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

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Date:	Sat, 13 Aug 2011 11:28:30 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Christoph Lameter <cl@...ux.com>
cc:	Pekka Enberg <penberg@...helsinki.fi>,
	Andi Kleen <andi@...stfloor.org>, tj@...nel.org,
	Metathronius Galabant <m.galabant@...glemail.com>,
	Matt Mackall <mpm@...enic.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Adrian Drzewiecki <z@...e.net>, linux-kernel@...r.kernel.org
Subject: Re: [slub p4 0/7] slub: per cpu partial lists V4

On Tue, 9 Aug 2011, Christoph Lameter wrote:

> 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.
> 

I'm currently 35,000 feet above Chicago going about 611 mph, so what 
better time to benchmark this patchset on my netperf testing rack!

	threads		before		after
	 16		78031		74714  (-4.3%)
	 32		118269		115810 (-2.1%)
	 48		150787		150165 (-0.4%)
	 64		189932		187766 (-1.1%)
	 80		221189		223682 (+1.1%)
	 96		239807		246222 (+2.7%)
	112		262135		271329 (+3.5%)
	128		273612		286782 (+4.8%)
	144		280009		293943 (+5.0%)
	160		285972		299798 (+4.8%)

I'll review the patchset in detail, especially the cleanups and 
optimizations, when my wifi isn't so sketchy.
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