From nobody Tue Dec 16 14:20:44 2025 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0C9781FDA for ; Tue, 27 May 2025 07:51:18 +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=1748332283; cv=none; b=Tl9rt2pB+Po2JCvX23hnFmjMl3VDEneATATIrEdCp3B3+C53mQod4+dUmP8cQBdgWkdOV7teNwI4uu6JejRhPk9vh493izpnUPoqQ3gXNaMdnKVEMZNYcTgvNQSTTM8NJzvJEwgS1CHqli/7AdaJhpGbbDO2oQLBPEXukb1jjbs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748332283; c=relaxed/simple; bh=vYDQyzHSKBnSWwXwBVNZsHhXumIsta3zonGSrGMYiVU=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=sDoeIKuGERwO42KYunb3HHSLTtmaYbG9ytE0xT7H6HZrjte9x5D5bWI+LuR5FlgIiOihActuVGSWCIl/xGeQoHEyJxsRIMfYPaQv2dGZkDiGBSYyvJzkC2xDCqqmVeSYnjYUQsWtA/+pXWPe5EjKeZEs7pZtOmpugcHwDr1naMo= 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 6626E14BF; Tue, 27 May 2025 00:51:02 -0700 (PDT) Received: from localhost.localdomain (unknown [10.163.85.29]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 185893F694; Tue, 27 May 2025 00:51:10 -0700 (PDT) From: Dev Jain To: akpm@linux-foundation.org Cc: Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, pfalcato@suse.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, david@redhat.com, peterx@redhat.com, ryan.roberts@arm.com, mingo@kernel.org, libang.li@antgroup.com, maobibo@loongson.cn, zhengqi.arch@bytedance.com, baohua@kernel.org, anshuman.khandual@arm.com, willy@infradead.org, ioworker0@gmail.com, yang@os.amperecomputing.com, baolin.wang@linux.alibaba.com, ziy@nvidia.com, hughd@google.com, Dev Jain Subject: [PATCH v3 2/2] mm: Optimize mremap() by PTE batching Date: Tue, 27 May 2025 13:20:49 +0530 Message-Id: <20250527075049.60215-3-dev.jain@arm.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <20250527075049.60215-1-dev.jain@arm.com> References: <20250527075049.60215-1-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" Use folio_pte_batch() to optimize move_ptes(). On arm64, if the ptes are painted with the contig bit, then ptep_get() will iterate through all 16 entries to collect a/d bits. Hence this optimization will result in a 16x reduction in the number of ptep_get() calls. Next, ptep_get_and_clear() will eventually call contpte_try_unfold() on every contig block, thus flushing the TLB for the complete large folio range. Instead, use get_and_clear_full_ptes() so as to elide TLBIs on each contig block, and on= ly do them on the starting and ending contig block. Signed-off-by: Dev Jain --- mm/mremap.c | 40 +++++++++++++++++++++++++++++++++------- 1 file changed, 33 insertions(+), 7 deletions(-) diff --git a/mm/mremap.c b/mm/mremap.c index 0163e02e5aa8..580b41f8d169 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -170,6 +170,24 @@ static pte_t move_soft_dirty_pte(pte_t pte) return pte; } =20 +/* mremap a batch of PTEs mapping the same large folio */ +static int mremap_folio_pte_batch(struct vm_area_struct *vma, unsigned lon= g addr, + pte_t *ptep, pte_t pte, int max_nr) +{ + const fpb_t flags =3D FPB_IGNORE_DIRTY | FPB_IGNORE_SOFT_DIRTY; + struct folio *folio; + + if (max_nr =3D=3D 1) + return 1; + + folio =3D vm_normal_folio(vma, addr, pte); + if (!folio || !folio_test_large(folio)) + return 1; + + return folio_pte_batch(folio, addr, ptep, pte, max_nr, flags, NULL, + NULL, NULL); +} + static int move_ptes(struct pagetable_move_control *pmc, unsigned long extent, pmd_t *old_pmd, pmd_t *new_pmd) { @@ -177,7 +195,7 @@ static int move_ptes(struct pagetable_move_control *pmc, bool need_clear_uffd_wp =3D vma_has_uffd_without_event_remap(vma); struct mm_struct *mm =3D vma->vm_mm; pte_t *old_ptep, *new_ptep; - pte_t pte; + pte_t old_pte, pte; pmd_t dummy_pmdval; spinlock_t *old_ptl, *new_ptl; bool force_flush =3D false; @@ -185,6 +203,8 @@ static int move_ptes(struct pagetable_move_control *pmc, unsigned long new_addr =3D pmc->new_addr; unsigned long old_end =3D old_addr + extent; unsigned long len =3D old_end - old_addr; + int max_nr_ptes; + int nr_ptes; int err =3D 0; =20 /* @@ -236,12 +256,14 @@ static int move_ptes(struct pagetable_move_control *p= mc, flush_tlb_batched_pending(vma->vm_mm); arch_enter_lazy_mmu_mode(); =20 - for (; old_addr < old_end; old_ptep++, old_addr +=3D PAGE_SIZE, - new_ptep++, new_addr +=3D PAGE_SIZE) { - if (pte_none(ptep_get(old_ptep))) + for (; old_addr < old_end; old_ptep +=3D nr_ptes, old_addr +=3D nr_ptes *= PAGE_SIZE, + new_ptep +=3D nr_ptes, new_addr +=3D nr_ptes * PAGE_SIZE) { + nr_ptes =3D 1; + max_nr_ptes =3D (old_end - old_addr) >> PAGE_SHIFT; + old_pte =3D ptep_get(old_ptep); + if (pte_none(old_pte)) continue; =20 - pte =3D ptep_get_and_clear(mm, old_addr, old_ptep); /* * If we are remapping a valid PTE, make sure * to flush TLB before we drop the PTL for the @@ -253,8 +275,12 @@ static int move_ptes(struct pagetable_move_control *pm= c, * the TLB entry for the old mapping has been * flushed. */ - if (pte_present(pte)) + if (pte_present(old_pte)) { + nr_ptes =3D mremap_folio_pte_batch(vma, old_addr, old_ptep, + old_pte, max_nr_ptes); force_flush =3D true; + } + pte =3D get_and_clear_full_ptes(mm, old_addr, old_ptep, nr_ptes, 0); pte =3D move_pte(pte, old_addr, new_addr); pte =3D move_soft_dirty_pte(pte); =20 @@ -267,7 +293,7 @@ static int move_ptes(struct pagetable_move_control *pmc, else if (is_swap_pte(pte)) pte =3D pte_swp_clear_uffd_wp(pte); } - set_pte_at(mm, new_addr, new_ptep, pte); + set_ptes(mm, new_addr, new_ptep, pte, nr_ptes); } } =20 --=20 2.30.2