On Tue, Mar 16, 2010 at 05:32:17PM +0800, Xin Xiaohui wrote:
> The vhost-net backend now only supports synchronous send/recv
> operations. The patch provides multiple submits and asynchronous
> notifications. This is needed for zero-copy case.
>
> Signed-off-by: Xin Xiaohui <xiaohui.xin@xxxxxxxxx>
> ---
>
> Michael,
> I don't use the kiocb comes from the sendmsg/recvmsg,
> since I have embeded the kiocb in page_info structure,
> and allocate it when page_info allocated.
So what I suggested was that vhost allocates and tracks the iocbs, and
passes them to your device with sendmsg/ recvmsg calls. This way your
device won't need to share structures and locking strategy with vhost:
you get an iocb, handle it, invoke a callback to notify vhost about
completion.
This also gets rid of the 'receiver' callback.
> Please have a review and thanks for the instruction
> for replying email which helps me a lot.
>
> Thanks,
> Xiaohui
>
> drivers/vhost/net.c | 159 +++++++++++++++++++++++++++++++++++++++++++++++--
> drivers/vhost/vhost.h | 12 ++++
> 2 files changed, 166 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 22d5fef..5483848 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -17,11 +17,13 @@
> #include <linux/workqueue.h>
> #include <linux/rcupdate.h>
> #include <linux/file.h>
> +#include <linux/aio.h>
>
> #include <linux/net.h>
> #include <linux/if_packet.h>
> #include <linux/if_arp.h>
> #include <linux/if_tun.h>
> +#include <linux/mpassthru.h>
>
> #include <net/sock.h>
>
> @@ -91,6 +93,12 @@ static void tx_poll_start(struct vhost_net *net, struct socket *sock)
> net->tx_poll_state = VHOST_NET_POLL_STARTED;
> }
>
> +static void handle_async_rx_events_notify(struct vhost_net *net,
> + struct vhost_virtqueue *vq);
> +
> +static void handle_async_tx_events_notify(struct vhost_net *net,
> + struct vhost_virtqueue *vq);
> +
A couple of style comments:
- It's better to arrange functions in such order that forward declarations
aren't necessary. Since we don't have recursion, this should always be
possible.
- continuation lines should be idented at least at the position of '('
on the previous line.
> /* 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)
> @@ -124,6 +132,8 @@ static void handle_tx(struct vhost_net *net)
> tx_poll_stop(net);
> hdr_size = vq->hdr_size;
>
> + handle_async_tx_events_notify(net, vq);
> +
> for (;;) {
> head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
> ARRAY_SIZE(vq->iov),
> @@ -151,6 +161,12 @@ static void handle_tx(struct vhost_net *net)
> /* Skip header. TODO: support TSO. */
> s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, out);
> msg.msg_iovlen = out;
> +
> + if (vq->link_state == VHOST_VQ_LINK_ASYNC) {
> + vq->head = head;
> + msg.msg_control = (void *)vq;
So here a device gets a pointer to vhost_virtqueue structure. If it gets
an iocb and invokes a callback, it would not care about vhost internals.
> + }
> +
> len = iov_length(vq->iov, out);
> /* Sanity check */
> if (!len) {
> @@ -166,6 +182,10 @@ static void handle_tx(struct vhost_net *net)
> tx_poll_start(net, sock);
> break;
> }
> +
> + if (vq->link_state == VHOST_VQ_LINK_ASYNC)
> + continue;
> +
> if (err != len)
> pr_err("Truncated TX packet: "
> " len %d != %zd\n", err, len);
> @@ -177,6 +197,8 @@ static void handle_tx(struct vhost_net *net)
> }
> }
>
> + handle_async_tx_events_notify(net, vq);
> +
> mutex_unlock(&vq->mutex);
> unuse_mm(net->dev.mm);
> }
> @@ -206,7 +228,8 @@ static void handle_rx(struct vhost_net *net)
> int err;
> size_t hdr_size;
> struct socket *sock = rcu_dereference(vq->private_data);
> - if (!sock || skb_queue_empty(&sock->sk->sk_receive_queue))
> + if (!sock || (skb_queue_empty(&sock->sk->sk_receive_queue) &&
> + vq->link_state == VHOST_VQ_LINK_SYNC))
> return;
>
> use_mm(net->dev.mm);
> @@ -214,9 +237,18 @@ static void handle_rx(struct vhost_net *net)
> vhost_disable_notify(vq);
> hdr_size = vq->hdr_size;
>
> - vq_log = unlikely(vhost_has_feature(&net->dev, VHOST_F_LOG_ALL)) ?
> + /* In async cases, for write logging, the simple way is to get
> + * the log info always, and really logging is decided later.
> + * Thus, when logging enabled, we can get log, and when logging
> + * disabled, we can get log disabled accordingly.
> + */
> +
This adds overhead and might be one of the reasons
your patch does not perform that well. A better way
would be to flush outstanding requests or reread the vq
when logging is enabled.
> + vq_log = unlikely(vhost_has_feature(&net->dev, VHOST_F_LOG_ALL)) |
> + (vq->link_state == VHOST_VQ_LINK_ASYNC) ?
> vq->log : NULL;
>
> + handle_async_rx_events_notify(net, vq);
> +
> for (;;) {
> head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
> ARRAY_SIZE(vq->iov),
> @@ -245,6 +277,11 @@ static void handle_rx(struct vhost_net *net)
> s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, in);
> msg.msg_iovlen = in;
> len = iov_length(vq->iov, in);
> + if (vq->link_state == VHOST_VQ_LINK_ASYNC) {
> + vq->head = head;
> + vq->_log = log;
> + msg.msg_control = (void *)vq;
> + }
> /* Sanity check */
> if (!len) {
> vq_err(vq, "Unexpected header len for RX: "
> @@ -259,6 +296,10 @@ static void handle_rx(struct vhost_net *net)
> vhost_discard_vq_desc(vq);
> break;
> }
> +
> + if (vq->link_state == VHOST_VQ_LINK_ASYNC)
> + continue;
> +
> /* TODO: Should check and handle checksum. */
> if (err > len) {
> pr_err("Discarded truncated rx packet: "
> @@ -284,10 +325,85 @@ static void handle_rx(struct vhost_net *net)
> }
> }
>
> + handle_async_rx_events_notify(net, vq);
> +
> mutex_unlock(&vq->mutex);
> unuse_mm(net->dev.mm);
> }
>
> +struct kiocb *notify_dequeue(struct vhost_virtqueue *vq)
> +{
> + struct kiocb *iocb = NULL;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&vq->notify_lock, flags);
> + if (!list_empty(&vq->notifier)) {
> + iocb = list_first_entry(&vq->notifier,
> + struct kiocb, ki_list);
> + list_del(&iocb->ki_list);
> + }
> + spin_unlock_irqrestore(&vq->notify_lock, flags);
> + return iocb;
> +}
> +
> +static void handle_async_rx_events_notify(struct vhost_net *net,
> + struct vhost_virtqueue *vq)
> +{
> + struct kiocb *iocb = NULL;
> + struct vhost_log *vq_log = NULL;
> + int rx_total_len = 0;
> + int log, size;
> +
> + if (vq->link_state != VHOST_VQ_LINK_ASYNC)
> + return;
> + if (vq != &net->dev.vqs[VHOST_NET_VQ_RX])
> + return;
> +
> + if (vq->receiver)
> + vq->receiver(vq);
> + vq_log = unlikely(vhost_has_feature(
> + &net->dev, VHOST_F_LOG_ALL)) ? vq->log : NULL;
> + while ((iocb = notify_dequeue(vq)) != NULL) {
> + vhost_add_used_and_signal(&net->dev, vq,
> + iocb->ki_pos, iocb->ki_nbytes);
> + log = (int)iocb->ki_user_data;
> + size = iocb->ki_nbytes;
> + rx_total_len += iocb->ki_nbytes;
> + if (iocb->ki_dtor)
> + iocb->ki_dtor(iocb);
> + if (unlikely(vq_log))
> + vhost_log_write(vq, vq_log, log, size);
> + if (unlikely(rx_total_len >= VHOST_NET_WEIGHT)) {
> + vhost_poll_queue(&vq->poll);
> + break;
> + }
> + }
> +}
> +
> +static void handle_async_tx_events_notify(struct vhost_net *net,
> + struct vhost_virtqueue *vq)
> +{
> + struct kiocb *iocb = NULL;
> + int tx_total_len = 0;
> +
> + if (vq->link_state != VHOST_VQ_LINK_ASYNC)
> + return;
> + if (vq != &net->dev.vqs[VHOST_NET_VQ_TX])
> + return;
> +
Hard to see why the second check would be necessary
> + while ((iocb = notify_dequeue(vq)) != NULL) {
> + vhost_add_used_and_signal(&net->dev, vq,
> + iocb->ki_pos, 0);
> + tx_total_len += iocb->ki_nbytes;
> + if (iocb->ki_dtor)
> + iocb->ki_dtor(iocb);
> + if (unlikely(tx_total_len >= VHOST_NET_WEIGHT)) {
> + vhost_poll_queue(&vq->poll);
> + break;
> + }
> + }
> +}
> +
> static void handle_tx_kick(struct work_struct *work)
> {
> struct vhost_virtqueue *vq;
> @@ -462,7 +578,19 @@ static struct socket *get_tun_socket(int fd)
> return sock;
> }
>
> -static struct socket *get_socket(int fd)
> +static struct socket *get_mp_socket(int fd)
> +{
> + struct file *file = fget(fd);
> + struct socket *sock;
> + if (!file)
> + return ERR_PTR(-EBADF);
> + sock = mp_get_socket(file);
> + if (IS_ERR(sock))
> + fput(file);
> + return sock;
> +}
> +
> +static struct socket *get_socket(struct vhost_virtqueue *vq, int fd)
> {
> struct socket *sock;
> if (fd == -1)
> @@ -473,9 +601,26 @@ static struct socket *get_socket(int fd)
> sock = get_tun_socket(fd);
> if (!IS_ERR(sock))
> return sock;
> + sock = get_mp_socket(fd);
> + if (!IS_ERR(sock)) {
> + vq->link_state = VHOST_VQ_LINK_ASYNC;
> + return sock;
> + }
> return ERR_PTR(-ENOTSOCK);
> }
>
> +static void vhost_init_link_state(struct vhost_net *n, int index)
> +{
> + struct vhost_virtqueue *vq = n->vqs + index;
> +
> + WARN_ON(!mutex_is_locked(&vq->mutex));
> + if (vq->link_state == VHOST_VQ_LINK_ASYNC) {
> + vq->receiver = NULL;
> + INIT_LIST_HEAD(&vq->notifier);
> + spin_lock_init(&vq->notify_lock);
> + }
> +}
> +
> static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
> {
> struct socket *sock, *oldsock;
> @@ -493,12 +638,15 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
> }
> vq = n->vqs + index;
> mutex_lock(&vq->mutex);
> - sock = get_socket(fd);
> + vq->link_state = VHOST_VQ_LINK_SYNC;
> + sock = get_socket(vq, fd);
> if (IS_ERR(sock)) {
> r = PTR_ERR(sock);
> goto err;
> }
>
> + vhost_init_link_state(n, index);
> +
> /* start polling new socket */
> oldsock = vq->private_data;
> if (sock == oldsock)
> @@ -507,8 +655,8 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
> vhost_net_disable_vq(n, vq);
> rcu_assign_pointer(vq->private_data, sock);
> vhost_net_enable_vq(n, vq);
> - mutex_unlock(&vq->mutex);
> done:
> + mutex_unlock(&vq->mutex);
> mutex_unlock(&n->dev.mutex);
> if (oldsock) {
> vhost_net_flush_vq(n, index);
> @@ -516,6 +664,7 @@ done:
> }
> return r;
> err:
> + mutex_unlock(&vq->mutex);
> mutex_unlock(&n->dev.mutex);
> return r;
> }
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index d1f0453..297af1c 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -43,6 +43,11 @@ struct vhost_log {
> u64 len;
> };
>
> +enum vhost_vq_link_state {
> + VHOST_VQ_LINK_SYNC = 0,
> + VHOST_VQ_LINK_ASYNC = 1,
> +};
> +
> /* The virtqueue structure describes a queue attached to a device. */
> struct vhost_virtqueue {
> struct vhost_dev *dev;
> @@ -96,6 +101,13 @@ struct vhost_virtqueue {
> /* Log write descriptors */
> void __user *log_base;
> struct vhost_log log[VHOST_NET_MAX_SG];
> + /*Differiate async socket for 0-copy from normal*/
> + enum vhost_vq_link_state link_state;
> + int head;
> + int _log;
> + struct list_head notifier;
> + spinlock_t notify_lock;
> + void (*receiver)(struct vhost_virtqueue *);
> };
>
> struct vhost_dev {
> --
> 1.5.4.4
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