Re: [dpdk-stable] [PATCH 18.11] net/virtio: cleanup on demand when in-order Tx

[Kevin Traynor <ktraynor@redhat.com>]

On 16/03/2020 12:35, Marvin Liu wrote:
> [ upstream commit e76097f8489a0c4c8044f3382ad81452c4771624 ]
> 
> Check whether space are enough before burst enqueue operation. If more
> space is needed, will try to clean up used descriptors for space on
> demand. It can give more chances to free used descriptors, thus will
> help RFC2544 performance. Also deduct failed xmit packets from total
> xmit number.
> 
> Fixes: e5f456a98d3c ("net/virtio: support in-order Rx and Tx")
> 
> Signed-off-by: Marvin Liu <yong.liu@intel.com>
> Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> 
> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
> index 306009d96..2bbda8525 100644
> --- a/drivers/net/virtio/virtio_rxtx.c
> +++ b/drivers/net/virtio/virtio_rxtx.c
> @@ -1471,6 +1471,21 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
>  	return nb_tx;
>  }
>  
> +static __rte_always_inline int
> +virtio_xmit_try_cleanup_inorder(struct virtqueue *vq, uint16_t need)
> +{
> +	uint16_t nb_used, nb_clean, nb_descs;
> +
> +	nb_descs = vq->vq_free_cnt + need;
> +	nb_used = VIRTQUEUE_NUSED(vq);
> +	virtio_rmb();
> +	nb_clean = RTE_MIN(need, (int)nb_used);
> +
> +	virtio_xmit_cleanup_inorder(vq, nb_clean);
> +
> +	return nb_descs - vq->vq_free_cnt;
> +}
> +
>  uint16_t
>  virtio_xmit_pkts_inorder(void *tx_queue,
>  			struct rte_mbuf **tx_pkts,
> @@ -1480,8 +1495,9 @@ virtio_xmit_pkts_inorder(void *tx_queue,
>  	struct virtqueue *vq = txvq->vq;
>  	struct virtio_hw *hw = vq->hw;
>  	uint16_t hdr_size = hw->vtnet_hdr_size;
> -	uint16_t nb_used, nb_avail, nb_tx = 0, nb_inorder_pkts = 0;
> +	uint16_t nb_used, nb_tx = 0, nb_inorder_pkts = 0;
>  	struct rte_mbuf *inorder_pkts[nb_pkts];
> +	int need;
>  
>  	if (unlikely(hw->started == 0 && tx_pkts != hw->inject_pkts))
>  		return nb_tx;
> @@ -1497,14 +1513,9 @@ virtio_xmit_pkts_inorder(void *tx_queue,
>  	if (likely(nb_used > vq->vq_nentries - vq->vq_free_thresh))
>  		virtio_xmit_cleanup_inorder(vq, nb_used);
>  
> -	if (unlikely(!vq->vq_free_cnt))
> -		virtio_xmit_cleanup_inorder(vq, nb_used);
> -
> -	nb_avail = RTE_MIN(vq->vq_free_cnt, nb_pkts);
> -
> -	for (nb_tx = 0; nb_tx < nb_avail; nb_tx++) {
> +	for (nb_tx = 0; nb_tx < nb_pkts; nb_tx++) {
>  		struct rte_mbuf *txm = tx_pkts[nb_tx];
> -		int slots, need;
> +		int slots;
>  
>  		/* optimize ring usage */
>  		if ((vtpci_with_feature(hw, VIRTIO_F_ANY_LAYOUT) ||
> @@ -1524,6 +1535,17 @@ virtio_xmit_pkts_inorder(void *tx_queue,
>  		}
>  
>  		if (nb_inorder_pkts) {
> +			need = nb_inorder_pkts - vq->vq_free_cnt;
> +			if (unlikely(need > 0)) {
> +				need = virtio_xmit_try_cleanup_inorder(vq,
> +								       need);
> +				if (unlikely(need > 0)) {
> +					PMD_TX_LOG(ERR,
> +						"No free tx descriptors to "
> +						"transmit");
> +					break;
> +				}
> +			}
>  			virtqueue_enqueue_xmit_inorder(txvq, inorder_pkts,
>  							nb_inorder_pkts);
>  			nb_inorder_pkts = 0;
> @@ -1532,13 +1554,7 @@ virtio_xmit_pkts_inorder(void *tx_queue,
>  		slots = txm->nb_segs + 1;
>  		need = slots - vq->vq_free_cnt;
>  		if (unlikely(need > 0)) {
> -			nb_used = VIRTQUEUE_NUSED(vq);
> -			virtio_rmb();
> -			need = RTE_MIN(need, (int)nb_used);
> -
> -			virtio_xmit_cleanup_inorder(vq, need);
> -
> -			need = slots - vq->vq_free_cnt;
> +			need = virtio_xmit_try_cleanup_inorder(vq, slots);
>  
>  			if (unlikely(need > 0)) {
>  				PMD_TX_LOG(ERR,
> @@ -1554,9 +1570,21 @@ virtio_xmit_pkts_inorder(void *tx_queue,
>  	}
>  
>  	/* Transmit all inorder packets */
> -	if (nb_inorder_pkts)
> +	if (nb_inorder_pkts) {
> +		need = nb_inorder_pkts - vq->vq_free_cnt;
> +		if (unlikely(need > 0)) {
> +			need = virtio_xmit_try_cleanup_inorder(vq, need);
> +			if (unlikely(need > 0)) {
> +				PMD_TX_LOG(ERR,
> +					"No free tx descriptors to transmit");
> +				nb_inorder_pkts = vq->vq_free_cnt;
> +				nb_tx -= need;
> +			}
> +		}
> +
>  		virtqueue_enqueue_xmit_inorder(txvq, inorder_pkts,
>  						nb_inorder_pkts);
> +	}
>  
>  	txvq->stats.packets += nb_tx;
>  
> 

Applied, thanks.