vhost_net: basic polling support
This patch tries to poll for new added tx buffer or socket receive queue for a while at the end of tx/rx processing. The maximum time spent on polling were specified through a new kind of vring ioctl. Signed-off-by: Jason Wang <jasowang@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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0308813724
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@ -287,6 +287,43 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success)
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rcu_read_unlock_bh();
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}
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static inline unsigned long busy_clock(void)
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{
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return local_clock() >> 10;
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}
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static bool vhost_can_busy_poll(struct vhost_dev *dev,
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unsigned long endtime)
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{
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return likely(!need_resched()) &&
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likely(!time_after(busy_clock(), endtime)) &&
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likely(!signal_pending(current)) &&
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!vhost_has_work(dev);
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}
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static int vhost_net_tx_get_vq_desc(struct vhost_net *net,
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struct vhost_virtqueue *vq,
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struct iovec iov[], unsigned int iov_size,
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unsigned int *out_num, unsigned int *in_num)
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{
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unsigned long uninitialized_var(endtime);
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int r = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
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out_num, in_num, NULL, NULL);
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if (r == vq->num && vq->busyloop_timeout) {
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preempt_disable();
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endtime = busy_clock() + vq->busyloop_timeout;
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while (vhost_can_busy_poll(vq->dev, endtime) &&
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vhost_vq_avail_empty(vq->dev, vq))
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cpu_relax_lowlatency();
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preempt_enable();
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r = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
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out_num, in_num, NULL, NULL);
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}
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return r;
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}
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/* Expects to be always run from workqueue - which acts as
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* read-size critical section for our kind of RCU. */
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static void handle_tx(struct vhost_net *net)
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@ -331,10 +368,9 @@ static void handle_tx(struct vhost_net *net)
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% UIO_MAXIOV == nvq->done_idx))
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break;
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head = vhost_get_vq_desc(vq, vq->iov,
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head = vhost_net_tx_get_vq_desc(net, vq, vq->iov,
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ARRAY_SIZE(vq->iov),
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&out, &in,
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NULL, NULL);
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&out, &in);
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/* On error, stop handling until the next kick. */
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if (unlikely(head < 0))
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break;
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@ -435,6 +471,38 @@ static int peek_head_len(struct sock *sk)
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return len;
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}
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static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk)
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{
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struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];
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struct vhost_virtqueue *vq = &nvq->vq;
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unsigned long uninitialized_var(endtime);
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int len = peek_head_len(sk);
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if (!len && vq->busyloop_timeout) {
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/* Both tx vq and rx socket were polled here */
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mutex_lock(&vq->mutex);
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vhost_disable_notify(&net->dev, vq);
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preempt_disable();
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endtime = busy_clock() + vq->busyloop_timeout;
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while (vhost_can_busy_poll(&net->dev, endtime) &&
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skb_queue_empty(&sk->sk_receive_queue) &&
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vhost_vq_avail_empty(&net->dev, vq))
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cpu_relax_lowlatency();
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preempt_enable();
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if (vhost_enable_notify(&net->dev, vq))
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vhost_poll_queue(&vq->poll);
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mutex_unlock(&vq->mutex);
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len = peek_head_len(sk);
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}
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return len;
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}
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/* This is a multi-buffer version of vhost_get_desc, that works if
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* vq has read descriptors only.
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* @vq - the relevant virtqueue
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@ -553,7 +621,7 @@ static void handle_rx(struct vhost_net *net)
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vq->log : NULL;
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mergeable = vhost_has_feature(vq, VIRTIO_NET_F_MRG_RXBUF);
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while ((sock_len = peek_head_len(sock->sk))) {
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while ((sock_len = vhost_net_rx_peek_head_len(net, sock->sk))) {
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sock_len += sock_hlen;
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vhost_len = sock_len + vhost_hlen;
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headcount = get_rx_bufs(vq, vq->heads, vhost_len,
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@ -303,6 +303,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
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vq->memory = NULL;
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vhost_reset_is_le(vq);
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vhost_disable_cross_endian(vq);
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vq->busyloop_timeout = 0;
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}
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static int vhost_worker(void *data)
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@ -937,6 +938,19 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
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case VHOST_GET_VRING_ENDIAN:
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r = vhost_get_vring_endian(vq, idx, argp);
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break;
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case VHOST_SET_VRING_BUSYLOOP_TIMEOUT:
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if (copy_from_user(&s, argp, sizeof(s))) {
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r = -EFAULT;
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break;
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}
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vq->busyloop_timeout = s.num;
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break;
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case VHOST_GET_VRING_BUSYLOOP_TIMEOUT:
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s.index = idx;
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s.num = vq->busyloop_timeout;
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if (copy_to_user(argp, &s, sizeof(s)))
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r = -EFAULT;
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break;
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default:
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r = -ENOIOCTLCMD;
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}
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@ -115,6 +115,7 @@ struct vhost_virtqueue {
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/* Ring endianness requested by userspace for cross-endian support. */
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bool user_be;
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#endif
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u32 busyloop_timeout;
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};
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struct vhost_dev {
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@ -126,6 +126,12 @@ struct vhost_memory {
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#define VHOST_SET_VRING_CALL _IOW(VHOST_VIRTIO, 0x21, struct vhost_vring_file)
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/* Set eventfd to signal an error */
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#define VHOST_SET_VRING_ERR _IOW(VHOST_VIRTIO, 0x22, struct vhost_vring_file)
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/* Set busy loop timeout (in us) */
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#define VHOST_SET_VRING_BUSYLOOP_TIMEOUT _IOW(VHOST_VIRTIO, 0x23, \
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struct vhost_vring_state)
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/* Get busy loop timeout (in us) */
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#define VHOST_GET_VRING_BUSYLOOP_TIMEOUT _IOW(VHOST_VIRTIO, 0x24, \
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struct vhost_vring_state)
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/* VHOST_NET specific defines */
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