On Thursday 08 May 2008 10:38, Robin Holt wrote: > On Wed, May 07, 2008 at 02:36:57PM -0700, Linus Torvalds wrote: > > On Wed, 7 May 2008, Andrea Arcangeli wrote: > > > I think the spinlock->rwsem conversion is ok under config option, as > > > you can see I complained myself to various of those patches and I'll > > > take care they're in a mergeable state the moment I submit them. What > > > XPMEM requires are different semantics for the methods, and we never > > > had to do any blocking I/O during vmtruncate before, now we have to. > > > > I really suspect we don't really have to, and that it would be better to > > just fix the code that does that. > > That fix is going to be fairly difficult. I will argue impossible. > > First, a little background. SGI allows one large numa-link connected > machine to be broken into seperate single-system images which we call > partitions. > > XPMEM allows, at its most extreme, one process on one partition to > grant access to a portion of its virtual address range to processes on > another partition. Those processes can then fault pages and directly > share the memory. > > In order to invalidate the remote page table entries, we need to message > (uses XPC) to the remote side. The remote side needs to acquire the > importing process's mmap_sem and call zap_page_range(). Between the > messaging and the acquiring a sleeping lock, I would argue this will > require sleeping locks in the path prior to the mmu_notifier invalidate_* > callouts().
Why do you need to take mmap_sem in order to shoot down pagetables of the process? It would be nice if this can just be done without sleeping. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
