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order-0 folios To: Andrew Morton Cc: David Hildenbrand , Jason Gunthorpe , Peter Xu , Mike Rapoport , LKML , linux-mm@kvack.org, Sourab Gupta References: <20260409014647.397515-1-jhubbard@nvidia.com> <20260408190745.40f0c0231a475e697c970fd4@linux-foundation.org> Content-Language: en-US From: John Hubbard In-Reply-To: <20260408190745.40f0c0231a475e697c970fd4@linux-foundation.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SJ0PR05CA0192.namprd05.prod.outlook.com (2603:10b6:a03:330::17) To DM3PR12MB9416.namprd12.prod.outlook.com (2603:10b6:0:4b::8) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM3PR12MB9416:EE_|SJ2PR12MB8847:EE_ X-MS-Office365-Filtering-Correlation-Id: 7359dc66-d150-4d46-1272-08de95dd0c2d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|366016|18002099003|56012099003|22082099003; X-Microsoft-Antispam-Message-Info: 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U1S603tsIpRK1gLs0FXk+k3PKt7t0JCNqwKpC1g//mDvYtYAfGNYbfp38lOPzTrHEQS0o8D0uOc3A8TyngQudD7v1Lx5m1HUaqdz+d+9ymvUumwaeSOKtGakMb6FOLXVMGo18t6dOLbShWkOqM8VUM8HLuDFfTD1U0wlpxhFew4EJOfLe+PmfY8hkEHvN+lD8ugzBtRP4xlbqE39FdvLUp5phQ3aoPr6R0iJiPOoc01R/Ct+/os1SwRND81RZgi+bP8fsHR2mE1SzR0QWowKYIxhRwOxLXF0K76mRfIvp0umKCkuh9JQoDjQ7UWkAKYVSsfjT1KCQn5Gl82qZ7lrDEO59l2sftvjrOfI06JCi1x1JgcoLJg9s9EYitrMUB/wwqZaSu9E6UCsSxEoS2Q6PQ/ZyG2huWkrGVwT0lo7mFYVBOlNJAHvU4LrfVg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/8/26 7:07 PM, Andrew Morton wrote: > On Wed, 8 Apr 2026 18:46:47 -0700 John Hubbard wrote: > >> Since commit f002882ca369 ("mm: merge folio_is_secretmem() and >> folio_fast_pin_allowed() into gup_fast_folio_allowed()"), >> gup_fast_folio_allowed() falls back to the slow path for any order-0 >> folio with a NULL mapping when CONFIG_SECRETMEM=y. This causes a >> performance regression for drivers that allocate pages with alloc_page() >> and insert them into VMAs via vm_insert_page(). These pages legitimately >> have a NULL folio->mapping, but they cannot be secretmem pages. > > How significant is the slowdown? About 2x! Sourab has a bunch of peer to peer IO cases that use 4K pages, that he ran. thanks, -- John Hubbard