On Fri, Dec 18, 2015 at 10:58:17AM +0000, Suzuki K. Poulose wrote: > We have a global Enable/Disable for CCI PMU and thats what we use > currently. To be able to reprogram the counters with the event period > (we program the counter with a specific count in pmu::start() and at > overflow irq handler, not to be confused with the sampling period, which > is not supported), we need to be sure that the counter value has been updated. > > May be we could check the event->hw->state to see if we need to reprogram it.
Right, have a look at arch/x86/kernel/cpu/perf_event.c:x86_pmu_enable() If there's new events, it does two loops over the events. The first loop does stop(PERF_EF_UPDATE) any counter that got moved. The second loop does start(PERF_EF_RELOAD) on moved and new events. The PERF_HES_ARCH bit is used to preserve the stopped state of counters that were programmed but temporarily stopped. -- 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/
