[dpdk-dev] [PATCH v2] event/sw: code refractor to reduce the fetch stall

[Vipin Varghese]

With rearranging the code to prefetch the contents before
loop check increases performance from single and multistage
atomic pipeline.

Signed-off-by: Vipin Varghese <vipin.varghese at intel.com>
Acked-by: Harry van Haaren <harry.van.haaren at intel.com>
---

Changes in V2:
 - compilation fix for const flowid - Harry
 - Removal of sw_refill_pp_buf logic - Harry
---
 drivers/event/sw/sw_evdev_scheduler.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/event/sw/sw_evdev_scheduler.c b/drivers/event/sw/sw_evdev_scheduler.c
index e3a41e0..98dcf68 100644
--- a/drivers/event/sw/sw_evdev_scheduler.c
+++ b/drivers/event/sw/sw_evdev_scheduler.c
@@ -44,12 +44,13 @@
 	uint32_t qid_id = qid->id;
 
 	iq_dequeue_burst(sw, &qid->iq[iq_num], qes, count);
-	for (i = 0; i < count; i++) {
-		const struct rte_event *qe = &qes[i];
-		const uint16_t flow_id = SW_HASH_FLOWID(qes[i].flow_id);
-		struct sw_fid_t *fid = &qid->fids[flow_id];
-		int cq = fid->cq;
 
+	const struct rte_event *qe = &qes[i];
+	uint16_t flow_id = SW_HASH_FLOWID(qes[i].flow_id);
+	struct sw_fid_t *fid = &qid->fids[flow_id];
+	int cq = fid->cq;
+
+	for (i = 0; i < count; i++) {
 		if (cq < 0) {
 			uint32_t cq_idx = qid->cq_next_tx++;
 			if (qid->cq_next_tx == qid->cq_num_mapped_cqs)
@@ -101,6 +102,14 @@
 					&sw->cq_ring_space[cq]);
 			p->cq_buf_count = 0;
 		}
+
+		if (likely(i+1 < count)) {
+			qe = (qes + i + 1);
+			flow_id = SW_HASH_FLOWID(qes[i + 1].flow_id);
+			fid = &qid->fids[flow_id];
+			cq = fid->cq;
+		}
+
 	}
 	iq_put_back(sw, &qid->iq[iq_num], blocked_qes, nb_blocked);
 
-- 
1.9.1