On 06/12/2015 06:08 PM, Frederic Weisbecker wrote: > On Fri, Jun 12, 2015 at 09:32:45AM +0200, Peter Zijlstra wrote: >> On Thu, Jun 11, 2015 at 07:36:05PM +0200, Frederic Weisbecker wrote: >>> Restart the tick when necessary from the irq exit path. It makes nohz >>> full more flexible and allow it to piggyback the tick restart on the >>> scheduler IPI in the future instead of sending a dedicated IPI that >>> often doubles the scheduler IPI on task wakeup. This will require >>> careful review of resched_curr() callers. >> >> This seems to assume schedule_ipi() callers use irq_exit(), this is >> false. > > Indeed there will be that too. Note the current patch doesn't yet rely on > schedule_ipi(), we are still using the nohz ipis. But introducing the > tick restart on irq exit prepares for later piggybacking on scheduler_ipi(). > > I think this will involve changes on got_nohz_idle_kick(), renamed to > got_nohz_kick() and include nohz full related checks to trigger the > irq_enter()/exit() pair.
I maybe saying something obvious here, nevertheless; I am not sure about other archs, but atleast on powerpc after handling an interrupt, we will call irq_exit() and reevaluate starting of ticks. So in our case even if scheduler_ipi() callers do not call irq_exit(), it will be called after handling the reschedule interrupt. Regards Preeti U Murthy > -- 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/