[openib-general] Re: [PATCH] [SRP] support for it_iu length negotiation

[John Kingman]

On Tue, 1 Nov 2005, Roland Dreier wrote:

>My objections are the following (as I said in my previous mail):
> - I don't like allocating a 1 KB IU for every send IU, since most of
>   that memory will probably never be used.

I have no problem with changing the 1K IU to some other value.  I
would rather see this max IU size as a module parameter, however,
so that it may be changed without having to rebuild the module.

> - I'm not convinced that it's _ever_ a win to have the target do
>   another RDMA to fetch the indirect buffer list.  You need to
>   convince me that it's not better to simply tell the upper layers
>   what the limit on s/g list length is to fit in the current IU size.

If you agree that it_iu size negotiation is OK, then the case where
you connect to a target with a smaller it_iu size than ib_srp was
built with leaves some number of indirect descriptors in the position
of only being available to the target via RDMA.  This would probably
be considered a win compared to not talking to the target at all.  :-)

John