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Date: Tue, 3 Mar 2009 13:35:08 -0800 (PST)
From: David Rientjes <rientjes@google.com>
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To: Christoph Lameter <cl@linux-foundation.org>
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       Andrew Morton <akpm@linux-foundation.org>,
       Paul Menage <menage@google.com>, Randy Dunlap <randy.dunlap@oracle.com>,
       linux-kernel@vger.kernel.org
Subject: Re: [patch 2/2] slub: enforce cpuset restrictions for cpu slabs
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On Tue, 3 Mar 2009, Christoph Lameter wrote:

> SLUB is also "dismissing" lots of other NUMA locality requirements since
> it relies on the page allocators for this. SLUB does *not* realize memory
> policy and/or cpuset support for individual objects.

Right, and this patch adds that.

> NUMA locality is
> implemented only (aside from explicit requests of memory from a
> certain node) when slab page allocations are performed.
> 

Yes, that is the current implementation.

For systems that use multiple cpusets, this allows objects for a task to 
be allocated on its assigned cpuset node(s); the only reasonable use case 
would be for memory isolation and/or NUMA optimizations.

Unfortunately, we can't add a slab hardwall flag to the cpuset to 
configure this behavior since that would require locking to dereference 
in the fastpath.