On Tue, 2009-03-31 at 11:00 -0400, Jeff Squyres wrote: > On Mar 31, 2009, at 3:45 AM, Sylvain Jeaugey wrote: > > System V shared memory used to be the main way to do shared memory on > > MPICH and from my (little) experience, this was truly painful : > > - Cleanup issues : does shmctl(IPC_RMID) solve _all_ cases ? (even > > kill > > -9 ?) > Indeed. The one saving grace here is that the cleanup issues > apparently can be solved on Linux with a special flag that indicates > "automatically remove this shmem when all processes attaching to it > have died." That was really the impetus for [re-]investigating sysv > shm. I, too, remember the sysv pain because we used it in LAM, too...
Unless there is something newer than IPC_RMID that I haven't heard of this is far from a complete solution, setting RMID causes it to be deleted when the attach count becomes zero so it handles the kill -9 case however it has the down side that once it's been set no further processes can attach to the memory so you have to leave a window during init during which any crash will leave the memory. I've always been of the opinion that mmaping shared files was a much more advanced solution. Ashley Pittman.
