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 BB53827B35B for ; Tue, 10 Feb 2026 01:53:44 +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=1770688424; cv=none; b=fGIuGVy8XAM6Dqq8zdxfbl5Cgzoyk/lGathz3Mey0VjPwu+ISp9KvZI7r0oU8BZz++JjRsVuUkyHiLHftcHJmvbn9Ky3kjyuKSULcwAE7DOKWowEZ3tV2bszCy56GnKnklg3LUuRioDcK3tCCr4tjTobFYEZUcTsPTBq2nIip5s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770688424; c=relaxed/simple; bh=dTlgmKkXUK5Su+MeTHOp7KFM8ri18T90z3fVgMQoyY4=; h=Date:To:From:Subject:Message-Id; b=UzWGVhML1eo8ATsZyZrnPI3jWp+qjyKe9e5ehtaxxu66SKmainIWE/B7v+xsGbX8x7GNGK5e1cXMec7gl02VITzTrwP48UCKTy+4G+wXqMoNkira3d20o+2BsHpLMpSNGS89+IIRHoRznZkCyvL1EmUH1b2sW5viyG+n9dGbOBo= 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=NSqFr7VM; 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="NSqFr7VM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 65037C116C6; Tue, 10 Feb 2026 01:53:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1770688424; bh=dTlgmKkXUK5Su+MeTHOp7KFM8ri18T90z3fVgMQoyY4=; h=Date:To:From:Subject:From; b=NSqFr7VM2rM+s80zcmlvwAV5cW4Y3y6cEJLXbnfJM6LRg1W49UO7/lCoM8eF4C7uH yePIckHFsC3boTldGdw6n6eaMLrUp42mjkJtIbFJ7Bbp/T1BTluldtxyBFdXlN5j1U GZp5k3Lvi9ui6J4Nj9yV5qYfkHLYCDfnLCbPmfQc= Date: Mon, 09 Feb 2026 17:53:43 -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,harry.yoo@oracle.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-unstable branch Message-Id: <20260210015344.65037C116C6@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-unstable 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-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm 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: Mon, 9 Feb 2026 22:07:24 +0800 Patch series "support batch checking of references and unmapping for large folios", v6. 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.1770645603.git.baolin.wang@linux.alibaba.com Link: https://lkml.kernel.org/r/12132694536834262062d1fb304f8f8a064b6750.1770645603.git.baolin.wang@linux.alibaba.com Signed-off-by: Baolin Wang Reviewed-by: Harry Yoo Reviewed-by: Ryan Roberts Acked-by: David Hildenbrand (Arm) Cc: Catalin Marinas 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 Cc: Barry Song Signed-off-by: Andrew Morton --- include/linux/mmu_notifier.h | 9 ++++---- include/linux/pgtable.h | 35 +++++++++++++++++++++++++++++++++ mm/rmap.c | 28 +++++++++++++++++++++++--- 3 files changed, 65 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 @@ -1068,6 +1068,41 @@ static inline void wrprotect_ptes(struct } #endif +#ifndef clear_flush_young_ptes +/** + * clear_flush_young_ptes - Mark PTEs that map consecutive pages of the same + * folio as old and flush the TLB. + * @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 young = 0; + + for (;;) { + young |= ptep_clear_flush_young(vma, addr, ptep); + if (--nr == 0) + break; + ptep++; + addr += PAGE_SIZE; + } + + 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 @@ -913,9 +913,11 @@ 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++; @@ -960,9 +962,21 @@ 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)) @@ -972,7 +986,15 @@ 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