From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f69.google.com (mail-pl0-f69.google.com [209.85.160.69]) by kanga.kvack.org (Postfix) with ESMTP id 0D6776B000E for ; Wed, 11 Apr 2018 03:23:40 -0400 (EDT) Received: by mail-pl0-f69.google.com with SMTP id 61-v6so680897plz.20 for ; Wed, 11 Apr 2018 00:23:40 -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 u29sor96010pgo.191.2018.04.11.00.23.37 for (Google Transport Security); Wed, 11 Apr 2018 00:23:37 -0700 (PDT) From: Jia He Subject: [PATCH v8 3/6] arm: arm64: page_alloc: reduce unnecessary binary search in memblock_next_valid_pfn() Date: Wed, 11 Apr 2018 00:21:54 -0700 Message-Id: <1523431317-30612-4-git-send-email-hejianet@gmail.com> In-Reply-To: <1523431317-30612-1-git-send-email-hejianet@gmail.com> References: <1523431317-30612-1-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. Furthermore, if the pfn is in a *gap* of two memory region, skip to next region directly if possible. Signed-off-by: Jia He --- include/linux/early_pfn.h | 37 +++++++++++++++++++++++++++++-------- 1 file changed, 29 insertions(+), 8 deletions(-) diff --git a/include/linux/early_pfn.h b/include/linux/early_pfn.h index 1b001c7..f9e40c3 100644 --- a/include/linux/early_pfn.h +++ b/include/linux/early_pfn.h @@ -3,31 +3,52 @@ #ifndef __EARLY_PFN_H #define __EARLY_PFN_H #ifdef CONFIG_HAVE_MEMBLOCK_PFN_VALID +static int early_region_idx __init_memblock = -1; 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, next_start_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; + + early_region_idx++; + next_start_pfn = PFN_DOWN(regions[early_region_idx].base); + + if (pfn >= end_pfn && pfn <= next_start_pfn) + return next_start_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_MEMBLOCK_PFN_VALID*/ -- 2.7.4