netdev - Re: [PATCH v5 20/22] virtio_net: set the default max ring num

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Date:   Wed, 16 Feb 2022 12:14:31 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc:     virtualization <virtualization@...ts.linux-foundation.org>,
        netdev <netdev@...r.kernel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>, bpf@...r.kernel.org
Subject: Re: [PATCH v5 20/22] virtio_net: set the default max ring num

On Mon, Feb 14, 2022 at 4:14 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> Sets the default maximum ring num based on virtio_set_max_ring_num().
>
> The default maximum ring num is 1024.

Having a default value is pretty useful, I see 32K is used by default for IFCVF.

Rethink this, how about having a different default value based on the speed?

Without SPEED_DUPLEX, we use 1024. Otherwise

10g 4096
40g 8192

etc.

(The number are just copied from the 10g/40g default parameter from
other vendors)

Thanks

>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
>  drivers/net/virtio_net.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index a4ffd7cdf623..77e61fe0b2ce 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -35,6 +35,8 @@ module_param(napi_tx, bool, 0644);
>  #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
>  #define GOOD_COPY_LEN  128
>
> +#define VIRTNET_DEFAULT_MAX_RING_NUM 1024
> +
>  #define VIRTNET_RX_PAD (NET_IP_ALIGN + NET_SKB_PAD)
>
>  /* Amount of XDP headroom to prepend to packets for use by xdp_adjust_head */
> @@ -3045,6 +3047,8 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
>                         ctx[rxq2vq(i)] = true;
>         }
>
> +       virtio_set_max_ring_num(vi->vdev, VIRTNET_DEFAULT_MAX_RING_NUM);
> +
>         ret = virtio_find_vqs_ctx(vi->vdev, total_vqs, vqs, callbacks,
>                                   names, ctx, NULL);
>         if (ret)
> --
> 2.31.0
>