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authorAndrew Bresticker <abrestic@google.com>2011-11-03 00:40:29 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2011-11-03 03:07:03 +0400
commitc1e2ee2dc436574880758b3836fc96935b774c32 (patch)
treeaa496a9ba20e06749194faa4dbb14b6046e6b06b /include/linux/cgroup.h
parent080d676de095a14ecba14c0b9a91acb5bbb634df (diff)
downloadlinux-c1e2ee2dc436574880758b3836fc96935b774c32.tar.xz
memcg: replace ss->id_lock with a rwlock
While back-porting Johannes Weiner's patch "mm: memcg-aware global reclaim" for an internal effort, we noticed a significant performance regression during page-reclaim heavy workloads due to high contention of the ss->id_lock. This lock protects idr map, and serializes calls to idr_get_next() in css_get_next() (which is used during the memcg hierarchy walk). Since idr_get_next() is just doing a look up, we need only serialize it with respect to idr_remove()/idr_get_new(). By making the ss->id_lock a rwlock, contention is greatly reduced and performance improves. Tested: cat a 256m file from a ramdisk in a 128m container 50 times on each core (one file + container per core) in parallel on a NUMA machine. Result is the time for the test to complete in 1 of the containers. Both kernels included Johannes' memcg-aware global reclaim patches. Before rwlock patch: 1710.778s After rwlock patch: 152.227s Signed-off-by: Andrew Bresticker <abrestic@google.com> Cc: Paul Menage <menage@gmail.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Ying Han <yinghan@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/cgroup.h')
-rw-r--r--include/linux/cgroup.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index da7e4bc34e8c..1b7f9d525013 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -516,7 +516,7 @@ struct cgroup_subsys {
struct list_head sibling;
/* used when use_id == true */
struct idr idr;
- spinlock_t id_lock;
+ rwlock_t id_lock;
/* should be defined only by modular subsystems */
struct module *module;