linux-kernel - Re: [PATCH RFC] [x86] Optimize copy-page by reducing impact from HW prefetch

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Message-ID: <20110623022911.GM3263@one.firstfloor.org>
Date:	Thu, 23 Jun 2011 04:29:11 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	"Ma, Ling" <ling.ma@...el.com>
Cc:	Andi Kleen <andi@...stfloor.org>, "mingo@...e.hu" <mingo@...e.hu>,
	"hpa@...or.com" <hpa@...or.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] [x86] Optimize copy-page by reducing impact from HW prefetch

On Thu, Jun 23, 2011 at 09:01:19AM +0800, Ma, Ling wrote:
> Yes, I also have tested 64bit atom, it got 11.6% improvement.

That's a nice improvement, however I should add that in my experience 
copy_page micro benchmark improvements do not necessarily translate to
real world improvements. Most simple micro benchmark do not simulate
the typical page fault access pattern very well.

> Because older CPU almost all use prefetch-next-line mechanism, the patch should be useful to them.

Old in this case is P4 and ancient early stepping K8 only.

-Andi
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