linux-kernel - [PATCH v1] perf tool_pmu: Fix aggregation on duration

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Message-ID: <20250423050358.94310-1-irogers@google.com>
Date: Tue, 22 Apr 2025 22:03:58 -0700
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, James Clark <james.clark@...aro.org>, 
	Thomas Richter <tmricht@...ux.ibm.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Cc: Stephane Eranian <eranian@...gle.com>
Subject: [PATCH v1] perf tool_pmu: Fix aggregation on duration_time

evsel__count_has_error fails counters when the enabled or running time
are 0. The duration_time event reads 0 when the cpu_map_idx != 0 to
avoid aggregating time over CPUs. Change the enable and running time
to always have a ratio of 100% so that evsel__count_has_error won't
fail.

Before:
```
$ sudo /tmp/perf/perf stat --per-core -a -M UNCORE_FREQ sleep 1

 Performance counter stats for 'system wide':

S0-D0-C0              1      2,615,819,485      UNC_CLOCK.SOCKET                 #     2.61 UNCORE_FREQ
S0-D0-C0              2      <not counted>      duration_time

       1.002111784 seconds time elapsed
```

After:
```
$ perf stat --per-core -a -M UNCORE_FREQ sleep 1

 Performance counter stats for 'system wide':

S0-D0-C0              1        758,160,296      UNC_CLOCK.SOCKET                 #     0.76 UNCORE_FREQ
S0-D0-C0              2      1,003,438,246      duration_time

       1.002486017 seconds time elapsed
```

Note: the metric reads the value a different way and isn't impacted.

Reported-by: Stephane Eranian <eranian@...gle.com>
Fixes: 240505b2d0ad ("perf tool_pmu: Factor tool events into their own PMU")
Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/tool_pmu.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/tool_pmu.c b/tools/perf/util/tool_pmu.c
index 97b327d1ce4a..727a10e3f990 100644
--- a/tools/perf/util/tool_pmu.c
+++ b/tools/perf/util/tool_pmu.c
@@ -486,8 +486,14 @@ int evsel__tool_pmu_read(struct evsel *evsel, int cpu_map_idx, int thread)
 		delta_start *= 1000000000 / ticks_per_sec;
 	}
 	count->val    = delta_start;
-	count->ena    = count->run = delta_start;
 	count->lost   = 0;
+	/*
+	 * The values of enabled and running must make a ratio of 100%. The
+	 * exact values don't matter as long as they are non-zero to avoid
+	 * issues with evsel__count_has_error.
+	 */
+	count->ena++;
+	count->run++;
 	return 0;
 }
 
-- 
2.49.0.805.g082f7c87e0-goog