* Question about QoS hardware offload
@ 2021-12-15 17:38 Naveen Mamindlapalli
2021-12-15 21:21 ` Dave Taht
0 siblings, 1 reply; 2+ messages in thread
From: Naveen Mamindlapalli @ 2021-12-15 17:38 UTC (permalink / raw)
To: lartc, netdev; +Cc: jhs, maximmi
Hi,
Our NIC hardware provides a hierarchical QoS tree for each physical
link with strict
priority and DRR scheduling & also supports traffic shaping at each
level. I'm curious what the closest qdisc that supports the above
functionalities for offloading to hardware. I looked into htb/drr/prio
qdiscs, but each qdisc supports a subset of the functionality enabled
by our hardware.
As per my understanding, The HTB hardware offload is used for shaping
rather than scheduling (strict priority/DRR).
The PRIO qdisc seems to support strict priority but not DRR. Similarly
DRR doesn't support strict priority.
Please advise on how to effectively offload all the features.
Is the ETS - Enhanced Transmission Selection scheduler a better fit if
we simply need to offload scheduling with strict priority and DRR?
Thanks,
Naveen
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Question about QoS hardware offload
2021-12-15 17:38 Question about QoS hardware offload Naveen Mamindlapalli
@ 2021-12-15 21:21 ` Dave Taht
0 siblings, 0 replies; 2+ messages in thread
From: Dave Taht @ 2021-12-15 21:21 UTC (permalink / raw)
To: Naveen Mamindlapalli
Cc: lartc, Linux Kernel Network Developers, Jamal Hadi Salim, maximmi
On Wed, Dec 15, 2021 at 12:46 PM Naveen Mamindlapalli
<naveen130617.lkml@gmail.com> wrote:
>
> Hi,
>
> Our NIC hardware provides a hierarchical QoS tree for each physical
> link with strict
> priority and DRR scheduling & also supports traffic shaping at each
> level. I'm curious what the closest qdisc that supports the above
> functionalities for offloading to hardware. I looked into htb/drr/prio
> qdiscs, but each qdisc supports a subset of the functionality enabled
> by our hardware.
>
> As per my understanding, The HTB hardware offload is used for shaping
> rather than scheduling (strict priority/DRR).
Correct.
> The PRIO qdisc seems to support strict priority but not DRR. Similarly
> DRR doesn't support strict priority.
My assumption is your hardware does not do 5 tuple FQ for the DRR, but
leverages the dscp field?
Instead, linux pretty much does a 5 tuple hash universally now for
packet steering (RPS) and in the sch_fq and fq_codel qdiscs.
I am not really big on strict priority with dscp, as whenever someone
lucks into the right dscp value they get most of the bandwidth, and
it's
more or less a matter of historical accident that the support in
mqprio/pfifo_fast is not more abused in the field. But that's me.
>
> Please advise on how to effectively offload all the features.
>
> Is the ETS - Enhanced Transmission Selection scheduler a better fit if
> we simply need to offload scheduling with strict priority and DRR?
Of course, my dream is to see 5 tuple fq-codel or cake land in some
offload somewhere.
I don't know enough about how when and where ets is used, it's pretty
new, and I'd lke to know more.
>
> Thanks,
> Naveen
--
I tried to build a better future, a few times:
https://wayforward.archive.org/?site=https%3A%2F%2Fwww.icei.org
Dave Täht CEO, TekLibre, LLC
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