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

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Message-ID: <475F1DC6.5090403@keyaccess.nl>
Date:	Wed, 12 Dec 2007 00:31:18 +0100
From:	Rene Herman <rene.herman@...il.com>
To:	Linux Kernel <linux-kernel@...r.kernel.org>
CC:	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: [RFT] Port 0x80 I/O speed

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!

Rene.

View attachment "port80.c" of type "text/plain" (1139 bytes)