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Date: Wed, 3 Aug 2011 09:09:48 -0500 (CDT)
From: Christoph Lameter <cl@linux.com>
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To: David Rientjes <rientjes@google.com>
cc: Pekka Enberg <penberg@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>, hughd@google.com,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [GIT PULL] Lockless SLUB slowpaths for v3.1-rc1
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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?