hulk inclusion category: feature bugzilla: NA CVE: N/A

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During high-frequency packet transmission, if vhost immediately notifies virtio driver after reading the virtio_queue empty, virtio driver will perform a kick after sending the next packet. However, if vhost waits a little longer, it could get the next packet sent by virtio driver without the need for virtio to perform a kick.

This patch optimizes for this issue. If the TX interval recently recorded by vhost-net is within 50us, it is considered a high-frequency packet sending. At this time, after detecting the virtio_queue is empty, vhost-net will wait for new packets to arrive before notifing the virtio driver.

Signed-off-by: Xu Kuohai xukuohai@huawei.com --- drivers/vhost/net.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index a6a1a01319d8..7312d0bfa3c1 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -126,6 +126,8 @@ struct vhost_net_virtqueue { struct vhost_net_buf rxq; /* Batched XDP buffs */ struct xdp_buff *xdp; + u64 tx_time; + u64 tx_interval; };

struct vhost_net { @@ -311,6 +313,8 @@ static void vhost_net_vq_reset(struct vhost_net *n) n->vqs[i].ubufs = NULL; n->vqs[i].vhost_hlen = 0; n->vqs[i].sock_hlen = 0; + n->vqs[i].tx_time = 0; + n->vqs[i].tx_interval = 1000000; /* 1ms */ vhost_net_buf_init(&n->vqs[i].rxq); }

@@ -456,6 +460,19 @@ static void vhost_net_signal_used(struct vhost_net_virtqueue *nvq) nvq->done_idx = 0; }

+static void vhost_update_tx_interval(struct vhost_net_virtqueue *nvq) +{ + u64 time = ktime_get_mono_fast_ns(); + + if (likely(nvq->tx_time != 0)) { + u64 d = time - nvq->tx_time; + /* 0.25 * interval + 0.75 * delta */ + nvq->tx_interval = (nvq->tx_interval >> 2) + (d - (d >> 2)); + } + + nvq->tx_time = time; +} + static void vhost_tx_batch(struct vhost_net *net, struct vhost_net_virtqueue *nvq, struct socket *sock, @@ -489,6 +506,7 @@ static void vhost_tx_batch(struct vhost_net *net, }

signal_used: + vhost_update_tx_interval(nvq); vhost_net_signal_used(nvq); nvq->batched_xdp = 0; } @@ -782,6 +800,7 @@ static void handle_tx_copy(struct vhost_net *net, struct socket *sock) int err; int sent_pkts = 0; bool sock_can_batch = (sock->sk->sk_sndbuf == INT_MAX); + int last_done_idx = 0;

do { bool busyloop_intr = false; @@ -798,6 +817,13 @@ static void handle_tx_copy(struct vhost_net *net, struct socket *sock) if (head == vq->num) { if (unlikely(busyloop_intr)) { vhost_poll_queue(&vq->poll); + } else if (nvq->tx_interval < 50000 && + ktime_get_mono_fast_ns() - nvq->tx_time < 50000) { + /* Update TX interval if we get some packets */ + if (last_done_idx < nvq->done_idx) + vhost_update_tx_interval(nvq); + last_done_idx = nvq->done_idx; + continue; } else if (unlikely(vhost_enable_notify(&net->dev, vq))) { vhost_disable_notify(&net->dev, vq);