Messages in this thread | | | Subject | Re: Suspicious error for CMA stress test | From | Vlastimil Babka <> | Date | Mon, 14 Mar 2016 13:30:09 +0100 |
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On 03/14/2016 08:18 AM, 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, so this is bloat-o-meter on x86_64, gcc 5.3.1. CONFIG_CMA=y
next-20160310 vs my patch (with added min_t as you pointed out): add/remove: 0/0 grow/shrink: 1/1 up/down: 69/-5 (64) function old new delta free_one_page 833 902 +69 free_pcppages_bulk 1333 1328 -5
next-20160310 vs your patch: add/remove: 0/0 grow/shrink: 2/0 up/down: 577/0 (577) function old new delta free_one_page 833 1187 +354 free_pcppages_bulk 1333 1556 +223
my patch vs your patch: add/remove: 0/0 grow/shrink: 2/0 up/down: 513/0 (513) function old new delta free_one_page 902 1187 +285 free_pcppages_bulk 1328 1556 +228
The increase of your version is surprising, wonder what the compiler did. Otherwise I would like simpler/maintainable version, but this is crazy. Can you post your results? I wonder if your compiler e.g. decided to stop inlining page_is_buddy() or something.
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