Re: [PATCH RFC 0/4] Scheduler idle notifiers and users

[Ingo Molnar <mingo@elte.hu>]

* Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:

> On Wed, 2012-02-08 at 15:23 -0500, Dave Jones wrote:
> > I think the biggest mistake we ever made with cpufreq was making it
> > so configurable. If we redesign it, just say no to plugin governors,
> > and
> > yes to a lot fewer sysfs knobs.
> > 
> > So, provide mechanism to kill off all the governors, and there's a
> > migration path from what we have now to something that just works
> > in a lot more cases, while remaining configurable enough for the
> > corner-cases.
> 
> On the other hand, the need for schedulable contxts may not 
> necessarily go away.

We will support it, but the *sane* hw solution is where 
frequency transitions can be done atomically. Most workloads 
change their characteristics very quickly, and so does their 
power management profile change.

The user-space driven policy model failed for that reason: it 
was *way* too slow in reacting) - and slow hardware transitions 
suck for a similar reason as well.

We accomodate all hardware as well as we can, but we *design* 
for proper hardware. So Peter is right, this should be done 
properly.

Thanks,

	Ingo