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

[Jesse Barnes <jbarnes@virtuousgeek.org>]

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