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h=From:To:Cc:Subject:Date:From; b=pkFuTB7dmikw7C91cqH3pZT3et/jndvNGFkXwF82k3d2lpxoReaf8RrkaOXz06RXH +csyYlIM6hzOU275rNwE1F+Hk/tEBkV70U4LvEaabPrhqc8I2YmmfKv/nSQEKLBhhB iHbQS2T6PPBLBTYD/9GIgWVoABqCTw068zjTTznE= From: Dev Jain To: akpm@linux-foundation.org, david@kernel.org, hughd@google.com, chrisl@kernel.org Cc: ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, kasong@tencent.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, riel@surriel.com, harry@kernel.org, jannh@google.com, pfalcato@suse.de, baolin.wang@linux.alibaba.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, youngjun.park@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, Dev Jain Subject: [PATCH v2 0/9] Optimize anonymous large folio unmapping Date: Fri, 10 Apr 2026 16:01:55 +0530 Message-Id: <20260410103204.120409-1-dev.jain@arm.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 01B792000B X-Stat-Signature: wfa3i3bdrehhfqtcb9qzac1n7eek9dtj X-Rspam-User: X-HE-Tag: 1775817141-244345 X-HE-Meta: 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 dX6vT4e1 9VHjPTWpD2v1jvEmAn2+9iulI3c9UnJ3t1FjeDsWEQkQkhLVMwm3Smm2F3q1uOaRo5MztSb+lEcY/t7voFtN+m9Y/IyDZZYlX49YW4DosBgQknFoVgMupBN8vl7c33np6OQK4YVRjYOPm3k9qXKlfI2bCjFkhWnG/yDe/XW9AoKfjlht3t0jRRtwQtQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Speed up unmapping of anonymous large folios by clearing the ptes, and setting swap ptes, in one go. The following benchmark (stolen from Barry at [1]) is used to measure the time taken to swapout 256M worth of memory backed by 64K large folios: #define _GNU_SOURCE #include #include #include #include #include #include #include #define SIZE_MB 256 #define SIZE_BYTES (SIZE_MB * 1024 * 1024) int main() { void *addr = mmap(NULL, SIZE_BYTES, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (addr == MAP_FAILED) { perror("mmap failed"); return 1; } memset(addr, 0, SIZE_BYTES); struct timespec start, end; clock_gettime(CLOCK_MONOTONIC, &start); if (madvise(addr, SIZE_BYTES, MADV_PAGEOUT) != 0) { perror("madvise(MADV_PAGEOUT) failed"); munmap(addr, SIZE_BYTES); return 1; } clock_gettime(CLOCK_MONOTONIC, &end); long duration_ns = (end.tv_sec - start.tv_sec) * 1e9 + (end.tv_nsec - start.tv_nsec); printf("madvise(MADV_PAGEOUT) took %ld ns (%.3f ms)\n", duration_ns, duration_ns / 1e6); munmap(addr, SIZE_BYTES); return 0; } Performance as measured on a Linux VM on Apple M3 (arm64): Vanilla - Mean: 37401913 ns, std dev: 12% Patched - Mean: 17420282 ns, std dev: 11% No regression observed on 4K folios. Performance as measured on bare metal x86: Vanilla - mean: 54986286 ns, std dev: 1.5% Patched - mean: 51930795 ns, std dev: 3% Interestingly, no obvious improvement is observed on x86, hinting that the benefit lies mainly in the reduction of ptep_get() calls and the reduction of TLB flushes during contpte-unfolding, on arm64. No regression is observed on 4K folios on x86 too. --- Based on mm-unstable 3fa44141e0bb ("ksm: optimize rmap_walk_ksm by passing a suitable address range"). mm-selftests pass. v1->v2: - Keep nr_pages as unsigned long - Add patch 2 - Rename some functions, make return type bool for functions returning 0/1 - Drop page_vma_mapped_walk_jump - this is implicitly handled - Drop likely() - Add folio_dup/put_swap_pages, do subpage -> page - Shorten the kerneldoc to remove unnecessary information - keep it aligned with analogous functions - Put clear_pages_anon_exclusive to mm.h - Some more refactoring in last patch with finish_folio_unmap Dev Jain (9): mm/rmap: initialize nr_pages to 1 at loop start in try_to_unmap_one mm/rmap: refactor hugetlb pte clearing in try_to_unmap_one mm/rmap: refactor some code around lazyfree folio unmapping mm/memory: Batch set uffd-wp markers during zapping mm/rmap: batch unmap folios belonging to uffd-wp VMAs mm/swapfile: Add batched version of folio_dup_swap mm/swapfile: Add batched version of folio_put_swap mm/rmap: Add batched version of folio_try_share_anon_rmap_pte mm/rmap: enable batch unmapping of anonymous folios include/linux/mm.h | 11 ++ include/linux/mm_inline.h | 32 +-- include/linux/rmap.h | 27 ++- mm/internal.h | 26 +++ mm/memory.c | 26 +-- mm/mprotect.c | 17 -- mm/rmap.c | 404 +++++++++++++++++++++++--------------- mm/shmem.c | 8 +- mm/swap.h | 23 ++- mm/swapfile.c | 42 ++-- 10 files changed, 380 insertions(+), 236 deletions(-) -- 2.34.1