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 9174FC369D9 for ; Wed, 30 Apr 2025 06:25:21 +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=TicTVOmEB3gnVmsnSxlET08PtUTAw7ExU8QRHiIKy9o=; b=soqkRwRKyp48mbvvMFmYps2eYr Maan4yFLncoCE3ebftVtIalH3l9+lE9aa3LB3G8/PJGZaxSGl1WYYXxSSJESLhmO3GTGUIzItnwM+ u60tb3Qj85HNlEsxz6TxErtrG0o13k2TeSFXQI+k/yNgFwPHza7TLzFD4sD/gRJ6SdFrHKorwSSTt j75mZH9lXHXi+urQ5zuqltv8/4B+XtSWgPiLsrr9Ydqwcae+quioJn0I3QD8O9qFcHORulcxO1h/m 8sYmTGpvmmWuAxCxo1wSSN5RJLVi65QxD40OiJpmakvGR5s0c8cvshHBqK8XL+7gthjbMRm/lhg3A HXD5a7jw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uA0sV-0000000BrMa-36dQ; Wed, 30 Apr 2025 06:25:07 +0000 Received: from out-189.mta0.migadu.com ([91.218.175.189]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uA0qY-0000000Br9x-40s3 for linux-arm-kernel@lists.infradead.org; Wed, 30 Apr 2025 06:23:09 +0000 Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1745994182; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TicTVOmEB3gnVmsnSxlET08PtUTAw7ExU8QRHiIKy9o=; b=Ai9ipa+swlvk6wp6hyZxKB+55UqBgEJPAgarn6r/UgjhhL+D5PngZJkXGwJI+d4l3phYyh PE71HTKiS0ULVsUSSILir4g4HXTlBXhMsV0zKCvEm23t2+10PfvU1orBDbXD5Hw/A+QULH ZWFyjRt0qmGuGPq+Cy6yfNTp3R+0i7k= Date: Wed, 30 Apr 2025 14:22:46 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v2 0/7] Optimize mprotect for large folios Content-Language: en-US To: Dev Jain , Lorenzo Stoakes Cc: akpm@linux-foundation.org, 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, 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, namit@vmware.com, hughd@google.com, yang@os.amperecomputing.com, ziy@nvidia.com References: <20250429052336.18912-1-dev.jain@arm.com> <05c3cd68-0d75-4682-a51c-59307e2b2e78@arm.com> <9d995850-d0c4-4e02-8547-74a9723e0405@lucifer.local> <11f86b1c-a12e-4cd3-8b4e-a8a34c64fbf1@arm.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <11f86b1c-a12e-4cd3-8b4e-a8a34c64fbf1@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250429_232307_760596_4424D0A0 X-CRM114-Status: GOOD ( 23.12 ) 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 On 2025/4/30 13:42, Dev Jain wrote: > > > On 29/04/25 4:11 pm, Lorenzo Stoakes wrote: >> FWIW can confirm the same thing. Lance's fixes sort most of it out, >> but I also >> get this error: Good catch! >> >> mm/mprotect.c: In function ‘can_change_ptes_writable’: >> mm/mprotect.c:46:22: error: unused variable ‘page’ [-Werror=unused- >> variable] >>     46 |         struct page *page; >>        |                      ^~~~ >> >> So you also need to remove this unused variable at the stop of >> can_change_ptes_writable(). > > Strange that my build didn't catch this. Well, to catch unused variable warnings with GCC, enable stricter checks by passing -Wunused-variable via KCFLAGS, and use -Werror=unused-variable to force the build to fail if any variable is declared but unused: make -j$(nproc) KCFLAGS="-Wunused-variable -Werror=unused-variable" Thanks, Lance > >> >> Cheers, Lorenzo >> >> On Tue, Apr 29, 2025 at 02:32:59PM +0530, Dev Jain wrote: >>> >>> >>> On 29/04/25 12:36 pm, Lance Yang wrote: >>>> Hey Dev, >>>> >>>> Hmm... I also hit the same compilation errors: >>>> >>>> In file included from ./include/linux/kasan.h:37, >>>>                    from ./include/linux/slab.h:260, >>>>                    from ./include/linux/crypto.h:19, >>>>                    from arch/x86/kernel/asm-offsets.c:9: >>>> ./include/linux/pgtable.h: In function ‘modify_prot_start_ptes’: >>>> ./include/linux/pgtable.h:905:15: error: implicit declaration of >>>> function ‘ptep_modify_prot_start’ >>>> [-Werror=implicit-function-declaration] >>>>     905 |         pte = ptep_modify_prot_start(vma, addr, ptep); >>>>         |               ^~~~~~~~~~~~~~~~~~~~~~ >>>> ./include/linux/pgtable.h:905:15: error: incompatible types when >>>> assigning to type ‘pte_t’ from type ‘int’ >>>> ./include/linux/pgtable.h:909:27: error: incompatible types when >>>> assigning to type ‘pte_t’ from type ‘int’ >>>>     909 |                 tmp_pte = ptep_modify_prot_start(vma, >>>> addr, ptep); >>>>         |                           ^~~~~~~~~~~~~~~~~~~~~~ >>>> ./include/linux/pgtable.h: In function ‘modify_prot_commit_ptes’: >>>> ./include/linux/pgtable.h:925:17: error: implicit declaration of >>>> function ‘ptep_modify_prot_commit’ >>>> [-Werror=implicit-function-declaration] >>>>     925 |                 ptep_modify_prot_commit(vma, addr, ptep, >>>> old_pte, pte); >>>>         |                 ^~~~~~~~~~~~~~~~~~~~~~~ >>>> ./include/linux/pgtable.h: At top level: >>>> ./include/linux/pgtable.h:1360:21: error: conflicting types for >>>> ‘ptep_modify_prot_start’; have ‘pte_t(struct vm_area_struct *, long >>>> unsigned int,  pte_t *)’ >>>>    1360 | static inline pte_t ptep_modify_prot_start(struct >>>> vm_area_struct *vma, >>>>         |                     ^~~~~~~~~~~~~~~~~~~~~~ >>>> ./include/linux/pgtable.h:905:15: note: previous implicit >>>> declaration of >>>> ‘ptep_modify_prot_start’ with type ‘int()’ >>>>     905 |         pte = ptep_modify_prot_start(vma, addr, ptep); >>>>         |               ^~~~~~~~~~~~~~~~~~~~~~ >>>> ./include/linux/pgtable.h:1371:20: warning: conflicting types for >>>> ‘ptep_modify_prot_commit’; have ‘void(struct vm_area_struct *, long >>>> unsigned int,  pte_t *, pte_t,  pte_t)’ >>>>    1371 | static inline void ptep_modify_prot_commit(struct >>>> vm_area_struct *vma, >>>>         |                    ^~~~~~~~~~~~~~~~~~~~~~~ >>>> ./include/linux/pgtable.h:1371:20: error: static declaration of >>>> ‘ptep_modify_prot_commit’ follows non-static declaration >>>> ./include/linux/pgtable.h:925:17: note: previous implicit >>>> declaration of >>>> ‘ptep_modify_prot_commit’ with type ‘void(struct vm_area_struct *, long >>>> unsigned int,  pte_t *, pte_t,  pte_t)’ >>>>     925 |                 ptep_modify_prot_commit(vma, addr, ptep, >>>> old_pte, pte); >>>>         |                 ^~~~~~~~~~~~~~~~~~~~~~~ >>>>     CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/ >>>> objtool/ >>>> libstring.o >>>>     CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/ >>>> objtool/ >>>> libctype.o >>>>     CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/ >>>> objtool/ >>>> str_error_r.o >>>>     CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/ >>>> objtool/ >>>> librbtree.o >>>> cc1: some warnings being treated as errors >>>> make[2]: *** [scripts/Makefile.build:98: arch/x86/kernel/asm-offsets.s] >>>> Error 1 >>>> make[1]: *** [/home/runner/work/mm-test-robot/mm-test-robot/linux/ >>>> Makefile:1280: prepare0] Error 2 >>>> make[1]: *** Waiting for unfinished jobs.... >>>>     LD /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/ >>>> objtool/ >>>> objtool-in.o >>>>     LINK /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/ >>>> objtool/objtool >>>> make: *** [Makefile:248: __sub-make] Error 2 >>>> >>>> Well, modify_prot_start_ptes() calls ptep_modify_prot_start(), but x86 >>>> does not define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION. To avoid >>>> implicit declaration errors, the architecture-independent >>>> ptep_modify_prot_start() must be defined before >>>> modify_prot_start_ptes(). >>>> >>>> With the changes below, things work correctly now ;) >>> >>> Ah thanks! My bad :( >>> >>>> >>>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h >>>> index 10cdb87ccecf..d9d6c49bb914 100644 >>>> --- a/include/linux/pgtable.h >>>> +++ b/include/linux/pgtable.h >>>> @@ -895,44 +895,6 @@ static inline void wrprotect_ptes(struct mm_struct >>>> *mm, unsigned long addr, >>>>    } >>>>    #endif >>>> >>>> -/* See the comment for ptep_modify_prot_start */ >>>> -#ifndef modify_prot_start_ptes >>>> -static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma, >>>> -        unsigned long addr, pte_t *ptep, unsigned int nr) >>>> -{ >>>> -    pte_t pte, tmp_pte; >>>> - >>>> -    pte = ptep_modify_prot_start(vma, addr, ptep); >>>> -    while (--nr) { >>>> -        ptep++; >>>> -        addr += PAGE_SIZE; >>>> -        tmp_pte = ptep_modify_prot_start(vma, addr, ptep); >>>> -        if (pte_dirty(tmp_pte)) >>>> -            pte = pte_mkdirty(pte); >>>> -        if (pte_young(tmp_pte)) >>>> -            pte = pte_mkyoung(pte); >>>> -    } >>>> -    return pte; >>>> -} >>>> -#endif >>>> - >>>> -/* See the comment for ptep_modify_prot_commit */ >>>> -#ifndef modify_prot_commit_ptes >>>> -static inline void modify_prot_commit_ptes(struct vm_area_struct *vma, >>>> unsigned long addr, >>>> -        pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr) >>>> -{ >>>> -    for (;;) { >>>> -        ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte); >>>> -        if (--nr == 0) >>>> -            break; >>>> -        ptep++; >>>> -        addr += PAGE_SIZE; >>>> -        old_pte = pte_next_pfn(old_pte); >>>> -        pte = pte_next_pfn(pte); >>>> -    } >>>> -} >>>> -#endif >>>> - >>>>    /* >>>>     * On some architectures hardware does not set page access bit when >>>> accessing >>>>     * memory page, it is responsibility of software setting this >>>> bit. It >>>> brings >>>> @@ -1375,6 +1337,45 @@ static inline void >>>> ptep_modify_prot_commit(struct >>>> vm_area_struct *vma, >>>>        __ptep_modify_prot_commit(vma, addr, ptep, pte); >>>>    } >>>>    #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */ >>>> + >>>> +/* See the comment for ptep_modify_prot_start */ >>>> +#ifndef modify_prot_start_ptes >>>> +static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma, >>>> +        unsigned long addr, pte_t *ptep, unsigned int nr) >>>> +{ >>>> +    pte_t pte, tmp_pte; >>>> + >>>> +    pte = ptep_modify_prot_start(vma, addr, ptep); >>>> +    while (--nr) { >>>> +        ptep++; >>>> +        addr += PAGE_SIZE; >>>> +        tmp_pte = ptep_modify_prot_start(vma, addr, ptep); >>>> +        if (pte_dirty(tmp_pte)) >>>> +            pte = pte_mkdirty(pte); >>>> +        if (pte_young(tmp_pte)) >>>> +            pte = pte_mkyoung(pte); >>>> +    } >>>> +    return pte; >>>> +} >>>> +#endif >>>> + >>>> +/* See the comment for ptep_modify_prot_commit */ >>>> +#ifndef modify_prot_commit_ptes >>>> +static inline void modify_prot_commit_ptes(struct vm_area_struct *vma, >>>> unsigned long addr, >>>> +        pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr) >>>> +{ >>>> +    for (;;) { >>>> +        ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte); >>>> +        if (--nr == 0) >>>> +            break; >>>> +        ptep++; >>>> +        addr += PAGE_SIZE; >>>> +        old_pte = pte_next_pfn(old_pte); >>>> +        pte = pte_next_pfn(pte); >>>> +    } >>>> +} >>>> +#endif >>>> + >>>>    #endif /* CONFIG_MMU */ >>>> >>>>    /* >>>> -- >>>> >>>> Thanks, >>>> Lance >>>> >>>> On 2025/4/29 13:23, Dev Jain wrote: >>>>> This patchset optimizes the mprotect() system call for large folios >>>>> by PTE-batching. >>>>> >>>>> We use the following test cases to measure performance, mprotect()'ing >>>>> the mapped memory to read-only then read-write 40 times: >>>>> >>>>> Test case 1: Mapping 1G of memory, touching it to get PMD-THPs, then >>>>> pte-mapping those THPs >>>>> Test case 2: Mapping 1G of memory with 64K mTHPs >>>>> Test case 3: Mapping 1G of memory with 4K pages >>>>> >>>>> Average execution time on arm64, Apple M3: >>>>> Before the patchset: >>>>> T1: 7.9 seconds   T2: 7.9 seconds   T3: 4.2 seconds >>>>> >>>>> After the patchset: >>>>> T1: 2.1 seconds   T2: 2.2 seconds   T3: 4.2 seconds >>>>> >>>>> Observing T1/T2 and T3 before the patchset, we also remove the >>>>> regression >>>>> introduced by ptep_get() on a contpte block. And, for large folios >>>>> we get >>>>> an almost 74% performance improvement. >>>>> >>>>> v1->v2: >>>>>    - Rebase onto mm-unstable (6ebffe676fcf: util_macros.h: make the >>>>> header more resilient) >>>>>    - Abridge the anon-exclusive condition (Lance Yang) >>>>> >>>>> Dev Jain (7): >>>>>     mm: Refactor code in mprotect >>>>>     mm: Optimize mprotect() by batch-skipping PTEs >>>>>     mm: Add batched versions of ptep_modify_prot_start/commit >>>>>     arm64: Add batched version of ptep_modify_prot_start >>>>>     arm64: Add batched version of ptep_modify_prot_commit >>>>>     mm: Batch around can_change_pte_writable() >>>>>     mm: Optimize mprotect() through PTE-batching >>>>> >>>>>    arch/arm64/include/asm/pgtable.h |  10 ++ >>>>>    arch/arm64/mm/mmu.c              |  21 +++- >>>>>    include/linux/mm.h               |   4 +- >>>>>    include/linux/pgtable.h          |  42 ++++++++ >>>>>    mm/gup.c                         |   2 +- >>>>>    mm/huge_memory.c                 |   4 +- >>>>>    mm/memory.c                      |   6 +- >>>>>    mm/mprotect.c                    | 165 +++++++++++++++++++ >>>>> +----------- >>>>>    mm/pgtable-generic.c             |  16 ++- >>>>>    9 files changed, 198 insertions(+), 72 deletions(-) >>>>> >>>> >>> >