On 02/19/2013 10:21 AM, Daniel Lezcano wrote: > On 02/19/2013 07:10 PM, Thomas Gleixner wrote: >> 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 Thomas for your quick answer. I will write a RFC patchset.
I'm curious what the use case is. I played with this code awhile ago, and AFAICT it's not used on sensible (i.e. modern) systems. Is there anything other than old x86 machines that needs it? --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
