Richard A. Smith richard at
Mon Nov 3 17:11:46 EST 2008

Jordan Crouse wrote:

> appropriate hook.  But if we want to suspend on idle, then we need to
> do it while are... you know... idle - so something  has to live there.
> I think we are basically saying the same thing here - userspace needs
> to give us the go-ahead to suspend, and we need to have the right
> latency programmed so that if all is well, we just suspend.  Or at least,
> we'll try to suspend and hope like heck it works.

I appear to have completely the wrong idea of what cpuidle would do for 
us then wrt suspend decisions.  I thought that cpuidle had the ability 
to report that the _system_ was idle.  For example if we are doing lots 
of DMA the cpu usage is very low but the system is far from idle.  Only 
the kernel has the proper knowledge of everything thats going on under 
the hood.

Where the ultimate decision to suspend is made doesn't seem to so 
important as the getting the inputs to that decision correct.  We don't 
appear to have a plan on how to get all the inputs.  Do we?

Thats what I'm proposing as one of the first steps and I was starting 
with cpuidle (perhaps incorrectly).  Replacing the current simplistic 
decision with something that we can mold into the Right way.  If cpuidle 
can't give us all the kernel info then we need start thinking about what 

Richard Smith  <richard at>
One Laptop Per Child

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