linux-ext4 - Re: [PATCH 2/4] mm: slub: Do not wake kswapd for SLUBs speculative high-order allocations

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Date:	Wed, 18 May 2011 09:09:29 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	David Rientjes <rientjes@...gle.com>
CC:	Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Colin King <colin.king@...onical.com>,
	Raghavendra D Prabhu <raghu.prabhu13@...il.com>,
	Jan Kara <jack@...e.cz>, Chris Mason <chris.mason@...cle.com>,
	Christoph Lameter <cl@...ux.com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 2/4] mm: slub: Do not wake kswapd for SLUBs speculative
 high-order allocations

On 5/17/11 12:10 AM, David Rientjes wrote:
> On Fri, 13 May 2011, Mel Gorman wrote:
>
>> To avoid locking and per-cpu overhead, SLUB optimisically uses
>> high-order allocations and falls back to lower allocations if they
>> fail.  However, by simply trying to allocate, kswapd is woken up to
>> start reclaiming at that order. On a desktop system, two users report
>> that the system is getting locked up with kswapd using large amounts
>> of CPU.  Using SLAB instead of SLUB made this problem go away.
>>
>> This patch prevents kswapd being woken up for high-order allocations.
>> Testing indicated that with this patch applied, the system was much
>> harder to hang and even when it did, it eventually recovered.
>>
>> Signed-off-by: Mel Gorman<mgorman@...e.de>
> Acked-by: David Rientjes<rientjes@...gle.com>

Christoph? I think this patch is sane although the original rationale 
was to workaround kswapd problems.

                 Pekka
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