linux-kernel - Re: [PATCH RFC 2/9] perf metrics: Don't iter sys metrics if we already found a CPU match

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Date:   Fri, 30 Jun 2023 10:41:02 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     John Garry <john.g.garry@...cle.com>
Cc:     acme@...nel.org, namhyung@...nel.org, jolsa@...nel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        renyu.zj@...ux.alibaba.com, shangxiaojing@...wei.com,
        zhangshaokun@...ilicon.com, qiangqing.zhang@....com,
        kjain@...ux.ibm.com, kan.liang@...ux.intel.com
Subject: Re: [PATCH RFC 2/9] perf metrics: Don't iter sys metrics if we
 already found a CPU match

On Wed, Jun 28, 2023 at 3:30 AM John Garry <john.g.garry@...cle.com> wrote:
>
> In metricgroup__add_metric() we still iter the sys metrics if we already
> found a match from the CPU table, which is pretty pointless, so don't
> bother.
>
> Signed-off-by: John Garry <john.g.garry@...cle.com>
> ---
>  tools/perf/util/metricgroup.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
> index 4389ccd29fe7..8d2ac2513530 100644
> --- a/tools/perf/util/metricgroup.c
> +++ b/tools/perf/util/metricgroup.c
> @@ -1261,6 +1261,12 @@ static int metricgroup__add_metric(const char *pmu, const char *metric_name, con
>
>                 has_match = data.has_match;
>         }
> +
> +       if (has_match) {
> +               ret = 0;
> +               goto out;
> +       }
> +

I think this can just be:

if (!has_match)

However, I'm not sure I agree with the intent of the change. We may
have a metric like IPC and want it to apply to all types of CPU, GPU,
etc. If we short-cut here then that won't be possible.

Thanks,
Ian
>         {
>                 struct metricgroup_iter_data data = {
>                         .fn = metricgroup__add_metric_sys_event_iter,
> @@ -1279,6 +1285,7 @@ static int metricgroup__add_metric(const char *pmu, const char *metric_name, con
>
>                 pmu_for_each_sys_metric(metricgroup__sys_event_iter, &data);
>         }
> +
>         /* End of pmu events. */
>         if (!has_match)
>                 ret = -EINVAL;
> --
> 2.35.3
>