linux-kernel - Re: [patch] slub: default min_partial to at least highest cpus per node

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Message-ID: <alpine.DEB.2.00.0904071445200.27115@chino.kir.corp.google.com>
Date:	Tue, 7 Apr 2009 14:46:49 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Christoph Lameter <cl@...ux.com>
cc:	Pekka Enberg <penberg@...helsinki.fi>, linux-kernel@...r.kernel.org
Subject: Re: [patch] slub: default min_partial to at least highest cpus per
  node

On Tue, 7 Apr 2009, Christoph Lameter wrote:

> The partial list sizes cannot be adjusted.

It's adjustable via /sys/kernel/slab/cache/min_partial.

> There is just a mininum size
> that is set via MIN_PARTIAL. Currently we use that to avoid trips to the
> page allocator by keeping the list artificially long. This should not be
> done because it increases memory overhead by keeping slab pages around
> with no objects.

That memory is easily reclaimed with kmem_cache_shrink().

> If the page allocator trips are not that expensive
> anymore then there is no reason to keep these slab pages around. A hot
> page can be reused by any other subsystemm in the kernel.
> 

Right, but right now allocating new slabs is extremely slow compared to 
using a partial slab.
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