[dpdk-dev] [PATCH 2/5] virtio: don't use unlikely for normal tx stuff

[Stephen Hemminger]

Don't use unlikely() for VLAN or ring getting full.
GCC will not optimize code in unlikely paths and since these can
happen with normal code that can hurt performance.

Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
---
 drivers/net/virtio/virtio_rxtx.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index 5b50ed0..dbe6665 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -763,7 +763,7 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, 
uint16_t nb_pkts)
                int need = txm->nb_segs - txvq->vq_free_cnt + 1;

                /* Positive value indicates it need free vring descriptors */
-               if (unlikely(need > 0)) {
+               if (need > 0) {
                        nb_used = VIRTQUEUE_NUSED(txvq);
                        virtio_rmb();
                        need = RTE_MIN(need, (int)nb_used);
@@ -778,7 +778,7 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, 
uint16_t nb_pkts)
                }

                /* Do VLAN tag insertion */
-               if (unlikely(txm->ol_flags & PKT_TX_VLAN_PKT)) {
+               if (txm->ol_flags & PKT_TX_VLAN_PKT) {
                        error = rte_vlan_insert(&txm);
                        if (unlikely(error)) {
                                rte_pktmbuf_free(txm);
@@ -798,10 +798,9 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf 
**tx_pkts, uint16_t nb_pkts)
                        break;
                }
                txvq->bytes += txm->pkt_len;
+               ++txvq->packets;
        }

-       txvq->packets += nb_tx;
-
        if (likely(nb_tx)) {
                vq_update_avail_idx(txvq);

-- 
2.1.4