linux-kernel - Re: Dependent CPU core speed reporting not updated with CPUFREQ_SHARED_TYPE

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Date:	Sat, 2 Jun 2007 02:43:25 -0400
From:	Dave Jones <davej@...hat.com>
To:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
Cc:	"Darrick J. Wong" <djwong@...ibm.com>, linux-kernel@...r.kernel.org
Subject: Re: Dependent CPU core speed reporting not updated with
	CPUFREQ_SHARED_TYPE_HW?

On Fri, Jun 01, 2007 at 06:59:25PM -0700, Venki Pallipadi wrote:

 > Hmmm. How about having a new cpufreq_sysfs entry to say
 > these CPUs are frequency dependent in hardware.

Wait, wasn't this the entire purpose of affected_cpus in the first
place? So we could see which CPUs would be affected by a frequency
change?  What went wrong here?

 > affected_cpus today has a single cpufreq directory for all affected_cpus
 > and we coordinate all CPUs in software. To change freq, we will have to
 > move among all affected_cpus and write an MSR.

This I think is where the problem started.  That these remained
independant.  Changing one should also affect the others that it
'affects'. Is that not the case?

 > Hardware coordination basically tells us that kernel can control
 > frequency
 > percpu, but underneath hardware will pick highest requested freq among a
 > group of CPUs. Instaed of handling this case as the existing software
 > coordination case above, we can add a new entry in cpufreq /sysfs
 > denoting
 > hardware coordinated CPU group.
 > 
 > Though it will be confusing with too many interfaces, I feel this is the
 > right way to go about here.

If 'affected_cpus' doesn't do the right thing, I'd vote for making it
do so over adding more interfaces.

	Dave

-- 
http://www.codemonkey.org.uk
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