[PATCH v6 1/5] perf stat: Fix wrong per-thread runtime stat for interval mode

Jin Yao
2020-05-20T04:29:51Z

root@kbl-ppc:~# perf stat --per-thread -e cycles,instructions -I1000 --interval-count 2
1.004171683 perf-3696 8,747,311 cycles
...
1.004171683 perf-3696 691,730 instructions # 0.08 insn per cycle
...
2.006490373 perf-3696 1,749,936 cycles
...
2.006490373 perf-3696 1,484,582 instructions # 0.28 insn per cycle
...

Let's see interval 2.006490373

perf-3696 1,749,936 cycles
perf-3696 1,484,582 instructions # 0.28 insn per cycle

insn per cycle = 1,484,582 / 1,749,936 = 0.85.
But now it's 0.28, that's not correct.

stat_config.stats[] records the per-thread runtime stat. But for interval
mode, it should be reset for each interval.

So now, with this patch,

root@kbl-ppc:~# perf stat --per-thread -e cycles,instructions -I1000 --interval-count 2
1.005818121 perf-8633 9,898,045 cycles
...
1.005818121 perf-8633 693,298 instructions # 0.07 insn per cycle
...
2.007863743 perf-8633 1,551,619 cycles
...
2.007863743 perf-8633 1,317,514 instructions # 0.85 insn per cycle
...

Let's check interval 2.007863743.

insn per cycle = 1,317,514 / 1,551,619 = 0.85. It's correct.

This patch creates runtime_stat_reset, places it next to
untime_stat_new/runtime_stat_delete and moves all runtime_stat
functions before process_interval.

v4:
---
Create runtime_stat_reset.

Fixes: commit 14e72a21c783 ("perf stat: Update or print per-thread stats")
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
---
tools/perf/builtin-stat.c | 70 +++++++++++++++++++++++----------------
1 file changed, 41 insertions(+), 29 deletions(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index e0c1ad23c768..f3b3a59ac7d2 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -351,6 +351,46 @@ static void read_counters(struct timespec *rs)
}
}

+static int runtime_stat_new(struct perf_stat_config *config, int nthreads)
+{
+ int i;
+
+ config->stats = calloc(nthreads, sizeof(struct runtime_stat));
+ if (!config->stats)
+ return -1;
+
+ config->stats_num = nthreads;
+
+ for (i = 0; i < nthreads; i++)
+ runtime_stat__init(&config->stats[i]);
+
+ return 0;
+}
+
+static void runtime_stat_delete(struct perf_stat_config *config)
+{
+ int i;
+
+ if (!config->stats)
+ return;
+
+ for (i = 0; i < config->stats_num; i++)
+ runtime_stat__exit(&config->stats[i]);
+
+ zfree(&config->stats);
+}
+
+static void runtime_stat_reset(struct perf_stat_config *config)
+{
+ int i;
+
+ if (!config->stats)
+ return;
+
+ for (i = 0; i < config->stats_num; i++)
+ perf_stat__reset_shadow_per_stat(&config->stats[i]);
+}
+
static void process_interval(void)
{
struct timespec ts, rs;
@@ -359,6 +399,7 @@ static void process_interval(void)
diff_timespec(&rs, &ts, &ref_time);

perf_stat__reset_shadow_per_stat(&rt_stat);
+ runtime_stat_reset(&stat_config);
read_counters(&rs);

if (STAT_RECORD) {
@@ -1737,35 +1778,6 @@ int process_cpu_map_event(struct perf_session *session,
return set_maps(st);
}

-static int runtime_stat_new(struct perf_stat_config *config, int nthreads)
-{
- int i;
-
- config->stats = calloc(nthreads, sizeof(struct runtime_stat));
- if (!config->stats)
- return -1;
-
- config->stats_num = nthreads;
-
- for (i = 0; i < nthreads; i++)
- runtime_stat__init(&config->stats[i]);
-
- return 0;
-}
-
-static void runtime_stat_delete(struct perf_stat_config *config)
-{
- int i;
-
- if (!config->stats)
- return;
-
- for (i = 0; i < config->stats_num; i++)
- runtime_stat__exit(&config->stats[i]);
-
- zfree(&config->stats);
-}
-
static const char * const stat_report_usage[] = {
"perf stat report [<options>]",
NULL,
--
2.17.1