linux-kernel - Re: [PATCH net 9/9] virtio-net: XDP support for small buffers

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Date:   Tue, 3 Jan 2017 14:16:31 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     John Fastabend <john.fastabend@...il.com>, mst@...hat.com,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     john.r.fastabend@...el.com
Subject: Re: [PATCH net 9/9] virtio-net: XDP support for small buffers



On 2017年01月03日 06:43, John Fastabend wrote:
> On 16-12-23 06:37 AM, Jason Wang wrote:
>> Commit f600b6905015 ("virtio_net: Add XDP support") leaves the case of
>> small receive buffer untouched. This will confuse the user who want to
>> set XDP but use small buffers. Other than forbid XDP in small buffer
>> mode, let's make it work. XDP then can only work at skb->data since
>> virtio-net create skbs during refill, this is sub optimal which could
>> be optimized in the future.
>>
>> Cc: John Fastabend <john.r.fastabend@...el.com>
>> Signed-off-by: Jason Wang <jasowang@...hat.com>
>> ---
>>   drivers/net/virtio_net.c | 112 ++++++++++++++++++++++++++++++++++++-----------
>>   1 file changed, 87 insertions(+), 25 deletions(-)
>>
> Hi Jason,
>
> I was doing some more testing on this what do you think about doing this
> so that free_unused_bufs() handles the buffer free with dev_kfree_skb()
> instead of put_page in small receive mode. Seems more correct to me.
>
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 783e842..27ff76c 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1898,6 +1898,10 @@ static void free_receive_page_frags(struct virtnet_info *vi)
>
>   static bool is_xdp_queue(struct virtnet_info *vi, int q)
>   {
> +       /* For small receive mode always use kfree_skb variants */
> +       if (!vi->mergeable_rx_bufs)
> +               return false;
> +
>          if (q < (vi->curr_queue_pairs - vi->xdp_queue_pairs))
>                  return false;
>          else if (q < vi->curr_queue_pairs)
>
>
> patch is untested just spotted doing code review.
>
> Thanks,
> John

We probably need a better name for this function.

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