Re: [nfsv4] Genart last call review of draft-ietf-nfsv4-rpcrdma-cm-pvt-data-06

Suhas Nandakumar <suhasietf@gmail.com> Wed, 29 January 2020 05:04 UTC

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From: Suhas Nandakumar <suhasietf@gmail.com>
Date: Tue, 28 Jan 2020 21:03:55 -0800
Message-ID: <CAMRcRGR2XkudwuWczgHbF23=E6tAgrzMrUNDNTjJbVR=bmhung@mail.gmail.com>
To: Chuck Lever <chuck.lever@oracle.com>
Cc: gen-art@ietf.org, draft-ietf-nfsv4-rpcrdma-cm-pvt-data.all@ietf.org, nfsv4@ietf.org, last-call@ietf.org
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Subject: Re: [nfsv4] Genart last call review of draft-ietf-nfsv4-rpcrdma-cm-pvt-data-06
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Thanks Chuck for the response. Please see inline

On Tue, Jan 28, 2020 at 7:52 AM Chuck Lever <chuck.lever@oracle.com> wrote:

> Hi Suhas -
>
> Thanks for your review and comments! My responses are below.
>
>
> > On Jan 27, 2020, at 2:37 PM, Suhas Nandakumar via Datatracker <
> noreply@ietf.org> wrote:
> >
> > Reviewer: Suhas Nandakumar
> > Review result: Ready with Nits
> >
> > I am the assigned Gen-ART reviewer for this draft. The General Area
> > Review Team (Gen-ART) reviews all IETF documents being processed
> > by the IESG for the IETF Chair.  Please treat these comments just
> > like any other last call comments.
> >
> > For more information, please see the FAQ at
> >
> > <https://trac.ietf.org/trac/gen/wiki/GenArtfaq>.
> >
> > Document: draft-ietf-nfsv4-rpcrdma-cm-pvt-data-??
> > Reviewer: Suhas Nandakumar
> > Review Date: 2020-01-27
> > IETF LC End Date: 2020-01-27
> > IESG Telechat date: Not scheduled for a telechat
> >
> > Summary: Thanks for the work. This document is clear in the problem to be
> > solved . This document is ready to be published as it-is, however I do
> have few
> > clarification questions for my own understanding
> >
> > Major issues:
> >
> > Minor issues:
> >
> > Nits/editorial comments:
> > 1. The draft doesn't specify normative procedures on sender/receiver
> behavior
> > when certain fields are missing (say size of all zeroes). Should the
> draft say
> > recommended procedures for handling these scenarios ?
>
> Section 4 defines the format, which is fixed in size. Section 4.1.1 in
> particular mandates the behavior when a perfectly-formed RPC-over-RDMA
> private message is not received.
>
> Zero is a permitted value for the size fields. Section 5.2 explains how
> to compute the actual buffer size. If those fields contain zero, the
> actual send and receive buffer sizes would be 1024 octets.
>
>
[Suhas] I am not sure if i am reading it right here. Section 5.2 would
result in the
value of -1 if the min of the values is Zero (0/1024 - 1). Isn't it so ?


> "Recommended procedures" are scattered about, but IMO the cases are
> covered appropriately. If you see one that isn't, or one that could be
> made more clear, please let me know.
>
>
> > 2. Also i didn't see fallback procedures to be followed when the server
> > reported size isn't of much use to the sender of the data . In such case
> the
> > sender might decide to go with existing explicit RDMA data transfer
> operations
> > instead of failing the connection ?
>
> If I understand your question, you mean when an RPC message to be
> transmitted is larger than the buffer sizes reported in the private
> data. Section 3.5 of RFC 8166 explains how the RPC-over-RDMA protocol
> handles that situation.
>
> I see the confusion: Section 3.1 of the current document could be more
> precise about the risks of exceeding the inline threshold size. The
> second paragraph could instead read:
>
> "If an incoming RDMA message exceeds the size of a receiver's inline
> threshold, the receive operation fails, and the RDMA provider typically
> terminates the connection.  To convey an RPC message larger than a
> receiver's inline threshold without risking receive failure, the sender
> must use explicit RDMA data transfer operations, which are more expensive
> than RDMA Send."
>

[Suhas] This works great. Thanks for adding the clarification

>
>
> --
> Chuck Lever
>
>
>
>