From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 6C70D3E3C4E for ; Wed, 6 May 2026 09:45:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778060727; cv=none; b=mj7C+ikjGFIu+ZilmDJD2woL2iQU5LYbKjzW3AsXUKzTYOwvJTRTabXnbF4Exe3V6f7RuxhiOY3fMeEI+shjU8rKz9fgMZKZ0cHrDNPyjbZKVO5x7UDYtL+p+TuQ3643AqbzyWE78RbKUli0rVKzP1AWFnW9Nj1F2WXri+VL8eA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778060727; c=relaxed/simple; bh=2t9L31CurR28eOltO1eS/4M9dmxEnpUnjiQfALWhCkg=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=nCZwSgb6MowQPELrHkbsIoH8y3h3dh6UmRcpr85WozficMuNB9pJg1yrgmoVOrziTqXogj6sRUnqpg+so5CfOT2z++r8V2EKPLbHWx/98Vs7eskkANvAf0MXa7WP+79bskRGy0Wd/fSVic624adUWdkTz4wigihWB8vMmq/BcHc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=gT8rV42M; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="gT8rV42M" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5E3261A9A; Wed, 6 May 2026 02:45:14 -0700 (PDT) Received: from a080796.blr.arm.com (a080796.arm.com [10.164.21.51]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id CCE223F7B4; Wed, 6 May 2026 02:45:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1778060719; bh=2t9L31CurR28eOltO1eS/4M9dmxEnpUnjiQfALWhCkg=; h=From:To:Cc:Subject:Date:From; b=gT8rV42Mxd4wvgf5OaeZErHCRVkQ1VYUGuARq+ONMgYtfMHQ1IiZdToGo+9gexoLI Fi3Ewq0j5MAodsRqKhN4Xd68ynhMfMZKfmRjmvURCvjjE1/KFGtViKArO9PZA9W3NJ RnRAhNrtDGa9jGjWHDu5s3xQnVEi/V9YBQ8Q2OFE= From: Dev Jain To: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, hughd@google.com, chrisl@kernel.org, kasong@tencent.com Cc: Dev Jain , riel@surriel.com, liam@infradead.org, vbabka@kernel.org, harry@kernel.org, jannh@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, rppt@kernel.org, surenb@google.com, mhocko@suse.com, baolin.wang@linux.alibaba.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, youngjun.park@lge.com, pfalcato@suse.de, ryan.roberts@arm.com, anshuman.khandual@arm.com Subject: [PATCH v3 0/9] Optimize anonymous large folio unmapping Date: Wed, 6 May 2026 15:14:55 +0530 Message-Id: <20260506094504.2588857-1-dev.jain@arm.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 (2d565cbaafd4). 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 (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 | 34 ++-- include/linux/rmap.h | 27 ++- mm/internal.h | 26 +++ mm/memory.c | 26 +-- mm/mprotect.c | 17 -- mm/rmap.c | 405 ++++++++++++++++++++++++-------------- mm/shmem.c | 8 +- mm/swap.h | 23 ++- mm/swapfile.c | 42 ++-- 10 files changed, 383 insertions(+), 236 deletions(-) -- 2.34.1