> -----Original Message----- > From: Jerin Jacob <jerinjac...@gmail.com> > Sent: Thursday, June 15, 2023 4:38 PM > To: Zhang, Qi Z <qi.z.zh...@intel.com> > Cc: Ori Kam <or...@nvidia.com>; NBU-Contact-Thomas Monjalon (EXTERNAL) > <tho...@monjalon.net>; david.march...@redhat.com; Richardson, Bruce > <bruce.richard...@intel.com>; jer...@marvell.com; ferruh.yi...@amd.com; > Mcnamara, John <john.mcnam...@intel.com>; Zhang, Helin > <helin.zh...@intel.com>; techbo...@dpdk.org; dev@dpdk.org; Ivan Malov > <ivan.ma...@arknetworks.am> > Subject: Re: [RFC] lib/ethdev: introduce table driven APIs > > On Thu, Jun 15, 2023 at 1:12 PM Zhang, Qi Z <qi.z.zh...@intel.com> wrote: > > > > > > > > > -----Original Message----- > > > From: Jerin Jacob <jerinjac...@gmail.com> > > > Sent: Thursday, June 15, 2023 2:21 PM > > > To: Zhang, Qi Z <qi.z.zh...@intel.com> > > > Cc: Ori Kam <or...@nvidia.com>; NBU-Contact-Thomas Monjalon > > > (EXTERNAL) <tho...@monjalon.net>; david.march...@redhat.com; > > > Richardson, Bruce <bruce.richard...@intel.com>; jer...@marvell.com; > > > ferruh.yi...@amd.com; Mcnamara, John <john.mcnam...@intel.com>; > > > Zhang, Helin <helin.zh...@intel.com>; techbo...@dpdk.org; > > > dev@dpdk.org; Ivan Malov <ivan.ma...@arknetworks.am> > > > Subject: Re: [RFC] lib/ethdev: introduce table driven APIs > > > > > > On Thu, Jun 15, 2023 at 11:33 AM Zhang, Qi Z <qi.z.zh...@intel.com> > wrote: > > > > > > > > Hi Jerin: > > > > > > Hi Qi > > > > > > > > > > > > -----Original Message----- > > > > > From: Jerin Jacob <jerinjac...@gmail.com> > > > > > Sent: Thursday, June 15, 2023 12:58 PM > > > > > To: Zhang, Qi Z <qi.z.zh...@intel.com> > > > > > Cc: Ori Kam <or...@nvidia.com>; NBU-Contact-Thomas Monjalon > > > > > (EXTERNAL) <tho...@monjalon.net>; david.march...@redhat.com; > > > > > Richardson, Bruce <bruce.richard...@intel.com>; > > > > > jer...@marvell.com; ferruh.yi...@amd.com; Mcnamara, John > > > > > <john.mcnam...@intel.com>; Zhang, Helin <helin.zh...@intel.com>; > > > > > techbo...@dpdk.org; dev@dpdk.org; Ivan Malov > > > > > <ivan.ma...@arknetworks.am> > > > > > Subject: Re: [RFC] lib/ethdev: introduce table driven APIs > > > > > > > > > > On Thu, Jun 15, 2023 at 7:55 AM Zhang, Qi Z > > > > > <qi.z.zh...@intel.com> > > > wrote: > > > > > > > > > > > > Hi Ori: > > > > > > > > > > > > Thank you for your review! > > > > > > Comment inline. > > > > > > Please let me know if anything I missed. > > > > > > > > > > > > Thanks > > > > > > Qi > > > > > > > > > > > > > -----Original Message----- > > > > > > > From: Ori Kam <or...@nvidia.com> > > > > > > > Sent: Thursday, June 15, 2023 2:31 AM > > > > > > > To: Zhang, Qi Z <qi.z.zh...@intel.com>; NBU-Contact-Thomas > > > > > > > Monjalon > > > > > > > (EXTERNAL) <tho...@monjalon.net>; > david.march...@redhat.com; > > > > > > > Richardson, Bruce <bruce.richard...@intel.com>; > > > > > > > jer...@marvell.com; ferruh.yi...@amd.com > > > > > > > Cc: Mcnamara, John <john.mcnam...@intel.com>; Zhang, Helin > > > > > > > <helin.zh...@intel.com>; techbo...@dpdk.org; dev@dpdk.org > > > > > > > Subject: RE: [RFC] lib/ethdev: > > > > > > > > > > > > > > Hi Qi, > > > > > > > > > > > > > > > > > > > > > 1. it may be useful to get some general calling flow what > > > > > > > comes from the application, what comes from the compiler. > > > > > > > Simple example will be good. > > > > > > > > > > > > An example of decap VXLAN TCP flow is explained in problem > > > > > > statement > > > > > > (http://mails.dpdk.org/archives/dev/2023-May/267719.html) > > > > > > covering the following information. > > > > > > > > > > > > 1. the p4 source code, the definition of the table and actions 2. > > > > > > the table / action hints generated by the compiler, details to > > > > > > each > > > fields. > > > > > > 3. How the Control Plane Application utilizes the P4 Runtime > > > > > > API to program the rule with the respective table and action > > > > > > IDs > > > > > > > > > > > > The DPDK PMD is responsible for loading the hints generated by > > > > > > the > > > > > compiler. > > > > > > This enables the PMD to accept requests from the P4 Runtime > > > > > > and reject > > > > > any incompatible request. > > > > > > > > > > I see two different types of device/system category > > > > > > > > > > 1) HW + SW/FW combination that really understands p4 structures > > > > > and job of the driver to is to give work to HW/SW as p4 > > > > > structure generated from vendor specific compiler and runtime > > > > > gRPC message > > > > > 2) Existing HW and SW drivers implements rte-flow driver. > > > > > > > > > > For item (1), if end user application is using P4 program and P4 > > > > > runtime and this is _API contract_ to application, Not sure why > > > > > end user care it is DPDK PMD or not? > > > > > > > > That's true. DPDK as a platform that manage the hardware, it is > > > > required to > > > provide a channel that connects applications with the hardware > > > responsible for implementing the contract. > > > > In this context, the PMD (ethdev) serves as the conduit that can > > > > fulfill this > > > requirement. > > > > > > I meant vdev + rawdev combo can be used to talk to FW. > > > > OK, I will comment this together when vdev + rawdev be mentioned again > at below. > > > > > > > > > > If driver writer care about using DPDK for driver framework for > > > > > EAL services, simply using vdev etc would be enough. Right? > > > > > > > > I may not fully understand this, a vdev should have a device type, > > > > I didn't > > > see any issue for a ethdev vdev to implement the table-driven APIs. > > > > > > See above. > > > > > > There is a lot of overlap between rte_flow and table driven API is the > issue. > > > To make things worst, there is also lib/table/ API. > > > > I assume this is just the concern about naming? At least, they are target to > different usage. > > Not the naming of library. Duplicate functional APIs to express a specific use > case for HW. > > > > > > > > > > > > > > > > > > > > For item (2), I think, interest is how to offload p4 workload to > > > > > rte_flow. So that _existing_ drivers implements rte_flow can > > > > > support > > > > > p4 naturally in addition to existing rte_flow API. If that is > > > > > direction, then we need to the following. > > > > > > > > While the idea of offloading P4 to rte_flow is certainly > > > > interesting, it > > > doesn't seem to directly address our initial problem statement. > > > > The primary objective is to find a solution for offloading > > > > rte_flow into a P4- > > > based pipeline. > > > > > > Isn't same? If not, Please elaborate on "P4 to rte_flow mapping" vs > > > "offloading rte_flow into a P4-based pipeline" > > > > OK I guess the gap here is I may not fully understand is how we > > defined the case of item(2) Existing HW and SW drivers implements rte- > flow driver. > > > > If we assume that the application is not P4-aware, it will consume existing > rte_flow API for flow offloading. In this case, all we need to do is implement > it in the PMD, which will be a highly hardware-specific task. Do you propose > generalizing this common part? > > > > On the other hand, if the application is P4-aware, we can assume that > there won't be a need for translation between P4 tokens and rte_flow > protocols in the PMD. > > I agree, Translation is BAD. There are two elements to that. > 1)if it is p4 aware application, why bother with DPDK abstraction? > 2)Can we use compiler techniques to avoid the cost of translation if P4- > aware path is needed in DPDK. Rather than creating yet another library. In > this context, that would translate to some of your compiler and FW work > making as generic so that _any_ other rte_flow based driver can use and > improve it.
Ok, I would like to gain a better understanding. Below is my current understanding: There are no plans to introduce any new API from DPDK. However, your proposal suggests the creation of a tool, such as a compiler, which would assist in generating a translation layer from P4 table/actions to rte_flow for user application like p4 runtime backend that based on DPDK. Could you provide more details about the design? Specifically, I would like to know what the input for the compiler is and who is responsible for generating that input, as well as the process involved. I apologize if I have not grasped the complete picture, but I would appreciate your patience. > > > > > > > > > > > > > > > > > We have identified two distinct use cases: > > > > > > > > P4-Aware Applications: > > > > > > > > For applications that are already P4 aware, the proposal suggests > > > > the > > > introduction of a new set of APIs to rte_flow. > > > > These APIs aim to facilitate seamless integration between DPDK and > > > > P4 > > > aware applications. > > > > > > Counter argument for that is, If the P4 is API contract then why > > > bother with DPDK abstraction use vdev + rawdev talk to FW as PMD is > > > just passing message to FW. FW is doing the heavy lifting anyway. > > > > We are attempting to generalize the common aspects, considering that P4 > Runtime is a standard API. It appears worthwhile to expose certain APIs that > can assist its backend implementation. > > I agree. If backend is built on top rte_flow and some compiler bits. I think, > multiple consumer can use it. > Otherwise, we are making the API for a p4 FW backend is needed. > > > > I may need some time to understand the concept of vdev +rawdev combo > solution, currently one question in my mind is: in this solution, is above > consideration covered? > > > > Thanks > > Qi > > > > > > > > > > > > > > > > Non-P4 Aware Applications: > > > > > > > > In the case, our focus is on bridging the existing rte_flow API to > > > > the > > > underlying P4 pipeline. > > > > Currently, we haven't identified any significant gaps in the DPDK APIs. > > > > The key challenge lies in handling the translation process within > > > > the PMD > > > > > > > > Thanks > > > > Qi > > > > > > > > > > > > > > a)Improve p4-dpdk compiler backend or add new compiler DPDK > > > backend > > > > > to understand the rte_flow and have helper library in DPDK to > > > > > understand the compiler spec file to translate to rte_flow > > > > > objects b)Similar case for runtime API. i.e Have helper > > > > > functions to translate > > > > > p4 MatchField name etc to appropriate rte_flow objects. > > > > > c)Enhance base rte_flow specification if there are any > > > > > fundamental gaps to express the new pattern or actions (which is > > > > > not specific to > > > > > p4 and applicable for any flow matching use case) > > > > > > > > > > If we introduce compiler in the pipeline, a lot of translation > > > > > will get in the slowpath. And for runtime API, the translation > > > > > primarily will be name to rte_flow object lookup (which is not > > > > > that costly) and using rte_flow_template etc. to amortize the cost by > making it burst. > > > > > > > > > > Just my 2c. > >
