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Subject: Re: [slub p4 6/7] slub: per cpu cache for partial pages
From: Lin Ming <ming.m.lin@intel.com>
To: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>,
        David Rientjes <rientjes@google.com>, Andi Kleen <andi@firstfloor.org>,
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        Matt Mackall <mpm@selenic.com>, Eric Dumazet <eric.dumazet@gmail.com>,
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        lkml <linux-kernel@vger.kernel.org>
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Date: Wed, 24 Aug 2011 15:26:23 +0800
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On Wed, Aug 10, 2011 at 5:12 AM, Christoph Lameter <cl@linux.com> wrote:
> Allow filling out the rest of the kmem_cache_cpu cacheline with pointers to
> partial pages. The partial page list is used in slab_free() to avoid
> per node lock taking.
> 
> In __slab_alloc() we can then take multiple partial pages off the per
> node partial list in one go reducing node lock pressure.
> 
> We can also use the per cpu partial list in slab_alloc() to avoid scanning
> partial lists for pages with free objects.
> 
> The main effect of a per cpu partial list is that the per node list_lock
> is taken for batches of partial pages instead of individual ones.
> 
> Potential future enhancements:
> 
> 1. The pickup from the partial list could be perhaps be done without disabling
>   interrupts with some work. The free path already puts the page into the
>   per cpu partial list without disabling interrupts.

Nice patches!

Could you share possible ways for this potential enhancement?

Thanks,
Lin Ming

> 
> 2. __slab_free() may have some code paths that could use optimization.