[openib-general] Re: SDP Performance

[Libor Michalek]

On Fri, Apr 08, 2005 at 03:37:32PM -0400, Hal Rosenstock wrote:
> Hi Libor,
> 
> A couple of questions about SDP performance:
> 
> 1. When running the AIO version of TTCP, there appears to be a bandwidth
> degradation when using buffer sizes from about 5K to 13K. Do you see
> this too ? If so, is there an explanation for this ?

  This would be the result of transitioning from buffered to zcopy mode
at 5K, which is the zcopy threshold. You can change the threshold with
a socket option, which is exposed in ttcp.aio.c using the -z option. I
was not planning on spending time to determine the correct value of the
default threshold until the code stabalized a bit. At this point I'm
investigating what appears to be an RDMA going into an incorrect location.

> 2. Also, is there a program you use to measure SDP latency ?

  I've used netperf in the past which has a roundtrip test to
measure latency using the regular sockets API. I don't have an
AIO latency test handy at the moment, but I could fix one up
and place it in the examples directory...

-Libor