linux-kernel - Re: [PATCH] perf pmu: Fix perf stat output with correct scale and unit

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Date:   Wed, 20 Sep 2023 09:02:23 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Wyes Karny <wyes.karny@....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,
        kan.liang@...ux.intel.com, james.clark@....com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        sandipan.das@....com, ravi.bangoria@....com
Subject: Re: [PATCH] perf pmu: Fix perf stat output with correct scale and unit

On Wed, Sep 20, 2023 at 5:24 AM Wyes Karny <wyes.karny@....com> wrote:
>
> The perf_pmu__parse_* functions for the sysfs files of pmu event’s
> scale, unit, per-pkg and snapshot were updated in commit 7b723dbb96e8
> ("perf pmu: Be lazy about loading event info files from sysfs").
> However, the paths for these sysfs files were incorrect. This resulted
> in perf stat reporting values with wrong scaling and missing units. This
> is fixed by correcting the paths for these sysfs files.
>
> Before this fix:
>
>  $sudo perf stat -e power/energy-pkg/ -- sleep 2
>
>  Performance counter stats for 'system wide':
>
>    351,217,188,864      power/energy-pkg/
>
>           2.004127961 seconds time elapsed
>
> After this fix:
>
>  $sudo perf stat -e power/energy-pkg/ -- sleep 2
>
>  Performance counter stats for 'system wide':
>
>              80.58 Joules power/energy-pkg/
>
>              2.004009749 seconds time elapsed
>
> Fixes: 7b723dbb96e8 ("perf pmu: Be lazy about loading event info files from sysfs")
> Signed-off-by: Wyes Karny <wyes.karny@....com>

Reviewed-by: Ian Rogers <irogers@...gle.com>

Thanks!
Ian

> ---
>  tools/perf/util/pmu.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index 0d81c059c91c..93feee29d054 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -295,7 +295,7 @@ static int perf_pmu__parse_scale(struct perf_pmu *pmu, struct perf_pmu_alias *al
>         len = perf_pmu__event_source_devices_scnprintf(path, sizeof(path));
>         if (!len)
>                 return 0;
> -       scnprintf(path + len, sizeof(path) - len, "%s/%s.scale", pmu->name, alias->name);
> +       scnprintf(path + len, sizeof(path) - len, "%s/events/%s.scale", pmu->name, alias->name);
>
>         fd = open(path, O_RDONLY);
>         if (fd == -1)
> @@ -330,7 +330,7 @@ static int perf_pmu__parse_unit(struct perf_pmu *pmu, struct perf_pmu_alias *ali
>         len = perf_pmu__event_source_devices_scnprintf(path, sizeof(path));
>         if (!len)
>                 return 0;
> -       scnprintf(path + len, sizeof(path) - len, "%s/%s.unit", pmu->name, alias->name);
> +       scnprintf(path + len, sizeof(path) - len, "%s/events/%s.unit", pmu->name, alias->name);
>
>         fd = open(path, O_RDONLY);
>         if (fd == -1)
> @@ -364,7 +364,7 @@ perf_pmu__parse_per_pkg(struct perf_pmu *pmu, struct perf_pmu_alias *alias)
>         len = perf_pmu__event_source_devices_scnprintf(path, sizeof(path));
>         if (!len)
>                 return 0;
> -       scnprintf(path + len, sizeof(path) - len, "%s/%s.per-pkg", pmu->name, alias->name);
> +       scnprintf(path + len, sizeof(path) - len, "%s/events/%s.per-pkg", pmu->name, alias->name);
>
>         fd = open(path, O_RDONLY);
>         if (fd == -1)
> @@ -385,7 +385,7 @@ static int perf_pmu__parse_snapshot(struct perf_pmu *pmu, struct perf_pmu_alias
>         len = perf_pmu__event_source_devices_scnprintf(path, sizeof(path));
>         if (!len)
>                 return 0;
> -       scnprintf(path + len, sizeof(path) - len, "%s/%s.snapshot", pmu->name, alias->name);
> +       scnprintf(path + len, sizeof(path) - len, "%s/events/%s.snapshot", pmu->name, alias->name);
>
>         fd = open(path, O_RDONLY);
>         if (fd == -1)
> --
> 2.34.1
>