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

[Florian Fainelli]

2013/12/4 Mel Gorman <mgorman@xxxxxxx>:
> 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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