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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6F980C2BD09 for ; Mon, 24 Jun 2024 14:31:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:CC:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=BBSJ2PgiKbWVEkMyLRZPRu2UoMqvQ6nNoh7jyH/mO8k=; b=3Zj6RmrRIXWcpeNXv3q9uXKG4v 7u+p8IuQcTTTa5jqUJt3Pvw/hlrnBFUJiUqb3Tp1Yxd3IUl41ZjkST8hgu1puhbv/elNk5EPydrn9 i92IyJ5Pbj/cM0SDw0vaEI/pUk/AUg2g91wDXueUGzSH5AtFDH/OE2KpfcKn8sb2LRKm9wNonKpdA TNV3u8ESYMo8AKzSo3q/2yOP+VHL73PRXYxb5LZsY5RteiUxiZok70lXcG4kVmLwgOEmDxCIzC3Ij Ihhg6Zh8My4ZDAFZQ7me6OcVw7Tk0frjSSYhK9R1LsEop7OEAKYcNgo17e8gg8KchkeI4rHmtJoaA RasQl5oA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sLkiw-0000000H6Gw-3rbY; Mon, 24 Jun 2024 14:31:14 +0000 Received: from szxga02-in.huawei.com ([45.249.212.188]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sLkiq-0000000H6CS-2Zxe for linux-arm-kernel@lists.infradead.org; Mon, 24 Jun 2024 14:31:10 +0000 Received: from mail.maildlp.com (unknown [172.19.88.105]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4W79ML6fkQzddS9; Mon, 24 Jun 2024 22:29:18 +0800 (CST) Received: from dggpemf100008.china.huawei.com (unknown [7.185.36.138]) by mail.maildlp.com (Postfix) with ESMTPS id F0305140156; Mon, 24 Jun 2024 22:30:51 +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; Mon, 24 Jun 2024 22:30:50 +0800 Message-ID: <1285eb59-fcc3-4db8-9dd9-e7c4d82b1be0@huawei.com> Date: Mon, 24 Jun 2024 22:30:50 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 18/18] arm64/mm: Automatically fold contpte mappings Content-Language: en-US To: Ryan Roberts , Catalin Marinas , Will Deacon , Ard Biesheuvel , Marc Zyngier , James Morse , Andrey Ryabinin , Andrew Morton , Matthew Wilcox , Mark Rutland , David Hildenbrand , John Hubbard , Zi Yan , Barry Song <21cnbao@gmail.com>, Alistair Popple , Yang Shi , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" CC: , , , , References: <20240215103205.2607016-1-ryan.roberts@arm.com> <20240215103205.2607016-19-ryan.roberts@arm.com> From: Kefeng Wang In-Reply-To: <20240215103205.2607016-19-ryan.roberts@arm.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemf100008.china.huawei.com (7.185.36.138) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240624_073109_043231_9C5E61D0 X-CRM114-Status: GOOD ( 40.15 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Ryan, A big regression on page-fault3("Separate file shared mapping page fault") testcase from will-it-scale on arm64, no issue on x86, ./page_fault3_processes -t 128 -s 5 1) large folio disabled on ext4: 92378735 2) large folio enabled on ext4 + CONTPTE enabled 16164943 3) large folio enabled on ext4 + CONTPTE disabled 80364074 4) large folio enabled on ext4 + CONTPTE enabled + large folio mapping enabled in finish_fault()[2] 299656874 We found *contpte_convert* consume lots of CPU(76%) in case 2), and disparaged by following change[2], it is easy to understood the different between case 2) and case 4) since case 2) always map one page size, but always try to fold contpte mappings, which spend a lot of time. Case 4) is a workaround, any other better suggestion? Thanks. [1] https://github.com/antonblanchard/will-it-scale [2] enable large folio mapping in finish_fault() diff --git a/mm/memory.c b/mm/memory.c index 00728ea95583..5623a8ce3a1e 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4880,7 +4880,7 @@ vm_fault_t finish_fault(struct vm_fault *vmf) * approach also applies to non-anonymous-shmem faults to avoid * inflating the RSS of the process. */ - if (!vma_is_anon_shmem(vma) || unlikely(userfaultfd_armed(vma))) { + if (unlikely(userfaultfd_armed(vma))) { nr_pages = 1; } else if (nr_pages > 1) { pgoff_t idx = folio_page_idx(folio, page); On 2024/2/15 18:32, Ryan Roberts wrote: > There are situations where a change to a single PTE could cause the > contpte block in which it resides to become foldable (i.e. could be > repainted with the contiguous bit). Such situations arise, for example, > when user space temporarily changes protections, via mprotect, for > individual pages, such can be the case for certain garbage collectors. > > We would like to detect when such a PTE change occurs. However this can > be expensive due to the amount of checking required. Therefore only > perform the checks when an indiviual PTE is modified via mprotect > (ptep_modify_prot_commit() -> set_pte_at() -> set_ptes(nr=1)) and only > when we are setting the final PTE in a contpte-aligned block. > > Signed-off-by: Ryan Roberts > --- > arch/arm64/include/asm/pgtable.h | 26 +++++++++++++ > arch/arm64/mm/contpte.c | 64 ++++++++++++++++++++++++++++++++ > 2 files changed, 90 insertions(+) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 8310875133ff..401087e8a43d 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -1185,6 +1185,8 @@ extern void ptep_modify_prot_commit(struct vm_area_struct *vma, > * where it is possible and makes sense to do so. The PTE_CONT bit is considered > * a private implementation detail of the public ptep API (see below). > */ > +extern void __contpte_try_fold(struct mm_struct *mm, unsigned long addr, > + pte_t *ptep, pte_t pte); > extern void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr, > pte_t *ptep, pte_t pte); > extern pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte); > @@ -1206,6 +1208,29 @@ extern int contpte_ptep_set_access_flags(struct vm_area_struct *vma, > unsigned long addr, pte_t *ptep, > pte_t entry, int dirty); > > +static __always_inline void contpte_try_fold(struct mm_struct *mm, > + unsigned long addr, pte_t *ptep, pte_t pte) > +{ > + /* > + * Only bother trying if both the virtual and physical addresses are > + * aligned and correspond to the last entry in a contig range. The core > + * code mostly modifies ranges from low to high, so this is the likely > + * the last modification in the contig range, so a good time to fold. > + * We can't fold special mappings, because there is no associated folio. > + */ > + > + const unsigned long contmask = CONT_PTES - 1; > + bool valign = ((addr >> PAGE_SHIFT) & contmask) == contmask; > + > + if (unlikely(valign)) { > + bool palign = (pte_pfn(pte) & contmask) == contmask; > + > + if (unlikely(palign && > + pte_valid(pte) && !pte_cont(pte) && !pte_special(pte))) > + __contpte_try_fold(mm, addr, ptep, pte); > + } > +} > + > static __always_inline void contpte_try_unfold(struct mm_struct *mm, > unsigned long addr, pte_t *ptep, pte_t pte) > { > @@ -1286,6 +1311,7 @@ static __always_inline void set_ptes(struct mm_struct *mm, unsigned long addr, > if (likely(nr == 1)) { > contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); > __set_ptes(mm, addr, ptep, pte, 1); > + contpte_try_fold(mm, addr, ptep, pte); > } else { > contpte_set_ptes(mm, addr, ptep, pte, nr); > } > diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c > index 50e0173dc5ee..16788f07716d 100644 > --- a/arch/arm64/mm/contpte.c > +++ b/arch/arm64/mm/contpte.c > @@ -73,6 +73,70 @@ static void contpte_convert(struct mm_struct *mm, unsigned long addr, > __set_ptes(mm, start_addr, start_ptep, pte, CONT_PTES); > } > > +void __contpte_try_fold(struct mm_struct *mm, unsigned long addr, > + pte_t *ptep, pte_t pte) > +{ > + /* > + * We have already checked that the virtual and pysical addresses are > + * correctly aligned for a contpte mapping in contpte_try_fold() so the > + * remaining checks are to ensure that the contpte range is fully > + * covered by a single folio, and ensure that all the ptes are valid > + * with contiguous PFNs and matching prots. We ignore the state of the > + * access and dirty bits for the purpose of deciding if its a contiguous > + * range; the folding process will generate a single contpte entry which > + * has a single access and dirty bit. Those 2 bits are the logical OR of > + * their respective bits in the constituent pte entries. In order to > + * ensure the contpte range is covered by a single folio, we must > + * recover the folio from the pfn, but special mappings don't have a > + * folio backing them. Fortunately contpte_try_fold() already checked > + * that the pte is not special - we never try to fold special mappings. > + * Note we can't use vm_normal_page() for this since we don't have the > + * vma. > + */ > + > + unsigned long folio_start, folio_end; > + unsigned long cont_start, cont_end; > + pte_t expected_pte, subpte; > + struct folio *folio; > + struct page *page; > + unsigned long pfn; > + pte_t *orig_ptep; > + pgprot_t prot; > + > + int i; > + > + if (!mm_is_user(mm)) > + return; > + > + page = pte_page(pte); > + folio = page_folio(page); > + folio_start = addr - (page - &folio->page) * PAGE_SIZE; > + folio_end = folio_start + folio_nr_pages(folio) * PAGE_SIZE; > + cont_start = ALIGN_DOWN(addr, CONT_PTE_SIZE); > + cont_end = cont_start + CONT_PTE_SIZE; > + > + if (folio_start > cont_start || folio_end < cont_end) > + return; > + > + pfn = ALIGN_DOWN(pte_pfn(pte), CONT_PTES); > + prot = pte_pgprot(pte_mkold(pte_mkclean(pte))); > + expected_pte = pfn_pte(pfn, prot); > + orig_ptep = ptep; > + ptep = contpte_align_down(ptep); > + > + for (i = 0; i < CONT_PTES; i++) { > + subpte = pte_mkold(pte_mkclean(__ptep_get(ptep))); > + if (!pte_same(subpte, expected_pte)) > + return; > + expected_pte = pte_advance_pfn(expected_pte, 1); > + ptep++; > + } > + > + pte = pte_mkcont(pte); > + contpte_convert(mm, addr, orig_ptep, pte); > +} > +EXPORT_SYMBOL(__contpte_try_fold); > + > void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr, > pte_t *ptep, pte_t pte) > {