linux-kernel - Re: [PATCH vhost v2 09/10] vdpa/mlx5: Small improvement for change_num

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Message-ID: <CAJaqyWcnJwfwyGKqx62OdSXrVH4gA701E-j5soChG0ZfTUsi9Q@mail.gmail.com>
Date: Wed, 28 Aug 2024 14:48:59 +0200
From: Eugenio Perez Martin <eperezma@...hat.com>
To: Dragos Tatulea <dtatulea@...dia.com>
Cc: "Michael S . Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, 
	virtualization@...ts.linux-foundation.org, Si-Wei Liu <si-wei.liu@...cle.com>, 
	Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Gal Pressman <gal@...dia.com>, 
	Parav Pandit <parav@...dia.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, 
	Tariq Toukan <tariqt@...dia.com>
Subject: Re: [PATCH vhost v2 09/10] vdpa/mlx5: Small improvement for change_num_qps()

On Fri, Aug 16, 2024 at 11:03 AM Dragos Tatulea <dtatulea@...dia.com> wrote:
>
> change_num_qps() has a lot of multiplications by 2 to convert
> the number of VQ pairs to number of VQs. This patch simplifies
> the code by doing the VQP -> VQ count conversion at the beginning
> in a variable.
>
> Signed-off-by: Dragos Tatulea <dtatulea@...dia.com>
> Reviewed-by: Tariq Toukan <tariqt@...dia.com>

Acked-by: Eugenio Pérez <eperezma@...hat.com>

> ---
>  drivers/vdpa/mlx5/net/mlx5_vnet.c | 21 +++++++++++----------
>  1 file changed, 11 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 65063c507130..d1a01c229110 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -2219,16 +2219,17 @@ static virtio_net_ctrl_ack handle_ctrl_mac(struct mlx5_vdpa_dev *mvdev, u8 cmd)
>  static int change_num_qps(struct mlx5_vdpa_dev *mvdev, int newqps)
>  {
>         struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
> -       int cur_qps = ndev->cur_num_vqs / 2;
> +       int cur_vqs = ndev->cur_num_vqs;
> +       int new_vqs = newqps * 2;
>         int err;
>         int i;
>
> -       if (cur_qps > newqps) {
> -               err = modify_rqt(ndev, 2 * newqps);
> +       if (cur_vqs > new_vqs) {
> +               err = modify_rqt(ndev, new_vqs);
>                 if (err)
>                         return err;
>
> -               for (i = ndev->cur_num_vqs - 1; i >= 2 * newqps; i--) {
> +               for (i = cur_vqs - 1; i >= new_vqs; i--) {
>                         struct mlx5_vdpa_virtqueue *mvq = &ndev->vqs[i];
>
>                         if (is_resumable(ndev))
> @@ -2237,27 +2238,27 @@ static int change_num_qps(struct mlx5_vdpa_dev *mvdev, int newqps)
>                                 teardown_vq(ndev, mvq);
>                 }
>
> -               ndev->cur_num_vqs = 2 * newqps;
> +               ndev->cur_num_vqs = new_vqs;
>         } else {
> -               ndev->cur_num_vqs = 2 * newqps;
> -               for (i = cur_qps * 2; i < 2 * newqps; i++) {
> +               ndev->cur_num_vqs = new_vqs;
> +               for (i = cur_vqs; i < new_vqs; i++) {
>                         struct mlx5_vdpa_virtqueue *mvq = &ndev->vqs[i];
>
>                         err = mvq->initialized ? resume_vq(ndev, mvq) : setup_vq(ndev, mvq, true);
>                         if (err)
>                                 goto clean_added;
>                 }
> -               err = modify_rqt(ndev, 2 * newqps);
> +               err = modify_rqt(ndev, new_vqs);
>                 if (err)
>                         goto clean_added;
>         }
>         return 0;
>
>  clean_added:
> -       for (--i; i >= 2 * cur_qps; --i)
> +       for (--i; i >= cur_vqs; --i)
>                 teardown_vq(ndev, &ndev->vqs[i]);
>
> -       ndev->cur_num_vqs = 2 * cur_qps;
> +       ndev->cur_num_vqs = cur_vqs;
>
>         return err;
>  }
> --
> 2.45.1
>