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authorKAMEZAWA Hiroyuki2009-01-07 18:07:55 -0800
committerLinus Torvalds2009-01-08 08:31:04 -0800
commitc1e862c1f5ad34771b6d0a528cf681e0dcad7c86 (patch)
treee3ac7ca8cfe5ac02b0df83a4aef5f37e59d7d61f /Documentation
parentc8dad2bb6307f5b00f804a686917105206a4d5c9 (diff)
memcg: new force_empty to free pages under group
By memcg-move-all-accounts-to-parent-at-rmdir.patch, there is no leak of memory usage and force_empty is removed. This patch adds "force_empty" again, in reasonable manner. memory.force_empty file works when #echo 0 (or some) > memory.force_empty and have following function. 1. only works when there are no task in this cgroup. 2. free all page under this cgroup as much as possible. 3. page which cannot be freed will be moved up to parent. 4. Then, memcg will be empty after above echo returns. This is much better behavior than old "force_empty" which just forget all accounts. This patch also check signal_pending() and above "echo" can be stopped by "Ctrl-C". [akpm@linux-foundation.org: cleanup] Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Pavel Emelyanov <xemul@openvz.org> 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/controllers/memory.txt27
1 files changed, 23 insertions, 4 deletions
diff --git a/Documentation/controllers/memory.txt b/Documentation/controllers/memory.txt
index 58f32c166fac..54253b7a8db2 100644
--- a/Documentation/controllers/memory.txt
+++ b/Documentation/controllers/memory.txt
@@ -237,11 +237,30 @@ reclaimed.
A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a
cgroup might have some charge associated with it, even though all
tasks have migrated away from it.
-Such charges are moved to its parent as much as possible and freed if parent
-is full. Both of RSS and CACHES are moved to parent.
-If both of them are busy, rmdir() returns -EBUSY.
+Such charges are freed(at default) or moved to its parent. When moved,
+both of RSS and CACHES are moved to parent.
+If both of them are busy, rmdir() returns -EBUSY. See 5.1 Also.
-5. TODO
+5. Misc. interfaces.
+
+5.1 force_empty
+ memory.force_empty interface is provided to make cgroup's memory usage empty.
+ You can use this interface only when the cgroup has no tasks.
+ When writing anything to this
+
+ # echo 0 > memory.force_empty
+
+ Almost all pages tracked by this memcg will be unmapped and freed. Some of
+ pages cannot be freed because it's locked or in-use. Such pages are moved
+ to parent and this cgroup will be empty. But this may return -EBUSY in
+ some too busy case.
+
+ Typical use case of this interface is that calling this before rmdir().
+ Because rmdir() moves all pages to parent, some out-of-use page caches can be
+ moved to the parent. If you want to avoid that, force_empty will be useful.
+
+
+6. TODO
1. Add support for accounting huge pages (as a separate controller)
2. Make per-cgroup scanner reclaim not-shared pages first