[dpdk-dev] 4 Traffic classes per Pipe limitation

[Michael Sardo]

Oops, I should have searched a bit more before asking. I see that they've
already been made available:
http://dpdk.org/ml/archives/dev/attachments/20150423/17a4d8de/attachment-0001.pdf

Thanks.

-Mike

On Sat, Jun 6, 2015 at 5:05 PM, Michael Sardo <mike at bandex.io> wrote:

> 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 at intel.com> wrote:
>
>> Hi Avinash,
>>
>> > -----Original Message-----
>> > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Yeddula, Avinash
>> > Sent: Friday, June 5, 2015 6:06 PM
>> > To: dev at 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
>>
>
>