2016-03-18 0:43 GMT+09:00 Vlastimil Babka <vbabka@xxxxxxx>: > On 03/17/2016 10:24 AM, Hanjun Guo wrote: >> >> On 2016/3/17 14:54, Joonsoo Kim wrote: >>> >>> 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); >> >> >> I tested Vlastimil's patch + your change with stress for more than half >> hour, the bug >> I reported is gone :) > > > Oh, ok, will try to send proper patch, once I figure out what to write in > the changelog :) Thanks in advance! 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>