2010-02-09 00:14:49

by Shirley Ma

Subject: [PATCH 1/1 net-next] virtio_net: remove send queue

Now we have a virtio detach API (in commit
f9bfbebf34eab707b065116cdc9699d25ba4252a), we don't need to track xmit
skbs in the virio_net driver, which improves transmission performance.

Signed-off-by: Shirley Ma <[email protected]>
Acked-by: Rusty Russell <[email protected]>
Acked-by: Michael S. Tsirkin <[email protected]>
---
drivers/net/virtio_net.c | 26 ++++++++------------------
1 files changed, 8 insertions(+), 18 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 9d8984a..8069c08 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -56,9 +56,6 @@ struct virtnet_info
/* Host will merge rx buffers for big packets (shake it! shake it!) */
bool mergeable_rx_bufs;

- /* Send queue. */
- struct sk_buff_head send;
-
/* Work struct for refilling if we run low on memory. */
struct delayed_work refill;

@@ -505,7 +502,6 @@ static unsigned int free_old_xmit_skbs(struct virtnet_info *vi)

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;
@@ -588,15 +584,6 @@ again:
}
vi->svq->vq_ops->kick(vi->svq);

- /*
- * Put new one in send queue. You'd expect we'd need this before
- * xmit_skb calls add_buf(), since the callback can be triggered
- * immediately after that. But since the callback just triggers
- * another call back here, normal network xmit locking prevents the
- * race.
- */
- __skb_queue_head(&vi->send, skb);
-
/* Don't wait up for transmitted skbs to be freed. */
skb_orphan(skb);
nf_reset(skb);
@@ -977,9 +964,6 @@ static int virtnet_probe(struct virtio_device *vdev)
dev->features |= NETIF_F_HW_VLAN_FILTER;
}

- /* Initialize our empty send queue. */
- skb_queue_head_init(&vi->send);
-
err = register_netdev(dev);
if (err) {
pr_debug("virtio_net: registering device failed\n");
@@ -1016,6 +1000,12 @@ static void free_unused_bufs(struct virtnet_info *vi)
{
void *buf;
while (1) {
+ buf = vi->svq->vq_ops->detach_unused_buf(vi->svq);
+ if (!buf)
+ break;
+ dev_kfree_skb(buf);
+ }
+ while (1) {
buf = vi->rvq->vq_ops->detach_unused_buf(vi->rvq);
if (!buf)
break;
@@ -1035,11 +1025,11 @@ static void __devexit virtnet_remove(struct virtio_device *vdev)
/* Stop all the virtqueues. */
vdev->config->reset(vdev);

- /* Free our skbs in send queue, if any. */
- __skb_queue_purge(&vi->send);

unregister_netdev(vi->dev);
cancel_delayed_work_sync(&vi->refill);
+
+ /* Free unused buffers in both send and recv, if any. */
free_unused_bufs(vi);

vdev->config->del_vqs(vi->vdev);

2010-02-10 16:54:37

by Shirley Ma

Subject: Re: [PATCH 1/1 net-next] virtio_net: remove send queue

netperf results showed about 20% transmission gain with this patch for
virtio_net.

Thanks
Shirley

2010-02-12 20:28:13

by David Miller

Subject: Re: [PATCH 1/1 net-next] virtio_net: remove send queue

From: Shirley Ma <[email protected]>
Date: Mon, 08 Feb 2010 16:14:42 -0800

> Now we have a virtio detach API (in commit
> f9bfbebf34eab707b065116cdc9699d25ba4252a), we don't need to track xmit
> skbs in the virio_net driver, which improves transmission performance.
>
> Signed-off-by: Shirley Ma <[email protected]>
> Acked-by: Rusty Russell <[email protected]>
> Acked-by: Michael S. Tsirkin <[email protected]>

Applied to net-next-2.6, thanks everyone.