linux-kernel - Re: [PATCH] virtio_ring: remove unnecessary to_vvq call in virtqueue_disable_cb

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Date:   Wed, 22 Jun 2022 08:15:12 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Deming Wang <wangdeming@...pur.com>
Cc:     jasowang@...hat.com, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] virtio_ring: remove unnecessary to_vvq call in
 virtqueue_disable_cb_packed

On Wed, Jun 22, 2022 at 03:50:52AM -0400, Deming Wang wrote:
> It passes '_vq' to virtqueue_use_indirect(), which still calls
> to_vvq to get 'vq', let's directly pass 'vq'. It can avoid
> unnecessary call of to_vvq in hot path.
> 
> Signed-off-by: Deming Wang <wangdeming@...pur.com>

I do not see the point of any of these patches. Sorry.
If this is supposed to be an optimization, post some numbers pls.


> ---
>  drivers/virtio/virtio_ring.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 13a7348cedff..af2b7785ed77 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1475,10 +1475,8 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq,
>  	return ret;
>  }
>  
> -static void virtqueue_disable_cb_packed(struct virtqueue *_vq)
> +static void virtqueue_disable_cb_packed(struct vring_virtqueue *vq)
>  {
> -	struct vring_virtqueue *vq = to_vvq(_vq);
> -
>  	if (vq->packed.event_flags_shadow != VRING_PACKED_EVENT_FLAG_DISABLE) {
>  		vq->packed.event_flags_shadow = VRING_PACKED_EVENT_FLAG_DISABLE;
>  		vq->packed.vring.driver->flags =
> @@ -2007,7 +2005,7 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
>  		return;
>  
>  	if (vq->packed_ring)
> -		virtqueue_disable_cb_packed(_vq);
> +		virtqueue_disable_cb_packed(vq);
>  	else
>  		virtqueue_disable_cb_split(_vq);
>  }
> -- 
> 2.27.0