I like #2 too. But my question was slightly different. Can we incapsulate PMI logic that OMPI use in common/pmi as #2 suggests but have 2 different implementations of this component say common/pmi and common/pmi2? I am asking because I have concerns that this kind of component is not supposed to be duplicated. In this case we could have one common MCA parameter and 2 components as it was suggested by Jeff.
2014-05-08 7:01 GMT+07:00 Ralph Castain <r...@open-mpi.org>: > The desired solution is to have the ability to select pmi-1 vs pmi-2 at > runtime. This can be done in two ways: > > 1. you could have separate pmi1 and pmi2 components in each framework. > You'd want to define only one common MCA param to direct the selection, > however. > > 2. you could have a single pmi component in each framework, calling code > in the appropriate common/pmi location. You would then need a runtime MCA > param to select whether pmi-1 or pmi-2 was going to be used, and have the > common code check before making the desired calls. > > The choice of method is left up to you. They each have their negatives. If > it were me, I'd probably try #2 first, assuming the codes are mostly common > in the individual frameworks. > > > On May 7, 2014, at 4:51 PM, Artem Polyakov <artpo...@gmail.com> wrote: > > Just reread your suggestions in our out-of-list discussion and found that > I misunderstand it. So no parallel PMI! Take all possible code into > opal/mca/common/pmi. > To additionally clarify what is the preferred way: > 1. to create one joined PMI module having a switches to decide what > functiononality to implement. > 2. or to have 2 separate common modules for PMI1 and one for PMI2, and > does this fit opal/mca/common/ ideology at all? > > > 2014-05-08 6:44 GMT+07:00 Artem Polyakov <artpo...@gmail.com>: > >> >> 2014-05-08 5:54 GMT+07:00 Ralph Castain <r...@open-mpi.org>: >> >> Ummm....no, I don't think that's right. I believe we decided to instead >>> create the separate components, default to PMI-2 if available, print nice >>> error message if not, otherwise use PMI-1. >>> >>> I don't want to initialize both PMIs in parallel as most installations >>> won't support it. >>> >> >> Ok, I agree. Beside the lack of support there can be a performance hit >> caused by PMI1 initialization at scale. This is not a case of SLURM PMI1 >> since it is quite simple and local. But I didn't consider other >> implementations. >> >> On May 7, 2014, at 3:49 PM, Artem Polyakov <artpo...@gmail.com> wrote: >>> >>> We discussed with Ralph Joshuas concerns and decided to try automatic >>> PMI2 correctness first as it was initially intended. Here is my idea. The >>> universal way to decide if PMI2 is correct is to compare PMI_Init(.., >>> &rank, &size, ...) and PMI2_Init(.., &rank, &size, ...). Size and rank >>> should be equal. In this case we proceed with PMI2 finalizing PMI1. >>> Otherwise we finalize PMI2 and proceed with PMI1. >>> I need to clarify with SLURM guys if parallel initialization of both >>> PMIs are legal. If not - we'll do that sequentially. >>> In other places we'll just use the flag saying what PMI version to use. >>> Does that sounds reasonable? >>> >>> 2014-05-07 23:10 GMT+07:00 Artem Polyakov <artpo...@gmail.com>: >>> >>>> That's a good point. There is actually a bunch of modules in ompi, opal >>>> and orte that has to be duplicated. >>>> >>>> среда, 7 мая 2014 г. пользователь Joshua Ladd написал: >>>> >>>>> +1 Sounds like a good idea - but decoupling the two and adding all the >>>>> right selection mojo might be a bit of a pain. There are several places in >>>>> OMPI where the distinction between PMI1and PMI2 is made, not only in >>>>> grpcomm. DB and ESS frameworks off the top of my head. >>>>> >>>>> Josh >>>>> >>>>> >>>>> On Wed, May 7, 2014 at 11:48 AM, Artem Polyakov <artpo...@gmail.com> >>>>> wrote: >>>>> >>>>>> Good idea :)! >>>>>> >>>>>> среда, 7 мая 2014 г. пользователь Ralph Castain написал: >>>>>> >>>>>> Jeff actually had a useful suggestion (gasp!).He proposed that we >>>>>> separate the PMI-1 and PMI-2 codes into separate components so you could >>>>>> select them at runtime. Thus, we would build both (assuming both PMI-1 >>>>>> and >>>>>> 2 libs are found), default to PMI-1, but users could select to try PMI-2. >>>>>> If the PMI-2 component failed, we would emit a show_help indicating that >>>>>> they probably have a broken PMI-2 version and should try PMI-1. >>>>>> >>>>>> Make sense? >>>>>> Ralph >>>>>> >>>>>> On May 7, 2014, at 8:00 AM, Ralph Castain <r...@open-mpi.org> wrote: >>>>>> >>>>>> >>>>>> On May 7, 2014, at 7:56 AM, Joshua Ladd <jladd.m...@gmail.com> wrote: >>>>>> >>>>>> Ah, I see. Sorry for the reactionary comment - but this feature falls >>>>>> squarely within my "jurisdiction", and we've invested a lot in improving >>>>>> OMPI jobstart under srun. >>>>>> >>>>>> That being said (now that I've taken some deep breaths and carefully >>>>>> read your original email :)), what you're proposing isn't a bad idea. I >>>>>> think it would be good to maybe add a "--with-pmi2" flag to configure >>>>>> since >>>>>> "--with-pmi" automagically uses PMI2 if it finds the header and lib. This >>>>>> way, we could experiment with PMI1/PMI2 without having to rebuild SLURM >>>>>> or >>>>>> hack the installation. >>>>>> >>>>>> >>>>>> That would be a much simpler solution than what Artem proposed >>>>>> (off-list) where we would try PMI2 and then if it didn't work try to >>>>>> figure >>>>>> out how to fall back to PMI1. I'll add this for now, and if Artem wants >>>>>> to >>>>>> try his more automagic solution and can make it work, then we can >>>>>> reconsider that option. >>>>>> >>>>>> Thanks >>>>>> Ralph >>>>>> >>>>>> >>>>>> Josh >>>>>> >>>>>> >>>>>> On Wed, May 7, 2014 at 10:45 AM, Ralph Castain <r...@open-mpi.org> >>>>>> wrote: >>>>>> >>>>>> Okay, then we'll just have to develop a workaround for all those >>>>>> Slurm releases where PMI-2 is borked :-( >>>>>> >>>>>> FWIW: I think people misunderstood my statement. I specifically did >>>>>> *not* propose to *lose* PMI-2 support. I suggested that we change it to >>>>>> "on-by-request" instead of the current "on-by-default" so we wouldn't >>>>>> keep >>>>>> getting asked about PMI-2 bugs in Slurm. Once the Slurm implementation >>>>>> stabilized, then we could reverse that policy. >>>>>> >>>>>> However, given that both you and Chris appear to prefer to keep it >>>>>> "on-by-default", we'll see if we can find a way to detect that PMI-2 is >>>>>> broken and then fall back to PMI-1. >>>>>> >>>>>> >>>>>> On May 7, 2014, at 7:39 AM, Joshua Ladd <jladd.m...@gmail.com> wrote: >>>>>> >>>>>> Just saw this thread, and I second Chris' observations: at scale we >>>>>> are seeing huge gains in jobstart performance with PMI2 over PMI1. We >>>>>> *CANNOT* loose this functionality. For competitive reasons, I >>>>>> cannot provide exact numbers, but let's say the difference is in the >>>>>> ballpark of a full order-of-magnitude on 20K ranks versus PMI1. PMI1 is >>>>>> completely unacceptable/unusable at scale. Certainly PMI2 still has >>>>>> scaling >>>>>> issues, but there is no contest between PMI1 and PMI2. We (MLNX) are >>>>>> actively working to resolve some of the scalability issues in PMI2. >>>>>> >>>>>> Josh >>>>>> >>>>>> Joshua S. Ladd >>>>>> Staff Engineer, HPC Software >>>>>> Mellanox Technologies >>>>>> >>>>>> Email: josh...@mellanox.com >>>>>> >>>>>> >>>>>> On Wed, May 7, 2014 at 4:00 AM, Ralph Castain <r...@open-mpi.org> >>>>>> wrote: >>>>>> >>>>>> Interesting - how many nodes were involved? As I said, the bad >>>>>> scaling becomes more evident at a fairly high node count. >>>>>> >>>>>> On May 7, 2014, at 12:07 AM, Christopher Samuel < >>>>>> sam...@unimelb.edu.au> wrote: >>>>>> >>>>>> > -----BEGIN PGP SIGNED MESSAGE----- >>>>>> > Hash: SHA1 >>>>>> > >>>>>> > Hiya Ralph, >>>>>> > >>>>>> > On 07/05/14 14:49, Ralph Castain wrote: >>>>>> > >>>>>> >> I should have looked closer to see the numbers you posted, Chris - >>>>>> >> those include time for MPI wireup. So what you are seeing is that >>>>>> >> mpirun is much more efficient at exchanging the MPI endpoint info >>>>>> >> than PMI. I suspect that PMI2 is not much better as the primary >>>>>> >> reason for the difference is that mpriun sends blobs, while PMI >>>>>> >> requires that everything b >>>>>> >>>>>> _______________________________________________ >>>>>> >>>>>> devel mailing list >>>>>> de...@open-mpi.org >>>>>> Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/devel >>>>>> Link to this post: >>>>>> http://www.open-mpi.org/community/lists/devel/2014/05/14716.php >>>>>> >>>>> >>>>> >>> >>> >>> -- >>> С Уважением, Поляков Артем Юрьевич >>> Best regards, Artem Y. Polyakov >>> _______________________________________________ >>> devel mailing list >>> de...@open-mpi.org >>> Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/devel >>> Link to this post: >>> http://www.open-mpi.org/community/lists/devel/2014/05/14725.php >>> >>> >>> >>> _______________________________________________ >>> devel mailing list >>> de...@open-mpi.org >>> Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/devel >>> Link to this post: >>> http://www.open-mpi.org/community/lists/devel/2014/05/14726.php >>> >> >> >> >> -- >> С Уважением, Поляков Артем Юрьевич >> Best regards, Artem Y. Polyakov >> > > > > -- > С Уважением, Поляков Артем Юрьевич > Best regards, Artem Y. Polyakov > _______________________________________________ > devel mailing list > de...@open-mpi.org > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/devel > Link to this post: > http://www.open-mpi.org/community/lists/devel/2014/05/14728.php > > > > _______________________________________________ > devel mailing list > de...@open-mpi.org > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/devel > Link to this post: > http://www.open-mpi.org/community/lists/devel/2014/05/14729.php > -- С Уважением, Поляков Артем Юрьевич Best regards, Artem Y. Polyakov
