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d=arm.com; s=foss; t=1779777413; bh=3ZneyL1b9DzWVg14gAhSJwF0kmIWkhbz/xMA8lPoVc8=; h=From:To:Cc:Subject:Date:From; b=aaxxDZZ00/6kTt9UJwFHNozi2DNKt5zjoYtENmmW0NNH65+WDLuWQ7zIAnjclLOlc G+La6zgUxuPjsq8Zl8sIB0j5rwanOYrSIU3aCHkXcuHgUfa3bq0x1tJL5oLiRmSPPG SLW406MAZdQI4a9MkA+0X+OOLa2UL3lgVgd58Yb0= From: Dev Jain To: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, chrisl@kernel.org, kasong@tencent.com, hughd@google.com, liam@infradead.org Cc: Dev Jain , riel@surriel.com, vbabka@kernel.org, harry@kernel.org, jannh@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, youngjun.park@lge.com, baolin.wang@linux.alibaba.com, pfalcato@suse.de, ryan.roberts@arm.com, anshuman.khandual@arm.com Subject: [PATCH v4 00/12] Optimize anonymous large folio unmapping Date: Tue, 26 May 2026 12:06:23 +0530 Message-Id: <20260526063635.61721-1-dev.jain@arm.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 19F801C0006 X-Rspamd-Server: rspam03 X-Stat-Signature: 5oe114s4yzoez9q8m4rcxjwi5twc8neu X-HE-Tag: 1779777413-422553 X-HE-Meta: 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 5S3x1vdT M5byMZJRdU86G6jWkSsogeE0CYRJXXpKeTOaH1nWK0vu93ceLjqmjo5OWzo+mbC/zu9x6t+30bpVs1ih7zDy+wdEfWL1428S44BH6MKQglbGWbTM5ZQQoJ8SPQM+UHKjxKPOtOO2D48xtYFUCVQszh1FjZUafa5GdKMB3GIP0r4QLoaMS7q7QUjxYVA== 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. --- Applies on mm-unstable (444fc9435e57). v3->v4: - Add patch 1 (page->folio conversion), patch 2 (add try_to_unmap_hugetlb_one), patch 6 and 11 (subpage -> page renaming), and patch 10 (refactoring anon unmap first) - Drop patch 1 of v3, which is now in mm-hotfixes - Patch 3: do set_ptes() restoration at call site - Patch 4: rename the function, move to memory.c, rename pte->ptep, pteval->pte - Patch 7,8: Remove redundant stub, add kerneldoc - Patch 9: remove helper, do a loop in-line v2->v3: Mostly a resend after merge window. Some minor changes: - Match kerneldoc parameter with function parameter (pte -> ptep) - Mention change BUG->WARN in patch description - Rename walk_done -> exit_walk in patch 2 - 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 (12): mm/rmap: convert page -> folio for hwpoison checks mm/rmap: Add try_to_unmap_hugetlb_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/swap: rename subpage->page in folio_dup_swap/folio_put_swap 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: refactor anon folio unmap in try_to_unmap_one mm/mprotect: drop 'sub' from page_anon_exclusive_sub_batch mm/rmap: enable batch unmapping of anonymous folios include/linux/mm.h | 4 + include/linux/mm_inline.h | 53 ----- include/linux/rmap.h | 52 +++-- mm/internal.h | 17 ++ mm/memory.c | 87 +++++-- mm/mprotect.c | 19 +- mm/rmap.c | 475 ++++++++++++++++++++++++-------------- mm/shmem.c | 8 +- mm/swap.h | 36 ++- mm/swapfile.c | 31 ++- 10 files changed, 470 insertions(+), 312 deletions(-) -- 2.34.1