On Tue, 14 Jun 2011 09:36:51 +0200 Michal Hocko <mhocko@xxxxxxx> wrote: > On Mon 13-06-11 12:16:48, KAMEZAWA Hiroyuki wrote: > > From 18b12e53f1cdf6d7feed1f9226c189c34866338c Mon Sep 17 00:00:00 2001 > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > Date: Mon, 13 Jun 2011 11:25:43 +0900 > > Subject: [PATCH 5/5] memcg: fix percpu cached charge draining frequency > > > > For performance, memory cgroup caches some "charge" from res_counter > > into per cpu cache. This works well but because it's cache, > > it needs to be flushed in some cases. Typical cases are > > 1. when someone hit limit. > > 2. when rmdir() is called and need to charges to be 0. > > > > But "1" has problem. > > > > Recently, with large SMP machines, we see many kworker runs because > > of flushing memcg's cache. Bad things in implementation are > > that even if a cpu contains a cache for memcg not related to > > a memcg which hits limit, drain code is called. > > > > This patch does > > D) don't call at softlimit reclaim. > > I think this needs some justification. The decision is not that > obvious IMO. I would say that this is a good decision because cached > charges will not help to free any memory (at least not directly) during > background reclaim. What about something like: > " > We are not draining per cpu cached charges during soft limit reclaim > because background reclaim doesn't care about charges. It tries to free > some memory and charges will not give any. > Cached charges might influence only selection of the biggest soft limit > offender but as the call is done only after the selection has been > already done it makes no change. > " > > Anyway, wouldn't it be better to have this change separate from the > async draining logic change? Hmm. I think calling "draining" at softlimit is just a bug. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx 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>