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On Mon, Aug 15, 2005 at 12:37:50PM -0400, Bill Jordan wrote: > On 8/11/05, Gleb Natapov <glebn@voltaire.com> wrote: > > What about the idea that was floating around about new VM flag that will > > instruct kernel to copy pages belonging to the vma on fork instead of mark > > them as cow? > > > > I think the big problem with this idea is the huge memory regions that > InfiniBand applications are dealing with. If the application forks (or > uses system()), you are going to copy a huge chunk of data (most > likely swapping since the application memory footprint is probably > already tuned to consume the available physical memory). And the copy > is really for nothing since in most (or at least many) cases the child > is just going to exec anyway. If the child is going to exec it may call vfork or clone with CLONE_VM flag. glibc system(3) does clone (CLONE_PARENT_SETTID | SIGCHLD) why not CLONE_VM too? This single change will allow to use system() from MPI programs thus eliminating many users problem. If the child isn't going to exec it should face the music. -- Gleb. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||
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