On Wed, Oct 15, 2014 at 03:25:26PM +0800, Jason Wang wrote:
> This patch introduces virtio_enable_cb_avail() to publish avail idx
> and used event. This could be used by batched buffer submitting to
> reduce the number of tx interrupts.
>
> Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> drivers/virtio/virtio_ring.c | 22 ++++++++++++++++++++--
> include/linux/virtio.h | 2 ++
> 2 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 1b3929f..d67fbf8 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -567,14 +567,32 @@ unsigned virtqueue_enable_cb_prepare(struct virtqueue *_vq)
> * entry. Always do both to keep code simple. */
> vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
> /* Make sure used event never go backwards */
> - if (!vring_need_event(vring_used_event(&vq->vring),
> - vq->vring.avail->idx, last_used_idx))
> + if (vq->vring.avail->idx != vring_used_event(&vq->vring) &&
> + !vring_need_event(vring_used_event(&vq->vring),
> + vq->vring.avail->idx, last_used_idx)) {
> vring_used_event(&vq->vring) = last_used_idx;
> + }
> END_USE(vq);
> return last_used_idx;
> }
> EXPORT_SYMBOL_GPL(virtqueue_enable_cb_prepare);
>
I see you are also changing virtqueue_enable_cb_prepare, why?
> +bool virtqueue_enable_cb_avail(struct virtqueue *_vq)
> +{
> + struct vring_virtqueue *vq = to_vvq(_vq);
> + bool ret;
> +
> + START_USE(vq);
> + vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
> + vring_used_event(&vq->vring) = vq->vring.avail->idx;
> + ret = vring_need_event(vq->vring.avail->idx,
> + vq->last_used_idx, vq->vring.used->idx);
> + END_USE(vq);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(virtqueue_enable_cb_avail);
> +
> /**
> * virtqueue_poll - query pending used buffers
> * @vq: the struct virtqueue we're talking about.
Could not figure out what this does.
Please add documentation.
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index b46671e..bfaf058 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -65,6 +65,8 @@ bool virtqueue_enable_cb(struct virtqueue *vq);
>
> unsigned virtqueue_enable_cb_prepare(struct virtqueue *vq);
>
> +bool virtqueue_enable_cb_avail(struct virtqueue *vq);
> +
> bool virtqueue_poll(struct virtqueue *vq, unsigned);
>
> bool virtqueue_enable_cb_delayed(struct virtqueue *vq);
> --
> 1.7.1
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