Take a look in opal/mca/common/pmi - we already do a bunch of #if PMI2 stuff in there. All we are talking about doing here is:
* making those selections be runtime based on an MCA param, compiling if PMI2 is available but selected at runtime * moving some additional functions into that code area and out of the individual components On May 7, 2014, at 5:08 PM, Artem Polyakov <artpo...@gmail.com> wrote: > 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 > _______________________________________________ > 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/2014/05/14730.php
