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References: <20220328105817.1028065-1-xianting.tian@linux.alibaba.com>
In-Reply-To: <20220328105817.1028065-1-xianting.tian@linux.alibaba.com>
From:   Jason Wang <jasowang@redhat.com>
Date:   Tue, 29 Mar 2022 12:56:46 +0800
Message-ID: <CACGkMEvgcJy3k-s39QeLkLFho_wpsBnEbrcHWugajy50qjAo-w@mail.gmail.com>
Subject: Re: [PATCH 1/2] virtio_ring: remove unnecessary to_vvq call in vring
 hot path
To:     Xianting Tian <xianting.tian@linux.alibaba.com>
Cc:     mst <mst@redhat.com>, Stefano Garzarella <sgarzare@redhat.com>,
        virtualization <virtualization@lists.linux-foundation.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
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On Mon, Mar 28, 2022 at 6:58 PM Xianting Tian
<xianting.tian@linux.alibaba.com> 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: Xianting Tian <xianting.tian@linux.alibaba.com>

Acked-by: Jason Wang <jasowang@redhat.com>

> ---
>  drivers/virtio/virtio_ring.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 962f1477b1fa..d597fc0874ec 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -205,11 +205,9 @@ struct vring_virtqueue {
>
>  #define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
>
> -static inline bool virtqueue_use_indirect(struct virtqueue *_vq,
> +static inline bool virtqueue_use_indirect(struct vring_virtqueue *vq,
>                                           unsigned int total_sg)
>  {
> -       struct vring_virtqueue *vq = to_vvq(_vq);
> -
>         /*
>          * If the host supports indirect descriptor tables, and we have multiple
>          * buffers, then go indirect. FIXME: tune this threshold
> @@ -507,7 +505,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
>
>         head = vq->free_head;
>
> -       if (virtqueue_use_indirect(_vq, total_sg))
> +       if (virtqueue_use_indirect(vq, total_sg))
>                 desc = alloc_indirect_split(_vq, total_sg, gfp);
>         else {
>                 desc = NULL;
> @@ -1194,7 +1192,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
>
>         BUG_ON(total_sg == 0);
>
> -       if (virtqueue_use_indirect(_vq, total_sg)) {
> +       if (virtqueue_use_indirect(vq, total_sg)) {
>                 err = virtqueue_add_indirect_packed(vq, sgs, total_sg, out_sgs,
>                                                     in_sgs, data, gfp);
>                 if (err != -ENOMEM) {
> --
> 2.17.1
>