netdev - Re: [PATCH RFC 2/4] vhost/vsock: split packets to send using multiple buffers

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Date:   Mon, 8 Apr 2019 10:28:11 +0100
From:   Stefan Hajnoczi <stefanha@...hat.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     Stefan Hajnoczi <stefanha@...il.com>, netdev@...r.kernel.org,
        Jason Wang <jasowang@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH RFC 2/4] vhost/vsock: split packets to send using
 multiple buffers

On Fri, Apr 05, 2019 at 11:36:08AM +0200, Stefano Garzarella wrote:
> On Fri, Apr 05, 2019 at 09:13:56AM +0100, Stefan Hajnoczi wrote:
> > On Thu, Apr 04, 2019 at 12:58:36PM +0200, Stefano Garzarella wrote:
> > > -		vhost_add_used(vq, head, sizeof(pkt->hdr) + pkt->len);
> > > +		vhost_add_used(vq, head, sizeof(pkt->hdr) + payload_len);
> > >  		added = true;
> > >  
> > > +		pkt->off += payload_len;
> > > +
> > > +		/* If we didn't send all the payload we can requeue the packet
> > > +		 * to send it with the next available buffer.
> > > +		 */
> > > +		if (pkt->off < pkt->len) {
> > > +			spin_lock_bh(&vsock->send_pkt_list_lock);
> > > +			list_add(&pkt->list, &vsock->send_pkt_list);
> > > +			spin_unlock_bh(&vsock->send_pkt_list_lock);
> > > +			continue;
> > 
> > The virtio_transport_deliver_tap_pkt() call is skipped.  Packet capture
> > should see the exact packets that are delivered.  I think this patch
> > will present one large packet instead of several smaller packets that
> > were actually delivered.
> 
> I'll modify virtio_transport_build_skb() to take care of pkt->off
> and reading the payload size from the virtio_vsock_hdr.
> Otherwise, should I introduce another field in virtio_vsock_pkt to store
> the payload size?

I don't remember the details but I trust you'll pick a good way of doing
it.

Stefan

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