On Sat, Jul 04, 2015 at 04:50:07PM +0800, Jisheng Zhang wrote: > Dear Russell, > > On Sat, 4 Jul 2015 09:26:23 +0100 > Russell King - ARM Linux <li...@arm.linux.org.uk> wrote: > > > On Sat, Jul 04, 2015 at 01:19:30PM +0800, Jisheng Zhang wrote: > > > On Marvell Berlin SoCs, the cpu's local timer is shutdown when the cpu > > > goes to a deep idle state, then the timer framework will be notified to > > > use a broadcast timer instead. The broadcast timer uses dw-apb-ictl as > > > interrupt chip, this patch adds irq_set_affinity support so that the > > > going to deep idle state cpu can set the interrupt affinity of the > > > broadcast interrupt to avoid unnecessary wakeups and IPIs. > > > > NAK to this patch. > > > > The real question is - if CPU0 is the CPU going offline, why is it > > still receiving _any_ interrupts - all interrupts should be migrated > > off it, including the chained interrupts. > > I think it's due to broadcast timer interrupt. Let me describe the situation: > > 1. cpu1 is going offline > 2. cpuidle notify timer framework to use a broadcast timer instead due to > localtimer > is CLOCK_EVT_FEAT_C3STOP > 3. when timer is expired, CPU0 will be waken up by the timer interrupt if it > has > gone offline > 4. CPU0 sends broadcast timer IPI to CPU1
If CPU1 is going offline, then CPU1 should have no interrupts delivered to it. However, this is not the situation you're testing - in your results below, and your "simple test" you never take CPU1 offline. -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net. -- 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/
