- block_dump
- drop-caches
- zone_reclaim_mode
+- min_unmapped_ratio
+- min_slab_ratio
+- panic_on_oom
==============================================================
zone_reclaim_mode:
-This is set during bootup to 1 if it is determined that pages from
-remote zones will cause a significant performance reduction. The
+Zone_reclaim_mode allows to set more or less agressive 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.
+
+This is value ORed together of
+
+1 = Zone reclaim on
+2 = Zone reclaim writes dirty pages out
+4 = Zone reclaim swaps pages
+
+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
page allocator will then reclaim easily reusable pages (those page
-cache pages that are currently not used) before going off node.
+cache pages that are currently not used) before allocating off node pages.
+
+It may be beneficial to switch off zone reclaim if the system is
+used for a file server and all of memory should be used for caching files
+from disk. In that case the caching effect is more important than
+data locality.
+
+Allowing zone reclaim to write out pages stops processes that are
+writing large amounts of data from dirtying pages on other nodes. Zone
+reclaim will write out dirty pages if a zone fills up and so effectively
+throttle the process. This may decrease the performance of a single process
+since it cannot use all of system memory to buffer the outgoing writes
+anymore but it preserve the memory on other nodes so that the performance
+of other processes running on other nodes will not be affected.
+
+Allowing regular swap effectively restricts allocations to the local
+node unless explicitly overridden by memory policies or cpuset
+configurations.
+
+=============================================================
+
+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 user can override this setting. It may be beneficial to switch
-off zone reclaim if the system is used for a file server and all
-of memory should be used for caching files from disk.
+The default is 1 percent.
-It may be beneficial to switch this on if one wants to do zone
-reclaim regardless of the numa distances in the system.
+=============================================================
+
+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.
+
+The default value is 0.
git.openpandora.org / pandora-kernel.git / blobdiff