[Qemu-devel] Re: [PATCH 0/5] Fix packet queueing to allow full tap queue drain

[Mark McLoughlin <markmc@redhat.com>]

On Wed, 2009-10-28 at 11:36 +0800, Scott Tsai wrote:
> >         Scott, Sven, if you could test the tap-drain-queue branch from
> > my tree, that would be great:
> >   http://repo.or.cz/w/qemu/markmc.git
> > 
> > Thanks,
> > Mark. 
> 
> Mark,
> I've tested http://repo.or.cz/w/qemu/markmc.git and it indeed works
> for my test case
> (NFS through emulated smc91c111 NIC on arm-integragorcp)

Many thanks for the report and confirming the fix

> How about adding a comment in tap_send() about when
> qemu_send_packet_async() would return 0 and -1?
> 
> I'd also recommend checking for the case of qemu_send_packet_async()
> returning -1 and dropping a packet and have a debug message guarded by
> #ifdef DEBUG_TAP in case the qemu_can_send_packet() check is ever
> removed in future modifications of the code.

Yeah, it's fairly gnarly code alright. I'd prefer to make it more
obvious with something like:

  ret = qemu_send_packet_async();
  switch (ret) {
  case NET_PACKET_AGAIN:
      tap_disable_write_poll();
      return;

  case NET_PACKET_DROP:
      /* drop! */
      return;
  }

Added to my TODO list

> Also, would it be possible to get the stable-0.11 version of the patch
> into the soon to be released Fedora 12? I've written some embedded
> Linux tutorials for Taiwanese consumer electronics developers that
> recommends using qemu on Fedora. Being able to rely on NFS always
> working in Fedora's qmeu packet would really help :)

Filed https://bugzilla.redhat.com/531419 ... I'll pull it in later
today.

qemu-system-arm on F12 works okay then? That's good to know, it's the
first I've heard of someone using it :-)

Thanks,
Mark.