linux-kernel - Re: SLUB defrag pull request?

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Message-Id: <1225191983.27477.16.camel@penberg-laptop>
Date:	Tue, 28 Oct 2008 13:06:23 +0200
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	Miklos Szeredi <miklos@...redi.hu>, nickpiggin@...oo.com.au,
	hugh@...itas.com, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: Re: SLUB defrag pull request?

On Thu, 2008-10-23 at 19:14 +0200, Eric Dumazet wrote:
> [PATCH] slub: slab_alloc() can use prefetchw()
> 
> Most kmalloced() areas are initialized/written right after allocation.
> 
> prefetchw() gives a hint to cpu saying this cache line is going to be
> *modified*, even if first access is a read.
> 
> Some architectures can save some bus transactions, acquiring
> the cache line in an exclusive way instead of shared one.
> 
> Same optimization was done in 2005 on SLAB in commit 
> 34342e863c3143640c031760140d640a06c6a5f8 
> ([PATCH] mm/slab.c: prefetchw the start of new allocated objects)
> 
> Signed-off-by: Eric Dumazet <dada1@...mosbay.com>

Christoph, I was sort of expecting a NAK/ACK from you before merging
this. I would be nice to have numbers on this but then again I don't see
how this can hurt either.

		Pekka

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