netdev - Re: [PATCH net-next v3 12/15] virtio

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Date:   Wed, 26 Apr 2023 14:00:31 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     Jason Wang <jasowang@...hat.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 v3 12/15] virtio_net: small: optimize code

On Wed, 26 Apr 2023 11:08:52 +0800, Jason Wang <jasowang@...hat.com> wrote:
> On Sun, Apr 23, 2023 at 6:58 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> >
> > Avoid the problem that some variables(headroom and so on) will repeat
> > the calculation when process xdp.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
>
> Nit: I think we need to tweak the title, it's better to say what is
> optimized. (And it would be better to tweak the title of patch 11 as
> well)

Yes, I agree this.

Thanks.

>
> Acked-by: Jason Wang <jasowang@...hat.com>
>
> > ---
> >  drivers/net/virtio_net.c | 12 ++++++++----
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 5bc3dca0f60c..601c0e7fc32b 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -1031,11 +1031,10 @@ static struct sk_buff *receive_small(struct net_device *dev,
> >         struct sk_buff *skb;
> >         struct bpf_prog *xdp_prog;
> >         unsigned int xdp_headroom = (unsigned long)ctx;
> > -       unsigned int header_offset = VIRTNET_RX_PAD + xdp_headroom;
> > -       unsigned int headroom = vi->hdr_len + header_offset;
> > -       unsigned int buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
> > -                             SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> >         struct page *page = virt_to_head_page(buf);
> > +       unsigned int header_offset;
> > +       unsigned int headroom;
> > +       unsigned int buflen;
> >
> >         len -= vi->hdr_len;
> >         stats->bytes += len;
> > @@ -1063,6 +1062,11 @@ static struct sk_buff *receive_small(struct net_device *dev,
> >         rcu_read_unlock();
> >
> >  skip_xdp:
> > +       header_offset = VIRTNET_RX_PAD + xdp_headroom;
> > +       headroom = vi->hdr_len + header_offset;
> > +       buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
> > +               SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> > +
> >         skb = build_skb(buf, buflen);
> >         if (!skb)
> >                 goto err;
> > --
> > 2.32.0.3.g01195cf9f
> >
>