From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from CY3PR05CU001.outbound.protection.outlook.com (mail-westcentralusazon11013051.outbound.protection.outlook.com [40.93.201.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 40C0F2E4247 for ; Thu, 9 Apr 2026 20:10:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.93.201.51 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775765427; cv=fail; b=Br4ooL8H8vvCSY864VH6TCcurupQjyszRju4azrk1XNE+MknsJUA0W0mTLp/d3uLvhfXry4MGKYVHa6VbhpEE3i69h1B0vnXE1L72qeasWW1vrjlCbgjp9uZOfeaotjmWYVqQRlbNGA35NdDhT1eRnHbRvghce2uUdBjJfPAomc= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775765427; c=relaxed/simple; bh=n/77sEPOu+aHVcl/brKjffGob9z0HDFzLDe8fvIjtMM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: Content-Type:MIME-Version; b=fPZtIswVg7a4+DmDWKzJh35dM2unbDjo9WYYAM0OSY2Z5pPctgT4IikgvFKXhIEH7F0AcTSpGEQzRO2MCnbN8nARlfyPrK/z1rJ7F9BzGaXqwe0XAlCNRA6IOIrG3zYfM0LWxI/Xc+rN+TJfSWpHwsy1R6jGZIjt1q8PCaiGkB8= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com; spf=fail smtp.mailfrom=nvidia.com; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b=sYnqP4at; arc=fail smtp.client-ip=40.93.201.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nvidia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b="sYnqP4at" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=lM0p/cycgxTPj4WBLHo6+/yy1UDXjtw6oROHoxt067Xm1il2oAFCOfoMUMr2eutH3AFYGfDNbjUSZ0t0wv0dxT/A4mL71noT6Sq5SqJLmvoneg4hwt+yM2tT+dMLNoxuJ6oHDMmaoot+a2GILOOPl89/s0Jzsb3A+tQvEWetpF8x4uLasMWG03XcTMSqes7AhnpvcByz5aCkB6XPAAA6Su6c0aJeAJpVSzbD56Zf+KSztjIQk+c37BD/ea2y91l+tzBpWLtl2Co8U65rMPpTs9E2Tu4owI3L5n5xmLEohmazMzydT+xsnbVhhRuj0uZMbVG+OxF9RxAkuUwTDAJu5Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=TvYOlE6beCM0sBQ9h1R01NfbU4GGHKYjn7Rb5QwOHMo=; b=sEA6KW4hntwXVRDv/rc0uMwAXy+Q5n67RzT0u1NyYhoRnbypSm/Hd/65X0Scb6nW+XAcgX431slJ7exkmTeXt39cWgJSlcsjtk+zvJeoYDH1OVd0I5/PiLZgAb7TDxaHN1qWZ1NpEmgqh4jsZk31fZht3/qpTGDSg3s0zwUUzAN7MJHt2uEOFfgBJNs6Ry0Um852TuEoA3nfSo3LfDTBIzp7sA43etQm/Yur7JQV8JiEsNMT9MfFEToLnXyIDlzFW2SlkNRFyDTIzub79Y2wnYlX6j83praVGFkHXKRt3JBopr3gqnogsRBz4YsFXczGeKmNmWIFT1oh+EjGhecpNA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=TvYOlE6beCM0sBQ9h1R01NfbU4GGHKYjn7Rb5QwOHMo=; b=sYnqP4ataJwE+RLRrhvDTHfAdPW3T2Xc0mwruT2LTrPWl/llGYXhsB5pfvZgI1hXAbSRo/PrCVG/uVWSs+xQRFmyCIQb+ekRV9hc6Xas3gO7lNBXeMBIW/S+/2h4jt0/Nrb62EvqJRUmqpC/EYvgg1GP3cqWc3dJtjzQbK/h3B6frQjRgTB0FnPIWR9T3EaBNmsYxUrIDrfwnKeTpzq3frUWGsxdKJDZNKaDJEapcimyJYR0XiufGUkqIzxexbxZI3hOZZyyofQl7SWU69anGIDty5hkVMjD6aoi7dijubiBz70RWzcTDD8TD/it0qYTpPQl6oD78L8ncFKb8yO79w== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) by DM4PR12MB5962.namprd12.prod.outlook.com (2603:10b6:8:69::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9769.42; Thu, 9 Apr 2026 20:10:18 +0000 Received: from DS7PR12MB9473.namprd12.prod.outlook.com ([fe80::f01d:73d2:2dda:c7b2]) by DS7PR12MB9473.namprd12.prod.outlook.com ([fe80::f01d:73d2:2dda:c7b2%4]) with mapi id 15.20.9769.014; Thu, 9 Apr 2026 20:10:18 +0000 From: Zi Yan To: Luiz Capitulino Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, david@kernel.org, baolin.wang@linux.alibaba.com, ryan.roberts@arm.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com Subject: Re: [PATCH v3 09/10] mm: thp: always enable mTHP support Date: Thu, 09 Apr 2026 16:10:16 -0400 X-Mailer: MailMate (2.0r6290) Message-ID: <3B2D36D9-4B04-4548-ABA0-AE5DAF66B2EF@nvidia.com> In-Reply-To: <7830cda5-b3df-4da1-805b-278d5af6b2b1@redhat.com> References: <6dea717fe8c86003e7da33c9a7623b834649d5ee.1775679721.git.luizcap@redhat.com> <772C4431-FA93-4477-B1CE-3BE5EA97FD0B@nvidia.com> <7830cda5-b3df-4da1-805b-278d5af6b2b1@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: MN0PR02CA0004.namprd02.prod.outlook.com (2603:10b6:208:530::11) To DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) 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: DS7PR12MB9473:EE_|DM4PR12MB5962:EE_ X-MS-Office365-Filtering-Correlation-Id: 09e5dcc7-2962-4751-cd6f-08de9674053f X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|366016|1800799024|18002099003|22082099003|56012099003; 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:DS7PR12MB9473.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(376014)(366016)(1800799024)(18002099003)(22082099003)(56012099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?bHNROVVPV0dXMC9hcitRQTd3L1RIcXQ5dmNSS0tYR0s0SEJDbEVXQVNPSXlX?= =?utf-8?B?SG1CMndKajZMTElpdW9OQ1hoeXU4Q2szSnhZVjAwcjI5bHhDYTB2UWptS0ZN?= =?utf-8?B?ZksxK21yRktla2Vrbm9nZmxuNHVxZGcweWVFcjd5dUtHcG55dU1XdGJxUmU5?= =?utf-8?B?NW52YlQ2VzIxeEhlWXhQR2dSbysxYi9ub3dzdWZ5QllFZUtPdHAyWUo5VFNM?= =?utf-8?B?dUpVMVJTRkxYZzNmWEZQaHliYTI1QjNla0dER0VPMFRENDRUaHBJMklBRDlK?= =?utf-8?B?L016NmkwTGpFTi8reVo5Z2pkSk5oQmFBZGVBMmZXeEdROFRnaDlrVkhLVU14?= =?utf-8?B?QVBCVmgxWUJqRTdvaDJxZkdPQVZyWnFlbnZyYmFRRUc1UUowNERveVRLQWNM?= =?utf-8?B?cEx3ZEZkVHdaUWhsWlJESG5QRUVSRGtDaFlieWxYK3ViVUF4Y0MyT24renZl?= =?utf-8?B?UUZqdkNLUDIyWFZsL0ZEUkN4TzVZMFFFVEVoSTJ3Ukgwb1l3UXJuODdQVzky?= =?utf-8?B?RXAvdTJnNGh3L0NmN2NNMUM4Zzkvc3U5a29XKzFXSjdwK3FqN1ZXblVzTHRu?= =?utf-8?B?UTBqVTMvWThnc2s4T3NuUzc4STFqMTk3V0oxWUMyR2dIQ1doejVXSDNhWWpT?= =?utf-8?B?a09EbklvdTZXM21OaXVabThjZWYrZmVmRU83UFRmaFpZeXFDR05TNHEwaHpG?= =?utf-8?B?NGc5T2FmODlUcGU3eG9uTEMycmF6c2hxY0Z4MU4wSWQ2a3FQRW5GRWFLM3oz?= =?utf-8?B?Y0pXdkgyZnFrNldNaTZFcUVWZ1FYKy9YRFh1U21wc2R6amF1L2JvOTlCU2k4?= =?utf-8?B?S29lL0ZUd3E1L2xUam5iOEJyODBPUGtTOFhqWEdIdEcvZU0yQUQ3bnFPR0ta?= =?utf-8?B?WGU5b3VFbitKSHd1TVI2SjhyVjN1dWxITkFoTVBOUkZScTc1UEd5bkl3RlNs?= =?utf-8?B?WTZGYkRzMzBpelBoZ2NMVGJGTnZDdUVtMGlBUitEekJtTWFjVDdRMEZKQ210?= =?utf-8?B?bVlUcnE4dVRSWi95Y1Riazc1ampaS2c0QVJra3p1MWVCVWwrMm0xdHFYSi9n?= =?utf-8?B?VlFPcGtNeXZINUJwbS92OGgvQVRMMFQyWGpFc2JPeURPWWNmUUE0UUpSUWdK?= =?utf-8?B?c2ZONG9RT0UwOEQ4QXlKbWdSQUdRdDhYcDNxN3B6bHUrTzlsTWZJVXpXVFFQ?= =?utf-8?B?K3Nyd2x1SWJFVlFHMHpVQ24vb1ozNTZzeEcra1BXRlBWbEhBYmhUTFJJaFJj?= =?utf-8?B?T0ZFK0JoUlNoaDFNNDkzVHhTR1huZnhzekc5VmRSZkljNnh1YkNuQTg5ajEx?= =?utf-8?B?anFyYWI3MDB2Z2JWVVlVMjIyWWFaUEFlekdwZWErVXk0Yk4xQ2NmZkdaRlRh?= =?utf-8?B?Zy94cC8wMytaOTN3NmRPMCsyaGsxdnB1d1hJNWdrcmJMRE5OWEhWN1VqOENs?= =?utf-8?B?Z2V0U285UzVtWEpJdXVWWlZPZFEzVkdwVXZ0dVdKc2JJZ3ZnQm9NWnZzYlJP?= =?utf-8?B?NlY1cjg0UWxTd0lZZHNQbnZleFQ5WEtkZ3BvNEx1Y3FxdUhCOVNJYUxxc3l6?= =?utf-8?B?VVBudTMzUk1XenJiMXlCTUhrZ3k5dG9lSEp6VzlUTzZkYVVlcVRReC81ZnRQ?= =?utf-8?B?ZWl4MURqTk9VVnlSUVZURktnTmVNU3h4TzNTWWFGSTdoNFMzQXpxVGlZSjFh?= =?utf-8?B?OS94cnV3TEVVSkxMNW5IWXVVcU5rTzVlSVVVY2FkUE5uSWRScWhtNU9yMkxu?= =?utf-8?B?UWVoRTVrZ2J1eXUzNU1QcFZwS2Jmc3h1eFZneVY1L0I4WGcyU0hjOXVhZ001?= =?utf-8?B?MG9jalVXRjZtT1BJUHVET3c2eXBUSkNIR0NoVHVZS2x1d3J5OGxLZktZeEV5?= =?utf-8?B?akx6WTU4bTRJRkRNUW02a0dvZmcyRTNaNGpCSTV0Z0QyQ210Tzg2eGpnQ1FM?= =?utf-8?B?U0RsRTlqSEhkTlZkR2NQdHc1RmZLazd5UmJUb3NmOGdzclBYeWFTcW55aUVh?= =?utf-8?B?TFh6M1VhUTNidEF0dmptc1llUGdoR3o0TVpuTjlOU2xsQ28zTFZrejNYSEky?= =?utf-8?B?ejc3UDFUZjdUNWZjTDRrekh3VW52b3ZNZSs3dCsxOGJtM0RBWklYcStzZmly?= =?utf-8?B?SllJQmEzUlZrN3N2RzFLOGh1b3F0TmlOYlcreGxkSTJXeTQxQW0wMGVHbWtl?= =?utf-8?B?R0RxYjFMbVlLdHc5ZjI5OTdjOFRCT0xFMGExamltSFlQOGpHTEJ0cWlZTGhU?= =?utf-8?B?djV2UGJUd3ZXdWhOeHJld2ZYMGw2RFU1V2RwK2dvU1d0bUwvb2t5WGowbDNk?= =?utf-8?B?akNoMDdJTEYwUk90UGZsWDM0S1RUZVVWZGI3bWRabjR3eE9UdGhZdz09?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 09e5dcc7-2962-4751-cd6f-08de9674053f X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB9473.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Apr 2026 20:10:18.3230 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: T+2TkHKD0T2BZr9bRdxX1Uc++h6fe2VCGe38P7gQW8VoXedkzj7Za3N2Q4U9IIS3 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB5962 On 9 Apr 2026, at 16:07, Luiz Capitulino wrote: > On 2026-04-09 11:55, Zi Yan wrote: >> On 8 Apr 2026, at 16:23, Luiz Capitulino wrote: >> >>> If PMD-sized pages are not supported on an architecture (ie. the >>> arch implements arch_has_pmd_leaves() and it returns false) then the >>> current code disables all THP, including mTHP. >>> >>> This commit fixes this by allowing mTHP to be always enabled for all >>> archs. When PMD-sized pages are not supported, its sysfs entry won't be >>> created and their mapping will be disallowed at page-fault time. >>> >>> Similarly, this commit implements the following changes for shmem: >>> >>> - In shmem_allowable_huge_orders(): drop the pgtable_has_pmd_leaves() >>> check so that mTHP sizes are considered >>> - In shmem_alloc_and_add_folio(): don't consider PMD and PUD orders >>> when PMD-sized pages are not supported by the CPU >>> >>> Signed-off-by: Luiz Capitulino >>> --- >>> mm/huge_memory.c | 13 ++++++++----- >>> mm/shmem.c | 4 +++- >>> 2 files changed, 11 insertions(+), 6 deletions(-) >>> >>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>> index 86e489c0a150..6de3d8ebc35c 100644 >>> --- a/mm/huge_memory.c >>> +++ b/mm/huge_memory.c >>> @@ -118,6 +118,9 @@ unsigned long __thp_vma_allowable_orders(struct vm_= area_struct *vma, >>> else >>> supported_orders =3D THP_ORDERS_ALL_FILE_DEFAULT; >>> >>> + if (!pgtable_has_pmd_leaves()) >>> + supported_orders &=3D ~(BIT(PMD_ORDER) | BIT(PUD_ORDER)); >> >> Why is BIT(PUD_ORDER) also removed? I thought PMD THP support and PUD TH= P support >> are separate. Here the code implies PUD THP relies on PMD THP. Is that t= he case? > > This was a suggestion from David to an earlier version: > > https://lore.kernel.org/linux-mm/dac20466-adac-4e47-8f50-87f4774fd57b@ker= nel.org/ > > My understanding was that if an arch doesn't support PMD pages then it > probably doesn't support PUD pages either. Got it. Can you add a comment on =E2=80=9CNo PMD leaves -> No PUD leaves=E2= =80=9D for pgtable_has_pmd_leaves(), so that no one would ask the same question again? Thanks. Best Regards, Yan, Zi