Roland Dreier wrote:
> 1. Sometimes observe RDMA data transfer stalls of ~ 1.0 second
Could it be an RNR NAK? You didn't really describe your protocol, but
if you use send operations and if you do a send without a matching
receive on the other side, then you might end up stalling the QP for a
while.
Quite possibly, we are using an IBV_QPT_RC transport type. The code
simply adds another work request with ibv_post_srq_recv(...) after each
packet is processed. Am I correct in thinking it should start out with a
stack of work requests in case another packet arrives before the current
one has been processed?
> 2. Creation of a Queue Pair is rejected when I have mapped a region of
> memory greater than about 1.35GB.
I don't really understand this problem. Are you able to map more
memory, and then ibv_create_qp() fails if you do? Later you say
> Ideally, we would like the to be able to write anywhere within a 2GB
> (or larger) shared memory segment. However, when I attempt to do this,
> the call to fails with REJ.
You didn't say which call fails with REJ, and I'm not even sure I
understand what it means to "fail with REJ".
Sorry, I meant to look up in my source code which call was failing but
forgot to paste it into the question. Yes, I can map 2GB of memory but
the call to ibv_create_qp() fails with REJ
On x86-64, the limit on how much memory you can register should be
much higher, closer to 32 GB by default.
That's reassuring. Are there any performance penalties for mapping a
larger region than a smaller region?
- R.
Many thanks for the speedy response.
David Robb
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