linux-kernel - Re: excessive CPU utilization by isolate

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Message-ID: <alpine.DEB.2.00.1206271803280.10830@chino.kir.corp.google.com>
Date:	Wed, 27 Jun 2012 18:06:59 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Minchan Kim <minchan@...nel.org>
cc:	Rik van Riel <riel@...hat.com>, Jim Schutt <jaschut@...dia.gov>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	"ceph-devel@...r.kernel.org" <ceph-devel@...r.kernel.org>
Subject: Re: excessive CPU utilization by isolate_freepages?

On Thu, 28 Jun 2012, Minchan Kim wrote:

> >>> > > https://lkml.org/lkml/2012/6/21/30
> >> > 
> > Not sure if Jim is using memcg; if not, then this won't be helpful.
> > 
> 
> 
> It doesn't related to memcg.
> if compaction_alloc can't find suitable migration target, it returns NULL.
> Then, migrate_pages should be exit.
> 

If isolate_freepages() is going to fail, then this zone should have been 
skipped when checking for compaction_suitable().  In Jim's perf output, 
compaction_suitable() returns COMPACT_CONTINUE for a transparent hugepage.  
Why is zone_watermark_ok(zone, 0 low_wmark + 1024, 0, 0) succeeding if 
isolate_freepages() is going to fail?
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