On Mon, Nov 7, 2011 at 11:32 PM, Andrea Arcangeli <aarcange@xxxxxxxxxx> wrote: > On Mon, Nov 07, 2011 at 12:21:35PM +0800, Nai Xia wrote: >> If an anonymous vma has not yet been faulted, move_page_tables() in move_vma() >> is not necessary for it. > > I actually thought of adding that (in fact fork has it and it's more > likely to be beneficial for fork than for mremap I suspect), but this > adds a branch to the fast path for a case that shouldn't normally > materialize. So I don't think it's worth adding it as I expect it to > add overhead in average. > Well, it seems like I forgot to embrace it with unlikely(), with instr prefetching this line seems a trivial even for the average cases. But in case it really materializes, it may avoid tedious page table locking and pmd allocation and furthermore, a semantically confusing operation of move_page_tables() on a same VMA. Anyway, it's not a big deal, indeed. You are the maintainers, it's left for you to decide. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>