Re: pm qos and cpufreq interaction [Was: pm qos infrastructure and interface]

[Dominik Brodowski <linux@dominikbrodowski.net>]

Hi Mark,

On Wed, Oct 24, 2007 at 02:21:50PM -0700, Mark Gross wrote:
> > On Thu, Oct 04, 2007 at 02:51:39PM -0700, Mark Gross wrote:
> > What about cpu_throughput{_min,_max}, as being something considered to be
> > proportional to the CPU frequency? This way, the cpufreq policy notifiers
> > might be able to utilize the pm_qos infrastructure; but maybe even also the
> > userspace interface (at least the min freq/max freq one)... Haven't thought
> > this through, but maybe you (or someone else) has.
> 
> I've only thought it though enough to choose to avoid cpufreq
> interactions.  
> 
> Sadly core frequency is not proportional to throughput on X86
> processors.  I don't know how one would reliably quantify cpu throughput
> in this context, other than defining latencies.  

Well it's not exactly throughput, but the CPU frequency surely has an
influence on it and also affects the quality of the service provided...

> I could see something like this to prevent cpufreq throttling at bad
> times, but how common of an issue is this any more?  

Hopefully none :) I was just wondering whether this generalization would
make sense in the big scheme of things (i.e. grand plan of unified power
management)...

> Its good to hear from you.  Will you be at the ELC conference in Linz
> next week?

Unfortunately not.

Best,
	Dominik