linux-kernel - [PATCH v1 4/4] perf stat-shadow: Display metric-only for 0 counters

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Message-ID: <20250914182900.1960567-5-irogers@google.com>
Date: Sun, 14 Sep 2025 11:29:00 -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>, 
	Chun-Tse Shao <ctshao@...gle.com>, Thomas Falcon <thomas.falcon@...el.com>, 
	Yang Li <yang.lee@...ux.alibaba.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH v1 4/4] perf stat-shadow: Display metric-only for 0 counters

0 counters may occur in hypervisor settings but metric-only output is
always expected. This resolves an issue in the "perf stat STD output
linter" test.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/stat-display.c |  3 +++
 tools/perf/util/stat-shadow.c  | 11 ++++-------
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
index a67b991f4e81..8a72e019e6c7 100644
--- a/tools/perf/util/stat-display.c
+++ b/tools/perf/util/stat-display.c
@@ -944,6 +944,9 @@ static bool should_skip_zero_counter(struct perf_stat_config *config,
 	if (verbose == 0 && counter->skippable && !counter->supported)
 		return true;
 
+	/* Metric only counts won't be displayed but the metric wants to be computed. */
+	if (config->metric_only)
+		return false;
 	/*
 	 * Skip value 0 when enabling --per-thread globally,
 	 * otherwise it will have too many 0 output.
diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c
index abaf6b579bfc..dd3a15b17eb9 100644
--- a/tools/perf/util/stat-shadow.c
+++ b/tools/perf/util/stat-shadow.c
@@ -320,13 +320,10 @@ static void print_instructions(struct perf_stat_config *config,
 	double max_stalled = max(find_stat(evsel, aggr_idx, STAT_STALLED_CYCLES_FRONT),
 				find_stat(evsel, aggr_idx, STAT_STALLED_CYCLES_BACK));
 
-	if (cycles) {
-		print_metric(config, ctxp, METRIC_THRESHOLD_UNKNOWN, "%7.2f ",
-			     "insn per cycle", instructions / cycles);
-	} else {
-		print_metric(config, ctxp, METRIC_THRESHOLD_UNKNOWN, /*fmt=*/NULL,
-			     "insn per cycle", 0);
-	}
+        print_metric(config, ctxp, METRIC_THRESHOLD_UNKNOWN, "%7.2f ",
+                     "insn per cycle",
+                     fpclassify(cycles) == FP_ZERO ? 0 : instructions / cycles);
+
 	if (max_stalled && instructions) {
 		if (out->new_line)
 			out->new_line(config, ctxp);
-- 
2.51.0.384.g4c02a37b29-goog