[dpdk-dev] [PATCH v2 16/16] vhost: optimize packed ring dequeue when in-order

[Marvin Liu]

When VIRTIO_F_IN_ORDER feature is negotiated, vhost can optimize dequeue
function by only update first used descriptor.

Signed-off-by: Marvin Liu <yong....@intel.com>

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 357517cdd..a7bb4ec79 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -31,6 +31,12 @@ rxvq_is_mergeable(struct virtio_net *dev)
        return dev->features & (1ULL << VIRTIO_NET_F_MRG_RXBUF);
 }
 
+static  __rte_always_inline bool
+virtio_net_is_inorder(struct virtio_net *dev)
+{
+       return dev->features & (1ULL << VIRTIO_F_IN_ORDER);
+}
+
 static bool
 is_valid_virt_queue_idx(uint32_t idx, int is_tx, uint32_t nr_vring)
 {
@@ -213,6 +219,30 @@ flush_burst_packed(struct virtio_net *dev, struct 
vhost_virtqueue *vq,
        }
 }
 
+static __rte_always_inline void
+update_dequeue_burst_packed_inorder(struct vhost_virtqueue *vq, uint16_t id)
+{
+       vq->shadow_used_packed[0].id  = id;
+
+       if (!vq->shadow_used_idx) {
+               vq->dequeue_shadow_head = vq->last_used_idx;
+               vq->shadow_used_packed[0].len = 0;
+               vq->shadow_used_packed[0].count = 1;
+               vq->shadow_used_packed[0].used_idx = vq->last_used_idx;
+               vq->shadow_used_packed[0].used_wrap_counter =
+                       vq->used_wrap_counter;
+
+               vq->shadow_used_idx = 1;
+
+       }
+
+       vq->last_used_idx += PACKED_DESCS_BURST;
+       if (vq->last_used_idx >= vq->size) {
+               vq->used_wrap_counter ^= 1;
+               vq->last_used_idx -= vq->size;
+       }
+}
+
 static __rte_always_inline void
 update_dequeue_burst_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
        uint16_t *ids)
@@ -315,7 +345,6 @@ update_dequeue_shadow_packed(struct vhost_virtqueue *vq, 
uint16_t buf_id,
                else
                        vq->desc_packed[vq->last_used_idx].flags =
                                VIRTIO_TX_USED_WRAP_FLAG;
-
        }
 
        vq->last_used_idx += count;
@@ -326,6 +355,31 @@ update_dequeue_shadow_packed(struct vhost_virtqueue *vq, 
uint16_t buf_id,
        }
 }
 
+static __rte_always_inline void
+update_dequeue_shadow_packed_inorder(struct vhost_virtqueue *vq,
+       uint16_t buf_id, uint16_t count)
+{
+       vq->shadow_used_packed[0].id = buf_id;
+
+       if (!vq->shadow_used_idx) {
+               vq->dequeue_shadow_head = vq->last_used_idx;
+
+               vq->shadow_used_packed[0].len = 0;
+               vq->shadow_used_packed[0].count = count;
+               vq->shadow_used_packed[0].used_idx = vq->last_used_idx;
+               vq->shadow_used_packed[0].used_wrap_counter =
+                       vq->used_wrap_counter;
+
+               vq->shadow_used_idx = 1;
+       }
+
+       vq->last_used_idx += count;
+
+       if (vq->last_used_idx >= vq->size) {
+               vq->used_wrap_counter ^= 1;
+               vq->last_used_idx -= vq->size;
+       }
+}
 
 static inline void
 do_data_copy_enqueue(struct virtio_net *dev, struct vhost_virtqueue *vq)
@@ -1834,7 +1888,12 @@ virtio_dev_tx_burst_packed(struct virtio_net *dev, 
struct vhost_virtqueue *vq,
                           pkts[i]->pkt_len);
        }
 
-       update_dequeue_burst_packed(dev, vq, ids);
+       if (virtio_net_is_inorder(dev))
+               update_dequeue_burst_packed_inorder(vq,
+                                                   ids[PACKED_BURST_MASK]);
+       else
+               update_dequeue_burst_packed(dev, vq, ids);
+
        if (virtio_net_with_host_offload(dev)) {
                UNROLL_PRAGMA(PRAGMA_PARAM)
                for (i = 0; i < PACKED_DESCS_BURST; i++) {
@@ -1897,7 +1956,10 @@ virtio_dev_tx_single_packed(struct virtio_net *dev, 
struct vhost_virtqueue *vq,
                                        &desc_count))
                return -1;
 
-       update_dequeue_shadow_packed(vq, buf_id, desc_count);
+       if (virtio_net_is_inorder(dev))
+               update_dequeue_shadow_packed_inorder(vq, buf_id, desc_count);
+       else
+               update_dequeue_shadow_packed(vq, buf_id, desc_count);
 
        vq->last_avail_idx += desc_count;
        if (vq->last_avail_idx >= vq->size) {
-- 
2.17.1