On Fri 21-08-15 13:40:59, Kirill A. Shutemov wrote: > On Fri, Aug 21, 2015 at 09:13:42AM +0200, Michal Hocko wrote: > > On Thu 20-08-15 16:26:04, Andrew Morton wrote: [...] > > > Why not use ushort for 64-bit as well? > > > > Yeah, I have asked the same in the previous round. So I've tried to > > compile with ushort. The resulting code was slightly larger > > text data bss dec hex filename > > 476370 90811 44632 611813 955e5 mm/built-in.o.prev > > 476418 90811 44632 611861 95615 mm/built-in.o.after > > > > E.g. prep_compound_page > > before: > > 4c6b: c7 47 68 01 00 00 00 movl $0x1,0x68(%rdi) > > 4c72: 89 77 6c mov %esi,0x6c(%rdi) > > after: > > 4c6c: 66 c7 47 68 01 00 movw $0x1,0x68(%rdi) > > 4c72: 66 89 77 6a mov %si,0x6a(%rdi) > > > > which looks very similar to me but I am not an expert here so it might > > possible that movw is slower. > > > > __free_pages_ok > > before: > > 63af: 8b 77 6c mov 0x6c(%rdi),%esi > > after: > > 63b1: 0f b7 77 6a movzwl 0x6a(%rdi),%esi > > > > which looks like a worse code to me. Whether this all is measurable or > > worth it I dunno. The ifdef is ugly but maybe the ugliness is a destiny > > for struct page. > > I don't care about the ifdef that much. If you guys prefer to drop it I'm > fine with that. I can live with it. It makes the struct more complicated which is what struck me. If there is a good reason and a better generated code is a good one then I do not object but please make it a separate patch so that we do not wonder why this has been done in the future. -- Michal Hocko SUSE Labs -- 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>