[ofw] Which API to use for IB project

[Thomas Peiselt]

Hello,

thank you for your elaborate response.

On Mon, Aug 3, 2009 at 5:22 PM, Tzachi Dar<tzachid at mellanox.co.il> wrote:
> I guess that if you can live with latency of ~5us you should be using SDP which will give you the minimum development effort.

development is only a minor issue -- unless we're talking
developer-years here :-).

>
> If you want to be in the area of ~1us latency you should be using one of the following 3 options IBAL ND or winverbs. I guess that once it comes to latency this are the best choices.

It appears that ND is MS-only and results in even more vendor-lock in,
which we would like to avoid. From the remaining two, IBAL seems to be
the more mature implementation, whereas WV has a bright future. I
personally prefer the latter, all else being equal, especially when
this API is closer to its linux counterpart.

We're currently running XP x64, so 32bit support will not be an issue.

> Please note that to get the best latency one should be using RDMA write and pool on the memory for completion (see the ib_write_lat program for an example).

speaking of example code, is there anything in the trunk demonstrating
the usage of the winverbs api? The docs mention ibv_read_lat and
friends but I'm unable to find these, or anything else using the
winverbs header file.
What about uDAPL? It claims to be a thin layer abstracting
RDMA-enabled communication from the underlying hardware and the API is
OS-independent. Additionally, the endpoint state diagram from the
specification is very close to what we currently have in our tcp/ip
overlapped I/O implementation. Where's the drawback?


Thanks again,

Thomas