admin-guide/sysctl/vm.rst

13 ------------------------------------------------------------------------------
27 - admin_reserve_kbytes
28 - block_dump
29 - compact_memory
30 - compaction_proactiveness
31 - compact_unevictable_allowed
32 - dirty_background_bytes
33 - dirty_background_ratio
34 - dirty_bytes
35 - dirty_expire_centisecs
36 - dirty_ratio
37 - dirtytime_expire_seconds
38 - dirty_writeback_centisecs
39 - drop_caches
40 - extfrag_threshold
41 - extra_free_kbytes
42 - highmem_is_dirtyable
43 - hugetlb_shm_group
44 - laptop_mode
45 - legacy_va_layout
46 - lowmem_reserve_ratio
47 - max_map_count
48 - memory_failure_early_kill
49 - memory_failure_recovery
50 - min_free_kbytes
51 - min_slab_ratio
52 - min_unmapped_ratio
53 - mmap_min_addr
54 - mmap_rnd_bits
55 - mmap_rnd_compat_bits
56 - nr_hugepages
57 - nr_hugepages_mempolicy
58 - nr_overcommit_hugepages
59 - nr_trim_pages         (only if CONFIG_MMU=n)
60 - numa_zonelist_order
61 - oom_dump_tasks
62 - oom_kill_allocating_task
63 - overcommit_kbytes
64 - overcommit_memory
65 - overcommit_ratio
66 - page-cluster
67 - panic_on_oom
68 - percpu_pagelist_fraction
69 - stat_interval
70 - stat_refresh
71 - numa_stat
72 - swappiness
73 - unprivileged_userfaultfd
74 - user_reserve_kbytes
75 - vfs_cache_pressure
76 - watermark_boost_factor
77 - watermark_scale_factor
78 - zone_reclaim_mode
114 information on block I/O debugging is in Documentation/admin-guide/laptops/laptop-mode.rst.
133 Note that compaction has a non-trivial system-wide impact as pages
199 of a second.  Data which has been dirty in-memory for longer than this
254 This is a non-destructive operation and will not free any dirty objects.
260 This file is not a means to control the growth of the various kernel caches
282 reclaim to satisfy a high-order allocation. The extfrag/extfrag_index file in
285 of memory, values towards 1000 imply failures are due to fragmentation and -1
306 storage more effectively. Note this also comes with a risk of pre-mature
321 (causing in-kernel memory allocations) with a maximum total message burst
338 controlled by this knob are discussed in Documentation/admin-guide/laptops/laptop-mode.rst.
344 If non-zero, this sysctl disables the new 32-bit mmap layout - the kernel
364 (The same argument applies to the old 16 megabyte ISA DMA region.  This
371 If you have a machine which uses highmem or ISA DMA and your
380 But, these values are not used directly. The kernel calculates # of protection
381 pages for each zones from them. These are shown as array of protection pages
382 in /proc/zoneinfo like followings. (This is an example of x86-64 box).
383 Each zone has an array of protection pages like this::
385   Node 0, zone      DMA
393           protection: (0, 2004, 2004, 2004)
402 In this example, if normal pages (index=2) are required to this DMA zone and
404 not be used because pages_free(1355) is smaller than watermark + protection[2]
405 (4 + 2004 = 2008). If this protection value is 0, this zone would be used for
406 normal page requirement. If requirement is DMA zone(index=0), protection[0]
409 zone[i]'s protection[j] is calculated by following expression::
412     zone[i]->protection[j]
423     256 (if zone[i] means DMA or DMA32 zone)
428 256 means 1/256. # of protection pages becomes about "0.39%" of total managed
432 The minimum value is 1 (1/1 -> 100%). The value less than 1 completely
433 disables protection of the pages.
440 may have. Memory map areas are used as a side-effect of calling
454 Control how to kill processes when uncorrected memory error (typically
513 This insures that the slab growth stays under control even in NUMA
533 against all file-backed unmapped pages including swapcache pages and tmpfs
585 See Documentation/admin-guide/mm/hugetlbpage.rst
591 Change the size of the hugepage pool at run-time on a specific
594 See Documentation/admin-guide/mm/hugetlbpage.rst
603 See Documentation/admin-guide/mm/hugetlbpage.rst
611 This value adjusts the excess page trimming behaviour of power-of-2 aligned
620 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
634 In non-NUMA case, a zonelist for GFP_KERNEL is ordered as following.
635 ZONE_NORMAL -> ZONE_DMA
642   (A) Node(0) ZONE_NORMAL -> Node(0) ZONE_DMA -> Node(1) ZONE_NORMAL
643   (B) Node(0) ZONE_NORMAL -> Node(1) ZONE_NORMAL -> Node(0) ZONE_DMA.
647 out-of-memory(OOM) of ZONE_DMA because ZONE_DMA is tend to be small.
650 the DMA zone.
662 On 32-bit, the Normal zone needs to be preserved for allocations accessible
665 On 64-bit, devices that require DMA32/DMA are relatively rare, so "node"
675 Enables a system-wide task dump (excluding kernel threads) to be produced
676 when the kernel performs an OOM-killing and includes such information as
688 If this is set to non-zero, this information is shown whenever the
689 OOM killer actually kills a memory-hogging task.
697 This enables or disables killing the OOM-triggering task in
698 out-of-memory situations.
702 selects a rogue memory-hogging task that frees up a large amount of
705 If this is set to non-zero, the OOM killer simply kills the task that
706 triggered the out-of-memory condition.  This avoids the expensive
742 programs that malloc() huge amounts of memory "just-in-case"
747 See Documentation/vm/overcommit-accounting.rst and
759 page-cluster
762 page-cluster controls the number of pages up to which consecutive pages
766 but consecutive on swap space - that means they were swapped out together.
768 It is a logarithmic value - setting it to zero means "1 page", setting
774 swap-intensive.
784 This enables or disables panic on out-of-memory feature.
790 If this is set to 1, the kernel panics when out-of-memory happens.
793 may be killed by oom-killer. No panic occurs in this case.
798 above-mentioned. Even oom happens under memory cgroup, the whole
813 This is the fraction of pages at most (high mark pcp->high) in each zone that
821 set to pcp->high/4.  The upper limit of batch is (PAGE_SHIFT * 8)
838 Any read or write (by root only) flushes all the per-cpu vm statistics
842 As a side-effect, it also checks for negative totals (elsewhere reported
868 This control is used to define the rough relative IO cost of swapping
871 cache and swap-backed pages equally; lower values signify more
876 experimentation and will also be workload-dependent.
880 For in-memory swap, like zram or zswap, as well as hybrid setups that
887 file-backed pages is less than the high watermark in a zone.
935 lead to out-of-memory conditions. Increasing vfs_cache_pressure beyond 100
951 increase the success rate of future high-order allocations such as SLUB
961 (e.g.  2MB on 64-bit x86). A boost factor of 0 will disable the feature.