| Message ID | 20240413002219.71246-3-ioworker0@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/madvise: enhance lazyfreeing with mTHP in madvise_free | expand |
On 13/04/2024 01:22, Lance Yang wrote: > The per-pte get_and_clear/modify/set approach would result in > unfolding/refolding for contpte mappings on arm64. So we need > to override clear_young_dirty_ptes() for arm64 to avoid it. > > Suggested-by: David Hildenbrand <david@redhat.com> > Suggested-by: Barry Song <21cnbao@gmail.com> > Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> No, afraid I haven't signed off yet! > Signed-off-by: Lance Yang <ioworker0@gmail.com> > --- > arch/arm64/include/asm/pgtable.h | 37 ++++++++++++++++++++++++++++++++ > arch/arm64/mm/contpte.c | 28 ++++++++++++++++++++++++ > 2 files changed, 65 insertions(+) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 9fd8613b2db2..f951774dd2d6 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -1223,6 +1223,28 @@ static inline void __wrprotect_ptes(struct mm_struct *mm, unsigned long address, > __ptep_set_wrprotect(mm, address, ptep); > } > > +static inline void __clear_young_dirty_ptes(struct mm_struct *mm, > + unsigned long addr, pte_t *ptep, > + unsigned int nr, cydp_t flags) > +{ > + pte_t pte; > + > + for (;;) { > + pte = __ptep_get(ptep); > + > + if (flags | CYDP_CLEAR_YOUNG) bug: should be bitwise AND (&). > + pte = pte_mkold(pte); > + if (flags | CYDP_CLEAR_DIRTY) > + pte = pte_mkclean(pte); > + > + __set_pte(ptep, pte); The __ptep_get() and __set_pte() are not atomic. This is only safe when you are clearing BOTH access and dirty (as I explained in the previous version). If you are only clearing one of the flags, you will need a similar cmpxchg loop as for __ptep_test_and_clear_young(). Otherwise you can race with the HW and lose information. > + if (--nr == 0) > + break; > + ptep++; > + addr += PAGE_SIZE; > + } > +} > + > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > #define __HAVE_ARCH_PMDP_SET_WRPROTECT > static inline void pmdp_set_wrprotect(struct mm_struct *mm, > @@ -1379,6 +1401,9 @@ extern void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr, > extern int contpte_ptep_set_access_flags(struct vm_area_struct *vma, > unsigned long addr, pte_t *ptep, > pte_t entry, int dirty); > +extern void contpte_clear_young_dirty_ptes(struct mm_struct *mm, > + unsigned long addr, pte_t *ptep, > + unsigned int nr, cydp_t flags); > > static __always_inline void contpte_try_fold(struct mm_struct *mm, > unsigned long addr, pte_t *ptep, pte_t pte) > @@ -1603,6 +1628,17 @@ static inline int ptep_set_access_flags(struct vm_area_struct *vma, > return contpte_ptep_set_access_flags(vma, addr, ptep, entry, dirty); > } > > +#define clear_young_dirty_ptes clear_young_dirty_ptes > +static inline void clear_young_dirty_ptes(struct mm_struct *mm, > + unsigned long addr, pte_t *ptep, > + unsigned int nr, cydp_t flags) > +{ > + if (likely(nr == 1 && !pte_cont(__ptep_get(ptep)))) > + __clear_young_dirty_ptes(mm, addr, ptep, nr, flags); > + else > + contpte_clear_young_dirty_ptes(mm, addr, ptep, nr, flags); > +} > + > #else /* CONFIG_ARM64_CONTPTE */ > > #define ptep_get __ptep_get > @@ -1622,6 +1658,7 @@ static inline int ptep_set_access_flags(struct vm_area_struct *vma, > #define wrprotect_ptes __wrprotect_ptes > #define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS > #define ptep_set_access_flags __ptep_set_access_flags > +#define clear_young_dirty_ptes __clear_young_dirty_ptes > > #endif /* CONFIG_ARM64_CONTPTE */ > > diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c > index 1b64b4c3f8bf..bf3b089d9641 100644 > --- a/arch/arm64/mm/contpte.c > +++ b/arch/arm64/mm/contpte.c > @@ -361,6 +361,34 @@ void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr, > } > EXPORT_SYMBOL_GPL(contpte_wrprotect_ptes); > > +void contpte_clear_young_dirty_ptes(struct mm_struct *mm, unsigned long addr, > + pte_t *ptep, unsigned int nr, cydp_t flags) > +{ > + /* > + * We can safely clear access/dirty without needing to unfold from > + * the architectures perspective, even when contpte is set. If the > + * range starts or ends midway through a contpte block, we can just > + * expand to include the full contpte block. While this is not > + * exactly what the core-mm asked for, it tracks access/dirty per > + * folio, not per page. And since we only create a contpte block > + * when it is covered by a single folio, we can get away with > + * clearing access/dirty for the whole block. > + */ > + unsigned int start = addr; > + unsigned int end = start + nr; There are addresses; they should be unsigned long. May have been my error originally when I sent you the example snippet. Thanks, Ryan > + > + if (pte_cont(__ptep_get(ptep + nr - 1))) > + end = ALIGN(end, CONT_PTE_SIZE); > + > + if (pte_cont(__ptep_get(ptep))) { > + start = ALIGN_DOWN(start, CONT_PTE_SIZE); > + ptep = contpte_align_down(ptep); > + } > + > + __clear_young_dirty_ptes(mm, start, ptep, end - start, flags); > +} > +EXPORT_SYMBOL_GPL(contpte_clear_young_dirty_ptes); > + > int contpte_ptep_set_access_flags(struct vm_area_struct *vma, > unsigned long addr, pte_t *ptep, > pte_t entry, int dirty)
On Mon, Apr 15, 2024 at 4:59 PM Ryan Roberts <ryan.roberts@arm.com> wrote: > > On 13/04/2024 01:22, Lance Yang wrote: > > The per-pte get_and_clear/modify/set approach would result in > > unfolding/refolding for contpte mappings on arm64. So we need > > to override clear_young_dirty_ptes() for arm64 to avoid it. > > > > Suggested-by: David Hildenbrand <david@redhat.com> > > Suggested-by: Barry Song <21cnbao@gmail.com> > > Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> > > No, afraid I haven't signed off yet! Actually, you've done most of this change, and I just do the legwork :) But I'll remove this s-o-b. > > > Signed-off-by: Lance Yang <ioworker0@gmail.com> > > --- > > arch/arm64/include/asm/pgtable.h | 37 ++++++++++++++++++++++++++++++++ > > arch/arm64/mm/contpte.c | 28 ++++++++++++++++++++++++ > > 2 files changed, 65 insertions(+) > > > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > > index 9fd8613b2db2..f951774dd2d6 100644 > > --- a/arch/arm64/include/asm/pgtable.h > > +++ b/arch/arm64/include/asm/pgtable.h > > @@ -1223,6 +1223,28 @@ static inline void __wrprotect_ptes(struct mm_struct *mm, unsigned long address, > > __ptep_set_wrprotect(mm, address, ptep); > > } > > > > +static inline void __clear_young_dirty_ptes(struct mm_struct *mm, > > + unsigned long addr, pte_t *ptep, > > + unsigned int nr, cydp_t flags) > > +{ > > + pte_t pte; > > + > > + for (;;) { > > + pte = __ptep_get(ptep); > > + > > + if (flags | CYDP_CLEAR_YOUNG) > > bug: should be bitwise AND (&). Good spot! Thanks! > > > + pte = pte_mkold(pte); > > + if (flags | CYDP_CLEAR_DIRTY) > > + pte = pte_mkclean(pte); > > + > > + __set_pte(ptep, pte); > > The __ptep_get() and __set_pte() are not atomic. This is only safe when you are > clearing BOTH access and dirty (as I explained in the previous version). If you > are only clearing one of the flags, you will need a similar cmpxchg loop as for > __ptep_test_and_clear_young(). Otherwise you can race with the HW and lose > information. Thanks again for your patience and explanation! I still got it wrong :( > > > + if (--nr == 0) > > + break; > > + ptep++; > > + addr += PAGE_SIZE; > > + } > > +} > > + > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > > #define __HAVE_ARCH_PMDP_SET_WRPROTECT > > static inline void pmdp_set_wrprotect(struct mm_struct *mm, > > @@ -1379,6 +1401,9 @@ extern void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr, > > extern int contpte_ptep_set_access_flags(struct vm_area_struct *vma, > > unsigned long addr, pte_t *ptep, > > pte_t entry, int dirty); > > +extern void contpte_clear_young_dirty_ptes(struct mm_struct *mm, > > + unsigned long addr, pte_t *ptep, > > + unsigned int nr, cydp_t flags); > > > > static __always_inline void contpte_try_fold(struct mm_struct *mm, > > unsigned long addr, pte_t *ptep, pte_t pte) > > @@ -1603,6 +1628,17 @@ static inline int ptep_set_access_flags(struct vm_area_struct *vma, > > return contpte_ptep_set_access_flags(vma, addr, ptep, entry, dirty); > > } > > > > +#define clear_young_dirty_ptes clear_young_dirty_ptes > > +static inline void clear_young_dirty_ptes(struct mm_struct *mm, > > + unsigned long addr, pte_t *ptep, > > + unsigned int nr, cydp_t flags) > > +{ > > + if (likely(nr == 1 && !pte_cont(__ptep_get(ptep)))) > > + __clear_young_dirty_ptes(mm, addr, ptep, nr, flags); > > + else > > + contpte_clear_young_dirty_ptes(mm, addr, ptep, nr, flags); > > +} > > + > > #else /* CONFIG_ARM64_CONTPTE */ > > > > #define ptep_get __ptep_get > > @@ -1622,6 +1658,7 @@ static inline int ptep_set_access_flags(struct vm_area_struct *vma, > > #define wrprotect_ptes __wrprotect_ptes > > #define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS > > #define ptep_set_access_flags __ptep_set_access_flags > > +#define clear_young_dirty_ptes __clear_young_dirty_ptes > > > > #endif /* CONFIG_ARM64_CONTPTE */ > > > > diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c > > index 1b64b4c3f8bf..bf3b089d9641 100644 > > --- a/arch/arm64/mm/contpte.c > > +++ b/arch/arm64/mm/contpte.c > > @@ -361,6 +361,34 @@ void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr, > > } > > EXPORT_SYMBOL_GPL(contpte_wrprotect_ptes); > > > > +void contpte_clear_young_dirty_ptes(struct mm_struct *mm, unsigned long addr, > > + pte_t *ptep, unsigned int nr, cydp_t flags) > > +{ > > + /* > > + * We can safely clear access/dirty without needing to unfold from > > + * the architectures perspective, even when contpte is set. If the > > + * range starts or ends midway through a contpte block, we can just > > + * expand to include the full contpte block. While this is not > > + * exactly what the core-mm asked for, it tracks access/dirty per > > + * folio, not per page. And since we only create a contpte block > > + * when it is covered by a single folio, we can get away with > > + * clearing access/dirty for the whole block. > > + */ > > + unsigned int start = addr; > > + unsigned int end = start + nr; > > There are addresses; they should be unsigned long. May have been my error > originally when I sent you the example snippet. Got it. I'll sort it. Thanks again for your time! Thanks, Lance > > Thanks, > Ryan > > > + > > + if (pte_cont(__ptep_get(ptep + nr - 1))) > > + end = ALIGN(end, CONT_PTE_SIZE); > > + > > + if (pte_cont(__ptep_get(ptep))) { > > + start = ALIGN_DOWN(start, CONT_PTE_SIZE); > > + ptep = contpte_align_down(ptep); > > + } > > + > > + __clear_young_dirty_ptes(mm, start, ptep, end - start, flags); > > +} > > +EXPORT_SYMBOL_GPL(contpte_clear_young_dirty_ptes); > > + > > int contpte_ptep_set_access_flags(struct vm_area_struct *vma, > > unsigned long addr, pte_t *ptep, > > pte_t entry, int dirty) >
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 9fd8613b2db2..f951774dd2d6 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1223,6 +1223,28 @@ static inline void __wrprotect_ptes(struct mm_struct *mm, unsigned long address, __ptep_set_wrprotect(mm, address, ptep); } +static inline void __clear_young_dirty_ptes(struct mm_struct *mm, + unsigned long addr, pte_t *ptep, + unsigned int nr, cydp_t flags) +{ + pte_t pte; + + for (;;) { + pte = __ptep_get(ptep); + + if (flags | CYDP_CLEAR_YOUNG) + pte = pte_mkold(pte); + if (flags | CYDP_CLEAR_DIRTY) + pte = pte_mkclean(pte); + + __set_pte(ptep, pte); + if (--nr == 0) + break; + ptep++; + addr += PAGE_SIZE; + } +} + #ifdef CONFIG_TRANSPARENT_HUGEPAGE #define __HAVE_ARCH_PMDP_SET_WRPROTECT static inline void pmdp_set_wrprotect(struct mm_struct *mm, @@ -1379,6 +1401,9 @@ extern void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr, extern int contpte_ptep_set_access_flags(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep, pte_t entry, int dirty); +extern void contpte_clear_young_dirty_ptes(struct mm_struct *mm, + unsigned long addr, pte_t *ptep, + unsigned int nr, cydp_t flags); static __always_inline void contpte_try_fold(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte) @@ -1603,6 +1628,17 @@ static inline int ptep_set_access_flags(struct vm_area_struct *vma, return contpte_ptep_set_access_flags(vma, addr, ptep, entry, dirty); } +#define clear_young_dirty_ptes clear_young_dirty_ptes +static inline void clear_young_dirty_ptes(struct mm_struct *mm, + unsigned long addr, pte_t *ptep, + unsigned int nr, cydp_t flags) +{ + if (likely(nr == 1 && !pte_cont(__ptep_get(ptep)))) + __clear_young_dirty_ptes(mm, addr, ptep, nr, flags); + else + contpte_clear_young_dirty_ptes(mm, addr, ptep, nr, flags); +} + #else /* CONFIG_ARM64_CONTPTE */ #define ptep_get __ptep_get @@ -1622,6 +1658,7 @@ static inline int ptep_set_access_flags(struct vm_area_struct *vma, #define wrprotect_ptes __wrprotect_ptes #define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS #define ptep_set_access_flags __ptep_set_access_flags +#define clear_young_dirty_ptes __clear_young_dirty_ptes #endif /* CONFIG_ARM64_CONTPTE */ diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c index 1b64b4c3f8bf..bf3b089d9641 100644 --- a/arch/arm64/mm/contpte.c +++ b/arch/arm64/mm/contpte.c @@ -361,6 +361,34 @@ void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr, } EXPORT_SYMBOL_GPL(contpte_wrprotect_ptes); +void contpte_clear_young_dirty_ptes(struct mm_struct *mm, unsigned long addr, + pte_t *ptep, unsigned int nr, cydp_t flags) +{ + /* + * We can safely clear access/dirty without needing to unfold from + * the architectures perspective, even when contpte is set. If the + * range starts or ends midway through a contpte block, we can just + * expand to include the full contpte block. While this is not + * exactly what the core-mm asked for, it tracks access/dirty per + * folio, not per page. And since we only create a contpte block + * when it is covered by a single folio, we can get away with + * clearing access/dirty for the whole block. + */ + unsigned int start = addr; + unsigned int end = start + nr; + + if (pte_cont(__ptep_get(ptep + nr - 1))) + end = ALIGN(end, CONT_PTE_SIZE); + + if (pte_cont(__ptep_get(ptep))) { + start = ALIGN_DOWN(start, CONT_PTE_SIZE); + ptep = contpte_align_down(ptep); + } + + __clear_young_dirty_ptes(mm, start, ptep, end - start, flags); +} +EXPORT_SYMBOL_GPL(contpte_clear_young_dirty_ptes); + int contpte_ptep_set_access_flags(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep, pte_t entry, int dirty)