From nobody Wed Oct 8 13:22:11 2025 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 9F39219597F for ; Sat, 28 Jun 2025 11:35:12 +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=1751110514; cv=none; b=MuLaEF48kUCdZpvpy0MJ3xomo8qT+fQzrqk34ppTwRzchTawtb4asEck55uO7C+rzZpRHnbcrcftjZqUQ9rheSFeaiObt5ccQvjVpGxI9grbK+wulZOO2K6So/gbyJDNwtQ2jbDJ7sr41VLk8jM9DMUZhd939cbW8KFdGzK8l+w= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751110514; c=relaxed/simple; bh=b1d7X82GHOJNLPT9iA1Dynudh1Z4P9OP6XokhhKVDH8=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=csKcPZ+1kjwx/SqEzrgRQV4CziwhQ5/0ddzFRL0DEUTddQ4U673SvY8N8to5qDgBw6dZvQD6SFhni3YkobmEeAB5Kpog5IHXlIp42hCK6P/P/ZdlbgOeJXvxRWMZ4EWZhOtqyxP4yaw7KdSjofGEVoSDuBnAOrMboavEXMjVELw= 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; 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 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 0837F2574; Sat, 28 Jun 2025 04:34:55 -0700 (PDT) Received: from MacBook-Pro.blr.arm.com (MacBook-Pro.blr.arm.com [10.164.18.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 213E33F762; Sat, 28 Jun 2025 04:35:03 -0700 (PDT) From: Dev Jain To: akpm@linux-foundation.org Cc: ryan.roberts@arm.com, david@redhat.com, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, anshuman.khandual@arm.com, peterx@redhat.com, joey.gouly@arm.com, ioworker0@gmail.com, baohua@kernel.org, kevin.brodsky@arm.com, quic_zhenhuah@quicinc.com, christophe.leroy@csgroup.eu, yangyicong@hisilicon.com, linux-arm-kernel@lists.infradead.org, hughd@google.com, yang@os.amperecomputing.com, ziy@nvidia.com, Dev Jain Subject: [PATCH v4 1/4] mm: Optimize mprotect() for MM_CP_PROT_NUMA by batch-skipping PTEs Date: Sat, 28 Jun 2025 17:04:32 +0530 Message-Id: <20250628113435.46678-2-dev.jain@arm.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <20250628113435.46678-1-dev.jain@arm.com> References: <20250628113435.46678-1-dev.jain@arm.com> 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" In case of prot_numa, there are various cases in which we can skip to the next iteration. Since the skip condition is based on the folio and not the PTEs, we can skip a PTE batch. Additionally refactor all of this into a new function to clean up the existing code. Signed-off-by: Dev Jain --- mm/mprotect.c | 134 ++++++++++++++++++++++++++++++++------------------ 1 file changed, 87 insertions(+), 47 deletions(-) diff --git a/mm/mprotect.c b/mm/mprotect.c index 88709c01177b..af10a7fbe6b8 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -83,6 +83,83 @@ bool can_change_pte_writable(struct vm_area_struct *vma,= unsigned long addr, return pte_dirty(pte); } =20 +static int mprotect_folio_pte_batch(struct folio *folio, unsigned long add= r, + pte_t *ptep, pte_t pte, int max_nr_ptes) +{ + const fpb_t flags =3D FPB_IGNORE_DIRTY | FPB_IGNORE_SOFT_DIRTY; + + if (!folio || !folio_test_large(folio) || (max_nr_ptes =3D=3D 1)) + return 1; + + return folio_pte_batch(folio, addr, ptep, pte, max_nr_ptes, flags, + NULL, NULL, NULL); +} + +static int prot_numa_skip_ptes(struct folio **foliop, struct vm_area_struc= t *vma, + unsigned long addr, pte_t oldpte, pte_t *pte, int target_node, + int max_nr_ptes) +{ + struct folio *folio =3D NULL; + int nr_ptes =3D 1; + bool toptier; + int nid; + + /* Avoid TLB flush if possible */ + if (pte_protnone(oldpte)) + goto skip_batch; + + folio =3D vm_normal_folio(vma, addr, oldpte); + if (!folio) + goto skip_batch; + + if (folio_is_zone_device(folio) || folio_test_ksm(folio)) + goto skip_batch; + + /* Also skip shared copy-on-write pages */ + if (is_cow_mapping(vma->vm_flags) && + (folio_maybe_dma_pinned(folio) || folio_maybe_mapped_shared(folio))) + goto skip_batch; + + /* + * While migration can move some dirty pages, + * it cannot move them all from MIGRATE_ASYNC + * context. + */ + if (folio_is_file_lru(folio) && folio_test_dirty(folio)) + goto skip_batch; + + /* + * Don't mess with PTEs if page is already on the node + * a single-threaded process is running on. + */ + nid =3D folio_nid(folio); + if (target_node =3D=3D nid) + goto skip_batch; + + toptier =3D node_is_toptier(nid); + + /* + * Skip scanning top tier node if normal numa + * balancing is disabled + */ + if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) && toptier) + goto skip_batch; + + if (folio_use_access_time(folio)) { + folio_xchg_access_time(folio, jiffies_to_msecs(jiffies)); + + /* Do not skip in this case */ + nr_ptes =3D 0; + goto out; + } + +skip_batch: + nr_ptes =3D mprotect_folio_pte_batch(folio, addr, pte, oldpte, max_nr_pte= s); +out: + *foliop =3D folio; + return nr_ptes; +} + static long change_pte_range(struct mmu_gather *tlb, struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr, unsigned long end, pgprot_t newprot, unsigned long cp_flags) @@ -94,6 +171,7 @@ static long change_pte_range(struct mmu_gather *tlb, bool prot_numa =3D cp_flags & MM_CP_PROT_NUMA; bool uffd_wp =3D cp_flags & MM_CP_UFFD_WP; bool uffd_wp_resolve =3D cp_flags & MM_CP_UFFD_WP_RESOLVE; + int nr_ptes; =20 tlb_change_page_size(tlb, PAGE_SIZE); pte =3D pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); @@ -108,8 +186,11 @@ static long change_pte_range(struct mmu_gather *tlb, flush_tlb_batched_pending(vma->vm_mm); arch_enter_lazy_mmu_mode(); do { + nr_ptes =3D 1; oldpte =3D ptep_get(pte); if (pte_present(oldpte)) { + int max_nr_ptes =3D (end - addr) >> PAGE_SHIFT; + struct folio *folio =3D NULL; pte_t ptent; =20 /* @@ -117,53 +198,12 @@ static long change_pte_range(struct mmu_gather *tlb, * pages. See similar comment in change_huge_pmd. */ if (prot_numa) { - struct folio *folio; - int nid; - bool toptier; - - /* Avoid TLB flush if possible */ - if (pte_protnone(oldpte)) - continue; - - folio =3D vm_normal_folio(vma, addr, oldpte); - if (!folio || folio_is_zone_device(folio) || - folio_test_ksm(folio)) - continue; - - /* Also skip shared copy-on-write pages */ - if (is_cow_mapping(vma->vm_flags) && - (folio_maybe_dma_pinned(folio) || - folio_maybe_mapped_shared(folio))) - continue; - - /* - * While migration can move some dirty pages, - * it cannot move them all from MIGRATE_ASYNC - * context. - */ - if (folio_is_file_lru(folio) && - folio_test_dirty(folio)) - continue; - - /* - * Don't mess with PTEs if page is already on the node - * a single-threaded process is running on. - */ - nid =3D folio_nid(folio); - if (target_node =3D=3D nid) - continue; - toptier =3D node_is_toptier(nid); - - /* - * Skip scanning top tier node if normal numa - * balancing is disabled - */ - if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) && - toptier) + nr_ptes =3D prot_numa_skip_ptes(&folio, vma, + addr, oldpte, pte, + target_node, + max_nr_ptes); + if (nr_ptes) continue; - if (folio_use_access_time(folio)) - folio_xchg_access_time(folio, - jiffies_to_msecs(jiffies)); } =20 oldpte =3D ptep_modify_prot_start(vma, addr, pte); @@ -280,7 +320,7 @@ static long change_pte_range(struct mmu_gather *tlb, pages++; } } - } while (pte++, addr +=3D PAGE_SIZE, addr !=3D end); + } while (pte +=3D nr_ptes, addr +=3D nr_ptes * PAGE_SIZE, addr !=3D end); arch_leave_lazy_mmu_mode(); pte_unmap_unlock(pte - 1, ptl); =20 --=20 2.30.2