diff options
Diffstat (limited to 'Documentation/sysctl/vm.txt')
| -rw-r--r-- | Documentation/sysctl/vm.txt | 40 |
1 files changed, 27 insertions, 13 deletions
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index 2dc246af488..20d0d797f53 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt @@ -28,7 +28,8 @@ Currently, these files are in /proc/sys/vm: - block_dump - drop-caches - zone_reclaim_mode -- zone_reclaim_interval +- min_unmapped_ratio +- min_slab_ratio - panic_on_oom ============================================================== @@ -138,7 +139,6 @@ This is value ORed together of 1 = Zone reclaim on 2 = Zone reclaim writes dirty pages out 4 = Zone reclaim swaps pages -8 = Also do a global slab reclaim pass zone_reclaim_mode is set during bootup to 1 if it is determined that pages from remote zones will cause a measurable performance reduction. The @@ -162,22 +162,36 @@ Allowing regular swap effectively restricts allocations to the local node unless explicitly overridden by memory policies or cpuset configurations. -It may be advisable to allow slab reclaim if the system makes heavy -use of files and builds up large slab caches. However, the slab -shrink operation is global, may take a long time and free slabs -in all nodes of the system. +============================================================= + +min_unmapped_ratio: + +This is available only on NUMA kernels. + +A percentage of the total pages in each zone. Zone reclaim will only +occur if more than this percentage of pages are file backed and unmapped. +This is to insure that a minimal amount of local pages is still available for +file I/O even if the node is overallocated. + +The default is 1 percent. + +============================================================= -================================================================ +min_slab_ratio: -zone_reclaim_interval: +This is available only on NUMA kernels. -The time allowed for off node allocations after zone reclaim -has failed to reclaim enough pages to allow a local allocation. +A percentage of the total pages in each zone. On Zone reclaim +(fallback from the local zone occurs) slabs will be reclaimed if more +than this percentage of pages in a zone are reclaimable slab pages. +This insures that the slab growth stays under control even in NUMA +systems that rarely perform global reclaim. -Time is set in seconds and set by default to 30 seconds. +The default is 5 percent. -Reduce the interval if undesired off node allocations occur. However, too -frequent scans will have a negative impact onoff node allocation performance. +Note that slab reclaim is triggered in a per zone / node fashion. +The process of reclaiming slab memory is currently not node specific +and may not be fast. ============================================================= |