Re: SMP cpu deep sleep

[Hans Kristian Rosbach <hk@isphuset.no>]

On Fri, 2004-08-20 at 10:58, Jeff Sipek wrote:
> On Friday 20 August 2004 04:06, Hans Kristian Rosbach wrote:
> > While reading through hotplug and speedstep patches
> > I came to think of a feature I think might be useful.
> >
> > In an SMP system there are several cpus, this generates
> > extra heat and power consuption even on idle load.
> > Is there a way to put all cpus but cpu1 into a kind of
> > deep sleep? Cpu1 would have to do all work (including irqs)
> > of course.
> 
> With Rusty's Hotplug CPU, a userspace script should be able to do this
by 
> cat'ing 1 or 0 into the appropriate sysfs file.

Nice, this can be done on non-hotplug motherboards as well?
How much time does it take to take the cpu up again?

It would need to be awakened whenever the activity increases
again, and that delay should not be too long.

Also, what effect does this have on cpu power consumtion
and thermal output? Does it lower it below normal idle?

-HK