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 128B624EAB3 for ; Tue, 29 Apr 2025 06:54:51 +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=1745909694; cv=none; b=JXxR3wnKXsv9LDFW40phXyugquzjpbmrATMuK1z5kDM9Z6HloAgdz8ml8mz4vabZooYF9vPBIXDRUC/+Oyu/RXX8qmP2xn0WHwFOCqGbFv1zCNYKcwDSfLCwUZjCwtYH0VYGYOhPx/tlp0kfBuZwcIK56iH9GPYsV/msdfcZ/Bg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745909694; c=relaxed/simple; bh=yAfxxEt3u2cGWEC1v5XC7vdbYm+8s7aIBUQAa+eMuVM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=tAEQNJb9KSN64JwXfmFaAZzhZckmsF4XG1r/PfxE01LFwYbxCDB2+9cDHQsN7/CkukmpTA519qJh9ynFIG3nEnqJR/2NPA8b/oLgIIk+/TZugq9ZPb9pYaZ/iwfQGGZ+meRqRtulCIYNvw50qVHsUryyBR3qFWRRGgUmsaUqlNg= 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 7693D1515; Mon, 28 Apr 2025 23:54:44 -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 647323F5A1; Mon, 28 Apr 2025 23:54:41 -0700 (PDT) Message-ID: Date: Tue, 29 Apr 2025 12:24:37 +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 1/7] mm: Refactor code in mprotect 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> <20250429052336.18912-2-dev.jain@arm.com> <43dc2d0b-1ce9-4d56-a260-d1dfc4545c99@arm.com> Content-Language: en-US From: Dev Jain In-Reply-To: <43dc2d0b-1ce9-4d56-a260-d1dfc4545c99@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 29/04/25 12:11 pm, Anshuman Khandual wrote: > > > On 4/29/25 10:53, Dev Jain wrote: >> Reduce indentation in change_pte_range() by refactoring some of the code >> into a new function. No functional change. >> >> Signed-off-by: Dev Jain >> --- >> mm/mprotect.c | 116 +++++++++++++++++++++++++++++--------------------- >> 1 file changed, 68 insertions(+), 48 deletions(-) >> >> diff --git a/mm/mprotect.c b/mm/mprotect.c >> index 88608d0dc2c2..70f59aa8c2a8 100644 >> --- a/mm/mprotect.c >> +++ b/mm/mprotect.c >> @@ -83,6 +83,71 @@ bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, >> return pte_dirty(pte); >> } >> >> + >> + >> +static bool prot_numa_skip(struct vm_area_struct *vma, struct folio *folio, >> + int target_node) >> +{ >> + bool toptier; >> + int nid; >> + >> + /* Also skip shared copy-on-write pages */ >> + if (is_cow_mapping(vma->vm_flags) && >> + (folio_maybe_dma_pinned(folio) || >> + folio_maybe_mapped_shared(folio))) >> + return true; >> + >> + /* >> + * 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)) >> + return true; >> + >> + /* >> + * Don't mess with PTEs if page is already on the node >> + * a single-threaded process is running on. >> + */ >> + nid = folio_nid(folio); >> + if (target_node == nid) >> + return true; >> + toptier = node_is_toptier(nid); >> + >> + /* >> + * Skip scanning top tier node if normal numa >> + * balancing is disabled >> + */ >> + if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) && >> + toptier) >> + return true; >> + return false; >> +} >> + >> +static bool prot_numa_avoid_fault(struct vm_area_struct *vma, >> + unsigned long addr, pte_t oldpte, int target_node) >> +{ >> + struct folio *folio; >> + int ret; >> + >> + /* Avoid TLB flush if possible */ >> + if (pte_protnone(oldpte)) >> + return true; >> + >> + folio = vm_normal_folio(vma, addr, oldpte); >> + if (!folio || folio_is_zone_device(folio) || >> + folio_test_ksm(folio)) >> + return true; >> + ret = prot_numa_skip(vma, folio, target_node); > > What purpose does it solve to create additional helper prot_numa_skip(). > IOW - why cannot all of these be inside prot_numa_avoid_fault() itself. That is in preparation for patch 2, so that I can skip a PTE batch. > >> + if (ret) >> + return ret; >> + if (folio_use_access_time(folio)) >> + folio_xchg_access_time(folio, >> + jiffies_to_msecs(jiffies)); >> + return false; >> +} >> + >> 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) >> @@ -116,56 +181,11 @@ static long change_pte_range(struct mmu_gather *tlb, >> * Avoid trapping faults against the zero or KSM >> * 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 = 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)) >> + if (prot_numa && >> + prot_numa_avoid_fault(vma, addr, >> + oldpte, target_node)) >> continue; >> >> - /* >> - * Don't mess with PTEs if page is already on the node >> - * a single-threaded process is running on. >> - */ >> - nid = folio_nid(folio); >> - if (target_node == nid) >> - continue; >> - toptier = node_is_toptier(nid); >> - >> - /* >> - * Skip scanning top tier node if normal numa >> - * balancing is disabled >> - */ >> - if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) && >> - toptier) >> - continue; >> - if (folio_use_access_time(folio)) >> - folio_xchg_access_time(folio, >> - jiffies_to_msecs(jiffies)); >> - } >> - >> oldpte = ptep_modify_prot_start(vma, addr, pte); >> ptent = pte_modify(oldpte, newprot); >>