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Wed, 3 Apr 2024 04:40:51 -0700 (PDT) From: Ryan Roberts To: Andrew Morton , David Hildenbrand , Matthew Wilcox , Huang Ying , Gao Xiang , Yu Zhao , Yang Shi , Michal Hocko , Kefeng Wang , Barry Song <21cnbao@gmail.com>, Chris Li , Lance Yang Cc: Ryan Roberts , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Barry Song Subject: [PATCH v6 5/6] mm: vmscan: Avoid split during shrink_folio_list() Date: Wed, 3 Apr 2024 12:40:31 +0100 Message-Id: <20240403114032.1162100-6-ryan.roberts@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20240403114032.1162100-1-ryan.roberts@arm.com> References: <20240403114032.1162100-1-ryan.roberts@arm.com> MIME-Version: 1.0 X-Rspamd-Queue-Id: 030E4100007 X-Rspam-User: X-Stat-Signature: nbp4ockmx4craz5enuxxk9o7cykzzo1g X-Rspamd-Server: rspam01 X-HE-Tag: 1712144453-959092 X-HE-Meta: U2FsdGVkX19l1D+OBtPyOUtWu8HfaFsqfFL2wBYpQvGHJGJwYW/KW3Zs7jw9DuhYBMZDWSGvfhtdWo04XPIiDMs7tBNoaqRZKda46WX0+6tDsAMW6siDNk026fgP6MOOfSpVidaO7c2BuhUhflCKnocqzKWZTACpEhG7dn8+exjU6x866vnTVoqqHAQq5XmT9F7P9p5DOdbTtKmBmHgHdCIZemZVfniB0rhbXYquqH9pbwpEYrmfEThhiaTKIBw95NpqxaTUsYJCg6wgOtRGRGNClG4J1H7Kb1fxacFJely7/kdAyKwm5n/Y55jD7pLU9eaTU/HldVGbBHbi0TUv1yq9I3zK0kh9zTe4My793X1nT0epVsfj9qiZzuPGyEhO4RV4qEBmGnUMRfKLcFUVFS/XHyHWRJkTFwUKj8m0yXQeqtMfftPuEofDGPQIKuXWiu8u4nULX4YkU3U5VI7dXXq+xWtcOvfwUJFvLvxJk1lCF2A7hKY/1Tf9rTKS6nvlwr8gQAWBnmy3VDIRlifUHr0HeAuYwdCWn1lh6D9HFKyTo0009KaO99YX3uOr+qM6MjC8zceuQvcm6TF7dFyVkkE6/eLj0tkiHnOuM/FeoEe800XLBCBhAuXlFPBm39xKdbqwza6ykl4Mk0fvRt0XsGZwrRTkkU/NqDizu+/EqhdEwWeRb7wXI3F9C4DZNO6lTYY4DOQRw4w7nd5gOYXRnfxTHp1yBngmM6BjBL7t35akE3CjNOC6s17wBTq+RAdkQML1q9EOqm6JaEgTg8qXGVNljUMhQXaAqv+5SFDQitW8Ej6q8owMbuHilSSaocAUfT4G0Ma9oV0S+SaA6kz9yFEAzTthyumA43XdUEbv7Oq8+zBdAqj2c7HDCXxVSoIT18VB4Z6PsKWiaHGXS2BzNwpv5UfceCjPVJwfbAERJd/VJ3VlE1bIDAJ9E+NthSTnSmF1jFzSz6bNVB/T4kI Br2Z3hS/ tDISosoDJ9+PBg2TmUI1KtRRFiR2/phCwB9NDl32WrxBvcRqXuDlSgTyaeWUKMbK+01CKfQf2SZZaSGF0sy2AhEMJpyCKRBr0Pi869vz6gXQETxPnejecwe74NZ+LpqNQXCTmCWbMWYG0DZOTqRX7BGauG3H10rFnFzupHFeK5hTkDe5BOMphmQVxPFqQzHy56DqblKIgKIfNFsuR2mQOcRcf+FwhjQpQMMB4N3YSX8As3cYaY1lNFLlHlHQf94YyGVPBXf94A0n1kdL/mHWdg6VhT/6w9xbocXwW 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: Now that swap supports storing all mTHP sizes, avoid splitting large folios before swap-out. This benefits performance of the swap-out path by eliding split_folio_to_list(), which is expensive, and also sets us up for swapping in large folios in a future series. If the folio is partially mapped, we continue to split it since we want to avoid the extra IO overhead and storage of writing out pages uneccessarily. THP_SWPOUT and THP_SWPOUT_FALLBACK counters should continue to count events only for PMD-mappable folios to avoid user confusion. THP_SWPOUT already has the appropriate guard. Add a guard for THP_SWPOUT_FALLBACK. It may be appropriate to add per-size counters in future. Reviewed-by: David Hildenbrand Reviewed-by: Barry Song Signed-off-by: Ryan Roberts --- mm/vmscan.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 00adaf1cb2c3..ffc4553c8615 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1223,11 +1223,12 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, if (!can_split_folio(folio, NULL)) goto activate_locked; /* - * Split folios without a PMD map right - * away. Chances are some or all of the - * tail pages can be freed without IO. + * Split partially mapped folios right + * away. We can free the unmapped pages + * without IO. */ - if (!folio_entire_mapcount(folio) && + if (data_race(!list_empty( + &folio->_deferred_list)) && split_folio_to_list(folio, folio_list)) goto activate_locked; @@ -1240,8 +1241,12 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, folio_list)) goto activate_locked; #ifdef CONFIG_TRANSPARENT_HUGEPAGE - count_memcg_folio_events(folio, THP_SWPOUT_FALLBACK, 1); - count_vm_event(THP_SWPOUT_FALLBACK); + if (nr_pages >= HPAGE_PMD_NR) { + count_memcg_folio_events(folio, + THP_SWPOUT_FALLBACK, 1); + count_vm_event( + THP_SWPOUT_FALLBACK); + } #endif if (!add_to_swap(folio)) goto activate_locked_split;