Ralph Castain wrote:
There is at least one binary distribution that does build on one linux and allows to be installed on several others. That is the reason I bring up the above. The community can make a stance that that one distribution does not matter for this case or needs to handle it on its own. In the grand scheme of things it might not matter but I wanted to at least stand up and be heard.On May 4, 2010, at 3:45 AM, Terry Dontje wrote:Is a configure-time test good enough? For example, are all Linuxes the same in this regard. That is if you built OMPI on RH and it configured in the new SysV SM will those bits actually run on other Linux systems correctly? I think Jeff had hinted to this similarly when suggesting this may need to be a runtime test.I don't think we have ever enforced that requirement, nor am I sure the current code would meet it. We have a number of components that test for ability to build, but don't check again at run-time.Generally, the project has followed the philosophy of "build on the system you intend to run on".
--td
--td Samuel K. Gutierrez wrote:Hi All,New configure-time test added - thanks for the suggestion, Jeff. Update and give it a whirl.Ethan - could you please try again? This time, I'm hoping sysv support will be disabled ;-).Thanks! -- Samuel K. Gutierrez Los Alamos National Laboratory On May 3, 2010, at 9:18 AM, Samuel K. Gutierrez wrote:Hi Jeff, Sounds like a plan :-). Thanks! -- Samuel K. Gutierrez Los Alamos National Laboratory On May 3, 2010, at 9:12 AM, Jeff Squyres wrote:It might well be that you need a configure test to determine whether this behavior occurs or not. Heck, it may even need to be a run-time test! Hrm.Write a small C program that does something like the following (this is off the top of my head):fork a child child goes to sleep immediately sysv alloc a segment attach to it ipc rm it parent wakes up child child tries to attach to segmentIf that succeeds, then all is good. If not, then don't use this stuff.On May 3, 2010, at 10:55 AM, Samuel K. Gutierrez wrote:Hi all, Does anyone know of a relatively portable solution for querying agiven system for the shmctl behavior that I am relying on, or is thisgoing to be a nightmare? Because, if I am reading this thread correctly, the presence of shmget and Linux is not sufficient for determining an adequate level of sysv support. Thanks! -- Samuel K. Gutierrez Los Alamos National Laboratory On May 2, 2010, at 7:48 AM, N.M. Maclaren wrote:On May 2 2010, Ashley Pittman wrote:On 2 May 2010, at 04:03, Samuel K. Gutierrez wrote:As to performance there should be no difference in use between sys-V shared memory and file-backed shared memory, the instructions issued and the MMU flags for the page should both be the same so the performance should be identical.Not necessarily, and possibly not so even for far-future Linuces.On at least one system I used, the poxious kernel wrote the completefile to disk before returning - all right, it did that for System V shared memory, too, just to a 'hidden' file! But, if I recall, onanother it did that only for file-backed shared memory - however, it'sa decade ago now and I may be misremembering. Of course, that's a serious issue mainly for large segments. I was using multi-GB ones. I don't know how big the ones you need are.The one area you do need to keep an eye on for performance is on numa machines where it's important which process on a node touches each page first, you can end up using different areas (pages, notregions) for communicating in different directions between the samepair of processes. I don't believe this is any different to mmap backed shared memory though.On some systems it may be, but in bizarre, inconsistent, undocumentedand unpredictable ways :-( Also, there are usually several system (and sometimes user) configuration options that change the behaviour, so youhave to allow for that. My experience of trying to use those is thatdifferent uses have incompatible requirements, and most of the critical configuration parameters apply to ALL uses!In my view, the configuration variability is the number one nightmare for trying to write portable code that uses any form of shared memory.ARMCI seem to agree.Because of this, sysv support may be limited to Linux systems - that is,until we can get a better sense of which systems provide the shmctlIPC_RMID behavior that I am relying on.And, I suggest, whether they have an evil gotcha on one of the areasthat Ashley Pittman noted. Regards, Nick Maclaren. _______________________________________________ devel mailing list de...@open-mpi.org http://www.open-mpi.org/mailman/listinfo.cgi/devel_______________________________________________ devel mailing list de...@open-mpi.org http://www.open-mpi.org/mailman/listinfo.cgi/devel-- 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 http://www.open-mpi.org/mailman/listinfo.cgi/devel_______________________________________________ devel mailing list de...@open-mpi.org http://www.open-mpi.org/mailman/listinfo.cgi/devel_______________________________________________ devel mailing list de...@open-mpi.org http://www.open-mpi.org/mailman/listinfo.cgi/devel-- <Mail Attachment.gif> Terry D. Dontje | Principal Software Engineer Developer Tools Engineering | +1.650.633.7054 Oracle * - Performance Technologies* 95 Network Drive, Burlington, MA 01803 Email terry.don...@oracle.com <mailto:terry.don...@oracle.com> _______________________________________________ devel mailing list de...@open-mpi.org <mailto:de...@open-mpi.org> http://www.open-mpi.org/mailman/listinfo.cgi/devel------------------------------------------------------------------------ _______________________________________________ devel mailing list de...@open-mpi.org http://www.open-mpi.org/mailman/listinfo.cgi/devel
-- Oracle Terry D. Dontje | Principal Software Engineer Developer Tools Engineering | +1.650.633.7054 Oracle * - Performance Technologies* 95 Network Drive, Burlington, MA 01803 Email terry.don...@oracle.com <mailto:terry.don...@oracle.com>
