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Reed" Cc: James Houghton , Andrew Morton , linux-mm@kvack.org, Axel Rasmussen Subject: Re: PROBLEM: userfaultfd REGISTER minor mode on MAP_PRIVATE range fails Message-ID: References: <1757967196.153116687@apps.rackspace.com> <1757977128.137610687@apps.rackspace.com> <1758037938.96199037@apps.rackspace.com> MIME-Version: 1.0 In-Reply-To: <1758037938.96199037@apps.rackspace.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: GO4FVrkz4or8qYxFfHANEIM0fdnLGF-bD_nFzOJgPzA_1758039210 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 7ECE214000E X-Stat-Signature: 1dx7q1eapqhbj7isz97zmoz1wpoi5mhs X-HE-Tag: 1758039214-746245 X-HE-Meta: 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 d39acIdQ dFE6UFfFfcBKv7WmTdJ+0ePXfiLmd3Qr2f8GjhYXvUlJgrEA7v5Sc9pN9bYt6dcOGuWUFpNL7+Vz6lSt6shG1G2AYcY4mvaqXj0jSg9l14n8t9vUliUjqifEEfwXOhleAsw7bDqPwnCHXygrto5ECywYj/wz5M19YZxU+HkWSrDvicqF4szyg1BZ/7Wb87AqWohNsL+/WAIXBm/YBk+Gb94UMonass1D6XYc4IpgTARxzXeuNEMFVNN07Up/KlqEBedCFGeb5T8FQcAyL4xCl1pn6sqST14zvE5gGpdWWh/2uURT3Kn5WAMbWECtM0ZT18Ddc9adx7yLWonE2fR+oXOCHcK48U4ffDC7HqdX+e2FWIa3cca+2kk6i/ZrODThxx/HWU9f+ckOcFqLgXaTDpJdZCyqz1/NVCWHS X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Sep 16, 2025 at 11:52:18AM -0400, David P. Reed wrote: > synchronous would be better. But what I want to do is at least get > notifications of swapin events (including the case when the page is in > swap cache). Also, using UFFDIO_COPY can be useful for the swap in case > might make sense (but rarely, because there's no way to access the data > that was swapped out). Some more info on the use case might be helpful. I can start with some more questions if that helps. - If it's about page hotness / coldness, have you tried existing facilities (page idle, DAMON, etc.)? If so, why they won't work? - Assuming it's async reports that can be collected, what do you plan to do with the info? Do you care about swap outs prior to swap ins? - How sync events would be better in this case? Thanks, -- Peter Xu