| Message ID | 20231218105100.172635-17-ryan.roberts@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Transparent Contiguous PTEs for User Mappings | expand |
Ryan Roberts <ryan.roberts@arm.com> writes: > With the core-mm changes in place to batch-clear ptes during > zap_pte_range(), we can take advantage of this in arm64 to greatly > reduce the number of tlbis we have to issue, and recover the lost > performance in exit, munmap and madvise(DONTNEED) incured when adding > support for transparent contiguous ptes. > > If we are clearing a whole contpte range, we can elide first unfolding > that range and save the tlbis. We just clear the whole range. > > The following microbenchmark results demonstate the effect of this > change on madvise(DONTNEED) performance for large pte-mapped folios. > madvise(dontneed) is called for each page of a 1G populated mapping and > the total time is measured. 100 iterations per run, 8 runs performed on > both Apple M2 (VM) and Ampere Altra (bare metal). Tests performed for > case where 1G memory is comprised of pte-mapped order-9 folios. Negative > is faster, positive is slower, compared to baseline upon which the > series is based: > > | dontneed | Apple M2 VM | Ampere Altra | > | order-9 |-------------------|-------------------| > | (pte-map) | mean | stdev | mean | stdev | > |---------------|---------|---------|---------|---------| > | baseline | 0.0% | 7.9% | 0.0% | 0.0% | > | before-change | -1.3% | 7.0% | 13.0% | 0.0% | > | after-change | -9.9% | 0.9% | 14.1% | 0.0% | > > The memory is initially all contpte-mapped and has to be unfolded (which > requires tlbi for the whole block) when the first page is touched (since > the test is madvise-ing 1 page at a time). Ampere Altra has high cost > for tlbi; this is why cost increases there. > > The following microbenchmark results demonstate the recovery (and > overall improvement) of munmap performance for large pte-mapped folios. > munmap is called for a 1G populated mapping and the function runtime is > measured. 100 iterations per run, 8 runs performed on both Apple M2 (VM) > and Ampere Altra (bare metal). Tests performed for case where 1G memory > is comprised of pte-mapped order-9 folios. Negative is faster, positive > is slower, compared to baseline upon which the series is based: > > | munmap | Apple M2 VM | Ampere Altra | > | order-9 |-------------------|-------------------| > | (pte-map) | mean | stdev | mean | stdev | > |---------------|---------|---------|---------|---------| > | baseline | 0.0% | 6.4% | 0.0% | 0.1% | > | before-change | 43.3% | 1.9% | 375.2% | 0.0% | > | after-change | -6.0% | 1.4% | -0.6% | 0.2% | > > Tested-by: John Hubbard <jhubbard@nvidia.com> > Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> > --- > arch/arm64/include/asm/pgtable.h | 42 +++++++++++++++++++++++++++++ > arch/arm64/mm/contpte.c | 45 ++++++++++++++++++++++++++++++++ > 2 files changed, 87 insertions(+) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index d4805f73b9db..f5bf059291c3 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -953,6 +953,29 @@ static inline pte_t __ptep_get_and_clear(struct mm_struct *mm, > return pte; > } > > +static inline pte_t __clear_ptes(struct mm_struct *mm, > + unsigned long address, pte_t *ptep, > + unsigned int nr, int full) Ping on my previous comment - why not just use the generic version defined in patch 3 which is basically identical to this? > +{ > + pte_t orig_pte = __ptep_get_and_clear(mm, address, ptep); > + unsigned int i; > + pte_t pte; > + > + for (i = 1; i < nr; i++) { > + address += PAGE_SIZE; > + ptep++; > + pte = __ptep_get_and_clear(mm, address, ptep); > + > + if (pte_dirty(pte)) > + orig_pte = pte_mkdirty(orig_pte); > + > + if (pte_young(pte)) > + orig_pte = pte_mkyoung(orig_pte); > + } > + > + return orig_pte; > +} > + > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > #define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR > static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm, > @@ -1151,6 +1174,8 @@ extern pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte); > extern pte_t contpte_ptep_get_lockless(pte_t *orig_ptep); > extern void contpte_set_ptes(struct mm_struct *mm, unsigned long addr, > pte_t *ptep, pte_t pte, unsigned int nr); > +extern pte_t contpte_clear_ptes(struct mm_struct *mm, unsigned long addr, > + pte_t *ptep, unsigned int nr, int full); > extern int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, > unsigned long addr, pte_t *ptep); > extern int contpte_ptep_clear_flush_young(struct vm_area_struct *vma, > @@ -1279,6 +1304,22 @@ static inline void pte_clear(struct mm_struct *mm, > __pte_clear(mm, addr, ptep); > } > > +#define clear_ptes clear_ptes > +static inline pte_t clear_ptes(struct mm_struct *mm, > + unsigned long addr, pte_t *ptep, > + unsigned int nr, int full) > +{ > + pte_t pte; > + > + if (nr == 1) { > + contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); > + pte = __ptep_get_and_clear(mm, addr, ptep); > + } else > + pte = contpte_clear_ptes(mm, addr, ptep, nr, full); > + > + return pte; > +} > + > #define __HAVE_ARCH_PTEP_GET_AND_CLEAR > static inline pte_t ptep_get_and_clear(struct mm_struct *mm, > unsigned long addr, pte_t *ptep) > @@ -1366,6 +1407,7 @@ static inline int ptep_set_access_flags(struct vm_area_struct *vma, > #define set_pte __set_pte > #define set_ptes __set_ptes > #define pte_clear __pte_clear > +#define clear_ptes __clear_ptes > #define __HAVE_ARCH_PTEP_GET_AND_CLEAR > #define ptep_get_and_clear __ptep_get_and_clear > #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG > diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c > index 72e672024785..6f2a15ac5163 100644 > --- a/arch/arm64/mm/contpte.c > +++ b/arch/arm64/mm/contpte.c > @@ -293,6 +293,51 @@ void contpte_set_ptes(struct mm_struct *mm, unsigned long addr, > } > EXPORT_SYMBOL(contpte_set_ptes); > > +pte_t contpte_clear_ptes(struct mm_struct *mm, unsigned long addr, pte_t *ptep, > + unsigned int nr, int full) > +{ > + /* > + * If we cover a partial contpte block at the beginning or end of the > + * batch, unfold if currently folded. This makes it safe to clear some > + * of the entries while keeping others. contpte blocks in the middle of > + * the range, which are fully covered don't need to be unfolded because > + * we will clear the full block. > + */ > + > + unsigned int i; > + pte_t pte; > + pte_t tail; > + > + if (!mm_is_user(mm)) > + return __clear_ptes(mm, addr, ptep, nr, full); > + > + if (ptep != contpte_align_down(ptep) || nr < CONT_PTES) > + contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); > + > + if (ptep + nr != contpte_align_down(ptep + nr)) > + contpte_try_unfold(mm, addr + PAGE_SIZE * (nr - 1), > + ptep + nr - 1, > + __ptep_get(ptep + nr - 1)); > + > + pte = __ptep_get_and_clear(mm, addr, ptep); > + > + for (i = 1; i < nr; i++) { > + addr += PAGE_SIZE; > + ptep++; > + > + tail = __ptep_get_and_clear(mm, addr, ptep); > + > + if (pte_dirty(tail)) > + pte = pte_mkdirty(pte); > + > + if (pte_young(tail)) > + pte = pte_mkyoung(pte); > + } > + > + return pte; > +} > +EXPORT_SYMBOL(contpte_clear_ptes); > + > int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, > unsigned long addr, pte_t *ptep) > {
On 20/12/2023 05:28, Alistair Popple wrote: > > Ryan Roberts <ryan.roberts@arm.com> writes: > >> With the core-mm changes in place to batch-clear ptes during >> zap_pte_range(), we can take advantage of this in arm64 to greatly >> reduce the number of tlbis we have to issue, and recover the lost >> performance in exit, munmap and madvise(DONTNEED) incured when adding >> support for transparent contiguous ptes. >> >> If we are clearing a whole contpte range, we can elide first unfolding >> that range and save the tlbis. We just clear the whole range. >> >> The following microbenchmark results demonstate the effect of this >> change on madvise(DONTNEED) performance for large pte-mapped folios. >> madvise(dontneed) is called for each page of a 1G populated mapping and >> the total time is measured. 100 iterations per run, 8 runs performed on >> both Apple M2 (VM) and Ampere Altra (bare metal). Tests performed for >> case where 1G memory is comprised of pte-mapped order-9 folios. Negative >> is faster, positive is slower, compared to baseline upon which the >> series is based: >> >> | dontneed | Apple M2 VM | Ampere Altra | >> | order-9 |-------------------|-------------------| >> | (pte-map) | mean | stdev | mean | stdev | >> |---------------|---------|---------|---------|---------| >> | baseline | 0.0% | 7.9% | 0.0% | 0.0% | >> | before-change | -1.3% | 7.0% | 13.0% | 0.0% | >> | after-change | -9.9% | 0.9% | 14.1% | 0.0% | >> >> The memory is initially all contpte-mapped and has to be unfolded (which >> requires tlbi for the whole block) when the first page is touched (since >> the test is madvise-ing 1 page at a time). Ampere Altra has high cost >> for tlbi; this is why cost increases there. >> >> The following microbenchmark results demonstate the recovery (and >> overall improvement) of munmap performance for large pte-mapped folios. >> munmap is called for a 1G populated mapping and the function runtime is >> measured. 100 iterations per run, 8 runs performed on both Apple M2 (VM) >> and Ampere Altra (bare metal). Tests performed for case where 1G memory >> is comprised of pte-mapped order-9 folios. Negative is faster, positive >> is slower, compared to baseline upon which the series is based: >> >> | munmap | Apple M2 VM | Ampere Altra | >> | order-9 |-------------------|-------------------| >> | (pte-map) | mean | stdev | mean | stdev | >> |---------------|---------|---------|---------|---------| >> | baseline | 0.0% | 6.4% | 0.0% | 0.1% | >> | before-change | 43.3% | 1.9% | 375.2% | 0.0% | >> | after-change | -6.0% | 1.4% | -0.6% | 0.2% | >> >> Tested-by: John Hubbard <jhubbard@nvidia.com> >> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> >> --- >> arch/arm64/include/asm/pgtable.h | 42 +++++++++++++++++++++++++++++ >> arch/arm64/mm/contpte.c | 45 ++++++++++++++++++++++++++++++++ >> 2 files changed, 87 insertions(+) >> >> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h >> index d4805f73b9db..f5bf059291c3 100644 >> --- a/arch/arm64/include/asm/pgtable.h >> +++ b/arch/arm64/include/asm/pgtable.h >> @@ -953,6 +953,29 @@ static inline pte_t __ptep_get_and_clear(struct mm_struct *mm, >> return pte; >> } >> >> +static inline pte_t __clear_ptes(struct mm_struct *mm, >> + unsigned long address, pte_t *ptep, >> + unsigned int nr, int full) > > Ping on my previous comment - why not just use the generic version > defined in patch 3 which is basically identical to this? Perhaps I misunderstood your original comment - I thought this was what you were suggesting - i.e. move this code out of the arm64 clear_ptes() impl into its own __clear_ptes() helper, and always define an arm64 clear_ptes(), even when ARM64_CONTPTE is not enabled. I can use (and was in v3) the generic version when ARM64_CONTPTE is disabled. But I can't use it when its enabled, because then arm64 needs its own implementation to manage the contpte bit. And once it defines it's own version, by defining the macro clear_ptes(), then the generic version is no longer defined so I can't call it as part of this implementation. Even if I could, that would be recursive. Or perhaps I'm still not understanding your suggestion? > >> +{ >> + pte_t orig_pte = __ptep_get_and_clear(mm, address, ptep); >> + unsigned int i; >> + pte_t pte; >> + >> + for (i = 1; i < nr; i++) { >> + address += PAGE_SIZE; >> + ptep++; >> + pte = __ptep_get_and_clear(mm, address, ptep); >> + >> + if (pte_dirty(pte)) >> + orig_pte = pte_mkdirty(orig_pte); >> + >> + if (pte_young(pte)) >> + orig_pte = pte_mkyoung(orig_pte); >> + } >> + >> + return orig_pte; >> +} >> + >> #ifdef CONFIG_TRANSPARENT_HUGEPAGE >> #define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR >> static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm, >> @@ -1151,6 +1174,8 @@ extern pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte); >> extern pte_t contpte_ptep_get_lockless(pte_t *orig_ptep); >> extern void contpte_set_ptes(struct mm_struct *mm, unsigned long addr, >> pte_t *ptep, pte_t pte, unsigned int nr); >> +extern pte_t contpte_clear_ptes(struct mm_struct *mm, unsigned long addr, >> + pte_t *ptep, unsigned int nr, int full); >> extern int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, >> unsigned long addr, pte_t *ptep); >> extern int contpte_ptep_clear_flush_young(struct vm_area_struct *vma, >> @@ -1279,6 +1304,22 @@ static inline void pte_clear(struct mm_struct *mm, >> __pte_clear(mm, addr, ptep); >> } >> >> +#define clear_ptes clear_ptes >> +static inline pte_t clear_ptes(struct mm_struct *mm, >> + unsigned long addr, pte_t *ptep, >> + unsigned int nr, int full) >> +{ >> + pte_t pte; >> + >> + if (nr == 1) { >> + contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); >> + pte = __ptep_get_and_clear(mm, addr, ptep); >> + } else >> + pte = contpte_clear_ptes(mm, addr, ptep, nr, full); >> + >> + return pte; >> +} >> + >> #define __HAVE_ARCH_PTEP_GET_AND_CLEAR >> static inline pte_t ptep_get_and_clear(struct mm_struct *mm, >> unsigned long addr, pte_t *ptep) >> @@ -1366,6 +1407,7 @@ static inline int ptep_set_access_flags(struct vm_area_struct *vma, >> #define set_pte __set_pte >> #define set_ptes __set_ptes >> #define pte_clear __pte_clear >> +#define clear_ptes __clear_ptes >> #define __HAVE_ARCH_PTEP_GET_AND_CLEAR >> #define ptep_get_and_clear __ptep_get_and_clear >> #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG >> diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c >> index 72e672024785..6f2a15ac5163 100644 >> --- a/arch/arm64/mm/contpte.c >> +++ b/arch/arm64/mm/contpte.c >> @@ -293,6 +293,51 @@ void contpte_set_ptes(struct mm_struct *mm, unsigned long addr, >> } >> EXPORT_SYMBOL(contpte_set_ptes); >> >> +pte_t contpte_clear_ptes(struct mm_struct *mm, unsigned long addr, pte_t *ptep, >> + unsigned int nr, int full) >> +{ >> + /* >> + * If we cover a partial contpte block at the beginning or end of the >> + * batch, unfold if currently folded. This makes it safe to clear some >> + * of the entries while keeping others. contpte blocks in the middle of >> + * the range, which are fully covered don't need to be unfolded because >> + * we will clear the full block. >> + */ >> + >> + unsigned int i; >> + pte_t pte; >> + pte_t tail; >> + >> + if (!mm_is_user(mm)) >> + return __clear_ptes(mm, addr, ptep, nr, full); >> + >> + if (ptep != contpte_align_down(ptep) || nr < CONT_PTES) >> + contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); >> + >> + if (ptep + nr != contpte_align_down(ptep + nr)) >> + contpte_try_unfold(mm, addr + PAGE_SIZE * (nr - 1), >> + ptep + nr - 1, >> + __ptep_get(ptep + nr - 1)); >> + >> + pte = __ptep_get_and_clear(mm, addr, ptep); >> + >> + for (i = 1; i < nr; i++) { >> + addr += PAGE_SIZE; >> + ptep++; >> + >> + tail = __ptep_get_and_clear(mm, addr, ptep); >> + >> + if (pte_dirty(tail)) >> + pte = pte_mkdirty(pte); >> + >> + if (pte_young(tail)) >> + pte = pte_mkyoung(pte); >> + } >> + >> + return pte; >> +} >> +EXPORT_SYMBOL(contpte_clear_ptes); >> + >> int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, >> unsigned long addr, pte_t *ptep) >> { >
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index d4805f73b9db..f5bf059291c3 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -953,6 +953,29 @@ static inline pte_t __ptep_get_and_clear(struct mm_struct *mm, return pte; } +static inline pte_t __clear_ptes(struct mm_struct *mm, + unsigned long address, pte_t *ptep, + unsigned int nr, int full) +{ + pte_t orig_pte = __ptep_get_and_clear(mm, address, ptep); + unsigned int i; + pte_t pte; + + for (i = 1; i < nr; i++) { + address += PAGE_SIZE; + ptep++; + pte = __ptep_get_and_clear(mm, address, ptep); + + if (pte_dirty(pte)) + orig_pte = pte_mkdirty(orig_pte); + + if (pte_young(pte)) + orig_pte = pte_mkyoung(orig_pte); + } + + return orig_pte; +} + #ifdef CONFIG_TRANSPARENT_HUGEPAGE #define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm, @@ -1151,6 +1174,8 @@ extern pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte); extern pte_t contpte_ptep_get_lockless(pte_t *orig_ptep); extern void contpte_set_ptes(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte, unsigned int nr); +extern pte_t contpte_clear_ptes(struct mm_struct *mm, unsigned long addr, + pte_t *ptep, unsigned int nr, int full); extern int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep); extern int contpte_ptep_clear_flush_young(struct vm_area_struct *vma, @@ -1279,6 +1304,22 @@ static inline void pte_clear(struct mm_struct *mm, __pte_clear(mm, addr, ptep); } +#define clear_ptes clear_ptes +static inline pte_t clear_ptes(struct mm_struct *mm, + unsigned long addr, pte_t *ptep, + unsigned int nr, int full) +{ + pte_t pte; + + if (nr == 1) { + contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); + pte = __ptep_get_and_clear(mm, addr, ptep); + } else + pte = contpte_clear_ptes(mm, addr, ptep, nr, full); + + return pte; +} + #define __HAVE_ARCH_PTEP_GET_AND_CLEAR static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep) @@ -1366,6 +1407,7 @@ static inline int ptep_set_access_flags(struct vm_area_struct *vma, #define set_pte __set_pte #define set_ptes __set_ptes #define pte_clear __pte_clear +#define clear_ptes __clear_ptes #define __HAVE_ARCH_PTEP_GET_AND_CLEAR #define ptep_get_and_clear __ptep_get_and_clear #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c index 72e672024785..6f2a15ac5163 100644 --- a/arch/arm64/mm/contpte.c +++ b/arch/arm64/mm/contpte.c @@ -293,6 +293,51 @@ void contpte_set_ptes(struct mm_struct *mm, unsigned long addr, } EXPORT_SYMBOL(contpte_set_ptes); +pte_t contpte_clear_ptes(struct mm_struct *mm, unsigned long addr, pte_t *ptep, + unsigned int nr, int full) +{ + /* + * If we cover a partial contpte block at the beginning or end of the + * batch, unfold if currently folded. This makes it safe to clear some + * of the entries while keeping others. contpte blocks in the middle of + * the range, which are fully covered don't need to be unfolded because + * we will clear the full block. + */ + + unsigned int i; + pte_t pte; + pte_t tail; + + if (!mm_is_user(mm)) + return __clear_ptes(mm, addr, ptep, nr, full); + + if (ptep != contpte_align_down(ptep) || nr < CONT_PTES) + contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); + + if (ptep + nr != contpte_align_down(ptep + nr)) + contpte_try_unfold(mm, addr + PAGE_SIZE * (nr - 1), + ptep + nr - 1, + __ptep_get(ptep + nr - 1)); + + pte = __ptep_get_and_clear(mm, addr, ptep); + + for (i = 1; i < nr; i++) { + addr += PAGE_SIZE; + ptep++; + + tail = __ptep_get_and_clear(mm, addr, ptep); + + if (pte_dirty(tail)) + pte = pte_mkdirty(pte); + + if (pte_young(tail)) + pte = pte_mkyoung(pte); + } + + return pte; +} +EXPORT_SYMBOL(contpte_clear_ptes); + int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep) {