From c1e1126c39fe107f68adec196d4e558a14540939 Mon Sep 17 00:00:00 2001
From: Anthony Liguori <aliguori@xxxxxxxxxx>
Date: Mon, 12 Nov 2007 21:30:26 -0600
Subject: [PATCH] virtio: use an hrtimer for tx coalescing.
Not sure why hrtimer's cb_mode only exists with CONFIG_HIGH_RES_TIMERS; that
seems like a bug to me.
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
---
drivers/net/virtio_net.c | 41 ++++++++++++++++++++++++++++++++++++++++-
1 files changed, 40 insertions(+), 1 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index aff25b0..6526e0b 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -23,6 +23,7 @@
#include <linux/virtio.h>
#include <linux/virtio_net.h>
#include <linux/scatterlist.h>
+#include <linux/hrtimer.h>
/* FIXME: MTU in config. */
#define MAX_PACKET_LEN (ETH_HLEN+ETH_DATA_LEN)
@@ -34,9 +35,15 @@ 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;
@@ -223,6 +230,20 @@ static void free_old_xmit_skbs(struct virtnet_info *vi)
}
}
+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);
@@ -273,11 +294,25 @@ static int start_xmit(struct sk_buff *skb, struct
net_device *dev)
if (err) {
pr_debug("%s: virtio not prepared to send\n", dev->name);
skb_unlink(skb, &vi->send);
+ 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);
return NETDEV_TX_BUSY;
}
- vi->svq->vq_ops->kick(vi->svq);
+ if (++vi->out_num == vi->out_max) {
+ hrtimer_cancel(&vi->tx_timer);
+ vi->svq->vq_ops->kick(vi->svq);
+ vi->out_num = 0;
+ } else
+ hrtimer_start(&vi->tx_timer, ktime_set(0,500000),
+ HRTIMER_MODE_REL);
return 0;
}
@@ -363,6 +398,10 @@ static int virtnet_probe(struct virtio_device *vdev)
netif_napi_add(dev, &vi->napi, virtnet_poll, 16);
vi->dev = dev;
vi->vdev = vdev;
+ hrtimer_init(&vi->tx_timer, CLOCK_REALTIME, HRTIMER_MODE_REL);
+ vi->tx_timer.function = kick_xmit;
+ vi->tx_timer.cb_mode = HRTIMER_CB_SOFTIRQ;
+ vi->out_max = -1U;
/* We expect two virtqueues, receive then send. */
vi->rvq = vdev->config->find_vq(vdev, 0, skb_recv_done);
--
1.5.3.3
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