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

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Date:	Wed, 11 Nov 2009 14:39:45 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
CC:	"Ma, Ling" <ling.ma@...el.com>, Ingo Molnar <mingo@...e.hu>,
	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 11/11/2009 12:34 PM, Cyrill Gorcunov wrote:
>                        			memcpy_orig	memcpy_new
> TPT: Len 1024, alignment  8/ 0:		490		570
> TPT: Len 2048, alignment  8/ 0:		826		329
> TPT: Len 3072, alignment  8/ 0:		441		464
> TPT: Len 4096, alignment  8/ 0:		579		596
> TPT: Len 5120, alignment  8/ 0:		723		729
> TPT: Len 6144, alignment  8/ 0:		859		861
> TPT: Len 7168, alignment  8/ 0:		996		994
> TPT: Len 8192, alignment  8/ 0:		1165		1127
> TPT: Len 9216, alignment  8/ 0:		1273		1260
> TPT: Len 10240, alignment  8/ 0:	1402		1395
> TPT: Len 11264, alignment  8/ 0:	1543		1525
> TPT: Len 12288, alignment  8/ 0:	1682		1659
> TPT: Len 13312, alignment  8/ 0:	1869		1815
> TPT: Len 14336, alignment  8/ 0:	1982		1951
> TPT: Len 15360, alignment  8/ 0:	2185		2110
> 
> I've run this test a few times and results almost the same,
> with alignment 1024, 3072, 4096, 5120, 6144, new version a bit slowly.
> 

Was the result for 2048 consistent (it seems odd in the extreme)... the
discrepancy between this result and Ling's results bothers me; perhaps
the right answer is to leave the current code for Core2 and use new code
(with a lower than 1024 threshold?) for NHM and K8?

	-hpa
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