linux-kernel - Re: [PATCH 0/3] Removal of lumpy reclaim V2

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Message-ID: <4F85C813.2050206@redhat.com>
Date:	Wed, 11 Apr 2012 14:06:11 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Mel Gorman <mgorman@...e.de>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	Hugh Dickins <hughd@...gle.com>, Ying Han <yinghan@...gle.com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] Removal of lumpy reclaim V2

On 04/11/2012 01:52 PM, Mel Gorman wrote:
> On Wed, Apr 11, 2012 at 01:17:02PM -0400, Rik van Riel wrote:

>> Next step: get rid of __GFP_NO_KSWAPD for THP, first
>> in the -mm kernel
>>
>
> Initially the flag was introduced because kswapd reclaimed too
> aggressively. One would like to believe that it would be less of a problem
> now but we must avoid a situation where the CPU and reclaim cost of kswapd
> exceeds the benefit of allocating a THP.

Since kswapd and the direct reclaim code now use
the same conditionals for calling compaction,
the cost ought to be identical.

I agree this is something we should shake out
in -mm for a while though, before considering a
mainline merge.

Andrew, would you be willing to take a removal
of __GFP_NO_KSWAPD in -mm, and push it to Linus
for the 3.6 kernel if no ill effects are seen
in -mm and -next?
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