linux-kernel - Re: [GIT PULL] Lockless SLUB slowpaths for v3.1-rc1

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Date:	Sun, 31 Jul 2011 23:45:46 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Christoph Lameter <cl@...ux.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>, hughd@...gle.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [GIT PULL] Lockless SLUB slowpaths for v3.1-rc1

On Sun, 2011-07-31 at 13:24 -0700, David Rientjes wrote:
> And although slub is definitely heading in the right direction regarding 
> the netperf benchmark, it's still a non-starter for anybody using large 
> NUMA machines for networking performance.  On my 16-core, 4 node, 64GB 
> client/server machines running netperf TCP_RR with various thread counts 
> for 60 seconds each on 3.0:
> 
> 	threads		SLUB		SLAB		diff
> 	 16		76345		74973		- 1.8%
> 	 32		116380		116272		- 0.1%
> 	 48		150509		153703		+ 2.1%
> 	 64		187984		189750		+ 0.9%
> 	 80		216853		224471		+ 3.5%
> 	 96		236640		249184		+ 5.3%
> 	112		256540		275464		+ 7.4%
> 	128		273027		296014		+ 8.4%
> 	144		281441		314791		+11.8%
> 	160		287225		326941		+13.8%

That looks like a pretty nasty scaling issue. David, would it be
possible to see 'perf report' for the 160 case? [ Maybe even 'perf
annotate' for the interesting SLUB functions. ]

On Sun, 2011-07-31 at 13:24 -0700, David Rientjes wrote:
> And although I've developed a mutable slab allocator, SLAM, that makes all 
> of this irrelevant since it's a drop-in replacement for slab and slub, I 
> can't legitimately propose it for inclusion because it lacks the debugging 
> capabilities that slub excels in and there's an understanding that Linus 
> won't merge another stand-alone allocator until one is removed.

Nick tried that with SLQB and it didn't work out. I actually even tried
to maintain it out-of-tree for a while but eventually gave up. So no,
I'm not interested in merging a new allocator either. I would be,
however, interested to see the source code.

			Pekka

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