linux-kernel - Re: [PATCH V2] perf top: Use evsel's cpus to replace user_requested

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Date:   Wed, 13 Dec 2023 13:54:17 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     "Liang, Kan" <kan.liang@...ux.intel.com>, acme@...nel.org,
        mark.rutland@....com, maz@...nel.org, marcan@...can.st,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH V2] perf top: Use evsel's cpus to replace user_requested_cpus

On Wed, Dec 13, 2023 at 9:42 AM Ian Rogers <irogers@...gle.com> wrote:
>
> On Wed, Dec 13, 2023 at 7:45 AM Liang, Kan <kan.liang@...ux.intel.com> wrote:
> >
> >
> >
> > On 2023-12-12 8:06 p.m., Namhyung Kim wrote:
> > > On Tue, Dec 12, 2023 at 2:12 PM Ian Rogers <irogers@...gle.com> wrote:

> > >> If my memory serves there was a patch where perf top was showing >1
> > >> event. It would be nice here to do some kind of hybrid merging rather
> > >> than having to view each PMU's top separately.
> >
> > The current perf top doesn't merge when there are >1 event.
> > sudo ./perf top -e "cycles,instructions"
> >
> > Available samples
> > 2K cycles
> >
> > 2K instructions
> >
> > For now, I think we may just append a PMU name to distinguish the hybrid
> > case.
> >
> > We may implement the merging feature which impacts both hybrid and
> > non-hybrid cases later separately.
> >
> > >
> > > Using event groups, but I noticed you removed the --group option.
> > > Maybe perf top can just use `{ ... }` notation for explicit grouping,
> > > but it might be implicit like in the hybrid case.
> > >
> >
> > Yes, if the events are from different PMUs, the perf tool will
> > implicitly de-group the hybrid events. "{ ... }" may not help here.
>
> I think grouping may have been the situation where I saw >1 event
> displayed but I agree with Kan, we implicitly de-group events on
> different PMUs so it won't help here.

The --group option was implemented in perf report which means
it doesn't matter if events are in different PMUs.  It's just to display
the results together.

Thanks,
Namhyung