Re: RDMA synchronous operations

[Dotan Barak <dotanba-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hi.

On 24/06/2010 16:36, Andrea Gozzelino wrote:
> Hi all,
>
> I’m testing the latency time of an RDMA system (2 card and 1 switch).
> The connection server/client is established and the code is just as
> mirror on both sides.
>
> The RDMA action scheme is below:
> 1-	client sends a buffer;
> 2-	server receives a buffer;
> 3-	server sends a buffer;
> 4-	client receives a buffer.
>
> The scheme is in a for loop, so after step 4 client repeats step 1.
> On client side I put a clock: t_start is before loop and t_end is after
> loop.
> I consider the round trip time RTT as (t_end-t_start)/NTX where NTX is
> number of transfer (number of loop). The latency time is half RTT, if
> transfer time is negligible, i.e. for small (8 Bytes – 4 Kbytes) buffer
> size and high NTX value (>  10000) is true.
>
> The RDMA communication stops casually with error status 5. It means that
> the send or receive operation on one side (server or client) casually is
> not in time. I summarize post_send and post_receive operation are
> quasi-synchronous. I would like that RDMA operation are completely
> synchronous. I use the completion queue and the acknowledgement event.
>
>    
Do you have any asynchronous event handler on the QP/SRQ?
(maybe there is an error on your QP/SRQ)

Did you get any completion with error before the completion with status 5?

Dotan
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