Re: [RFC v9 02/11] vhost: use batched get_vq_desc version

Michael S. Tsirkin
2020-06-23T14:42:21Z

On Fri, Jun 19, 2020 at 08:22:53PM +0200, Eugenio Pérez wrote:
> From: "Michael S. Tsirkin" <mst@redhat.com>
>
> As testing shows no performance change, switch to that now.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> Link: https://lore.kernel.org/r/20200401183118.8334-3-eperezma@redhat.com
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
> drivers/vhost/test.c | 2 +-
> drivers/vhost/vhost.c | 314 ++++++++----------------------------------
> drivers/vhost/vhost.h | 7 +-
> 3 files changed, 61 insertions(+), 262 deletions(-)
>
> diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
> index a09dedc79f68..650e69261557 100644
> --- a/drivers/vhost/test.c
> +++ b/drivers/vhost/test.c
> @@ -119,7 +119,7 @@ static int vhost_test_open(struct inode *inode, struct file *f)
> dev = &n->dev;
> vqs[VHOST_TEST_VQ] = &n->vqs[VHOST_TEST_VQ];
> n->vqs[VHOST_TEST_VQ].handle_kick = handle_vq_kick;
> - vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV,
> + vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV + 64,
> VHOST_TEST_PKT_WEIGHT, VHOST_TEST_WEIGHT, true, NULL);
>
> f->private_data = n;
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 2d784681b0fa..13021d6986eb 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -304,6 +304,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
> {
> vq->num = 1;
> vq->ndescs = 0;
> + vq->first_desc = 0;
> vq->desc = NULL;
> vq->avail = NULL;
> vq->used = NULL;
> @@ -372,6 +373,11 @@ static int vhost_worker(void *data)
> return 0;
> }
>
> +static int vhost_vq_num_batch_descs(struct vhost_virtqueue *vq)
> +{
> + return vq->max_descs - UIO_MAXIOV;
> +}
> +
> static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
> {
> kfree(vq->descs);

Batching is enabled if max_descs > UIO_MAXIOV.

So this uses batching for test.

But net is unchanged, so it is still not using the batched version.
Is that right?

I think a better subject would be "vhost/test: use batched get_vq_desc version".

And that explains which testing it refers to: the one executed by vhost test.

I think there was a separate patch to enable that for net separately,
but it got lost - or did I miss it?

--
MST