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

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Date:   Wed, 20 Sep 2023 12:23:49 +0000
From:   Wyes Karny <wyes.karny@....com>
To:     <irogers@...gle.com>, <peterz@...radead.org>, <mingo@...hat.com>,
        <acme@...nel.org>
CC:     <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>, Wyes Karny <wyes.karny@....com>
Subject: [PATCH] perf pmu: Fix perf stat output with correct scale and unit

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>
---
 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