[PATCH 1/3] Remove the TX timer from virtio_net

Anthony Liguori
2008-01-07T21:41:28Z

Doing tx mitigation in the host gets equivalent performance and offers greater
flexibility. It also simplifies the guest code.

Signed-off-by: Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 4082099..797a3ed 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -23,7 +23,6 @@
#include <linux/virtio.h>
#include <linux/virtio_net.h>
#include <linux/scatterlist.h>
-#include <linux/hrtimer.h>

static int napi_weight = 128;
module_param(napi_weight, int, 0444);
@@ -40,15 +39,9 @@ struct virtnet_info
struct net_device *dev;
struct napi_struct napi;

- /* TX coalescing. */
- struct hrtimer tx_timer;
-
/* Number of input buffers, and max we've ever had. */
unsigned int num, max;

- /* Number of queued output buffers, and max we've ever had. */
- unsigned int out_num, out_max;
-
/* Receive & send queues. */
struct sk_buff_head recv;
struct sk_buff_head send;
@@ -238,20 +231,6 @@ again:
return received;
}

-static enum hrtimer_restart kick_xmit(struct hrtimer *t)
-{
- struct virtnet_info *vi = container_of(t,struct virtnet_info,tx_timer);
-
- BUG_ON(!in_softirq());
- BUG_ON(in_irq());
- netif_tx_lock(vi->dev);
- vi->svq->vq_ops->kick(vi->svq);
- vi->out_num = 0;
- netif_tx_unlock(vi->dev);
-
- return HRTIMER_NORESTART;
-}
-
static int start_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct virtnet_info *vi = netdev_priv(dev);
@@ -305,13 +284,8 @@ again:
goto again;

pr_debug("%s: virtio not prepared to send\n", dev->name);
- if (vi->out_max != vi->out_num)
- printk("%s: out_max changed from %u to %u\n",
- dev->name, vi->out_max, vi->out_num);
- vi->out_max = vi->out_num;
- vi->out_num = 0;
+
/* Kick off send immediately. */
- hrtimer_cancel(&vi->tx_timer);
vi->svq->vq_ops->kick(vi->svq);
netif_stop_queue(dev);

@@ -327,13 +301,8 @@ again:
return NETDEV_TX_BUSY;
}

- if (++vi->out_num == vi->out_max) {
- hrtimer_cancel(&vi->tx_timer);
- vi->svq->vq_ops->kick(vi->svq);
- vi->out_num = 0;
- } else if (!hrtimer_is_queued(&vi->tx_timer))
- hrtimer_start(&vi->tx_timer, ktime_set(0,500000),
- HRTIMER_MODE_REL);
+ vi->svq->vq_ops->kick(vi->svq);
+
return 0;
}

@@ -425,10 +394,6 @@ static int virtnet_probe(struct virtio_device *vdev)
netif_napi_add(dev, &vi->napi, virtnet_poll, napi_weight);
vi->dev = dev;
vi->vdev = vdev;
- memset(&vi->tx_timer, 0, sizeof(vi->tx_timer));
- hrtimer_init(&vi->tx_timer, CLOCK_REALTIME, HRTIMER_MODE_REL);
- vi->tx_timer.function = kick_xmit;
- vi->out_max = -1U;

/* We expect two virtqueues, receive then send. */
vi->rvq = vdev->config->find_vq(vdev, 0, skb_recv_done);