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Subject: Re: [OMPI devel] 1.3.1 -- bad MTT from Cisco
From: Ralph Castain (rhc_at_[hidden])
Date: 2009-03-11 11:34:46


I'll run some tests with 1.3.1 on one of our systems and see if it
shows up there. If it is truly rare and was in 1.3.0, then I
personally don't have a problem with it. Got bigger problems with
hanging collectives, frankly - and we don't know how the sm changes
will affect this problem, if at all.

On Mar 11, 2009, at 7:50 AM, Terry Dontje wrote:

> Jeff Squyres wrote:
>> So -- Brad/George -- this technically isn't a regression against
>> v1.3.0 (do we know if this can happen in 1.2? I don't recall
>> seeing it there, but if it's so elusive... I haven't been MTT
>> testing the 1.2 series in a long time). But it is a nonzero problem.
>>
> I have not seen 1.2 fail with this problem but I honestly don't know
> if that is a fluke or not.
>
> --td
>
>> Should we release 1.3.1 without a fix?
>>
>
>>
>> On Mar 11, 2009, at 7:30 AM, Ralph Castain wrote:
>>
>>> I actually wasn't implying that Eugene's changes -caused- the
>>> problem,
>>> but rather that I thought they might have -fixed- the problem.
>>>
>>> :-)
>>>
>>>
>>> On Mar 11, 2009, at 4:34 AM, Terry Dontje wrote:
>>>
>>> > I forgot to mention that since I ran into this issue so long ago I
>>> > really doubt that Eugene's SM changes has caused this issue.
>>> >
>>> > --td
>>> >
>>> > Terry Dontje wrote:
>>> >> Hey!!! I ran into this problem many months ago but its been so
>>> >> elusive that I've haven't nailed it down. First time we saw this
>>> >> was last October. I did some MTT gleaning and could not find
>>> >> anyone but Solaris having this issue under MTT. What's
>>> interesting
>>> >> is I gleaned Sun's MTT results and could not find any of these
>>> >> failures as far back as last October.
>>> >> What it looked like to me was that the shared memory segment
>>> might
>>> >> not have been initialized with 0's thus allowing one of the
>>> >> processes to start accessing addresses that did not have an
>>> >> appropriate address. However, when I was looking at this I was
>>> >> told the mmap file was created with ftruncate which essentially
>>> >> should 0 fill the memory. So I was at a loss as to why this was
>>> >> happening.
>>> >>
>>> >> I was able to reproduce this for a little while manually
>>> setting up
>>> >> a script that ran and small np=2 program over and over for
>>> sometime
>>> >> under 3-4 days. But around November I was unable to reproduce
>>> the
>>> >> issue after 4 days of runs and threw up my hands until I was able
>>> >> to find more failures under MTT which for Sun I haven't.
>>> >>
>>> >> Note that I was able to reproduce this issue with both SPARC and
>>> >> Intel based platforms.
>>> >>
>>> >> --td
>>> >>
>>> >> Ralph Castain wrote:
>>> >>> Hey Jeff
>>> >>>
>>> >>> I seem to recall seeing the identical problem reported on the
>>> user
>>> >>> list not long ago...or may have been the devel list. Anyway, it
>>> >>> was during btl_sm_add_procs, and the code was segv'ing.
>>> >>>
>>> >>> I don't have the archives handy here, but perhaps you might
>>> search
>>> >>> them and see if there is a common theme here. IIRC, some of
>>> >>> Eugene's fixes impacted this problem.
>>> >>>
>>> >>> Ralph
>>> >>>
>>> >>>
>>> >>> On Mar 10, 2009, at 7:49 PM, Jeff Squyres wrote:
>>> >>>
>>> >>>> On Mar 10, 2009, at 9:13 PM, Jeff Squyres (jsquyres) wrote:
>>> >>>>
>>> >>>>> Doh -- I'm seeing intermittent sm btl failures on Cisco 1.3.1
>>> >>>>> MTT. :-
>>> >>>>> ( I can't reproduce them manually, but they seem to only
>>> happen
>>> >>>>> in a
>>> >>>>> very small fraction of overall MTT runs. I'm seeing at
>>> least 3
>>> >>>>> classes of errors:
>>> >>>>>
>>> >>>>> 1. btl_sm_add_procs.c:529 which is this:
>>> >>>>>
>>> >>>>> if(mca_btl_sm_component.fifo[j]
>>> [my_smp_rank].head_lock !=
>>> >>>>> NULL) {
>>> >>>>>
>>> >>>>> j = 3, my_smp_rank = 1. mca_btl_sm_component.fifo[j]
>>> [my_smp_rank]
>>> >>>>> appears to have a valid value in it (i.e., .fifo[3][0] =
>>> >>>>> x, .fifo[3]
>>> >>>>> [1] = x+offset, .fifo[3][2] = x+2*offset, .fifo[3][3] = x
>>> >>>>> +3*offset.
>>> >>>>> But gdb says:
>>> >>>>>
>>> >>>>> (gdb) print mca_btl_sm_component.fifo[j][my_smp_rank]
>>> >>>>> Cannot access memory at address 0x2a96b73050
>>> >>>>>
>>> >>>>
>>> >>>>
>>> >>>> Bah -- this is a red herring; this memory is in the shared
>>> memory
>>> >>>> segment, and that memory is not saved in the corefile. So of
>>> >>>> course gdb can't access it (I just did a short controlled test
>>> >>>> and proved this to myself).
>>> >>>>
>>> >>>> But I don't understand why I would have a bunch of tests that
>>> all
>>> >>>> segv at btl_sm_add_procs.c:529. :-(
>>> >>>>
>>> >>>> --
>>> >>>> Jeff Squyres
>>> >>>> Cisco Systems
>>> >>>>
>>> >>>> _______________________________________________
>>> >>>> devel mailing list
>>> >>>> devel_at_[hidden]
>>> >>>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>>> >>>
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>>> >>
>>> >>
>>> >
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>>
>>
>
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