virtio_net: avoid (most) NETDEV_TX_BUSY by stopping queue early. (48925e37) · Commits · 戴 / test

drivers/net/virtio_net.c

+40 −24

Original line number	Diff line number	Diff line
		/* A simple network driver using virtio.
		/* A network driver using virtio.
		*
		* Copyright 2007 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
		*
		@@ -73,6 +73,7 @@ struct skb_vnet_hdr {
		struct virtio_net_hdr hdr;
		struct virtio_net_hdr_mrg_rxbuf mhdr;
		};
		unsigned int num_sg;
		};

		static inline struct skb_vnet_hdr skb_vnet_hdr(struct sk_buff skb)
		@@ -442,23 +443,24 @@ again:
		return received;
		}

		static void free_old_xmit_skbs(struct virtnet_info *vi)
		static unsigned int free_old_xmit_skbs(struct virtnet_info *vi)
		{
		struct sk_buff *skb;
		unsigned int len;
		unsigned int len, tot_sgs = 0;

		while ((skb = vi->svq->vq_ops->get_buf(vi->svq, &len)) != NULL) {
		pr_debug("Sent skb %p\n", skb);
		__skb_unlink(skb, &vi->send);
		vi->dev->stats.tx_bytes += skb->len;
		vi->dev->stats.tx_packets++;
		tot_sgs += skb_vnet_hdr(skb)->num_sg;
		kfree_skb(skb);
		}
		return tot_sgs;
		}

		static int xmit_skb(struct virtnet_info vi, struct sk_buff skb)
		{
		int num;
		struct scatterlist sg[2+MAX_SKB_FRAGS];
		struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
		const unsigned char dest = ((struct ethhdr )skb->data)->h_dest;
		@@ -502,13 +504,14 @@ static int xmit_skb(struct virtnet_info vi, struct sk_buff skb)
		else
		sg_set_buf(sg, &hdr->hdr, sizeof(hdr->hdr));

		num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
		return vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb);
		hdr->num_sg = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
		return vi->svq->vq_ops->add_buf(vi->svq, sg, hdr->num_sg, 0, skb);
		}

		static netdev_tx_t start_xmit(struct sk_buff skb, struct net_device dev)
		{
		struct virtnet_info *vi = netdev_priv(dev);
		int capacity;

		again:
		/* Free up any pending old buffers before queueing new ones. */
		@@ -516,27 +519,40 @@ again:

		/* Put new one in send queue and do transmit */
		__skb_queue_head(&vi->send, skb);
		if (likely(xmit_skb(vi, skb) >= 0)) {
		capacity = xmit_skb(vi, skb);

		/* This can happen with OOM and indirect buffers. */
		if (unlikely(capacity < 0)) {
		netif_stop_queue(dev);
		dev_warn(&dev->dev, "Unexpected full queue\n");
		if (unlikely(!vi->svq->vq_ops->enable_cb(vi->svq))) {
		vi->svq->vq_ops->disable_cb(vi->svq);
		netif_start_queue(dev);
		goto again;
		}
		return NETDEV_TX_BUSY;
		}

		vi->svq->vq_ops->kick(vi->svq);
		/* Don't wait up for transmitted skbs to be freed. */
		skb_orphan(skb);
		nf_reset(skb);
		return NETDEV_TX_OK;
		}

		/* Ring too full for this packet, remove it from queue again. */
		pr_debug("%s: virtio not prepared to send\n", dev->name);
		__skb_unlink(skb, &vi->send);
		/* Apparently nice girls don't return TX_BUSY; stop the queue
		* before it gets out of hand. Naturally, this wastes entries. */
		if (capacity < 2+MAX_SKB_FRAGS) {
		netif_stop_queue(dev);

		/* Activate callback for using skbs: if this returns false it
		* means some were used in the meantime. */
		if (unlikely(!vi->svq->vq_ops->enable_cb(vi->svq))) {
		vi->svq->vq_ops->disable_cb(vi->svq);
		/* More just got used, free them then recheck. */
		capacity += free_old_xmit_skbs(vi);
		if (capacity >= 2+MAX_SKB_FRAGS) {
		netif_start_queue(dev);
		goto again;
		vi->svq->vq_ops->disable_cb(vi->svq);
		}
		return NETDEV_TX_BUSY;
		}
		}

		return NETDEV_TX_OK;
		}

		static int virtnet_set_mac_address(struct net_device dev, void p)

Admin message