linux-kernel - Re: high kswapd CPU usage when executing binaries from NFS w/ CMA and COMPACTION

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Message-ID: <CAGVrzcYMSVX=xkVqROjouvHpVup+jO00Wb66h2Wd=LFX47rDiw@mail.gmail.com>
Date:	Fri, 6 Dec 2013 14:51:00 -0800
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Mel Gorman <mgorman@...e.de>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	mhocko <mhocko@...e.cz>, hannes <hannes@...xchg.org>,
	riel <riel@...hat.com>, linux-mm <linux-mm@...ck.org>,
	"m.szyprowski" <m.szyprowski@...sung.com>,
	"marc.ceeeee" <marc.ceeeee@...il.com>
Subject: Re: high kswapd CPU usage when executing binaries from NFS w/ CMA and COMPACTION

2013/12/4 Mel Gorman <mgorman@...e.de>:
> On Tue, Dec 03, 2013 at 06:30:28PM -0800, Florian Fainelli wrote:
>> Hi all,
>>
>> I am experiencing high kswapd CPU usage on an ARMv7 system running
>> 3.8.13 when executing relatively large binaries from NFS. When this
>> happens kswapd consumes around 55-60% CPU usage and the applications
>> takes a huge time to load.
>>
>
> There were a number of changes made related to how and when kswapd
> stalls, particularly when pages are dirty. Brief check confirms that
>
> git log v3.8..v3.12 --pretty=one --author "Mel Gorman" mm/vmscan.c
>
> NFS dirty pages are problematic for compaction as dirty pages cannot be
> migrated until cleaned. I'd suggest checking if current mainline suffers
> the same problem and if not, focus on patches related to dirty page
> handling and kswapd throttling in mm/vmscan.c as backport candidates.

I have just backported these patches to 3.8.13 and am still seeing the
problem, although kswapd usage dropped considerably (by half
approximately). Will keep you updated once I have properly tested
current mainline on my platform. Thanks!
-- 
Florian
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