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Date: Thu, 11 Apr 2013 10:24:30 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jason Wang <jasowang@...hat.com>
Cc: kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
davem@...emloft.net
Subject: Re: [PATCH] vhost_net: remove tx polling state
On Thu, Apr 11, 2013 at 02:50:48PM +0800, Jason Wang wrote:
> After commit 2b8b328b61c799957a456a5a8dab8cc7dea68575 (vhost_net: handle polling
> errors when setting backend), we in fact track the polling state through
> poll->wqh, so there's no need to duplicate the work with an extra
> vhost_net_polling_state. So this patch removes this and make the code simpler.
>
> This patch also removes the all tx starting/stopping code in tx path according
> to Michael's suggestion.
>
> Netperf test shows almost the same result in stream test, but gets improvements
> on TCP_RR tests (both zerocopy or copy) especially on low load cases.
>
> Tested between multiqueue kvm guest and external host with two direct
> connected 82599s.
>
> zerocopy disabled:
>
> sessions|transaction rates|normalize|
> before/after/+improvements
> 1 | 9510.24/11727.29/+23.3% | 693.54/887.68/+28.0% |
> 25| 192931.50/241729.87/+25.3% | 2376.80/2771.70/+16.6% |
> 50| 277634.64/291905.76/+5% | 3118.36/3230.11/+3.6% |
>
> zerocopy enabled:
>
> sessions|transaction rates|normalize|
> before/after/+improvements
> 1 | 7318.33/11929.76/+63.0% | 521.86/843.30/+61.6% |
> 25| 167264.88/242422.15/+44.9% | 2181.60/2788.16/+27.8% |
> 50| 272181.02/294347.04/+8.1% | 3071.56/3257.85/+6.1% |
>
> Signed-off-by: Jason Wang <jasowang@...hat.com>
Less code and better speed, what's not to like.
Davem, could you pick this up for 3.10 please?
Acked-by: Michael S. Tsirkin <mst@...hat.com>
> ---
> drivers/vhost/net.c | 74 ++++---------------------------------------------
> drivers/vhost/vhost.c | 3 ++
> 2 files changed, 9 insertions(+), 68 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index ec6fb3f..87c216c 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -64,20 +64,10 @@ enum {
> VHOST_NET_VQ_MAX = 2,
> };
>
> -enum vhost_net_poll_state {
> - VHOST_NET_POLL_DISABLED = 0,
> - VHOST_NET_POLL_STARTED = 1,
> - VHOST_NET_POLL_STOPPED = 2,
> -};
> -
> struct vhost_net {
> struct vhost_dev dev;
> struct vhost_virtqueue vqs[VHOST_NET_VQ_MAX];
> struct vhost_poll poll[VHOST_NET_VQ_MAX];
> - /* Tells us whether we are polling a socket for TX.
> - * We only do this when socket buffer fills up.
> - * Protected by tx vq lock. */
> - enum vhost_net_poll_state tx_poll_state;
> /* Number of TX recently submitted.
> * Protected by tx vq lock. */
> unsigned tx_packets;
> @@ -155,28 +145,6 @@ static void copy_iovec_hdr(const struct iovec *from, struct iovec *to,
> }
> }
>
> -/* Caller must have TX VQ lock */
> -static void tx_poll_stop(struct vhost_net *net)
> -{
> - if (likely(net->tx_poll_state != VHOST_NET_POLL_STARTED))
> - return;
> - vhost_poll_stop(net->poll + VHOST_NET_VQ_TX);
> - net->tx_poll_state = VHOST_NET_POLL_STOPPED;
> -}
> -
> -/* Caller must have TX VQ lock */
> -static int tx_poll_start(struct vhost_net *net, struct socket *sock)
> -{
> - int ret;
> -
> - if (unlikely(net->tx_poll_state != VHOST_NET_POLL_STOPPED))
> - return 0;
> - ret = vhost_poll_start(net->poll + VHOST_NET_VQ_TX, sock->file);
> - if (!ret)
> - net->tx_poll_state = VHOST_NET_POLL_STARTED;
> - return ret;
> -}
> -
> /* In case of DMA done not in order in lower device driver for some reason.
> * upend_idx is used to track end of used idx, done_idx is used to track head
> * of used idx. Once lower device DMA done contiguously, we will signal KVM
> @@ -242,7 +210,7 @@ static void handle_tx(struct vhost_net *net)
> .msg_flags = MSG_DONTWAIT,
> };
> size_t len, total_len = 0;
> - int err, wmem;
> + int err;
> size_t hdr_size;
> struct socket *sock;
> struct vhost_ubuf_ref *uninitialized_var(ubufs);
> @@ -253,19 +221,9 @@ static void handle_tx(struct vhost_net *net)
> if (!sock)
> return;
>
> - wmem = atomic_read(&sock->sk->sk_wmem_alloc);
> - if (wmem >= sock->sk->sk_sndbuf) {
> - mutex_lock(&vq->mutex);
> - tx_poll_start(net, sock);
> - mutex_unlock(&vq->mutex);
> - return;
> - }
> -
> mutex_lock(&vq->mutex);
> vhost_disable_notify(&net->dev, vq);
>
> - if (wmem < sock->sk->sk_sndbuf / 2)
> - tx_poll_stop(net);
> hdr_size = vq->vhost_hlen;
> zcopy = vq->ubufs;
>
> @@ -285,23 +243,14 @@ static void handle_tx(struct vhost_net *net)
> if (head == vq->num) {
> int num_pends;
>
> - wmem = atomic_read(&sock->sk->sk_wmem_alloc);
> - if (wmem >= sock->sk->sk_sndbuf * 3 / 4) {
> - tx_poll_start(net, sock);
> - set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
> - break;
> - }
> /* If more outstanding DMAs, queue the work.
> * Handle upend_idx wrap around
> */
> num_pends = likely(vq->upend_idx >= vq->done_idx) ?
> (vq->upend_idx - vq->done_idx) :
> (vq->upend_idx + UIO_MAXIOV - vq->done_idx);
> - if (unlikely(num_pends > VHOST_MAX_PEND)) {
> - tx_poll_start(net, sock);
> - set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
> + if (unlikely(num_pends > VHOST_MAX_PEND))
> break;
> - }
> if (unlikely(vhost_enable_notify(&net->dev, vq))) {
> vhost_disable_notify(&net->dev, vq);
> continue;
> @@ -364,8 +313,6 @@ static void handle_tx(struct vhost_net *net)
> UIO_MAXIOV;
> }
> vhost_discard_vq_desc(vq, 1);
> - if (err == -EAGAIN || err == -ENOBUFS)
> - tx_poll_start(net, sock);
> break;
> }
> if (err != len)
> @@ -628,7 +575,6 @@ static int vhost_net_open(struct inode *inode, struct file *f)
>
> vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, POLLOUT, dev);
> vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, POLLIN, dev);
> - n->tx_poll_state = VHOST_NET_POLL_DISABLED;
>
> f->private_data = n;
>
> @@ -638,32 +584,24 @@ static int vhost_net_open(struct inode *inode, struct file *f)
> static void vhost_net_disable_vq(struct vhost_net *n,
> struct vhost_virtqueue *vq)
> {
> + struct vhost_poll *poll = n->poll + (vq - n->vqs);
> if (!vq->private_data)
> return;
> - if (vq == n->vqs + VHOST_NET_VQ_TX) {
> - tx_poll_stop(n);
> - n->tx_poll_state = VHOST_NET_POLL_DISABLED;
> - } else
> - vhost_poll_stop(n->poll + VHOST_NET_VQ_RX);
> + vhost_poll_stop(poll);
> }
>
> static int vhost_net_enable_vq(struct vhost_net *n,
> struct vhost_virtqueue *vq)
> {
> + struct vhost_poll *poll = n->poll + (vq - n->vqs);
> struct socket *sock;
> - int ret;
>
> sock = rcu_dereference_protected(vq->private_data,
> lockdep_is_held(&vq->mutex));
> if (!sock)
> return 0;
> - if (vq == n->vqs + VHOST_NET_VQ_TX) {
> - n->tx_poll_state = VHOST_NET_POLL_STOPPED;
> - ret = tx_poll_start(n, sock);
> - } else
> - ret = vhost_poll_start(n->poll + VHOST_NET_VQ_RX, sock->file);
>
> - return ret;
> + return vhost_poll_start(poll, sock->file);
> }
>
> static struct socket *vhost_net_stop_vq(struct vhost_net *n,
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 9759249..4eecdb8 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -89,6 +89,9 @@ int vhost_poll_start(struct vhost_poll *poll, struct file *file)
> unsigned long mask;
> int ret = 0;
>
> + if (poll->wqh)
> + return 0;
> +
> mask = file->f_op->poll(file, &poll->table);
> if (mask)
> vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
> --
> 1.7.1
--
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