[RFC][PATCH 3/3] memcg documenation soft limit (Yet Another One)

From: KAMEZAWA Hiroyuki
Date: Fri Mar 06 2009 - 05:39:56 EST


From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>

Documentation for softlimit (3/3)

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
Documentation/cgroups/memory.txt | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)

Index: mmotm-2.6.29-Mar3/Documentation/cgroups/memory.txt
===================================================================
--- mmotm-2.6.29-Mar3.orig/Documentation/cgroups/memory.txt
+++ mmotm-2.6.29-Mar3/Documentation/cgroups/memory.txt
@@ -322,6 +322,25 @@ will be charged as a new owner of it.
- a cgroup which uses hierarchy and it has child cgroup.
- a cgroup which uses hierarchy and not the root of hierarchy.

+5.4 softlimit
+ Memory cgroup supports softlimit and has 2 params for control.
+ - memory.softlimit_in_bytes
+ - softlimit to this cgroup.
+ - memory.softlimit_priority.
+ - priority of this cgroup at softlimit reclaim.
+ Allowed priority level is 3-0 and 3 is the lowest.
+ If 0, this cgroup will not be target of softlimit.
+
+ At memory shortage of the system (or local node/zone), softlimit helps
+ kswapd(), a global memory recalim kernel thread, and inform victim cgroup
+ to be shrinked to kswapd.
+
+ Victim selection logic:
+ The kernel searches from the lowest priroty(3) up to the highest(1).
+ If it find a cgroup witch has memory larger than softlimit, steal memory
+ from it.
+ If multiple cgroups are on the same priority, each cgroup wil be a
+ victim in turn.

6. Hierarchy support


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