Re: [dpdk-dev] 4 Traffic classes per Pipe limitation

[Michael Sardo <mike@bandex.io>]

Hello Cristian,

Are the slides shown in that video available? They're very helpful.

-Mike

On Fri, Jun 5, 2015 at 4:50 PM, Dumitrescu, Cristian <
cristian.dumitrescu@intel.com> wrote:

> Hi Avinash,
>
> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Yeddula, Avinash
> > Sent: Friday, June 5, 2015 6:06 PM
> > To: dev@dpdk.org
> > Subject: [dpdk-dev] 4 Traffic classes per Pipe limitation
> >
> > Hi,
> > This is related to the QOS scheduler functionality provided by dpdk.
> >
> > I see a limit on the number of traffic classes to be 4.  I'm exploring
> the
> > available options to increase that limit to 8.
>
> Yes, there are 4x traffic classes (scheduled in strict priority), but each
> traffic class has 4x queues (scheduled using WFQ); for big weight ratios
> between queues (e.g. 1:4 or 1:8, etc), WFQ becomes very similar to strict
> priority, a king of strict priority without starvation. So the 16x queues
> per pipe can be considered 16x sub-traffic-classes.
>
> You might want to watch this video on DPDK QoS:
> https://youtu.be/_PPklkWGugs
>
> >
> > This is what I found when I researched on this topic.
> > The limitation on number's of TC (and pipes) comes from the number of
> > bits available. Since the QoS code overloads the 32 bit RSS field in
> > the mbuf there isn't enough bits to a lot. But then again if you add lots
> > of pipes or subports the memory footprint gets huge.
>
> It is not that simple. The number of 4x traffic classes in deeply built
> into the implementation for performance reasons. Increasing the number of
> bits allocated to traffic class in mbuf->sched would not help.
>
> >
> > Any more info or suggestions on increasing the limit to 8 ?
>
> Yes, look at the 16x pipe queues as 16x (sub)traffic classes.
> >
> > Thanks
> > -Avinash
>