Re: [Cerowrt-devel] [Codel] [Bloat] Latest codel, fq_codel, and pie sim study from cablelabs now available

[Jesper Dangaard Brouer <jbrouer@redhat.com>]

On Mon, 6 May 2013 21:46:35 +0300 Jonathan Morton
<chromatix99@gmail.com> wrote: 
> On 6 May, 2013, at 8:54 pm, Jesper Dangaard Brouer wrote:
> 
> > A flow is considered "new" if no packets for the given flow exists
> > in the queue.  It does not have to be a truly new-flow, it just
> > have to send packets "slow"/paced enough, that the queue is empty
> > when the next packet arrive.
> > 
> > Perhaps VoIP would fit this traffic profile, and thus would work
> > better with the Linux fq_codel implementation, compared to the
> > SFQ-Codel used in the simulation.
> 
> That doesn't work, because the with a sufficient number of BT flows,
> the flow queue containing the VoIP flow is the fullest queue, not the
> emptiest.  That's independent of the number of flow queues, including
> the infinite case.  Think about it carefully.

Yes, I agree.

And as I mentioned, with the fq_codel implementation details, this is
going to hit even earlier, as we have a limited number of flow/hash
queues.

> Looking at the implementation, it does have the problem that the match
> for "if the flow already have packets in the queue" just looks to see
> if the hash bucket is empty.  Thus 2 stream sharing a hash queue throw
> this off.

--
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Sr. Network Kernel Developer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer