linux-kernel - Re: [RFT] Port 0x80 I/O speed

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Date:	Tue, 11 Dec 2007 17:28:28 -0800
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Rene Herman <rene.herman@...il.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>, dpreed@...d.com,
	Alan Cox <alan@...rguk.ukuu.org.uk>, pavel@....cz,
	andi@...stfloor.org, rol@...917.net,
	Krzysztof Halasa <khc@...waw.pl>, david@...idnewall.com,
	hpa@...or.com, john@...ffel.org, linux-os@...logic.com
Subject: Re: [RFT] Port 0x80 I/O speed

On Wed, 12 Dec 2007 00:31:18 +0100 Rene Herman wrote:

> Good day.
> 
> Would some people on x86 (both 32 and 64) be kind enough to compile and run 
> the attached program? This is about testing how long I/O port access to port 
> 0x80 takes. It measures in CPU cycles so CPU speed is crucial in reporting.
> 
> Posted a previous incarnation of this before, buried in the outb 0x80 thread 
> which had a serialising problem. This one should as far as I can see measure 
> the right thing though. Please yell if you disagree...
> 
> For me, on a Duron 1300 (AMD756 chipset) I have a constant:
> 
> rene@...e4:~/src/port80$ su -c ./port80
> cycles: out 2400, in 2400
> 
> and on a PII 400 (Intel 440BX chipset) a constant:
> 
> rene@...p:~/src/port80$ su -c ./port80
> cycles: out 553, in 251
> 
> Results are (mostly) independent of compiler optimisation, but testing with 
> an -O2 compile should be most useful. Thanks!

(-m32 build on x86_64)

midway:/home/rddunlap/src # ./port80
cycles: out 2702, in 1903
midway:/home/rddunlap/src # ./port80
cycles: out 2688, in 1893
midway:/home/rddunlap/src # ./port80
cycles: out 2703, in 1909
midway:/home/rddunlap/src # ./port80
cycles: out 2687, in 1893
midway:/home/rddunlap/src # ./port80
cycles: out 2687, in 1893
midway:/home/rddunlap/src # ./port80
cycles: out 2701, in 1907
midway:/home/rddunlap/src # ./port80
cycles: out 2701, in 1919
midway:/home/rddunlap/src # ./port80
cycles: out 2687, in 1893
midway:/home/rddunlap/src # ./port80
cycles: out 2701, in 1909
midway:/home/rddunlap/src # ./port80
cycles: out 2706, in 1906

/proc/cpuinfo says CPU speed is
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      :               Intel(R) Pentium(R) D CPU 3.00GHz
stepping        : 4
cpu MHz         : 2999.988


---
~Randy
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