On Sat, Nov 14, 2020 at 7:16 AM Jiri Olsa <jo...@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 <xyz...@google.com>
> > Fixes: 44d49a600259 ("perf stat: Support metrics in --per-core/socket mode")
> > Signed-off-by: Namhyung Kim <namhy...@kernel.org>
>
> nice catch! would be great to have test for this
>
> Acked-by: Jiri Olsa <jo...@redhat.com>
Thanks! Will add a test later.
Thanks,
Namhyung
