netdev - Re: [net-next PATCH v5 0/6] XDP for virtio

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Date:   Thu, 8 Dec 2016 23:16:47 +0200
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     David Miller <davem@...emloft.net>
Cc:     john.fastabend@...il.com, daniel@...earbox.net,
        shm@...ulusnetworks.com, tgraf@...g.ch,
        alexei.starovoitov@...il.com, john.r.fastabend@...el.com,
        netdev@...r.kernel.org, brouer@...hat.com
Subject: Re: [net-next PATCH v5 0/6] XDP for virtio_net

On Thu, Dec 08, 2016 at 02:17:02PM -0500, David Miller wrote:
> From: John Fastabend <john.fastabend@...il.com>
> Date: Wed, 07 Dec 2016 12:10:47 -0800
> 
> > This implements virtio_net for the mergeable buffers and big_packet
> > modes. I tested this with vhost_net running on qemu and did not see
> > any issues. For testing num_buf > 1 I added a hack to vhost driver
> > to only but 100 bytes per buffer.
>  ...
> 
> So where are we with this?
> 
> I'm not too thrilled with the idea of making XDP_TX optional or
> something like that.  If someone enables XDP, there is a tradeoff.

The issue is inability of XDP TX to share xmit queues with net stack.
I'm guessing virtio is not the only card that has a limited
number of queues, is it? Is it really so hard to lock the queue
and check it's running? Could be optional in case resources are there
...

-- 
MST