From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f71.google.com (mail-pl0-f71.google.com [209.85.160.71]) by kanga.kvack.org (Postfix) with ESMTP id ECC856B0007 for ; Tue, 3 Apr 2018 22:57:09 -0400 (EDT) Received: by mail-pl0-f71.google.com with SMTP id 61-v6so9047678plz.20 for ; Tue, 03 Apr 2018 19:57:09 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id q3sor928392pgr.339.2018.04.03.19.57.08 for (Google Transport Security); Tue, 03 Apr 2018 19:57:08 -0700 (PDT) From: Jia He Subject: [PATCH v6 2/5] arm: arm64: page_alloc: reduce unnecessary binary search in memblock_next_valid_pfn() Date: Tue, 3 Apr 2018 19:56:16 -0700 Message-Id: <1522810579-7466-3-git-send-email-hejianet@gmail.com> In-Reply-To: <1522810579-7466-1-git-send-email-hejianet@gmail.com> References: <1522810579-7466-1-git-send-email-hejianet@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Russell King , Catalin Marinas , Will Deacon , Mark Rutland , Ard Biesheuvel , Andrew Morton , Michal Hocko Cc: Wei Yang , Kees Cook , Laura Abbott , Vladimir Murzin , Philip Derrin , AKASHI Takahiro , James Morse , Steve Capper , Pavel Tatashin , Gioh Kim , Vlastimil Babka , Mel Gorman , Johannes Weiner , Kemi Wang , Petr Tesarik , YASUAKI ISHIMATSU , Andrey Ryabinin , Nikolay Borisov , Daniel Jordan , Daniel Vacek , Eugeniu Rosca , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Jia He , Jia He Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns where possible") optimized the loop in memmap_init_zone(). But there is still some room for improvement. E.g. if pfn and pfn+1 are in the same memblock region, we can simply pfn++ instead of doing the binary search in memblock_next_valid_pfn. Signed-off-by: Jia He --- include/linux/arm96_common.h | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-) diff --git a/include/linux/arm96_common.h b/include/linux/arm96_common.h index a6f68ea..2f4dea4 100644 --- a/include/linux/arm96_common.h +++ b/include/linux/arm96_common.h @@ -5,32 +5,47 @@ #ifndef __ARM96_COMMON_H #define __ARM96_COMMON_H #ifdef CONFIG_HAVE_ARCH_PFN_VALID +static int early_region_idx __init_memblock = -1; /* HAVE_MEMBLOCK is always enabled on arm and arm64 */ ulong __init_memblock memblock_next_valid_pfn(ulong pfn) { struct memblock_type *type = &memblock.memory; - unsigned int right = type->cnt; - unsigned int mid, left = 0; + struct memblock_region *regions = type->regions; + uint right = type->cnt; + uint mid, left = 0; + ulong start_pfn, end_pfn; phys_addr_t addr = PFN_PHYS(++pfn); + /* fast path, return pfn+1 if next pfn is in the same region */ + if (early_region_idx != -1) { + start_pfn = PFN_DOWN(regions[early_region_idx].base); + end_pfn = PFN_DOWN(regions[early_region_idx].base + + regions[early_region_idx].size); + + if (pfn >= start_pfn && pfn < end_pfn) + return pfn; + } + + /* slow path, do the binary searching */ do { mid = (right + left) / 2; - if (addr < type->regions[mid].base) + if (addr < regions[mid].base) right = mid; - else if (addr >= (type->regions[mid].base + - type->regions[mid].size)) + else if (addr >= (regions[mid].base + regions[mid].size)) left = mid + 1; else { - /* addr is within the region, so pfn is valid */ + early_region_idx = mid; return pfn; } } while (left < right); if (right == type->cnt) return -1UL; - else - return PHYS_PFN(type->regions[right].base); + + early_region_idx = right; + + return PHYS_PFN(regions[early_region_idx].base); } EXPORT_SYMBOL(memblock_next_valid_pfn); #endif /*CONFIG_HAVE_ARCH_PFN_VALID*/ -- 2.7.4