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diff --git a/man5/proc_sys_vm.5 b/man5/proc_sys_vm.5 deleted file mode 100644 index 17a7dd2ec..000000000 --- a/man5/proc_sys_vm.5 +++ /dev/null @@ -1,420 +0,0 @@ -.\" Copyright (C) 1994, 1995, Daniel Quinlan <quinlan@yggdrasil.com> -.\" Copyright (C) 2002-2008, 2017, Michael Kerrisk <mtk.manpages@gmail.com> -.\" Copyright (C) , Andries Brouwer <aeb@cwi.nl> -.\" Copyright (C) 2023, Alejandro Colomar <alx@kernel.org> -.\" -.\" SPDX-License-Identifier: GPL-3.0-or-later -.\" -.TH proc_sys_vm 5 (date) "Linux man-pages (unreleased)" -.SH NAME -/proc/sys/vm/ \- virtual memory subsystem -.SH DESCRIPTION -.TP -.I /proc/sys/vm/ -This directory contains files for memory management tuning, buffer, and -cache management. -.TP -.IR /proc/sys/vm/admin_reserve_kbytes " (since Linux 3.10)" -.\" commit 4eeab4f5580d11bffedc697684b91b0bca0d5009 -This file defines the amount of free memory (in KiB) on the system that -should be reserved for users with the capability -.BR CAP_SYS_ADMIN . -.IP -The default value in this file is the minimum of [3% of free pages, 8MiB] -expressed as KiB. -The default is intended to provide enough for the superuser -to log in and kill a process, if necessary, -under the default overcommit 'guess' mode (i.e., 0 in -.IR /proc/sys/vm/overcommit_memory ). -.IP -Systems running in "overcommit never" mode (i.e., 2 in -.IR /proc/sys/vm/overcommit_memory ) -should increase the value in this file to account -for the full virtual memory size of the programs used to recover (e.g., -.BR login (1) -.BR ssh (1), -and -.BR top (1)) -Otherwise, the superuser may not be able to log in to recover the system. -For example, on x86-64 a suitable value is 131072 (128MiB reserved). -.IP -Changing the value in this file takes effect whenever -an application requests memory. -.TP -.IR /proc/sys/vm/compact_memory " (since Linux 2.6.35)" -When 1 is written to this file, all zones are compacted such that free -memory is available in contiguous blocks where possible. -The effect of this action can be seen by examining -.IR /proc/buddyinfo . -.IP -Present only if the kernel was configured with -.BR CONFIG_COMPACTION . -.TP -.IR /proc/sys/vm/drop_caches " (since Linux 2.6.16)" -Writing to this file causes the kernel to drop clean caches, dentries, and -inodes from memory, causing that memory to become free. -This can be useful for memory management testing and -performing reproducible filesystem benchmarks. -Because writing to this file causes the benefits of caching to be lost, -it can degrade overall system performance. -.IP -To free pagecache, use: -.IP -.in +4n -.EX -echo 1 > /proc/sys/vm/drop_caches -.EE -.in -.IP -To free dentries and inodes, use: -.IP -.in +4n -.EX -echo 2 > /proc/sys/vm/drop_caches -.EE -.in -.IP -To free pagecache, dentries, and inodes, use: -.IP -.in +4n -.EX -echo 3 > /proc/sys/vm/drop_caches -.EE -.in -.IP -Because writing to this file is a nondestructive operation and dirty objects -are not freeable, the -user should run -.BR sync (1) -first. -.TP -.IR /proc/sys/vm/sysctl_hugetlb_shm_group " (since Linux 2.6.7)" -This writable file contains a group ID that is allowed -to allocate memory using huge pages. -If a process has a filesystem group ID or any supplementary group ID that -matches this group ID, -then it can make huge-page allocations without holding the -.B CAP_IPC_LOCK -capability; see -.BR memfd_create (2), -.BR mmap (2), -and -.BR shmget (2). -.TP -.IR /proc/sys/vm/legacy_va_layout " (since Linux 2.6.9)" -.\" The following is from Documentation/filesystems/proc.txt -If nonzero, this disables the new 32-bit memory-mapping layout; -the kernel will use the legacy (2.4) layout for all processes. -.TP -.IR /proc/sys/vm/memory_failure_early_kill " (since Linux 2.6.32)" -.\" The following is based on the text in Documentation/sysctl/vm.txt -Control how to kill processes when an uncorrected memory error -(typically a 2-bit error in a memory module) -that cannot be handled by the kernel -is detected in the background by hardware. -In some cases (like the page still having a valid copy on disk), -the kernel will handle the failure -transparently without affecting any applications. -But if there is no other up-to-date copy of the data, -it will kill processes to prevent any data corruptions from propagating. -.IP -The file has one of the following values: -.RS -.TP -.B 1 -Kill all processes that have the corrupted-and-not-reloadable page mapped -as soon as the corruption is detected. -Note that this is not supported for a few types of pages, -such as kernel internally -allocated data or the swap cache, but works for the majority of user pages. -.TP -.B 0 -Unmap the corrupted page from all processes and kill a process -only if it tries to access the page. -.RE -.IP -The kill is performed using a -.B SIGBUS -signal with -.I si_code -set to -.BR BUS_MCEERR_AO . -Processes can handle this if they want to; see -.BR sigaction (2) -for more details. -.IP -This feature is active only on architectures/platforms with advanced machine -check handling and depends on the hardware capabilities. -.IP -Applications can override the -.I memory_failure_early_kill -setting individually with the -.BR prctl (2) -.B PR_MCE_KILL -operation. -.IP -Present only if the kernel was configured with -.BR CONFIG_MEMORY_FAILURE . -.TP -.IR /proc/sys/vm/memory_failure_recovery " (since Linux 2.6.32)" -.\" The following is based on the text in Documentation/sysctl/vm.txt -Enable memory failure recovery (when supported by the platform). -.RS -.TP -.B 1 -Attempt recovery. -.TP -.B 0 -Always panic on a memory failure. -.RE -.IP -Present only if the kernel was configured with -.BR CONFIG_MEMORY_FAILURE . -.TP -.IR /proc/sys/vm/oom_dump_tasks " (since Linux 2.6.25)" -.\" The following is from Documentation/sysctl/vm.txt -Enables a system-wide task dump (excluding kernel threads) to be -produced when the kernel performs an OOM-killing. -The dump includes the following information -for each task (thread, process): -thread ID, real user ID, thread group ID (process ID), -virtual memory size, resident set size, -the CPU that the task is scheduled on, -oom_adj score (see the description of -.IR /proc/ pid /oom_adj ), -and command name. -This is helpful to determine why the OOM-killer was invoked -and to identify the rogue task that caused it. -.IP -If this contains the value zero, this information is suppressed. -On very large systems with thousands of tasks, -it may not be feasible to dump the memory state information for each one. -Such systems should not be forced to incur a performance penalty in -OOM situations when the information may not be desired. -.IP -If this is set to nonzero, this information is shown whenever the -OOM-killer actually kills a memory-hogging task. -.IP -The default value is 0. -.TP -.IR /proc/sys/vm/oom_kill_allocating_task " (since Linux 2.6.24)" -.\" The following is from Documentation/sysctl/vm.txt -This enables or disables killing the OOM-triggering task in -out-of-memory situations. -.IP -If this is set to zero, the OOM-killer will scan through the entire -tasklist and select a task based on heuristics to kill. -This normally selects a rogue memory-hogging task that -frees up a large amount of memory when killed. -.IP -If this is set to nonzero, the OOM-killer simply kills the task that -triggered the out-of-memory condition. -This avoids a possibly expensive tasklist scan. -.IP -If -.I /proc/sys/vm/panic_on_oom -is nonzero, it takes precedence over whatever value is used in -.IR /proc/sys/vm/oom_kill_allocating_task . -.IP -The default value is 0. -.TP -.IR /proc/sys/vm/overcommit_kbytes " (since Linux 3.14)" -.\" commit 49f0ce5f92321cdcf741e35f385669a421013cb7 -This writable file provides an alternative to -.I /proc/sys/vm/overcommit_ratio -for controlling the -.I CommitLimit -when -.I /proc/sys/vm/overcommit_memory -has the value 2. -It allows the amount of memory overcommitting to be specified as -an absolute value (in kB), -rather than as a percentage, as is done with -.IR overcommit_ratio . -This allows for finer-grained control of -.I CommitLimit -on systems with extremely large memory sizes. -.IP -Only one of -.I overcommit_kbytes -or -.I overcommit_ratio -can have an effect: -if -.I overcommit_kbytes -has a nonzero value, then it is used to calculate -.IR CommitLimit , -otherwise -.I overcommit_ratio -is used. -Writing a value to either of these files causes the -value in the other file to be set to zero. -.TP -.I /proc/sys/vm/overcommit_memory -This file contains the kernel virtual memory accounting mode. -Values are: -.RS -.IP -0: heuristic overcommit (this is the default) -.br -1: always overcommit, never check -.br -2: always check, never overcommit -.RE -.IP -In mode 0, calls of -.BR mmap (2) -with -.B MAP_NORESERVE -are not checked, and the default check is very weak, -leading to the risk of getting a process "OOM-killed". -.IP -In mode 1, the kernel pretends there is always enough memory, -until memory actually runs out. -One use case for this mode is scientific computing applications -that employ large sparse arrays. -Before Linux 2.6.0, any nonzero value implies mode 1. -.IP -In mode 2 (available since Linux 2.6), the total virtual address space -that can be allocated -.RI ( CommitLimit -in -.IR /proc/meminfo ) -is calculated as -.IP -.in +4n -.EX -CommitLimit = (total_RAM \- total_huge_TLB) * - overcommit_ratio / 100 + total_swap -.EE -.in -.IP -where: -.RS -.IP \[bu] 3 -.I total_RAM -is the total amount of RAM on the system; -.IP \[bu] -.I total_huge_TLB -is the amount of memory set aside for huge pages; -.IP \[bu] -.I overcommit_ratio -is the value in -.IR /proc/sys/vm/overcommit_ratio ; -and -.IP \[bu] -.I total_swap -is the amount of swap space. -.RE -.IP -For example, on a system with 16 GB of physical RAM, 16 GB -of swap, no space dedicated to huge pages, and an -.I overcommit_ratio -of 50, this formula yields a -.I CommitLimit -of 24 GB. -.IP -Since Linux 3.14, if the value in -.I /proc/sys/vm/overcommit_kbytes -is nonzero, then -.I CommitLimit -is instead calculated as: -.IP -.in +4n -.EX -CommitLimit = overcommit_kbytes + total_swap -.EE -.in -.IP -See also the description of -.I /proc/sys/vm/admin_reserve_kbytes -and -.IR /proc/sys/vm/user_reserve_kbytes . -.TP -.IR /proc/sys/vm/overcommit_ratio " (since Linux 2.6.0)" -This writable file defines a percentage by which memory -can be overcommitted. -The default value in the file is 50. -See the description of -.IR /proc/sys/vm/overcommit_memory . -.TP -.IR /proc/sys/vm/panic_on_oom " (since Linux 2.6.18)" -.\" The following is adapted from Documentation/sysctl/vm.txt -This enables or disables a kernel panic in -an out-of-memory situation. -.IP -If this file is set to the value 0, -the kernel's OOM-killer will kill some rogue process. -Usually, the OOM-killer is able to kill a rogue process and the -system will survive. -.IP -If this file is set to the value 1, -then the kernel normally panics when out-of-memory happens. -However, if a process limits allocations to certain nodes -using memory policies -.RB ( mbind (2) -.BR MPOL_BIND ) -or cpusets -.RB ( cpuset (7)) -and those nodes reach memory exhaustion status, -one process may be killed by the OOM-killer. -No panic occurs in this case: -because other nodes' memory may be free, -this means the system as a whole may not have reached -an out-of-memory situation yet. -.IP -If this file is set to the value 2, -the kernel always panics when an out-of-memory condition occurs. -.IP -The default value is 0. -1 and 2 are for failover of clustering. -Select either according to your policy of failover. -.TP -.I /proc/sys/vm/swappiness -.\" The following is from Documentation/sysctl/vm.txt -The value in this file controls how aggressively the kernel will swap -memory pages. -Higher values increase aggressiveness, lower values -decrease aggressiveness. -The default value is 60. -.TP -.IR /proc/sys/vm/user_reserve_kbytes " (since Linux 3.10)" -.\" commit c9b1d0981fcce3d9976d7b7a56e4e0503bc610dd -Specifies an amount of memory (in KiB) to reserve for user processes. -This is intended to prevent a user from starting a single memory hogging -process, such that they cannot recover (kill the hog). -The value in this file has an effect only when -.I /proc/sys/vm/overcommit_memory -is set to 2 ("overcommit never" mode). -In this case, the system reserves an amount of memory that is the minimum -of [3% of current process size, -.IR user_reserve_kbytes ]. -.IP -The default value in this file is the minimum of [3% of free pages, 128MiB] -expressed as KiB. -.IP -If the value in this file is set to zero, -then a user will be allowed to allocate all free memory with a single process -(minus the amount reserved by -.IR /proc/sys/vm/admin_reserve_kbytes ). -Any subsequent attempts to execute a command will result in -"fork: Cannot allocate memory". -.IP -Changing the value in this file takes effect whenever -an application requests memory. -.TP -.IR /proc/sys/vm/unprivileged_userfaultfd " (since Linux 5.2)" -.\" cefdca0a86be517bc390fc4541e3674b8e7803b0 -This (writable) file exposes a flag that controls whether -unprivileged processes are allowed to employ -.BR userfaultfd (2). -If this file has the value 1, then unprivileged processes may use -.BR userfaultfd (2). -If this file has the value 0, then only processes that have the -.B CAP_SYS_PTRACE -capability may employ -.BR userfaultfd (2). -The default value in this file is 1. -.SH SEE ALSO -.BR proc (5), -.BR proc_sys (5) |