From: Niklas Cassel <niklas.cassel@xxxxxxx>
Commit 56440e63ac17 ("fio: report percentiles for slat, clat, lat")
together with commit 38ec5c514104 ("stat: make priority summary statistics
consistent with percentiles") changed so that per prio stats track either
completion latency (clat) or total latency (lat), depending on the option
lat_percentiles.
It is not obvious why add_clat_sample() shouldn't add a high/low clat prio
sample when option lat_percentiles is set, especially considering that
option lat_percentiles is usually used for controlling if total latency
percentiles should be displayed or not.
Add comments to describe why add_clat_sample() has to care about option
lat_percentiles.
Signed-off-by: Niklas Cassel <niklas.cassel@xxxxxxx>
Reviewed-by: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
---
stat.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/stat.c b/stat.c
index e0dc99b6..8bb49e4b 100644
--- a/stat.c
+++ b/stat.c
@@ -3089,6 +3089,15 @@ void add_clat_sample(struct thread_data *td, enum fio_ddir ddir,
add_stat_sample(&ts->clat_stat[ddir], nsec);
+ /*
+ * When lat_percentiles=1 (default 0), the reported high/low priority
+ * percentiles and stats are used for describing total latency values,
+ * even though the variable names themselves start with clat_.
+ *
+ * Because of the above definition, add a prio stat sample only when
+ * lat_percentiles=0. add_lat_sample() will add the prio stat sample
+ * when lat_percentiles=1.
+ */
if (!ts->lat_percentiles) {
if (high_prio)
add_stat_sample(&ts->clat_high_prio_stat[ddir], nsec);
@@ -3101,6 +3110,11 @@ void add_clat_sample(struct thread_data *td, enum fio_ddir ddir,
offset, ioprio);
if (ts->clat_percentiles) {
+ /*
+ * Because of the above definition, add a prio lat percentile
+ * sample only when lat_percentiles=0. add_lat_sample() will add
+ * the prio lat percentile sample when lat_percentiles=1.
+ */
if (ts->lat_percentiles)
add_lat_percentile_sample_noprio(ts, nsec, ddir, FIO_CLAT);
else
@@ -3194,6 +3208,16 @@ void add_lat_sample(struct thread_data *td, enum fio_ddir ddir,
add_log_sample(td, td->lat_log, sample_val(nsec), ddir, bs,
offset, ioprio);
+ /*
+ * When lat_percentiles=1 (default 0), the reported high/low priority
+ * percentiles and stats are used for describing total latency values,
+ * even though the variable names themselves start with clat_.
+ *
+ * Because of the above definition, add a prio stat and prio lat
+ * percentile sample only when lat_percentiles=1. add_clat_sample() will
+ * add the prio stat and prio lat percentile sample when
+ * lat_percentiles=0.
+ */
if (ts->lat_percentiles) {
add_lat_percentile_sample(ts, nsec, ddir, high_prio, FIO_LAT);
if (high_prio)
--
2.33.1
