linux-kernel - Re: excessive CPU utilization by isolate

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Message-ID: <4FEBB0FA.2070203@kernel.org>
Date:	Thu, 28 Jun 2012 10:18:50 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	David Rientjes <rientjes@...gle.com>
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 06/28/2012 10:06 AM, David Rientjes wrote:

> 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?
> 


zone_watermark_ok doesn't consider migratetype but suitable_migrate_target
does consider one.

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-- 
Kind regards,
Minchan Kim
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