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: <B2310DA9850C8743AA7AA0055500E90F0FD70AC5@SHSMSX102.ccr.corp.intel.com>
Date:	Fri, 12 Oct 2012 09:07:43 +0000
From:	"Ma, Ling" <ling.ma@...el.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	Konrad Rzeszutek Wilk <konrad@...nel.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>,
	"iant@...gle.com" <iant@...gle.com>
Subject: RE: [PATCH RFC 2/2] [x86] Optimize copy_page by re-arranging
 instruction sequence and saving register

> > > So is that also true for AMD CPUs?
> > Although Bulldozer put 32byte instruction into decoupled 16byte entry
> > buffers, it still decode 4 instructions per cycle, so 4 instructions
> > will be fed into execution unit and
> > 2 loads ,1 write will be issued per cycle.
> 
> I'd be very interested with what benchmarks are you seeing that perf
> improvement on Atom and who knows, maybe I could find time to run them
> on Bulldozer and see how your patch behaves there :-).M
I use another benchmark from gcc, there are many code, and extract one simple benchmark, you may use it to test (cc -o copy_page copy_page.c),
my initial result shows new copy page version is still better on bulldozer machine, because the machine is first release, please verify result.
And CC to Ian.

Thanks
Ling


View attachment "copy_page.c" of type "text/plain" (5975 bytes)