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Subject[PATCH 53/75] perf top: Drop samples which are behind the refresh rate
Date
From: Jiri Olsa <jolsa@kernel.org>

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

Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/n/tip-x533ra5c1pgofvbtsizzuydd@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
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 50ec01eb7f57..234232d538c2 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);
--
2.19.2
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