Re: [PATCH] mm: page_alloc: avoid wakeup kswapd on the unintended node

From: Weijie Yang
Date: Fri Aug 29 2014 - 05:12:28 EST

On Fri, Aug 29, 2014 at 4:12 PM, Mel Gorman <mgorman@xxxxxxx> wrote:
> On Fri, Aug 29, 2014 at 03:03:19PM +0800, Weijie Yang wrote:
>> When enter page_alloc slowpath, we wakeup kswapd on every pgdat
>> according to the zonelist and high_zoneidx. However, this doesn't
>> take nodemask into account, and could prematurely wakeup kswapd on
>> some unintended nodes.
>> This patch uses for_each_zone_zonelist_nodemask() instead of
>> for_each_zone_zonelist() in wake_all_kswapds() to avoid the above situation.
>> Signed-off-by: Weijie Yang <weijie.yang@xxxxxxxxxxx>
> Just out of curiousity, did you measure a problem due to this or is
> the patch due to code inspection? It was known that we examined useless
> nodes but assumed to not be a problem because the watermark check should
> prevent spurious wakeups. However, we do a cpuset check and this patch
> is consistent with that so regardless of why you wrote the patch

It is a patch due to code review :-)

> Acked-by: Mel Gorman <mgorman@xxxxxxx>
> --
> Mel Gorman
> SUSE Labs
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