On Tue, 19 Feb 2013, Daniel Lezcano wrote:
> I am working on identifying the different wakeup sources from the
> interrupts and I have a question regarding the timer broadcast.
>
> The broadcast timer is setup to the next event and that will wake up any
> idle cpu belonging to the "broadcast cpumask", right ?
>
> The cpu which has been woken up will look for each cpu the next-event
> and send an IPI to wake it up.
>
> Although, it is possible the sender of this IPI may not be concerned by
> the timer expiration and has been woken up just for sending the IPI, right ?
Correct.
> If this is correct, is it possible to setup the timer irq affinity to a
> cpu which will be concerned by the timer expiration ? so we prevent an
> unnecessary wake up for a cpu.
It is possible, but we never implemented it.
If we go there, we want to make that conditional on a property flag,
because some interrupt controllers especially on x86 only allow to
move the affinity from interrupt context, which is pointless.
Thanks,
tglx
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