linux-kernel - Re: [PATCH] virtio: replace constant parameter '1' with num

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Date:   Tue, 8 Dec 2020 08:55:06 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     liush <liush@...winnertech.com>
Cc:     jasowang@...hat.com, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] virtio: replace constant parameter '1' with num

On Tue, Dec 08, 2020 at 07:57:51PM +0800, liush wrote:
> 'num' can represent the value of out_sgs(in_sags), no need to pass 
> in constant parameters in 'virtqueue_add'.
> 
> Signed-off-by: liush <liush@...winnertech.com>

Point being?
A constant is likely easier for the compiler to optimize ...

> ---
>  drivers/virtio/virtio_ring.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index becc776..7583f8b 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1760,7 +1760,7 @@ int virtqueue_add_outbuf(struct virtqueue *vq,
>  			 void *data,
>  			 gfp_t gfp)
>  {
> -	return virtqueue_add(vq, &sg, num, 1, 0, data, NULL, gfp);
> +	return virtqueue_add(vq, &sg, num, num, 0, data, NULL, gfp);
>  }
>  EXPORT_SYMBOL_GPL(virtqueue_add_outbuf);
>  
> @@ -1782,7 +1782,7 @@ int virtqueue_add_inbuf(struct virtqueue *vq,
>  			void *data,
>  			gfp_t gfp)
>  {
> -	return virtqueue_add(vq, &sg, num, 0, 1, data, NULL, gfp);
> +	return virtqueue_add(vq, &sg, num, 0, num, data, NULL, gfp);
>  }
>  EXPORT_SYMBOL_GPL(virtqueue_add_inbuf);
>  
> -- 
> 2.7.4