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SubjectRe: [PATCH net-next 2/3] vhost_net: support in order feature
On Fri, Nov 23, 2018 at 11:00:15AM +0800, Jason Wang wrote:
> This makes vhost_net to support in order feature. This is as simple as
> use datacopy path when it was negotiated. An alternative is not to
> advertise in order when zerocopy is enabled which tends to be
> suboptimal consider zerocopy may suffer from e.g HOL issues.

Well IIRC vhost_zerocopy_signal_used is used to
actually reorder used ring to match available ring.
So with a big comment explaining why it is so,
we could just enable IN_ORDER there too.

>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
> drivers/vhost/net.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index d919284f103b..bdf5de5a7eb2 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -74,7 +74,8 @@ enum {
> VHOST_NET_FEATURES = VHOST_FEATURES |
> (1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
> (1ULL << VIRTIO_NET_F_MRG_RXBUF) |
> - (1ULL << VIRTIO_F_IOMMU_PLATFORM)
> + (1ULL << VIRTIO_F_IOMMU_PLATFORM) |
> + (1ULL << VIRTIO_F_IN_ORDER)
> };
>
> enum {
> @@ -971,7 +972,8 @@ static void handle_tx(struct vhost_net *net)
> vhost_disable_notify(&net->dev, vq);
> vhost_net_disable_vq(net, vq);
>
> - if (vhost_sock_zcopy(sock))
> + if (vhost_sock_zcopy(sock) &&
> + !vhost_has_feature(vq, VIRTIO_F_IN_ORDER))
> handle_tx_zerocopy(net, sock);
> else
> handle_tx_copy(net, sock);
> --
> 2.17.1

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