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From: Mike Houston (mhouston_at_[hidden])
Date: 2007-03-20 22:54:29

Well, I've managed to get a working solution, but I'm not sure how I got
there. I built a test case that looked like a nice simple version of
what I was trying to do and it worked, so I moved the test code into my
implementation and low and behold it works. I must have been doing
something a little funky in the original pass, likely causing a stack
smash somewhere or trying to do a get/put out of bounds.

If I have any more problems, I'll let y'all know. I've tested pretty
heavy usage up to 128 MPI processes across 16 nodes and things seem to
be behaving. I did notice that single sided transfers seem to be a
little slower than explicit send/recv, at least on GigE. Once I do some
more testing, I'll bring things up on IB and see how things are going.


Mike Houston wrote:
> Brian Barrett wrote:
>> On Mar 20, 2007, at 3:15 PM, Mike Houston wrote:
>>> If I only do gets/puts, things seem to be working correctly with
>>> version
>>> 1.2. However, if I have a posted Irecv on the target node and issue a
>>> MPI_Get against that target, MPI_Test on the posed IRecv causes a
>>> segfaults:
>>> Anyone have suggestions? Sadly, I need to have IRecv's posted. I'll
>>> attempt to find a workaround, but it looks like the posed IRecv is
>>> getting all the data of the MPI_Get from the other node. It's like
>>> the
>>> message tagging is getting ignored. I've never tried posting two
>>> different IRecv's with different message tags either...
>> Hi Mike -
>> I've spent some time this afternoon looking at the problem and have
>> some ideas on what could be happening. I don't think it's a data
>> mismatch (the data intended for the IRecv getting delivered to the
>> Get), but more a problem with the call to MPI_Test perturbing the
>> progress flow of the one-sided engine. I can see one or two places
>> where it's possible this could happen, although I'm having trouble
>> replicating the problem with any test case I can write. Is it
>> possible for you to share the code causing the problem (or some small
>> test case)? It would make me feel considerably better if I could
>> really understand the conditions required to end up in a seg fault
>> state.
>> Thanks,
>> Brian
> Well, I can give you a linux x86 binary if that would do it. The code
> is huge as it's part of a much larger system, so there is no such thing
> as a simple case at the moment, and the code is in pieces an largely
> unrunnable now with all the hacking...
> I basically have one thread spinning on an MPI_Test on a posted IRecv
> while being used as the target to the MPI_Get. I'll see if I can hack
> together a simple version that breaks late tonight. I've just played
> with posting a send to that IRecv, issuing the MPI_Get, handshaking and
> then posting another IRecv and the MPI_Test continues to eat it, but in
> a memcpy:
> #0 0x001c068c in memcpy () from /lib/
> #1 0x00e412d9 in ompi_convertor_pack (pConv=0x83c1198, iov=0xa0,
> out_size=0xaffc1fd8, max_data=0xaffc1fdc) at convertor.c:254
> #2 0x00ea265d in ompi_osc_pt2pt_replyreq_send (module=0x856e668,
> replyreq=0x83c1180) at osc_pt2pt_data_move.c:411
> #3 0x00ea0ebe in ompi_osc_pt2pt_component_fragment_cb
> (pt2pt_buffer=0x8573380) at osc_pt2pt_component.c:582
> #4 0x00ea1389 in ompi_osc_pt2pt_progress () at osc_pt2pt_component.c:769
> #5 0x00aa3019 in opal_progress () at runtime/opal_progress.c:288
> #6 0x00ea59e5 in ompi_osc_pt2pt_passive_unlock (module=0x856e668,
> origin=1, count=1) at osc_pt2pt_sync.c:60
> #7 0x00ea0cd2 in ompi_osc_pt2pt_component_fragment_cb
> (pt2pt_buffer=0x856f300) at osc_pt2pt_component.c:688
> #8 0x00ea1389 in ompi_osc_pt2pt_progress () at osc_pt2pt_component.c:769
> #9 0x00aa3019 in opal_progress () at runtime/opal_progress.c:288
> #10 0x00e33f05 in ompi_request_test (rptr=0xaffc2430,
> completed=0xaffc2434, status=0xaffc23fc) at request/req_test.c:82
> #11 0x00e61770 in PMPI_Test (request=0xaffc2430, completed=0xaffc2434,
> status=0xaffc23fc) at ptest.c:52
> -Mike
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