On Thu, Apr 08, 2010 at 07:56:04PM +0200, Johannes Weiner wrote: > Humm, maybe the start pfn could be huge page aligned? That would make > it possible to check for PageTransHuge() and skip over compound_order() > pages. This way, we should never actually run into PG_tail pages. The problem here are random compound pages that aren't owned by the transparent hugepage subsystem. If we can't identify those, it's unsafe to call compound_order (like it's unsafe to call page_order for pagebuddy pages). I don't see a way to solve this without a new PG_ bitflag. We could do a 64-bit only optimization though... ;) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>