linux-kernel - Re: [patch v4] Soft limit rework

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Message-ID: <20130604180859.GB9321@dhcp22.suse.cz>
Date:	Tue, 4 Jun 2013 20:08:59 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Balbir Singh <bsingharora@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm <linux-mm@...ck.org>,
	"cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	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>, Tejun Heo <tj@...nel.org>
Subject: Re: [patch v4] Soft limit rework

On Tue 04-06-13 23:27:05, Balbir Singh wrote:
> > OK, let me summarize. The primary intention is to get rid of the current
> > soft reclaim infrastructure which basically bypasses the standard
> > reclaim and tight it directly into shrink_zone code. This also means
> > that the soft reclaim doesn't reclaim at priority 0 and that it is
> > active also for the targeted (aka limit) reclaim.
> >
> > Does this help?
> >
> 
> Yes. What are the limitations of no-priority 0 reclaim?

I am not sure I understand the question. What do you mean by
limitations?

The priority-0 scan was always a crude hack. With a lot of pages in on
the LRU it might cause huge big stalls during direct reclaim. There are
workloads which benefited from such an aggressive reclaim - e.g.
streaming IO but that doesn't justify this kind of reclaim.
-- 
Michal Hocko
SUSE Labs
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