Yeah, that seemed to do the trick, thank you. I'm curious though, is there a constant somewhere in code that indicates what the maximum size the PML header can be? I appreciate it's 32 right now, but I never feel right just hard coding that in.
On the descriptor you can set a number of iovec containing the raw data. You don't have to make it contiguous prior to calling up in the PML. I think the PML header has to be contiguous, so you have to make sure that the first 32 bytes of the message are contiguous.
On Apr 12, 2009, at 21:58 , Timothy Hayes wrote:
I was wondering if someone might be able to shed some light on a couple of questions I have.
When you receive a fragment/base_descriptor in a BTL module, is the raw data allowed to be fragmented when you invoke the callback function? By that I mean, I'm using a circular buffer in each endpoint so sometimes data loops back around. Currently I'm doing a two step copy: from my socket to the circular buffer and then from the circular buffer to the fragment. This actually effects my total throughput quite a bit, it would be much nicer to just point to the buffer instead. When I tried using two base_segments to point to the start and end of buffer I got some pretty strange errors. I'm just wondering if someone could confirm or deny that you can or can't do this, maybe those errors were down to human error instead.
There is no way to say don't use me "at all" anymore. This is per peer based, so you will have to return an error on every peer. Try returning OMPI_ERR_OUT_OF_RESOURCE from all functions that allocate descriptors (_alloc, _prepare_src and _prepare_dst), and the PML will end-up removing this BTL from the list.
My other question is about the BTL failover system. Would someone be able to briefly explain how it works or maybe point me to some docs? I'm actually expecting the file descriptors in my module to fail a certain point during an Open MPI job and I'd like my BTL module to fail gracefully and allow the TCP module to take over in its place. I'm not sure how to explicitly make the the BTL module say to the rest of Open MPI "don't use my anymore" though.
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