From nobody Sat Feb 7 08:43:36 2026 Received: from out30-131.freemail.mail.aliyun.com (out30-131.freemail.mail.aliyun.com [115.124.30.131]) (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 8B3ED26E6F2 for ; Fri, 26 Dec 2025 06:08:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.131 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766729294; cv=none; b=SKQuQ1eupxE7CXtj4Jm5aGgLP6Q0/o4j79GK19+gszuejefVRChUp8w6LoeubgyPUSHMyEh64V8OpEzYtbfkRC7Oq3I741Ek5nG/nIFouTDyiNpkWpbFs/+Wi3s+TD8VZcirnRqpQdqpZQIW0/RP9RvrtICYPX9AfPG1/wJD57U= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766729294; c=relaxed/simple; bh=4bcjds2mRUe9e8EYAxKeUMoiNdWPg9yTj7zI8q5s/M4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Gtrf1vmkTVznsxsT5hTB5Cw0l+/V38JokdUwCUaJkY4UUpbCWyMKFlKR9bCVvnXhaIxgn9YfWwXPHNLEVhHUNN0nsuAm87a8AdotdgL+bfnmJ3la/GgHYVASopNNegHApwBKGCOjM+HOXTYpDcPl3jaIbrcUetvU9zstrHuFeTQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=vnS+3iCv; arc=none smtp.client-ip=115.124.30.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="vnS+3iCv" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1766729288; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=nQOblmo1Xq9Mi6sOjwcZDMqeM3HaJgfSORShcGuHoSU=; b=vnS+3iCvjs3clh6XTawuuD4lIJTLS7pDaqG5A5AZTg5ebZkf4W0ncmLcnbHQxm4UWkwnb22ZIot/GseB0htrHEkgKN9E+5uJDiNHU3MsCaZvlAM5OSXCxZNLLDcUvVbrIxkrGbmd0Qrn7Qd37IaYgCrO0n949cedMpmO67UiOXc= Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WvgaV0W_1766729286 cluster:ay36) by smtp.aliyun-inc.com; Fri, 26 Dec 2025 14:08:07 +0800 From: Baolin Wang To: akpm@linux-foundation.org, david@kernel.org, catalin.marinas@arm.com, will@kernel.org Cc: lorenzo.stoakes@oracle.com, ryan.roberts@arm.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, riel@surriel.com, harry.yoo@oracle.com, jannh@google.com, willy@infradead.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v5 1/5] mm: rmap: support batched checks of the references for large folios Date: Fri, 26 Dec 2025 14:07:55 +0800 Message-ID: <18b3eb9c730d16756e5d23c7be22efe2f6219911.1766631066.git.baolin.wang@linux.alibaba.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 a= lready 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 oper= ations for the entire large folio (which might exceed the contiguous range: CONT_P= TE_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 architectu= re 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. Reviewed-by: Ryan Roberts Signed-off-by: Baolin Wang Reviewed-by: Harry Yoo --- include/linux/mmu_notifier.h | 9 +++++---- include/linux/pgtable.h | 31 +++++++++++++++++++++++++++++++ mm/rmap.c | 31 ++++++++++++++++++++++++++++--- 3 files changed, 64 insertions(+), 7 deletions(-) diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h index d1094c2d5fb6..07a2bbaf86e9 100644 --- a/include/linux/mmu_notifier.h +++ b/include/linux/mmu_notifier.h @@ -515,16 +515,17 @@ static inline void mmu_notifier_range_init_owner( range->owner =3D owner; } =20 -#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 =3D __vma; \ unsigned long ___address =3D __address; \ - __young =3D ptep_clear_flush_young(___vma, ___address, __ptep); \ + unsigned int ___nr =3D __nr; \ + __young =3D clear_flush_young_ptes(___vma, ___address, __ptep, ___nr); \ __young |=3D mmu_notifier_clear_flush_young(___vma->vm_mm, \ ___address, \ ___address + \ - PAGE_SIZE); \ + ___nr * PAGE_SIZE); \ __young; \ }) =20 @@ -650,7 +651,7 @@ static inline void mmu_notifier_subscriptions_destroy(s= truct mm_struct *mm) =20 #define mmu_notifier_range_update_to_read_only(r) false =20 -#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 diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 2f0dd3a4ace1..eb8aacba3698 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -1087,6 +1087,37 @@ static inline void wrprotect_ptes(struct mm_struct *= mm, unsigned long addr, } #endif =20 +#ifndef clear_flush_young_ptes +/** + * clear_flush_young_ptes - Clear the access bit and perform a TLB flush f= or 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 simp= le + * loop over ptep_clear_flush_young(). + * + * Note that PTE bits in the PTE range besides the PFN can differ. For exa= mple, + * 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 =3D 0; + + for (i =3D 0; i < nr; ++i, ++ptep, addr +=3D PAGE_SIZE) + young |=3D ptep_clear_flush_young(vma, addr, ptep); + + return young; +} +#endif + /* * On some architectures hardware does not set page access bit when access= ing * memory page, it is responsibility of software setting this bit. It brin= gs diff --git a/mm/rmap.c b/mm/rmap.c index e805ddc5a27b..985ab0b085ba 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -828,9 +828,11 @@ static bool folio_referenced_one(struct folio *folio, struct folio_referenced_arg *pra =3D arg; DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0); int ptes =3D 0, referenced =3D 0; + unsigned int nr; =20 while (page_vma_mapped_walk(&pvmw)) { address =3D pvmw.address; + nr =3D 1; =20 if (vma->vm_flags & VM_LOCKED) { ptes++; @@ -875,9 +877,24 @@ static bool folio_referenced_one(struct folio *folio, 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 =3D + pmd_addr_end(address, vma->vm_end); + unsigned int max_nr =3D + (end_addr - address) >> PAGE_SHIFT; + pte_t pteval =3D ptep_get(pvmw.pte); + + nr =3D folio_pte_batch(folio, pvmw.pte, + pteval, max_nr); + } + + ptes +=3D nr; + if (clear_flush_young_ptes_notify(vma, address, + pvmw.pte, nr)) referenced++; + /* Skip the batched PTEs */ + pvmw.pte +=3D nr - 1; + pvmw.address +=3D (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 folio *folio, WARN_ON_ONCE(1); } =20 - pra->mapcount--; + pra->mapcount -=3D nr; + /* + * If we are sure that we batched the entire folio, + * we can just optimize and stop right here. + */ + if (ptes =3D=3D pvmw.nr_pages) { + page_vma_mapped_walk_done(&pvmw); + break; + } } =20 if (referenced) --=20 2.47.3 From nobody Sat Feb 7 08:43:36 2026 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) (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 A28032989BF for ; Fri, 26 Dec 2025 06:08:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.133 ARC-Seal: i=1; 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charset="utf-8" Factor out the contpte block's address and ptep alignment into a new helper, and will be reused in the following patch. No functional changes. Reviewed-by: Ryan Roberts Signed-off-by: Baolin Wang --- arch/arm64/mm/contpte.c | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-) diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c index 589bcf878938..e4ddeb46f25d 100644 --- a/arch/arm64/mm/contpte.c +++ b/arch/arm64/mm/contpte.c @@ -26,6 +26,26 @@ static inline pte_t *contpte_align_down(pte_t *ptep) return PTR_ALIGN_DOWN(ptep, sizeof(*ptep) * CONT_PTES); } =20 +static inline pte_t *contpte_align_addr_ptep(unsigned long *start, + unsigned long *end, pte_t *ptep, + unsigned int nr) +{ + /* + * Note: caller must ensure these nr PTEs are consecutive (present) + * PTEs that map consecutive pages of the same large folio within a + * single VMA and a single page table. + */ + if (pte_cont(__ptep_get(ptep + nr - 1))) + *end =3D ALIGN(*end, CONT_PTE_SIZE); + + if (pte_cont(__ptep_get(ptep))) { + *start =3D ALIGN_DOWN(*start, CONT_PTE_SIZE); + ptep =3D contpte_align_down(ptep); + } + + return ptep; +} + static void contpte_try_unfold_partial(struct mm_struct *mm, unsigned long= addr, pte_t *ptep, unsigned int nr) { @@ -569,14 +589,7 @@ void contpte_clear_young_dirty_ptes(struct vm_area_str= uct *vma, unsigned long start =3D addr; unsigned long end =3D start + nr * PAGE_SIZE; =20 - if (pte_cont(__ptep_get(ptep + nr - 1))) - end =3D ALIGN(end, CONT_PTE_SIZE); - - if (pte_cont(__ptep_get(ptep))) { - start =3D ALIGN_DOWN(start, CONT_PTE_SIZE); - ptep =3D contpte_align_down(ptep); - } - + ptep =3D contpte_align_addr_ptep(&start, &end, ptep, nr); __clear_young_dirty_ptes(vma, start, ptep, (end - start) / PAGE_SIZE, fla= gs); } EXPORT_SYMBOL_GPL(contpte_clear_young_dirty_ptes); --=20 2.47.3 From nobody Sat Feb 7 08:43:36 2026 Received: from out30-119.freemail.mail.aliyun.com (out30-119.freemail.mail.aliyun.com [115.124.30.119]) (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 528AB2874F1 for ; 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charset="utf-8" Currently, contpte_ptep_test_and_clear_young() and contpte_ptep_clear_flush= _young() only clear the young flag and flush TLBs for PTEs within the contiguous ran= ge. To support batch PTE operations for other sized large folios in the followi= ng patches, adding a new parameter to specify the number of PTEs that map cons= ecutive pages of the same large folio in a single VMA and a single page table. While we are at it, rename the functions to maintain consistency with other contpte_*() functions. Signed-off-by: Baolin Wang Reviewed-by: Ryan Roberts --- arch/arm64/include/asm/pgtable.h | 12 ++++++------ arch/arm64/mm/contpte.c | 33 ++++++++++++++++++-------------- 2 files changed, 25 insertions(+), 20 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgta= ble.h index 445e18e92221..5e9ff16146c3 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1648,10 +1648,10 @@ extern void contpte_clear_full_ptes(struct mm_struc= t *mm, unsigned long addr, extern pte_t contpte_get_and_clear_full_ptes(struct mm_struct *mm, unsigned long addr, pte_t *ptep, unsigned int nr, int full); -extern int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, - unsigned long addr, pte_t *ptep); -extern int contpte_ptep_clear_flush_young(struct vm_area_struct *vma, - unsigned long addr, pte_t *ptep); +int contpte_test_and_clear_young_ptes(struct vm_area_struct *vma, + unsigned long addr, pte_t *ptep, unsigned int nr); +int contpte_clear_flush_young_ptes(struct vm_area_struct *vma, + unsigned long addr, pte_t *ptep, unsigned int nr); extern void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long add= r, pte_t *ptep, unsigned int nr); extern int contpte_ptep_set_access_flags(struct vm_area_struct *vma, @@ -1823,7 +1823,7 @@ static inline int ptep_test_and_clear_young(struct vm= _area_struct *vma, if (likely(!pte_valid_cont(orig_pte))) return __ptep_test_and_clear_young(vma, addr, ptep); =20 - return contpte_ptep_test_and_clear_young(vma, addr, ptep); + return contpte_test_and_clear_young_ptes(vma, addr, ptep, 1); } =20 #define __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH @@ -1835,7 +1835,7 @@ static inline int ptep_clear_flush_young(struct vm_ar= ea_struct *vma, if (likely(!pte_valid_cont(orig_pte))) return __ptep_clear_flush_young(vma, addr, ptep); =20 - return contpte_ptep_clear_flush_young(vma, addr, ptep); + return contpte_clear_flush_young_ptes(vma, addr, ptep, 1); } =20 #define wrprotect_ptes wrprotect_ptes diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c index e4ddeb46f25d..b929a455103f 100644 --- a/arch/arm64/mm/contpte.c +++ b/arch/arm64/mm/contpte.c @@ -508,8 +508,9 @@ pte_t contpte_get_and_clear_full_ptes(struct mm_struct = *mm, } EXPORT_SYMBOL_GPL(contpte_get_and_clear_full_ptes); =20 -int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, - unsigned long addr, pte_t *ptep) +int contpte_test_and_clear_young_ptes(struct vm_area_struct *vma, + unsigned long addr, pte_t *ptep, + unsigned int nr) { /* * ptep_clear_flush_young() technically requires us to clear the access @@ -518,41 +519,45 @@ int contpte_ptep_test_and_clear_young(struct vm_area_= struct *vma, * contig range when the range is covered by a single folio, we can get * away with clearing young for the whole contig range here, so we avoid * having to unfold. + * + * The 'nr' means consecutive (present) PTEs that map consecutive pages + * of the same large folio in a single VMA and a single page table. */ =20 + unsigned long end =3D addr + nr * PAGE_SIZE; int young =3D 0; - int i; =20 - ptep =3D contpte_align_down(ptep); - addr =3D ALIGN_DOWN(addr, CONT_PTE_SIZE); - - for (i =3D 0; i < CONT_PTES; i++, ptep++, addr +=3D PAGE_SIZE) + ptep =3D contpte_align_addr_ptep(&addr, &end, ptep, nr); + for (; addr !=3D end; ptep++, addr +=3D PAGE_SIZE) young |=3D __ptep_test_and_clear_young(vma, addr, ptep); =20 return young; } -EXPORT_SYMBOL_GPL(contpte_ptep_test_and_clear_young); +EXPORT_SYMBOL_GPL(contpte_test_and_clear_young_ptes); =20 -int contpte_ptep_clear_flush_young(struct vm_area_struct *vma, - unsigned long addr, pte_t *ptep) +int contpte_clear_flush_young_ptes(struct vm_area_struct *vma, + unsigned long addr, pte_t *ptep, + unsigned int nr) { int young; =20 - young =3D contpte_ptep_test_and_clear_young(vma, addr, ptep); + young =3D contpte_test_and_clear_young_ptes(vma, addr, ptep, nr); =20 if (young) { + unsigned long end =3D addr + nr * PAGE_SIZE; + + contpte_align_addr_ptep(&addr, &end, ptep, nr); /* * See comment in __ptep_clear_flush_young(); same rationale for * eliding the trailing DSB applies here. */ - addr =3D ALIGN_DOWN(addr, CONT_PTE_SIZE); - __flush_tlb_range_nosync(vma->vm_mm, addr, addr + CONT_PTE_SIZE, + __flush_tlb_range_nosync(vma->vm_mm, addr, end, PAGE_SIZE, true, 3); } =20 return young; } -EXPORT_SYMBOL_GPL(contpte_ptep_clear_flush_young); +EXPORT_SYMBOL_GPL(contpte_clear_flush_young_ptes); =20 void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr, pte_t *ptep, unsigned int nr) --=20 2.47.3 From nobody Sat Feb 7 08:43:36 2026 Received: from out30-97.freemail.mail.aliyun.com (out30-97.freemail.mail.aliyun.com [115.124.30.97]) (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 D7C88280A56 for ; Fri, 26 Dec 2025 06:08:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.97 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766729305; cv=none; b=gz7qCR9esnlPDt2rGkOoItmn2zFbYo2ccDK4nFp8l7r/Bq3X5+5i07DFwESdoAKZqAIgM6kNF7jlx0nJfck1wtYvxSPmlJKk3HDjNrNG73rz2i3JJFA1S9FarA85BOPuUkyUs3hR/KvNBXwCfbHTXsNVVMHhw9KUVlNJzX5kfOU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; 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charset="utf-8" Implement the Arm64 architecture-specific clear_flush_young_ptes() to enable batched checking of young flags and TLB flushing, improving performance dur= ing large folio reclamation. Performance testing: Allocate 10G clean file-backed folios by mmap() in a memory cgroup, and try= to reclaim 8G file-backed folios via the memory.reclaim interface. I can obser= ve 33% performance improvement on my Arm64 32-core server (and 10%+ improvement on my X86 machine). Meanwhile, the hotspot folio_check_references() dropped from approximately 35% to around 5%. W/o patchset: real 0m1.518s user 0m0.000s sys 0m1.518s W/ patchset: real 0m1.018s user 0m0.000s sys 0m1.018s Reviewed-by: Ryan Roberts Signed-off-by: Baolin Wang --- arch/arm64/include/asm/pgtable.h | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgta= ble.h index 5e9ff16146c3..aa8f642f1260 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1838,6 +1838,17 @@ static inline int ptep_clear_flush_young(struct vm_a= rea_struct *vma, return contpte_clear_flush_young_ptes(vma, addr, ptep, 1); } =20 +#define clear_flush_young_ptes clear_flush_young_ptes +static inline int clear_flush_young_ptes(struct vm_area_struct *vma, + unsigned long addr, pte_t *ptep, + unsigned int nr) +{ + if (likely(nr =3D=3D 1 && !pte_cont(__ptep_get(ptep)))) + return __ptep_clear_flush_young(vma, addr, ptep); + + return contpte_clear_flush_young_ptes(vma, addr, ptep, nr); +} + #define wrprotect_ptes wrprotect_ptes static __always_inline void wrprotect_ptes(struct mm_struct *mm, unsigned long addr, pte_t *ptep, unsigned int nr) --=20 2.47.3 From nobody Sat Feb 7 08:43:36 2026 Received: from out30-97.freemail.mail.aliyun.com (out30-97.freemail.mail.aliyun.com [115.124.30.97]) (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 1F68429D281 for ; Fri, 26 Dec 2025 06:08:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.97 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766729305; cv=none; b=gMXuDzNGIfSsZa6YdkFsVZ5QuA7Q6P/iw8LJVWUi9jQjrR0534kUlddaEtOyJoDSpEjtMP7Qm09MUZHpdI0EuGXLk8me4IZdcdnafJIDxnmoDjKYNAL1a4o49/DcM2BQpFhMGajKyxtCPzbvZzPrAN5aIviLuiE52rM9LTvqHIQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766729305; c=relaxed/simple; bh=MfxlhrA88ORfcYR+9tQiZZEpWEDCsoJAyiNjy15xW5w=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KctUy5SjaHigsW3gTDYwLC4Gb1VRg7HbNHcRdBW59rDl4L9X6SVxyR4SNvDBdwFf/gnIDT+/xGG+SZKR5gJJjCiMNpHcqliKZOMeS2mX/kG+V+KjQZ4i/JNsbpD5Qa0SsV9SwV1bNNJy1ISp3v1YcTO0RH1aUHwZKlGthEhf2as= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=g+ec1C/i; arc=none smtp.client-ip=115.124.30.97 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="g+ec1C/i" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1766729295; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=AZ9WfEpVe/JlQetyc2ZwVRBQF0W+yj98KQzc8zM0fSE=; b=g+ec1C/iGT09Sv2dj9lVFXA/jBxqHE2dC+98DdCNHfnpKMj7s1zJxBO+5yBm3gdWVE4yjqHOcc8tpIrTNj+Wm+sOX/dotDMbv4hjQKwginWmPTT+22ZQnwtBQlIg+ClwEfNURYrRzS2kysvwor4vtFhiumvGXgCpSExhBwB/tbE= Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WvgZmTZ_1766729292 cluster:ay36) by smtp.aliyun-inc.com; Fri, 26 Dec 2025 14:08:13 +0800 From: Baolin Wang To: akpm@linux-foundation.org, david@kernel.org, catalin.marinas@arm.com, will@kernel.org Cc: lorenzo.stoakes@oracle.com, ryan.roberts@arm.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, riel@surriel.com, harry.yoo@oracle.com, jannh@google.com, willy@infradead.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v5 5/5] mm: rmap: support batched unmapping for file large folios Date: Fri, 26 Dec 2025 14:07:59 +0800 Message-ID: <142919ac14d3cf70cba370808d85debe089df7b4.1766631066.git.baolin.wang@linux.alibaba.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Similar to folio_referenced_one(), we can apply batched unmapping for file large folios to optimize the performance of file folios reclamation. Barry previously implemented batched unmapping for lazyfree anonymous large folios[1] and did not further optimize anonymous large folios or file-backed large folios at that stage. As for file-backed large folios, the batched unmapping support is relatively straightforward, as we only need to clear the consecutive (present) PTE entries for file-backed large folios. Performance testing: Allocate 10G clean file-backed folios by mmap() in a memory cgroup, and try= to reclaim 8G file-backed folios via the memory.reclaim interface. I can obser= ve 75% performance improvement on my Arm64 32-core server (and 50%+ improvement on my X86 machine) with this patch. W/o patch: real 0m1.018s user 0m0.000s sys 0m1.018s W/ patch: real 0m0.249s user 0m0.000s sys 0m0.249s [1] https://lore.kernel.org/all/20250214093015.51024-4-21cnbao@gmail.com/T/= #u Reviewed-by: Ryan Roberts Acked-by: Barry Song Signed-off-by: Baolin Wang Reviewed-by: Harry Yoo --- mm/rmap.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index 985ab0b085ba..e1d16003c514 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1863,9 +1863,10 @@ static inline unsigned int folio_unmap_pte_batch(str= uct folio *folio, end_addr =3D pmd_addr_end(addr, vma->vm_end); max_nr =3D (end_addr - addr) >> PAGE_SHIFT; =20 - /* We only support lazyfree batching for now ... */ - if (!folio_test_anon(folio) || folio_test_swapbacked(folio)) + /* We only support lazyfree or file folios batching for now ... */ + if (folio_test_anon(folio) && folio_test_swapbacked(folio)) return 1; + if (pte_unused(pte)) return 1; =20 @@ -2231,7 +2232,7 @@ static bool try_to_unmap_one(struct folio *folio, str= uct vm_area_struct *vma, * * See Documentation/mm/mmu_notifier.rst */ - dec_mm_counter(mm, mm_counter_file(folio)); + add_mm_counter(mm, mm_counter_file(folio), -nr_pages); } discard: if (unlikely(folio_test_hugetlb(folio))) { --=20 2.47.3