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Wed, 22 Apr 2020 14:38:46 +0000 Date: Wed, 22 Apr 2020 20:08:42 +0530 From: Prathu Baronia To: Will Deacon Cc: Vlastimil Babka , catalin.marinas@arm.com, alexander.duyck@gmail.com, chintan.pandya@oneplus.com, mhocko@suse.com, akpm@linux-foundation.org, linux-mm@kvack.org, gregkh@linuxfoundation.com, gthelen@google.com, jack@suse.cz, ken.lin@oneplus.com, gasine.xu@oneplus.com, ying.huang@intel.com, mark.rutland@arm.com Subject: Re: [PATCH v2] mm: Optimized hugepage zeroing & copying from user Message-ID: <20200422143841.ozuow4jkltzymvgs@oneplus.com> References: <20200419155856.dtwxomdkyujljdfi@oneplus.com> <87k12bt3ff.fsf@yhuang-dev.intel.com> <20200421093621.3fuptvf2qbyfzwfz@oneplus.com> <20200421100932.GC17256@willie-the-truck> <02d5daa8-ee7b-7d2d-6753-5191a7d761b9@suse.cz> <20200421133935.GC17875@willie-the-truck> <5e334947-22e9-e59d-f7bb-63e04cc8caf0@suse.cz> <20200422081852.GB29541@willie-the-truck> <20200422111928.GA32051@willie-the-truck> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200422111928.GA32051@willie-the-truck> User-Agent: NeoMutt/20171215 X-ClientProxiedBy: HK0PR01CA0055.apcprd01.prod.exchangelabs.com (2603:1096:203:a6::19) To HK0PR04MB3091.apcprd04.prod.outlook.com (2603:1096:203:89::20) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from oneplus.com (183.83.136.195) by HK0PR01CA0055.apcprd01.prod.exchangelabs.com (2603:1096:203:a6::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2937.13 via Frontend Transport; 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X-Microsoft-Antispam-Message-Info: XxXOCz1tmE5DSCoIftgcljIGYkDHUxFYu0zqXX+Xa0LOzpC2wscfr8dbacdhRGJGy9Zv4aWjSiep3hCjIL8jZLnephSnt92EUfG/2xpoYc9HSpzVTT/v6WL7ibSz5e2iEhjcf0Kf30keqmnNH6eY5qqRkVO810IJ19+oORjXfyTAubYxCezd9mXufw5oqLVuOIZ6p7eTCp78tQHYLI4WA1hNg2lPbntl/zzlhYj+BotpI6PY7FWXG+FsrtiPeyPf8KMh2gEY62QMxco6AZDqEImKyHhG5vBQIq5o/rTdXlAY2YU7YFhgQOLg9urpcay71FIMJObkCT8bilyNslieML05ACR35V2dmIBqim408Jdt/ipqyL2xgpWbFK2m/FvzbqE/HWV5J5/LtLoX8Ob4rFI3mIxmmDcShn9buDHt35wZ+vIiq1P4sITzs86PK0fi X-MS-Exchange-AntiSpam-MessageData: 8N/D79JwiuQYhxAv0orb7I78q9k3arGnIMJEsiU/YanTGOKoa0SNic3vhPOsE+C/w0yADzc1ARjrS5z6T/5pJJMm2igyNQ6hgbuqYvbmW1W3BxyVzbgWpfqbn+I832o29BtFceVlp4LAZyU5QASbDA== X-OriginatorOrg: oneplus.com X-MS-Exchange-CrossTenant-Network-Message-Id: ac59df0b-d098-4636-ea50-08d7e6cadd38 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Apr 2020 14:38:46.8629 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 0423909d-296c-463e-ab5c-e5853a518df8 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: Mx/8V0XZV32aYvjXsHl1Z2pPHjudwDsJzKNWMu9FeGfD3KAD4fwRcxN/qXH6TRHpxswPcbBZHnvsX+FhbyxIZcI9a8x5STr+QgF2B+5Unpg= X-MS-Exchange-Transport-CrossTenantHeadersStamped: HK0PR04MB2339 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: The 04/22/2020 12:19, Will Deacon wrote: > > I wrote the silly harness below for the snippets given in [1] but I can't > see any difference between the forwards and backwards versions on any arm64 > systems I have access to. > > Will > > --->8 > > #include > #include > #include > #include > #include > #include > > [...] > int main(void) > { > void *buf; > unsigned long long delta; > struct timespec ts_start, ts_end; > > if (posix_memalign(&buf, PAGE_SIZE, BUF_SZ)) { > perror("posix_memalign()"); > return -1; > } > > memset(buf, 0xd, BUF_SZ); > > [...] With this exact test code I also didn't observe any significant difference between forward and backwards versions on SM8150. ------------------------------------------------------------------------------ Output on 8150 under controlled conditions(CPU0 & 6 turned on, CPUs set to max frequency and DDR set to performance governor): ------------------------------------------------------------------------------ Forwards: took 0.319658 seconds Backwards: took 0.320983 seconds ------------------------------------------------------------------------------ But when I used malloc instead of posix_memalign because that was the big difference between this and our test code, I observed significant difference between forward and backwards version on SM8150. ------------------------------------------------------------------------------ Output on 8150 under controlled conditions(CPU0 & 6 turned on, CPUs set to max frequency and DDR set to performance governor): ------------------------------------------------------------------------------ Forwards: took 0.323157 seconds Backwards: took 0.581638 seconds ------------------------------------------------------------------------------ I don't know the implementation differences between posix_memalign and malloc which might lead to these results. -- Prathu Baronia OnePlus RnD