From: Baolin Wang <baolin.wang@linux.alibaba.com> To: nh26223@qq.com, catalin.marinas@arm.com, will@kernel.org, arnd@arndb.de, mike.kravetz@oracle.com, akpm@linux-foundation.org, sj@kernel.org Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH 1/3] arm64/hugetlb: Introduce new huge_ptep_get_access_flags() interface Date: Mon, 9 May 2022 09:19:00 +0800 [thread overview] Message-ID: <5e33cf5e-2c48-89fe-3447-2f29c7844928@linux.alibaba.com> (raw) In-Reply-To: <tencent_E3DE18C8CFE150F1EDCF887146BA374E6706@qq.com> On 5/8/2022 9:14 PM, nh26223@qq.com wrote: > On 2022年5月8日星期日 CST 下午4:58:52 Baolin Wang wrote: >> Now we use huge_ptep_get() to get the pte value of a hugetlb page, >> however it will only return one specific pte value for the CONT-PTE >> or CONT-PMD size hugetlb on ARM64 system, which can contain seravel >> continuous pte or pmd entries with same page table attributes. And it >> will not take into account the subpages' dirty or young bits of a >> CONT-PTE/PMD size hugetlb page. >> >> So the huge_ptep_get() is inconsistent with huge_ptep_get_and_clear(), >> which already takes account the dirty or young bits for any subpages >> in this CONT-PTE/PMD size hugetlb [1]. Meanwhile we can miss dirty or >> young flags statistics for hugetlb pages with current huge_ptep_get(), >> such as the gather_hugetlb_stats() function. >> >> Thus introduce a new huge_ptep_get_access_flags() interface and define >> an ARM64 specific implementation, that will take into account any subpages' >> dirty or young bits for CONT-PTE/PMD size hugetlb page, for those functions >> that want to check the dirty and young flags of a hugetlb page. >> >> [1] >> https://lore.kernel.org/linux-mm/85bd80b4-b4fd-0d3f-a2e5-149559f2f387@oracl >> e.com/ >> >> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> >> --- >> arch/arm64/include/asm/hugetlb.h | 2 ++ >> arch/arm64/mm/hugetlbpage.c | 24 ++++++++++++++++++++++++ >> include/asm-generic/hugetlb.h | 7 +++++++ >> 3 files changed, 33 insertions(+) >> >> diff --git a/arch/arm64/include/asm/hugetlb.h >> b/arch/arm64/include/asm/hugetlb.h index 616b2ca..a473544 100644 >> --- a/arch/arm64/include/asm/hugetlb.h >> +++ b/arch/arm64/include/asm/hugetlb.h >> @@ -44,6 +44,8 @@ extern pte_t huge_ptep_clear_flush(struct vm_area_struct >> *vma, #define __HAVE_ARCH_HUGE_PTE_CLEAR >> extern void huge_pte_clear(struct mm_struct *mm, unsigned long addr, >> pte_t *ptep, unsigned long sz); >> +#define __HAVE_ARCH_HUGE_PTEP_GET_ACCESS_FLAGS >> +extern pte_t huge_ptep_get_access_flags(pte_t *ptep, unsigned long sz); >> extern void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr, >> pte_t *ptep, pte_t pte, unsigned long > sz); >> #define set_huge_swap_pte_at set_huge_swap_pte_at >> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c >> index ca8e65c..ce39699 100644 >> --- a/arch/arm64/mm/hugetlbpage.c >> +++ b/arch/arm64/mm/hugetlbpage.c >> @@ -158,6 +158,30 @@ static inline int num_contig_ptes(unsigned long size, >> size_t *pgsize) return contig_ptes; >> } >> >> +pte_t huge_ptep_get_access_flags(pte_t *ptep, unsigned long sz) > The function name looks to me that it returns access flags of PTE. Yes, not a good name. That's why this is a RFC patch set to get more suggestion :) Maybe huge_ptep_get_with_access_flags()? or do you have some better idea? > >> +{ >> + int ncontig, i; >> + size_t pgsize; >> + pte_t orig_pte = ptep_get(ptep); >> + >> + if (!pte_cont(orig_pte)) >> + return orig_pte; >> + >> + ncontig = num_contig_ptes(sz, &pgsize); >> + >> + for (i = 0; i < ncontig; i++, ptep++) { >> + pte_t pte = ptep_get(ptep); >> + >> + if (pte_dirty(pte)) >> + orig_pte = pte_mkdirty(orig_pte); >> + >> + if (pte_young(pte)) >> + orig_pte = pte_mkyoung(orig_pte); >> + } >> + >> + return orig_pte; >> +} > Not sure whether it's worthy being changed to: > > bool dirty = false, young = false; > > for (i = 0; i < ncontig; i++, ptep++) { > pte_t pte = ptep_get(ptep); > > if (pte_dirty(pte)) > dirty = true; > > if (pte_young(pte)) > young = true; > > if (dirty && young) > break; > } > > if (dirty) > orig_pte = pte_mkdirty(orig_pte); > > if (young) > orig_pte = pte_mkyoung(orit_pte); > > return orig_pte; I followed the same logics in get_clear_flush(), which is more readable I think. Yes, your approach can save some cycles, I can change to use it in next version if arm64 maintainers have no objection. >> + >> /* >> * Changing some bits of contiguous entries requires us to follow a >> * Break-Before-Make approach, breaking the whole contiguous set >> diff --git a/include/asm-generic/hugetlb.h b/include/asm-generic/hugetlb.h >> index a57d667..bb77fb0 100644 >> --- a/include/asm-generic/hugetlb.h >> +++ b/include/asm-generic/hugetlb.h >> @@ -150,6 +150,13 @@ static inline pte_t huge_ptep_get(pte_t *ptep) >> } >> #endif >> >> +#ifndef __HAVE_ARCH_HUGE_PTEP_GET_ACCESS_FLAGS >> +static inline pte_t huge_ptep_get_access_flags(pte_t *ptep, unsigned long >> sz) +{ >> + return ptep_get(ptep); > Should be: > return huge_ptep_get(ptep) ? I don't think so. If no ARCH-specific definition, the huge_ptep_get_access_flags() implementation should be same as huge_ptep_get(). Thanks for your comments. #ifndef __HAVE_ARCH_HUGE_PTEP_GET static inline pte_t huge_ptep_get(pte_t *ptep) { return ptep_get(ptep); } #endif
WARNING: multiple messages have this Message-ID (diff)
From: Baolin Wang <baolin.wang@linux.alibaba.com> To: nh26223@qq.com, catalin.marinas@arm.com, will@kernel.org, arnd@arndb.de, mike.kravetz@oracle.com, akpm@linux-foundation.org, sj@kernel.org Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH 1/3] arm64/hugetlb: Introduce new huge_ptep_get_access_flags() interface Date: Mon, 9 May 2022 09:19:00 +0800 [thread overview] Message-ID: <5e33cf5e-2c48-89fe-3447-2f29c7844928@linux.alibaba.com> (raw) In-Reply-To: <tencent_E3DE18C8CFE150F1EDCF887146BA374E6706@qq.com> On 5/8/2022 9:14 PM, nh26223@qq.com wrote: > On 2022年5月8日星期日 CST 下午4:58:52 Baolin Wang wrote: >> Now we use huge_ptep_get() to get the pte value of a hugetlb page, >> however it will only return one specific pte value for the CONT-PTE >> or CONT-PMD size hugetlb on ARM64 system, which can contain seravel >> continuous pte or pmd entries with same page table attributes. And it >> will not take into account the subpages' dirty or young bits of a >> CONT-PTE/PMD size hugetlb page. >> >> So the huge_ptep_get() is inconsistent with huge_ptep_get_and_clear(), >> which already takes account the dirty or young bits for any subpages >> in this CONT-PTE/PMD size hugetlb [1]. Meanwhile we can miss dirty or >> young flags statistics for hugetlb pages with current huge_ptep_get(), >> such as the gather_hugetlb_stats() function. >> >> Thus introduce a new huge_ptep_get_access_flags() interface and define >> an ARM64 specific implementation, that will take into account any subpages' >> dirty or young bits for CONT-PTE/PMD size hugetlb page, for those functions >> that want to check the dirty and young flags of a hugetlb page. >> >> [1] >> https://lore.kernel.org/linux-mm/85bd80b4-b4fd-0d3f-a2e5-149559f2f387@oracl >> e.com/ >> >> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> >> --- >> arch/arm64/include/asm/hugetlb.h | 2 ++ >> arch/arm64/mm/hugetlbpage.c | 24 ++++++++++++++++++++++++ >> include/asm-generic/hugetlb.h | 7 +++++++ >> 3 files changed, 33 insertions(+) >> >> diff --git a/arch/arm64/include/asm/hugetlb.h >> b/arch/arm64/include/asm/hugetlb.h index 616b2ca..a473544 100644 >> --- a/arch/arm64/include/asm/hugetlb.h >> +++ b/arch/arm64/include/asm/hugetlb.h >> @@ -44,6 +44,8 @@ extern pte_t huge_ptep_clear_flush(struct vm_area_struct >> *vma, #define __HAVE_ARCH_HUGE_PTE_CLEAR >> extern void huge_pte_clear(struct mm_struct *mm, unsigned long addr, >> pte_t *ptep, unsigned long sz); >> +#define __HAVE_ARCH_HUGE_PTEP_GET_ACCESS_FLAGS >> +extern pte_t huge_ptep_get_access_flags(pte_t *ptep, unsigned long sz); >> extern void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr, >> pte_t *ptep, pte_t pte, unsigned long > sz); >> #define set_huge_swap_pte_at set_huge_swap_pte_at >> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c >> index ca8e65c..ce39699 100644 >> --- a/arch/arm64/mm/hugetlbpage.c >> +++ b/arch/arm64/mm/hugetlbpage.c >> @@ -158,6 +158,30 @@ static inline int num_contig_ptes(unsigned long size, >> size_t *pgsize) return contig_ptes; >> } >> >> +pte_t huge_ptep_get_access_flags(pte_t *ptep, unsigned long sz) > The function name looks to me that it returns access flags of PTE. Yes, not a good name. That's why this is a RFC patch set to get more suggestion :) Maybe huge_ptep_get_with_access_flags()? or do you have some better idea? > >> +{ >> + int ncontig, i; >> + size_t pgsize; >> + pte_t orig_pte = ptep_get(ptep); >> + >> + if (!pte_cont(orig_pte)) >> + return orig_pte; >> + >> + ncontig = num_contig_ptes(sz, &pgsize); >> + >> + for (i = 0; i < ncontig; i++, ptep++) { >> + pte_t pte = ptep_get(ptep); >> + >> + if (pte_dirty(pte)) >> + orig_pte = pte_mkdirty(orig_pte); >> + >> + if (pte_young(pte)) >> + orig_pte = pte_mkyoung(orig_pte); >> + } >> + >> + return orig_pte; >> +} > Not sure whether it's worthy being changed to: > > bool dirty = false, young = false; > > for (i = 0; i < ncontig; i++, ptep++) { > pte_t pte = ptep_get(ptep); > > if (pte_dirty(pte)) > dirty = true; > > if (pte_young(pte)) > young = true; > > if (dirty && young) > break; > } > > if (dirty) > orig_pte = pte_mkdirty(orig_pte); > > if (young) > orig_pte = pte_mkyoung(orit_pte); > > return orig_pte; I followed the same logics in get_clear_flush(), which is more readable I think. Yes, your approach can save some cycles, I can change to use it in next version if arm64 maintainers have no objection. >> + >> /* >> * Changing some bits of contiguous entries requires us to follow a >> * Break-Before-Make approach, breaking the whole contiguous set >> diff --git a/include/asm-generic/hugetlb.h b/include/asm-generic/hugetlb.h >> index a57d667..bb77fb0 100644 >> --- a/include/asm-generic/hugetlb.h >> +++ b/include/asm-generic/hugetlb.h >> @@ -150,6 +150,13 @@ static inline pte_t huge_ptep_get(pte_t *ptep) >> } >> #endif >> >> +#ifndef __HAVE_ARCH_HUGE_PTEP_GET_ACCESS_FLAGS >> +static inline pte_t huge_ptep_get_access_flags(pte_t *ptep, unsigned long >> sz) +{ >> + return ptep_get(ptep); > Should be: > return huge_ptep_get(ptep) ? I don't think so. If no ARCH-specific definition, the huge_ptep_get_access_flags() implementation should be same as huge_ptep_get(). Thanks for your comments. #ifndef __HAVE_ARCH_HUGE_PTEP_GET static inline pte_t huge_ptep_get(pte_t *ptep) { return ptep_get(ptep); } #endif _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-05-09 1:29 UTC|newest] Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-05-08 8:58 [RFC PATCH 0/3] Introduce new huge_ptep_get_access_flags() interface Baolin Wang 2022-05-08 8:58 ` Baolin Wang 2022-05-08 8:58 ` [RFC PATCH 1/3] arm64/hugetlb: " Baolin Wang 2022-05-08 8:58 ` Baolin Wang 2022-05-08 13:14 ` nh26223 2022-05-08 13:14 ` nh26223 2022-05-09 1:19 ` Baolin Wang [this message] 2022-05-09 1:19 ` Baolin Wang 2022-05-09 4:10 ` nh26223 2022-05-09 4:10 ` nh26223 2022-05-09 4:19 ` Baolin Wang 2022-05-09 4:19 ` Baolin Wang 2022-05-08 8:58 ` [RFC PATCH 2/3] fs/proc/task_mmu: Change to use huge_ptep_get_access_flags() Baolin Wang 2022-05-08 8:58 ` Baolin Wang 2022-05-08 8:58 ` [RFC PATCH 3/3] mm/damon/vaddr: " Baolin Wang 2022-05-08 8:58 ` Baolin Wang 2022-05-08 12:41 ` kernel test robot 2022-05-08 15:26 ` [RFC PATCH 0/3] Introduce new huge_ptep_get_access_flags() interface Muchun Song 2022-05-08 15:26 ` Muchun Song 2022-05-09 1:34 ` Baolin Wang 2022-05-09 1:34 ` Baolin Wang 2022-05-08 17:08 ` Matthew Wilcox 2022-05-08 17:08 ` Matthew Wilcox 2022-05-09 1:53 ` Baolin Wang 2022-05-09 1:53 ` Baolin Wang 2022-05-09 2:54 ` Muchun Song 2022-05-09 2:54 ` Muchun Song
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