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Mon, 13 Apr 2026 08:46:42 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 3htaC3Kt3Gn8IQAAD6G6ig (envelope-from ); Mon, 13 Apr 2026 08:46:42 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id E5C64A0AFF; Mon, 13 Apr 2026 10:46:37 +0200 (CEST) Date: Mon, 13 Apr 2026 10:46:37 +0200 From: Jan Kara To: Andres Freund Cc: Zi Yan , "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: <2hwc3ixfwvpnaazsm7y2vgrdh5em4fosxdcs2lhszcsn7mlcca@u3c5czxxcatv> 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: X-Rspamd-Action: no action X-Rspamd-Queue-Id: E71D5180002 X-Stat-Signature: k17mygh9srbn535hp79wfbtyte4c334d X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1776070003-32287 X-HE-Meta: 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 JWO96kKK Dd8pFzurFfwOOEzLacT+y1bZ5r7FLH8x+8Fva1LUtdfjETe7iBZ38utkyc9yk9bXYna6t/LQE34E9lZLid1ue9JBJpdcOMLD/Tg6y+APibN9gbhZvK5/Ngar+ZZEb5JNrAZg0f9ykB1/jPNYVWTBhoVO4gKJVh6SrroeM9xWziN4SORu2gSmH0pVu4aRY/6ONvUi4+hVnrgkyB1ThsjJPhz0Bqm5kWghBx8eE5IpMzpg1nI8gVVLatD/ddWGq1+0AKwO74i4i0KikRcesvoqt2zjBNobr4iZ5FDkmMoIr/rUgUVVtx9h86LUm939i4emstIssDqRzfYks2gAmM/o3btVLiJiDAw2z2cin4TwwBARb9h8IMWfEizPp4rH+WS8dEDAHtVQHyssSj102cTXfQHILQlvJJjZOx7Aw Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri 10-04-26 11:06:23, Andres Freund wrote: > 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? FWIW we soon might be creating PMD sized folios for executable VMAs by default [1] (at least for archs with 4k page size). So there'd be no need for explicit MADV_COLLAPSE to get the gain. Honza [1] https://lore.kernel.org/all/20260402181326.3107102-3-usama.arif@linux.dev/ -- Jan Kara SUSE Labs, CR