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

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Date:	Fri, 29 Aug 2014 09:12:11 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Weijie Yang <weijie.yang@...sung.com>
Cc:	'Andrew Morton' <akpm@...ux-foundation.org>,
	'Rik van Riel' <riel@...hat.com>,
	'Johannes Weiner' <hannes@...xchg.org>, rientjes@...gle.com,
	'Weijie Yang' <weijie.yang.kh@...il.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 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

Acked-by: Mel Gorman <mgorman@...e.de>

-- 
Mel Gorman
SUSE Labs
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