Re: [BUGFIX][PATCH 5/5] memcg: fix percpu cached charge draining frequency

KAMEZAWA Hiroyuki
2011-06-15T00:17:18Z

On Mon, 13 Jun 2011 14:25:01 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Mon, 13 Jun 2011 12:16:48 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>
> > >From 18b12e53f1cdf6d7feed1f9226c189c34866338c Mon Sep 17 00:00:00 2001
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > 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
> > A) check percpu cache contains a useful data or not.
> > B) check other asynchronous percpu draining doesn't run.
> > C) don't call local cpu callback.
> > D) don't call at softlimit reclaim.
> >
> >
> > ...
> >
> > +DEFINE_MUTEX(percpu_charge_mutex);
>
> I made this static. If we later wish to give it kernel-wide scope then
> "percpu_charge_mutex" will not be a good choice of name.

Thank you.
And, yes..... memcg_cached_charge_mutex ?

Thanks,
-Kame