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See http://www.infradead.org/rpr.html X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 6CED1180007 X-Stat-Signature: o3698m4ddh4r3muqmhddam9ijichh9wu X-HE-Tag: 1787719162-117221 X-HE-Meta: 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 SIAERbL3 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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.  Maybe we can go the extra step > > for > > that, as it would reduce the number of calls into gup significantly. > > > Which code are you referring to here? > > 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. > > Is there another performance critical path that goes > through the slower get_user_pages() path? The other callers of iov_iter_extract_bvecs matter more, but this is the main user. And iov_iter_extract_bvecs right now is very inefficient when used on larger folios, as each call to iov_iter_extract_bvecs and thus iov_iter_extract_pages and iov_iter_extract_user_pages can only fill in up to 256 pages. On x86 that is a single PMD mapped folio. Passing down the bio_vec array means that for PMD-mapped ranges we reduce the calls into pin_user_pages_fast by a factor of 256.