From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from CY3PR05CU001.outbound.protection.outlook.com (mail-westcentralusazon11013052.outbound.protection.outlook.com [40.93.201.52]) (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 A60EC3EAC84 for ; Wed, 20 May 2026 15:22:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.93.201.52 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779290547; cv=fail; b=l/TUd3F6yznGgu16dPSTo93LYqi6y16Ue6KHQfl9LavL1DTXzlEiEQWkNutxoPAL+wFiCYgEvHtGtiqm4NEvrQyQpJ8bUlsPEU+dZQJ2PZXqEe0dyFdFkuWIHtc60AP79aMxUFRnLPu1AsTbKQCV7gKiwS8KoIOolHz7LnCsQKg= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779290547; c=relaxed/simple; bh=PsbX57TpURvYdsNNRtSJKIdkQJYdTNiwUGGgo0de9GY=; h=Message-ID:Date:From:Subject:To:Cc:References:In-Reply-To: Content-Type:MIME-Version; b=og8YGzEW1nODzalXvqjPOS8T3FuulPQRaE8M7a04DeQZNJvsU7cgeK74KIVll7296Y94SrDgV9RwYSEt7d85gRTKmbHOSq3OE1dmmOiZDFEwNTXvd/6w9o0GB5EA9zirgZQSElOKUWlrXgZZ5gTrlwChSrIHVJBXMzYyoprooM8= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com; spf=fail smtp.mailfrom=amd.com; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b=e41nh0nX; arc=fail smtp.client-ip=40.93.201.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=amd.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b="e41nh0nX" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=FhHlcsCIYzZaAk+TqR1kZihCVkRdOjUIpcHhX8Bt8lYMfqGULc/n9bQKmQaBaSst4xzQxns9e/8Llv68lFxFe7tDy7xiZQdeJ4si6PNB4L9QahHa1RKJh00ssTcjljImnDskxfmpF+nNkm+SKD/nDwQmirSAcYjj0udXat4nRm3mALpQKOlw7pJNLZnSwjjrVhGxT4Nm7VB82T4oZ2mwlS6DyJT4pCejH5FJO9yO66sF6Cjnmnlk95IMOBo+pwEd3VFrKaZuyvORL8RV0zUpGo6DVdW8dowuowiZfURFu+t6q6l+GW3M3A+0novxgfEL7mXmLBzaocQloaa2NtdeFA== 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=u8mX2PjBicXkBslPywg1I4hiqxP98nvYwtWEvdDiZPQ=; b=CdcR+rPc2J40jVTK1QNpDA+2pMZsRlpaf1BUhjkemWCvI0DHjWRvd3+VsBvb0glnUDJgr8dgYjgSWN4kjlL0lygajvpy5btL0fwnAyEjnqRk2WRsZDHwDFZVUNCmx3kdtoncdk+tsv7qy3DWAq2dR4KANjhgZdFbvmhCnAg614foMpc0H10C082GF8A1VTe1zdbdPPKP3f8HKzjgwZTNV9UGBU1pOopx4loD2XBUM01VNUKiA+hnr7KvExDq2UWLc0s1HYTHIc0a+kg+sQtcq/4GhByYivNFUOLFPj3Oj1L0kNxS0zgOnkemieYtWdqV+Mp9gEGbvPia2nQMVU+0fQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=amd.com; dmarc=pass action=none header.from=amd.com; dkim=pass header.d=amd.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=u8mX2PjBicXkBslPywg1I4hiqxP98nvYwtWEvdDiZPQ=; b=e41nh0nX+1PqatoPCfxUYTIFe/fP3TMvtjmsbJwfMdSX47xmuR2jAwgekZ9nG5lIeZUuZ33a+CFAtBaTkmRJHW/JjTZLCoAl5NBjAGmVaj5OgA2M2keCGHhcbmrkGUQaV1cHQHVwnaThJZebU/qWJKCmKHfDCvq2yuglPSMVYc8= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from BN9PR12MB5259.namprd12.prod.outlook.com (2603:10b6:408:100::17) by DM4PR12MB8498.namprd12.prod.outlook.com (2603:10b6:8:183::11) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.48.14; Wed, 20 May 2026 15:22:21 +0000 Received: from BN9PR12MB5259.namprd12.prod.outlook.com ([fe80::122c:cca7:c2b3:90ed]) by BN9PR12MB5259.namprd12.prod.outlook.com ([fe80::122c:cca7:c2b3:90ed%4]) with mapi id 15.21.0048.016; Wed, 20 May 2026 15:22:21 +0000 Message-ID: <70ee3800-0469-4c3d-8a1c-bb6594c64f42@amd.com> Date: Wed, 20 May 2026 20:52:09 +0530 User-Agent: Mozilla Thunderbird From: "Garg, Shivank" Subject: Re: [PATCH 5/7] mm/migrate: add copy offload registration infrastructure To: "David Hildenbrand (Arm)" , akpm@linux-foundation.org Cc: kinseyho@google.com, weixugc@google.com, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, willy@infradead.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, dave@stgolabs.net, Jonathan.Cameron@huawei.com, rkodsara@amd.com, vkoul@kernel.org, bharata@amd.com, sj@kernel.org, rientjes@google.com, xuezhengchu@huawei.com, yiannis@zptcorp.com, dave.hansen@intel.com, hannes@cmpxchg.org, jhubbard@nvidia.com, peterx@redhat.com, riel@surriel.com, shakeel.butt@linux.dev, stalexan@redhat.com, tj@kernel.org, nifan.cxl@gmail.com, jic23@kernel.org, aneesh.kumar@kernel.org, nathan.lynch@amd.com, Frank.li@nxp.com, djbw@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20260428155043.39251-2-shivankg@amd.com> <20260428155043.39251-12-shivankg@amd.com> <9145ae5b-a33e-4092-8cb5-efa18ae61287@kernel.org> Content-Language: en-US In-Reply-To: <9145ae5b-a33e-4092-8cb5-efa18ae61287@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BM1P287CA0016.INDP287.PROD.OUTLOOK.COM (2603:1096:b00:40::27) To BN9PR12MB5259.namprd12.prod.outlook.com (2603:10b6:408:100::17) 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: BN9PR12MB5259:EE_|DM4PR12MB8498:EE_ X-MS-Office365-Filtering-Correlation-Id: 239e4249-1613-40ba-609a-08deb683968b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|376014|7416014|56012099003|22082099003|18002099003|11063799006|4143699003; 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:BN9PR12MB5259.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(1800799024)(376014)(7416014)(56012099003)(22082099003)(18002099003)(11063799006)(4143699003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?ZmU3dHdNMDh0Nk90VHNTY25lQlFGd1dXMzBBcHBQM2J4MitCWUVJNnNXWXlK?= =?utf-8?B?bk1PZGcyWEtqRGd6ckJCbUNGd3pxT2xFWHZ6ZlJzU0FGNC9FVE5CbVlnQ3hs?= =?utf-8?B?ZHAyZzJSamg3dldnRXF1bVhxQU9WTm5XaWc2Y0R6K2VRUnR4T1RZWjhKZ2hq?= =?utf-8?B?bHFUM3JhZ21zYlJVRGZBMnF1ZndTSW55UUI2SVZYWTdmTHYyZGNhWUdOR3dm?= =?utf-8?B?SG5pUFJZYjZxMElIam9Wa09DM2pnTlZIbk13RC82MERiRHRaV2hpSFI0Nmx0?= =?utf-8?B?SS9FcDNaMUxEdzQ2ZnZUMGtaTEkrbzFFOXhoU0JDMVdabTNjd0VoZGRFWXE4?= =?utf-8?B?MjBxMU5lY1RGVWg5VCs5Tm5wUmcrT3BuTk12MFpmc1BlVG1iaUs4ejBRMWFE?= =?utf-8?B?Y2FjRjhsYzd2ZkFBblVhVjRsUjIwZjJGMVBBblZpOWxDb2M2VWpYZUFlQ2J3?= =?utf-8?B?ZXVvSWF1eTNWQVdjcG8rMnN5VVd4TFRTaFhBK3RtUWcxdC84bStTRmQydDJ5?= =?utf-8?B?ZEg0cXpJYjRiT2UySTZQM05iN21xeXl3QlBYOVBYVklqQWowcm5iOVlOc0ZT?= =?utf-8?B?S2h2OE44QlRpOXIvdFFQMUt6blpEaGRBT1puRXp5TnNCUXoyNzRPcjU5TWRK?= =?utf-8?B?d28rdEUzR21DZ05sMlBCRUd6RldMK011UGxtY0JubysxeU9ha3J3V0grbGFr?= =?utf-8?B?NU1XQkRpVnVJcCtpbDVTY1JLL1R4MHorYUM4RW4xQm1ZNE1TZlU5QW8rZFBN?= =?utf-8?B?V3cyN1IrdURYaDI1bVg5MFZDeUNtT1htanZreUNHUjRHcnV4OEQ0YmtIZFNY?= =?utf-8?B?dGx0VVB1QUV0ZEw4M3U0OU1xaitiRyt3S3crQUlNZ3ZaZVFlVklqTDNLZFZC?= =?utf-8?B?UE9lQytGb29YYmNKdk02Y1V0dUFRV0h2Z1AxQnNVanp3djRXcGMwaG9QTDNt?= =?utf-8?B?YnB4WVgyZzV5SGJjWkpkcEkzUHJ3UU12SnFUMHZSbFJSZkM4Smt4bHdxK0Jj?= =?utf-8?B?TE80dUEvVVkvN0lGTC9QcVd3ZXViZGxtdmhyU3VFeFViQ3ovZnd3aXFLZ1Fp?= =?utf-8?B?VHZhTHRvL1dIbm1mQitGZndNZWhvaWo5d1Y1U3owalpFa2Y3V2NSN3BqNHNy?= =?utf-8?B?NmtVckNMYS9JK2lmRzcyVkUvM0luQTgxR0F4aEtnMXdNT255YWZmU2FhdlhP?= =?utf-8?B?UWY5b0pqK2kybWI0dUFWVmF0TEJURWFqYnhTWk1JUGVZTmpSNHpxWWEvQ2VQ?= =?utf-8?B?WnV1d2tRTjNJNnpNRnNTUUVkUjllMkhsV2d5d21FN3pUYzFEN1c3S2s1dk5p?= =?utf-8?B?dVR3ZWI3M2JiMjJGWm15NlZRN1FCRUgzem9EZllGSjNod0szYXYzODNrWjhC?= =?utf-8?B?SkRRY3N3ZFM5cUhyMEM3SmxVK1NrN1NoV1c5Tk1sTENwbml0K1FUQy9xL2ZT?= =?utf-8?B?WDQwS3VGSkRNbVdtREQ1ZlZzMWZEa1hvSWExM2lvN3V4SWwyTWFJNEpNTzBW?= =?utf-8?B?M3gwZXFDdmtkUit2ZjY2ZStudndJTFJlbkZHKzNrQW5qNjJQQkY1Vmwvc2th?= =?utf-8?B?QTV3b1FNZm1XU0huWTZ3M2ZoNWZZYk1ydlBkV24xUThVRDY3Nm83azdOUFdi?= =?utf-8?B?T0pQditRUTEvNnNCZUtmRE9DOU5sbitBTURjOEFtZyt1bVIrdC9lTndBNVBT?= =?utf-8?B?dGdHL2lId0RXcXRCNm9jbFE3Qm15b0pLMXNqeHNpcFdMWTF0VDJkaVVJUTRV?= =?utf-8?B?K2tQTGVCdkJka2Npa2ZPSXJTZHVHSWFEMWVUYjVsb3NRT3JWODh1K1pyVTh6?= =?utf-8?B?cDF0ZUxvSFFDdk9XZzJzeGhYWCtBck9FZHRoU21DMy9lRkpzeWNoQlB2S2J6?= =?utf-8?B?R2pXZDV3Mnc5M3JjR0sraWxTZUNQd1BQL3l0TjRoRFVaTDRQMElIUGxBdExx?= =?utf-8?B?bzUzM3N6WEwyd0NCS1BZbGNreGFZeE5kZThtRFk5SVcrZzk4eGNGSk1QYVh6?= =?utf-8?B?OWZNTHIwdnluMmV4ZWR1L2lOOHVZMTRrZi9oSndaRTJsbmxackd3Y1VUNmJm?= =?utf-8?B?NVhhc1pQeHYxK3hva2dTbXpsR0FUK1p4VnVQY0FpS1B0cW96eXZuNEtaRGk4?= =?utf-8?B?UlN2YVFjNGxDMXRkRHV3N1hvS1FoYXdHTTAyKzR1dVAya1VKeUpFSkVEY0tJ?= =?utf-8?B?WXpJL1VFd1lUN1ZacTZ1OG52Rk9yVnBxODZLL3RKUzRuODcwZHJKeXgra2hx?= =?utf-8?B?NjVQZ2FPdXlrdWxXZlVVeGFEdDNMczRaSzB0Rkc1bzFvVkVqMFoxbm1uZndn?= =?utf-8?B?cnlqdU5pOTdPTVArQ20velJSN2daTzV3ZStOdEUvT1FmUkhwamtPQT09?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 239e4249-1613-40ba-609a-08deb683968b X-MS-Exchange-CrossTenant-AuthSource: BN9PR12MB5259.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 May 2026 15:22:21.7011 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 13vr6To/YJcZ5j2mGm+ZmT5B/AyYJjB2ABSaI4YUoER8ctMrXGE4fM8IVuheXOJC8NTDi+IG59kPvxqa4N9L1Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB8498 On 5/11/2026 9:20 PM, David Hildenbrand (Arm) wrote: > On 4/28/26 17:50, Shivank Garg wrote: [...] >> +static bool migrate_offload_do_batch(int reason) >> +{ >> + if (!static_branch_unlikely(&migrate_offload_enabled)) >> + return false; >> + >> + switch (reason) { >> + case MR_COMPACTION: >> + case MR_SYSCALL: >> + case MR_DEMOTION: >> + case MR_NUMA_MISPLACED: >> + return true; >> + default: >> + return false; > > > What's the exact reason we don't do this for hotunplug etc? IOW, why do we make > this depend on a reason? Reason-based filtering could be a requirement for some users who want only specific use cases to go through DMA offload. For the RFC, I introduced a placeholder to enable further discussion on which use cases should allow migration offload and whether offload users actually need this control? Your other point also makes sense: "If someone migrates a handful of folios, latency is likely more important (and batching less beneficial)." Based on this, we could either fully rely on batch size. I'll think more about this. Thanks, Shivank