Re: [PATCH] virtio_ring: Optimize duplicate judgment codes for virtqueue_add_split

Michael S. Tsirkin
2022-06-20T08:25:43Z

On Mon, Jun 20, 2022 at 04:06:56AM -0400, Deming Wang wrote:
> We combine repeated judgments about indirect in one place
>
> Signed-off-by: Deming Wang <wangdeming@inspur.com>

Point being? The patch makes the code kind of confusing.
What do we gain in return?

> ---
> drivers/virtio/virtio_ring.c | 16 ++++++----------
> 1 file changed, 6 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 13a7348cedff..331fa3cf5be7 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -582,23 +582,19 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
> total_sg * sizeof(struct vring_desc),
> VRING_DESC_F_INDIRECT,
> false);
> + vq->free_head = vq->split.desc_extra[head].next;
> + vq->split.desc_state[head].indir_desc = desc;
> + } else {
> + /* Update free pointer */
> + vq->free_head = i;
> + vq->split.desc_state[head].indir_desc = ctx;
> }
>
> /* We're using some buffers from the free list. */
> vq->vq.num_free -= descs_used;
>
> - /* Update free pointer */
> - if (indirect)
> - vq->free_head = vq->split.desc_extra[head].next;
> - else
> - vq->free_head = i;
> -
> /* Store token and indirect buffer state. */
> vq->split.desc_state[head].data = data;
> - if (indirect)
> - vq->split.desc_state[head].indir_desc = desc;
> - else
> - vq->split.desc_state[head].indir_desc = ctx;
>
> /* Put entry in available array (but don't update avail->idx until they
> * do sync). */
> --
> 2.27.0