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 7BA3429DB9B for ; Tue, 29 Apr 2025 08:59:27 +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=1745917169; cv=none; b=H1Urzvl9TryvEijFOZxAr8wKR3IuMOyxeP1F+HDdvE6u1KLdZG3f76pxPUzF5JbONxbpM0e+8AvdAnHieL22+39oMtSPpNK4X/beCSJdPKjMpU/T0vQwMH6MHbQ1aZdT5yvrdBDCmzQSPKs3LZr4Mh1YLdSlby4xPbc5Ix9oE5U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745917169; c=relaxed/simple; bh=+GhfafEzYP5vPOgXCfvc8wvhKT0+V97ZCyBqu2nN76k=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=AuQUOgfhO+7n9vIw1DJoiuseAfWBQcEaPflhtoE3c2Oj3j3NBoimvCSRZ6nWn8QFqDd3+cchuKBj/nVE/NoszyTfYA/Uym6TRd/4av86CIxFGXMWiiNT0w2UZAOCJW7doTT7JEwmaR7Ql30mAOOIC8Aus9zo5cn9zayemal3FE4= 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 DAC0A1515; Tue, 29 Apr 2025 01:59:19 -0700 (PDT) Received: from [10.163.78.253] (unknown [10.163.78.253]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 78FBB3F673; Tue, 29 Apr 2025 01:59:16 -0700 (PDT) Message-ID: <33e8d9fe-d30a-4cbb-b141-133b8989019e@arm.com> Date: Tue, 29 Apr 2025 14:29:13 +0530 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 v2 2/7] mm: Optimize mprotect() by batch-skipping PTEs To: Anshuman Khandual , 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, 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, namit@vmware.com, hughd@google.com, yang@os.amperecomputing.com, ziy@nvidia.com References: <20250429052336.18912-1-dev.jain@arm.com> <20250429052336.18912-3-dev.jain@arm.com> Content-Language: en-US From: Dev Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 29/04/25 12:44 pm, Anshuman Khandual wrote: > On 4/29/25 10:53, 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 | 27 ++++++++++++++++++++------- >> 1 file changed, 20 insertions(+), 7 deletions(-) >> >> diff --git a/mm/mprotect.c b/mm/mprotect.c >> index 70f59aa8c2a8..ec5d17af7650 100644 >> --- a/mm/mprotect.c >> +++ b/mm/mprotect.c >> @@ -91,6 +91,9 @@ static bool prot_numa_skip(struct vm_area_struct *vma, struct folio *folio, >> bool toptier; >> int nid; >> >> + if (folio_is_zone_device(folio) || folio_test_ksm(folio)) >> + return true; >> + > > Moving these here from prot_numa_avoid_fault() could have been done > earlier, while adding prot_numa_skip() itself in the previous patch > (in case this helper is determined to be really required). True. I'll do that. > >> /* Also skip shared copy-on-write pages */ >> if (is_cow_mapping(vma->vm_flags) && >> (folio_maybe_dma_pinned(folio) || >> @@ -126,8 +129,10 @@ static bool prot_numa_skip(struct vm_area_struct *vma, struct folio *folio, >> } >> >> static bool prot_numa_avoid_fault(struct vm_area_struct *vma, >> - unsigned long addr, pte_t oldpte, int target_node) >> + unsigned long addr, pte_t *pte, pte_t oldpte, int target_node, >> + int max_nr, int *nr) >> { >> + const fpb_t flags = FPB_IGNORE_DIRTY | FPB_IGNORE_SOFT_DIRTY; > > Flags are all correct. > >> struct folio *folio; >> int ret; >> >> @@ -136,12 +141,16 @@ static bool prot_numa_avoid_fault(struct vm_area_struct *vma, >> return true; >> >> folio = vm_normal_folio(vma, addr, oldpte); >> - if (!folio || folio_is_zone_device(folio) || >> - folio_test_ksm(folio)) >> + if (!folio) >> return true; >> + >> ret = prot_numa_skip(vma, folio, target_node); >> - if (ret) >> + if (ret) { >> + if (folio_test_large(folio) && max_nr != 1) > > Conditional checks are all correct. > >> + *nr = folio_pte_batch(folio, addr, pte, oldpte, >> + max_nr, flags, NULL, NULL, NULL); >> return ret; >> + } >> if (folio_use_access_time(folio)) >> folio_xchg_access_time(folio, >> jiffies_to_msecs(jiffies)); >> @@ -159,6 +168,7 @@ 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; >> >> tlb_change_page_size(tlb, PAGE_SIZE); >> pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); >> @@ -173,8 +183,10 @@ static long change_pte_range(struct mmu_gather *tlb, >> flush_tlb_batched_pending(vma->vm_mm); >> arch_enter_lazy_mmu_mode(); >> do { >> + nr = 1; > > 'nr' resets each iteration. > >> oldpte = ptep_get(pte); >> if (pte_present(oldpte)) { >> + int max_nr = (end - addr) >> PAGE_SHIFT; > > Small nit - 'max_nr' declaration could be moved earlier along with 'nr'. Sure. > >> pte_t ptent; >> >> /* >> @@ -182,8 +194,9 @@ static long change_pte_range(struct mmu_gather *tlb, >> * pages. See similar comment in change_huge_pmd. >> */ >> if (prot_numa && >> - prot_numa_avoid_fault(vma, addr, >> - oldpte, target_node)) >> + prot_numa_avoid_fault(vma, addr, pte, >> + oldpte, target_node, >> + max_nr, &nr)) >> continue; >> >> oldpte = ptep_modify_prot_start(vma, addr, pte); >> @@ -300,7 +313,7 @@ static long change_pte_range(struct mmu_gather *tlb, >> pages++; >> } >> } >> - } while (pte++, addr += PAGE_SIZE, addr != end); >> + } while (pte += nr, addr += nr * PAGE_SIZE, addr != end); >> arch_leave_lazy_mmu_mode(); >> pte_unmap_unlock(pte - 1, ptl); >> > > Otherwise LGTM