| Message ID | 20220309021230.721028-3-yuzhao@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Multi-Gen LRU Framework | expand |
On Wed, Mar 9, 2022 at 3:47 PM Yu Zhao <yuzhao@google.com> wrote: > > Some architectures support the accessed bit in non-leaf PMD entries, > e.g., x86 sets the accessed bit in a non-leaf PMD entry when using it > as part of linear address translation [1]. Page table walkers that > clear the accessed bit may use this capability to reduce their search > space. > > Note that: > 1. Although an inline function is preferable, this capability is added > as a configuration option for consistency with the existing macros. > 2. Due to the little interest in other varieties, this capability was > only tested on Intel and AMD CPUs. > > [1]: Intel 64 and IA-32 Architectures Software Developer's Manual > Volume 3 (June 2021), section 4.8 > > Signed-off-by: Yu Zhao <yuzhao@google.com> > Acked-by: Brian Geffon <bgeffon@google.com> > Acked-by: Jan Alexander Steffens (heftig) <heftig@archlinux.org> > Acked-by: Oleksandr Natalenko <oleksandr@natalenko.name> > Acked-by: Steven Barrett <steven@liquorix.net> > Acked-by: Suleiman Souhlal <suleiman@google.com> > Tested-by: Daniel Byrne <djbyrne@mtu.edu> > Tested-by: Donald Carr <d@chaos-reins.com> > Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com> > Tested-by: Konstantin Kharlamov <Hi-Angel@yandex.ru> > Tested-by: Shuang Zhai <szhai2@cs.rochester.edu> > Tested-by: Sofia Trinh <sofia.trinh@edi.works> > Tested-by: Vaibhav Jain <vaibhav@linux.ibm.com> > --- Reviewed-by: Barry Song <baohua@kernel.org> hard to read this patch by itself. but after reading the change in walk_pmd_range(), it seems this patch becomes quite clear: walk_pmd_range() { ... #ifdef CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG if (get_cap(LRU_GEN_NONLEAF_YOUNG)) { if (!pmd_young(val)) continue; walk_pmd_range_locked(pud, addr, vma, walk, &pos); } #endif ... } this gives us the chance to skip the scan of all ptes within the pmd. so i am not quite sure this should necessarily be a separate patch, or should be put together with the change in walk_pmd_range() to make readers understand its purpose. > arch/Kconfig | 9 +++++++++ > arch/x86/Kconfig | 1 + > arch/x86/include/asm/pgtable.h | 3 ++- > arch/x86/mm/pgtable.c | 5 ++++- > include/linux/pgtable.h | 4 ++-- > 5 files changed, 18 insertions(+), 4 deletions(-) > > diff --git a/arch/Kconfig b/arch/Kconfig > index 678a80713b21..f9c59ecadbbb 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -1322,6 +1322,15 @@ config DYNAMIC_SIGFRAME > config HAVE_ARCH_NODE_DEV_GROUP > bool > > +config ARCH_HAS_NONLEAF_PMD_YOUNG > + bool > + depends on PGTABLE_LEVELS > 2 > + help > + Architectures that select this option are capable of setting the > + accessed bit in non-leaf PMD entries when using them as part of linear > + address translations. Page table walkers that clear the accessed bit > + may use this capability to reduce their search space. > + > source "kernel/gcov/Kconfig" > > source "scripts/gcc-plugins/Kconfig" > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 9f5bd41bf660..e787b7fc75be 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -85,6 +85,7 @@ config X86 > select ARCH_HAS_PMEM_API if X86_64 > select ARCH_HAS_PTE_DEVMAP if X86_64 > select ARCH_HAS_PTE_SPECIAL > + select ARCH_HAS_NONLEAF_PMD_YOUNG > select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64 > select ARCH_HAS_COPY_MC if X86_64 > select ARCH_HAS_SET_MEMORY > diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h > index 60b6ce45c2e3..f973788f6b21 100644 > --- a/arch/x86/include/asm/pgtable.h > +++ b/arch/x86/include/asm/pgtable.h > @@ -819,7 +819,8 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd) > > static inline int pmd_bad(pmd_t pmd) > { > - return (pmd_flags(pmd) & ~_PAGE_USER) != _KERNPG_TABLE; > + return (pmd_flags(pmd) & ~(_PAGE_USER | _PAGE_ACCESSED)) != > + (_KERNPG_TABLE & ~_PAGE_ACCESSED); > } > > static inline unsigned long pages_to_mb(unsigned long npg) > diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c > index 3481b35cb4ec..a224193d84bf 100644 > --- a/arch/x86/mm/pgtable.c > +++ b/arch/x86/mm/pgtable.c > @@ -550,7 +550,7 @@ int ptep_test_and_clear_young(struct vm_area_struct *vma, > return ret; > } > > -#ifdef CONFIG_TRANSPARENT_HUGEPAGE > +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) > int pmdp_test_and_clear_young(struct vm_area_struct *vma, > unsigned long addr, pmd_t *pmdp) > { > @@ -562,6 +562,9 @@ int pmdp_test_and_clear_young(struct vm_area_struct *vma, > > return ret; > } > +#endif > + > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > int pudp_test_and_clear_young(struct vm_area_struct *vma, > unsigned long addr, pud_t *pudp) > { > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h > index 79f64dcff07d..743e7fc4afda 100644 > --- a/include/linux/pgtable.h > +++ b/include/linux/pgtable.h > @@ -212,7 +212,7 @@ static inline int ptep_test_and_clear_young(struct vm_area_struct *vma, > #endif > > #ifndef __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG > -#ifdef CONFIG_TRANSPARENT_HUGEPAGE > +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) > static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma, > unsigned long address, > pmd_t *pmdp) > @@ -233,7 +233,7 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma, > BUILD_BUG(); > return 0; > } > -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ > +#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG */ > #endif > > #ifndef __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH > -- > 2.35.1.616.g0bdcbb4464-goog > Thanks Barry
diff --git a/arch/Kconfig b/arch/Kconfig index 678a80713b21..f9c59ecadbbb 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -1322,6 +1322,15 @@ config DYNAMIC_SIGFRAME config HAVE_ARCH_NODE_DEV_GROUP bool +config ARCH_HAS_NONLEAF_PMD_YOUNG + bool + depends on PGTABLE_LEVELS > 2 + help + Architectures that select this option are capable of setting the + accessed bit in non-leaf PMD entries when using them as part of linear + address translations. Page table walkers that clear the accessed bit + may use this capability to reduce their search space. + source "kernel/gcov/Kconfig" source "scripts/gcc-plugins/Kconfig" diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 9f5bd41bf660..e787b7fc75be 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -85,6 +85,7 @@ config X86 select ARCH_HAS_PMEM_API if X86_64 select ARCH_HAS_PTE_DEVMAP if X86_64 select ARCH_HAS_PTE_SPECIAL + select ARCH_HAS_NONLEAF_PMD_YOUNG select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64 select ARCH_HAS_COPY_MC if X86_64 select ARCH_HAS_SET_MEMORY diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 60b6ce45c2e3..f973788f6b21 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -819,7 +819,8 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd) static inline int pmd_bad(pmd_t pmd) { - return (pmd_flags(pmd) & ~_PAGE_USER) != _KERNPG_TABLE; + return (pmd_flags(pmd) & ~(_PAGE_USER | _PAGE_ACCESSED)) != + (_KERNPG_TABLE & ~_PAGE_ACCESSED); } static inline unsigned long pages_to_mb(unsigned long npg) diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c index 3481b35cb4ec..a224193d84bf 100644 --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -550,7 +550,7 @@ int ptep_test_and_clear_young(struct vm_area_struct *vma, return ret; } -#ifdef CONFIG_TRANSPARENT_HUGEPAGE +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) int pmdp_test_and_clear_young(struct vm_area_struct *vma, unsigned long addr, pmd_t *pmdp) { @@ -562,6 +562,9 @@ int pmdp_test_and_clear_young(struct vm_area_struct *vma, return ret; } +#endif + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE int pudp_test_and_clear_young(struct vm_area_struct *vma, unsigned long addr, pud_t *pudp) { diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 79f64dcff07d..743e7fc4afda 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -212,7 +212,7 @@ static inline int ptep_test_and_clear_young(struct vm_area_struct *vma, #endif #ifndef __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG -#ifdef CONFIG_TRANSPARENT_HUGEPAGE +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma, unsigned long address, pmd_t *pmdp) @@ -233,7 +233,7 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma, BUILD_BUG(); return 0; } -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ +#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG */ #endif #ifndef __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH
Some architectures support the accessed bit in non-leaf PMD entries, e.g., x86 sets the accessed bit in a non-leaf PMD entry when using it as part of linear address translation [1]. Page table walkers that clear the accessed bit may use this capability to reduce their search space. Note that: 1. Although an inline function is preferable, this capability is added as a configuration option for consistency with the existing macros. 2. Due to the little interest in other varieties, this capability was only tested on Intel and AMD CPUs. [1]: Intel 64 and IA-32 Architectures Software Developer's Manual Volume 3 (June 2021), section 4.8 Signed-off-by: Yu Zhao <yuzhao@google.com> Acked-by: Brian Geffon <bgeffon@google.com> Acked-by: Jan Alexander Steffens (heftig) <heftig@archlinux.org> Acked-by: Oleksandr Natalenko <oleksandr@natalenko.name> Acked-by: Steven Barrett <steven@liquorix.net> Acked-by: Suleiman Souhlal <suleiman@google.com> Tested-by: Daniel Byrne <djbyrne@mtu.edu> Tested-by: Donald Carr <d@chaos-reins.com> Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com> Tested-by: Konstantin Kharlamov <Hi-Angel@yandex.ru> Tested-by: Shuang Zhai <szhai2@cs.rochester.edu> Tested-by: Sofia Trinh <sofia.trinh@edi.works> Tested-by: Vaibhav Jain <vaibhav@linux.ibm.com> --- arch/Kconfig | 9 +++++++++ arch/x86/Kconfig | 1 + arch/x86/include/asm/pgtable.h | 3 ++- arch/x86/mm/pgtable.c | 5 ++++- include/linux/pgtable.h | 4 ++-- 5 files changed, 18 insertions(+), 4 deletions(-)