From: Eric Dumazet <eric.dumazet@gmail.com>
To: Christoph Lameter <cl@linux.com>
Cc: Mel Gorman <mgorman@suse.de>, Pekka Enberg <penberg@kernel.org>,
Konstantin Khlebnikov <khlebnikov@openvz.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Matt Mackall <mpm@selenic.com>
Subject: Re: [PATCH] mm-slab: allocate kmem_cache with __GFP_REPEAT
Date: Wed, 20 Jul 2011 18:31:05 +0200 [thread overview]
Message-ID: <1311179465.2338.62.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> (raw)
In-Reply-To: <alpine.DEB.2.00.1107201114480.1472@router.home>
Le mercredi 20 juillet 2011 A 11:17 -0500, Christoph Lameter a A(C)crit :
> On Wed, 20 Jul 2011, Eric Dumazet wrote:
>
> > Note that adding ____cacheline_aligned_in_smp on nodelists[] actually
> > helps performance, as all following fields are readonly after kmem_cache
> > setup.
>
> Well but that is not addresssing the same issue. Could you separate that
> out?
>
I would like this patch not being a performance regression. I know some
people really want fast SLAB/SLUB ;)
> The other question that follows from this is then: Does that
> alignment compensate for the loss of performance due to the additional
> lookup in hot code paths and the additional cacheline reference required?
>
In fact resulting code is smaller, because most fields are now with <
127 offset (x86 assembly code can use shorter instructions)
Before patch :
# size mm/slab.o
text data bss dec hex filename
22605 361665 32 384302 5dd2e mm/slab.o
After patch :
# size mm/slab.o
text data bss dec hex filename
22347 328929 32800 384076 5dc4c mm/slab.o
> The per node pointers are lower priority in terms of performance than the
> per cpu pointers. I'd rather have the per node pointers requiring an
> additional lookup. Less impact on hot code paths.
>
Sure. I'll post a V2 to have CPU array before NODE array.
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next prev parent reply other threads:[~2011-07-20 16:31 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-20 12:16 Konstantin Khlebnikov
2011-07-20 13:14 ` Pekka Enberg
2011-07-20 13:28 ` Konstantin Khlebnikov
2011-07-20 13:42 ` Pekka Enberg
2011-07-20 13:50 ` Konstantin Khlebnikov
2011-07-20 13:53 ` Pekka Enberg
2011-07-20 15:36 ` Christoph Lameter
2011-07-20 13:59 ` Konstantin Khlebnikov
2011-07-20 13:54 ` Christoph Lameter
2011-07-20 14:20 ` Mel Gorman
2011-07-20 14:32 ` Konstantin Khlebnikov
2011-07-20 14:40 ` Eric Dumazet
2011-07-20 14:47 ` Konstantin Khlebnikov
2011-07-20 13:43 ` Mel Gorman
2011-07-20 13:56 ` Christoph Lameter
2011-07-20 14:08 ` Eric Dumazet
2011-07-20 14:52 ` Christoph Lameter
2011-07-20 15:09 ` Eric Dumazet
2011-07-20 15:34 ` Christoph Lameter
2011-07-20 15:56 ` Eric Dumazet
2011-07-20 16:17 ` Christoph Lameter
2011-07-20 16:31 ` Eric Dumazet [this message]
2011-07-20 17:04 ` Eric Dumazet
2011-07-20 17:13 ` Christoph Lameter
2011-07-20 17:28 ` Pekka Enberg
2011-07-20 17:37 ` Christoph Lameter
2011-07-20 17:41 ` Pekka Enberg
2011-07-20 18:07 ` Matt Mackall
2011-07-21 7:18 ` Konstantin Khlebnikov
2011-07-20 19:09 ` Mel Gorman
2011-07-31 11:41 ` Konstantin Khlebnikov
2011-07-31 11:44 ` Pekka Enberg
2011-07-21 8:43 ` Eric Dumazet
2011-07-21 15:27 ` Christoph Lameter
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