perf top: Start display thread earlier

davem330 · acmel · commit ff27a06af6ff · 2018-10-31T10:10:11.000-03:00
If events are coming in at a rate such that the event processing thread can barely keep up, our initial run of the event ring will almost never terminate and this delays the starting of the display thread. The screen basically stays black until the event thread can get out of it's endless loop. Therefore, start the display thread before we start processing the ring buffer. This also make sure that we always have the user requested real time setting engaged when processing the ring. Signed-off-by: David S. Miller <davem@davemloft.net> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Kan Liang <kan.liang@linux.intel.com> Cc: Namhyung Kim <namhyung@kernel.org> Link: http://lkml.kernel.org/r/20181030.223003.2242527041807905962.davem@davemloft.net Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
@@ -1134,11 +1134,6 @@ static int __cmd_top(struct perf_top *top)
         if (!target__none(&opts->target))
                 perf_evlist__enable(top->evlist);
 
-	/* Wait for a minimal set of events before starting the snapshot */
-	perf_evlist__poll(top->evlist, 100);
-
-	perf_top__mmap_read(top);
-
 	ret = -1;
 	if (pthread_create(&thread, NULL, (use_browser > 0 ? display_thread_tui :
 							    display_thread), top)) {
@@ -1156,6 +1151,11 @@ static int __cmd_top(struct perf_top *top)
 		}
 	}
 
+	/* Wait for a minimal set of events before starting the snapshot */
+	perf_evlist__poll(top->evlist, 100);
+
+	perf_top__mmap_read(top);
+
 	while (!done) {
 		u64 hits = top->samples;
 
