On Wed, Jul 30, 2008 at 09:19:44AM -0500, Christoph Lameter wrote: > Yes we have had so much talk about this that I am a bit tired of > talking about it. I vaguely remember bringing up the same point a > couple of months ago. If you can make it work then great. I think the current implementation is fine for the long run, it can provide the fastest performance when armed, and each invalidate either requires IPIs or it may may need to access the southbridge, so when freeing large areas of memory it's good being able to do a single invalidate. If I can add another comment, I think if a new user of mm_take_all_locks showup, that will further confirm that such method is useful and should stay. Of course it needs to be a legitimate usage that allows to improve performance to the fast paths like in the mmu-notifier usage. And if Nick's right that mm_take_all_locks will ever become a limitation, removing it is trivial, much much simpler than undoing mmu-notifier changes to tlb-gather. So until Nick will go ahead and remove the anon_vma->lock (and I don't think it's feasible without screwing other paths much more troublesome than mm_take_all_locks) I think this is fine to stay. If you'll have troubles removing anon_vma->lock it won't be because of mm_take_all_locks be sure ;). If you ever get there we'll add invalidate_page before tlb_remove_page and be done with it for the benefit of the VM, no problem at all. If we'll ever need to add scheduling capability to mmu notifiers (like for XPMEM or perhaps in the future infiniband) that's nearly trivially feasible too in the future without having to alter the API at all (something not feasible with other implementations). Nevertheless I'm ok if we want to alter the implementation in the future for whatever good/wrong reasaon: the only important thing to me is that from now on all kernels will have this functionality one way or another because KVM already depends on it and it swaps much better now! The current implementation is bugfree, well tested, looks great to me and there's no urgency to alter it. It's surely what all the mmu-notifier users prefer, and I want to thank everyone for the help in getting here and all the good/bad feedback provided that helped improving the code so much. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
