linux-kernel - Re: [PATCH 14/15] perf stat: Rename "aggregate-number" to "cpu-count" in JSON

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Date:   Thu, 24 Nov 2022 23:50:58 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org,
        Kan Liang <kan.liang@...ux.intel.com>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        James Clark <james.clark@....com>,
        Athira Jajeev <atrajeev@...ux.vnet.ibm.com>
Subject: Re: [PATCH 14/15] perf stat: Rename "aggregate-number" to "cpu-count"
 in JSON

Hi Ian,

On Wed, Nov 23, 2022 at 3:31 PM Ian Rogers <irogers@...gle.com> wrote:
>
> On Wed, Nov 23, 2022 at 10:02 AM Namhyung Kim <namhyung@...nel.org> wrote:
> >
> > As the JSON output has been broken for a little while, I guess there are
> > not many users.  Let's rename the field to more intuitive one. :)
>
> I'm not sure cpu-count is accurate. For example, an uncore counter in
> a dual socket machine may have a CPU mask of "0, 36", ie one event per
> socket. The aggregate-number in this case I believe is 2.

You're right.  In case of uncore events, it can be confusing.  But in some
sense it could be thought as cpu count as well since it aggregates the
result from two cpus anyway. :)

Note that the aggregate-number (or cpu-count) is only printed if users
requested one of aggregation options like --per-socket or --per-core.
In your example, then it could print 1 for each socket.

But I think uncore events are different from core events, and hopefully
they have separate instances for different sockets or something already.
That means it doesn't need to use those aggregation options for them.

Also the CSV output uses "cpus" for the same information.  It'd be nice
we could have consistency.

Thanks,
Namhyung