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s=arc-20220608; d=hostedemail.com; t=1745991779; a=rsa-sha256; cv=none; b=zHV6T+ff7+PyNS7CdEZJF3AmqL9p0yy1GN6hOkdjbXtsu75FgRUdcKXs3KpeFdCPUYiezV dmXGnyYsqUZkLvW9DLu6Gjye6a2SfV1PZpbJhWOWp4nV5ptO5ATD3NbV2brXD0axy8X120 zb9KDcapD1nbkuAlCqfu79xVq/0DiCs= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf06.hostedemail.com: domain of dev.jain@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=dev.jain@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 E2C0F106F; Tue, 29 Apr 2025 22:42:50 -0700 (PDT) Received: from [10.163.79.251] (unknown [10.163.79.251]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CB7653F5A1; Tue, 29 Apr 2025 22:42:48 -0700 (PDT) Message-ID: <11f86b1c-a12e-4cd3-8b4e-a8a34c64fbf1@arm.com> Date: Wed, 30 Apr 2025 11:12:45 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/7] Optimize mprotect for large folios To: Lorenzo Stoakes Cc: Lance Yang , 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> Content-Language: en-US From: Dev Jain In-Reply-To: <9d995850-d0c4-4e02-8547-74a9723e0405@lucifer.local> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 2D7AD180007 X-Rspam-User: X-Stat-Signature: 1ajrawqoysryobs8tnaib518xd8iiuth X-HE-Tag: 1745991778-730398 X-HE-Meta: U2FsdGVkX19vhADFMHuWKO4K8mz890eYzME+ooNirNpsBE14Owd9vWYC4UnWftB/ZoUdnmtQXhEvsTLOXQ3AWNgFz1pfaAdQ+BJ7UPUWvMMhzUcNR9V4Cl7ytypRAvBERTW5hqnY3lHx7NA+MQE0Kg8BbvcXR1bMVRgaz48Vsf/PpQOSpHY04i/aTR6iULy579QRj5/NveFRz9YxFXt9EyUxWkGeCwYKsU8i6KKVEvCLuhqQHr//FI8WiSYreJSIwIXJ/S+8ZHJMKR5G2gPXbOjkWVNlm2vDpaQOLaRhQr+BmBphfGdq/fExdWvh+AgSkDb29EjEI6XpUm9dnsjpn2KFLGciAKYmn+NQe/J85ToilZhhV8VZYl/iluBd42fjGc/hFGslx60oLO5Vkf9947zqU42JKl+2TuRJgyEVz0hYi6y1EWCWbJjHiINnucNGbNeo2QjxhV004ND+q7V8/5pgyI27iOdc+yHlFIRujzeZBTUhzQUq2E1FrkJcfbN7Sy1SgszEraYmywPBfWkrt/SvqEinl6q7ma/L+Hd+PbJaxavHAEY3bV2rpQdLEfmyOtJZkd49UAyXMViLOvqoQFM6exhS9GIBYQM5gO3yJeWFoMQTh3mGOidybkpbBPubJuD092b+zrtwzzye5Z7nC3UxNvRsM6r/pQ7sTfREYCtLXh6RZLKvsbtOEkx16NaavbvS2AubM6oTU3DxIj0QZHZFTaq29gNeVJ9AKdov8zeFHLRrF8563UHsoSZ/rKy0K51VQS9M8Hl4PL86bDyGUb03k9LTFkQ86mdP8S+PozOsANtnd0r1LKs6BoT7K5dheyIATtfY74rGxnrju9057mCIBctqEeYHqJFsVhfLg/tZ7i+RNuvmkJF7Cr7J8OWxL5G6Oqd0ZF0pL/CYYZeYlhjx5ddIyAVtxVsxB/g5vITczIme8L2ESzFJeraGpEzFyjUJLBwEkpwGOjkedGc XXbpgDB5 yN/IGQzOKaQBSCKJ3c1V63xrqdv4vjR5zS3iG+nTkYL5zHfqENytBwXfr0NCBOG+o5kE/9yuFTue2JrsvON+X1Z89rmcKkABRMf4wwEulUF+8pT+gutfAKhragS3mBtDipSPRzsKXoH7hNdx3Tkvp6FHEVeU/KMCj19pkPQOV6dDkvVU= 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 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: > > 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. > > 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(-) >>>> >>> >>