http://doodle.com/hhm4yyr76ipcxgk2
On May 1, 2014, at 10:25 AM, Ralph Castain <r...@open-mpi.org> wrote: > 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 > > _______________________________________________ > 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/2014/05/14676.php -- Jeff Squyres jsquy...@cisco.com For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
