[PATCH v4 2/6] latencystats: handle fractional cycles per ns

[Stephen Hemminger <stephen@networkplumber.org>]

The timer_hz is not always an integral number of nanoseconds.
For examples, cycles per nanoseconds on my test system is 2.8.
Fix by using floating point where needed and calculate value once.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/latencystats/rte_latencystats.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/lib/latencystats/rte_latencystats.c b/lib/latencystats/rte_latencystats.c
index 9b345bfb33..55a099c818 100644
--- a/lib/latencystats/rte_latencystats.c
+++ b/lib/latencystats/rte_latencystats.c
@@ -18,12 +18,7 @@
 /** Nano seconds per second */
 #define NS_PER_SEC 1E9
 
-/** Clock cycles per nano second */
-static uint64_t
-latencystat_cycles_per_ns(void)
-{
-	return rte_get_timer_hz() / NS_PER_SEC;
-}
+static double cycles_per_ns;
 
 RTE_LOG_REGISTER_DEFAULT(latencystat_logtype, INFO);
 #define RTE_LOGTYPE_LATENCY_STATS latencystat_logtype
@@ -89,8 +84,7 @@ rte_latencystats_update(void)
 	for (i = 0; i < NUM_LATENCY_STATS; i++) {
 		stats_ptr = RTE_PTR_ADD(glob_stats,
 				lat_stats_strings[i].offset);
-		values[i] = (uint64_t)floor((*stats_ptr)/
-				latencystat_cycles_per_ns());
+		values[i] = floor(*stats_ptr / cycles_per_ns);
 	}
 
 	ret = rte_metrics_update_values(RTE_METRICS_GLOBAL,
@@ -112,8 +106,7 @@ rte_latencystats_fill_values(struct rte_metric_value *values)
 		stats_ptr = RTE_PTR_ADD(glob_stats,
 				lat_stats_strings[i].offset);
 		values[i].key = i;
-		values[i].value = (uint64_t)floor((*stats_ptr)/
-						latencystat_cycles_per_ns());
+		values[i].value = floor(*stats_ptr / cycles_per_ns);
 	}
 }
 
@@ -235,9 +228,11 @@ rte_latencystats_init(uint64_t app_samp_intvl,
 		return -ENOMEM;
 	}
 
+	cycles_per_ns = (double)rte_get_timer_hz() / NS_PER_SEC;
+
 	glob_stats = mz->addr;
 	rte_spinlock_init(&glob_stats->lock);
-	samp_intvl = app_samp_intvl * latencystat_cycles_per_ns();
+	samp_intvl = (uint64_t)(app_samp_intvl * cycles_per_ns);
 
 	/** Register latency stats with stats library */
 	for (i = 0; i < NUM_LATENCY_STATS; i++)
-- 
2.43.0