linux-kernel - Re: [patch v3 -mm 1/3] memcg: integrate soft reclaim tighter with zone shrinking code

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Message-ID: <20130517071240.GC25158@dhcp22.suse.cz>
Date:	Fri, 17 May 2013 09:12:40 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Tejun Heo <tj@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Johannes Weiner <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Ying Han <yinghan@...gle.com>, Hugh Dickins <hughd@...gle.com>,
	Glauber Costa <glommer@...allels.com>,
	Michel Lespinasse <walken@...gle.com>,
	Greg Thelen <gthelen@...gle.com>,
	Balbir Singh <bsingharora@...il.com>
Subject: Re: [patch v3 -mm 1/3] memcg: integrate soft reclaim tighter with
 zone shrinking code

On Thu 16-05-13 15:12:00, Tejun Heo wrote:
> Sorry about the delay.  Just getting back to memcg.
> 
> On Mon, May 13, 2013 at 09:46:10AM +0200, Michal Hocko wrote:
> ...
> > during the first pass. Only groups which are over their soft limit or
> > any of their parents up the hierarchy is over the limit are considered
> 
> ancestors?

Well, ancestors might or might not be part of the hierarchy, so while it
is much shorter I consider the original more precise.

> > +static void shrink_zone(struct zone *zone, struct scan_control *sc)
> > +{
> > +	bool do_soft_reclaim = mem_cgroup_should_soft_reclaim(sc);
> > +	unsigned long nr_scanned = sc->nr_scanned;
> > +
> > +	__shrink_zone(zone, sc, do_soft_reclaim);
> > +
> > +	/*
> > +	 * No group is over the soft limit or those that are do not have
> > +	 * pages in the zone we are reclaiming so we have to reclaim everybody
> > +	 */
> > +	if (do_soft_reclaim && (sc->nr_scanned == nr_scanned)) {
> > +		__shrink_zone(zone, sc, false);
> > +		return;
> > +	}
> > +}
> 
> Maybe the following is easier to follow?
> 
> 	if (mem_cgroup_should_soft_reclaim(sc)) {
> 		__shrink_zone(zone, sc, true);
> 		if (sc->nr_scanned == nr_scanned)
> 			__shrink_zone(zone, sc, false);
> 	} else {
> 		__shrink_zone(zone, sc, false);
> 	}
> 
> But it's a minor point, please feel free to ignore.

I will stick with the original code as I have some plans to build on top
of that.

>   Reviewed-by: Tejun Heo <tj@...nel.org>

Thank you!

> 
> Thanks.
> 
> -- 
> tejun

-- 
Michal Hocko
SUSE Labs
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