From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f170.google.com (mail-io0-f170.google.com [209.85.223.170]) by kanga.kvack.org (Postfix) with ESMTP id 5E4606B0258 for ; Tue, 15 Sep 2015 06:29:01 -0400 (EDT) Received: by iofh134 with SMTP id h134so195760774iof.0 for ; Tue, 15 Sep 2015 03:29:01 -0700 (PDT) Received: from mga09.intel.com (mga09.intel.com. [134.134.136.24]) by mx.google.com with ESMTP id j20si4722054ioe.208.2015.09.15.03.28.59 for ; Tue, 15 Sep 2015 03:28:59 -0700 (PDT) From: "Kirill A. Shutemov" Subject: [PATCHv6 7/7] mm: use 'unsigned int' for compound_dtor/compound_order on 64BIT Date: Tue, 15 Sep 2015 13:28:15 +0300 Message-Id: <1442312895-124384-8-git-send-email-kirill.shutemov@linux.intel.com> In-Reply-To: <1442312895-124384-1-git-send-email-kirill.shutemov@linux.intel.com> References: <1442312895-124384-1-git-send-email-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Hugh Dickins Cc: Andrea Arcangeli , Dave Hansen , Vlastimil Babka , Johannes Weiner , Michal Hocko , David Rientjes , "Aneesh Kumar K.V" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Kirill A. Shutemov" 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 Acked-by: Michal Hocko Reviewed-by: Andrea Arcangeli --- 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 385604afbafa..82d7f6a72626 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 -- 2.5.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org