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

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Date:	Thu, 13 Dec 2007 01:13:52 +0100 (CET)
From:	Jan Engelhardt <jengelh@...putergmbh.de>
To:	Rene Herman <rene.herman@...il.com>
cc:	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFT] Port 0x80 I/O speed


On Dec 13 2007 00:54, Jan Engelhardt wrote:
>
>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.)
>
>00:46 takeshi:../cpu0/cpufreq # echo 300000 >scaling_min_freq
>00:46 takeshi:../cpu0/cpufreq # echo 933000 >scaling_max_freq
>00:42 takeshi:/dev/shm # for ((x=1;x<=10;++x)); do ./port80 ; done
>cycles: out 1514, in 584
^ most likely 300 MHz state
>cycles: out 1371, in 516
^ 533 MHz state
>cycles: out 1291, in 472
^ ??
>cycles: out 1304, in 437
^ ??
>cycles: out 1308, in 410
^ ??
>cycles: out 1315, in 419
^ 933 MHz state
>cycles: out 1315, in 419
>cycles: out 1314, in 419
>cycles: out 1315, in 420
>cycles: out 1315, in 419

...this is in stark contrast to values of other users, where,
skimming through the mails, higher cpu frequencies yields
higher out/in values, but not so on TM5800. Highly interesting.
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