netdev - Re: [PATCH net-next v2 03/14] virtio_net: optimize mergeable_xdp

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Date:   Thu, 20 Apr 2023 13:59:19 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc:     netdev@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        virtualization@...ts.linux-foundation.org, bpf@...r.kernel.org
Subject: Re: [PATCH net-next v2 03/14] virtio_net: optimize mergeable_xdp_prepare()

On Tue, Apr 18, 2023 at 2:53 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> The previous patch, in order to facilitate review, I do not do any
> modification. This patch has made some optimization on the top.
>
> * remove some repeated logics in this function.
> * add fast check for passing without any alloc.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>

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

Thanks


> ---
>  drivers/net/virtio_net.c | 29 ++++++++++++++---------------
>  1 file changed, 14 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 12559062ffb6..50dc64d80d3b 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1192,6 +1192,11 @@ static void *mergeable_xdp_prepare(struct virtnet_info *vi,
>          */
>         *frame_sz = truesize;
>
> +       if (likely(headroom >= virtnet_get_headroom(vi) &&
> +                  (*num_buf == 1 || xdp_prog->aux->xdp_has_frags))) {
> +               return page_address(*page) + offset;
> +       }
> +
>         /* This happens when headroom is not enough because
>          * of the buffer was prefilled before XDP is set.
>          * This should only happen for the first several packets.
> @@ -1200,22 +1205,15 @@ static void *mergeable_xdp_prepare(struct virtnet_info *vi,
>          * support it, and we don't want to bother users who are
>          * using xdp normally.
>          */
> -       if (!xdp_prog->aux->xdp_has_frags &&
> -           (*num_buf > 1 || headroom < virtnet_get_headroom(vi))) {
> +       if (!xdp_prog->aux->xdp_has_frags) {
>                 /* linearize data for XDP */
>                 xdp_page = xdp_linearize_page(rq, num_buf,
>                                               *page, offset,
>                                               VIRTIO_XDP_HEADROOM,
>                                               len);
> -               *frame_sz = PAGE_SIZE;
> -
>                 if (!xdp_page)
>                         return NULL;
> -               offset = VIRTIO_XDP_HEADROOM;
> -
> -               put_page(*page);
> -               *page = xdp_page;
> -       } else if (unlikely(headroom < virtnet_get_headroom(vi))) {
> +       } else {
>                 xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
>                                           sizeof(struct skb_shared_info));
>                 if (*len + xdp_room > PAGE_SIZE)
> @@ -1227,14 +1225,15 @@ static void *mergeable_xdp_prepare(struct virtnet_info *vi,
>
>                 memcpy(page_address(xdp_page) + VIRTIO_XDP_HEADROOM,
>                        page_address(*page) + offset, *len);
> -               *frame_sz = PAGE_SIZE;
> -               offset = VIRTIO_XDP_HEADROOM;
> -
> -               put_page(*page);
> -               *page = xdp_page;
>         }
>
> -       return page_address(*page) + offset;
> +       *frame_sz = PAGE_SIZE;
> +
> +       put_page(*page);
> +
> +       *page = xdp_page;
> +
> +       return page_address(*page) + VIRTIO_XDP_HEADROOM;
>  }
>
>  static struct sk_buff *receive_mergeable(struct net_device *dev,
> --
> 2.32.0.3.g01195cf9f
>