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DateWed, 07 Sep 2005 12:14:55 -0400
FromBill Davidsen <>
SubjectRe: [PATCH 1/3] dynticks - implement no idle hz for x86
Srivatsa Vaddagiri wrote:
> On Sun, Sep 04, 2005 at 10:48:13PM -0700, Nishanth Aravamudan wrote:
>
>>Admittedly, I don't think SMP ARM has been around all that long? Maybe
>>the existing code just has not been extended.
>
>
> Yeah, maybe ARM never cared for SMP. But we do care :)
>
>
>>I'm not sure on this. It's going to be NULL for other architectures, or
>>end up being called by the reprogram() call for the last CPU to go idle,
>>right (presuming there isn't a separate TOD source, like in x86). I
>>think it is better to be in the reprogram() interface.
>
>
> Non-x86 could have it set to NULL, in which case it doesn't get called.
> (I know the current code does not take care of this situation).
> But having an explicit 'all_cpus_idle' interface may be good, since
> Tony talked of idling some devices when all CPUs are idle. So it
> probably has non-x86/PIT uses too.

If this is intended to reduce power, and it originally came from that
root, then this is the time to put in a hook for transitions to<=>from
the all-idle state. Various arch may have things other than the PIT
which should (or at least can) be stopped, and which need to be restarted.

--
-bill davidsen (davidsen@tmr.com)
"The secret to procrastination is to put things off until the
last possible moment - but no longer" -me
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