[ovs-discuss] Maximum Number of Queues per Port

Ben Pfaff blp at nicira.com
Thu May 28 19:27:01 UTC 2015


Linux queues have 32-bit numbers divided into two 16-bit parts.  For the
qdiscs currently configured by OVS, only one of the parts is really
useful, so that's roughly 65000 queues.

On Thu, May 28, 2015 at 07:50:40PM +0100, Daniel Caixinha wrote:
> Hello Ben. Thank you for your help. Can you tell me what is the bottleneck
> in the Linux QoS configuration made by OVS? It is always about 65000
> queues? Or depends on RAM capacity (or disk)?
> 
> Thank you and my best regards,
> 
> Daniel
> 
> 
> 
> 2015-05-28 16:17 GMT+01:00 Ben Pfaff <blp at nicira.com>:
> 
> > On Wed, May 27, 2015 at 04:10:45PM +0100, Daniel Caixinha wrote:
> > > I am using OVS in my research work and I plan to run a simulation where I
> > > create a high number of queues in each port (to support BW slicing) of
> > each
> > > OVS instance. Can somebody please tell me what is the maximum number of
> > > queues per port in OVS? And what is the reason for that maximum?
> >
> > OVS uses Linux's QoS, so the main limitation is Linux.  I think that the
> > way that OVS configures Linux QoS limits it to about 65000 queues.
> >
> > OpenFlow is limited to about 4 billion queues.  That's mainly Justin
> > Pettit's fault, as the guy who said, "Four billion queues ought to be
> > enough for anyone":
> >
> > https://mailman.stanford.edu/pipermail/openflow-spec/2009-August/000394.html
> >



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