From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 09D2DC83F25 for ; Tue, 22 Jul 2025 11:26:16 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 98C716B00A9; Tue, 22 Jul 2025 07:26:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 93D286B00AA; Tue, 22 Jul 2025 07:26:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 87A706B00AB; Tue, 22 Jul 2025 07:26:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 794BF6B00A9 for ; Tue, 22 Jul 2025 07:26:15 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 26008130B35 for ; 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s=arc-20220608; d=hostedemail.com; t=1753183573; a=rsa-sha256; cv=none; b=1Gj/finj9fXhN/bIRFfOuyqNL/B1AIBe70z3uvyzkrJTY1bD+0QvtAWLhsxRvwpgh1USEF uYB4Hv380tHFQEZW/dDKXEhPLbU9junIu7uzIOw53VfQeCXdiFAWzasFv99n774rjdyDqO RLE6C8AN0dMAxUvStmgevmHQ8mtoLt4= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf01.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@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 5BE64152B; Tue, 22 Jul 2025 04:26:07 -0700 (PDT) Received: from [10.1.30.167] (XHFQ2J9959.cambridge.arm.com [10.1.30.167]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CD9293F66E; Tue, 22 Jul 2025 04:26:09 -0700 (PDT) Message-ID: <3b105623-95c2-4d4b-b49f-dd087eaa652b@arm.com> Date: Tue, 22 Jul 2025 12:26:08 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 2/7] mm: Optimize mprotect() for MM_CP_PROT_NUMA 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: <20250718090244.21092-1-dev.jain@arm.com> <20250718090244.21092-3-dev.jain@arm.com> From: Ryan Roberts In-Reply-To: <20250718090244.21092-3-dev.jain@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 70A9740007 X-Rspam-User: X-Rspamd-Server: rspam09 X-Stat-Signature: ysn93w9qmo6sg9n6pco5npixt8i4hgpn X-HE-Tag: 1753183573-395179 X-HE-Meta: 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 yqUNUfRT 0hYoltBUKyxl7tzO082BNeVqNY/QZF0rckBQNmeVp9xL/nelQs5Hk6fsZmsPFP3Zz20Usq4XkUH7Oui7sA2HwvHtHW6/DMhZrTqX5iZmL80SPPLFncvBp7iUIXLPMRCN6LCrwL98A63ZliShn1DHWDcQUY3k3lhi8+/kbXItfgVqxtYogTofpfSknk4JzKleIxixJh1JEsAFbpyeQ3jR+paFNWAH/eyMp0X+TyA0ZZVyDuzWJK/lEA+WxpQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 18/07/2025 10:02, Dev Jain wrote: > For the MM_CP_PROT_NUMA skipping case, observe that, if we skip an > iteration due to the underlying folio satisfying any of the skip > conditions, then for all subsequent ptes which map the same folio, the > iteration will be skipped for them too. Therefore, we can optimize > by using folio_pte_batch() to batch skip the iterations. > > Use prot_numa_skip() introduced in the previous patch to determine whether > we need to skip the iteration. Change its signature to have a double > pointer to a folio, which will be used by mprotect_folio_pte_batch() to > determine the number of iterations we can safely skip. > > Signed-off-by: Dev Jain LGTM: Reviewed-by: Ryan Roberts > --- > mm/mprotect.c | 55 +++++++++++++++++++++++++++++++++++++++------------ > 1 file changed, 42 insertions(+), 13 deletions(-) > > diff --git a/mm/mprotect.c b/mm/mprotect.c > index 2a9c73bd0778..97adc62c50ab 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -83,28 +83,43 @@ bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, > return pte_dirty(pte); > } > > +static int mprotect_folio_pte_batch(struct folio *folio, pte_t *ptep, > + pte_t pte, int max_nr_ptes) > +{ > + /* No underlying folio, so cannot batch */ > + if (!folio) > + return 1; > + > + if (!folio_test_large(folio)) > + return 1; > + > + return folio_pte_batch(folio, ptep, pte, max_nr_ptes); > +} > + > static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long addr, > - pte_t oldpte, pte_t *pte, int target_node) > + pte_t oldpte, pte_t *pte, int target_node, > + struct folio **foliop) > { > - struct folio *folio; > + struct folio *folio = NULL; > + bool ret = true; > bool toptier; > int nid; > > /* Avoid TLB flush if possible */ > if (pte_protnone(oldpte)) > - return true; > + goto skip; > > folio = vm_normal_folio(vma, addr, oldpte); > if (!folio) > - return true; > + goto skip; > > if (folio_is_zone_device(folio) || folio_test_ksm(folio)) > - return true; > + goto skip; > > /* 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; > + goto skip; > > /* > * While migration can move some dirty pages, > @@ -112,7 +127,7 @@ static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long addr, > * context. > */ > if (folio_is_file_lru(folio) && folio_test_dirty(folio)) > - return true; > + goto skip; > > /* > * Don't mess with PTEs if page is already on the node > @@ -120,7 +135,7 @@ static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long addr, > */ > nid = folio_nid(folio); > if (target_node == nid) > - return true; > + goto skip; > > toptier = node_is_toptier(nid); > > @@ -129,11 +144,15 @@ static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long addr, > * balancing is disabled > */ > if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) && toptier) > - return true; > + goto skip; > > + ret = false; > if (folio_use_access_time(folio)) > folio_xchg_access_time(folio, jiffies_to_msecs(jiffies)); > - return false; > + > +skip: > + *foliop = folio; > + return ret; > } > > static long change_pte_range(struct mmu_gather *tlb, > @@ -147,6 +166,7 @@ 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); > @@ -161,8 +181,11 @@ 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; > + struct folio *folio; > pte_t ptent; > > /* > @@ -170,9 +193,15 @@ static long change_pte_range(struct mmu_gather *tlb, > * pages. See similar comment in change_huge_pmd. > */ > if (prot_numa) { > - if (prot_numa_skip(vma, addr, oldpte, pte, > - target_node)) > + int ret = prot_numa_skip(vma, addr, oldpte, pte, > + target_node, &folio); > + if (ret) { > + > + /* determine batch to skip */ > + nr_ptes = mprotect_folio_pte_batch(folio, > + pte, oldpte, max_nr_ptes); > continue; > + } > } > > oldpte = ptep_modify_prot_start(vma, addr, pte); > @@ -289,7 +318,7 @@ 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); >