[PATCH v5 7/9] latencystats: add metric for number of samples

[Stephen Hemminger]

Keeping track of the number of samples is useful when doing
debug and testing to make sure that samples are actually happening.

Signed-off-by: Stephen Hemminger <step...@networkplumber.org>
---
 lib/latencystats/rte_latencystats.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/lib/latencystats/rte_latencystats.c 
b/lib/latencystats/rte_latencystats.c
index 8311adb411..e5a84fbd92 100644
--- a/lib/latencystats/rte_latencystats.c
+++ b/lib/latencystats/rte_latencystats.c
@@ -59,6 +59,7 @@ struct rte_latency_stats {
        uint64_t avg_latency; /**< Average latency */
        uint64_t max_latency; /**< Maximum latency */
        uint64_t jitter; /** Latency variation */
+       uint64_t samples;    /** Number of latency samples */
        rte_spinlock_t lock; /** Latency calculation lock */
 };
 
@@ -82,20 +83,26 @@ static const struct latency_stats_nameoff 
lat_stats_strings[] = {
        {"avg_latency_ns", offsetof(struct rte_latency_stats, avg_latency), 
LATENCY_AVG_SCALE},
        {"max_latency_ns", offsetof(struct rte_latency_stats, max_latency), 1},
        {"jitter_ns", offsetof(struct rte_latency_stats, jitter), 
LATENCY_JITTER_SCALE},
+       {"samples", offsetof(struct rte_latency_stats, samples), 0},
 };
 
-#define NUM_LATENCY_STATS (sizeof(lat_stats_strings) / \
-                               sizeof(lat_stats_strings[0]))
+#define NUM_LATENCY_STATS RTE_DIM(lat_stats_strings)
 
 static void
 latencystats_collect(uint64_t values[])
 {
-       unsigned int i;
+       unsigned int i, scale;
        const uint64_t *stats;
 
        for (i = 0; i < NUM_LATENCY_STATS; i++) {
                stats = RTE_PTR_ADD(glob_stats, lat_stats_strings[i].offset);
-               values[i] = floor(*stats / (cycles_per_ns * 
lat_stats_strings[i].scale));
+               scale = lat_stats_strings[i].scale;
+
+               /* used to mark samples which are not a time interval */
+               if (scale == 0)
+                       values[i] = *stats;
+               else
+                       values[i] = floor(*stats / (cycles_per_ns * scale));
        }
 }
 
@@ -173,7 +180,6 @@ calc_latency(uint16_t pid __rte_unused,
        unsigned int i;
        uint64_t now, latency;
        static uint64_t prev_latency;
-       static bool first_sample = true;
 
        now = rte_rdtsc();
 
@@ -184,9 +190,7 @@ calc_latency(uint16_t pid __rte_unused,
 
                latency = now - *timestamp_dynfield(pkts[i]);
 
-               if (unlikely(first_sample)) {
-                       first_sample = false;
-
+               if (glob_stats->samples++ == 0) {
                        glob_stats->min_latency = latency;
                        glob_stats->max_latency = latency;
                        glob_stats->avg_latency = latency * 4;
-- 
2.43.0