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

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Date:	Fri, 29 Aug 2014 17:12:21 +0800
From:	Weijie Yang <weijie.yang.kh@...il.com>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Weijie Yang <weijie.yang@...sung.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>, rientjes@...gle.com,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: page_alloc: avoid wakeup kswapd on the unintended node

On Fri, Aug 29, 2014 at 4:12 PM, Mel Gorman <mgorman@...e.de> 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@...sung.com>
>
> 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@...e.de>
>
> --
> Mel Gorman
> SUSE Labs
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