On 2018年07月03日 15:31, Toshiaki Makita wrote:
We may run handle_rx() while rx work is queued. For example a packet can
push the rx work during the window before handle_rx calls
vhost_net_disable_vq().
In that case busypoll immediately exits due to vhost_has_work()
condition and enables vq again. This can lead to another unnecessary rx
wake-ups, so poll rx work instead of enabling the vq.
Signed-off-by: Toshiaki Makita <[email protected]>
---
drivers/vhost/net.c | 26 +++++++++++++++++++-------
1 file changed, 19 insertions(+), 7 deletions(-)
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 811c0e5..791bc8b 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -653,7 +653,8 @@ static void vhost_rx_signal_used(struct vhost_net_virtqueue
*nvq)
nvq->done_idx = 0;
}
-static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk)
+static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk,
+ bool *busyloop_intr)
{
struct vhost_net_virtqueue *rnvq = &net->vqs[VHOST_NET_VQ_RX];
struct vhost_net_virtqueue *tnvq = &net->vqs[VHOST_NET_VQ_TX];
@@ -671,11 +672,16 @@ static int vhost_net_rx_peek_head_len(struct vhost_net
*net, struct sock *sk)
preempt_disable();
endtime = busy_clock() + tvq->busyloop_timeout;
- while (vhost_can_busy_poll(endtime) &&
- !vhost_has_work(&net->dev) &&
- !sk_has_rx_data(sk) &&
- vhost_vq_avail_empty(&net->dev, tvq))
+ while (vhost_can_busy_poll(endtime)) {
+ if (vhost_has_work(&net->dev)) {
+ *busyloop_intr = true;
+ break;
+ }
+ if (sk_has_rx_data(sk) ||
+ !vhost_vq_avail_empty(&net->dev, tvq))
+ break;
cpu_relax();
+ }
preempt_enable();
@@ -795,6 +801,7 @@ static void handle_rx(struct vhost_net *net)
s16 headcount;
size_t vhost_hlen, sock_hlen;
size_t vhost_len, sock_len;
+ bool busyloop_intr = false;
struct socket *sock;
struct iov_iter fixup;
__virtio16 num_buffers;
@@ -818,7 +825,9 @@ static void handle_rx(struct vhost_net *net)
vq->log : NULL;
mergeable = vhost_has_feature(vq, VIRTIO_NET_F_MRG_RXBUF);
- while ((sock_len = vhost_net_rx_peek_head_len(net, sock->sk))) {
+ while ((sock_len = vhost_net_rx_peek_head_len(net, sock->sk,
+ &busyloop_intr))) {
+ busyloop_intr = false;
sock_len += sock_hlen;
vhost_len = sock_len + vhost_hlen;
headcount = get_rx_bufs(vq, vq->heads + nvq->done_idx,
@@ -905,7 +914,10 @@ static void handle_rx(struct vhost_net *net)
goto out;
}
}
- vhost_net_enable_vq(net, vq);
+ if (unlikely(busyloop_intr))
+ vhost_poll_queue(&vq->poll);
+ else
+ vhost_net_enable_vq(net, vq);
out:
vhost_rx_signal_used(nvq);
mutex_unlock(&vq->mutex);
Acked-by: Jason Wang <[email protected]>
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