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 16228CD6E4A for ; Tue, 2 Jun 2026 13:09:46 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.1325007.1590519 (Exim 4.92) (envelope-from ) id 1wUOsB-0005Vu-Fn; Tue, 02 Jun 2026 13:09:35 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 1325007.1590519; Tue, 02 Jun 2026 13:09:35 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1wUOsB-0005Vn-BL; Tue, 02 Jun 2026 13:09:35 +0000 Received: by outflank-mailman (input) for mailman id 1325007; Tue, 02 Jun 2026 13:09:34 +0000 Received: from mx.expurgate.net ([194.145.224.20]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1wUOsA-0005Vh-D5 for xen-devel@lists.xenproject.org; Tue, 02 Jun 2026 13:09:34 +0000 Received: from mx.expurgate.net (helo=localhost) by mx.expurgate.net with esmtp id 1wUOs9-003ioW-Pd for xen-devel@lists.xenproject.org; Tue, 02 Jun 2026 15:09:33 +0200 Received: from [10.42.69.8] (helo=localhost) by localhost with ESMTP (eXpurgate MTA 0.9.1) (envelope-from ) id 6a1ed5ff-5cb7-0a2a0a5109dd-0a2a4508b5a2-40 for ; Tue, 02 Jun 2026 15:09:33 +0200 Received: from [40.107.201.6] (helo=CH4PR04CU002.outbound.protection.outlook.com) by tlsNG-c1860d.mxtls.expurgate.net with ESMTPS (eXpurgate 4.56.1) (envelope-from ) id 6a1ed60c-63b5-0a2a45080019-286bc90613fe-3 for ; Tue, 02 Jun 2026 15:09:33 +0200 Received: from CH7PR03MB7860.namprd03.prod.outlook.com (2603:10b6:610:24e::14) by BY5PR03MB4951.namprd03.prod.outlook.com (2603:10b6:a03:1ef::24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.92.7; Tue, 2 Jun 2026 13:09:30 +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 15.21.0092.006; Tue, 2 Jun 2026 13:09:30 +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" Authentication-Results: eu.smtp.expurgate.cloud; dkim=pass header.s=selector1 header.d=citrix.com header.i="@citrix.com" header.h="From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=mDnLcOxadTY/HHl7WRJvPFd3VCgSAkJUGxkx8eJLDfyqG9NptbojLxz10X+JRjFti33/NKTpEk0LJf1mNrOuIoQruIwWwynKDQf2Zz54/NOYg/Tz/GQmyWIMReP9M7OzMQlJTFkwaZULdM738/kZhLVLA2c0Wj6OtyE44HrdWb4runbEHYf2gZiwm/DN81Pehs34xLTCHAaj0OdtpULgEzQCKH3CYQMRaL6Sc2pT807lU4EdiSePLS7fnPLZBHKWCyDYq8Y/DnDD2PBPgyojNEQsQMxMGW2E+CoX0h5uHB7a4gK591Ucl3XBMzd186FYg6CY+V6foQ62DCA0kD+fmw== 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=wOyHAdNRnSbAKIrq+mXowVimhqtVHKNabqwahNEHcXY=; b=MAynxGMurrP8elLgbTMFS/5YkeXOD39U8bVZIl/gOiNnc6PryKUaLvenf3k4xgZjFFglInY1GgdjuckJ/r8wAYUC/cmuVxKywE82jNkFqNsp3kG7Pfe76cQBfYpB302VYgrTTU6DgW7qhCHs77DGiExE1USzOuTYc757iWYA4yFNZCKeL8UJVvMQrmo4ijpSGdBoLNbp5sWAECfAWAm7dYnxCcsOiDGXcZglkhTd6k8+PoziNIQjx0UeAgiP1fXpu7h3DmyJhIBUejlNubTGuCiGxl6L8o3cnW3gLSUlqCFWMNBgPtF8s9pyI+r9B4V35dJqvWKQbnEvghmGzOsABQ== 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=wOyHAdNRnSbAKIrq+mXowVimhqtVHKNabqwahNEHcXY=; b=wvK90Nl4SDrefHrst4m2brFf1fJXtJrhz6nFL+fJS8kXTXUtNKQDr5jk/YYfdTkzIOtY24b0sVlsPQWoc22+003fompPL/f3cPNdsmtqOOgfjE1m2JdTXl4XBKZGjAMjBh/G31TRzY0/NEeEfOLRF23VPo9NBL3djLzhRM3qM+A= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=citrix.com; Date: Tue, 2 Jun 2026 15:09:27 +0200 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Jan Beulich Cc: Bernhard Kaindl , Andrew Cooper , Teddy Astie , Anthony PERARD , Michal Orzel , Julien Grall , Stefano Stabellini , Tamas K Lengyel , Alejandro Vallejo , Marcus Granado , xen-devel@lists.xenproject.org Subject: Re: [PATCH] xen/mm: avoid watchdog timeout in dump_numa() on large domains Message-ID: References: <10d8309efdb878a3b615a7daca2bb5209525cb37.1780390167.git.bernhard.kaindl@citrix.com> <4f3f6ead-b917-4824-bc24-47a37f921bf6@suse.com> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <4f3f6ead-b917-4824-bc24-47a37f921bf6@suse.com> X-ClientProxiedBy: BN9PR03CA0563.namprd03.prod.outlook.com (2603:10b6:408:138::28) To CH7PR03MB7860.namprd03.prod.outlook.com (2603:10b6:610:24e::14) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH7PR03MB7860:EE_|BY5PR03MB4951:EE_ X-MS-Office365-Filtering-Correlation-Id: 07181b2f-69a6-4219-9f41-08dec0a82e3e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|366016|56012099006|4143699003|11063799006|5023799004|22082099003|6133799003|18002099003; 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:CH7PR03MB7860.namprd03.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(376014)(366016)(56012099006)(4143699003)(11063799006)(5023799004)(22082099003)(6133799003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?WmI2REcyZ1c0YysxQ08zMXNOcHAwRy9vdFRPejZpeU9tNzBwemVNaUp2SXQz?= =?utf-8?B?WnJVc0dVU3A3MWVzRmlJcEIxYTUxU3d3WmJRUy8yMkVRNkJFSTIxM25VdTlQ?= =?utf-8?B?ejd0cDN3UWNFVXdqNjY1cWZSVXU2bUZNRUlBeWxoT1k3Z3BJSk84NFFUSGNO?= =?utf-8?B?NjEzQndteUtCaXRKRFVxRElDcGExWlEvekpsbytZUW0yT3ZZcEkwcU1rR2ta?= =?utf-8?B?ZldVUjJ6QjZzb2ZZOStKQi9MbTZKMmpDbGRTMkNOU2hDQ3Q1Vzc0YnJSbGtR?= =?utf-8?B?WGxIdFBacG1XRTJ4UytPL2RTdG0rY0gvTGVHaW02NzZCK1pORWJZaFRkSG96?= =?utf-8?B?MnN0VmR3aVIza1JCOE9lV1g5alhtQ0lSZXkzUWRUS3JxNzdmeitsQ2tVQVpB?= =?utf-8?B?S20yTEJMa2g0WWR6ZWJjdzRrVFBtaWJFWDJYMTc1TTJ4R1ZQS0RLcUllelVW?= =?utf-8?B?UkJQVm4xcHowZ0FxazhRZlpva1UwRGhKSTNXRjFQRjNxUjFpdUJzbDRCSTNL?= =?utf-8?B?cHhZa0JvT24yM2FncGtmNzRXMWpIb2JuQUtnamJxdFloTjRrTFdscC9tNHZ5?= =?utf-8?B?NVVUTUJoV0Zaamp3bHg3UHY4b1lZTDJlMEl4cURST3VCL3drRXBsMUpvUnpC?= =?utf-8?B?bCtSdytRNDdNblFwbllPR2xEeTdmYXRuSkg1VjI4STFWeE9FaEd2cjJERVlU?= =?utf-8?B?ZjkvNUtYRW9Oa01oQWZpWUEzQzR4RzROT01vcGQ5UEU5SE1xRW8xeklVUjVp?= =?utf-8?B?c3RBMDJtOXI1MFdTM01DcnlscE41M3FTK3lPdjJkRE4wK25Lb2lLVEIvTEND?= =?utf-8?B?WXdTckg4TklST0NkaGFqcHFDMk1zWGJTSmVteFpqMnNBQXkxQWdFTXpsSy9I?= =?utf-8?B?cHlCalhZYnh2ellMSDFVTTFZYURtYkZ4R3Z0b0taS3hRMXNHbkx4YUVHcVpC?= =?utf-8?B?YTZmL1M5K0lSSThrd3dLZWQrSVNFL2hDcTFyQi9pS3lVK2phZHYxZXF4dWR3?= =?utf-8?B?ZlNST1dKYzdJZWNLVlBRODJ2M0dOWUlyMldWMk1zOWp5TjRHcVJBVndBb1Yz?= =?utf-8?B?NmJ2emZmWUVPbjUzNC9NOW5VWmwzK0JFSk1JRC96OXhpYXJGNXZIZVFnbElv?= =?utf-8?B?U0RLNVJaZ3o4TEZWZ3RwUmRKVkxiMnZkNWU1WnhPaTBqZlRGckQzY0M0eXdZ?= =?utf-8?B?eG1yT2lRc1FHd0l2NDJlR2lES0RPSGp1SWVNcE9aUkkzb2hCS2dtTmxXVXZm?= =?utf-8?B?TjVpWFJuM3Z6M3hSMWRqcGdwYmNhZEVtbldXTVY1d2JzV3FObUVaTG8xK1o1?= =?utf-8?B?OGlHazZDSEladWRIRGNjMXRmeWZHTkRTRXJKRmFQcmVDRDdEbTVYT0pmM3pF?= =?utf-8?B?NDlkZmVLYjNYdHZnNW9qYklyOWNzeU9tSWI5aEJGNWd0VHMvd2lGbVNqbysr?= =?utf-8?B?YmUvdkZLTktITlhZc3ltY0p1YkJKcUJVZlZRMlF6alRNNFNOTGRoaiszdjNq?= =?utf-8?B?TEVNQ0dlMlZFZ3lpaUdKTlFlOUw1QjNEdStaemFlcEVtUTA5dXhJcXJkRjVL?= =?utf-8?B?S1UrN3d2T3A3V1VrVTFnaUpJR1Q4UkZ3U0tFUW9MUU0yKzVFUVI0RU5SV2l6?= =?utf-8?B?WEdyOWFHL3A4aXMzcU1CN1pyZkxNTjZoNHdQYXFsaUdZaUpiL3BMSUpPUUVD?= =?utf-8?B?MTdMQVg4TVdsSC93bEZnTXJ1NTZPeWEvdXBLQnpPeGJ0Q0FxaitYSlZ5Smdr?= =?utf-8?B?eWswRk95ZGY4QzZINXI0ZHJybWdqaDlvdjlUNlhqSlVkbHNGQS9aVnh4R2RY?= =?utf-8?B?L3BBbndwYU9sYkxmb1NzNmFPU1BTdWpSTnI5Yk5tb3BuNlVWSHY4ei9ZaEk2?= =?utf-8?B?OFdBMXFIUHp0NTN1RUhIdnJwZEZ3bEpJaXZiMk03OE5TdmZGa0lQSVN4UTNO?= =?utf-8?B?Q1VnU1lYTGdvUzJ0Y2VXb2pUNkZzSFFTQmlSWGNRU3BrZkE4MHIrdG1mZ2p5?= =?utf-8?B?R2xUREVzdGVwL3RHNm5FYUZSRVd1cFBXbk1nc1NPekRLK2d2U1VuQ1YwbEFv?= =?utf-8?B?T3FqcktiQm15VlR0RlJKa1VrcjRud1N0NXpWeENQSzljdTRXVUhOUDA1SWsz?= =?utf-8?B?QVZUMTFOWlBETHcrWDJTUmtUaisyQzhTK01nVnczWXNUTHordlIrNlYrcU9X?= =?utf-8?B?SEdJUU9jZC9vdG9Wd0RBMXlVWGxyNTV4dnQ0OUhoWHlOcnBuL3BWb2hxdlZ1?= =?utf-8?B?dnVBUkpZMXpQQjR5Z2FHZ1lzUnZHMmoyN2JwNFNHZ1o4VERpRGcwSm1vczZP?= =?utf-8?B?Wjc3eFNtYzR5LzZsazJKMVZkK3psSysrR1dBNEM0WGNYbEpkRE84Zz09?= X-OriginatorOrg: citrix.com X-MS-Exchange-CrossTenant-Network-Message-Id: 07181b2f-69a6-4219-9f41-08dec0a82e3e X-MS-Exchange-CrossTenant-AuthSource: CH7PR03MB7860.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Jun 2026 13:09:29.9067 (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: 5lKaTXK8qr2ZY1TGdu9nDAvxmz+6oeFvtt69mjqVXjuMuC/rV+mIzpI5t/BGGQjl0xoJJoRNCQkIOdCrXU6fwA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR03MB4951 X-purgate-ID: tlsNG-c1860d/1780405773-C4E78DB1-FA19F5E4/0/0 X-purgate-type: clean X-purgate-size: 1386 On Tue, Jun 02, 2026 at 01:51:13PM +0200, Jan Beulich wrote: > On 02.06.2026 10:49, Bernhard Kaindl wrote: > > Using the 'u' debug key invokes dump_numa(), which walks each domain's > > page list under page_alloc_lock to compute per-NUMA-node counts. On > > domains with many pages, this O(pages) operation can hold the lock long > > enough to trigger a watchdog timeout. > > In addition to what Roger said: Is it really the lock holding that's a > problem here? That is, there would be no problem if there was no lock > involved in this O(pages) operation? > > > Replace the page-list walk with node_tot_pages[], a per-node counter > > maintained in struct domain. This reduces dump_numa()'s per-domain work > > from O(pages) to O(nodes). > > Alternative approch for consideration: Purge dump_numa()? This big a > change for making a keyhandler work better is somewhat questionable an > approach, imo. The keyhandler isn't there for use in production anyway, > it's (primarily) a debugging aid. If the data is still needed (and may > e.g. be useful on production systems), make a (preemptible) domctl or > sysctl or alike instead? At some point a similar change will be needed for per-node memory claims. While we might refuse just for dump_numa(), the intrusive changes in memory_exchange() are a requirement for per-node claims IIRC. Thanks, Roger.