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bh=HEQV6wqvGRAIoOz+/bA80TdRTCSdvCmyE7QBXz5PKXM=; b=rReN+kKktQSHVXFOAcAr6jebSx7d/MDvO94NaH4ryYA6M1aMOWl7OgEUFwYWQT0MEk0BDb HciZOAoC1wQVZRfvwJV1KOb1ouAYHsFQP6GrpQT202IDHb+mSjbJdlPOOEvZD8jTRRADSd Y0urlWSkOel9EhboL4Iy3r+AAMjtFHQ= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf02.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 425C92B; Wed, 30 Apr 2025 00:07:46 -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 BB5363F5A1; Wed, 30 Apr 2025 00:07:43 -0700 (PDT) Message-ID: Date: Wed, 30 Apr 2025 12:37:39 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/7] Optimize mprotect for large folios To: Lance Yang , 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> Content-Language: en-US From: Dev Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 986AE80013 X-Stat-Signature: ayyn4t6wr9cizuykk6k37h7eo1zupedo X-Rspam-User: X-HE-Tag: 1745996874-903133 X-HE-Meta: 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 kF49zXSV KKmc0UsUdqfSmNMwVXCiKWz4nsVXq1qaF77+hyt/Kt1VTU4Lwrwx/1tm2G2G42195hY5CNC3YoZNN52mF6x1x4KE6FFrxyQMX+YeUdo7xIf3m9wMBZ7HMIq1UZa8WYRgTsoW3rJhh5u1dfb91L+CQsTzG5b7ycL02Y4s/X74dLXpYm8E= 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 30/04/25 11:52 am, Lance Yang wrote: > > > 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" I thought this was the default, but thanks Lance! > > 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(-) >>>>>> >>>>> >>>> >> >