On Thu 24-01-19 14:13:41, Wei Yang wrote: > On Wed, Jan 23, 2019 at 10:55:03AM +0100, Michal Hocko wrote: > >On Tue 22-01-19 15:56:28, Wei Yang wrote: > >> > >> I think the answer is yes. > >> > >> * it reduce the code from 6 lines to 3 lines, 50% off > >> * by reducing calculation back and forth, it would be easier for > >> audience to catch what it tries to do > > > >To be honest, I really do not see this sufficient to justify touching > >the code unless the resulting _generated_ code is better/more efficient. > > Tried objdump to compare two version. > > Base Patched Reduced > Code Size(B) 48 39 18.7% > Instructions 12 10 16.6% How have you compiled the code? (compiler version, any specific configs). Because I do not see any difference. CONFIG_CC_OPTIMIZE_FOR_SIZE: text data bss dec hex filename 47087 2085 72 49244 c05c mm/page_alloc.o 47087 2085 72 49244 c05c mm/page_alloc.o.prev CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE: text data bss dec hex filename 55046 2085 72 57203 df73 mm/page_alloc.o 55046 2085 72 57203 df73 mm/page_alloc.o.prev And that would actually match my expectations because I am pretty sure the compiler can figure out what to do with those operations even without any help. Really, is this really worth touching and spending a non-trivial time to discuss? I do not see the benefit. -- Michal Hocko SUSE Labs
