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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