Messages in this thread | | | Date | Mon, 19 Jun 2017 13:46:40 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH v3 1/n] perf/core: addressing 4x slowdown during per-process profiling of STREAM benchmark on Intel Xeon Phi |
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On Fri, Jun 16, 2017 at 05:22:29PM +0300, Alexey Budankov wrote: > On 16.06.2017 17:08, Alexey Budankov wrote: > >On 16.06.2017 12:09, Mark Rutland wrote: > >>On Fri, Jun 16, 2017 at 01:10:10AM +0300, Alexey Budankov wrote: > >>>On 15.06.2017 22:56, Mark Rutland wrote: > >>>>On Thu, Jun 15, 2017 at 08:41:42PM +0300, Alexey Budankov wrote: > >>>>>This series of patches continues v2 and addresses captured comments. > >> > >>>>>Specifically this patch replaces pinned_groups and flexible_groups > >>>>>lists of perf_event_context by red-black cpu indexed trees avoiding > >>>>>data structures duplication and introducing possibility to iterate > >>>>>event groups for a specific CPU only. > >>>> > >>>>If you use --per-thread, I take it the overhead is significantly > >>>>lowered? > >>> > >>>Please ask more. > >> > >>IIUC, you're seeing the slowdown when using perf record, correct? > > > >Correct. Specifically in per-process mode - without -a option. > > > >> > >>There's a --per-thread option to ask perf record to not duplicate the > >>event per-cpu. > >> > >>If you use that, what amount of slowdown do you see? > > After applying all three patches: > > - system-wide collection: > > [ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 303.795 MB perf.data (~13272985 samples) ] > 2162.08user 176.24system 0:12.97elapsed 18021%CPU (0avgtext+0avgdata > 1187208maxresident)k > 0inputs+622624outputs (0major+1360285minor)pagefaults 0swaps > > - per-process collection: > > [ perf record: Woken up 5 times to write data ] > [ perf record: Captured and wrote 1.079 MB perf.data (~47134 samples) ] > 2102.39user 153.88system 0:12.78elapsed 17645%CPU (0avgtext+0avgdata > 1187156maxresident)k > 0inputs+2272outputs (0major+1181660minor)pagefaults 0swaps > > Elapsed times look similar. Data file sizes differ significantly.
Interesting. I wonder if that's because we're losing samples due to hammering the rb, or if that's a side-effect of this patch.
Does perf report describe any lost chunks?
For comparison, can you give --per-thread a go prior to these patches being applied?
Thanks, Mark.
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