On Wed, Mar 16, 2016 at 05:44:28PM +0800, Hanjun Guo wrote: > On 2016/3/14 15:18, Joonsoo Kim wrote: > > On Mon, Mar 14, 2016 at 08:06:16AM +0100, Vlastimil Babka wrote: > >> On 03/14/2016 07:49 AM, Joonsoo Kim wrote: > >>> On Fri, Mar 11, 2016 at 06:07:40PM +0100, Vlastimil Babka wrote: > >>>> On 03/11/2016 04:00 PM, Joonsoo Kim wrote: > >>>> > >>>> How about something like this? Just and idea, probably buggy (off-by-one etc.). > >>>> Should keep away cost from <pageblock_order iterations at the expense of the > >>>> relatively fewer >pageblock_order iterations. > >>> Hmm... I tested this and found that it's code size is a little bit > >>> larger than mine. I'm not sure why this happens exactly but I guess it would be > >>> related to compiler optimization. In this case, I'm in favor of my > >>> implementation because it looks like well abstraction. It adds one > >>> unlikely branch to the merge loop but compiler would optimize it to > >>> check it once. > >> I would be surprised if compiler optimized that to check it once, as > >> order increases with each loop iteration. But maybe it's smart > >> enough to do something like I did by hand? Guess I'll check the > >> disassembly. > > Okay. I used following slightly optimized version and I need to > > add 'max_order = min_t(unsigned int, MAX_ORDER, pageblock_order + 1)' > > to yours. Please consider it, too. > > Hmm, this one is not work, I still can see the bug is there after applying > this patch, did I miss something? I may find that there is a bug which was introduced by me some time ago. Could you test following change in __free_one_page() on top of Vlastimil's patch? -page_idx = pfn & ((1 << max_order) - 1); +page_idx = pfn & ((1 << MAX_ORDER) - 1); Thanks. -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>