linux-kernel - Re: [patch 2/2] slub: enforce cpuset restrictions for cpu slabs

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Message-ID: <alpine.DEB.2.00.0903040959530.17033@chino.kir.corp.google.com>
Date:	Wed, 4 Mar 2009 10:06:49 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
cc:	Paul Menage <menage@...gle.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 2/2] slub: enforce cpuset restrictions for cpu slabs

On Wed, 4 Mar 2009, Christoph Lameter wrote:

> That would make the per object memory policies in SLUB configurable? If
> you can do that without regression and its clean then it would be
> acceptable.
> 

Yes, if `slab_hardwall' is enabled for a cpuset it will attempt to replace 
the cpu slab with a partial slab on an allowed node.

> Again if you want per object memory policies in SLUB then it needs to be
> added consistently. You would also f.e. have to check for an MPOL_BIND
> condition where you check for cpuset nodes and make sure that __slab_alloc
> goes round robin on MPOL_INTERLEAVE etc etc. You end up with a similar
> nightmare implementation of that stuff as in SLAB.

I agree that we should avoid adding mempolicy support, especially 
MPOL_INTERLEAVE at the object level since that would totally avoid the 
fastpath for any task using it.
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