[dpdk-dev] [PATCH v5 4/6] vhost: add desc prefetch

[Zhihong Wang]

This patch adds descriptor prefetch to hide cache access latency.

Signed-off-by: Zhihong Wang <zhihong.wang at intel.com>
---
 lib/librte_vhost/virtio_net.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 6f63968..b38f18f 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -302,6 +302,12 @@ rte_vhost_enqueue_burst(int vid, uint16_t queue_id,
        /* start enqueuing packets 1 by 1 */
        avail_idx = *((volatile uint16_t *)&vq->avail->idx);
        while (pkt_left && avail_idx != vq->last_used_idx) {
+               /* prefetch the next desc */
+               if (pkt_left > 1 && avail_idx != vq->last_used_idx + 1)
+                       rte_prefetch0(&vq->desc[vq->avail->ring[
+                                       (vq->last_used_idx + 1) &
+                                       (vq->size - 1)]]);
+
                if (enqueue_packet(dev, vq, avail_idx, pkts[pkt_idx],
                                        is_mrg_rxbuf))
                        break;
-- 
2.7.4