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Date: Tue, 11 Oct 2022 15:28:38 +0200 From: "Wilczynski, Michal" <michal.wilczynski@...el.com> To: Jiri Pirko <jiri@...nulli.us> CC: Edward Cree <ecree.xilinx@...il.com>, <netdev@...r.kernel.org>, <alexandr.lobakin@...el.com>, <dchumak@...dia.com>, <maximmi@...dia.com>, <simon.horman@...igine.com>, <jacob.e.keller@...el.com>, <jesse.brandeburg@...el.com>, <przemyslaw.kitszel@...el.com>, Jakub Kicinski <kuba@...nel.org> Subject: Re: [RFC PATCH net-next v4 2/6] devlink: Extend devlink-rate api with queues and new parameters On 9/29/2022 9:12 AM, Jiri Pirko wrote: > Wed, Sep 28, 2022 at 01:47:03PM CEST, michal.wilczynski@...el.com wrote: >> >> On 9/26/2022 1:51 PM, Jiri Pirko wrote: >>> Thu, Sep 15, 2022 at 08:41:52PM CEST, michal.wilczynski@...el.com wrote: >>>> On 9/15/2022 5:31 PM, Edward Cree wrote: >>>>> On 15/09/2022 14:42, Michal Wilczynski wrote: >>>>>> Currently devlink-rate only have two types of objects: nodes and leafs. >>>>>> There is a need to extend this interface to account for a third type of >>>>>> scheduling elements - queues. In our use case customer is sending >>>>>> different types of traffic on each queue, which requires an ability to >>>>>> assign rate parameters to individual queues. >>>>> Is there a use-case for this queue scheduling in the absence of a netdevice? >>>>> If not, then I don't see how this belongs in devlink; the configuration >>>>> should instead be done in two parts: devlink-rate to schedule between >>>>> different netdevices (e.g. VFs) and tc qdiscs (or some other netdev-level >>>>> API) to schedule different queues within each single netdevice. >>>>> Please explain why this existing separation does not support your use-case. >>>>> >>>>> Also I would like to see some documentation as part of this patch. It looks >>>>> like there's no kernel document for devlink-rate unlike most other devlink >>>>> objects; perhaps you could add one? >>>>> >>>>> -ed >>>> Hi, >>>> Previously we discussed adding queues to devlink-rate in this thread: >>>> https://lore.kernel.org/netdev/20220704114513.2958937-1-michal.wilczynski@intel.com/T/#u >>>> In our use case we are trying to find a way to expose hardware Tx scheduler >>>> tree that is defined >>>> per port to user. Obviously if the tree is defined per physical port, all the >>>> scheduling nodes will reside >>>> on the same tree. >>>> >>>> Our customer is trying to send different types of traffic that require >>>> different QoS levels on the same >>> Do I understand that correctly, that you are assigning traffic to queues >>> in VM, and you rate the queues on hypervisor? Is that the goal? >> Yes. > Why do you have this mismatch? If forces the hypervisor and VM admin to > somehow sync upon the configuration. That does not sound correct to me. Thanks for a feedback, this is going to be changed > > >>> >>>> VM, but on a different queues. This requires completely different rate setups >>>> for that queue - in the >>>> implementation that you're mentioning we wouldn't be able to arbitrarily >>>> reassign the queue to any node. >>>> Those queues would still need to share a single parent - their netdev. This >>> So that replies to Edward's note about having the queues maintained >>> within the single netdev/vport, correct? >> Correct ;) > Okay. So you don't really need any kind of sharing devlink might be able > to provide. > > From what you say and how I see this, it's clear. You should handle the > per-queue shaping on the VM, on netdevice level, most probably by > offloading some of the TC qdisc. I talked with architect, and this is how the solution will end up looking like, I'm not sure however whether creating a hardware-only qdisc is allowed ? Btw, thanks everyone for valuable feedback, I've resend the patch without the queue support, https://lore.kernel.org/netdev/20221011090113.445485-1-michal.wilczynski@intel.com/ BR, Michał > >>> >>>> wouldn't allow us to fully take >>>> advantage of the HQoS and would introduce arbitrary limitations. >>>> >>>> Also I would think that since there is only one vendor implementing this >>>> particular devlink-rate API, there is >>>> some room for flexibility. >>>> >>>> Regarding the documentation, sure. I just wanted to get all the feedback >>> >from the mailing list and arrive at the final >>>> solution before writing the docs. >>>> >>>> BTW, I'm going to be out of office tomorrow, so will respond in this thread >>>> on Monday. >>>> BR, >>>> Michał >>>> >>>>
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