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Fri, 10 Apr 2026 11:06:24 -0400 (EDT) Date: Fri, 10 Apr 2026 11:06:23 -0400 From: Andres Freund To: Zi Yan Cc: "Matthew Wilcox (Oracle)" , Song Liu , Chris Mason , David Sterba , Alexander Viro , Christian Brauner , Jan Kara , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v1 05/10] mm/huge_memory: remove READ_ONLY_THP_FOR_FS from file_thp_enabled() Message-ID: References: <20260327014255.2058916-1-ziy@nvidia.com> <20260327014255.2058916-6-ziy@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260327014255.2058916-6-ziy@nvidia.com> X-Rspamd-Queue-Id: D39ED4001C X-Stat-Signature: oj4eu7i39aqa57x8xyw16setxwapkcrx X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1775833586-876098 X-HE-Meta: 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 z51KxUhR Zhw+DtuzG76aeu4PG2f/sCb6VnxJ2caxtsHDdo/FPdptURRYhoBs+GRENFe5Cdomn+1vsv5ZmvKAyDnLJF0y54ZUU6+DvB1aIBN2Gkv4CPo/2t5/pkuHCff0r3I0GuNq6bHn0aBbSBhOmwzqVqSYo/zW4snN4lfFnQcceWbJanNiH4dI/po0lL5uye6TutBtysIlSINK9l+dpDCRPz9MRkVPhQsrYk1hTWBCSDWeMEuaLZoGO87396XbtCf3png08KPg89GjZWbylfYV1e0IHc2CaZnLaPRzEm3B8EsP8EdXOlVYzuP8wer5k1sNddV/BPFhnA9FEwXZ8i4FPFo1hz9h/OYk51YnEkRRTf3DdXmlg/8rS7e3RkQv2jvjWhHaL/eVC0t5+tefhSBNIbrVrxF7yT0GWunaQaygxC4v6muZ98dZvluokcWuTVMD2E4ed2p0Ec0VCeRDcyH6FXIa+dG9ZPg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi, On 2026-03-26 21:42:50 -0400, Zi Yan wrote: > Replace it with a check on the max folio order of the file's address space > mapping, making sure PMD_ORDER is supported. Question from a user space developer (who learned of this via LWN [1]): Right now MADV_COlLAPSE on file mappings appears to only only work with CONFIG_READ_ONLY_THP_FOR_FS. That's pretty sad, because I see quite consistent gains (~15%) from doing madvise(MADV_COLLAPSE) on e.g. postgres' .text - but because CONFIG_READ_ONLY_THP_FOR_FS is not enabled default (or at least not commonly, I think?) in distro kernels, it never quite seemed worth the fiddliness. Do I understand correctly that by replacing the check here (and the predecessor commits), madvise(MADV_COLLAPSE) on file mappings might actually start working in more situations on typical distro kernels? Greetings, Andres [1] https://lwn.net/SubscriberLink/1066582/b92de1d7595a01e4/