- drop-caches
- zone_reclaim_mode
- min_unmapped_ratio
+- min_slab_ratio
- panic_on_oom
==============================================================
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.
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
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.
=============================================================
+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.
-The default value is 0.
+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.