sure - might be faster that way :-) On May 1, 2014, at 6:59 AM, Jeff Squyres (jsquyres) <jsquy...@cisco.com> wrote:
> Want to have a phone call/webex to discuss? > > > On May 1, 2014, at 9:43 AM, Ralph Castain <r...@open-mpi.org> wrote: > >> The problem we'll have with BTLs in opal is going to revolve around that >> ompi_process_name_t and will occur in a number of places. I've been trying >> to grok George's statement about accessors and can't figure out a clean way >> to make that work IF every RTE gets to define the process name a different >> way. >> >> For example, suppose I define ompi_process_name_t to be a string. I can hash >> the string down to an opal_identifier_t, but that is a structureless 64-bit >> value - there is no concept of a jobid or vpid in it. So if you now want to >> extract a jobid for that identifier, the only way you can do it is to >> "up-call" back to the RTE to parse it. >> >> This means that every RTE would have to initialize OPAL with a registration >> of its opal_identifier parser function(s), which seems like a really ugly >> solution. >> >> Maybe it is time to shift the process identifier down to the opal layer? If >> we define opal_identifier_t to include the required jobid/vpid, perhaps >> adding a void* so someone can put whatever they want in it? >> >> Note that I'm not wild about extending the identifier size beyond 64-bits as >> the memory footprint issue is growing in concern, and I still haven't seen >> any real use-case proposed for extending it. >> >> >> On May 1, 2014, at 3:41 AM, Jeff Squyres (jsquyres) <jsquy...@cisco.com> >> wrote: >> >>> On Apr 30, 2014, at 10:01 PM, George Bosilca <bosi...@icl.utk.edu> wrote: >>> >>>> Why do you need the ompi_process_name_t? Isn’t the opal_identifier_t >>>> enough to dig for the info of the peer into the opal_db? >>> >>> >>> At the moment, I use the ompi_process_name_t for RML sends/receives in the >>> usnic BTL. I know this will have to change when the BTLs move down to OPAL >>> (when is that going to happen, BTW?). So my future use case may be >>> somewhat moot. >>> >>> More detail >>> =========== >>> >>> "Why does the usnic BTL use RML sends/receives?", you ask. >>> >>> The reason is rooted in the fact that the usnic BTL uses an unreliable, >>> connectionless transport under the covert. We had some customers have >>> network misconfigurations that resulted in usnic traffic not flowing >>> properly (e.g., MTU mismatches in the network). But since we don't have a >>> connection-oriented underlying API that will eventually timeout/fail to >>> connect/etc. when there's a problem with the network configuration, we >>> added a "connection validation" service in the usnic BTL that fires up in a >>> thread in the local rank 0 on each server. This thread provides service to >>> all the MPI processes on its server. >>> >>> In short: the service thread sends UDP pings and ACKs to peer service >>> threads on other servers (upon demand/upon first send between servers) to >>> verify network connectivity. If the pings eventually fail/timeout (i.e., >>> don't get ACKs back), the service thread does a show_help and kills the >>> job. >>> >>> There's more details, but that's the gist of it. >>> >>> This basically gives us the ability to highlight problems in the network >>> and kill the MPI job rather than spin infinitely while trying to deliver >>> MPI/BTL messages to a peer that will never get there. >>> >>> Since this is really a server-to-server network connectivity issue (vs. an >>> MPI peer-to-peer connectivity issue), we only need to have one service >>> thread for a whole server. The other MPI procs on the server use RML to >>> talk to it. E.g., "Please ping the server where MPI proc X lives," and so >>> on. This seemed better than having a service thread in each MPI process. >>> >>> We've thought a bit about what to do when the BTLs move down to OPAL (since >>> they won't be able to use RML any more), but don't have a final solution >>> yet... We do still want to be able to utilize this capability even after >>> the BTL move. >>> >>> -- >>> Jeff Squyres >>> jsquy...@cisco.com >>> For corporate legal information go to: >>> http://www.cisco.com/web/about/doing_business/legal/cri/ >>> >>> _______________________________________________ >>> 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/2014/05/14673.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/2014/05/14674.php > > > -- > Jeff Squyres > jsquy...@cisco.com > For corporate legal information go to: > http://www.cisco.com/web/about/doing_business/legal/cri/ > > _______________________________________________ > 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/2014/05/14675.php
