aboutsummaryrefslogtreecommitdiffstats
path: root/Documentation
diff options
context:
space:
mode:
authorBalbir Singh <balbir@linux.vnet.ibm.com>2009-09-23 18:56:34 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-24 10:20:59 -0400
commita6df63615b943dbef22df04c19f4506330fe835e (patch)
treecd1b0ca72533a37d224d1424a5309f1924afe20b /Documentation
parent261fb61a8bf6d3bd964ae6f1e6af49585d30db51 (diff)
memory controller: soft limit documentation
Soft limits is a new feature for the memory resource controller, something similar has existed in the group scheduler in the form of shares. The CPU controllers interpretation of shares is very different though. Soft limits are the most useful feature to have for environments where the administrator wants to overcommit the system, such that only on memory contention do the limits become active. The current soft limits implementation provides a soft_limit_in_bytes interface for the memory controller and not for memory+swap controller. The implementation maintains an RB-Tree of groups that exceed their soft limit and starts reclaiming from the group that exceeds this limit by the maximum amount. This patch: Add documentation for soft limits Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/cgroups/memory.txt37
1 files changed, 36 insertions, 1 deletions
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index ab0a02172cf4..b871f2552b45 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -379,7 +379,42 @@ cgroups created below it.
379 379
380NOTE2: This feature can be enabled/disabled per subtree. 380NOTE2: This feature can be enabled/disabled per subtree.
381 381
3827. TODO 3827. Soft limits
383
384Soft limits allow for greater sharing of memory. The idea behind soft limits
385is to allow control groups to use as much of the memory as needed, provided
386
387a. There is no memory contention
388b. They do not exceed their hard limit
389
390When the system detects memory contention or low memory control groups
391are pushed back to their soft limits. If the soft limit of each control
392group is very high, they are pushed back as much as possible to make
393sure that one control group does not starve the others of memory.
394
395Please note that soft limits is a best effort feature, it comes with
396no guarantees, but it does its best to make sure that when memory is
397heavily contended for, memory is allocated based on the soft limit
398hints/setup. Currently soft limit based reclaim is setup such that
399it gets invoked from balance_pgdat (kswapd).
400
4017.1 Interface
402
403Soft limits can be setup by using the following commands (in this example we
404assume a soft limit of 256 megabytes)
405
406# echo 256M > memory.soft_limit_in_bytes
407
408If we want to change this to 1G, we can at any time use
409
410# echo 1G > memory.soft_limit_in_bytes
411
412NOTE1: Soft limits take effect over a long period of time, since they involve
413 reclaiming memory for balancing between memory cgroups
414NOTE2: It is recommended to set the soft limit always below the hard limit,
415 otherwise the hard limit will take precedence.
416
4178. TODO
383 418
3841. Add support for accounting huge pages (as a separate controller) 4191. Add support for accounting huge pages (as a separate controller)
3852. Make per-cgroup scanner reclaim not-shared pages first 4202. Make per-cgroup scanner reclaim not-shared pages first