event/sw: simplify credit scheme

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>

diff --git a/drivers/event/sw/sw_evdev_worker.c b/drivers/event/sw/sw_evdev_worker.c
index 5854be5..67151f7 100644 (file)
--- a/drivers/event/sw/sw_evdev_worker.c
+++ b/drivers/event/sw/sw_evdev_worker.c
@@ -57,6 +57,7 @@ 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)
@@ -70,7 +71,6 @@ 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;
 
@@ -81,7 +81,6 @@ 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;
@@ -98,21 +97,16 @@ 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);
@@ -125,6 +119,13 @@ 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;
 }
 
@@ -140,16 +141,22 @@ 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 */
@@ -160,8 +167,6 @@ 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();
@@ -169,11 +174,6 @@ 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;
 }