Messages in this thread Patch in this message | | | From | "Kirill A. Shutemov" <> | Subject | [PATCHv5 7/7] mm: use 'unsigned int' for compound_dtor/compound_order on 64BIT | Date | Thu, 3 Sep 2015 15:35:58 +0300 |
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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 difference can be bigger.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Michal Hocko <mhocko@suse.com> --- include/linux/mm_types.h | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index ecaf3b1d0216..39b0db74ba5e 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -150,8 +150,13 @@ struct page { /* First tail page of compound page */ struct { unsigned long compound_head; /* If bit zero is set */ +#ifdef CONFIG_64BIT + 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 -- 2.5.0
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