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mm/gup: local lru_add_drain() to avoid lru_add_drain_all()

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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 a03db236ae ("gup: optimize longterm
pin_user_pages() for large folio") first.

Link: https://lkml.kernel.org/r/66f2751f-283e-816d-9530-765db7edc465@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: David Hildenbrand <david@redhat.com>
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: 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: Rik van Riel <riel@surriel.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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Hugh Dickins
2025-09-08 15:16:53 -07:00
committed by Andrew Morton
parent 98c6d25931
commit a09a8a1fbb
1 changed files with 11 additions and 4 deletions
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15
mm/gup.c
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@@ -2287,8 +2287,8 @@ static unsigned long collect_longterm_unpinnable_folios(
struct pages_or_folios *pofs) struct pages_or_folios *pofs)
{ {
unsigned long collected = 0; unsigned long collected = 0;
bool drain_allow = true;
struct folio *folio; struct folio *folio;
int drained = 0;
long i = 0; long i = 0;
for (folio = pofs_get_folio(pofs, i); folio; for (folio = pofs_get_folio(pofs, i); folio;
@@ -2307,10 +2307,17 @@ static unsigned long collect_longterm_unpinnable_folios(
continue; continue;
} }
if (drain_allow && folio_ref_count(folio) != if (drained == 0 &&
folio_expected_ref_count(folio) + 1) { folio_ref_count(folio) !=
folio_expected_ref_count(folio) + 1) {
lru_add_drain();
drained = 1;
}
if (drained == 1 &&
folio_ref_count(folio) !=
folio_expected_ref_count(folio) + 1) {
lru_add_drain_all(); lru_add_drain_all();
drain_allow = false; drained = 2;
} }
if (!folio_isolate_lru(folio)) if (!folio_isolate_lru(folio))