linux-kernel - Re: [PATCH] perf pmu: Filter out search events table of software pmu in perf_pmu_

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Date:   Mon, 16 Oct 2023 14:04:30 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Yang Jihong <yangjihong1@...wei.com>
Cc:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...nel.org, namhyung@...nel.org, adrian.hunter@...el.com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf pmu: Filter out search events table of software pmu
 in perf_pmu__lookup()

On Mon, Oct 16, 2023 at 2:35 AM Yang Jihong <yangjihong1@...wei.com> wrote:
>
> For software pmu, the events_table is empty, reducing unnecessary search.
>
> Signed-off-by: Yang Jihong <yangjihong1@...wei.com>

I'd rather that all PMUs behaved in the same manner without ifs that
will catch people/me out later on. perf_pmu__is_software tells whether
the kernel context is software and therefore whether events can be
grouped with a hardware event. As a test for whether json exists or
not I'd rather stick to values derived from the json.

Thanks,
Ian

> ---
>  tools/perf/util/pmu.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index 6428e2648289..59c8394a4efa 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -1033,7 +1033,8 @@ struct perf_pmu *perf_pmu__lookup(struct list_head *pmus, int dirfd, const char
>                 pmu->id = pmu_id(name);
>         pmu->max_precise = pmu_max_precise(dirfd, pmu);
>         pmu->alias_name = pmu_find_alias_name(pmu, dirfd);
> -       pmu->events_table = perf_pmu__find_events_table(pmu);
> +       if (!perf_pmu__is_software(pmu))
> +               pmu->events_table = perf_pmu__find_events_table(pmu);
>         pmu_add_sys_aliases(pmu);
>         list_add_tail(&pmu->list, pmus);
>
> --
> 2.34.1
>