linux-kernel - Re: [patch 04/11] mm: memcg: per-priority per-zone hierarchy scan generations

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Message-Id: <20110914164045.f8074468.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Wed, 14 Sep 2011 16:40:45 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Johannes Weiner <jweiner@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Balbir Singh <bsingharora@...il.com>,
	Ying Han <yinghan@...gle.com>, Michal Hocko <mhocko@...e.cz>,
	Greg Thelen <gthelen@...gle.com>,
	Michel Lespinasse <walken@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Christoph Hellwig <hch@...radead.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 04/11] mm: memcg: per-priority per-zone hierarchy scan
 generations

On Wed, 14 Sep 2011 07:56:34 +0200
Johannes Weiner <jweiner@...hat.com> wrote:

> On Wed, Sep 14, 2011 at 09:55:04AM +0900, KAMEZAWA Hiroyuki wrote:
> > On Tue, 13 Sep 2011 13:03:01 +0200
> > Johannes Weiner <jweiner@...hat.com> wrote:
> No, the hierarchy iteration in shrink_zone() is done after a single
> memcg, which is equivalent to the old code: scan all zones at all
> priority levels from a memcg, then move on to the next memcg.  This
> also works because of the per-zone per-priority last_scanned_child:
> 
> 	for each priority
> 	  for each zone
> 	    mem = mem_cgroup_iter(root)
> 	    scan(mem)
> 
> priority-12 + zone-1 will yield memcg-1.  priority-12 + zone-2 starts
> at its own last_scanned_child, so yields memcg-1 as well, etc.  A
> second reclaimer that comes in with priority-12 + zone-1 will receive
> memcg-2 for scanning.  So there is no change in behaviour for limit
> reclaim.
> 
ok, thanks.

> > If so, I need to abandon node-selection-logic for reclaim-by-limit
> > and nodemask-for-memcg which shows me very good result. 
> > I'll be sad ;)
> 
> With my clarification, do you still think so?
> 

No. Thank you. 

Regards,
-Kame

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