Em Thu, Nov 27, 2014 at 09:56:21AM +0900, Namhyung Kim escreveu: > Hi Milian, > > On Wed, 26 Nov 2014 19:11:01 +0100, Milian Wolff wrote: > > I tried this on a benchmark of mine: > > > > before: > > [ perf record: Woken up 196 times to write data ] > > [ perf record: Captured and wrote 48.860 MB perf.data (~2134707 samples) ] > > > > after, with dwarf,512 > > [ perf record: Woken up 18 times to write data ] > > [ perf record: Captured and wrote 4.401 MB perf.data (~192268 samples) ] > > > > What confuses me though is the number of samples. When the workload is > > equal, > > shouldn't the number of samples stay the same? Or what does this mean? The > > resulting reports both look similar enough. > > It's bogus - it just calculates the number of samples based on the file > size (with fixed sample size). I think we should either show the correct > number as we post-process samples for build-id detection or simply > remove it.
Well, since we setup the perf_event_attr we could perhaps do a better job at estimating this... In this case we even know how much stack_dump we will take at each sample, that would be major culprit for the current mis estimation. And yes, if we do the post processing, we can do a precise calculation. - Arnaldo -- To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
