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Commit 03088137 authored by Jason Wang's avatar Jason Wang Committed by Michael S. Tsirkin
Browse files

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: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent d4a60603

drivers/vhost/net.c

+73 −5
Original line number Diff line number Diff line
@@ -287,6 +287,43 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success) 
	rcu_read_unlock_bh();

}



static inline unsigned long busy_clock(void)

{

	return local_clock() >> 10;

}



static bool vhost_can_busy_poll(struct vhost_dev *dev,

				unsigned long endtime)

{

	return likely(!need_resched()) &&

	       likely(!time_after(busy_clock(), endtime)) &&

	       likely(!signal_pending(current)) &&

	       !vhost_has_work(dev);

}



static int vhost_net_tx_get_vq_desc(struct vhost_net *net,

				    struct vhost_virtqueue *vq,

				    struct iovec iov[], unsigned int iov_size,

				    unsigned int *out_num, unsigned int *in_num)

{

	unsigned long uninitialized_var(endtime);

	int r = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),

				    out_num, in_num, NULL, NULL);



	if (r == vq->num && vq->busyloop_timeout) {

		preempt_disable();

		endtime = busy_clock() + vq->busyloop_timeout;

		while (vhost_can_busy_poll(vq->dev, endtime) &&

		       vhost_vq_avail_empty(vq->dev, vq))

			cpu_relax_lowlatency();

		preempt_enable();

		r = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),

					out_num, in_num, NULL, NULL);

	}



	return r;

}



/* Expects to be always run from workqueue - which acts as

 * read-size critical section for our kind of RCU. */

static void handle_tx(struct vhost_net *net)
@@ -331,10 +368,9 @@ static void handle_tx(struct vhost_net *net) 
			      % UIO_MAXIOV == nvq->done_idx))

			break;



		head = vhost_get_vq_desc(vq, vq->iov,

		head = vhost_net_tx_get_vq_desc(net, vq, vq->iov,

						ARRAY_SIZE(vq->iov),

					 &out, &in,

					 NULL, NULL);

						&out, &in);

		/* On error, stop handling until the next kick. */

		if (unlikely(head < 0))

			break;
@@ -435,6 +471,38 @@ static int peek_head_len(struct sock *sk) 
	return len;

}



static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk)

{

	struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];

	struct vhost_virtqueue *vq = &nvq->vq;

	unsigned long uninitialized_var(endtime);

	int len = peek_head_len(sk);



	if (!len && vq->busyloop_timeout) {

		/* Both tx vq and rx socket were polled here */

		mutex_lock(&vq->mutex);

		vhost_disable_notify(&net->dev, vq);



		preempt_disable();

		endtime = busy_clock() + vq->busyloop_timeout;



		while (vhost_can_busy_poll(&net->dev, endtime) &&

		       skb_queue_empty(&sk->sk_receive_queue) &&

		       vhost_vq_avail_empty(&net->dev, vq))

			cpu_relax_lowlatency();



		preempt_enable();



		if (vhost_enable_notify(&net->dev, vq))

			vhost_poll_queue(&vq->poll);

		mutex_unlock(&vq->mutex);



		len = peek_head_len(sk);

	}



	return len;

}



/* This is a multi-buffer version of vhost_get_desc, that works if

 *	vq has read descriptors only.

 * @vq		- the relevant virtqueue
@@ -553,7 +621,7 @@ static void handle_rx(struct vhost_net *net) 
		vq->log : NULL;

	mergeable = vhost_has_feature(vq, VIRTIO_NET_F_MRG_RXBUF);



	while ((sock_len = peek_head_len(sock->sk))) {

	while ((sock_len = vhost_net_rx_peek_head_len(net, sock->sk))) {

		sock_len += sock_hlen;

		vhost_len = sock_len + vhost_hlen;

		headcount = get_rx_bufs(vq, vq->heads, vhost_len,

drivers/vhost/vhost.c

+14 −0
Original line number Diff line number Diff line
@@ -303,6 +303,7 @@ static void vhost_vq_reset(struct vhost_dev *dev, 
	vq->memory = NULL;

	vhost_reset_is_le(vq);

	vhost_disable_cross_endian(vq);

	vq->busyloop_timeout = 0;

}



static int vhost_worker(void *data)
@@ -937,6 +938,19 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp) 
	case VHOST_GET_VRING_ENDIAN:

		r = vhost_get_vring_endian(vq, idx, argp);

		break;

	case VHOST_SET_VRING_BUSYLOOP_TIMEOUT:

		if (copy_from_user(&s, argp, sizeof(s))) {

			r = -EFAULT;

			break;

		}

		vq->busyloop_timeout = s.num;

		break;

	case VHOST_GET_VRING_BUSYLOOP_TIMEOUT:

		s.index = idx;

		s.num = vq->busyloop_timeout;

		if (copy_to_user(argp, &s, sizeof(s)))

			r = -EFAULT;

		break;

	default:

		r = -ENOIOCTLCMD;

	}

drivers/vhost/vhost.h

+1 −0
Original line number Diff line number Diff line
@@ -115,6 +115,7 @@ struct vhost_virtqueue { 
	/* Ring endianness requested by userspace for cross-endian support. */

	bool user_be;

#endif

	u32 busyloop_timeout;

};



struct vhost_dev {

include/uapi/linux/vhost.h

+6 −0
Original line number Diff line number Diff line
@@ -126,6 +126,12 @@ struct vhost_memory { 
#define VHOST_SET_VRING_CALL _IOW(VHOST_VIRTIO, 0x21, struct vhost_vring_file)

/* Set eventfd to signal an error */

#define VHOST_SET_VRING_ERR _IOW(VHOST_VIRTIO, 0x22, struct vhost_vring_file)

/* Set busy loop timeout (in us) */

#define VHOST_SET_VRING_BUSYLOOP_TIMEOUT _IOW(VHOST_VIRTIO, 0x23,	\

					 struct vhost_vring_state)

/* Get busy loop timeout (in us) */

#define VHOST_GET_VRING_BUSYLOOP_TIMEOUT _IOW(VHOST_VIRTIO, 0x24,	\

					 struct vhost_vring_state)



/* VHOST_NET specific defines */