From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8F0B2256C9F for ; Wed, 21 May 2025 11:58:50 +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=1747828732; cv=none; b=osj0IBNi6H50klD/tPOdolXE8tLVtZ+0K4yX22KB0B62Ka1rz/A/mJZZwB9+cbWGU1LXeu7WsBiZxyTprJ8FWmvbU9Wgq9hneH6nqa4dlgu0CPC1FphJh93uDyCoJ0b0VNDq/RWAfV8ePm0h+U/waZKQXIj5ghnPYpWsU1d9rf0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747828732; c=relaxed/simple; bh=y8LNvCTSqWoC7VyYuBorMydHeaA5NTUu9Pu7gTfSwEE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=FDXdra60KPnDPpfqk9iDHhKqWr/TFNbj279H17r2RVcRa8TuBK1PMs9C6Sa+v2MiH2/MyIiYmJ5Ue3l5kh6pd2FKHdlIO64IjWb6Em9aW6yZO0dwHfBWgXKcmTGIb7JK1w0vZNjD1ZcKPYk8wLDzOi4aTWijrovYqDoHa+ELOsk= 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 092FB1515; Wed, 21 May 2025 04:58:36 -0700 (PDT) Received: from [10.57.94.227] (unknown [10.57.94.227]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1B24B3F5A1; Wed, 21 May 2025 04:58:45 -0700 (PDT) Message-ID: <00555927-bfa1-4df0-8107-7080447acaa6@arm.com> Date: Wed, 21 May 2025 12:58:44 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/5] mm: Optimize mprotect() by batch-skipping PTEs Content-Language: en-GB To: Dev Jain , akpm@linux-foundation.org Cc: 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 References: <20250519074824.42909-1-dev.jain@arm.com> <20250519074824.42909-2-dev.jain@arm.com> From: Ryan Roberts In-Reply-To: <20250519074824.42909-2-dev.jain@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 19/05/2025 08:48, Dev Jain wrote: > 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. > > Signed-off-by: Dev Jain > --- > mm/mprotect.c | 36 +++++++++++++++++++++++++++++------- > 1 file changed, 29 insertions(+), 7 deletions(-) > > diff --git a/mm/mprotect.c b/mm/mprotect.c > index 88608d0dc2c2..1ee160ed0b14 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -83,6 +83,18 @@ bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, > return pte_dirty(pte); > } > > +static int mprotect_batch(struct folio *folio, unsigned long addr, pte_t *ptep, Perhaps it should be called mprotect_folio_pte_batch() to match the existing madvise_folio_pte_batch()? > + pte_t pte, int max_nr_ptes) > +{ > + const fpb_t flags = FPB_IGNORE_DIRTY | FPB_IGNORE_SOFT_DIRTY; > + > + if (!folio_test_large(folio) || (max_nr_ptes == 1)) > + return 1; > + > + return folio_pte_batch(folio, addr, ptep, pte, max_nr_ptes, flags, > + NULL, NULL, NULL); > +} > + > 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 +106,7 @@ static long change_pte_range(struct mmu_gather *tlb, > bool prot_numa = cp_flags & MM_CP_PROT_NUMA; > bool uffd_wp = cp_flags & MM_CP_UFFD_WP; > bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; > + int nr_ptes; > > tlb_change_page_size(tlb, PAGE_SIZE); > pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); > @@ -108,8 +121,10 @@ static long change_pte_range(struct mmu_gather *tlb, > flush_tlb_batched_pending(vma->vm_mm); > arch_enter_lazy_mmu_mode(); > do { > + nr_ptes = 1; > oldpte = ptep_get(pte); > if (pte_present(oldpte)) { > + int max_nr_ptes = (end - addr) >> PAGE_SHIFT; > pte_t ptent; > > /* > @@ -126,15 +141,18 @@ static long change_pte_range(struct mmu_gather *tlb, > continue; > > folio = vm_normal_folio(vma, addr, oldpte); > - if (!folio || folio_is_zone_device(folio) || > - folio_test_ksm(folio)) > + if (!folio) > continue; You modify mprotect_batch() to handle folio == NULL later, perhaps just add that here, then you don't need to unpick this conditional and can just goto skip_branch, even for the !folio case. Thanks, Ryan > > + 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))) > - continue; > + goto skip_batch; > > /* > * While migration can move some dirty pages, > @@ -143,7 +161,7 @@ static long change_pte_range(struct mmu_gather *tlb, > */ > if (folio_is_file_lru(folio) && > folio_test_dirty(folio)) > - continue; > + goto skip_batch; > > /* > * Don't mess with PTEs if page is already on the node > @@ -151,7 +169,7 @@ static long change_pte_range(struct mmu_gather *tlb, > */ > nid = folio_nid(folio); > if (target_node == nid) > - continue; > + goto skip_batch; > toptier = node_is_toptier(nid); > > /* > @@ -159,8 +177,12 @@ static long change_pte_range(struct mmu_gather *tlb, > * balancing is disabled > */ > if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) && > - toptier) > + toptier) { > +skip_batch: > + nr_ptes = mprotect_batch(folio, addr, pte, > + oldpte, max_nr_ptes); > continue; > + } > if (folio_use_access_time(folio)) > folio_xchg_access_time(folio, > jiffies_to_msecs(jiffies)); > @@ -280,7 +302,7 @@ static long change_pte_range(struct mmu_gather *tlb, > pages++; > } > } > - } while (pte++, addr += PAGE_SIZE, addr != end); > + } while (pte += nr_ptes, addr += nr_ptes * PAGE_SIZE, addr != end); > arch_leave_lazy_mmu_mode(); > pte_unmap_unlock(pte - 1, ptl); >