Open MPI logo

Open MPI Development Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Development mailing list

Subject: Re: [OMPI devel] 1.3.1 -- bad MTT from Cisco
From: Ralph Castain (rhc_at_[hidden])
Date: 2009-03-11 11:47:58


You know, this isn't the first time we have encountered errors that -
only- appear when running under MTT. As per my other note, we are not
seeing these failures here, even though almost all our users run under
batch/scripts.

This has been the case with at least some of these other MTT-only
errors as well. It can't help but make one wonder if there isn't
something about MTT that is causing these failures to occur. It just
seems too bizarre that a true code problem would -only- show itself
when executing under MTT. You would think that it would have to appear
in a script and/or batch environment as well.

Just something to consider.

On Mar 11, 2009, at 9:38 AM, Jeff Squyres wrote:

> As Terry stated, I think this bugger is quite rare. I'm having a
> helluva time trying to reproduce it manually (over 5k runs this
> morning and still no segv). Ugh.
>
> Looking through the sm startup code, I can't see exactly what the
> problem would be. :-(
>
>
> On Mar 11, 2009, at 11:34 AM, Ralph Castain wrote:
>
>> 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
>> >>> >>>
>> >>> >>> _______________________________________________
>> >>> >>> devel mailing list
>> >>> >>> devel_at_[hidden]
>> >>> >>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>> >>> >>
>> >>> >>
>> >>> >
>> >>> > _______________________________________________
>> >>> > devel mailing list
>> >>> > devel_at_[hidden]
>> >>> > http://www.open-mpi.org/mailman/listinfo.cgi/devel
>> >>>
>> >>> _______________________________________________
>> >>> devel mailing list
>> >>> devel_at_[hidden]
>> >>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>> >>>
>> >>
>> >>
>> >
>> > _______________________________________________
>> > devel mailing list
>> > devel_at_[hidden]
>> > http://www.open-mpi.org/mailman/listinfo.cgi/devel
>>
>> _______________________________________________
>> devel mailing list
>> devel_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>
>
> --
> Jeff Squyres
> Cisco Systems
>
> _______________________________________________
> devel mailing list
> devel_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/devel