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Shutemov" , Dave Hansen , Peter Zijlstra , Thomas Gleixner References: <20250514104242.1275040-9-ardb+git@google.com> <20250514104242.1275040-10-ardb+git@google.com> <20250515131120.GCaCXn-E8zQutUqKLn@fat_crate.local> Content-Language: en-US From: Shivank Garg In-Reply-To: <20250515131120.GCaCXn-E8zQutUqKLn@fat_crate.local> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: PN3PR01CA0113.INDPRD01.PROD.OUTLOOK.COM (2603:1096:c01:96::18) To CH2PR12MB4262.namprd12.prod.outlook.com (2603:10b6:610:af::8) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH2PR12MB4262:EE_|DM6PR12MB4297:EE_ X-MS-Office365-Filtering-Correlation-Id: 3229f538-c56b-46d2-c593-08dd93dd29ae X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|366016|13003099007; X-Microsoft-Antispam-Message-Info: =?utf-8?B?bVJBNGJSbGIwN3RNYWU0WlFJYStpWUc4Wmpvb0I5cFA2WnZ4eWZNUTI3cWUx?= =?utf-8?B?em5zZUt2QjE2ZTVPZ3hDamhKY1dOUXlGejZtVnFnTjJyOGR4U3RaU2IwczRE?= =?utf-8?B?bmdmOEdDQWQyNUZWeXdDMzNCTDJsKzZnOU84ZWYwVnhZcHZsS2x6NGMzREdT?= =?utf-8?B?WFBSRUtUeGJtNFVuRmNzWlh6a2NYaGorem1JRWJUUGgzc2pWUnJINHhwZWlh?= =?utf-8?B?bGJmVkNnTS83YWt3L1hHZmt5OExuU2F6MFZUc1loeUVjVGdkeTBOR0hzOWQz?= =?utf-8?B?N0hsVGdCS2l1WHlUMS9MWjJSenRkbXZ3SWk2L0pSYk8yTWN2a3hmbWpVSXBR?= =?utf-8?B?UzFkUWZNL29sRGN2WmI2aGphYlVwRjJpamtDZzkyOXZHMlhmaTU1OVgxNTRZ?= =?utf-8?B?RVIxOVhzbWh0aWJDWGFKOTV2MHBwTmlhWTdCcjZGZEpETlFBRVd6Y2xlaUIx?= =?utf-8?B?QnBISEN5eVVPSklOL1hMbFIwMlR6cnp6MVBkTU5BWk8rUnUzNnFOajhmaVJF?= =?utf-8?B?WGdQNUkrWUk1Z1l5UWYyMXVXQnhRdVMwWm90amIrNk9lSFpKY2xNMTc5Smty?= =?utf-8?B?SHVHK0JHQ3VsUVN6Tk5VeGRrVEtIZmZpa3pDK2pwQzhVeHhubnptWWJxZkU4?= =?utf-8?B?VXZxbXNvMGJjMi80Z3oxT3pUSG8vYThJQnFOOFRMcHVVZHdqUnRCY3A3UFFq?= =?utf-8?B?RWRjZTVmbDBROFh1cWkxaTNkWU5CdGk1K1ZHLzVLa1lOV2d5eW9EbzBiajh5?= =?utf-8?B?QUFSYmVWb0hMSE1kQ2NiaE8yeUdFVExESFliQkZSWHRSUWJ3TjZDL1F2eTRa?= =?utf-8?B?KzRQMGxpUjlKN1QyVUNPVVN1VDBDQ2VKMmtISnp4OFlSWUtlajdBUzBaNUFx?= =?utf-8?B?NCtnVDlsNWpjUjg1Rm84ZXpnb1NheDdXMnA1bVA0cVdJMTNwNW1mODVKeXF4?= =?utf-8?B?bTdEekI4dHdlN2ZBTC8yWld4Z1Y0b1QwZUlqQ2tVQnJEbFBleTJFZ0FQVVZm?= =?utf-8?B?N3lQcHJFWnhDVzZOVnhxRmpwZno3Q1hVK3dLak9Pc1JZNi9uZTZ1aExiY3h0?= =?utf-8?B?SW93S3dGMnVhclZ2dTQ5TU9md1diTGIyTEpNN0xCOHhwUzJNT0ZrdjZ1ZWpq?= =?utf-8?B?T3FEYnF2T0NoMXUxdC9ob3BNVUMvU1N3VVdqL25ZWW1xQjFMbk9SdlVNZTQ0?= =?utf-8?B?aFhiVXZaV09xemtRYklUdzJiNkM1NWhkV3p0WklzWUVocFJqV2ZHZUtPZXR0?= =?utf-8?B?MXRCSStVOVlUcW5LczlCd0RURnB3OG50d3BIMjN2UWgyZ0J1MlRJQ1FHMG9r?= =?utf-8?B?Y3g5ZENyUnpVU0U4U1hHK2JWcDMzQmN4ZjkxYmRuK3BDUDRTNkcvOXp5OTYw?= =?utf-8?B?RnN6eFFSKyt2K29EalB0cFpiYTNobzVLQjJGdzA2YTdVaDBrVU5qaXMyWkY1?= =?utf-8?B?QUVxS1k2VmlVTmJqdm8yQ1JwUXlIV2lUN3F1QzlvY1Nwdnk3V1llOXJPdCtt?= =?utf-8?B?d2pUZGpTU0hQd2U1MXhJNjZESDBEUDlKejI1MzNnMTd5YjUwRUlwMjRzODdC?= =?utf-8?B?YmFvWmlQSUdzL2Faa0M4YktNdW5aaExNamx4YmVPemF0ckw3R0RUY3FjSENO?= =?utf-8?B?NHJGcHJQbHl4endsekVEYXhaaHYxSGl5Mlc0bHJMUldKSkZkaDhpekpRTXk1?= =?utf-8?B?V3V3Qjd0ckFvOEpFbjZOSkFwZDdoaEZPcS9hckZHNmErOVRUeE1jNE9YMXBR?= =?utf-8?B?MXdtTjNma1JISmZJNDFVb3ZKV1dRNWlyK2hmUGdYT1lwR25acUFKcVhzb2Vy?= =?utf-8?B?dW5WMG8zZjlhSThpV2hQY2Rwc3RWV3NNR2hsRmpHK0RadXdKQzNzRVdqbEg3?= =?utf-8?B?SVBHdy82MFh4TC9ocXU0ajE2aXNHd1hpNGRFUDhIdU45TklFYmxPR0pIa0JF?= =?utf-8?Q?yiPmxhZu9Nhze215AQobTUCr1av/kn4g?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CH2PR12MB4262.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(7416014)(376014)(366016)(13003099007);DIR:OUT;SFP:1101; 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>> - whether 5 level paging is currently in use. > > Btw, that gunk: > > We had started simplifying the whole 5-level crap: > > https://lore.kernel.org/all/20240621164406.256314-1-kirill.shutemov@linux.intel.com/ > > Shivank, I hear the performance issues got resolved in the meantime? > > Thx. > Hi Boris, I've re-tested the performance concerns we discussed earlier regarding 5-level paging. Recent tests on a current kernel don't show any performance issues: AMD EPYC Zen 5 (SMT enabled). Linux HEAD 6.15.0-rc6+ 088d13246a46 lmbench/lat_pagefault: numactl --membind=1 --cpunodebind=1 bin/x86_64-linux-gnu/lat_pagefault -N 100 1GB_randomfile Output values (50 runs, Mean, 2.5 percentile and 97.5 percentile, in microseconds): 4-level (no5lvl option) Mean: 0.138876 2.5% 97.5% 0.1384988 0.1392532 4-level (CONFIG_X86_5LEVEL=n) Mean: 0.137958 2.5% 97.5% 0.1376473 0.1382687 5-level Mean: 0.138904 2.5% 97.5% 0.1384789 0.1393291 After repeating the experiments a few times, the observed difference(~1%) in mean values is under noise levels. I think these results address the performance concerns previously raised[1]. I don't foresee any issues in proceeding with the 5-level paging implementation simplification efforts[2]. [1] https://lore.kernel.org/all/80734605-1926-4ac7-9c63-006fe3ea6b6a@amd.com [2] https://lore.kernel.org/all/20240621164406.256314-1-kirill.shutemov@linux.intel.com Thanks, Shivank