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[73.69.118.222]) by smtp.gmail.com with ESMTPSA id x19-v6sm1420286ywg.72.2018.08.16.18.38.16 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 16 Aug 2018 18:38:18 -0700 (PDT) Subject: Re: [RESEND PATCH v10 6/6] mm: page_alloc: reduce unnecessary binary search in early_pfn_valid() To: Pasha Tatashin , Jia He , 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@microsoft.com, 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 References: <1530867675-9018-1-git-send-email-hejianet@gmail.com> <1530867675-9018-7-git-send-email-hejianet@gmail.com> From: Pavel Tatashin Message-ID: <831be9a1-6401-3af0-b68b-b3e25db806f9@gmail.com> Date: Thu, 16 Aug 2018 21:38:15 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/16/18 9:35 PM, Pasha Tatashin wrote: > > > On 7/6/18 5:01 AM, Jia He wrote: >> 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. in early_pfn_valid(), if pfn and >> pfn+1 are in the same memblock region, we can record the last returned >> memblock region index and check whether pfn++ is still in the same >> region. >> >> Currently it only improve the performance on arm/arm64 and will have no >> impact on other arches. >> >> For the performance improvement, after this set, I can see the time >> overhead of memmap_init() is reduced from 27956us to 13537us in my >> armv8a server(QDF2400 with 96G memory, pagesize 64k). > > This series would be a lot simpler if patches 4, 5, and 6 were dropped. > The extra complexity does not make sense to save 0.0001s/T during not. s/not/boot > > Patches 1-3, look OK, but without patches 4-5 __init_memblock should be > made local static as I suggested earlier. s/__init_memblock/early_region_idx