On Fri, Sep 11, 2009 at 03:11:36PM +0900, KOSAKI Motohiro wrote: > Hi > > Thank you explanation. > > > > > > Can I this version already solved fork() + COW issue? if so, could you > > > please explain what happen at fork. Obviously RDMA point to either parent > > > or child page, not both. but Corrent COW rule is, first touch process > > > get copyed page and other process still own original page. I think it's > > > unpecected behavior form RDMA. > > > > No, ummunotify doesn't really help that much with fork() + COW. If a > > parent forks and then touches pages that are actively in use for RDMA, > > then of course they get COWed and RDMA goes to the wrong memory (from > > the point of view of the parent). > > So, Can we assume OpenMPI user process doesn't such thing? > > Parhaps, madvise(DONTFORK) or vfork() avoid this issue. but I'm not > sure all program in the world do that. > MPI (or is it libibverbs?) marks all registered memory as DONTFORK.
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