linux-kernel - RE: [PATCH RFC 2/2] [x86] Optimize copy_page by re-arranging instruction sequence and saving register

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Message-ID: <B2310DA9850C8743AA7AA0055500E90F0FD70B53@SHSMSX102.ccr.corp.intel.com>
Date:	Fri, 12 Oct 2012 14:54:54 +0000
From:	"Ma, Ling" <ling.ma@...el.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	"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>,
	"iant@...gle.com" <iant@...gle.com>
Subject: RE: [PATCH RFC 2/2] [x86] Optimize copy_page by re-arranging
 instruction sequence and saving register

> If you can't test the CPUs who run this code I think it's safer if you
> add a new variant for Atom, not change the existing well tested code.
> Otherwise you risk performance regressions on these older CPUs.

I found one older machine, and tested the code on it, the results between them are almost the same as below(attached cpu info).
      1                         copy_page_org   copy_page_new
      2 TPT: Len 4096, alignment  0/ 0: 2252    2218
      3 TPT: Len 4096, alignment  0/ 0: 2244    2193
      4 TPT: Len 4096, alignment  0/ 0: 2261    2227
      5 TPT: Len 4096, alignment  0/ 0: 2235    2244
      6 TPT: Len 4096, alignment  0/ 0: 2261    2184

Thanks
Ling

Download attachment "xeon-cpu-info" of type "application/octet-stream" (2376 bytes)