linux-kernel - Re: [PATCH 2/4] slqb: Record what node is local to a kmem_cache

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Date:	Tue, 22 Sep 2009 16:38:32 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Nick Piggin <npiggin@...e.de>,
	Christoph Lameter <cl@...ux-foundation.org>,
	heiko.carstens@...ibm.com, sachinp@...ibm.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Tejun Heo <tj@...nel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH 2/4] slqb: Record what node is local to a kmem_cache_cpu

Hi Mel,

On Tue, Sep 22, 2009 at 3:54 PM, Mel Gorman <mel@....ul.ie> wrote:
> When freeing a page, SLQB checks if the page belongs to the local node.
> If it is not, it is considered a remote free. On the allocation side, it
> always checks the local lists and if they are empty, the page allocator
> is called. On memoryless configurations, this is effectively a memory
> leak and the machine quickly kills itself in an OOM storm.
>
> This patch records what node ID is considered local to a CPU. As the
> management structure for the CPU is always allocated from the closest
> node, the node the CPU structure resides on is considered "local".
>
> Signed-off-by: Mel Gorman <mel@....ul.ie>

I don't understand how the memory leak happens from the above
description (or reading the code). page_to_nid() returns some crazy
value at free time? The remote list isn't drained properly?

                        Pekka
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