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 <[email protected]>
Reviewed-by: James Clark <[email protected]>
Cc: Suzuki K Poulose <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Mike Leach <[email protected]>
Cc: Kajol Jain <[email protected]>
Cc: John Garry <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Namhyung Kim <[email protected]>

Author: Leo-Yan

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;