The patch titled Subject: mm/gup: local lru_add_drain() to avoid lru_add_drain_all() has been added to the -mm mm-new branch. Its filename is mm-gup-local-lru_add_drain-to-avoid-lru_add_drain_all.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: Hugh Dickins hughd@google.com Subject: mm/gup: local lru_add_drain() to avoid lru_add_drain_all() Date: Sun, 31 Aug 2025 02:08:26 -0700 (PDT)
In many cases, if collect_longterm_unpinnable_folios() does need to drain the LRU cache to release a reference, the cache in question is on this same CPU, and much more efficiently drained by a preliminary local lru_add_drain(), than the later cross-CPU lru_add_drain_all().
Marked for stable, to counter the increase in lru_add_drain_all()s from "mm/gup: check ref_count instead of lru before migration". Note for clean backports: can take 6.16 commit a03db236aebf ("gup: optimize longterm pin_user_pages() for large folio") first.
Link: https://lkml.kernel.org/r/165ccfdb-16b5-ac11-0d66-2984293590c8@google.com Signed-off-by: Hugh Dickins hughd@google.com Cc: stable@vger.kernel.org Cc: "Aneesh Kumar K.V" aneesh.kumar@kernel.org Cc: Axel Rasmussen axelrasmussen@google.com Cc: Chris Li chrisl@kernel.org Cc: Christoph Hellwig hch@infradead.org Cc: David Hildenbrand david@redhat.com Cc: Jason Gunthorpe jgg@ziepe.ca Cc: Johannes Weiner hannes@cmpxchg.org Cc: John Hubbard jhubbard@nvidia.com Cc: Keir Fraser keirf@google.com Cc: Konstantin Khlebnikov koct9i@gmail.com Cc: Li Zhe lizhe.67@bytedance.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Peter Xu peterx@redhat.com Cc: Shivank Garg shivankg@amd.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Wei Xu weixugc@google.com Cc: Will Deacon will@kernel.org Cc: yangge yangge1116@126.com Cc: Yuanchu Xie yuanchu@google.com Cc: Yu Zhao yuzhao@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/gup.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/mm/gup.c~mm-gup-local-lru_add_drain-to-avoid-lru_add_drain_all +++ a/mm/gup.c @@ -2291,6 +2291,8 @@ static unsigned long collect_longterm_un struct folio *folio; long i = 0;
+ lru_add_drain(); + for (folio = pofs_get_folio(pofs, i); folio; folio = pofs_next_folio(folio, pofs, &i)) {
_
Patches currently in -mm which might be from hughd@google.com are
mm-fix-folio_expected_ref_count-when-pg_private_2.patch mm-gup-check-ref_count-instead-of-lru-before-migration.patch mm-gup-local-lru_add_drain-to-avoid-lru_add_drain_all.patch mm-revert-mm-gup-clear-the-lru-flag-of-a-page-before-adding-to-lru-batch.patch mm-revert-mm-vmscanc-fix-oom-on-swap-stress-test.patch mm-folio_may_be_cached-unless-folio_test_large.patch mm-lru_add_drain_all-do-local-lru_add_drain-first.patch