On 2018年08月01日 11:00, xiangxia.m.yue@xxxxxxxxx wrote:
From: Tonghao Zhang <xiangxia.m.yue@xxxxxxxxx>
Factor out generic busy polling logic and will be
used for in tx path in the next patch. And with the patch,
qemu can set differently the busyloop_timeout for rx queue.
In the handle_tx, the busypoll will vhost_net_disable/enable_vq
because we have poll the sock. This can improve performance.
[This is suggested by Toshiaki Makita <makita.toshiaki@xxxxxxxxxxxxx>]
And when the sock receive skb, we should queue the poll if necessary.
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@xxxxxxxxx>
---
drivers/vhost/net.c | 131 ++++++++++++++++++++++++++++++++++++----------------
1 file changed, 91 insertions(+), 40 deletions(-)
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 32c1b52..5b45463 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -440,6 +440,95 @@ static void vhost_net_signal_used(struct vhost_net_virtqueue *nvq)
nvq->done_idx = 0;
}
+static int sk_has_rx_data(struct sock *sk)
+{
+ struct socket *sock = sk->sk_socket;
+
+ if (sock->ops->peek_len)
+ return sock->ops->peek_len(sock);
+
+ return skb_queue_empty(&sk->sk_receive_queue);
+}
+
+static void vhost_net_busy_poll_try_queue(struct vhost_net *net,
+ struct vhost_virtqueue *vq)
+{
+ if (!vhost_vq_avail_empty(&net->dev, vq)) {
+ vhost_poll_queue(&vq->poll);
+ } else if (unlikely(vhost_enable_notify(&net->dev, vq))) {
+ vhost_disable_notify(&net->dev, vq);
+ vhost_poll_queue(&vq->poll);
+ }
+}
+
+static void vhost_net_busy_poll_check(struct vhost_net *net,
+ struct vhost_virtqueue *rvq,
+ struct vhost_virtqueue *tvq,
+ bool rx)
+{
+ struct socket *sock = rvq->private_data;
+
+ if (rx)
+ vhost_net_busy_poll_try_queue(net, tvq);
+ else if (sock && sk_has_rx_data(sock->sk))
+ vhost_net_busy_poll_try_queue(net, rvq);
+ else {
+ /* On tx here, sock has no rx data, so we
+ * will wait for sock wakeup for rx, and
+ * vhost_enable_notify() is not needed. */
A possible case is we do have rx data but guest does not refill the rx
queue. In this case we may lose notifications from guest.
+ }
+}
+
+static void vhost_net_busy_poll(struct vhost_net *net,
+ struct vhost_virtqueue *rvq,
+ struct vhost_virtqueue *tvq,
+ bool *busyloop_intr,
+ bool rx)
+{
+ unsigned long busyloop_timeout;
+ unsigned long endtime;
+ struct socket *sock;
+ struct vhost_virtqueue *vq = rx ? tvq : rvq;
+
+ mutex_lock_nested(&vq->mutex, rx ? VHOST_NET_VQ_TX: VHOST_NET_VQ_RX);
+ vhost_disable_notify(&net->dev, vq);
+ sock = rvq->private_data;
+
+ busyloop_timeout = rx ? rvq->busyloop_timeout:
+ tvq->busyloop_timeout;
+
+
+ /* Busypoll the sock, so don't need rx wakeups during it. */
+ if (!rx)
+ vhost_net_disable_vq(net, vq);
Actually this piece of code is not a factoring out. I would suggest to
add this in another patch, or on top of this series.
+
+ preempt_disable();
+ endtime = busy_clock() + busyloop_timeout;
+
+ while (vhost_can_busy_poll(endtime)) {
+ if (vhost_has_work(&net->dev)) {
+ *busyloop_intr = true;
+ break;
+ }
+
+ if ((sock && sk_has_rx_data(sock->sk) &&
+ !vhost_vq_avail_empty(&net->dev, rvq)) ||
+ !vhost_vq_avail_empty(&net->dev, tvq))
+ break;
Some checks were duplicated in vhost_net_busy_poll_check(). Need
consider to unify them.
+
+ cpu_relax();
+ }
+
+ preempt_enable();
+
+ if (!rx)
+ vhost_net_enable_vq(net, vq);
No need to enable rx virtqueue, if we are sure handle_rx() will be
called soon.
+
+ vhost_net_busy_poll_check(net, rvq, tvq, rx);
It looks to me just open code all check here is better and easier to be
reviewed.
Thanks
+
+ mutex_unlock(&vq->mutex);
+}
+
static int vhost_net_tx_get_vq_desc(struct vhost_net *net,
struct vhost_net_virtqueue *nvq,
unsigned int *out_num, unsigned int *in_num,
@@ -753,16 +842,6 @@ static int peek_head_len(struct vhost_net_virtqueue *rvq, struct sock *sk)
return len;
}
-static int sk_has_rx_data(struct sock *sk)
-{
- struct socket *sock = sk->sk_socket;
-
- if (sock->ops->peek_len)
- return sock->ops->peek_len(sock);
-
- return skb_queue_empty(&sk->sk_receive_queue);
-}
-
static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk,
bool *busyloop_intr)
{
@@ -770,41 +849,13 @@ static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk,
struct vhost_net_virtqueue *tnvq = &net->vqs[VHOST_NET_VQ_TX];
struct vhost_virtqueue *rvq = &rnvq->vq;
struct vhost_virtqueue *tvq = &tnvq->vq;
- unsigned long uninitialized_var(endtime);
int len = peek_head_len(rnvq, sk);
- if (!len && tvq->busyloop_timeout) {
+ if (!len && rvq->busyloop_timeout) {
/* Flush batched heads first */
vhost_net_signal_used(rnvq);
/* Both tx vq and rx socket were polled here */
- mutex_lock_nested(&tvq->mutex, VHOST_NET_VQ_TX);
- vhost_disable_notify(&net->dev, tvq);
-
- preempt_disable();
- endtime = busy_clock() + tvq->busyloop_timeout;
-
- 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, rvq)) ||
- !vhost_vq_avail_empty(&net->dev, tvq))
- break;
- cpu_relax();
- }
-
- preempt_enable();
-
- if (!vhost_vq_avail_empty(&net->dev, tvq)) {
- vhost_poll_queue(&tvq->poll);
- } else if (unlikely(vhost_enable_notify(&net->dev, tvq))) {
- vhost_disable_notify(&net->dev, tvq);
- vhost_poll_queue(&tvq->poll);
- }
-
- mutex_unlock(&tvq->mutex);
+ vhost_net_busy_poll(net, rvq, tvq, busyloop_intr, true);
len = peek_head_len(rnvq, sk);
}
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