Messages in this thread | | | From | Namhyung Kim <> | Date | Sat, 14 Nov 2020 09:23:39 +0900 | Subject | Re: [PATCH] perf stat: Use proper cpu for shadow stats |
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On Sat, Nov 14, 2020 at 7:16 AM Jiri Olsa <jolsa@redhat.com> wrote: > > On Fri, Nov 13, 2020 at 02:02:36PM +0900, Namhyung Kim wrote: > > Currently perf stat shows some metrics (like IPC) for defined events. > > But when no aggregation mode is used (-A option), it shows incorrect > > values since it used a value from a different cpu. > > > > Before: > > > > $ perf stat -aA -e cycles,instructions sleep 1 > > > > Performance counter stats for 'system wide': > > > > CPU0 116,057,380 cycles > > CPU1 86,084,722 cycles > > CPU2 99,423,125 cycles > > CPU3 98,272,994 cycles > > CPU0 53,369,217 instructions # 0.46 insn per cycle > > CPU1 33,378,058 instructions # 0.29 insn per cycle > > CPU2 58,150,086 instructions # 0.50 insn per cycle > > CPU3 40,029,703 instructions # 0.34 insn per cycle > > > > 1.001816971 seconds time elapsed > > > > So the IPC for CPU1 should be 0.38 (= 33,378,058 / 86,084,722) > > but it was 0.29 (= 33,378,058 / 116,057,380) and so on. > > > > After: > > > > $ perf stat -aA -e cycles,instructions sleep 1 > > > > Performance counter stats for 'system wide': > > > > CPU0 109,621,384 cycles > > CPU1 159,026,454 cycles > > CPU2 99,460,366 cycles > > CPU3 124,144,142 cycles > > CPU0 44,396,706 instructions # 0.41 insn per cycle > > CPU1 120,195,425 instructions # 0.76 insn per cycle > > CPU2 44,763,978 instructions # 0.45 insn per cycle > > CPU3 69,049,079 instructions # 0.56 insn per cycle > > > > 1.001910444 seconds time elapsed > > > > Reported-by: Sam Xi <xyzsam@google.com> > > Fixes: 44d49a600259 ("perf stat: Support metrics in --per-core/socket mode") > > Signed-off-by: Namhyung Kim <namhyung@kernel.org> > > nice catch! would be great to have test for this > > Acked-by: Jiri Olsa <jolsa@redhat.com>
Thanks! Will add a test later.
Thanks, Namhyung
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