Re: cpuidle asymmetry (was Re: [RFC PATCH V4 5/5] cpuidle: cpuidledriver for apm)

[Len Brown]

> > Moorestown is already an example of an asymmetric system,
> > since its deepest c-state is available on cpu0, but not on cpu1.
> > So it needs different tables for each cpu. 
> 
> wtf are these hardware guys smoking and how the heck are we supposed to
> schedule on such a machine? Prefer to keep cpu1 busy while idling cpu0?

they are smoking micro-amps:-)

S0i3 on cpu0 can be entered only after cpu1 is already off-line,
among other system hardware dependencies...

So it makes no sense to export S0i3 as a c-state on cpu1.

When cpu1 is online, the scheduler treats it as a normal SMP.

cheers,
-Len Brown, Intel Open Source Technology Center


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