Pull kmalloc into release branch

[pandora-kernel.git] / Documentation / sysctl / vm.txt

diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 6910c01..86754eb 100644 (file)
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -27,6 +27,8 @@ Currently, these files are in /proc/sys/vm:
 - laptop_mode
 - block_dump
 - drop-caches
+- zone_reclaim_mode
+- panic_on_oom
 
 ==============================================================
 
@@ -120,3 +122,59 @@ set to pcp->high/4.  The upper limit of batch is (PAGE_SHIFT * 8)
 
 The initial value is zero.  Kernel does not use this value at boot time to set
 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
+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
+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
+page allocator will then reclaim easily reusable pages (those page
+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.
+
+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.
+
+=============================================================
+
+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.
+