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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: [RFC PATCH 02/11] mm/khugepaged: remove READ_ONLY_THP_FOR_FS code in collapse_file() Message-ID: References: <20260323190644.1714379-1-ziy@nvidia.com> <20260323190644.1714379-3-ziy@nvidia.com> <7382046f-7c58-4a3e-ab34-b2704355b7d5@kernel.org> <71148f2e-cceb-418e-b762-c8dbd7a7eb1f@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 19BBF180011 X-Stat-Signature: jdu1m5w41tiypqwj5gre71sr58cyp6aw X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1774299770-277859 X-HE-Meta: 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 CbqqcVDA pzqMovUwp8rp+dbSCzf+QakCSfEHi9DkHjinY4NPWBwOg1uD5zyDs/4WdQbEH9dbMGtgI2xJ3kSI19Ms8WFA+yd8R3NZ8jqvlCCb0moTvjEPWBvoQIhZk0s1JU3ulwzVsCfBgmzg+i55SpWqu/MKxH9rralsmV6zpNC7dRstrcZ2rzmLJrpmZ4zT5dggACbCYvL7rUDtsR+X7yxXBPnsWndMzk1ri9GMGZtFfMPS+QMfhrOljFl86AxbzpCx0j5WjpfzZtCgcQSCwqM7wrXXYcsxWV+Ni43+lvF1TLfGsZ4pd3dg= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 23, 2026 at 04:24:26PM -0400, Zi Yan wrote: > On 23 Mar 2026, at 16:13, David Hildenbrand (Arm) wrote: > > I assume so, because for executables you would have to be lucky to get a > > PMD THP? So I don't see the non-khugepaged large folio support on par > > with khugepaged support. Not necessarily that lucky; if you set VM_HUGEPAGE, do_sync_mmap_readahead() will allocate PMD-sized folios automatically. On busy database servers (and is there any other kind?), khugepaged takes too long to run and find opportunities to collapse text pages. Like, days. > It is more like turning on READ_ONLY_THP_FOR_FS by default for > FS with large folio support instead of removing it. > > OK, I will give it another try. I think the test needs to be: if (mapping_max_folio_order(mapping) >= PMD_ORDER) as there can be cases of filesystems which support up to, say, 64KiB, but not all the way up to 2MiB. I disapprove of this situation, but this is where we are right now.