[dpdk-dev] [PATCH v2] meter: fix excess token bucket update in srtcm implementation

[Nikhil Jagtap]

As per srTCM RFC 2697, we should be updating the E bucket only after the
C bucket overflows. This patch fixes the current DPDK implementation,
where we are updating both the buckets simultaneously at the same rate
(CIR) which results in token accumulation rate of (2*CIR).

Signed-off-by: Nikhil Jagtap <nikhil.jagtap at gmail.com>
---

v2:
Removed the else part and instead added a default initialization of te.

---
 lib/librte_meter/rte_meter.h |   24 ++++++++++++++----------
 1 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/lib/librte_meter/rte_meter.h b/lib/librte_meter/rte_meter.h
index 2cd8d81..2ab7184 100644
--- a/lib/librte_meter/rte_meter.h
+++ b/lib/librte_meter/rte_meter.h
@@ -232,13 +232,15 @@ rte_meter_srtcm_color_blind_check(struct rte_meter_srtcm *m,
 	n_periods = time_diff / m->cir_period;
 	m->time += n_periods * m->cir_period;
 
+	/* Put the tokens overflowing from tc into te bucket */
 	tc = m->tc + n_periods * m->cir_bytes_per_period;
-	if (tc > m->cbs)
+	te = m->te;
+	if (tc > m->cbs) {
+		te += (tc - m->cbs);
+		if (te > m->ebs)
+			te = m->ebs;
 		tc = m->cbs;
-
-	te = m->te + n_periods * m->cir_bytes_per_period;
-	if (te > m->ebs)
-		te = m->ebs;
+	}
 
 	/* Color logic */
 	if (tc >= pkt_len) {
@@ -271,13 +273,15 @@ rte_meter_srtcm_color_aware_check(struct rte_meter_srtcm *m,
 	n_periods = time_diff / m->cir_period;
 	m->time += n_periods * m->cir_period;
 
+	/* Put the tokens overflowing from tc into te bucket */
 	tc = m->tc + n_periods * m->cir_bytes_per_period;
-	if (tc > m->cbs)
+	te = m->te;
+	if (tc > m->cbs) {
+		te += (tc - m->cbs);
+		if (te > m->ebs)
+			te = m->ebs;
 		tc = m->cbs;
-
-	te = m->te + n_periods * m->cir_bytes_per_period;
-	if (te > m->ebs)
-		te = m->ebs;
+	}
 
 	/* Color logic */
 	if ((pkt_color == e_RTE_METER_GREEN) && (tc >= pkt_len)) {
-- 
1.7.1