From 0d20bdf34dc7d6aeaa04f762be3e313bc4fa1b02 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Fri, 20 Jul 2018 08:15:18 +0800 Subject: [PATCH] vhost_net: split out datacopy logic Instead of mixing zerocopy and datacopy logics, this patch tries to split datacopy logic out. This results for a more compact code and ad-hoc optimization could be done on top more easily. Signed-off-by: Jason Wang Signed-off-by: David S. Miller --- drivers/vhost/net.c | 110 ++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 90 insertions(+), 20 deletions(-) diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index f59b615..9cef0b2 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -520,9 +520,7 @@ static bool tx_can_batch(struct vhost_virtqueue *vq, size_t total_len) !vhost_vq_avail_empty(vq->dev, vq); } -/* 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) +static void handle_tx_copy(struct vhost_net *net, struct socket *sock) { struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX]; struct vhost_virtqueue *vq = &nvq->vq; @@ -537,30 +535,76 @@ static void handle_tx(struct vhost_net *net) }; size_t len, total_len = 0; int err; - struct socket *sock; - struct vhost_net_ubuf_ref *uninitialized_var(ubufs); - bool zcopy, zcopy_used; int sent_pkts = 0; - mutex_lock(&vq->mutex); - sock = vq->private_data; - if (!sock) - goto out; + for (;;) { + bool busyloop_intr = false; - if (!vq_iotlb_prefetch(vq)) - goto out; + head = get_tx_bufs(net, nvq, &msg, &out, &in, &len, + &busyloop_intr); + /* On error, stop handling until the next kick. */ + if (unlikely(head < 0)) + break; + /* Nothing new? Wait for eventfd to tell us they refilled. */ + if (head == vq->num) { + if (unlikely(busyloop_intr)) { + vhost_poll_queue(&vq->poll); + } else if (unlikely(vhost_enable_notify(&net->dev, + vq))) { + vhost_disable_notify(&net->dev, vq); + continue; + } + break; + } - vhost_disable_notify(&net->dev, vq); - vhost_net_disable_vq(net, vq); + total_len += len; + if (tx_can_batch(vq, total_len)) + msg.msg_flags |= MSG_MORE; + else + msg.msg_flags &= ~MSG_MORE; + + /* TODO: Check specific error and bomb out unless ENOBUFS? */ + err = sock->ops->sendmsg(sock, &msg, len); + if (unlikely(err < 0)) { + vhost_discard_vq_desc(vq, 1); + vhost_net_enable_vq(net, vq); + break; + } + if (err != len) + pr_debug("Truncated TX packet: len %d != %zd\n", + err, len); + vhost_add_used_and_signal(&net->dev, vq, head, 0); + if (vhost_exceeds_weight(++sent_pkts, total_len)) { + vhost_poll_queue(&vq->poll); + break; + } + } +} - zcopy = nvq->ubufs; +static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock) +{ + struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX]; + struct vhost_virtqueue *vq = &nvq->vq; + unsigned out, in; + int head; + struct msghdr msg = { + .msg_name = NULL, + .msg_namelen = 0, + .msg_control = NULL, + .msg_controllen = 0, + .msg_flags = MSG_DONTWAIT, + }; + size_t len, total_len = 0; + int err; + struct vhost_net_ubuf_ref *uninitialized_var(ubufs); + bool zcopy_used; + int sent_pkts = 0; for (;;) { bool busyloop_intr; /* Release DMAs done buffers first */ - if (zcopy) - vhost_zerocopy_signal_used(net, vq); + vhost_zerocopy_signal_used(net, vq); busyloop_intr = false; head = get_tx_bufs(net, nvq, &msg, &out, &in, &len, @@ -579,9 +623,9 @@ static void handle_tx(struct vhost_net *net) break; } - zcopy_used = zcopy && len >= VHOST_GOODCOPY_LEN - && !vhost_exceeds_maxpend(net) - && vhost_net_tx_select_zcopy(net); + zcopy_used = len >= VHOST_GOODCOPY_LEN + && !vhost_exceeds_maxpend(net) + && vhost_net_tx_select_zcopy(net); /* use msg_control to pass vhost zerocopy ubuf info to skb */ if (zcopy_used) { @@ -636,6 +680,32 @@ static void handle_tx(struct vhost_net *net) break; } } +} + +/* 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) +{ + struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX]; + struct vhost_virtqueue *vq = &nvq->vq; + struct socket *sock; + + mutex_lock(&vq->mutex); + sock = vq->private_data; + if (!sock) + goto out; + + if (!vq_iotlb_prefetch(vq)) + goto out; + + vhost_disable_notify(&net->dev, vq); + vhost_net_disable_vq(net, vq); + + if (vhost_sock_zcopy(sock)) + handle_tx_zerocopy(net, sock); + else + handle_tx_copy(net, sock); + out: mutex_unlock(&vq->mutex); } -- 2.7.4