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Subject[PATCH 4.19 086/114] perf stat: Reset previous counts on repeat with interval
Date
From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

[ Upstream commit b63fd11cced17fcb8e133def29001b0f6aaa5e06 ]

When using 'perf stat' with repeat and interval option, it shows wrong
values for events.

The wrong values will be shown for the first interval on the second and
subsequent repetitions.

Without the fix:

# perf stat -r 3 -I 2000 -e faults -e sched:sched_switch -a sleep 5

2.000282489 53 faults
2.000282489 513 sched:sched_switch
4.005478208 3,721 faults
4.005478208 2,666 sched:sched_switch
5.025470933 395 faults
5.025470933 1,307 sched:sched_switch
2.009602825 1,84,46,74,40,73,70,95,47,520 faults <------
2.009602825 1,84,46,74,40,73,70,95,49,568 sched:sched_switch <------
4.019612206 4,730 faults
4.019612206 2,746 sched:sched_switch
5.039615484 3,953 faults
5.039615484 1,496 sched:sched_switch
2.000274620 1,84,46,74,40,73,70,95,47,520 faults <------
2.000274620 1,84,46,74,40,73,70,95,47,520 sched:sched_switch <------
4.000480342 4,282 faults
4.000480342 2,303 sched:sched_switch
5.000916811 1,322 faults
5.000916811 1,064 sched:sched_switch
#

prev_raw_counts is allocated when using intervals. This is used when
calculating the difference in the counts of events when using interval.

The current counts are stored in prev_raw_counts to calculate the
differences in the next iteration.

On the first interval of the second and subsequent repetitions,
prev_raw_counts would be the values stored in the last interval of the
previous repetitions, while the current counts will only be for the
first interval of the current repetition.

Hence there is a possibility of events showing up as big number.

Fix this by resetting prev_raw_counts whenever perf stat repeats the
command.

With the fix:

# perf stat -r 3 -I 2000 -e faults -e sched:sched_switch -a sleep 5

2.019349347 2,597 faults
2.019349347 2,753 sched:sched_switch
4.019577372 3,098 faults
4.019577372 2,532 sched:sched_switch
5.019415481 1,879 faults
5.019415481 1,356 sched:sched_switch
2.000178813 8,468 faults
2.000178813 2,254 sched:sched_switch
4.000404621 7,440 faults
4.000404621 1,266 sched:sched_switch
5.040196079 2,458 faults
5.040196079 556 sched:sched_switch
2.000191939 6,870 faults
2.000191939 1,170 sched:sched_switch
4.000414103 541 faults
4.000414103 902 sched:sched_switch
5.000809863 450 faults
5.000809863 364 sched:sched_switch
#

Committer notes:

This was broken since the cset introducing the --interval feature, i.e.
--repeat + --interval wasn't tested at that point, add the Fixes tag so
that automatic scripts can pick this up.

Fixes: 13370a9b5bb8 ("perf stat: Add interval printing")
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: stable@vger.kernel.org # v3.9+
Link: http://lore.kernel.org/lkml/20190904094738.9558-2-srikar@linux.vnet.ibm.com
[ Fixed up conflicts with libperf, i.e. some perf_{evsel,evlist} lost the 'perf' prefix ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/perf/builtin-stat.c | 3 +++
tools/perf/util/stat.c | 17 +++++++++++++++++
tools/perf/util/stat.h | 1 +
3 files changed, 21 insertions(+)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 11650910e089a..6aae10ff954c7 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -3090,6 +3090,9 @@ int cmd_stat(int argc, const char **argv)
fprintf(output, "[ perf stat: executing run #%d ... ]\n",
run_idx + 1);

+ if (run_idx != 0)
+ perf_evlist__reset_prev_raw_counts(evsel_list);
+
status = run_perf_stat(argc, argv, run_idx);
if (forever && status != -1 && !interval) {
print_counters(NULL, argc, argv);
diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
index a0061e0b0fade..6917ba8a00240 100644
--- a/tools/perf/util/stat.c
+++ b/tools/perf/util/stat.c
@@ -154,6 +154,15 @@ static void perf_evsel__free_prev_raw_counts(struct perf_evsel *evsel)
evsel->prev_raw_counts = NULL;
}

+static void perf_evsel__reset_prev_raw_counts(struct perf_evsel *evsel)
+{
+ if (evsel->prev_raw_counts) {
+ evsel->prev_raw_counts->aggr.val = 0;
+ evsel->prev_raw_counts->aggr.ena = 0;
+ evsel->prev_raw_counts->aggr.run = 0;
+ }
+}
+
static int perf_evsel__alloc_stats(struct perf_evsel *evsel, bool alloc_raw)
{
int ncpus = perf_evsel__nr_cpus(evsel);
@@ -204,6 +213,14 @@ void perf_evlist__reset_stats(struct perf_evlist *evlist)
}
}

+void perf_evlist__reset_prev_raw_counts(struct perf_evlist *evlist)
+{
+ struct perf_evsel *evsel;
+
+ evlist__for_each_entry(evlist, evsel)
+ perf_evsel__reset_prev_raw_counts(evsel);
+}
+
static void zero_per_pkg(struct perf_evsel *counter)
{
if (counter->per_pkg_mask)
diff --git a/tools/perf/util/stat.h b/tools/perf/util/stat.h
index 36efb986f7fc6..e19abb1635c4e 100644
--- a/tools/perf/util/stat.h
+++ b/tools/perf/util/stat.h
@@ -158,6 +158,7 @@ void perf_stat__collect_metric_expr(struct perf_evlist *);
int perf_evlist__alloc_stats(struct perf_evlist *evlist, bool alloc_raw);
void perf_evlist__free_stats(struct perf_evlist *evlist);
void perf_evlist__reset_stats(struct perf_evlist *evlist);
+void perf_evlist__reset_prev_raw_counts(struct perf_evlist *evlist);

int perf_stat_process_counter(struct perf_stat_config *config,
struct perf_evsel *counter);
--
2.20.1


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