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charset=UTF-8 Date: Mon, 21 Sep 2026 22:07:54 -0400 Message-Id: Subject: Re: [PATCH v8 03/14] mm: introduce pgtable_has_pmd_leaves() Cc: , , , , , , , , , , , , , , , , , , , , To: "Luiz Capitulino" , , , , , From: "Zi Yan" X-Mailer: aerc 0.22.0 References: In-Reply-To: X-ClientProxiedBy: YQBPR0101CA0278.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:c01:68::12) To IA0PR12MB8374.namprd12.prod.outlook.com (2603:10b6:208:40e::7) 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: IA0PR12MB8374:EE_|DS4PR12MB9588:EE_ X-MS-Office365-Filtering-Correlation-Id: c1d25505-6c52-4a31-4843-08df184e51c4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|7416014|23010399003|366016|6133799003|10067099003|56012099006|11063799006|4143699003|18002099003|22082099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:IA0PR12MB8374.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(376014)(7416014)(23010399003)(366016)(6133799003)(10067099003)(56012099006)(11063799006)(4143699003)(18002099003)(22082099003);DIR:OUT;SFP:1101; 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This helper is used in fast > paths > > A better design would be to separate CONFIG_TRANSPARENT_HUGEPAGE > checking, which can be done with the IS_ENABLED() macro, from checking > if a CPU supports PMD-sized pages. > > To this end, this commit introduces a new helper called > pgtable_has_pmd_leaves() which offers the following advantages: > > 1. Well defined and clear semantics: it returns true if the CPU > supports PMD-sized pages and false otherwise > 2. It always returns a cached value, so it can be used in fast paths > 3. It's implemented with a static key: it's a no-op for archs not > implemeting it and for archs implementing it the static key is > changed only during boot > > The new helper requires an initialization step which is performed by > pgtable_leaf_support_init(). We call pgtable_leaf_support_init() early > during boot from mm_core_init(). > > The next commits will convert users of both has_transparent_hugepage() > and thp_disabled_by_hw() to pgtable_has_pmd_leaves() and/or > IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE). > > Signed-off-by: Luiz Capitulino > --- > include/linux/pgtable.h | 17 +++++++++++++++++ > mm/memory.c | 9 +++++++++ > mm/mm_init.c | 1 + > 3 files changed, 27 insertions(+) > LGTM. Acked-by: Zi Yan --=20 Best Regards, Yan, Zi