |
| X is the immediate master of the mount, or if there's no dominant peer |
| group under the same root, then only the "master:X" field is present |
| and not the "propagate_from:X" field. |
| |
| For more information on mount propagation see: |
| |
| Documentation/filesystems/sharedsubtree.rst |
| |
| |
| 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm |
| -------------------------------------------------------- |
| These files provide a method to access a task's comm value. It also allows for |
| a task to set its own or one of its thread siblings comm value. The comm value |
| is limited in size compared to the cmdline value, so writing anything longer |
| then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated |
| comm value. |
| |
| |
| 3.7 /proc/<pid>/task/<tid>/children - Information about task children |
| ------------------------------------------------------------------------- |
| This file provides a fast way to retrieve first level children pids |
| of a task pointed by <pid>/<tid> pair. The format is a space separated |
| stream of pids. |
| |
| Note the "first level" here -- if a child has its own children they will |
| not be listed here; one needs to read /proc/<children-pid>/task/<tid>/children |
| to obtain the descendants. |
| |
| Since this interface is intended to be fast and cheap it doesn't |
| guarantee to provide precise results and some children might be |
| skipped, especially if they've exited right after we printed their |
| pids, so one needs to either stop or freeze processes being inspected |
| if precise results are needed. |
| |
| |
| 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file |
| --------------------------------------------------------------- |
| This file provides information associated with an opened file. The regular |
| files have at least four fields -- 'pos', 'flags', 'mnt_id' and 'ino'. |
| The 'pos' represents the current offset of the opened file in decimal |
| form [see lseek(2) for details], 'flags' denotes the octal O_xxx mask the |
| file has been created with [see open(2) for details] and 'mnt_id' represents |
| mount ID of the file system containing the opened file [see 3.5 |
| /proc/<pid>/mountinfo for details]. 'ino' represents the inode number of |
| the file. |
| |
| A typical output is:: |
| |
| pos: 0 |
| flags: 0100002 |
| mnt_id: 19 |
| ino: 63107 |
| |
| All locks associated with a file descriptor are shown in its fdinfo too:: |
| |
| lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF |
| |
| The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags |
| pair provide additional information particular to the objects they represent. |
| |
| Eventfd files |
| ~~~~~~~~~~~~~ |
| |
| :: |
| |
| pos: 0 |
| flags: 04002 |
| mnt_id: 9 |
| ino: 63107 |
| eventfd-count: 5a |
| |
| where 'eventfd-count' is hex value of a counter. |
| |
| Signalfd files |
| ~~~~~~~~~~~~~~ |
| |
| :: |
| |
| pos: 0 |
| flags: 04002 |
| mnt_id: 9 |
| ino: 63107 |
| sigmask: 0000000000000200 |
| |
| where 'sigmask' is hex value of the signal mask associated |
| with a file. |
| |
| Epoll files |
| ~~~~~~~~~~~ |
| |
| :: |
| |
| pos: 0 |
| flags: 02 |
| mnt_id: 9 |
| ino: 63107 |
| tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7 |
| |
| where 'tfd' is a target file descriptor number in decimal form, |
| 'events' is events mask being watched and the 'data' is data |
| associated with a target [see epoll(7) for more details]. |
| |
| The 'pos' is current offset of the target file in decimal form |
| [see lseek(2)], 'ino' and 'sdev' are inode and device numbers |
| where target file resides, all in hex format. |
| |
| Fsnotify files |
| ~~~~~~~~~~~~~~ |
| For inotify files the format is the following:: |
| |
| pos: 0 |
| flags: 02000000 |
| mnt_id: 9 |
| ino: 63107 |
| inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d |
| |
| where 'wd' is a watch descriptor in decimal form, i.e. a target file |
| descriptor number, 'ino' and 'sdev' are inode and device where the |
| target file resides and the 'mask' is the mask of events, all in hex |
| form [see inotify(7) for more details]. |
| |
| If the kernel was built with exportfs support, the path to the target |
| file is encoded as a file handle. The file handle is provided by three |
| fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex |
| format. |
| |
| If the kernel is built without exportfs support the file handle won't be |
| printed out. |
| |
| If there is no inotify mark attached yet the 'inotify' line will be omitted. |
| |
| For fanotify files the format is:: |
| |
| pos: 0 |
| flags: 02 |
| mnt_id: 9 |
| ino: 63107 |
| fanotify flags:10 event-flags:0 |
| fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003 |
| fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4 |
| |
| where fanotify 'flags' and 'event-flags' are values used in fanotify_init |
| call, 'mnt_id' is the mount point identifier, 'mflags' is the value of |
| flags associated with mark which are tracked separately from events |
| mask. 'ino' and 'sdev' are target inode and device, 'mask' is the events |
| mask and 'ignored_mask' is the mask of events which are to be ignored. |
| All are in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask' |
| provide information about flags and mask used in fanotify_mark |
| call [see fsnotify manpage for details]. |
| |
| While the first three lines are mandatory and always printed, the rest is |
| optional and may be omitted if no marks created yet. |
| |
| Timerfd files |
| ~~~~~~~~~~~~~ |
| |
| :: |
| |
| pos: 0 |
| flags: 02 |
| mnt_id: 9 |
| ino: 63107 |
| clockid: 0 |
| ticks: 0 |
| settime flags: 01 |
| it_value: (0, 49406829) |
| it_interval: (1, 0) |
| |
| where 'clockid' is the clock type and 'ticks' is the number of the timer expirations |
| that have occurred [see timerfd_create(2) for details]. 'settime flags' are |
| flags in octal form been used to setup the timer [see timerfd_settime(2) for |
| details]. 'it_value' is remaining time until the timer expiration. |
| 'it_interval' is the interval for the timer. Note the timer might be set up |
| with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value' |
| still exhibits timer's remaining time. |
| |
| DMA Buffer files |
| ~~~~~~~~~~~~~~~~ |
| |
| :: |
| |
| pos: 0 |
| flags: 04002 |
| mnt_id: 9 |
| ino: 63107 |
| size: 32768 |
| count: 2 |
| exp_name: system-heap |
| |
| where 'size' is the size of the DMA buffer in bytes. 'count' is the file count of |
| the DMA buffer file. 'exp_name' is the name of the DMA buffer exporter. |
| |
| 3.9 /proc/<pid>/map_files - Information about memory mapped files |
| --------------------------------------------------------------------- |
| This directory contains symbolic links which represent memory mapped files |
| the process is maintaining. Example output:: |
| |
| | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so |
| | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so |
| | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so |
| | ... |
| | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1 |
| | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls |
| |
| The name of a link represents the virtual memory bounds of a mapping, i.e. |
| vm_area_struct::vm_start-vm_area_struct::vm_end. |
| |
| The main purpose of the map_files is to retrieve a set of memory mapped |
| files in a fast way instead of parsing /proc/<pid>/maps or |
| /proc/<pid>/smaps, both of which contain many more records. At the same |
| time one can open(2) mappings from the listings of two processes and |
| comparing their inode numbers to figure out which anonymous memory areas |
| are actually shared. |
| |
| 3.10 /proc/<pid>/timerslack_ns - Task timerslack value |
| --------------------------------------------------------- |
| This file provides the value of the task's timerslack value in nanoseconds. |
| This value specifies an amount of time that normal timers may be deferred |
| in order to coalesce timers and avoid unnecessary wakeups. |
| |
| This allows a task's interactivity vs power consumption tradeoff to be |
| adjusted. |
| |
| Writing 0 to the file will set the task's timerslack to the default value. |
| |
| Valid values are from 0 - ULLONG_MAX |
| |
| An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level |
| permissions on the task specified to change its timerslack_ns value. |
| |
| 3.11 /proc/<pid>/patch_state - Livepatch patch operation state |
| ----------------------------------------------------------------- |
| When CONFIG_LIVEPATCH is enabled, this file displays the value of the |
| patch state for the task. |
| |
| A value of '-1' indicates that no patch is in transition. |
| |
| A value of '0' indicates that a patch is in transition and the task is |
| unpatched. If the patch is being enabled, then the task hasn't been |
| patched yet. If the patch is being disabled, then the task has already |
| been unpatched. |
| |
| A value of '1' indicates that a patch is in transition and the task is |
| patched. If the patch is being enabled, then the task has already been |
| patched. If the patch is being disabled, then the task hasn't been |
| unpatched yet. |
| |
| 3.12 /proc/<pid>/arch_status - task architecture specific status |
| ------------------------------------------------------------------- |
| When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the |
| architecture specific status of the task. |
| |
| Example |
| ~~~~~~~ |
| |
| :: |
| |
| $ cat /proc/6753/arch_status |
| AVX512_elapsed_ms: 8 |
| |
| Description |
| ~~~~~~~~~~~ |
| |
| x86 specific entries |
| ~~~~~~~~~~~~~~~~~~~~~ |
| |
| AVX512_elapsed_ms |
| ^^^^^^^^^^^^^^^^^^ |
| |
| If AVX512 is supported on the machine, this entry shows the milliseconds |
| elapsed since the last time AVX512 usage was recorded. The recording |
| happens on a best effort basis when a task is scheduled out. This means |
| that the value depends on two factors: |
| |
| 1) The time which the task spent on the CPU without being scheduled |
| out. With CPU isolation and a single runnable task this can take |
| several seconds. |
| |
| 2) The time since the task was scheduled out last. Depending on the |
| reason for being scheduled out (time slice exhausted, syscall ...) |
| this can be arbitrary long time. |
| |
| As a consequence the value cannot be considered precise and authoritative |
| information. The application which uses this information has to be aware |
| of the overall scenario on the system in order to determine whether a |
| task is a real AVX512 user or not. Precise information can be obtained |
| with performance counters. |
| |
| A special value of '-1' indicates that no AVX512 usage was recorded, thus |
| the task is unlikely an AVX512 user, but depends on the workload and the |
| scheduling scenario, it also could be a false negative mentioned above. |
| |
| 3.13 /proc/<pid>/fd - List of symlinks to open files |
| ------------------------------------------------------- |
| This directory contains symbolic links which represent open files |
| the process is maintaining. Example output:: |
| |
| lr-x------ 1 root root 64 Sep 20 17:53 0 -> /dev/null |
| l-wx------ 1 root root 64 Sep 20 17:53 1 -> /dev/null |
| lrwx------ 1 root root 64 Sep 20 17:53 10 -> 'socket:[12539]' |
| lrwx------ 1 root root 64 Sep 20 17:53 11 -> 'socket:[12540]' |
| lrwx------ 1 root root 64 Sep 20 17:53 12 -> 'socket:[12542]' |
| |
| The number of open files for the process is stored in 'size' member |
| of stat() output for /proc/<pid>/fd for fast access. |
| ------------------------------------------------------- |
| |
| |
| Chapter 4: Configuring procfs |
| ============================= |
| |
| 4.1 Mount options |
| --------------------- |
| |
| The following mount options are supported: |
| |
| ========= ======================================================== |
| hidepid= Set /proc/<pid>/ access mode. |
| gid= Set the group authorized to learn processes information. |
| subset= Show only the specified subset of procfs. |
| ========= ======================================================== |
| |
| hidepid=off or hidepid=0 means classic mode - everybody may access all |
| /proc/<pid>/ directories (default). |
| |
| hidepid=noaccess or hidepid=1 means users may not access any /proc/<pid>/ |
| directories but their own. Sensitive files like cmdline, sched*, status are now |
| protected against other users. This makes it impossible to learn whether any |
| user runs specific program (given the program doesn't reveal itself by its |
| behaviour). As an additional bonus, as /proc/<pid>/cmdline is unaccessible for |
| other users, poorly written programs passing sensitive information via program |
| arguments are now protected against local eavesdroppers. |
| |
| hidepid=invisible or hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be |
| fully invisible to other users. It doesn't mean that it hides a fact whether a |
| process with a specific pid value exists (it can be learned by other means, e.g. |
| by "kill -0 $PID"), but it hides process' uid and gid, which may be learned by |
| stat()'ing /proc/<pid>/ otherwise. It greatly complicates an intruder's task of |
| gathering information about running processes, whether some daemon runs with |
| elevated privileges, whether other user runs some sensitive program, whether |
| other users run any program at all, etc. |
| |
| hidepid=ptraceable or hidepid=4 means that procfs should only contain |
| /proc/<pid>/ directories that the caller can ptrace. |
| |
| gid= defines a group authorized to learn processes information otherwise |
| prohibited by hidepid=. If you use some daemon like identd which needs to learn |
| information about processes information, just add identd to this group. |
| |
| subset=pid hides all top level files and directories in the procfs that |
| are not related to tasks. |
| |
| Chapter 5: Filesystem behavior |
| ============================== |
| |
| Originally, before the advent of pid namepsace, procfs was a global file |
| system. It means that there was only one procfs instance in the system. |
| |
| When pid namespace was added, a separate procfs instance was mounted in |
| each pid namespace. So, procfs mount options are global among all |
| mountpoints within the same namespace:: |
| |
| # grep ^proc /proc/mounts |
| proc /proc proc rw,relatime,hidepid=2 0 0 |
| |
| # strace -e mount mount -o hidepid=1 -t proc proc /tmp/proc |
| mount("proc", "/tmp/proc", "proc", 0, "hidepid=1") = 0 |
| +++ exited with 0 +++ |
| |
| # grep ^proc /proc/mounts |
| proc /proc proc rw,relatime,hidepid=2 0 0 |
| proc /tmp/proc proc rw,relatime,hidepid=2 0 0 |
| |
| and only after remounting procfs mount options will change at all |
| mountpoints:: |
| |
| # mount -o remount,hidepid=1 -t proc proc /tmp/proc |
| |
| # grep ^proc /proc/mounts |
| proc /proc proc rw,relatime,hidepid=1 0 0 |
| proc /tmp/proc proc rw,relatime,hidepid=1 0 0 |
| |
| This behavior is different from the behavior of other filesystems. |
| |
| The new procfs behavior is more like other filesystems. Each procfs mount |
| creates a new procfs instance. Mount options affect own procfs instance. |
| It means that it became possible to have several procfs instances |
| displaying tasks with different filtering options in one pid namespace:: |
| |
| # mount -o hidepid=invisible -t proc proc /proc |
| # mount -o hidepid=noaccess -t proc proc /tmp/proc |
| # grep ^proc /proc/mounts |
| proc /proc proc rw,relatime,hidepid=invisible 0 0 |
| proc /tmp/proc proc rw,relatime,hidepid=noaccess 0 0 |
