linux-kernel - [PATCH v2 2/5] perf x86/topdown: Fix topdown leader sampling test error on hybrid

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Message-ID: <20250307023906.1135613-2-irogers@google.com>
Date: Thu,  6 Mar 2025 18:39:03 -0800
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>, 
	Dominique Martinet <asmadeus@...ewreck.org>, Andi Kleen <ak@...ux.intel.com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Dapeng Mi <dapeng1.mi@...ux.intel.com>, Thomas Falcon <thomas.falcon@...el.com>
Subject: [PATCH v2 2/5] perf x86/topdown: Fix topdown leader sampling test
 error on hybrid

From: Dapeng Mi <dapeng1.mi@...ux.intel.com>

When running topdown leader smapling test on Intel hybrid platforms,
such as LNL/ARL, we see the below error.

Topdown leader sampling test
Topdown leader sampling [Failed topdown events not reordered correctly]

It indciates the below command fails.

perf record -o "${perfdata}" -e "{instructions,slots,topdown-retiring}:S" true

The root cause is that perf tool creats a perf event for each PMU type
if it can create.

As for this command, there would be 5 perf events created,
cpu_atom/instructions/,cpu_atom/topdown_retiring/,
cpu_core/slots/,cpu_core/instructions/,cpu_core/topdown-retiring/

For these 5 events, the 2 cpu_atom events are in a group and the other 3
cpu_core events are in another group.

When arch_topdown_sample_read() traverses all these 5 events, events
cpu_atom/instructions/ and cpu_core/slots/ don't have a same group
leade, and then return false directly and lead to cpu_core/slots/ event
is used to sample and this is not allowed by PMU driver.

It's a overkill to return false directly if "evsel->core.leader !=
 leader->core.leader" since there could be multiple groups in the event
list.

Just "continue" instead of "return false" to fix this issue.

Fixes: 1e53e9d1787b ("perf x86/topdown: Correct leader selection with sample_read enabled")
Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
Tested-by: Thomas Falcon <thomas.falcon@...el.com>
Tested-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/arch/x86/util/topdown.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/arch/x86/util/topdown.c b/tools/perf/arch/x86/util/topdown.c
index f63747d0abdf..d1c654839049 100644
--- a/tools/perf/arch/x86/util/topdown.c
+++ b/tools/perf/arch/x86/util/topdown.c
@@ -81,7 +81,7 @@ bool arch_topdown_sample_read(struct evsel *leader)
 	 */
 	evlist__for_each_entry(leader->evlist, evsel) {
 		if (evsel->core.leader != leader->core.leader)
-			return false;
+			continue;
 		if (evsel != leader && arch_is_topdown_metrics(evsel))
 			return true;
 	}
-- 
2.49.0.rc0.332.g42c0ae87b1-goog