netdev - Re: [PATCH 02/11] ixgbe: simplify Rx buffer recycle

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Message-ID: <CAJ+HfNhcj+LOQ5uLmyj0rZnomvW83NFDty0CQqj4a1wV7sQnmA@mail.gmail.com>
Date:   Mon, 24 Jun 2019 16:30:37 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     Kevin Laatz <kevin.laatz@...el.com>
Cc:     Netdev <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Björn Töpel <bjorn.topel@...el.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        bpf <bpf@...r.kernel.org>,
        intel-wired-lan <intel-wired-lan@...ts.osuosl.org>,
        Bruce Richardson <bruce.richardson@...el.com>,
        ciara.loftus@...el.com
Subject: Re: [PATCH 02/11] ixgbe: simplify Rx buffer recycle

On Thu, 20 Jun 2019 at 19:25, Kevin Laatz <kevin.laatz@...el.com> wrote:
>
> Currently, the dma, addr and handle are modified when we reuse Rx buffers
> in zero-copy mode. However, this is not required as the inputs to the
> function are copies, not the original values themselves. As we use the
> copies within the function, we can use the original 'obi' values
> directly without having to mask and add the headroom.
>
> Signed-off-by: Kevin Laatz <kevin.laatz@...el.com>

Acked-by: Björn Töpel <bjorn.topel@...el.com>


> ---
>  drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> index bfe95ce0bd7f..49536adafe8e 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> @@ -251,8 +251,6 @@ ixgbe_rx_buffer *ixgbe_get_rx_buffer_zc(struct ixgbe_ring *rx_ring,
>  static void ixgbe_reuse_rx_buffer_zc(struct ixgbe_ring *rx_ring,
>                                      struct ixgbe_rx_buffer *obi)
>  {
> -       unsigned long mask = (unsigned long)rx_ring->xsk_umem->chunk_mask;
> -       u64 hr = rx_ring->xsk_umem->headroom + XDP_PACKET_HEADROOM;
>         u16 nta = rx_ring->next_to_alloc;
>         struct ixgbe_rx_buffer *nbi;
>
> @@ -262,14 +260,9 @@ static void ixgbe_reuse_rx_buffer_zc(struct ixgbe_ring *rx_ring,
>         rx_ring->next_to_alloc = (nta < rx_ring->count) ? nta : 0;
>
>         /* transfer page from old buffer to new buffer */
> -       nbi->dma = obi->dma & mask;
> -       nbi->dma += hr;
> -
> -       nbi->addr = (void *)((unsigned long)obi->addr & mask);
> -       nbi->addr += hr;
> -
> -       nbi->handle = obi->handle & mask;
> -       nbi->handle += rx_ring->xsk_umem->headroom;
> +       nbi->dma = obi->dma;
> +       nbi->addr = obi->addr;
> +       nbi->handle = obi->handle;
>
>         obi->addr = NULL;
>         obi->skb = NULL;
> --
> 2.17.1
>