Messages in this thread |  | | From | Jose Abreu <> | Subject | RE: [EXT] Re: [v1,net-next, 1/2] ethtool: add setting frame preemption of traffic classes | Date | Fri, 10 Jan 2020 14:35:41 +0000 |
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From: Andre Guedes <andre.guedes@linux.intel.com> Date: Jan/09/2020, 18:04:55 (UTC+00:00)
> Quoting Jose Abreu (2020-01-09 00:59:24) > > From: Andre Guedes <andre.guedes@linux.intel.com> > > Date: Jan/09/2020, 01:07:37 (UTC+00:00) > > > > > After reading all this great discussion and revisiting the 802.1Q and 802.3br > > > specs, I'm now leaning towards to not coupling Frame Preemption support under > > > taprio qdisc. Besides what have been discussed, Annex S.2 from 802.1Q-2018 > > > foresees FP without EST so it makes me feel like we should keep them separate. > > > > I agree that EST and FP can be used individually. But how can you > > specify the hold and release commands for gates without changing taprio qdisc user space API ? > > The 'hold' and 'release' are operations from the GCL, which is part of EST. So > they should still be specified via taprio. No changing in the user space API is > required since these operations are already supported in taprio API. What is > missing today is just the 'tc' side of it, which you already have a patch for > it.
OK. Should we ask to merge it as-is then ?
> > > Regarding the FP configuration knobs, the following seems reasonable to me: > > > * Enable/disable FP feature > > > * Preemptable queue mapping > > > * Fragment size multiplier > > > > > > I'm not sure about the knob 'timers (hold/release)' described in the quotes > > > above. I couldn't find a match in the specs. If it refers to 'holdAdvance' and > > > 'releaseAdvance' parameters described in 802.1Q-2018, I believe they are not > > > configurable. Do we know any hardware where they are configurable? > > > > Synopsys' HW supports reconfiguring these parameters. They are, however, > > fixed independently of Queues. i.e. all queues will have same holdAdvance / releaseAdvance. > > Good to know. Is the datasheet publicly available? If so, could you please > point me to it? I'd like to learn more about the FP knobs provided by > different HW.
I'm afraid its not available unless you are a Synopsys customer. You should however be able to figure out the behavior by reading my patch that adds support for FPE in XGMAC and QoS cores. I can clarify any doubts.
--- Thanks, Jose Miguel Abreu
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