[libfabric-users] memory registration "not needed", with the efa provider?

[Wespetal, Robert]

Hi Greg,

The man page is correct in that the RDM endpoint does not require memory registration. The EFA device does require registrations but the Libfabric provider will do the registration on behalf of the user or copy into pre-registered bounce buffers depending on the protocol used.

There are examples of Libfabric users that require this behavior, for example the Open MPI OFI MTL does not do any memory registrations. I'd cut an issue on GitHub for the error and we can take a look!

Thanks,
Robert

On Mon, 2020-07-27 at 22:53 +0000, Titus, Greg wrote:

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Greetings --

I'm trying to use the efa provider on an AWS instance that has the Elastic Fabric Adaptor high-performance network interface.  In the fi_efa(7) man page for libfabric version 1.9.0amzn1.1 installed on the system it says:
The RDM endpoint does not require memory registration

I was a little in disbelief when I read that, and thus was not surprised when I tried simply not making any memory registration calls and sure enough, got internal errors in libfabric.  So, what does that statement in the man page mean, exactly?   Is there maybe a magic remote key value that means "I didn't register memory."?  I'm just using 0UL, in the absence of any other guidance.

thanks,
greg


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