[dpdk-dev] [PATCH v2 2/2] event/sw: simplify credit scheme

[Gage Eads <gage.eads@intel.com>]

This commit modifies the sw PMD credit scheme such that credits are
consumed when enqueueing a NEW event and released when an event is
released -- typically, the beginning and end of a pipeline. Workers that
simply forward events do not interact with the credit pool.

Signed-off-by: Gage Eads <gage.eads@intel.com>
Acked-by: Harry van Haaren <harry.van.haaren@intel.com>
---
 drivers/event/sw/sw_evdev_worker.c | 38 +++++++++++++++++++-------------------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/drivers/event/sw/sw_evdev_worker.c b/drivers/event/sw/sw_evdev_worker.c
index 93cd29b..766c836 100644
--- a/drivers/event/sw/sw_evdev_worker.c
+++ b/drivers/event/sw/sw_evdev_worker.c
@@ -85,6 +85,7 @@ sw_event_enqueue_burst(void *port, const struct rte_event ev[], uint16_t num)
 	struct sw_port *p = port;
 	struct sw_evdev *sw = (void *)p->sw;
 	uint32_t sw_inflights = rte_atomic32_read(&sw->inflights);
+	uint32_t credit_update_quanta = sw->credit_update_quanta;
 	int new = 0;
 
 	if (num > PORT_ENQUEUE_MAX_BURST_SIZE)
@@ -98,7 +99,6 @@ sw_event_enqueue_burst(void *port, const struct rte_event ev[], uint16_t num)
 
 	if (p->inflight_credits < new) {
 		/* check if event enqueue brings port over max threshold */
-		uint32_t credit_update_quanta = sw->credit_update_quanta;
 		if (sw_inflights + credit_update_quanta > sw->nb_events_limit)
 			return 0;
 
@@ -109,7 +109,6 @@ sw_event_enqueue_burst(void *port, const struct rte_event ev[], uint16_t num)
 			return 0;
 	}
 
-	uint32_t completions = 0;
 	for (i = 0; i < num; i++) {
 		int op = ev[i].op;
 		int outstanding = p->outstanding_releases > 0;
@@ -126,21 +125,16 @@ sw_event_enqueue_burst(void *port, const struct rte_event ev[], uint16_t num)
 		 * correct usage of the API), providing very high correct
 		 * prediction rate.
 		 */
-		if ((new_ops[i] & QE_FLAG_COMPLETE) && outstanding) {
+		if ((new_ops[i] & QE_FLAG_COMPLETE) && outstanding)
 			p->outstanding_releases--;
-			completions++;
-		}
 
 		/* error case: branch to avoid touching p->stats */
-		if (unlikely(invalid_qid)) {
+		if (unlikely(invalid_qid && op != RTE_EVENT_OP_RELEASE)) {
 			p->stats.rx_dropped++;
 			p->inflight_credits++;
 		}
 	}
 
-	/* handle directed port forward and release credits */
-	p->inflight_credits -= completions * p->is_directed;
-
 	/* returns number of events actually enqueued */
 	uint32_t enq = enqueue_burst_with_ops(p->rx_worker_ring, ev, i,
 					     new_ops);
@@ -153,6 +147,13 @@ sw_event_enqueue_burst(void *port, const struct rte_event ev[], uint16_t num)
 		p->avg_pkt_ticks += burst_pkt_ticks / NUM_SAMPLES;
 		p->last_dequeue_ticks = 0;
 	}
+
+	/* Replenish credits if enough releases are performed */
+	if (p->inflight_credits >= credit_update_quanta * 2) {
+		rte_atomic32_sub(&sw->inflights, credit_update_quanta);
+		p->inflight_credits -= credit_update_quanta;
+	}
+
 	return enq;
 }
 
@@ -168,16 +169,22 @@ sw_event_dequeue_burst(void *port, struct rte_event *ev, uint16_t num,
 {
 	RTE_SET_USED(wait);
 	struct sw_port *p = (void *)port;
-	struct sw_evdev *sw = (void *)p->sw;
 	struct rte_event_ring *ring = p->cq_worker_ring;
-	uint32_t credit_update_quanta = sw->credit_update_quanta;
 
 	/* check that all previous dequeues have been released */
-	if (p->implicit_release && !p->is_directed) {
+	if (p->implicit_release) {
+		struct sw_evdev *sw = (void *)p->sw;
+		uint32_t credit_update_quanta = sw->credit_update_quanta;
 		uint16_t out_rels = p->outstanding_releases;
 		uint16_t i;
 		for (i = 0; i < out_rels; i++)
 			sw_event_release(p, i);
+
+		/* Replenish credits if enough releases are performed */
+		if (p->inflight_credits >= credit_update_quanta * 2) {
+			rte_atomic32_sub(&sw->inflights, credit_update_quanta);
+			p->inflight_credits -= credit_update_quanta;
+		}
 	}
 
 	/* returns number of events actually dequeued */
@@ -188,8 +195,6 @@ sw_event_dequeue_burst(void *port, struct rte_event *ev, uint16_t num,
 		goto end;
 	}
 
-	/* only add credits for directed ports - LB ports send RELEASEs */
-	p->inflight_credits += ndeq * p->is_directed;
 	p->outstanding_releases += ndeq;
 	p->last_dequeue_burst_sz = ndeq;
 	p->last_dequeue_ticks = rte_get_timer_cycles();
@@ -197,11 +202,6 @@ sw_event_dequeue_burst(void *port, struct rte_event *ev, uint16_t num,
 	p->total_polls++;
 
 end:
-	if (p->inflight_credits >= credit_update_quanta * 2 &&
-			p->inflight_credits > credit_update_quanta + ndeq) {
-		rte_atomic32_sub(&sw->inflights, credit_update_quanta);
-		p->inflight_credits -= credit_update_quanta;
-	}
 	return ndeq;
 }
 
-- 
2.7.4