Messages in this thread | | | Date | Thu, 23 Apr 2020 14:09:57 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH v3] perf/record: add num-synthesize-threads option |
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On Wed, Apr 22, 2020 at 08:50:38AM -0700, Ian Rogers wrote: > From: Stephane Eranian <eranian@google.com> >
SNIP
> That is the processing is 1.49% of execution time and there is plenty to > make parallel. This is shown in the benchmark in this patch: > https://lore.kernel.org/lkml/20200415054050.31645-2-irogers@google.com/ > Computing performance of multi threaded perf event synthesis by > synthesizing events on CPU 0: > Number of synthesis threads: 1 > Average synthesis took: 127729.000 usec (+- 3372.880 usec) > Average num. events: 21548.600 (+- 0.306) > Average time per event 5.927 usec > Number of synthesis threads: 2 > Average synthesis took: 88863.500 usec (+- 385.168 usec) > Average num. events: 21552.800 (+- 0.327) > Average time per event 4.123 usec > Number of synthesis threads: 3 > Average synthesis took: 83257.400 usec (+- 348.617 usec) > Average num. events: 21553.200 (+- 0.327) > Average time per event 3.863 usec > Number of synthesis threads: 4 > Average synthesis took: 75093.000 usec (+- 422.978 usec) > Average num. events: 21554.200 (+- 0.200) > Average time per event 3.484 usec > Number of synthesis threads: 5 > Average synthesis took: 64896.600 usec (+- 353.348 usec) > Average num. events: 21558.000 (+- 0.000) > Average time per event 3.010 usec > Number of synthesis threads: 6 > Average synthesis took: 59210.200 usec (+- 342.890 usec) > Average num. events: 21560.000 (+- 0.000) > Average time per event 2.746 usec > Number of synthesis threads: 7 > Average synthesis took: 54093.900 usec (+- 306.247 usec) > Average num. events: 21562.000 (+- 0.000) > Average time per event 2.509 usec > Number of synthesis threads: 8 > Average synthesis took: 48938.700 usec (+- 341.732 usec) > Average num. events: 21564.000 (+- 0.000) > Average time per event 2.269 usec > > Where average time per synthesized event goes from 5.927 usec with 1 > thread to 2.269 usec with 8. This isn't a linear speed up as not all of > synthesize code has been made parallel. If the synthesis time was about > 10 seconds then using 8 threads may bring this down to less than 4.
Acked-by: Jiri Olsa <jolsa@redhat.com>
thanks, jirka
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