On Wed, Nov 09, 2016 at 03:38:33PM +0800, Jason Wang wrote:
> This patch tries to utilize tuntap rx batching by peeking the tx
> virtqueue during transmission, if there's more available buffers in
> the virtqueue, set MSG_MORE flag for a hint for tuntap to batch the
> packets. The maximum number of batched tx packets were specified
> through a module parameter: tx_bached.
>
> When use 16 as tx_batched:
When using
>
> Pktgen test shows 16% on tx pps in guest.
> Netperf test does not show obvious regression.
Why doesn't netperf benefit?
> For safety, 1 were used as the default value for tx_batched.
s/were used/is used/
> Signed-off-by: Jason Wang <jasow...@redhat.com>
These tests unfortunately only run a single flow.
The concern would be whether this increases latency when
NIC is busy with other flows, so I think this is what
you need to test.
> ---
> drivers/vhost/net.c | 15 ++++++++++++++-
> drivers/vhost/vhost.c | 1 +
> drivers/vhost/vhost.h | 1 +
> 3 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 5dc128a..51c378e 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -35,6 +35,10 @@ module_param(experimental_zcopytx, int, 0444);
> MODULE_PARM_DESC(experimental_zcopytx, "Enable Zero Copy TX;"
> " 1 -Enable; 0 - Disable");
>
> +static int tx_batched = 1;
> +module_param(tx_batched, int, 0444);
> +MODULE_PARM_DESC(tx_batched, "Number of patches batched in TX");
> +
> /* Max number of bytes transferred before requeueing the job.
> * Using this limit prevents one virtqueue from starving others. */
> #define VHOST_NET_WEIGHT 0x80000
I think we should do some tests and find a good default.
> @@ -454,6 +458,16 @@ static void handle_tx(struct vhost_net *net)
> msg.msg_control = NULL;
> ubufs = NULL;
> }
> + total_len += len;
> + if (vq->delayed < tx_batched &&
> + total_len < VHOST_NET_WEIGHT &&
> + !vhost_vq_avail_empty(&net->dev, vq)) {
> + vq->delayed++;
> + msg.msg_flags |= MSG_MORE;
> + } else {
> + vq->delayed = 0;
> + 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)) {
> @@ -472,7 +486,6 @@ static void handle_tx(struct vhost_net *net)
> vhost_add_used_and_signal(&net->dev, vq, head, 0);
> else
> vhost_zerocopy_signal_used(net, vq);
> - total_len += len;
> vhost_net_tx_packet(net);
> if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
> vhost_poll_queue(&vq->poll);
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index fdf4cdf..bc362c7 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -311,6 +311,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
> vq->busyloop_timeout = 0;
> vq->umem = NULL;
> vq->iotlb = NULL;
> + vq->delayed = 0;
> }
>
> static int vhost_worker(void *data)
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index 78f3c5f..9f81a94 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -141,6 +141,7 @@ struct vhost_virtqueue {
> bool user_be;
> #endif
> u32 busyloop_timeout;
> + int delayed;
> };
>
> struct vhost_msg_node {
> --
> 2.7.4
