linux-kernel - Re: [slub p4 0/7] slub: per cpu partial lists V4

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Date:	Sat, 20 Aug 2011 13:48:43 +0300 (EEST)
From:	Pekka Enberg <penberg@...nel.org>
To:	Christoph Lameter <cl@...ux.com>
cc:	linux-kernel@...r.kernel.org, rientjes@...gle.com,
	andi@...stfloor.org, mgorman@...e.de, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org
Subject: Re: [slub p4 0/7] slub: per cpu partial lists V4

On Tue, 9 Aug 2011, Christoph Lameter wrote:
> V3->V4 : Use a single linked per cpu list instead of a per cpu array.
> 	This results in improvements even for the single threaded
> 	case. I think this is ready for more widespread testing (-next?)
> 	The number of partial pages per cpu is configurable via
> 	/sys/kernel/slab/<name>/cpu_partial
>
> V2->V3 : Work on the todo list. Still some work to be done to reduce
>         code impact and make this all cleaner. (Pekka: patch 1-3
>         are cleanup patches of general usefulness. You got #1 already
>         2+3 could be picked up w/o any issue).
>
> The following patchset introduces per cpu partial lists which allow
> a performance increase of around ~10-20% with hackbench on my Sandybridge
> processor.
>
> These lists help to avoid per node locking overhead. Allocator latency
> could be further reduced by making these operations work without
> disabling interrupts (like the fastpath and the free slowpath) but that
> is another project.
>
> It is interesting to note that BSD has gone to a scheme with partial
> pages only per cpu (source: Adrian). Transfer of cpu ownerships is
> done using IPIs. Probably too much overhead for our taste. The approach
> here keeps the per node partial lists essentially meaning the "pages"
> in there have no cpu owner.

These patches are now in slub/partial branch of slab.git. I'll probably 
queue them for linux-next early next week if they don't explode on my 
machine.

 			Pekka
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