perf mem: Support new memory event PERF_MEM_EVENTS__LOAD_STORE

On the architectures with perf memory profiling, two types of hardware
events have been supported: load and store; if want to profile memory
for both load and store operations, the tool will use these two events
at the same time, the usage is:

  # perf mem record -t load,store -- uname

But this cannot be applied for AUX tracing event, the same PMU event can
be used to only trace memory load, or only memory store, or trace for
both memory load and store.

This patch introduces a new event PERF_MEM_EVENTS__LOAD_STORE, which is
used to support the event which can record both memory load and store
operations.

When user specifies memory operation type as 'load,store', or doesn't
set type so use 'load,store' as default, if the arch supports the event
PERF_MEM_EVENTS__LOAD_STORE, the tool will convert the required
operations to this single event; otherwise, if the arch doesn't support
PERF_MEM_EVENTS__LOAD_STORE, the tool rolls back to enable both events
PERF_MEM_EVENTS__LOAD and PERF_MEM_EVENTS__STORE, which keeps the same
behaviour with before.
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Link: https://lore.kernel.org/r/20201106094853.21082-4-leo.yan@linaro.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-mem.c

@@ -87,14 +87,26 @@ static int __cmd_record(int argc, const char **argv, struct perf_mem *mem)
 
 	rec_argv[i++] = "record";
 
-	if (mem->operation & MEM_OPERATION_LOAD) {
-		e = perf_mem_events__ptr(PERF_MEM_EVENTS__LOAD);
-		e->record = true;
-	}
+	e = perf_mem_events__ptr(PERF_MEM_EVENTS__LOAD_STORE);
 
-	if (mem->operation & MEM_OPERATION_STORE) {
-		e = perf_mem_events__ptr(PERF_MEM_EVENTS__STORE);
+	/*
+	 * The load and store operations are required, use the event
+	 * PERF_MEM_EVENTS__LOAD_STORE if it is supported.
+	 */
+	if (e->tag &&
+	    (mem->operation & MEM_OPERATION_LOAD) &&
+	    (mem->operation & MEM_OPERATION_STORE)) {
 		e->record = true;
+	} else {
+		if (mem->operation & MEM_OPERATION_LOAD) {
+			e = perf_mem_events__ptr(PERF_MEM_EVENTS__LOAD);
+			e->record = true;
+		}
+
+		if (mem->operation & MEM_OPERATION_STORE) {
+			e = perf_mem_events__ptr(PERF_MEM_EVENTS__STORE);
+			e->record = true;
+		}
 	}
 
 	e = perf_mem_events__ptr(PERF_MEM_EVENTS__LOAD);

tools/perf/util/mem-events.c

@@ -20,6 +20,7 @@ unsigned int perf_mem_events__loads_ldlat = 30;
 static struct perf_mem_event perf_mem_events[PERF_MEM_EVENTS__MAX] = {
 	E("ldlat-loads",	"cpu/mem-loads,ldlat=%u/P",	"cpu/events/mem-loads"),
 	E("ldlat-stores",	"cpu/mem-stores/P",		"cpu/events/mem-stores"),
+	E(NULL,			NULL,				NULL),
 };
 #undef E
 
@@ -75,6 +76,9 @@ int perf_mem_events__parse(const char *str)
 		for (j = 0; j < PERF_MEM_EVENTS__MAX; j++) {
 			struct perf_mem_event *e = perf_mem_events__ptr(j);
 
+			if (!e->tag)
+				continue;
+
 			if (strstr(e->tag, tok))
 				e->record = found = true;
 		}
@@ -105,6 +109,13 @@ int perf_mem_events__init(void)
 		struct perf_mem_event *e = perf_mem_events__ptr(j);
 		struct stat st;
 
+		/*
+		 * If the event entry isn't valid, skip initialization
+		 * and "e->supported" will keep false.
+		 */
+		if (!e->tag)
+			continue;
+
 		scnprintf(path, PATH_MAX, "%s/devices/%s",
 			  mnt, e->sysfs_name);
 
@@ -123,7 +134,7 @@ void perf_mem_events__list(void)
 		struct perf_mem_event *e = perf_mem_events__ptr(j);
 
 		fprintf(stderr, "%-13s%-*s%s\n",
-			e->tag,
+			e->tag ?: "",
 			verbose > 0 ? 25 : 0,
 			verbose > 0 ? perf_mem_events__name(j) : "",
 			e->supported ? ": available" : "");

tools/perf/util/mem-events.h

@@ -28,6 +28,7 @@ struct mem_info {
 enum {
 	PERF_MEM_EVENTS__LOAD,
 	PERF_MEM_EVENTS__STORE,
+	PERF_MEM_EVENTS__LOAD_STORE,
 	PERF_MEM_EVENTS__MAX,
 };