[dpdk-dev] [PATCH v2 24/24] virtio: Remove hotspots

[Ouyang Changchun]

Remove those hotspots which is unnecessary when early returning occurs;
Also reverse one likely to unlikely to let compiler has better decision;

Signed-off-by: Changchun Ouyang <changchun.ouyang at intel.com>
---
 lib/librte_pmd_virtio/virtio_rxtx.c | 33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/lib/librte_pmd_virtio/virtio_rxtx.c 
b/lib/librte_pmd_virtio/virtio_rxtx.c
index c6d9ae7..c4731b5 100644
--- a/lib/librte_pmd_virtio/virtio_rxtx.c
+++ b/lib/librte_pmd_virtio/virtio_rxtx.c
@@ -476,13 +476,13 @@ uint16_t
 virtio_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t nb_pkts)
 {
        struct virtqueue *rxvq = rx_queue;
-       struct virtio_hw *hw = rxvq->hw;
+       struct virtio_hw *hw;
        struct rte_mbuf *rxm, *new_mbuf;
-       uint16_t nb_used, num, nb_rx = 0;
+       uint16_t nb_used, num, nb_rx;
        uint32_t len[VIRTIO_MBUF_BURST_SZ];
        struct rte_mbuf *rcv_pkts[VIRTIO_MBUF_BURST_SZ];
        int error;
-       uint32_t i, nb_enqueued = 0;
+       uint32_t i, nb_enqueued;
        const uint32_t hdr_size = sizeof(struct virtio_net_hdr);

        nb_used = VIRTQUEUE_NUSED(rxvq);
@@ -491,7 +491,7 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts, 
uint16_t nb_pkts)

        num = (uint16_t)(likely(nb_used <= nb_pkts) ? nb_used : nb_pkts);
        num = (uint16_t)(likely(num <= VIRTIO_MBUF_BURST_SZ) ? num : 
VIRTIO_MBUF_BURST_SZ);
-       if (likely(num > DESC_PER_CACHELINE))
+       if (unlikely(num > DESC_PER_CACHELINE))
                num = num - ((rxvq->vq_used_cons_idx + num) % 
DESC_PER_CACHELINE);

        if (num == 0)
@@ -499,6 +499,11 @@ virtio_recv_pkts(void *rx_queue, struct rte_mbuf 
**rx_pkts, uint16_t nb_pkts)

        num = virtqueue_dequeue_burst_rx(rxvq, rcv_pkts, len, num);
        PMD_RX_LOG(DEBUG, "used:%d dequeue:%d", nb_used, num);
+
+       hw = rxvq->hw;
+       nb_rx = 0;
+       nb_enqueued = 0;
+
        for (i = 0; i < num ; i++) {
                rxm = rcv_pkts[i];

@@ -568,17 +573,17 @@ virtio_recv_mergeable_pkts(void *rx_queue,
                        uint16_t nb_pkts)
 {
        struct virtqueue *rxvq = rx_queue;
-       struct virtio_hw *hw = rxvq->hw;
+       struct virtio_hw *hw;
        struct rte_mbuf *rxm, *new_mbuf;
-       uint16_t nb_used, num, nb_rx = 0;
+       uint16_t nb_used, num, nb_rx;
        uint32_t len[VIRTIO_MBUF_BURST_SZ];
        struct rte_mbuf *rcv_pkts[VIRTIO_MBUF_BURST_SZ];
        struct rte_mbuf *prev;
        int error;
-       uint32_t i = 0, nb_enqueued = 0;
-       uint32_t seg_num = 0;
-       uint16_t extra_idx = 0;
-       uint32_t seg_res = 0;
+       uint32_t i, nb_enqueued;
+       uint32_t seg_num;
+       uint16_t extra_idx;
+       uint32_t seg_res;
        const uint32_t hdr_size = sizeof(struct virtio_net_hdr_mrg_rxbuf);

        nb_used = VIRTQUEUE_NUSED(rxvq);
@@ -590,6 +595,14 @@ virtio_recv_mergeable_pkts(void *rx_queue,

        PMD_RX_LOG(DEBUG, "used:%d\n", nb_used);

+       hw = rxvq->hw;
+       nb_rx = 0;
+       i = 0;
+       nb_enqueued = 0;
+       seg_num = 0;
+       extra_idx = 0;
+       seg_res = 0;
+
        while (i < nb_used) {
                struct virtio_net_hdr_mrg_rxbuf *header;

-- 
1.8.4.2