[dpdk-dev] [PATCH v2 2/2] net/virtio: on demand cleanup when doing in order xmit

[Liu, Yong]

Thanks for comments, will update in next patch.

> -----Original Message-----
> From: Bie, Tiwei
> Sent: Wednesday, September 18, 2019 10:44 AM
> To: Liu, Yong <yong.liu at intel.com>
> Cc: maxime.coquelin at redhat.com; dev at dpdk.org
> Subject: Re: [PATCH v2 2/2] net/virtio: on demand cleanup when doing in
> order xmit
> 
> On Wed, Sep 11, 2019 at 12:14:46AM +0800, Marvin Liu wrote:
> > Check whether space are enough before burst enqueue operation. If more
> > space is needed, will try to cleanup used descriptors for space on
> > demand. It can give more chances to free used descriptors, thus will
> > help RFC2544 performance.
> >
> > Signed-off-by: Marvin Liu <yong.liu at intel.com>
> > ---
> >  drivers/net/virtio/virtio_rxtx.c | 73 +++++++++++++++++++++++---------
> >  1 file changed, 54 insertions(+), 19 deletions(-)
> >
> > diff --git a/drivers/net/virtio/virtio_rxtx.c
> b/drivers/net/virtio/virtio_rxtx.c
> > index d3ca36831..842b600c3 100644
> > --- a/drivers/net/virtio/virtio_rxtx.c
> > +++ b/drivers/net/virtio/virtio_rxtx.c
> > @@ -2152,6 +2152,22 @@ 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;
> > +	struct virtio_hw *hw = vq->hw;
> > +
> > +	nb_descs = vq->vq_free_cnt + need;
> > +	nb_used = VIRTQUEUE_NUSED(vq);
> > +	virtio_rmb(hw->weak_barriers);
> > +	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,
> > @@ -2161,8 +2177,9 @@ 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, nb_left;
> >
> >  	if (unlikely(hw->started == 0 && tx_pkts != hw->inject_pkts))
> >  		return nb_tx;
> > @@ -2175,17 +2192,12 @@ virtio_xmit_pkts_inorder(void *tx_queue,
> >  	nb_used = VIRTQUEUE_NUSED(vq);
> >
> >  	virtio_rmb(hw->weak_barriers);
> > -	if (likely(nb_used > vq->vq_nentries - vq->vq_free_thresh))
> > -		virtio_xmit_cleanup_inorder(vq, nb_used);
> > -
> > -	if (unlikely(!vq->vq_free_cnt))
> > +	if (likely(nb_used > (vq->vq_nentries - vq->vq_free_thresh)))
> >  		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) ||
> > @@ -2199,11 +2211,25 @@ virtio_xmit_pkts_inorder(void *tx_queue,
> >  			inorder_pkts[nb_inorder_pkts] = txm;
> >  			nb_inorder_pkts++;
> >
> > -			virtio_update_packet_stats(&txvq->stats, txm);
> >  			continue;
> >  		}
> >
> >  		if (nb_inorder_pkts) {
> > +			need = nb_inorder_pkts - vq->vq_free_cnt;
> > +
> > +			if (unlikely(need > 0)) {
> > +				nb_left = virtio_xmit_try_cleanup_inorder(vq,
> > +									need);
> 
> There is no need to introduce `nb_left`. Looks better
> to just reuse `need`.
> 
> > +
> > +				if (unlikely(nb_left > 0)) {
> > +					PMD_TX_LOG(ERR,
> > +						"No free tx descriptors to "
> > +						"transmit");
> > +					nb_inorder_pkts = vq->vq_free_cnt;
> 
> You need to handle nb_tx as well, otherwise mbufs will leak.
> Or maybe just leave nb_inorder_pkts unchanged, and let the code
> outside the loop handle it.
> 
> 
> > +					break;
> > +				}
> > +			}
> > +
> >  			virtqueue_enqueue_xmit_inorder(txvq, inorder_pkts,
> >  							nb_inorder_pkts);
> >  			nb_inorder_pkts = 0;
> > @@ -2212,15 +2238,9 @@ 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(hw->weak_barriers);
> > -			need = RTE_MIN(need, (int)nb_used);
> > -
> > -			virtio_xmit_cleanup_inorder(vq, need);
> > +			nb_left = virtio_xmit_try_cleanup_inorder(vq, slots);
> >
> > -			need = slots - vq->vq_free_cnt;
> > -
> > -			if (unlikely(need > 0)) {
> > +			if (unlikely(nb_left > 0)) {
> >  				PMD_TX_LOG(ERR,
> >  					"No free tx descriptors to transmit");
> >  				break;
> > @@ -2233,9 +2253,24 @@ 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)) {
> > +			nb_left = virtio_xmit_try_cleanup_inorder(vq,
> > +								  need);
> > +
> > +			if (unlikely(nb_left > 0)) {
> > +				PMD_TX_LOG(ERR,
> > +					"No free tx descriptors to transmit");
> > +				nb_inorder_pkts = vq->vq_free_cnt;
> > +				nb_tx -= nb_left;
> > +			}
> > +		}
> > +
> >  		virtqueue_enqueue_xmit_inorder(txvq, inorder_pkts,
> >  						nb_inorder_pkts);
> > +	}
> >
> >  	txvq->stats.packets += nb_tx;
> >
> > --
> > 2.17.1
> >