[dpdk-dev] QoS Question

[Greg Smith <gregsmith@juniper.net>]

Hi DPDK team,

The docs on QoS (http://dpdk.org/doc/guides/prog_guide/qos_framework.html# ) describe the traffic class (TC) as follows:
1 - The  TCs of the same pipe handled in strict priority order.
2 - Upper limit enforced per TC at the pipe level.
3 - Lower priority TCs able to reuse pipe bandwidth currently unused by higher priority TCs.
4 - When subport TC is oversubscribed (configuration time event), pipe TC upper limit is capped to a dynamically adjusted value that is shared by all the subport pipes.

Can someone describe how and when the TC upper limit is "dynamically" changed?

For example, assume there's a 1Gb/s port and a single 1Gb/s subport and 2000 pipes each of 1Mb/s (total pipes = 2Gb/s which is > the 1Gb/s subport which I think means "oversubscribed" as used in the doc). Each Pipe has a single TC.
In that case, would each pipe be shaped to an upper limit of 0.5 Mb/s?
What if there was no traffic on 1999 pipes, would the single active pipe still be limited to 0.5 Mb/s?
What if the number of pipes changes without restarting the OS, how does that change the behavior?

BTW, great docs overall, thanks for writing those up.

Thanks,

Greg Smith