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Tue, 23 Dec 2025 13:48:52 +0800 From: Baolin Wang To: akpm@linux-foundation.org, david@kernel.org, catalin.marinas@arm.com, will@kernel.org Cc: lorenzo.stoakes@oracle.com, ryan.roberts@arm.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, riel@surriel.com, harry.yoo@oracle.com, jannh@google.com, willy@infradead.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 5/5] mm: rmap: support batched unmapping for file large folios Date: Tue, 23 Dec 2025 13:48:39 +0800 Message-ID: X-Mailer: git-send-email 2.43.7 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: E4DB220004 X-Stat-Signature: 4551b3enzb7kgju1ruqq4yw59d6nkcyj X-Rspam-User: X-HE-Tag: 1766468936-532621 X-HE-Meta: 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 wEaz74IB h6ADEUYC17mfKYZzE4QeJOYbO2v/eYbLQ6En/o7BupydwnQGse3kmdc2HSCYcTwhcbGApgUmM/370W63PPGnFXJsR6oo2bII3AYdRd9kP4b78+QJ4ryUPTPerAyPv644yPizFy0sMzqwOOCK6YHjZKzDa1iQLT59/w7mxVHzMCXInv+JLsU1EVgyPnKZO1k0IstHEf/0UHmNqkjboJqjEepIVfvc8JDarjZkcQZitV9swfRX1Gyzeoide2RVZp67v5ymIH8ZPWJIpj4D+iQqR7QSa9LFPtbi4BuhzPEjAL8/FiwQ= 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: Similar to folio_referenced_one(), we can apply batched unmapping for file large folios to optimize the performance of file folios reclamation. Barry previously implemented batched unmapping for lazyfree anonymous large folios[1] and did not further optimize anonymous large folios or file-backed large folios at that stage. As for file-backed large folios, the batched unmapping support is relatively straightforward, as we only need to clear the consecutive (present) PTE entries for file-backed large folios. Performance testing: Allocate 10G clean file-backed folios by mmap() in a memory cgroup, and try to reclaim 8G file-backed folios via the memory.reclaim interface. I can observe 75% performance improvement on my Arm64 32-core server (and 50%+ improvement on my X86 machine) with this patch. W/o patch: real 0m1.018s user 0m0.000s sys 0m1.018s W/ patch: real 0m0.249s user 0m0.000s sys 0m0.249s [1] https://lore.kernel.org/all/20250214093015.51024-4-21cnbao@gmail.com/T/#u Acked-by: Barry Song Signed-off-by: Baolin Wang --- mm/rmap.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index a0fc05f5966f..7482121d4e92 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1862,9 +1862,10 @@ static inline unsigned int folio_unmap_pte_batch(struct folio *folio, end_addr = pmd_addr_end(addr, vma->vm_end); max_nr = (end_addr - addr) >> PAGE_SHIFT; - /* We only support lazyfree batching for now ... */ - if (!folio_test_anon(folio) || folio_test_swapbacked(folio)) + /* We only support lazyfree or file folios batching for now ... */ + if (folio_test_anon(folio) && folio_test_swapbacked(folio)) return 1; + if (pte_unused(pte)) return 1; @@ -2230,7 +2231,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, * * See Documentation/mm/mmu_notifier.rst */ - dec_mm_counter(mm, mm_counter_file(folio)); + add_mm_counter(mm, mm_counter_file(folio), -nr_pages); } discard: if (unlikely(folio_test_hugetlb(folio))) { -- 2.47.3