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

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Message-ID: <1645090228.2917905-1-xuanzhuo@linux.alibaba.com>
Date:   Thu, 17 Feb 2022 17:30:28 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     Jason Wang <jasowang@...hat.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 Thu, 17 Feb 2022 15:21:26 +0800, Jason Wang <jasowang@...hat.com> wrote:
> On Wed, Feb 16, 2022 at 3:52 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> >
> > On Wed, 16 Feb 2022 12:14:31 +0800, Jason Wang <jasowang@...hat.com> wrote:
> > > 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
> >
> > We can define different default values of tx and rx by the way. This way I can
> > just use it in the new interface of find_vqs().
> >
> > without SPEED_DUPLEX:  tx 512 rx 1024
> >
>
> Any reason that TX is smaller than RX?
>

I've seen some NIC drivers with default tx smaller than rx.

One problem I have now is that inside virtnet_probe, init_vqs is before getting
speed/duplex. I'm not sure, can the logic to get speed/duplex be put before
init_vqs? Is there any risk?

Can you help me?

Thanks.

> Thanks
>
> > Thanks.
> >
> >
> > >
> > > 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
> > > >
> > >
> >
>