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

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Message-ID: <alpine.DEB.2.00.1105161410090.4353@chino.kir.corp.google.com>
Date:	Mon, 16 May 2011 14:10:24 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Mel Gorman <mgorman@...e.de>
cc:	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>,
	Pekka Enberg <penberg@...nel.org>,
	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 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>
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