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From: Wes Felter <wesley@felter.org>
To: linux-kernel@vger.kernel.org
Subject: Re: HELP: cpufreq on HT and/or SMP systems
Date: Fri, 01 Aug 2003 17:36:21 -0500	[thread overview]
Message-ID: <pan.2003.08.01.22.36.19.940443@felter.org> (raw)
In-Reply-To: 200307312353.54735.gallir@uib.es

On Thu, 31 Jul 2003 23:53:54 +0200, Ricardo Galli wrote:

> I have some doubts regarding cpufreq for SMP systems (for developing 
> http://mnm.uib.es/~gallir/cpudyn/).
> 
> If I remember well, I read a while ago that cpufreq didn't work in SMP 
> systems, but reading the docs and kernel/cpufreq.c, it seems there should be 
> any problem? 
> 
> Is it true?
> 
> OTH, I trying it on a P4 HT, and it works, changes in the frequency of one of 
> the "cpu's",  changes both. 

That makes sense, since the CPU only has one clock.

> What happens in the case of several real cpu's? Does it keep the same 
> frequency for every cpu? According to a comment in cpufreq.c, it seems that 
> each cpu might have different frequencies.

AFAIK no SMP systems have voltage/frequency scaling (SpeedStep/PowerNow).
I've heard that ACPI P-states works on SMP, but if it's not doing
voltage/frequency scaling then I don't know what it's doing.

Wes Felter - wesley@felter.org - http://felter.org/wesley/


  reply	other threads:[~2003-08-01 22:40 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-07-31 21:53 HELP: cpufreq on HT and/or SMP systems Ricardo Galli
2003-08-01 22:36 ` Wes Felter [this message]
2003-08-01 22:51   ` Xavier Bestel
2003-08-01 23:01     ` Wes Felter
2003-08-05 11:16       ` Pavel Machek
2003-08-06  8:10         ` Dominik Brodowski

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