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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.2 (3.60.2-1.fc44) MIME-Version: 1.0 X-Rspam-User: X-Stat-Signature: i3pedcsmwdh5pnhbw5zcbwjptg73bd5u X-Rspamd-Queue-Id: 2D22640002 X-Rspamd-Server: rspam06 X-HE-Tag: 1787751450-153519 X-HE-Meta: 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 qr8gG1aJ sKw2x+O6HaI5Z5Rov1zYw1GPAViX4xQa3xwAo6FvhSPMYjxVgw+V1xoL/HPEhe8Frt25uEU4gjjMK1vOubjGlOQHqP3VVfLX9ZOtraDzxV15dXxrSRH/TbL2f71FxfufL5yODG1UNGTi2wCZcGCWO+pnLYHc7w1q3CWk3fa2w12QdHIc3+SAadxZ2ciZEBU0OD9gPwW1lO8MvXuQ5EIel4PZvMY4sl1NCdbvFwRJJZ6y2hr/gBm87k+m0B7PT0UTsJcA+3iRZpcsMNuNLopM5JCSXiF3osmmLfGlCZXN0+1uSQw8QPVn8QF86Y+K15qpH/tuH Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 2026-08-25 at 21:39 -0700, Christoph Hellwig wrote: > On Tue, Aug 25, 2026 at 09:37:09AM -0400, Rik van Riel wrote: > > > And what many including the most performance critical callers > > > want > > > instead is really a single bio_vec.=C2=A0 Maybe we can go the extra > > > step > > > for > > > that, as it would reduce the number of calls into gup > > > significantly. > > >=20 > > Which code are you referring to here? > >=20 > > blk_rq_map_user() seems to end up calling pin_user_pages_fast(), > > via iov_iter_extract_user_pages, and it directly fills in the > > bio_vec's pages array. > >=20 > > Is there another performance critical path that goes > > through the slower get_user_pages() path? >=20 > The other callers of iov_iter_extract_bvecs matter more, but this is > the main user. >=20 > And iov_iter_extract_bvecs right now is very inefficient when used > on larger folios, I think it would be possible to create a path into follow_page_mask() that passes a bio_vec, and where we fill in the bio_vec fields the same way bvec_set_page() does. Then iov_iter_extract_bvecs would no longer need to iterate over the pages returned by get_user_pages_fast. That seems like a follow-up series though, and we need to think carefully about whether we would also want to unify part of the=C2=A0 gup_fast and gup code. Currently the gup code depends on locking to keep page tables from going away, while the gup_fast code depends on disabling irqs. --=20 All Rights Reversed.