vhost: simplify getting first in-flight index

This patch reworks the function getting the index
for the first packet in-flight.

When this index turns out to be zero, let's use the simple
path. Doing that avoid having to do a modulo with the
virtqueue size.

The patch also rename the function for better clarification,
and only pass the virtqueue metadata pointer, as all the
needed information are stored there.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Jiayu Hu <jiayu.hu@intel.com>

diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
index 3206b3f816d4fc30b2dca36d12e48f0dcaed63fd..2f76523e67bbbd7db6451e12480f317639d2fe2c 100644 (file)
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -1490,11 +1490,14 @@ rte_vhost_enqueue_burst(int vid, uint16_t queue_id,
 }
 
 static __rte_always_inline uint16_t
-virtio_dev_rx_async_get_info_idx(uint16_t pkts_idx,
-       uint16_t vq_size, uint16_t n_inflight)
+async_get_first_inflight_pkt_idx(struct vhost_virtqueue *vq)
 {
-       return pkts_idx > n_inflight ? (pkts_idx - n_inflight) :
-               (vq_size - n_inflight + pkts_idx) % vq_size;
+       struct vhost_async *async = vq->async;
+
+       if (async->pkts_idx >= async->pkts_inflight_n)
+               return async->pkts_idx - async->pkts_inflight_n;
+       else
+               return vq->size - async->pkts_inflight_n + async->pkts_idx;
 }
 
 static __rte_always_inline void
@@ -1932,9 +1935,6 @@ vhost_poll_enqueue_completed(struct virtio_net *dev, uint16_t queue_id,
        uint16_t n_descs = 0, n_buffers = 0;
        uint16_t start_idx, from, i;
 
-       start_idx = virtio_dev_rx_async_get_info_idx(async->pkts_idx,
-               vq->size, async->pkts_inflight_n);
-
        n_cpl = async->ops.check_completed_copies(dev->vid, queue_id, 0, count);
        if (unlikely(n_cpl < 0)) {
                VHOST_LOG_DATA(ERR, "(%d) %s: failed to check completed copies for queue id %d.\n",
@@ -1945,6 +1945,8 @@ vhost_poll_enqueue_completed(struct virtio_net *dev, uint16_t queue_id,
        if (n_cpl == 0)
                return 0;
 
+       start_idx = async_get_first_inflight_pkt_idx(vq);
+
        for (i = 0; i < n_cpl; i++) {
                from = (start_idx + i) % vq->size;
                /* Only used with packed ring */