Re: [RFC] (How to) Let idle CPUs sleep

[Jesse Barnes]

Srivatsa Vaddagiri wrote:

> Even if we were to go for this tickless design, the fundamental question
> remains: who wakes up the (sleeping) idle CPU upon a imbalance? Does some other
> (busy) CPU wake it up (which makes the implementation complex) or the idle CPU 
> checks imbalance itself at periodic intervals (which restricts the amount of
> time a idle CPU may sleep).
>  
Waking it up at fork or exec time might be doable, and having a busy CPU 
wake up other CPUs wouldn't add too much complexity, would it?

> I guess George's experience in implementing tickless systems is that
> it is more of an overhead for a general purpose OS like Linux. George?
>  
The latest patches seem to do tick skipping rather than wholesale 
ticklessness.  Admittedly, the latter is a more invasive change, but one 
that may end up being simpler in the long run.  But maybe George did a 
design like that in the past and rejected it?

Jesse
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