From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CD9B526FD93 for ; Sun, 28 Dec 2025 20:02:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766952178; cv=none; b=eKFpbQ0fIaHIzniZADHBqIl15d6c0phNr43Hug33JmMTRqZqRpw01T1qyVs/IE9hKJCr8Ibezrr2AujlrElvCN/08L6AsH36/hp3EbMazvD437Bnf/yix3H4mgj5zIMfK+bhgkGISHmuI82gsJILax3lnf4+dddo3/74Kuy2Xe8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766952178; c=relaxed/simple; bh=2zOowdCOLBRFSl8NMKgGc/yVOftiaeMrwP5dMgG3SiM=; h=Date:To:From:Subject:Message-Id; b=aOkqrNWWD+uz7WiP75XQBLLn/8sgAApDYS1gPDnZxDMgfuhpNwR50TJNZ6VfDFymii22vo7v+4DMZhDcK+ITOdW8aqNmH81kG4HLXz3Eukox8nf2xgw8EX59ws7IihTwNgyX8P6j3c6vxMXZzvEdObJ5D2fAxGwXy8t7SpY0SiA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=cTW1YH0g; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="cTW1YH0g" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 50965C4CEFB; Sun, 28 Dec 2025 20:02:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1766952178; bh=2zOowdCOLBRFSl8NMKgGc/yVOftiaeMrwP5dMgG3SiM=; h=Date:To:From:Subject:From; b=cTW1YH0gvOAM3N3KRcDBI/JfDnzDgIfUMukp53/R0MWYv9TdmEkx+JACZAltHl5Nc iu2aLgVIPyur5+r0Jl3SevUH4xSNdUhJHZL9eZ87dDc7OZVBYeBERaUM7tAkf+kGrN nTiWlBeKs127orklS5NM1w3YqkdW0iOUnB1adGaU= Date: Sun, 28 Dec 2025 12:02:57 -0800 To: mm-commits@vger.kernel.org,willy@infradead.org,will@kernel.org,vbabka@suse.cz,surenb@google.com,ryan.roberts@arm.com,rppt@kernel.org,riel@surriel.com,mhocko@suse.com,lorenzo.stoakes@oracle.com,liam.howlett@oracle.com,jannh@google.com,dev.jain@arm.com,david@kernel.org,catalin.marinas@arm.com,baohua@kernel.org,baolin.wang@linux.alibaba.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-rmap-support-batched-checks-of-the-references-for-large-folios.patch added to mm-new branch Message-Id: <20251228200258.50965C4CEFB@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm: rmap: support batched checks of the references for large folios has been added to the -mm mm-new branch. Its filename is mm-rmap-support-batched-checks-of-the-references-for-large-folios.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-rmap-support-batched-checks-of-the-references-for-large-folios.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Baolin Wang Subject: mm: rmap: support batched checks of the references for large folios Date: Fri, 26 Dec 2025 14:07:55 +0800 Patch series "support batch checking of references and unmapping for large folios", v5. Currently, folio_referenced_one() always checks the young flag for each PTE sequentially, which is inefficient for large folios. This inefficiency is especially noticeable when reclaiming clean file-backed large folios, where folio_referenced() is observed as a significant performance hotspot. Moreover, on Arm architecture, which supports contiguous PTEs, there is already an optimization to clear the young flags for PTEs within a contiguous range. However, this is not sufficient. We can extend this to perform batched operations for the entire large folio (which might exceed the contiguous range: CONT_PTE_SIZE). Similar to folio_referenced_one(), we can also apply batched unmapping for large file folios to optimize the performance of file folio reclamation. By supporting batched checking of the young flags, flushing TLB entries, and unmapping, I can observed a significant performance improvements in my performance tests for file folios reclamation. Please check the performance data in the commit message of each patch. This patch (of 5): Currently, folio_referenced_one() always checks the young flag for each PTE sequentially, which is inefficient for large folios. This inefficiency is especially noticeable when reclaiming clean file-backed large folios, where folio_referenced() is observed as a significant performance hotspot. Moreover, on Arm64 architecture, which supports contiguous PTEs, there is already an optimization to clear the young flags for PTEs within a contiguous range. However, this is not sufficient. We can extend this to perform batched operations for the entire large folio (which might exceed the contiguous range: CONT_PTE_SIZE). Introduce a new API: clear_flush_young_ptes() to facilitate batched checking of the young flags and flushing TLB entries, thereby improving performance during large folio reclamation. And it will be overridden by the architecture that implements a more efficient batch operation in the following patches. While we are at it, rename ptep_clear_flush_young_notify() to clear_flush_young_ptes_notify() to indicate that this is a batch operation. Link: https://lkml.kernel.org/r/cover.1766631066.git.baolin.wang@linux.alibaba.com Link: https://lkml.kernel.org/r/18b3eb9c730d16756e5d23c7be22efe2f6219911.1766631066.git.baolin.wang@linux.alibaba.com Signed-off-by: Baolin Wang Reviewed-by: Ryan Roberts Cc: Barry Song Cc: Catalin Marinas Cc: David Hildenbrand (Red Hat) Cc: Dev Jain Cc: Jann Horn Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Rik van Riel Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Will Deacon Signed-off-by: Andrew Morton --- include/linux/mmu_notifier.h | 9 +++++---- include/linux/pgtable.h | 31 +++++++++++++++++++++++++++++++ mm/rmap.c | 31 ++++++++++++++++++++++++++++--- 3 files changed, 64 insertions(+), 7 deletions(-) --- a/include/linux/mmu_notifier.h~mm-rmap-support-batched-checks-of-the-references-for-large-folios +++ a/include/linux/mmu_notifier.h @@ -515,16 +515,17 @@ static inline void mmu_notifier_range_in range->owner = owner; } -#define ptep_clear_flush_young_notify(__vma, __address, __ptep) \ +#define clear_flush_young_ptes_notify(__vma, __address, __ptep, __nr) \ ({ \ int __young; \ struct vm_area_struct *___vma = __vma; \ unsigned long ___address = __address; \ - __young = ptep_clear_flush_young(___vma, ___address, __ptep); \ + unsigned int ___nr = __nr; \ + __young = clear_flush_young_ptes(___vma, ___address, __ptep, ___nr); \ __young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \ ___address, \ ___address + \ - PAGE_SIZE); \ + ___nr * PAGE_SIZE); \ __young; \ }) @@ -650,7 +651,7 @@ static inline void mmu_notifier_subscrip #define mmu_notifier_range_update_to_read_only(r) false -#define ptep_clear_flush_young_notify ptep_clear_flush_young +#define clear_flush_young_ptes_notify clear_flush_young_ptes #define pmdp_clear_flush_young_notify pmdp_clear_flush_young #define ptep_clear_young_notify ptep_test_and_clear_young #define pmdp_clear_young_notify pmdp_test_and_clear_young --- a/include/linux/pgtable.h~mm-rmap-support-batched-checks-of-the-references-for-large-folios +++ a/include/linux/pgtable.h @@ -1087,6 +1087,37 @@ static inline void wrprotect_ptes(struct } #endif +#ifndef clear_flush_young_ptes +/** + * clear_flush_young_ptes - Clear the access bit and perform a TLB flush for PTEs + * that map consecutive pages of the same folio. + * @vma: The virtual memory area the pages are mapped into. + * @addr: Address the first page is mapped at. + * @ptep: Page table pointer for the first entry. + * @nr: Number of entries to clear access bit. + * + * May be overridden by the architecture; otherwise, implemented as a simple + * loop over ptep_clear_flush_young(). + * + * Note that PTE bits in the PTE range besides the PFN can differ. For example, + * some PTEs might be write-protected. + * + * Context: The caller holds the page table lock. The PTEs map consecutive + * pages that belong to the same folio. The PTEs are all in the same PMD. + */ +static inline int clear_flush_young_ptes(struct vm_area_struct *vma, + unsigned long addr, pte_t *ptep, + unsigned int nr) +{ + int i, young = 0; + + for (i = 0; i < nr; ++i, ++ptep, addr += PAGE_SIZE) + young |= ptep_clear_flush_young(vma, addr, ptep); + + return young; +} +#endif + /* * On some architectures hardware does not set page access bit when accessing * memory page, it is responsibility of software setting this bit. It brings --- a/mm/rmap.c~mm-rmap-support-batched-checks-of-the-references-for-large-folios +++ a/mm/rmap.c @@ -828,9 +828,11 @@ static bool folio_referenced_one(struct struct folio_referenced_arg *pra = arg; DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0); int ptes = 0, referenced = 0; + unsigned int nr; while (page_vma_mapped_walk(&pvmw)) { address = pvmw.address; + nr = 1; if (vma->vm_flags & VM_LOCKED) { ptes++; @@ -875,9 +877,24 @@ static bool folio_referenced_one(struct if (lru_gen_look_around(&pvmw)) referenced++; } else if (pvmw.pte) { - if (ptep_clear_flush_young_notify(vma, address, - pvmw.pte)) + if (folio_test_large(folio)) { + unsigned long end_addr = + pmd_addr_end(address, vma->vm_end); + unsigned int max_nr = + (end_addr - address) >> PAGE_SHIFT; + pte_t pteval = ptep_get(pvmw.pte); + + nr = folio_pte_batch(folio, pvmw.pte, + pteval, max_nr); + } + + ptes += nr; + if (clear_flush_young_ptes_notify(vma, address, + pvmw.pte, nr)) referenced++; + /* Skip the batched PTEs */ + pvmw.pte += nr - 1; + pvmw.address += (nr - 1) * PAGE_SIZE; } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { if (pmdp_clear_flush_young_notify(vma, address, pvmw.pmd)) @@ -887,7 +904,15 @@ static bool folio_referenced_one(struct WARN_ON_ONCE(1); } - pra->mapcount--; + pra->mapcount -= nr; + /* + * If we are sure that we batched the entire folio, + * we can just optimize and stop right here. + */ + if (ptes == pvmw.nr_pages) { + page_vma_mapped_walk_done(&pvmw); + break; + } } if (referenced) _ Patches currently in -mm which might be from baolin.wang@linux.alibaba.com are mm-rmap-support-batched-checks-of-the-references-for-large-folios.patch arm64-mm-factor-out-the-address-and-ptep-alignment-into-a-new-helper.patch arm64-mm-support-batch-clearing-of-the-young-flag-for-large-folios.patch arm64-mm-implement-the-architecture-specific-clear_flush_young_ptes.patch mm-rmap-support-batched-unmapping-for-file-large-folios.patch