[ofa-general] Non-Signaled RDMA Read (cxgb3)

[Caitlin Bestler]

On Tue, Jul 29, 2008 at 9:47 AM, Felix Marti <felix at chelsio.com> wrote:
>

>
> Roland, AFAIK, even an unsignaled WR generates a CQE when an error
> occurs (and then all subsequent WRs complete in error as well). Doesn't
> that imply that the CQ must be sized assuming that _every_ WR can
> generate a CQE?
>

Yes, that is exactly what application writers should assume.

They should also assume that spurious completion interrupts are possible
(although obviously they should be minimized) and therefore the application
should always be ready be woken up early and find nothing to do.

More complete descriptions that could be used as guidelines can be found
in the DAPL manuals.

About the only thing I think that can be done about this specific quirk is
to document it so that application developers are aware of it, and know that
it is a model-specific limitation and do not think it is a limitation of RDMA
or iWARP. If their application does not need the notification it should
keep requesting unsignaled completion.