perf record: Store PERF_RECORD_FINISHED_ROUND only for nonempty rounds

Currently we store PERF_RECORD_FINISHED_ROUND event each time
we go throught mmap buffers no matter if it contains any data,
which is useless.

Forcing the PERF_RECORD_FINISHED_ROUND event to be stored any
time we finished the round AND wrote at least one event.

Signed-off-by: Jiri Olsa <[email protected]>
Acked-by: Adrian Hunter <[email protected]>
Acked-by: David Ahern <[email protected]>
Cc: Corey Ashford <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jean Pihet <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 7 insertions, 1 deletions

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 4a1a54265b04..4869050e7194 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -238,6 +238,7 @@ static struct perf_event_header finished_round_event = {
 
 static int record__mmap_read_all(struct record *rec)
 {
+	u64 bytes_written = rec->bytes_written;
 	int i;
 	int rc = 0;
 
@@ -250,7 +251,12 @@ static int record__mmap_read_all(struct record *rec)
 		}
 	}
 
-	rc = record__write(rec, &finished_round_event, sizeof(finished_round_event));
+	/*
+	 * Mark the round finished in case we wrote
+	 * at least one event.
+	 */
+	if (bytes_written != rec->bytes_written)
+		rc = record__write(rec, &finished_round_event, sizeof(finished_round_event));
 
 out:
 	return rc;