perf: Introduce a new "round of buffers read" pseudo event

In order to provide a more rubust and deterministic reordering
algorithm, we need to know when we reach a point where we just
did a pass through over every counter buffers to read every thing
they had.

This patch introduces a new PERF_RECORD_FINISHED_ROUND pseudo event
that only consist in an event header and doesn't need to contain
anything.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>

tools/perf/builtin-record.c

@@ -494,6 +494,29 @@ static void event__synthesize_guest_os(struct machine *machine, void *data)
 		       " relocation symbol.\n", machine->pid);
 }
 
+static struct perf_event_header finished_round_event = {
+	.size = sizeof(struct perf_event_header),
+	.type = PERF_RECORD_FINISHED_ROUND,
+};
+
+static void mmap_read_all(void)
+{
+	int i, counter, thread;
+
+	for (i = 0; i < nr_cpu; i++) {
+		for (counter = 0; counter < nr_counters; counter++) {
+			for (thread = 0; thread < thread_num; thread++) {
+				if (mmap_array[i][counter][thread].base)
+					mmap_read(&mmap_array[i][counter][thread]);
+			}
+
+		}
+	}
+
+	if (perf_header__has_feat(&session->header, HEADER_TRACE_INFO))
+		write_output(&finished_round_event, sizeof(finished_round_event));
+}
+
 static int __cmd_record(int argc, const char **argv)
 {
 	int i, counter;
@@ -726,16 +749,7 @@ static int __cmd_record(int argc, const char **argv)
 		int hits = samples;
 		int thread;
 
-		for (i = 0; i < nr_cpu; i++) {
-			for (counter = 0; counter < nr_counters; counter++) {
-				for (thread = 0;
-					thread < thread_num; thread++) {
-					if (mmap_array[i][counter][thread].base)
-						mmap_read(&mmap_array[i][counter][thread]);
-				}
-
-			}
-		}
+		mmap_read_all();
 
 		if (hits == samples) {
 			if (done)

tools/perf/util/event.h

@@ -84,11 +84,12 @@ struct build_id_event {
 	char			 filename[];
 };
 
-enum perf_header_event_type { /* above any possible kernel type */
+enum perf_user_event_type { /* above any possible kernel type */
 	PERF_RECORD_HEADER_ATTR			= 64,
 	PERF_RECORD_HEADER_EVENT_TYPE		= 65,
 	PERF_RECORD_HEADER_TRACING_DATA		= 66,
 	PERF_RECORD_HEADER_BUILD_ID		= 67,
+	PERF_RECORD_FINISHED_ROUND		= 68,
 	PERF_RECORD_HEADER_MAX
 };