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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , , , , Wei Yang Subject: [PATCH V2 2/5] mm/khugepaged: count small VMAs towards scan limit Date: Wed, 24 Dec 2025 11:13:53 +0000 Message-ID: <20251224111351.41042-8-shivankg@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251224111351.41042-4-shivankg@amd.com> References: <20251224111351.41042-4-shivankg@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: satlexmb08.amd.com (10.181.42.217) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ1PEPF0000231B:EE_|SA1PR12MB999108:EE_ X-MS-Office365-Filtering-Correlation-Id: 0b86a8ce-eead-4834-9a4d-08de42de1990 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|82310400026|36860700013|7416014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?7KAYoRfGQGXZMhbORO4bon/xjjlC/x7oWMrIkP5IHUDryUo2ZHE/vZX5VvsG?= =?us-ascii?Q?xZrbUj8ncHajHfg/guohj6m9FZIMC+peUoiixebgtrH96AlhicUyWA2nl+JF?= =?us-ascii?Q?3AJ33zMo1ykKc9H/naEU3OPCIDtOQ/8RoLmbCBodrZ5Jp7uaS9rrXR3Wk8yP?= =?us-ascii?Q?Y8t66BAa1kDiM9aWEWoVJGRaXeUtU3tlySIfyYV/ZQ6jH8qV2w6skL6+dUU8?= =?us-ascii?Q?QrLKzJrYXMll/mpwtYCGqMK/GTpygbv2Jypd7IhFjcGbt9O5L3MthbDti7k7?= =?us-ascii?Q?zTyGSsVODdvl7yO7M1ZI0mgkYHOBpvsJW67hbjDs34m0eBW/ysCYGt+Nx7we?= =?us-ascii?Q?L6jceT2hNOS22yjgZD54ek2OBm1hA87Vy9BtV5eNQj7wWOcuEUxieQv39s15?= =?us-ascii?Q?Kr4KHyMPn49Ox0AZKsjgArrDptpMVaTPfIjd9TAFxGqd0YqU1EnrZrpBrZ+/?= =?us-ascii?Q?PZ7rd4R0mx+7cQ1q+W0zQD699vNjM0WcCdARfDFJSQCtt+bwBPw4LqhKRIt8?= =?us-ascii?Q?wdOeyYHjGqNGqsI1XEtuuW5+7eOEap5SUK0GWzb4fEUMa55gl3RO8PVCLLuL?= =?us-ascii?Q?Hwhzyix/AVl1eTpGtjz2BTxncviJU2LB69zBmwAw00Q6ckPlrAIr/k3UBg+w?= =?us-ascii?Q?esM011IL6j7AAIBQoe1XrQoMah7qaWpyFjx4h71Iyakhha1eSgMBVlnDqASK?= =?us-ascii?Q?a3r5kYP1dAc6Ed0J+7GVnKdKzuZD+Rc4yKY0wBtHNct/RxEyWyJ9FJCqC4Ga?= =?us-ascii?Q?AXAgIroaziaWCjXP0dBdOHO8Zkq1muhs8dcuCi+wHfRCEIptTyC1pKDVnQM1?= =?us-ascii?Q?aZEGOIqruMuGvXPGYxbM3YUj6ufBSfqSEzZ8MLlcinQrWV0obVsDdP+3/ZVz?= =?us-ascii?Q?D2O5uTsSJKMLITsAfQb/bVjAN48xCLpi9NrIUaOVlNJQ1LZ/p95N5qEzEVpj?= =?us-ascii?Q?TwLc/mKMkR/J0dFgz6qlIJi5FFlucyUNzhZ5fz46iwod/flNWmFekQSciPt0?= =?us-ascii?Q?nfcNddtnrEc/KbSU6PHmsqrTR48W9Z/XbGrR1XPFQSe0T3sk+aLHJxNG4kJj?= =?us-ascii?Q?yQGwVUF3wiB0mrRXQsTwuBPwG6mYt/ljW2lKMPCLz88Yd3xzYZfg4yQa6Sem?= =?us-ascii?Q?hQyOfCWnA58V0VaGzZjVER8PeVMdIsAZrwtej2E8BeIdsjh/RtnxAzNNUFAj?= =?us-ascii?Q?Xy8Yv8gCH64wG5cA5Hzgxa+Y/VXW+yv9JTM+FXp8EKrhiJQKwt/Dn7BaSAoi?= =?us-ascii?Q?g8s8KAzGeasGeU1TvJ1n357zq0a0k50myq9dCI1iABygyfdvplRSv4DolKzh?= =?us-ascii?Q?8J9PNDFg0xcCfkuDMbm9Bxm3DycIln5iAGCI/VjEsJFOy+B3UhdQ00I/hgJ0?= =?us-ascii?Q?GNQ2IpeJqLe882dz4Z2PifUsdb49dpGLxo7bUgMcQ+POYlRZ1iWOCB6RqpTU?= =?us-ascii?Q?MmXxbMe7ArDf52o9P56ORIpjwXBsgnunBonl5AhBDp4FMIt1ThS40EE4Is+m?= =?us-ascii?Q?yNOvTljY30n9p2AbDeJp8yR9v0GbCG5FOWo5ZobFdLkI713Skl8hzMOv8UJa?= =?us-ascii?Q?1DNXvPqCsKVGCMFaU8w=3D?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(1800799024)(376014)(82310400026)(36860700013)(7416014);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Dec 2025 11:18:01.1522 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 0b86a8ce-eead-4834-9a4d-08de42de1990 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SJ1PEPF0000231B.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB999108 Content-Type: text/plain; charset="utf-8" The khugepaged_scan_mm_slot() uses a 'progress' counter to limit the amount of work performed and consists of three components: 1. Transitioning to a new mm (+1). 2. Skipping an unsuitable VMA (+1). 3. Scanning a PMD-sized range (+HPAGE_PMD_NR). Consider a 1MB VMA sitting between two 2MB alignment boundaries: vma1 vma2 vma3 +----------+------+----------+ |2M |1M |2M | +----------+------+----------+ ^ ^ start end ^ hstart,hend In this case, for vma2: hstart =3D round_up(start, HPAGE_PMD_SIZE) -> Next 2MB alignment hend =3D round_down(end, HPAGE_PMD_SIZE) -> Prev 2MB alignment Currently, since `hend <=3D hstart`, VMAs that are too small or unaligned to contain a hugepage are skipped without incrementing 'progress'. A process containing a large number of such small VMAs will unfairly consume more CPU cycles before yielding compared to a process with fewer, larger, or aligned VMAs. Fix this by incrementing progress when the `hend <=3D hstart` condition is met. Additionally, change 'progress' type to `unsigned int` to match both the 'pages' type and the function return value. Suggested-by: Wei Yang Signed-off-by: Shivank Garg Reviewed-by: Lance Yang Reviewed-by: Wei Yang --- mm/khugepaged.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 107146f012b1..0b549c3250f9 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2403,7 +2403,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned = int pages, int *result, struct mm_slot *slot; struct mm_struct *mm; struct vm_area_struct *vma; - int progress =3D 0; + unsigned int progress =3D 0; =20 VM_BUG_ON(!pages); lockdep_assert_held(&khugepaged_mm_lock); @@ -2447,7 +2447,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned = int pages, int *result, } hstart =3D round_up(vma->vm_start, HPAGE_PMD_SIZE); hend =3D round_down(vma->vm_end, HPAGE_PMD_SIZE); - if (khugepaged_scan.address > hend) { + if (khugepaged_scan.address > hend || hend <=3D hstart) { progress++; continue; } --=20 2.43.0