From 1965c8b7ac7dd147663faf77a66a693ac3ddcb85 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Fri, 6 Nov 2015 16:30:00 -0800 Subject: [PATCH] mm: use 'unsigned int' for compound_dtor/compound_order on 64BIT On 64 bit system we have enough space in struct page to encode compound_dtor and compound_order with unsigned int. On x86-64 it leads to slightly smaller code size due usesage of plain MOV instead of MOVZX (zero-extended move) or similar effect. allyesconfig: text data bss dec hex filename 159520446 48146736 72196096 279863278 10ae5fee vmlinux.pre 159520382 48146736 72196096 279863214 10ae5fae vmlinux.post On other architectures without native support of 16-bit data types the Signed-off-by: Kirill A. Shutemov Acked-by: Michal Hocko Reviewed-by: Andrea Arcangeli Cc: "Paul E. McKenney" Cc: Andi Kleen Cc: Aneesh Kumar K.V Cc: Christoph Lameter Cc: David Rientjes Cc: Hugh Dickins Cc: Joonsoo Kim Cc: Sergey Senozhatsky Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm_types.h | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index bb91658c603f..f8d1492a114f 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -143,8 +143,19 @@ struct page { unsigned long compound_head; /* If bit zero is set */ /* First tail page only */ +#ifdef CONFIG_64BIT + /* + * On 64 bit system we have enough space in struct page + * to encode compound_dtor and compound_order with + * unsigned int. It can help compiler generate better or + * smaller code on some archtectures. + */ + unsigned int compound_dtor; + unsigned int compound_order; +#else unsigned short int compound_dtor; unsigned short int compound_order; +#endif }; #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && USE_SPLIT_PMD_PTLOCKS -- 2.11.0