Re: [dpdk-dev] [RFC PATCH 0/1] Dataplane Workload Accelerator library

[Thomas Monjalon <thomas@monjalon.net>]

31/10/2021 22:13, Jerin Jacob:
> On Mon, Nov 1, 2021 at 1:04 AM Thomas Monjalon <thomas@monjalon.net> wrote:
> >
> > 31/10/2021 15:01, Jerin Jacob:
> > > Since rte_flow already has the TLV concept it may not be new to DPDK.
> >
> > Where is there TLV in rte_flow?
> 
> struct rte_flow_item {
>         enum rte_flow_item_type type; /**< Item type. */
>         const void *spec; /**< Pointer to item specification structure. */
> 
> Type is the tag here and the spec is the value here. Length is the
> size of the specification structure.
> rte_flows spec does not support/need zero length variable at the end
> of spec structure,
> that reason for not embedding explicit length value as it is can be
> derived from sizeof(specification structure).

Ah OK I see what you mean.
But rte_flow_item is quite limited,
it is not the kind of TLV with multiple levels of nesting.
Do you need nesting of objects in DWA?

> > > I really liked rte_flow enablement of ABI combability and its ease of adding
> > > new stuff. Try to follow similar stuff which is proven in DPDK.
> > > Ie. New profile creation will very easy, it will be a matter of identifying
> > > the TLVs and their type and payload, rather than everyone comes with
> > > new APIs in every profile.
> > >
> > > > Why not use protobuf and its IDL to specify the interface?
> >
> > Yes I think it is important to discuss alternatives,
> > and at least get justifications of why TLV is chosen among others.
> 
> Yes. Current list is
> 
> 1) Very easy to enable ABI compatibility.
> 2) If it needs to be transported over network etc it needs to be
> packed so that way it is easy for implementation to do that
> with TLV also gives better performance in such
> cases by avoiding reformatting or possibly avoiding memcpy etc.
> 3) It is easy to plugin with another high-level programing language as
> just one API.
> 4) Easy to decouple DWA core library functionalities from profile.
> 5) Easy to enable asynchronous scheme using request and response TLVs.
> 6) Most importantly, We could introduce type notion with TLV
> (connected with the type of message  See TYPE_ATTACHED, TYPE_STOPPED,
> TYPE_USER_PLANE etc ),
> That way, we can have a uniform outlook of profiles instead of each profile
> coming with a setup of its own APIs and __rules__ on the state machine.
> I think, for a framework to leverage communication mechanisms and other
> aspects between profiles, it's important to have some synergy between profiles.
> 7) No Additional library dependencies like gRPC, protobuf
> 8) Provide driver to implement the optimized means of supporting different
> transport such as Ethernet, Shared memory, PCIe DMA style HW etc.
> 9) Avoid creating endless APIs and their associated driver function
> calls for each
> profile APIs.