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

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Date:	Thu, 12 Nov 2009 15:42:15 +0800
From:	"Ma, Ling" <ling.ma@...el.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Cyrill Gorcunov <gorcunov@...il.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.

Hi H. Peter Anvin

After running the test program in my attachment-memcpy.c on Nehalem platform,
when copy size is less 1024 memcopy_c function has very big regression compared
with original memcopy function. I think we have to combine original memcopy and
memcpy_c for Nehalem and other modern CPUS, so memcpy_new is on the right track.

Thanks
Ling 
( 

>-----Original Message-----
>From: H. Peter Anvin [mailto:hpa@...or.com]
>Sent: 2009年11月12日 13:27
>To: Ma, Ling
>Cc: Cyrill Gorcunov; Ingo Molnar; Ingo Molnar; Thomas Gleixner; linux-kernel
>Subject: Re: [PATCH RFC] [X86] performance improvement for memcpy_64.S by fast
>string.
>
>On 11/11/2009 08:49 PM, Ma, Ling wrote:
>> Hi All
>> The attachment is latest memcpy.c, please update by
>> "cc -o memcpy memcpy.c -O2 -m64".
>
>OK... given that there seems to be no point since the actual code we're
>talking about modifying doesn't ever actually get executed on the real
>kernel, we can just drop this, right?
>
>	-hpa
>
>--
>H. Peter Anvin, Intel Open Source Technology Center
>I work for Intel.  I don't speak on their behalf.


View attachment "memcpy.c" of type "text/plain" (6138 bytes)