On Wed, 2011-06-29 at 12:37 +0200, Robert Richter wrote: > I looked at the interrupt handlers. The events are always determined > from a per-cpu array: > > cpuc = &__get_cpu_var(cpu_hw_events); > ... > event = cpuc->events[idx]; > > In case of interrupts the event should then always be a hw event (or > uninitialized). Even if the interrupt was triggered by a different > source, it would always be mapped to the same event and the check > is_sampling_event() would be meaningless. I'm probably not quite getting what you mean, but how is is_sampling_event() meaningless? the INT bit is enabled for _all_ events, whether they were configured as a sampling event or not. Its just that for !sampling events we shouldn't attempt to generate any output. > There are other occurrences of perf_event_overflow() in > kernel/events/core.c for events of type PERF_TYPE_SOFTWARE. These > events are initialized with sample_period set and a check would always > be true too. I'm failing to see what you mean, where do we always set event->attr.sample_period for software events? > For both cases I stil don't see a reason for the check. You're going to have to spell things out for me, I'm really not getting your argument. > Anyway, would the following extentension of the check above ok? > > if (unlikely(!is_sampling_event(event) && !event->attr.sample_type)) > ... > > With no bits set in attr.sample_type the sample would be empty and > nothing to report. Now, with this change, samples that have data to > report wouldn't be dropped anymore. Also, could you explain in what way data is dropped? Where do non-sampling events need to write sample data? -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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