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dkim=none (message not signed) header.d=none;namei.org; dmarc=none action=none header.from=oracle.com; Received: from BYAPR10MB3077.namprd10.prod.outlook.com (2603:10b6:a03:8c::12) by BYAPR10MB3208.namprd10.prod.outlook.com (2603:10b6:a03:159::10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3805.17; Wed, 3 Feb 2021 16:13:32 +0000 Received: from BYAPR10MB3077.namprd10.prod.outlook.com ([fe80::74a8:8649:e20b:d571]) by BYAPR10MB3077.namprd10.prod.outlook.com ([fe80::74a8:8649:e20b:d571%7]) with mapi id 15.20.3805.024; Wed, 3 Feb 2021 16:13:32 +0000 Subject: Re: [PATCH v8 02/14] mm/gup: check every subpage of a compound page during isolation To: Jason Gunthorpe Cc: Pavel Tatashin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, vbabka@suse.cz, mhocko@suse.com, david@redhat.com, osalvador@suse.de, dan.j.williams@intel.com, sashal@kernel.org, tyhicks@linux.microsoft.com, iamjoonsoo.kim@lge.com, mike.kravetz@oracle.com, rostedt@goodmis.org, mingo@redhat.com, peterz@infradead.org, mgorman@suse.de, willy@infradead.org, rientjes@google.com, jhubbard@nvidia.com, linux-doc@vger.kernel.org, ira.weiny@intel.com, linux-kselftest@vger.kernel.org, jmorris@namei.org References: <20210125194751.1275316-1-pasha.tatashin@soleen.com> <20210125194751.1275316-3-pasha.tatashin@soleen.com> <05a66361-214c-2afe-22e4-12862ea1e4e2@oracle.com> <20210203145313.GQ4718@ziepe.ca> From: Joao Martins Message-ID: Date: Wed, 3 Feb 2021 16:13:21 +0000 In-Reply-To: <20210203145313.GQ4718@ziepe.ca> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?ckNCSlVEOEdYd2tiMWtlQWcvNHAxaUFMOXBtR3BCM004U0pYVEplcWZLK3Jk?= =?utf-8?B?MUtOeWtSUnVYZWFra01lbituUVpYZVllWUhzTzA5RVJwNm81MkVDdUh5QXJv?= =?utf-8?B?TlJtV2o4N1ZEQ0FzbUlpVUJ2L3JMWVl4aVJEcVo5WVMyZDdsZEhlZXNNaFpF?= =?utf-8?B?Yit0ZVMzR2lpWXovOEhmTEtPQ1pWTnFEMFcvRFZxQ1lqZENSUXBHNXI4RWJU?= =?utf-8?B?UU1Jd3NXc3EvVi85OExnYmFqSzRLdStEUTJjM0dHRVBMdjBxQXVvNC9IdkMx?= =?utf-8?B?STJ6RzhhcXdiN3YxRnpyN1ZpdWVGRTloc2FzSE1CUVdnTHRISDNBY1lITzdJ?= =?utf-8?B?dlI2RzI3aVBLU1RBYWhsUFJzcDQrK0s0Z21DV20yTkFVR3AyaFVlRWpHUXls?= =?utf-8?B?elR5SXRxKzA2Y3FTK2JFS3J5TFpLRkFhMWptd0VaVlRnSk5pbEwvVnNZOU9N?= =?utf-8?B?N2JsenRkOXVFRXZxSUhERzNZbld6dWRUTm1aY2k5SlE1bHBNQ3l3d0gzZ2Vv?= =?utf-8?B?YnBqamVndWo5ZmVSSUdiYm5LUktNT1k1dUxla2xIVFMzS3R5VWswVkd5TFk0?= =?utf-8?B?N3NUUW5GcFhJWXE1S2tiam9WSFRNZE9KcnJvbFdGR0tBVlRTLzRTNStlczJx?= =?utf-8?B?MG1tZGZzQ0dKeTQvYkdISmcyWkV4QmJQQXhKaDVtL011YTBlZ1JOK290NHNX?= =?utf-8?B?NEZKZmNmYXFyS1IzODU1bHFOS0M0QjBGalFpRU1tZkd1VGdleGNCSDJRZ1hH?= =?utf-8?B?ZG40bkV5NlRlYzhiV21oSlZFVmxIOFhmSTVtR2tSMHVKVEhzdkRRS1g1TXVi?= =?utf-8?B?YWJySEIrQWFkQWMzaUV1bDUwODdLY3c0K3paeDF6d2lOd05jOU1admlHZGxT?= =?utf-8?B?SUNsUm1qbGdoU3FUZjlrQ3JSOEtBb3U2b256Q3NrUWZnSU93V05TNThHaG53?= =?utf-8?B?YTNTalRsQ3djZUtIL0dxMXA2c1ViRURRQmgvV2laaXI1c1V3UFliUDYyNk9k?= =?utf-8?B?U0M4bXlNUXRWd3dmdHVlYllmcC9Wczd4RjJ4QWpIczAxb29zNmViYWVIR1Qz?= =?utf-8?B?VWFxbHRGbTdSN3pwdkZkTmJVeHE2eXhJMkZHbGQwTmpoU1R4N2Zobkl2bVB6?= =?utf-8?B?KzE3RnhWT085WjZYa1ZPSG9tbjNBMnkxQWMvdTZCU3c4aXQvZ28wK3lDNjd5?= =?utf-8?B?S1BFbXBjUkFjdm9CSmhGRTBZOTFNTm5LVkpvc3NUb0lxMlk4Q2J5QXlNZnds?= =?utf-8?B?T0QrdmQzendsdzZad1huc01CRjdyckljcTN1eEZVbnlDMENrV3dmakF2cEdq?= =?utf-8?B?dHowZXFDRjkzcDUxVndRa25VNytPV2xsU0xCZkxJTUpHZWVkcTdSdkR5ZW85?= =?utf-8?B?OGxqalhscG1pbG9hSm5VNzE3TVpCVWduQk1YbjB1b0xoZnNLdGNZa3EzQjMy?= =?utf-8?Q?Ulx9b70a?= X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-Network-Message-Id: 153a5354-e1cb-40b7-62d1-08d8c85ea6de X-MS-Exchange-CrossTenant-AuthSource: BYAPR10MB3077.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Feb 2021 16:13:32.6897 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: EeDX0ckS/1FV6dlu/TqIYBaww4+qVH63A/hR7KniF10h9SCdESH+E1DvKHHneCPrL6alnrFZjROZcKO9osmxEWhGz82VUyUFeBWCLqAgXxw= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR10MB3208 X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9884 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 mlxscore=0 suspectscore=0 spamscore=0 mlxlogscore=999 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102030098 X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9884 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 adultscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 clxscore=1015 spamscore=0 lowpriorityscore=0 phishscore=0 mlxlogscore=999 mlxscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102030098 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/3/21 2:53 PM, Jason Gunthorpe wrote: > On Wed, Feb 03, 2021 at 01:22:18PM +0000, Joao Martins wrote: > >> With this, longterm gup will 'regress' for hugetlbfs e.g. from ~6k -> ~32k usecs when >> pinning a 16G hugetlb file. > > Yes, but correctness demands it. > Hence the quotes around the word regress. But still, we are adding unnecessary overhead (previously nonexistent) to compound pages even those where the issue doesn't exist (hugetlb). > The solution is to track these pages as we discover them so we know if > a PMD/PUD points and can directly skip the duplicated work > That looks better. It would require moving check_and_migrate_movable_pages() elsewhere, and/or possibly reworking the entire series? >> Splitting can only occur on THP right? If so, perhaps we could >> retain the @step increment for compound pages but when >> !is_transparent_hugepage(head) or just PageHuge(head) like: > > Honestly I'd rather see it fixed properly which will give even bigger > performance gains - avoiding the entire rescan of the page list will > be a win > If check_and_migrate_movable_pages() is meant to migrate unpinned pages, then rather than pinning+unpinning+moving, perhaps it would be called in __get_user_pages() place where we are walking page tables and know if it's a PUD/PMD and can skip all the subpages and just record and migrate those instead. Was that your thinking? Joao