On Wed, 10 Aug 2011 11:20:33 -0700 Andrew Bresticker <abrestic@xxxxxxxxxx> wrote: > 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@xxxxxxxxxx> Hopefully, the changelog should be based on the latest Linus's git tree or mmotm. Even now, if a system has multiple hierarchies of memcg, I think the contention will happen. Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>