linux-kernel - [PATCH RFC] perf: Start 'top' display thread earlier.

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Message-Id: <20181030.223003.2242527041807905962.davem@davemloft.net>
Date:   Tue, 30 Oct 2018 22:30:03 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     acme@...nel.org
CC:     linux-kernel@...r.kernel.org
Subject: [PATCH RFC] perf: Start 'top' display thread earlier.

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@...emloft.net>

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index d21d875..e7a78ce 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1134,11 +1125,6 @@ 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 +1142,11 @@ 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;