linux-kernel - Re: [slub p4 6/7] slub: per cpu cache for partial pages

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Date:	Wed, 24 Aug 2011 08:57:55 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Lin Ming <ming.m.lin@...el.com>
cc:	Pekka Enberg <penberg@...helsinki.fi>,
	David Rientjes <rientjes@...gle.com>,
	Andi Kleen <andi@...stfloor.org>, tj@...nel.org,
	Metathronius Galabant <m.galabant@...glemail.com>,
	Matt Mackall <mpm@...enic.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Adrian Drzewiecki <z@...e.net>,
	"Li, Shaohua" <shaohua.li@...el.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [slub p4 6/7] slub: per cpu cache for partial pages

On Wed, 24 Aug 2011, Lin Ming wrote:

> > 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?

In order to avoid disabling interrupts in the allocation paths the state
that has to be kept in kmem_cache_cpu needs to be minimized so that it can
be swapped atomically using a this_cpu_cmpxchg. This means getting rid of
the node and slab fields I guess. Working on some patches to that effect.

Once that is done one can with a this_cpu_cmpxchg_double take over the per
cpu slab and then use that information to update the slab page etc.

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