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Wed, 15 Oct 2025 16:50:28 +0800 (CST) Received: from dggpemf100008.china.huawei.com (unknown [7.185.36.138]) by mail.maildlp.com (Postfix) with ESMTPS id 7C1101400CA; Wed, 15 Oct 2025 16:50:48 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemf100008.china.huawei.com (7.185.36.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 15 Oct 2025 16:50:47 +0800 Message-ID: Date: Wed, 15 Oct 2025 16:50:44 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/3] mm: mprotect: avoid unnecessary struct page accessing if pte_protnone() To: Dev Jain , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , CC: Zi Yan , Baolin Wang , Ryan Roberts , Barry Song , Lance Yang , , Sidhartha Kumar References: <20251014113349.2618158-1-wangkefeng.wang@huawei.com> <20251014113349.2618158-3-wangkefeng.wang@huawei.com> <1562a70d-6778-41cb-be30-c83ca7eab373@arm.com> Content-Language: en-US From: Kefeng Wang In-Reply-To: <1562a70d-6778-41cb-be30-c83ca7eab373@arm.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To dggpemf100008.china.huawei.com (7.185.36.138) X-Rspamd-Server: rspam01 X-Stat-Signature: ogyupsh9zdybz1p76qxh3y7cj5fyijo1 X-Rspam-User: X-Rspamd-Queue-Id: 2DF99160010 X-HE-Tag: 1760518252-527349 X-HE-Meta: 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 zXEusKGA z7xv/hvDTE4eg2r7DEzSeA+Cw7h57g7UZhEmgbWIkdcpIasMq2TKfa8INnOlLjx88vVTtZVb6vjdr4bbWyloKnWYky+nhipkO9gefUppM2mzO/ZfZSiFXBLMXfYuuehJzFMKuCdccuzIaGCcn96TzqmzVkyhl5PA+vQi7AUFDqRgOzbow4j8l0aq0etTRvyLWUAkHFPtuWPXIkSN3j/2VTAoqjeYqZNBL5bGtHPQhJM39/rFy4H9EfTCNq55nzSL6eahPC0BcZsUYgOyXBHv1NBhcMKWvT0E7JGRu6UpsJoFiC0BEi/5VEltSDPqHOyQxsjLOzQKo1tjuDwGj960MSX5rJLj1dZQe3MHGE168eGo5lGQLQxungWsr2jwt/7aPCTh4dXzz0QEZa18CeWUmuglkVrIuYl3WwZI0G00Avt0TB39R6TMEmWbSQA== 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 2025/10/15 15:32, Dev Jain wrote: > > On 14/10/25 5:03 pm, Kefeng Wang wrote: >> If the pte_protnone() is true, we could avoid unnecessary struct page >> accessing and reduce cache footprint when scanning page tables for prot >> numa, the performance test of pmbench memory accessing benchmark >> should be benifit, see more commit a818f5363a0e ("autonuma: reduce cache >> footprint when scanning page tables"). >> >> Reviewed-by: Sidhartha Kumar >> Signed-off-by: Kefeng Wang >> --- > > Thanks. > >>   mm/mprotect.c | 29 ++++++++++++----------------- >>   1 file changed, 12 insertions(+), 17 deletions(-) >> >> diff --git a/mm/mprotect.c b/mm/mprotect.c >> index bb59a42809b8..7affa88a6de7 100644 >> --- a/mm/mprotect.c >> +++ b/mm/mprotect.c >> @@ -118,18 +118,13 @@ static int mprotect_folio_pte_batch(struct folio >> *folio, pte_t *ptep, >>       return folio_pte_batch_flags(folio, NULL, ptep, &pte, >> max_nr_ptes, flags); >>   } >> -static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long >> addr, >> -               pte_t oldpte, pte_t *pte, int target_node, >> -               struct folio *folio) >> +static bool prot_numa_skip(struct vm_area_struct *vma, int target_node, >> +        struct folio *folio) >>   { >>       bool ret = true; >>       bool toptier; >>       int nid; >> -    /* Avoid TLB flush if possible */ >> -    if (pte_protnone(oldpte)) >> -        goto skip; >> - >>       if (!folio) >>           goto skip; >> @@ -307,23 +302,23 @@ static long change_pte_range(struct mmu_gather >> *tlb, >>               struct page *page; >>               pte_t ptent; >> +            /* Already in the desired state. */ >> +            if (prot_numa && pte_protnone(oldpte)) >> +                continue; >> + >>               page = vm_normal_page(vma, addr, oldpte); >>               if (page) >>                   folio = page_folio(page); >> + > > Unrelated change but I guess this is needed since we usually leave a line > before starting a comment. > >>               /* >>                * Avoid trapping faults against the zero or KSM >>                * pages. See similar comment in change_huge_pmd. >>                */ >> -            if (prot_numa) { >> -                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, /* flags = */ 0); >> -                    continue; >> -                } >> +            if (prot_numa & prot_numa_skip(vma, target_node, folio)) { > > Why not "&&" instead of "&"? oops，will fix it. > >> +                /* determine batch to skip */ >> +                nr_ptes = mprotect_folio_pte_batch(folio, >> +                      pte, oldpte, max_nr_ptes, /* flags = */ 0); >> +                continue; >>               } >>               nr_ptes = mprotect_folio_pte_batch(folio, pte, oldpte, >> max_nr_ptes, flags); >