Re: [Cbe-oss-dev] [Patch] Resending: cell_add_spuaware_cpufreq_governor.diff

[Christian Krafft <krafft@de.ibm.com>]

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On Wed, 16 Apr 2008 14:08:25 +0200
Arnd Bergmann <arnd@arndb.de> wrote:

> On Wednesday 16 April 2008, Christian Krafft wrote:
> > This patch is also missing a correct load calculation.
> > It works pretty well for spu's running at full time or idling, but not so
> > well for mixed load (i.e. each spu running 50 percent of the time we would
> > switch to fullspeed instead of half speed).
> 
> So why should that be something to optimize for? If the SPUs are all idle,
> I would assume we'd be better off throwing the tasks off and putting them
> into low-power mode, rather than changing the frequency, right?
> 
> What's the point of your driver, really?
> 
> 	Arnd <><

What we have now is good enough to
- switch to full power if there are spus active (waiting or running) and 
- switch to low power if not.

What we have now is not good enough to
- switch to low power if there are spus waiting, but none are running

As we cannot _yet_ differentiate between spus waiting and spus running means
that in _some_ cases we will not save as much power as we could.

The point of submitting the driver is to get it working.
Further improvements will follow of course.

-- 
Mit freundlichen Gruessen,
kind regards,

Christian Krafft
IBM Systems & Technology Group,
Linux Kernel Development
IT Specialist


Vorsitzender des Aufsichtsrats:	Martin Jetter
Geschaeftsfuehrung:		Herbert Kircher
Sitz der Gesellschaft:		Boeblingen
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