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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , , , , Wei Yang Subject: [PATCH V3 2/5] mm/khugepaged: count small VMAs towards scan limit Date: Sun, 18 Jan 2026 19:22:55 +0000 Message-ID: <20260118192253.9263-8-shivankg@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260118192253.9263-4-shivankg@amd.com> References: <20260118192253.9263-4-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: satlexmb07.amd.com (10.181.42.216) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ5PEPF000001F1:EE_|IA1PR12MB8264:EE_ X-MS-Office365-Filtering-Correlation-Id: f1b92ba7-342f-46b4-4723-08de56c78e19 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|7416014|376014|1800799024|82310400026|13003099007; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?1sZC4w6QGfhrz0qgbK/qtFpU2HNnS4hWPyNNsz7OJt4/w9nXnotsok081eOm?= =?us-ascii?Q?b4GWYYMy1xxXuyuORkA4m6x5yRK5R42Yqs7wRjNYSwlQfJLhExqREz47/gcw?= =?us-ascii?Q?9gKb1oUvtTrBHMkpTr170lqUMsru1o+cTjUr0gC1IBFxxzu/+QyvlzT7HZnT?= =?us-ascii?Q?ypETWVV2H5UXPH1G0tPpWNqTvrwBNGoB50UmzyOt293IiJedUMOvcjJidDxO?= =?us-ascii?Q?4MwZwovVGviQjnf/0WeiOKagkVo0qtGVBj7CB5PTiXtrYY29/xDdccEClQ6j?= =?us-ascii?Q?jSROBSBBobekYJKUvyVqY9XuwgjIGBetCKSjYL7nXBCIN5xOtizwRc992z1a?= =?us-ascii?Q?5b+VprTMs5LU8CVpJSdBfa+mxFrmnEIIQlMwYA47ULNBmEZA86y0z8jCkjhF?= =?us-ascii?Q?+IbXN9baakExlmPRwcYxhS8OJQAaRymsTK559wlzAt4lBwZGG/8yeC0jfIlD?= =?us-ascii?Q?Ec0o3iGe99ysAXZAAn4Ij9FL3vU81TpZ7wPfE5nD2HdpPSAQRSGtMN4OqpUU?= =?us-ascii?Q?wkCJkXaI9g77wUdvTj8rr9r5Ko2fmL7/qtdITgQjqMpqAPFjYZBf5nMMBW4/?= =?us-ascii?Q?cc75cyfNAAbIH0L3RtUGny4QzuHD4isiOGa6Ds0Ie06fWEo8ekulZRxK574E?= =?us-ascii?Q?eMfmSVyuMF3ihRwCFqgRsc4pj7tmQQLf9rloXTnromZ89pMZR/RLjWmCkymS?= =?us-ascii?Q?1sYdKpgeyrm55uLzRfzJlbhbOnAFdcYViPHM8X1v1t5NPSacISqGWT5X7xYB?= =?us-ascii?Q?ZLQCFXCQ1adVj1wVfx6yK/sVP5nMYkYHnrzLp7+jc9eYLs7ZgS8Y81Ldxlem?= =?us-ascii?Q?6Ve1P8aimjwYKyPZKHrjEb+IAxV/T1YmVaawNrCwBPZMMUGfE/MfYIM4AD3s?= =?us-ascii?Q?0GLedBtf9wbG2yUGpM3P1i87t5Ieob8l+j7WvrG0RfwOjOilQR2Xm1YDaHIh?= =?us-ascii?Q?uKPv3wZ3IUaLfN+gI1oDJLxsF2m1/Im5FoOmb5h02GFGy8SgzwkBZVqXQxvy?= =?us-ascii?Q?vo+r0NlxZf7hc1hrg/Sq8nLSQ98cG9SoYLzFXlmn9y9YI+lfFIITuEjAtdVy?= =?us-ascii?Q?+nE6jDUGsBaXinW+XyR6IrwGhU8nAPrBa9OchdrUwwjJDk6IeZ0cdh8pREHp?= =?us-ascii?Q?s9tINHQPN+732YVN0FOnc7cMU+LnAVnrNP5yqmRv/BjEoNgoMV/LZkx+BS/N?= =?us-ascii?Q?kMi5WwuoOWomDr/7rrFmCNckR50rz+F0m99cGETdbOfuFU7rAnLsJ6Jc1Drh?= =?us-ascii?Q?h26duLtberb/Y3gPA9XOPCujDHnyn1AT4u026WIeuWTbjOQzugE0w0Z0QLRm?= =?us-ascii?Q?98KNWjvRd/4b/AKBUKKmQRfOlhb87e1RZhJK6WWNhANKormTwZGctT3EvnfQ?= =?us-ascii?Q?lI6I2Q/0Ttw7L9pLJs7qacyzctXVb/XGvINkcmUU2IgihhVrKDcrPaNva9KD?= =?us-ascii?Q?laxV//15wyu6K0EPKFgHvCGzZw5cx1LqcsMegES5gwLcX21VVkOB6zW3WGMq?= =?us-ascii?Q?q09K+7G7xuUM1uzENE7ee1UrYtgFgo3Vcfg9ziVHpt/5OSbwKP3EZdUN2Lgl?= =?us-ascii?Q?aCUX5XiarETNauQ32+RClpri0OclSv7KoNffDQaR0LjFN/sNRcRNkWC/W7cm?= =?us-ascii?Q?L6EuqB9fC4yuOeOUrXRmPTK4mGLjBKKKYeg+lQTCAhdxry7nd/jaqrnRv9wg?= =?us-ascii?Q?xNgrgw=3D=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)(36860700013)(7416014)(376014)(1800799024)(82310400026)(13003099007);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Jan 2026 19:27:01.4358 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f1b92ba7-342f-46b4-4723-08de56c78e19 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: SJ5PEPF000001F1.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB8264 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 Reviewed-by: Wei Yang Reviewed-by: Lance Yang Signed-off-by: Shivank Garg --- Incorporate comment feedback from Lance: https://lore.kernel.org/linux-mm/6b408736-978a-4d40-adfc-97819951c3a6@linux= .dev mm/khugepaged.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 984294a16861..93ce39915f4a 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 +2447,8 @@ 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) { + /* VMA already scanned or too small/unaligned for hugepage. */ progress++; continue; } --=20 2.43.0