Re: [nfsv4] questions about flow control

[Martin Duke <[e-mail]>]

There are tons of people I would trust with this, but I might recommend
Jana Iyengar as a first stop.

On Thu, Apr 29, 2021 at 11:17 AM Chuck Lever III <[e-mail]>
wrote:

> Howdy-
>
> We're working on prototyping RPC/RDMA version two. As many of
> you know, RPC/RDMA uses credit-based flow control.
>
> I've presented to the WG before on the kinds of improvements
> to credit accounting we need to make over version one of
> RPC/RDMA in order to support control plane operations and
> message continuation -- cases where we no longer have
> perfectly symmetrical Call/Reply pairing.
>
> I'm looking at Section 4.2.1.1 of draft-ietf-nfsv4-rpcrdma-version-two
> as it is currently constructed and I'm finding it ...
> underwhelming.
>
> I'm thinking of replacing it with something more akin to the
> original forms of credit-based flow control, as described in
> Chapter 4 of:
>
> https://dl.acm.org/doi/pdf/10.1145/190314.190324
>
> and implemented in the form of Chapter 5 of that paper. The
> rdma_credits field would be filled in with the sender's Vr,
> in both directions, and N2 + N3 would be the credit limit. We
> would need to add some kind of "reset credit accounting"
> message as well.
>
> I'm not feeling confident about this choice, however. Does
> anyone know a person or people who could answer some questions
> about flow control design? Or is there a good reference I could
> read to help me understand fundamentals and common pitfalls?
>
> Many thanks in advance!
>
>
> --
> Chuck Lever
>
>
>
>