From c1e2ee2dc436574880758b3836fc96935b774c32 Mon Sep 17 00:00:00 2001 From: Andrew Bresticker Date: Wed, 2 Nov 2011 13:40:29 -0700 Subject: 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 Cc: Paul Menage Cc: Li Zefan Acked-by: KAMEZAWA Hiroyuki Cc: Ying Han Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/cgroup.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/cgroup.h') 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; -- cgit v1.2.3