Peter Zijlstra <[email protected]> writes: > On Wed, Aug 20, 2014 at 03:36:08PM +0300, Alexander Shishkin wrote: >> For counters such as instruction tracing, it is useful for the decoder >> to know which tasks are running when the event is first scheduled in, >> before the first sched_switch. >> >> To single out such instruction tracing pmus, this patch alse introduces >> ITRACE PMU capability. > > You forgot to tell why. Also explain why. > > The next context switch event will also tell you the previous task. So > this seems like superfluous information. Also if you really want this > you could simply emit an empty AUX record I suppose, no need to create > yet another record type.
Before the first sched_switch we don't actually know what pid/tid is running, so we can't make sense of the beginning of the trace without some event reordering trickery. We can use AUX for that as well, I guess this might be another use case for those flags in the AUX record. Changelog, got it. Adrian and Arnaldo cc'ed. Cheers, -- Alex -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
