[tip:perf/core] perf top: Display slow reader warning when droping samples

[tip-bot for Jiri Olsa]

Commit-ID:  ffec48b734491d7c687c5cb430bffdbb9c56824e
Gitweb:     https://git.kernel.org/tip/ffec48b734491d7c687c5cb430bffdbb9c56824e
Author:     Jiri Olsa <jolsa@xxxxxxxxxx>
AuthorDate: Mon, 19 Nov 2018 11:12:01 +0100
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Thu, 6 Dec 2018 14:12:34 -0300

perf top: Display slow reader warning when droping samples

Currently we display the "Too slow to read ring buffer.." helpline only
in the slow reader thread. This patch triggers it also when the
processing thread drops samples, because it has the same reason, which
is too many data on input.

Acked-by: David S. Miller <davem@xxxxxxxxxxxxx>
Acked-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/n/tip-bnev2mloavyurmgchcr3o24o@xxxxxxxxxxxxxx
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 tools/perf/builtin-top.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 9166f6087e3f..f22c531be366 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -571,7 +571,7 @@ static void perf_top__sort_new_samples(void *arg)
 	hists__collapse_resort(hists, NULL);
 	perf_evsel__output_resort(evsel, NULL);
 
-	if (t->lost)
+	if (t->lost || t->drop)
 		pr_warning("Too slow to read ring buffer (change period (-c/-F) or limit CPUs (-C)\n");
 
 	perf_top__reset_sample_counters(t);