From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6A184D3EE62 for ; Thu, 22 Jan 2026 13:06:19 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.1210986.1522548 (Exim 4.92) (envelope-from ) id 1viuNu-0006Vm-Tg; Thu, 22 Jan 2026 13:06:02 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 1210986.1522548; Thu, 22 Jan 2026 13:06:02 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1viuNu-0006Vf-Po; Thu, 22 Jan 2026 13:06:02 +0000 Received: by outflank-mailman (input) for mailman id 1210986; Thu, 22 Jan 2026 13:06:02 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1viuNt-0006VZ-VR for xen-devel@lists.xenproject.org; Thu, 22 Jan 2026 13:06:01 +0000 Received: from CH1PR05CU001.outbound.protection.outlook.com (mail-northcentralusazlp170100001.outbound.protection.outlook.com [2a01:111:f403:c105::1]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 1911a418-f793-11f0-b15e-2bf370ae4941; Thu, 22 Jan 2026 14:06:01 +0100 (CET) Received: from CH7PR03MB7860.namprd03.prod.outlook.com (2603:10b6:610:24e::14) by SN7PR03MB7153.namprd03.prod.outlook.com (2603:10b6:806:353::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9542.10; Thu, 22 Jan 2026 13:05:57 +0000 Received: from CH7PR03MB7860.namprd03.prod.outlook.com ([fe80::f5ba:35df:1c9f:b343]) by CH7PR03MB7860.namprd03.prod.outlook.com ([fe80::f5ba:35df:1c9f:b343%4]) with mapi id 15.20.9542.008; Thu, 22 Jan 2026 13:05:57 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 1911a418-f793-11f0-b15e-2bf370ae4941 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=W1yjiRSuntZluOvc7P/qmBiZ+81oueGiPtprw7Klxj6hd2u8wqjEPmQZFS/5V5CslMHul8DsNciCsg9M7bn4Yhg9dOvmq322v/Yz5BuFQPXep/PdYq/qV0k+1oV9oo77+RfNZtecfWQGIadn2drGlqBdBr8xiK/5o7X5yv+aPamg8Q7CK/qXYMlTco/5dFiqr7Ey0aH7kbvxMUbZhexEGNFPlUv4p2H0GEZ2ShsNURl7CvFunlZGcPjXens3UV4HHkdsprFcuXOzd/Y7DrHoYEmFwEDtUfilp8XYXZlaf3LEFO5VRJcVdhvCxFk5+GSjFl9+309SpG91+gUwnyWkQw== 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=cFD/qT4OVfg9dr7c4d4vbfsAInr6LCgB7utzTN1z3rc=; b=j8dPL6WDDxOUyC3qBx31qTQEplk4paKwxSHyMuULiMJupviFNDwpslqdw/alFKXbmZzN8aqnitTV41S7p2bMklU0zl3n5DeIrUTu+sJlKNc+Gxm4sz/SPuIDlIDLbcmnIPIMXRIuXFXNzD23ocCEJu7C0Z5r2V8bYiGl9EFqKpYPhYvcql4bdLmfapDKeI9RI91qNI3hP2PnKIDJPftOi7y3odYCkr5MZKM9exgCaDI2QdIGKagACknF4wdWqTUCHZauRi+PnB96h4ggFiRIhnsq/P9LoG0AakHehznhkn9lhDBS2thws5tAd0FEFbhZ5H01OmzGZllhxwoS3FhQog== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=cFD/qT4OVfg9dr7c4d4vbfsAInr6LCgB7utzTN1z3rc=; b=0TuNunIeeRMJl3tJW5PTa1xNW+DO1xRuGGHcAjCXlfPV+JMC5as8gjuLJ5bS63SYnIxOlBjIe619WXOrH8m8WFFUz5WUVb3SoKHnp35p9LxUUIMXlW8tJkxAN9LWqAtucCiLjUzrFlJ+BYtmCEm6x90XF5L2hw6Lh9DYdhq+xcg= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=citrix.com; Date: Thu, 22 Jan 2026 14:05:53 +0100 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Jan Beulich Cc: Andrew Cooper , Anthony PERARD , Michal Orzel , Julien Grall , Stefano Stabellini , xen-devel@lists.xenproject.org Subject: Re: [PATCH v2 3/3] xen/mm: limit non-scrubbed allocations to a specific order Message-ID: References: <20260115111804.40199-1-roger.pau@citrix.com> <20260115111804.40199-4-roger.pau@citrix.com> <858d73b3-2feb-419f-bf3b-9a264e9f9af8@suse.com> <97127b23-4e4c-4b06-a8bb-b1dad31bf0b0@suse.com> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <97127b23-4e4c-4b06-a8bb-b1dad31bf0b0@suse.com> X-ClientProxiedBy: MR1P264CA0077.FRAP264.PROD.OUTLOOK.COM (2603:10a6:501:3f::9) To CH7PR03MB7860.namprd03.prod.outlook.com (2603:10b6:610:24e::14) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH7PR03MB7860:EE_|SN7PR03MB7153:EE_ X-MS-Office365-Filtering-Correlation-Id: b64d5b5b-28d0-4475-137a-08de59b6fb7c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|1800799024; X-Microsoft-Antispam-Message-Info: =?utf-8?B?SU5nWXhyRkNPKzhTYzFwNkRwQjg5L2RMYWc4STRpV2QrejFNMXJ4VUd1bktN?= =?utf-8?B?Q0l2Q241WUl0RnZ2bTBiN2RQM1h4T1d4NEpWcFBOZnpKTFRKNmgwN1EzMndx?= =?utf-8?B?WU1tMjd5d0tpb0NraVVpbzRPUzJUS1YwejFNK0N0bGpSQ1pXdDV5TmZ2elBU?= =?utf-8?B?Sno1eUluakpMWmI5U0I3SGZGdFg5VmhpeVRJeWlaS0FtTmgrOHQ5NURlOHhk?= =?utf-8?B?Yld5MkdlM2I4c2lsTU5HMVRJaUkyaHJZUGNVdkhwTUVmL3dUUVRCU0VUVllF?= =?utf-8?B?ZVk4OUJYbDhHcG9qR0I3NDlVM2ZjZEFnNkpjNFdldk9xYWxaajIwYlZrMlVB?= =?utf-8?B?d01hSGVjNytYekpDRE1aVXhaYWtHMVJUM2JIelU2bVg2WHlrcW45S0xmNCt6?= =?utf-8?B?UXF2RUxKdVJpVkNDdzB4YWc4YktWajlBY2owTlN6UHFlZmNENUU3Y0NTMnZK?= =?utf-8?B?Q0NYUGlObkNaaDJnWnhwdUZFVVlQenVSRXdJOVZ2VnZFWm1udGZkVlhuSk93?= =?utf-8?B?OXR5OFdrRitTRTFNWFB3QjlmcFRnd21XZmRCUHh4U0NPQjhRVWE5Qk1tRzEz?= =?utf-8?B?ek5TSHpidnBMQzJFc1NLdjVwOE4xdXQ5T2pYdUQ5NVdUbm42bUp2S1ZFTjZ6?= =?utf-8?B?dms4RmFjMnBncERsd3M4WVNnWG9QMjVWekhyc1ltaHNhWmN0N3JMVFR4YXl6?= =?utf-8?B?WTlUQ2kxUXJmc0F5OEJOZUk4a00xcWZ2b3h4RnA1L3R6bllXb3E1ZFd4ckRs?= =?utf-8?B?ODhSMWdCdkdIRUEzb0xFdHowQVY4MjdvWlZSNjJaaU4zRlNTbHNpMCtiR0JK?= =?utf-8?B?VCtZRjBDSzg5VlpSUUFLdld1QWphSDdoQ1NrMjQvbVZGT2pVazBpdUhVLzM1?= =?utf-8?B?OVV1cnJTSzlLT0hTNE9JVktHZTJwNlhyUGpQZm1VTEpPZGM5MzBzWTRVMmRi?= =?utf-8?B?KytnL0ZtQmI5M0VhSEtRWkxXVXBFd0t2b3NndUI2bWZZdjVsOEcvSW42azJV?= =?utf-8?B?T0NyUloyT2VxWlNubmo1dEV3WU9BUnlUL2R3djU0ZVlBNFA0ZDZpQkhVa2Uy?= =?utf-8?B?UzVIVmNydjJWeGF2NUErYlNITm5rK2MwQXJmbHZkdWMzbVdaWFMwUTF2VjVF?= =?utf-8?B?Ymw3d1cvMWIvL2xaUUhGTVlwSDN2SlJQUFQ4VE8zc1M2ekUrSUo3VXBvQXRP?= =?utf-8?B?ZEthMWtlZnd6bmUxRjdVNy95bDZiRkJPbDRQb0x5amlSWmFyYWZOaTJWOG55?= =?utf-8?B?Q3JZY1pCR3BqSHZWaTVDeW53c3JNZXhuVk4yVzRodSs5UzFZV2FaOUgvWnNF?= =?utf-8?B?aVFsWmFEWWJmMnlUZllwWWNabGU5bDlQbkJEQ3JnSHVwOEMrQVVtTTNLbVA2?= =?utf-8?B?Q0k5R1hWc1VKazJmWWZKZ29ZUGtzSDhyamt6SUpkdnl5b21naGtXbE1GL1g5?= =?utf-8?B?aEZZUFkvK2pBTVRsWEgyNjNSMlJubzUxSGFrdkNtdGEvTVRRSDdGbjFIbU9C?= =?utf-8?B?Umg5M3pjNW9BSDJNUE16N1dUWnFzeUEvRms4QzVySExBbjdoRFdZVU9IbFQ4?= =?utf-8?B?YXR1Vy9wRExTanBGTms0UzlpZGlra2dHL1hXV1VXZ1ZtVlkxaFBrZ3NQckRN?= =?utf-8?B?NlQreXBXdCtobVFWbk0wWDBUa2JkcGtDSjRNd0I4RlA5QlQzQnhBUkYydk9G?= =?utf-8?B?emxYczVPaTJvNDFZNm9mNzlwbHlYV0hMVUR0c3NFV3VTcnhQd2JJQi9WcWox?= =?utf-8?B?NEtFYWJreTBPM1RPS09VYzdUYUltRjF0Q29NbU0ydnkyUnVoMzM4aEFKLzVN?= =?utf-8?B?NjVjd3VHRHlQZEhpRVFTYXdNUWZ4MW5xcWowM3JLMWtlTTNrVjRNMzN3Q0l6?= =?utf-8?B?cmEyVnZxcVdZRnZQSXRZOFB1a2lsNGZOOW5obFNSeEppNFpqTFVLT2tWVTBO?= =?utf-8?B?Ym8vb1NOT25zUzFPeTlLKy9ORzBPbS9hT0FqUnhBZ3lUdTdHZml6TWJFaFdE?= =?utf-8?B?b3Z3YTIvRFBmQkM4UERFbUZ1Szl5dTJ2Z2NPUkQvZjV0MUNXVHFWOWlFeWxS?= =?utf-8?B?dVdnUmFUY1JZTHF4V0xjWEx3RU1aNldJbWtmdFlKdlFaN2VMdEJTcUNzcXJh?= =?utf-8?Q?1KjE=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CH7PR03MB7860.namprd03.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(376014)(1800799024);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?dzBMU2xORysycHc3cys1bmlObWRUc1JFYWM1RzNmTmczVVJ3NS9XNzBIRWw1?= =?utf-8?B?WERZNHEvWk83RFZveHMyODZRRFhXUDI2MHRybmFsTUgwWnNMc0pSNVY4Qy8r?= =?utf-8?B?RHpPTVhHam5udVgyRG5OZ0JhMG5IY3BFRDRvNjNqSGpqVU14bCtBRm1jZGJx?= =?utf-8?B?cEVEdExZVWswdVhQMi9GMC9yaWd6Mk5SaHFxQmlXMFVsQ1dNdXVOUlhSUjRL?= =?utf-8?B?bmV3QkFuREZrTUJPdFpETGlDVlpqdG94cXVkakNkUDJYTXdmK0puTUlkdFpX?= =?utf-8?B?MFRpWkx0VEdINFBPME1jeHdwV09ud0pONWZqRmg2U2RRSk4rc2JDRnJkZmxH?= =?utf-8?B?V1cxYkhBMXFaQjU1RTBxeThqVk9xWmxMR0J5UXFRK2FROE5heW1GYXlaMlJP?= =?utf-8?B?TnhMcWw2MWdPVExmYXZTSmFMdjRHSm1ySHplaG1KRGFYOW5kOU15Mm9JOTEz?= =?utf-8?B?cStYVVVCZWFSMTJ1RDRYM0lraFU0WmhnMmlqRFdMMU5xWTB6UHNzRlVOWDJH?= =?utf-8?B?VDc5WGhTWDc4d1FpMUFBWUJwMUkzdFJ3bUlQVlZhUFBKN3BndDdSOEtvTWVt?= =?utf-8?B?SGVuM1k3QkxXaGlqYURiTFBpSjhBYldaTkNyQWtlVG1SYmJXa05YNzM3YjZI?= =?utf-8?B?ZjM4eDFjMDJrNDFSZmZCZS9OZ0RXRExzTG1YYVE5cWxlTUN1Rzc0ei91SWxG?= =?utf-8?B?clBrWmlSNlgxVUc4MDBLblU3YkhWVFpvQVlmYm8xZDdVWFVEZXBBak1obWdr?= =?utf-8?B?UjMwcm9RMkF2UThhOEg4ZDBPZ1ZMNW1TQ0lNNlRieVVQZXdJU0pLTWpOc0RI?= =?utf-8?B?b0JCUGdkUExFdUhNSGtWbDF4T2F2TFdFcGhFN2tPcnFVNFFwSngxN0lUS1A4?= =?utf-8?B?RkxQRVdMQ2lVc0s0emh1OGVYbEwxanpka3BrNVVaQ01zVUVnNWpJTG85Y2dw?= =?utf-8?B?YVFsb1ljVGk1a0dPOU12YlJZRGpxMjgrZm1UTllPN3BLSVVoUHg2b0l4SzZn?= =?utf-8?B?amRKbmg1azB6Tmc5TEQxYnlkUDFtSndKQTBRSHQyQ25qVGt0bTBUWjA4UURO?= =?utf-8?B?bnVudkxNSnlPOElZZW1iK0Y1YVB5UHZBNnQvWWxJVkg1ZDdJY1owalBFK0tP?= =?utf-8?B?a2Q0TWxFR3A1L0xBU0ZFMXFsUW9BbXJVb2MydXZDZVUxQUJzTlQySVRYMGxR?= =?utf-8?B?dHVNSExvT29GWHR5OUU0UmExdEZUcWRKOWc0NmxqbUNKQmJ0cURzV2RwZkFE?= =?utf-8?B?TVJxbStqMC9ZK3htNk12U2owdDB4QWlzeVl3cTNKemYybU5MYjhUNkpnUTlx?= =?utf-8?B?Y1I0L1hwTnFMWEl2MnRIMHpIaWpBUkJrYzhkY0RkSkJqcWlaQkFZMXdlNWlD?= =?utf-8?B?ZGFENjYrc3FEMXdFUVlOZlV6emxwdzdNOWl4QzZDMGZPRXAyZnlNRlhwQ2dK?= =?utf-8?B?Q3NBemlaRkVBbTJJaVlGRHlFSUNSMy9SNUJINFg4Wm1USndDd2dSMUxqM1h5?= =?utf-8?B?Kzc1V3lWelJlMHQxNTJBMzI0MGVDR1l1SytKVnRWNTlCMkpkcXliSWZoRUUy?= =?utf-8?B?eGhXZlVadkd3dG5LcGhDS2JRVjc3TjRRV3JwQmt0alUzWXc2U3k0L2VCZTVM?= =?utf-8?B?QVBzWkJ2dCtSd3N4aVpaMHFGaWZOOHJydFd5Q1FRRytDaFpnbnYxUmk1anNi?= =?utf-8?B?OUNobkZNTksweGFCQmtDOThrOWllem9aQzhlM3hBd0plWXE0RkFXL09zTm5P?= =?utf-8?B?NFdsNjlKTjlEa3RjZEVSUjhTdURMTVdyeTJFZDh2M3JxZk5zcmVPOTB5Tytl?= =?utf-8?B?ZUswei9vK1k2Y0drZ0t5emliYVdGL2FpTEI4Y3lGLzRwRjhxSVpNd0xGajhB?= =?utf-8?B?YWxZd2FnVXRPdlB0Y0x5TVdaV0dLVlZxOCtIUXorQzJ2UXJZQ1VXMmw0eit2?= =?utf-8?B?dzR2V3ZVZGxSOURBeHN3M3FiTjArbnBtSWNFOEppclE5bDhFVDdHQ0dkaEZ4?= =?utf-8?B?VjF3Z0FpVGlmaHlOQnNFanpOdVJ0LytQSXhKK1BRdGlWL0JGK25STDQ3NWNz?= =?utf-8?B?eEpuMURncDJ2Z1pua2oxWXJKc2J3dklpUFlhQUx1NCs5RDgvTWJnTzV0dE9L?= =?utf-8?B?YXNnRUhGMjQxbHlnYVpPcXBZR0QyZGxVUUh3a0p1MVRxbnpFSkxMOTZxOEZM?= =?utf-8?B?bTF6dEVtRzFtNk5WSjFMMTRqdm8rNFI2QzduV3JGNzdMZDllaUN4aU5iekYx?= =?utf-8?B?REVkWndpeE45R1h4THMwYi8xYTl4Yy9rOWhtTXA2eGlpOXRLTnBmSjBOTGNM?= =?utf-8?B?Tkl5UG8vRENMeWh4aG15SkRQbzUxRXo3Rm5qQ0Rwc0h3M2I2cEg2Zz09?= X-OriginatorOrg: citrix.com X-MS-Exchange-CrossTenant-Network-Message-Id: b64d5b5b-28d0-4475-137a-08de59b6fb7c X-MS-Exchange-CrossTenant-AuthSource: CH7PR03MB7860.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Jan 2026 13:05:57.3291 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 335836de-42ef-43a2-b145-348c2ee9ca5b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 8WKqmwZTpG07j2wqTCOs6MsU9+XYdCEhZJaqfFcWi+pNCEGm2H3P15/nDNb2Umb01kYgUA6lTkEqY7vCLbM3fg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR03MB7153 On Tue, Jan 20, 2026 at 08:25:49AM +0100, Jan Beulich wrote: > On 19.01.2026 17:13, Jan Beulich wrote: > > On 15.01.2026 12:18, Roger Pau Monne wrote: > >> The current logic allows for up to 1G pages to be scrubbed in place, which > >> can cause the watchdog to trigger in practice. Reduce the limit for > >> in-place scrubbed allocations to a newly introduced define: > >> CONFIG_DIRTY_MAX_ORDER. This currently defaults to CONFIG_DOMU_MAX_ORDER > >> on all architectures. Also introduce a command line option to set the > >> value. > >> > >> Fixes: 74d2e11ccfd2 ("mm: Scrub pages in alloc_heap_pages() if needed") > >> Signed-off-by: Roger Pau Monné > >> --- > >> Changes since v1: > >> - Split from previous patch. > >> - Introduce a command line option to set the limit. > >> --- > >> docs/misc/xen-command-line.pandoc | 9 +++++++++ > >> xen/common/page_alloc.c | 23 ++++++++++++++++++++++- > >> 2 files changed, 31 insertions(+), 1 deletion(-) > > > > If you confine the change to page_alloc.c, won't this mean that patch 2's > > passing of MEMF_no_scrub will then also be bounded (in which case the need > > for patch 2 would largely disappear)? > > This was rubbish, sorry. Besides my being thick-headed I can only attribute > this to the double negation in !(memflags & MEMF_no_scrub). > > I have another concern, though: You effectively undermine ptdom_max_order, > which is even more of a problem as that would also affect Dom0's ability to > obtain larger contiguous I/O buffers. Perhaps DIRTY_MAX_ORDER ought to > default to PTDOM_MAX_ORDER (if HAS_PASSTHROUGH)? OK, yes, I can default to PTDOM_MAX_ORDER instead of DOMU_MAX_ORDER. > Yet then command line > options may also need tying together, such that people using > "memop-max-order=" to alter (increase) ptdom_max_order won't need to > additionally use "max-order-dirty="? At which point maybe the new option > shouldn't be a standalone one, but be added to "memop-max-order=" (despite > it being effected in alloc_heap_pages())? I had concerns about adding it to "memop-max-order=" because it's effect is not limited to "issued by the various kinds of domain", this is an option that affects all allocations. I could try expanding the option description to reflect that, but I wasn't sure whether it would lead to confusion (as all options there are per-domain currently). Also if added to "memop-max-order=" the parsing function needs to be adjust a bit to consume an extra parameter in the !HAS_PASSTHROUGH case (which is not much of an issue). Thanks, Roger.