On Fri, 2014-09-26 at 07:16 +0100, Namhyung Kim wrote: > > It would be doable, I guess, but what > > if someone *wants* to have sched clock as the timestamps source (because > > it's cheap) but still be able to correlate them with userspace? In this > > case two separate timestamps are required to do the approximation. > > But by collecting two timestamps, you'll loose the win of the first > timestamp, no? But I can ask for both timestamps only being collected on "low bandwidth" events, in particular context switches and/or periodic (eg. 10ms hrtimer) software events. Then I have loads of normal normal samples, timestamped with sched clock only, and every now and then one with both timestamps which then I can use for time correlation. The whole point is that the frequency of such "synchronisation" event can be much (much!) lower than of the normal samples, but it still allows pretty good approximation (I was getting accuracy of ~1 microsecond and better with sched_switch trace event marked with additional raw monotonic timestamp). Pawel PS. Have you sent a couple of the messages via some kind of gmane's proxy? All the mail addresses got rather messed up... -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
