From 363f15149cfba67d29f1e6a6103dda079f27f3fa Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Sun, 8 Jun 2008 20:51:55 +1000 Subject: [PATCH] virtio: use callback on empty in virtio_net virtio_net uses a timer to free old transmitted packets, rather than leaving callbacks enabled all the time. If the host promises to always notify us when the transmit ring is empty, we can free packets at that point and avoid the timer. Signed-off-by: Rusty Russell Signed-off-by: Jeff Garzik --- drivers/net/virtio_net.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 156d76fee164..4452306d5328 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -44,6 +44,7 @@ struct virtnet_info /* The skb we couldn't send because buffers were full. */ struct sk_buff *last_xmit_skb; + /* If we need to free in a timer, this is it. */ struct timer_list xmit_free_timer; /* Number of input buffers, and max we've ever had. */ @@ -51,6 +52,7 @@ struct virtnet_info /* For cleaning up after transmission. */ struct tasklet_struct tasklet; + bool free_in_tasklet; /* Receive & send queues. */ struct sk_buff_head recv; @@ -74,7 +76,7 @@ static void skb_xmit_done(struct virtqueue *svq) /* Suppress further interrupts. */ svq->vq_ops->disable_cb(svq); - /* We were waiting for more output buffers. */ + /* We were probably waiting for more output buffers. */ netif_wake_queue(vi->dev); /* Make sure we re-xmit last_xmit_skb: if there are no more packets @@ -242,6 +244,8 @@ static void free_old_xmit_skbs(struct virtnet_info *vi) } } +/* If the virtio transport doesn't always notify us when all in-flight packets + * are consumed, we fall back to using this function on a timer to free them. */ static void xmit_free(unsigned long data) { struct virtnet_info *vi = (void *)data; @@ -302,7 +306,7 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb) num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1; err = vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb); - if (!err) + if (!err && !vi->free_in_tasklet) mod_timer(&vi->xmit_free_timer, jiffies + (HZ/10)); return err; @@ -317,6 +321,8 @@ static void xmit_tasklet(unsigned long data) vi->svq->vq_ops->kick(vi->svq); vi->last_xmit_skb = NULL; } + if (vi->free_in_tasklet) + free_old_xmit_skbs(vi); netif_tx_unlock_bh(vi->dev); } @@ -457,6 +463,10 @@ static int virtnet_probe(struct virtio_device *vdev) vi->vdev = vdev; vdev->priv = vi; + /* If they give us a callback when all buffers are done, we don't need + * the timer. */ + vi->free_in_tasklet = virtio_has_feature(vdev,VIRTIO_F_NOTIFY_ON_EMPTY); + /* We expect two virtqueues, receive then send. */ vi->rvq = vdev->config->find_vq(vdev, 0, skb_recv_done); if (IS_ERR(vi->rvq)) { @@ -476,7 +486,8 @@ static int virtnet_probe(struct virtio_device *vdev) tasklet_init(&vi->tasklet, xmit_tasklet, (unsigned long)vi); - setup_timer(&vi->xmit_free_timer, xmit_free, (unsigned long)vi); + if (!vi->free_in_tasklet) + setup_timer(&vi->xmit_free_timer, xmit_free, (unsigned long)vi); err = register_netdev(dev); if (err) { @@ -515,7 +526,8 @@ static void virtnet_remove(struct virtio_device *vdev) /* Stop all the virtqueues. */ vdev->config->reset(vdev); - del_timer_sync(&vi->xmit_free_timer); + if (!vi->free_in_tasklet) + del_timer_sync(&vi->xmit_free_timer); /* Free our skbs in send and recv queues, if any. */ while ((skb = __skb_dequeue(&vi->recv)) != NULL) { @@ -540,7 +552,7 @@ static struct virtio_device_id id_table[] = { static unsigned int features[] = { VIRTIO_NET_F_CSUM, VIRTIO_NET_F_GSO, VIRTIO_NET_F_MAC, VIRTIO_NET_F_HOST_TSO4, VIRTIO_NET_F_HOST_UFO, VIRTIO_NET_F_HOST_TSO6, - VIRTIO_NET_F_HOST_ECN, + VIRTIO_NET_F_HOST_ECN, VIRTIO_F_NOTIFY_ON_EMPTY, }; static struct virtio_driver virtio_net = { -- 2.20.1