linux-kernel - Re: [PATCH RFC] [X86] performance improvement for memcpy

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Message-ID: <4AF89989.2010402@zytor.com>
Date:	Mon, 09 Nov 2009 14:36:57 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	"Ma, Ling" <ling.ma@...el.com>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] [X86] performance improvement for memcpy_64.S by
 fast string.

On 11/09/2009 10:54 AM, Andi Kleen wrote:
>> Ling's numbers didn't seem to show a significant slowdown on Core 2 (it
>> was something like 0.95x baseline in the worst case, and most of the
>> cases were positive) so Core 2 doesn't seem to have a problem.
> 
> I ran quite a lot of micro benchmarks with various alignments and sizes
> the 'q' variant was not always a win. I haven't checked that particular
> version though.

Well, if you have concrete information about what the problem cases are,
then please provide it.  If you don't, but have a hunch where these
potential problems may lie, then please indicate what they might be.
Otherwise, there isn't any actionable information here.

	-hpa
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