Leandro Dorileo <l@xxxxxxxxxxx> writes:
> Cchange init_vqs() to avoid calling twice the virtio_has_feature()
> - attempting to find out if VIRTIO_BALLOON_F_STATS_VQ feature was negotiated -
> consequently we prevent unnecessarily running the drivers' feature_table more
> than needed.
>
> Signed-off-by: Leandro Dorileo <l@xxxxxxxxxxx>
Hi Leandro,
This seems like a premature optimization. The current code is
fairly clear, and there's no performance issue with init_vqs.
Am I missing something?
Rusty.
> ---
> drivers/virtio/virtio_balloon.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 34bdaba..41771c1 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -320,19 +320,21 @@ static int init_vqs(struct virtio_balloon *vb)
> vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
> const char *names[] = { "inflate", "deflate", "stats" };
> int err, nvqs;
> + bool stats;
>
> /*
> * We expect two virtqueues: inflate and deflate, and
> * optionally stat.
> */
> - nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
> + stats = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ);
> + nvqs = stats ? 3 : 2;
> err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
> if (err)
> return err;
>
> vb->inflate_vq = vqs[0];
> vb->deflate_vq = vqs[1];
> - if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
> + if (stats) {
> struct scatterlist sg;
> vb->stats_vq = vqs[2];
>
> --
> 1.8.5.3
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