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

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Message-ID: <476093B6.7080306@zytor.com>
Date:	Wed, 12 Dec 2007 18:06:46 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jan Engelhardt <jengelh@...putergmbh.de>
CC:	Rene Herman <rene.herman@...il.com>,
	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,
	john@...ffel.org, linux-os@...logic.com
Subject: Re: [RFT] Port 0x80 I/O speed

Jan Engelhardt wrote:
> On Dec 12 2007 00:31, Rene Herman wrote:
>> 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.
>>
> 
> Transmeta TM5800 CPU with nominal frequency 933 MHz, but it has a
> hardware(!) 'ondemand' governor over the range of frequencies that
> the user allowed scaling over, irrespective of the software governor.
> (That is, if the CPU can do 300,533 and 933 MHz, and setting the
> min/max to 300/533 will cause the hardware to 'ondemand' between 300
> and 533 only. And that even if 'performance' is set on the software
> side - so the only way to enforce 'performance' is to actually set
> min=933.)
> 

Actually it has two different ones (economy and performance), you can 
use the "longrun" utility to select which one.

Either way, all Transmeta processors have a fixed TSC, so there is no issue.

	-hpa
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