linux-kernel - [PATCH v2 2/2] perf mem: Warn if memory events are not supported on all CPUs

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Message-Id: <20240706152035.86983-3-leo.yan@arm.com>
Date: Sat,  6 Jul 2024 16:20:35 +0100
From: Leo Yan <leo.yan@....com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Namhyung Kim <namhyung@...nel.org>,
	James Clark <james.clark@...aro.org>,
	John Garry <john.g.garry@...cle.com>,
	Will Deacon <will@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Jiri Olsa <jolsa@...nel.org>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Mike Leach <mike.leach@...aro.org>,
	Kajol Jain <kjain@...ux.ibm.com>,
	coresight@...ts.linaro.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Leo Yan <leo.yan@....com>,
	James Clark <james.clark@....com>
Subject: [PATCH v2 2/2] perf mem: Warn if memory events are not supported on all CPUs

It is possible that memory events are not supported on all CPUs.

Prints a warning by dumping the enabled CPU maps in this case.

Signed-off-by: Leo Yan <leo.yan@....com>
Reviewed-by: James Clark <james.clark@....com>
---
 tools/perf/util/mem-events.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tools/perf/util/mem-events.c b/tools/perf/util/mem-events.c
index 6dda47bb774f..8aff2ca8bbd5 100644
--- a/tools/perf/util/mem-events.c
+++ b/tools/perf/util/mem-events.c
@@ -8,6 +8,7 @@
 #include <unistd.h>
 #include <api/fs/fs.h>
 #include <linux/kernel.h>
+#include "cpumap.h"
 #include "map_symbol.h"
 #include "mem-events.h"
 #include "mem-info.h"
@@ -242,6 +243,7 @@ int perf_mem_events__record_args(const char **rec_argv, int *argv_nr)
 	int i = *argv_nr;
 	const char *s;
 	char *copy;
+	struct perf_cpu_map *cpu_map = NULL;
 
 	while ((pmu = perf_pmus__scan_mem(pmu)) != NULL) {
 		for (int j = 0; j < PERF_MEM_EVENTS__MAX; j++) {
@@ -266,7 +268,19 @@ int perf_mem_events__record_args(const char **rec_argv, int *argv_nr)
 
 			rec_argv[i++] = "-e";
 			rec_argv[i++] = copy;
+
+			cpu_map = perf_cpu_map__merge(cpu_map, pmu->cpus);
+		}
+	}
+
+	if (cpu_map) {
+		if (!perf_cpu_map__equal(cpu_map, cpu_map__online())) {
+			char buf[200];
+
+			cpu_map__snprint(cpu_map, buf, sizeof(buf));
+			pr_warning("Memory events are enabled on a subset of CPUs: %s\n", buf);
 		}
+		perf_cpu_map__put(cpu_map);
 	}
 
 	*argv_nr = i;
-- 
2.34.1