linux-kernel - [PATCH 09/12] perf top: Drop samples which are behind more than refresh rate

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Message-Id: <20181119122016.22423-10-jolsa@kernel.org>
Date:   Mon, 19 Nov 2018 13:20:13 +0100
From:   Jiri Olsa <jolsa@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        David Miller <davem@...emloft.net>
Subject: [PATCH 09/12] perf top: Drop samples which are behind more than refresh rate

Dropping samples from processing thread if they get behind the
latest event read from kernel maps. If it gets behind more than
the refresh rate (-d option), dropping the sample.

Link: http://lkml.kernel.org/n/tip-wf56z076006vfs5f5qd28d7n@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/perf/builtin-top.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index ce542cc1e84f..a509d8c0a846 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -833,6 +833,8 @@ perf_top__process_lost_samples(struct perf_top *top,
 	hists->stats.total_lost_samples += event->lost_samples.lost;
 }
 
+static u64 last_timestamp;
+
 static void perf_top__mmap_read_idx(struct perf_top *top, int idx)
 {
 	struct record_opts *opts = &top->record_opts;
@@ -845,14 +847,13 @@ static void perf_top__mmap_read_idx(struct perf_top *top, int idx)
 		return;
 
 	while ((event = perf_mmap__read_event(md)) != NULL) {
-		u64 timestamp = -1ULL;
 		int ret;
 
-		ret = perf_evlist__parse_sample_timestamp(evlist, event, &timestamp);
+		ret = perf_evlist__parse_sample_timestamp(evlist, event, &last_timestamp);
 		if (ret && ret != -1)
 			break;
 
-		ret = ordered_events__queue(top->qe.in, event, timestamp, 0);
+		ret = ordered_events__queue(top->qe.in, event, last_timestamp, 0);
 		if (ret)
 			break;
 
@@ -1084,6 +1085,21 @@ static void *process_thread(void *arg)
 	return NULL;
 }
 
+/*
+ * Allow only 'top->delay_secs' seconds behind samples.
+ */
+static int should_drop(struct ordered_event *qevent, struct perf_top *top)
+{
+	union perf_event *event = qevent->event;
+	u64 delay_timestamp;
+
+	if (event->header.type != PERF_RECORD_SAMPLE)
+		return false;
+
+	delay_timestamp = qevent->timestamp + top->delay_secs * NSEC_PER_SEC;
+	return delay_timestamp < last_timestamp;
+}
+
 static int deliver_event(struct ordered_events *qe,
 			 struct ordered_event *qevent)
 {
@@ -1096,6 +1112,9 @@ static int deliver_event(struct ordered_events *qe,
 	struct machine *machine;
 	int ret = -1;
 
+	if (should_drop(qevent, top))
+		return 0;
+
 	ret = perf_evlist__parse_sample(evlist, event, &sample);
 	if (ret) {
 		pr_err("Can't parse sample, err = %d\n", ret);
-- 
2.17.2