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From: Stephen Hemminger <stephen@networkplumber.org>
To: dev@dpdk.org
Cc: "Stephen Hemminger" <stephen@networkplumber.org>,
	"Morten Brørup" <mb@smartsharesystems.com>,
	"Tyler Retzlaff" <roretzla@linux.microsoft.com>,
	"Reshma Pattan" <reshma.pattan@intel.com>
Subject: [PATCH v4 1/6] latencystats: replace use of VLA
Date: Fri, 19 Apr 2024 10:28:21 -0700	[thread overview]
Message-ID: <20240419172926.55447-2-stephen@networkplumber.org> (raw)
In-Reply-To: <20240419172926.55447-1-stephen@networkplumber.org>

The temporary array latencystats is not needed if the algorithm
is converted into one pass.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Morten Brørup <mb@smartsharesystems.com>
Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
---
 lib/latencystats/rte_latencystats.c | 31 +++++++++++++++--------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/lib/latencystats/rte_latencystats.c b/lib/latencystats/rte_latencystats.c
index 4ea9b0d75b..9b345bfb33 100644
--- a/lib/latencystats/rte_latencystats.c
+++ b/lib/latencystats/rte_latencystats.c
@@ -157,9 +157,9 @@ calc_latency(uint16_t pid __rte_unused,
 		uint16_t nb_pkts,
 		void *_ __rte_unused)
 {
-	unsigned int i, cnt = 0;
+	unsigned int i;
 	uint64_t now;
-	float latency[nb_pkts];
+	float latency;
 	static float prev_latency;
 	/*
 	 * Alpha represents degree of weighting decrease in EWMA,
@@ -169,13 +169,14 @@ calc_latency(uint16_t pid __rte_unused,
 	const float alpha = 0.2;
 
 	now = rte_rdtsc();
-	for (i = 0; i < nb_pkts; i++) {
-		if (pkts[i]->ol_flags & timestamp_dynflag)
-			latency[cnt++] = now - *timestamp_dynfield(pkts[i]);
-	}
 
 	rte_spinlock_lock(&glob_stats->lock);
-	for (i = 0; i < cnt; i++) {
+	for (i = 0; i < nb_pkts; i++) {
+		if (!(pkts[i]->ol_flags & timestamp_dynflag))
+			continue;
+
+		latency = now - *timestamp_dynfield(pkts[i]);
+
 		/*
 		 * The jitter is calculated as statistical mean of interpacket
 		 * delay variation. The "jitter estimate" is computed by taking
@@ -187,22 +188,22 @@ calc_latency(uint16_t pid __rte_unused,
 		 * Reference: Calculated as per RFC 5481, sec 4.1,
 		 * RFC 3393 sec 4.5, RFC 1889 sec.
 		 */
-		glob_stats->jitter +=  (fabsf(prev_latency - latency[i])
+		glob_stats->jitter +=  (fabsf(prev_latency - latency)
 					- glob_stats->jitter)/16;
 		if (glob_stats->min_latency == 0)
-			glob_stats->min_latency = latency[i];
-		else if (latency[i] < glob_stats->min_latency)
-			glob_stats->min_latency = latency[i];
-		else if (latency[i] > glob_stats->max_latency)
-			glob_stats->max_latency = latency[i];
+			glob_stats->min_latency = latency;
+		else if (latency < glob_stats->min_latency)
+			glob_stats->min_latency = latency;
+		else if (latency > glob_stats->max_latency)
+			glob_stats->max_latency = latency;
 		/*
 		 * The average latency is measured using exponential moving
 		 * average, i.e. using EWMA
 		 * https://en.wikipedia.org/wiki/Moving_average
 		 */
 		glob_stats->avg_latency +=
-			alpha * (latency[i] - glob_stats->avg_latency);
-		prev_latency = latency[i];
+			alpha * (latency - glob_stats->avg_latency);
+		prev_latency = latency;
 	}
 	rte_spinlock_unlock(&glob_stats->lock);
 
-- 
2.43.0


  reply	other threads:[~2024-04-19 17:29 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-04-08 19:50 [RFC] latencystats: performance overhaul Stephen Hemminger
2024-04-08 21:26 ` [PATCH v2] " Stephen Hemminger
2024-04-19 17:28 ` [PATCH v4 0/6] latencystats: cleanup Stephen Hemminger
2024-04-19 17:28   ` Stephen Hemminger [this message]
2024-04-19 17:28   ` [PATCH v4 2/6] latencystats: handle fractional cycles per ns Stephen Hemminger
2024-04-19 17:28   ` [PATCH v4 3/6] latencystats: do not use floating point Stephen Hemminger
2024-04-19 18:49     ` Morten Brørup
2024-04-19 22:45       ` Stephen Hemminger
2024-04-20  7:31         ` Morten Brørup
2024-04-19 17:28   ` [PATCH v4 4/6] latencystats: fix log messages Stephen Hemminger
2024-04-19 17:28   ` [PATCH v4 5/6] latencystats: update include files Stephen Hemminger
2024-04-19 17:28   ` [PATCH v4 6/6] latencystats: fix for pedantic warnings Stephen Hemminger
2024-04-22 15:21 ` [PATCH v5 0/9] latencystats: improve algorithms and tests Stephen Hemminger
2024-04-22 15:21   ` [PATCH v5 1/9] latencystats: replace use of VLA Stephen Hemminger
2024-04-22 15:21   ` [PATCH v5 2/9] latencystats: handle fractional cycles per ns Stephen Hemminger
2024-04-22 15:21   ` [PATCH v5 3/9] latencystats: do not use floating point Stephen Hemminger
2024-04-22 15:21   ` [PATCH v5 4/9] latencystats: fix log messages Stephen Hemminger
2024-04-22 15:21   ` [PATCH v5 5/9] latencystats: update include files Stephen Hemminger
2024-04-22 15:21   ` [PATCH v5 6/9] latencystats: enforce that unused callback function is NULL Stephen Hemminger
2024-04-22 15:21   ` [PATCH v5 7/9] latencystats: add metric for number of samples Stephen Hemminger
2024-04-22 15:21   ` [PATCH v5 8/9] test: use initialization in latencystats test Stephen Hemminger
2024-04-22 15:21   ` [PATCH v5 9/9] test: add more latencystats tests Stephen Hemminger
2024-05-29 22:54 ` [PATCH v6 0/8] latencystats: improvements to algorithm and test Stephen Hemminger
2024-05-29 22:54   ` [PATCH v6 1/8] latencystats: replace use of VLA Stephen Hemminger
2024-05-29 22:54   ` [PATCH v6 2/8] latencystats: handle fractional cycles per ns Stephen Hemminger
2024-05-29 22:54   ` [PATCH v6 3/8] latencystats: do not use floating point Stephen Hemminger
2024-05-29 22:54   ` [PATCH v6 4/8] latencystats: fix log messages Stephen Hemminger
2024-05-29 22:54   ` [PATCH v6 5/8] latencystats: update include files Stephen Hemminger
2024-05-29 22:54   ` [PATCH v6 6/8] latencystats: enforce that unused callback function is NULL Stephen Hemminger
2024-05-29 22:54   ` [PATCH v6 7/8] latencystats: add metric for number of samples Stephen Hemminger
2024-05-29 22:54   ` [PATCH v6 8/8] test: update to latencystats tests Stephen Hemminger
2024-07-04 15:21   ` [PATCH v6 0/8] latencystats: improvements to algorithm and test David Marchand

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