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

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

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.

If you look beyond x86, there's several issues that get into the
picture. i2c clock chips & power control chips are slow (the i2c bus
itself is). You don't want to spin for hundreds of microsecs while you
do those transactions.

I have seen many cases where the clock control can be done quite
quickly, but on the other hand, the voltage control takes dozens of ms
to reach the target value & stabilize.

That could be done asynchronously .. as long as the scheduler doesn't
constantly hammer it with change requests.

Cheers,
Ben.