linux-kernel - Re: [this_cpu_xx V6 7/7] this_cpu: slub aggressive use of this

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Date:	Wed, 14 Oct 2009 11:56:29 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Pekka Enberg <penberg@...helsinki.fi>
cc:	Mel Gorman <mel@....ul.ie>, David Rientjes <rientjes@...gle.com>,
	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>
Subject: Re: [this_cpu_xx V6 7/7] this_cpu: slub aggressive use of this_cpu
 operations in the hotpaths

On Wed, 14 Oct 2009, Pekka Enberg wrote:

> SLAB is able to queue lots of large objects but SLUB can't do that because it
> has no queues. In SLUB, each CPU gets a page assigned to it that serves as a
> "queue" but the size of the queue gets smaller as object size approaches page
> size.
>
> We try to offset that with higher order allocations but IIRC we don't increase
> the order linearly with object size and cap it to some reasonable maximum.

You can test to see if larger pages have an influence by passing

slub_max_order=6

or so on the kernel command line.

You can force a large page use in slub by setting

slub_min_order=3

f.e.

Or you can force a mininum number of objecxcts in slub through f.e.

slub_min_objects=50



slub_max_order=6 slub_min_objects=50

should result in pretty large slabs with lots of in page objects that
allow slub to queue better.




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