[dpdk-dev] [PATCH v6 07/13] vhost: flush enqueue updates by batch

[Maxime Coquelin]

On 10/15/19 6:07 PM, Marvin Liu wrote:
> Buffer vhost enqueue shadowed ring flush action buffered number exceed
> one batch. Thus virtio can receive packets at a faster frequency.

The commit message isn't very clear to me. Could you please improve it?

> Signed-off-by: Marvin Liu <yong.liu at intel.com>
> 
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> index 96bf763b1..a60b88d89 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -166,6 +166,8 @@ struct vhost_virtqueue {
>  		struct vring_used_elem_packed *shadow_used_packed;
>  	};
>  	uint16_t                shadow_used_idx;
> +	/* Record packed ring enqueue latest desc cache aligned index */
> +	uint16_t		shadow_aligned_idx;
>  	struct vhost_vring_addr ring_addrs;
>  
>  	struct batch_copy_elem	*batch_copy_elems;
> diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> index 274a28f99..020c9b858 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -91,6 +91,69 @@ update_shadow_used_ring_split(struct vhost_virtqueue *vq,
>  	vq->shadow_used_split[i].len = len;
>  }
>  
> +static __rte_always_inline void
> +vhost_flush_enqueue_shadow_packed(struct virtio_net *dev,
> +				  struct vhost_virtqueue *vq)
> +{
> +	int i;
> +	uint16_t used_idx = vq->last_used_idx;
> +	uint16_t head_idx = vq->last_used_idx;
> +	uint16_t head_flags = 0;
> +
> +	/* Split loop in two to save memory barriers */
> +	for (i = 0; i < vq->shadow_used_idx; i++) {
> +		vq->desc_packed[used_idx].id = vq->shadow_used_packed[i].id;
> +		vq->desc_packed[used_idx].len = vq->shadow_used_packed[i].len;
> +
> +		used_idx += vq->shadow_used_packed[i].count;
> +		if (used_idx >= vq->size)
> +			used_idx -= vq->size;
> +	}
> +
> +	rte_smp_wmb();
> +
> +	for (i = 0; i < vq->shadow_used_idx; i++) {
> +		uint16_t flags;
> +
> +		if (vq->shadow_used_packed[i].len)
> +			flags = VRING_DESC_F_WRITE;
> +		else
> +			flags = 0;
> +
> +		if (vq->used_wrap_counter) {
> +			flags |= VRING_DESC_F_USED;
> +			flags |= VRING_DESC_F_AVAIL;
> +		} else {
> +			flags &= ~VRING_DESC_F_USED;
> +			flags &= ~VRING_DESC_F_AVAIL;
> +		}
> +
> +		if (i > 0) {
> +			vq->desc_packed[vq->last_used_idx].flags = flags;
> +
> +			vhost_log_cache_used_vring(dev, vq,
> +					vq->last_used_idx *
> +					sizeof(struct vring_packed_desc),
> +					sizeof(struct vring_packed_desc));
> +		} else {
> +			head_idx = vq->last_used_idx;
> +			head_flags = flags;
> +		}
> +
> +		vq_inc_last_used_packed(vq, vq->shadow_used_packed[i].count);
> +	}
> +
> +	vq->desc_packed[head_idx].flags = head_flags;
> +
> +	vhost_log_cache_used_vring(dev, vq,
> +				head_idx *
> +				sizeof(struct vring_packed_desc),
> +				sizeof(struct vring_packed_desc));
> +
> +	vq->shadow_used_idx = 0;
> +	vhost_log_cache_sync(dev, vq);
> +}
> +
>  static __rte_always_inline void
>  flush_shadow_used_ring_packed(struct virtio_net *dev,
>  			struct vhost_virtqueue *vq)
> @@ -194,6 +257,33 @@ do_data_copy_dequeue(struct vhost_virtqueue *vq)
>  	vq->batch_copy_nb_elems = 0;
>  }
>  
> +static __rte_always_inline void
> +vhost_shadow_enqueue_single_packed(struct virtio_net *dev,
> +				   struct vhost_virtqueue *vq,
> +				   uint32_t len[],
> +				   uint16_t id[],
> +				   uint16_t count[],
> +				   uint16_t num_buffers)
> +{
> +	uint16_t i;
> +	for (i = 0; i < num_buffers; i++) {
> +		/* enqueue shadow flush action aligned with batch num */
> +		if (!vq->shadow_used_idx)
> +			vq->shadow_aligned_idx = vq->last_used_idx &
> +				PACKED_BATCH_MASK;
> +		vq->shadow_used_packed[vq->shadow_used_idx].id  = id[i];
> +		vq->shadow_used_packed[vq->shadow_used_idx].len = len[i];
> +		vq->shadow_used_packed[vq->shadow_used_idx].count = count[i];
> +		vq->shadow_aligned_idx += count[i];
> +		vq->shadow_used_idx++;
> +	}
> +
> +	if (vq->shadow_aligned_idx >= PACKED_BATCH_SIZE) {
> +		do_data_copy_enqueue(dev, vq);
> +		vhost_flush_enqueue_shadow_packed(dev, vq);
> +	}
> +}
> +
>  /* avoid write operation when necessary, to lessen cache issues */
>  #define ASSIGN_UNLESS_EQUAL(var, val) do {	\
>  	if ((var) != (val))			\
> @@ -785,6 +875,9 @@ vhost_enqueue_single_packed(struct virtio_net *dev,
>  	uint16_t desc_count;
>  	uint32_t size = pkt->pkt_len + dev->vhost_hlen;
>  	uint16_t num_buffers = 0;
> +	uint32_t buffer_len[vq->size];
> +	uint16_t buffer_buf_id[vq->size];
> +	uint16_t buffer_desc_count[vq->size];

With rings up to 1024 elements, maybe it would be better to have that
allocated as vq metadata like shadow_used_packed?

>  
>  	if (rxvq_is_mergeable(dev))
>  		max_tries = vq->size - 1;
> @@ -810,6 +903,9 @@ vhost_enqueue_single_packed(struct virtio_net *dev,
>  		len = RTE_MIN(len, size);
>  		size -= len;
>  
> +		buffer_len[num_buffers] = len;
> +		buffer_buf_id[num_buffers] = buf_id;
> +		buffer_desc_count[num_buffers] = desc_count;
>  		num_buffers += 1;
>  
>  		*nr_descs += desc_count;
> @@ -821,6 +917,9 @@ vhost_enqueue_single_packed(struct virtio_net *dev,
>  	if (copy_mbuf_to_desc(dev, vq, pkt, buf_vec, nr_vec, num_buffers) < 0)
>  		return -1;
>  
> +	vhost_shadow_enqueue_single_packed(dev, vq, buffer_len, buffer_buf_id,
> +					   buffer_desc_count, num_buffers);
> +
>  	return 0;
>  }
>  
> @@ -1017,7 +1116,7 @@ virtio_dev_rx_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
>  	do_data_copy_enqueue(dev, vq);
>  
>  	if (likely(vq->shadow_used_idx)) {
> -		flush_shadow_used_ring_packed(dev, vq);
> +		vhost_flush_enqueue_shadow_packed(dev, vq);
>  		vhost_vring_call_packed(dev, vq);
>  	}
>  
>