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

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Message-ID: <alpine.DEB.2.00.1108020913180.18965@router.home>
Date:	Tue, 2 Aug 2011 09:15:03 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	David Rientjes <rientjes@...gle.com>
cc:	Pekka Enberg <penberg@...nel.org>,
	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 Mon, 1 Aug 2011, David Rientjes wrote:

> On Mon, 1 Aug 2011, Pekka Enberg wrote:
>
> > Btw, I haven't measured this recently but in my testing, SLAB has
> > pretty much always used more memory than SLUB. So 'throwing more
> > memory at the problem' is definitely a reasonable approach for SLUB.
> >
>
> Yes, slub _did_ use more memory than slab until the alignment of
> struct page.  That cost an additional 128MB on each of these 64GB
> machines, while the total slab usage on the client machine systemwide is
> ~75MB while running netperf TCP_RR with 160 threads.

I guess that calculation did not include metadata structures (alien caches
and the NR_CPU arrays in kmem_cache) etc? These are particularly costly on SLAB.

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