admin-guide/sysctl/vm.rst

13 ------------------------------------------------------------------------------
27 - admin_reserve_kbytes
28 - compact_memory
29 - compaction_proactiveness
30 - compact_unevictable_allowed
31 - dirty_background_bytes
32 - dirty_background_ratio
33 - dirty_bytes
34 - dirty_expire_centisecs
35 - dirty_ratio
36 - dirtytime_expire_seconds
37 - dirty_writeback_centisecs
38 - drop_caches
39 - enable_soft_offline
40 - extfrag_threshold
41 - highmem_is_dirtyable
42 - hugetlb_shm_group
43 - laptop_mode
44 - legacy_va_layout
45 - lowmem_reserve_ratio
46 - max_map_count
47 - mem_profiling         (only if CONFIG_MEM_ALLOC_PROFILING=y)
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 - page_lock_unfairness
68 - panic_on_oom
69 - percpu_pagelist_high_fraction
70 - stat_interval
71 - stat_refresh
72 - numa_stat
73 - swappiness
74 - unprivileged_userfaultfd
75 - user_reserve_kbytes
76 - vfs_cache_pressure
77 - watermark_boost_factor
78 - watermark_scale_factor
79 - zone_reclaim_mode
127 Note that compaction has a non-trivial system-wide impact as pages
193 of a second.  Data which has been dirty in-memory for longer than this
248 This is a non-destructive operation and will not free any dirty objects.
273 Correctable memory errors are very common on servers. Soft-offline is kernel's
276 For different types of page, soft-offline has different behaviors / costs.
278 - For a raw error page, soft-offline migrates the in-use page's content to
281 - For a page that is part of a transparent hugepage, soft-offline splits the
286 - For a page that is part of a HugeTLB hugepage, soft-offline first migrates
303 - Request to soft offline pages from RAS Correctable Errors Collector.
305 - On ARM, the request to soft offline pages from GHES driver.
307 - On PARISC, the request to soft offline pages from Page Deallocation Table.
313 reclaim to satisfy a high-order allocation. The extfrag/extfrag_index file in
316 of memory, values towards 1000 imply failures are due to fragmentation and -1
337 storage more effectively. Note this also comes with a risk of pre-mature
354 controlled by this knob are discussed in Documentation/admin-guide/laptops/laptop-mode.rst.
360 If non-zero, this sysctl disables the new 32-bit mmap layout - the kernel
398 in /proc/zoneinfo like the following. (This is an example of x86-64 box).
428     zone[i]->protection[j]
448 The minimum value is 1 (1/1 -> 100%). The value less than 1 completely
456 may have. Memory map areas are used as a side-effect of calling
490 no other up-to-date copy of the data it will kill to prevent any data
550 The process of reclaiming slab memory is currently not node specific
564 against all file-backed unmapped pages including swapcache pages and tmpfs
616 See Documentation/admin-guide/mm/hugetlbpage.rst
659 Change the size of the hugepage pool at run-time on a specific
662 See Documentation/admin-guide/mm/hugetlbpage.rst
671 See Documentation/admin-guide/mm/hugetlbpage.rst
679 This value adjusts the excess page trimming behaviour of power-of-2 aligned
688 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
702 In non-NUMA case, a zonelist for GFP_KERNEL is ordered as following.
703 ZONE_NORMAL -> ZONE_DMA
710   (A) Node(0) ZONE_NORMAL -> Node(0) ZONE_DMA -> Node(1) ZONE_NORMAL
711   (B) Node(0) ZONE_NORMAL -> Node(1) ZONE_NORMAL -> Node(0) ZONE_DMA.
713 Type(A) offers the best locality for processes on Node(0), but ZONE_DMA
715 out-of-memory(OOM) of ZONE_DMA because ZONE_DMA is tend to be small.
717 Type(B) cannot offer the best locality but is more robust against OOM of
730 On 32-bit, the Normal zone needs to be preserved for allocations accessible
733 On 64-bit, devices that require DMA32/DMA are relatively rare, so "node"
743 Enables a system-wide task dump (excluding kernel threads) to be produced
744 when the kernel performs an OOM-killing and includes such information as
756 If this is set to non-zero, this information is shown whenever the
757 OOM killer actually kills a memory-hogging task.
765 This enables or disables killing the OOM-triggering task in
766 out-of-memory situations.
770 selects a rogue memory-hogging task that frees up a large amount of
773 If this is set to non-zero, the OOM killer simply kills the task that
774 triggered the out-of-memory condition.  This avoids the expensive
810 programs that malloc() huge amounts of memory "just-in-case"
815 See Documentation/mm/overcommit-accounting.rst and
827 page-cluster
830 page-cluster controls the number of pages up to which consecutive pages
834 but consecutive on swap space - that means they were swapped out together.
836 It is a logarithmic value - setting it to zero means "1 page", setting
842 swap-intensive.
860 This enables or disables panic on out-of-memory feature.
866 If this is set to 1, the kernel panics when out-of-memory happens.
869 may be killed by oom-killer. No panic occurs in this case.
874 above-mentioned. Even oom happens under memory cgroup, the whole
890 per-cpu page lists. It is an upper boundary that is divided depending
893 on per-cpu page lists. This entry only changes the value of hot per-cpu
895 each zone between per-cpu lists.
897 The batch value of each per-cpu page list remains the same regardless of
900 The initial value is zero. Kernel uses this value to set the high pcp->high
916 Any read or write (by root only) flushes all the per-cpu vm statistics
920 As a side-effect, it also checks for negative totals (elsewhere reported
949 cache and swap-backed pages equally; lower values signify more
954 experimentation and will also be workload-dependent.
958 For in-memory swap, like zram or zswap, as well as hybrid setups that
965 file-backed pages is less than the high watermark in a zone.
985 Documentation/admin-guide/mm/userfaultfd.rst.
1016 lead to out-of-memory conditions. Increasing vfs_cache_pressure beyond 100
1032 increase the success rate of future high-order allocations such as SLUB
1041 worth of pages will be reclaimed (e.g.  2MB on 64-bit x86). A boost factor
1082 data locality.