On Mon, Jun 19, 2017 at 01:46:39PM +0100, Mark Rutland wrote: > 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: > > >>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?
FWIW, I had a go with (an old) perf record on an arm64 system using --per-thread, and I see that no samples are recorded, which seems like a bug. With --per-thread, the slwodown was ~20%, whereas with the defaults it was > 400%. Thanks, Mark.
