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

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Date:	Wed, 3 Aug 2011 09:09:48 -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 Tue, 2 Aug 2011, David Rientjes wrote:

> On Tue, 2 Aug 2011, Christoph Lameter wrote:
>
> > The per cpu partial lists only add the need for more memory if other
> > processors have to allocate new pages because they do not have enough
> > partial slab pages to satisfy their needs. That can be tuned by a cap on
> > objects.
> >
>
> The netperf benchmark isn't representative of a heavy slab consuming
> workload, I routinely run jobs on these machines that use 20 times the
> amount of slab.  From what I saw in the earlier posting of the per-cpu
> partial list patch, the min_partial value is set to half of what it was
> previously as a per-node partial list.  Since these are 16-core, 4 node
> systems, that would mean that after a kmem_cache_shrink() on a cache that
> leaves empty slab on the partial lists that we've doubled the memory for
> slub's partial lists systemwide.

Cutting down the potential number of empty slabs that we might possible
keep around because we have no partial slabs per node increases memory
usage?

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