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 51BEC13A3F7 for ; Tue, 29 Apr 2025 07:14:41 +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=1745910884; cv=none; b=MW2zYbIKGqFH617eXaqaj3dzC0M3WmZPiuaN59IpYlpGvqequ3061lDLRpJZBx3prfBYzPWqtTIYG5nyBAttZIv7HuQnGyCgENIG31f0VMUWfUUKDKV8KmUTHkJpCqiMI7iV4tIXYa6LlTX2BXoF8SzaLlhUtkifkz4cFgMFdpo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745910884; c=relaxed/simple; bh=/F0rwoASJN4cJrSqXtppk1kQTiKS/PN8CxIcPjZzTOE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qKfFUfISBI4N0a8UWilFAzpBZbt7JOrOMkBb/DeTbGimeulXtwJB8SS9Qv9vQuY6msarr5dB7PGhCLDW0IQOBEE+vYxObHW5/N30fehe1yeYN5sshMshtDGo4oWuq61LKLxp/+wyVmW98aPRODO5yvyGpbtJNr7l8zSdeF/XoGs= 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 AB2411515; Tue, 29 Apr 2025 00:14:34 -0700 (PDT) Received: from [10.163.52.122] (unknown [10.163.52.122]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 51CD23F5A1; Tue, 29 Apr 2025 00:14:31 -0700 (PDT) Message-ID: Date: Tue, 29 Apr 2025 12:44:27 +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: Dev Jain , 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: Anshuman Khandual In-Reply-To: <20250429052336.18912-3-dev.jain@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 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). > /* 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'. > 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