X-Git-Url: http://pilppa.org/gitweb/?a=blobdiff_plain;f=Documentation%2Fsysctl%2Fvm.txt;h=8cfca173d4bca46fab5c121be80d070858aaa0c6;hb=4aabab2181f20560948c2045ce1faaa9ac1507a8;hp=7cee90223d3a0624296b42d983d786b25462dc56;hpb=f7d57e42e7ebd085133506ef6325e70e822196dc;p=linux-2.6-omap-h63xx.git diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index 7cee90223d3..8cfca173d4b 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt @@ -29,7 +29,9 @@ Currently, these files are in /proc/sys/vm: - drop-caches - zone_reclaim_mode - min_unmapped_ratio +- min_slab_ratio - panic_on_oom +- mmap_min_address ============================================================== @@ -128,7 +130,7 @@ the high water marks for each per cpu page list. zone_reclaim_mode: -Zone_reclaim_mode allows to set more or less agressive approaches to +Zone_reclaim_mode allows someone to set more or less aggressive approaches to reclaim memory when a zone runs out of memory. If it is set to zero then no zone reclaim occurs. Allocations will be satisfied from other zones / nodes in the system. @@ -138,7 +140,6 @@ 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 @@ -162,18 +163,13 @@ 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 file backed pages in each zone. Zone reclaim will only +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. @@ -182,13 +178,56 @@ The default is 1 percent. ============================================================= +min_slab_ratio: + +This is available only on NUMA kernels. + +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. + +The default is 5 percent. + +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. + +============================================================= + panic_on_oom -This enables or disables panic on out-of-memory feature. If this is set to 1, -the kernel panics when out-of-memory happens. If this is set to 0, the kernel -will kill some rogue process, called oom_killer. Usually, oom_killer can kill -rogue processes and system will survive. If you want to panic the system -rather than killing rogue processes, set this to 1. +This enables or disables panic on out-of-memory feature. + +If this is set to 0, the kernel will kill some rogue process, +called oom_killer. Usually, oom_killer can kill rogue processes and +system will survive. + +If this is set to 1, the kernel panics when out-of-memory happens. +However, if a process limits using nodes by mempolicy/cpusets, +and those nodes become memory exhaustion status, one process +may be killed by oom-killer. No panic occurs in this case. +Because other nodes' memory may be free. This means system total status +may be not fatal yet. + +If this is set to 2, the kernel panics compulsorily even on the +above-mentioned. The default value is 0. +1 and 2 are for failover of clustering. Please select either +according to your policy of failover. + +============================================================== + +mmap_min_addr + +This file indicates the amount of address space which a user process will +be restricted from mmaping. Since kernel null dereference bugs could +accidentally operate based on the information in the first couple of pages +of memory userspace processes should not be allowed to write to them. By +default this value is set to 0 and no protections will be enforced by the +security module. Setting this value to something like 64k will allow the +vast majority of applications to work correctly and provide defense in depth +against future potential kernel bugs.