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.
264 Use of this file can cause performance problems.  Since it discards cached
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
382 in /proc/zoneinfo like followings. (This is an example of x86-64 box).
412     zone[i]->protection[j]
432 The minimum value is 1 (1/1 -> 100%). The value less than 1 completely
440 may have. Memory map areas are used as a side-effect of calling
458 transparently without affecting any applications. But if there is
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.
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
685 be forced to incur a performance penalty in OOM conditions when the
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
853 When page allocation performance becomes a bottleneck and you can tolerate
859 When page allocation performance is not a bottleneck and you want all
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
939 performance impact. Reclaim code needs to take various locks to find freeable
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.
1005 and that accessing remote memory would cause a measurable performance
1012 throttle the process. This may decrease the performance of a single process
1014 anymore but it preserve the memory on other nodes so that the performance