Fedora kernel-2.6.17-1.2142_FC4 patched with stable patch-2.6.17.4-vs2.0.2-rc26.diff

[linux-2.6.git] / Documentation / sysctl / vm.txt

diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index fc3e413..a46c10f 100644 (file)
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -24,11 +24,17 @@ Currently, these files are in /proc/sys/vm:
 - dirty_writeback_centisecs
 - max_map_count
 - min_free_kbytes
 - dirty_writeback_centisecs
 - max_map_count
 - min_free_kbytes

+- laptop_mode
+- block_dump
+- drop-caches
+- zone_reclaim_mode
+- zone_reclaim_interval

 
 ==============================================================
 
 dirty_ratio, dirty_background_ratio, dirty_expire_centisecs,
 
 ==============================================================
 
 dirty_ratio, dirty_background_ratio, dirty_expire_centisecs,

-dirty_writeback_centisecs:
+dirty_writeback_centisecs, vfs_cache_pressure, laptop_mode,
+block_dump, swap_token_timeout, drop-caches:

 
 See Documentation/filesystems/proc.txt
 
 
 See Documentation/filesystems/proc.txt
 


@@ -44,7 +50,7 @@ of free memory left when userspace requests more memory.
 When this flag is 1, the kernel pretends there is always enough
 memory until it actually runs out.
 
 When this flag is 1, the kernel pretends there is always enough
 memory until it actually runs out.
 

-When this flag is 2, the kernel uses a "strict overcommit" 
+When this flag is 2, the kernel uses a "never overcommit"

 policy that attempts to prevent any overcommit of memory.  
 
 This feature can be very useful because there are a lot of
 policy that attempts to prevent any overcommit of memory.  
 
 This feature can be very useful because there are a lot of


@@ -99,3 +105,76 @@ This is used to force the Linux VM to keep a minimum number
 of kilobytes free.  The VM uses this number to compute a pages_min
 value for each lowmem zone in the system.  Each lowmem zone gets 
 a number of reserved free pages based proportionally on its size.
 of kilobytes free.  The VM uses this number to compute a pages_min
 value for each lowmem zone in the system.  Each lowmem zone gets 
 a number of reserved free pages based proportionally on its size.

+
+==============================================================
+
+percpu_pagelist_fraction
+
+This is the fraction of pages at most (high mark pcp->high) in each zone that
+are allocated for each per cpu page list.  The min value for this is 8.  It
+means that we don't allow more than 1/8th of pages in each zone to be
+allocated in any single per_cpu_pagelist.  This entry only changes the value
+of hot per cpu pagelists.  User can specify a number like 100 to allocate
+1/100th of each zone to each per cpu page list.
+
+The batch value of each per cpu pagelist is also updated as a result.  It is
+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.
+
+================================================================
+
+zone_reclaim_interval:
+
+The time allowed for off node allocations after zone reclaim
+has failed to reclaim enough pages to allow a local allocation.
+
+Time is set in seconds and set by default to 30 seconds.
+
+Reduce the interval if undesired off node allocations occur. However, too
+frequent scans will have a negative impact onoff node allocation performance.
+