| Message ID | 1403710824-24340-7-git-send-email-steve.capper@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Steve, On Wed, Jun 25, 2014 at 04:40:24PM +0100, Steve Capper wrote: > Activate the RCU fast_gup for ARM64. We also need to force THP splits > to broadcast an IPI s.t. we block in the fast_gup page walker. As THP > splits are comparatively rare, this should not lead to a noticeable > performance degradation. > > Some pre-requisite functions pud_write and pud_page are also added. > > Signed-off-by: Steve Capper <steve.capper@linaro.org> > --- > arch/arm64/Kconfig | 3 +++ > arch/arm64/include/asm/pgtable.h | 11 ++++++++++- > arch/arm64/mm/flush.c | 19 +++++++++++++++++++ > 3 files changed, 32 insertions(+), 1 deletion(-) [...] > diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c > index e4193e3..ddf96c1 100644 > --- a/arch/arm64/mm/flush.c > +++ b/arch/arm64/mm/flush.c > @@ -103,3 +103,22 @@ EXPORT_SYMBOL(flush_dcache_page); > */ > EXPORT_SYMBOL(flush_cache_all); > EXPORT_SYMBOL(flush_icache_range); > + > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > +#ifdef CONFIG_HAVE_RCU_TABLE_FREE > +static void thp_splitting_flush_sync(void *arg) > +{ > +} > + > +void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address, > + pmd_t *pmdp) > +{ > + pmd_t pmd = pmd_mksplitting(*pmdp); > + VM_BUG_ON(address & ~PMD_MASK); > + set_pmd_at(vma->vm_mm, address, pmdp, pmd); > + > + /* dummy IPI to serialise against fast_gup */ > + smp_call_function(thp_splitting_flush_sync, NULL, 1); Is there some reason we can't use kick_all_cpus_sync()? From a glance it seems that powerpc does just that. Mark.
On Wed, Jun 25, 2014 at 05:50:03PM +0100, Mark Rutland wrote: > Hi Steve, > > On Wed, Jun 25, 2014 at 04:40:24PM +0100, Steve Capper wrote: > > Activate the RCU fast_gup for ARM64. We also need to force THP splits > > to broadcast an IPI s.t. we block in the fast_gup page walker. As THP > > splits are comparatively rare, this should not lead to a noticeable > > performance degradation. > > > > Some pre-requisite functions pud_write and pud_page are also added. > > > > Signed-off-by: Steve Capper <steve.capper@linaro.org> > > --- > > arch/arm64/Kconfig | 3 +++ > > arch/arm64/include/asm/pgtable.h | 11 ++++++++++- > > arch/arm64/mm/flush.c | 19 +++++++++++++++++++ > > 3 files changed, 32 insertions(+), 1 deletion(-) > > [...] > > > diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c > > index e4193e3..ddf96c1 100644 > > --- a/arch/arm64/mm/flush.c > > +++ b/arch/arm64/mm/flush.c > > @@ -103,3 +103,22 @@ EXPORT_SYMBOL(flush_dcache_page); > > */ > > EXPORT_SYMBOL(flush_cache_all); > > EXPORT_SYMBOL(flush_icache_range); > > + > > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > > +#ifdef CONFIG_HAVE_RCU_TABLE_FREE > > +static void thp_splitting_flush_sync(void *arg) > > +{ > > +} > > + > > +void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address, > > + pmd_t *pmdp) > > +{ > > + pmd_t pmd = pmd_mksplitting(*pmdp); > > + VM_BUG_ON(address & ~PMD_MASK); > > + set_pmd_at(vma->vm_mm, address, pmdp, pmd); > > + > > + /* dummy IPI to serialise against fast_gup */ > > + smp_call_function(thp_splitting_flush_sync, NULL, 1); > > Is there some reason we can't use kick_all_cpus_sync()? Yes that would be equivalent. But looking at that, I worry about the smp_mb(); archs are supposed to make sure IPIs are serializing.
On Thu, Jun 26, 2014 at 08:56:05AM +0100, Peter Zijlstra wrote: > On Wed, Jun 25, 2014 at 05:50:03PM +0100, Mark Rutland wrote: > > Hi Steve, > > > > On Wed, Jun 25, 2014 at 04:40:24PM +0100, Steve Capper wrote: > > > Activate the RCU fast_gup for ARM64. We also need to force THP splits > > > to broadcast an IPI s.t. we block in the fast_gup page walker. As THP > > > splits are comparatively rare, this should not lead to a noticeable > > > performance degradation. > > > > > > Some pre-requisite functions pud_write and pud_page are also added. > > > > > > Signed-off-by: Steve Capper <steve.capper@linaro.org> > > > --- > > > arch/arm64/Kconfig | 3 +++ > > > arch/arm64/include/asm/pgtable.h | 11 ++++++++++- > > > arch/arm64/mm/flush.c | 19 +++++++++++++++++++ > > > 3 files changed, 32 insertions(+), 1 deletion(-) > > > > [...] > > > > > diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c > > > index e4193e3..ddf96c1 100644 > > > --- a/arch/arm64/mm/flush.c > > > +++ b/arch/arm64/mm/flush.c > > > @@ -103,3 +103,22 @@ EXPORT_SYMBOL(flush_dcache_page); > > > */ > > > EXPORT_SYMBOL(flush_cache_all); > > > EXPORT_SYMBOL(flush_icache_range); > > > + > > > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > > > +#ifdef CONFIG_HAVE_RCU_TABLE_FREE > > > +static void thp_splitting_flush_sync(void *arg) > > > +{ > > > +} > > > + > > > +void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address, > > > + pmd_t *pmdp) > > > +{ > > > + pmd_t pmd = pmd_mksplitting(*pmdp); > > > + VM_BUG_ON(address & ~PMD_MASK); > > > + set_pmd_at(vma->vm_mm, address, pmdp, pmd); > > > + > > > + /* dummy IPI to serialise against fast_gup */ > > > + smp_call_function(thp_splitting_flush_sync, NULL, 1); > > > > Is there some reason we can't use kick_all_cpus_sync()? > > Yes that would be equivalent. But looking at that, I worry about the > smp_mb(); archs are supposed to make sure IPIs are serializing. Agreed; smp_call_function would be hopelessly broken if that wasn't true (at least, everywhere I've used it ;) Will
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index e1d2eef..d6fcb8e 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -102,6 +102,9 @@ config GENERIC_CALIBRATE_DELAY config ZONE_DMA def_bool y +config HAVE_RCU_GUP + def_bool y + config ARCH_DMA_ADDR_T_64BIT def_bool y diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index e0ccceb..62510f7 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -237,7 +237,13 @@ static inline pmd_t pte_pmd(pte_t pte) #ifdef CONFIG_TRANSPARENT_HUGEPAGE #define pmd_trans_huge(pmd) (pmd_val(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT)) #define pmd_trans_splitting(pmd) pte_special(pmd_pte(pmd)) -#endif +#ifdef CONFIG_HAVE_RCU_TABLE_FREE +#define __HAVE_ARCH_PMDP_SPLITTING_FLUSH +struct vm_area_struct; +void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address, + pmd_t *pmdp); +#endif /* CONFIG_HAVE_RCU_TABLE_FREE */ +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #define pmd_young(pmd) pte_young(pmd_pte(pmd)) #define pmd_wrprotect(pmd) pte_pmd(pte_wrprotect(pmd_pte(pmd))) @@ -258,6 +264,7 @@ static inline pmd_t pte_pmd(pte_t pte) #define mk_pmd(page,prot) pfn_pmd(page_to_pfn(page),prot) #define pmd_page(pmd) pfn_to_page(__phys_to_pfn(pmd_val(pmd) & PHYS_MASK)) +#define pud_write(pud) pmd_write(__pmd(pud_val(pud))) #define pud_pfn(pud) (((pud_val(pud) & PUD_MASK) & PHYS_MASK) >> PAGE_SHIFT) #define set_pmd_at(mm, addr, pmdp, pmd) set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd)) @@ -345,6 +352,8 @@ static inline pmd_t *pud_page_vaddr(pud_t pud) return __va(pud_val(pud) & PHYS_MASK & (s32)PAGE_MASK); } +#define pud_page(pud) pmd_page(__pmd(pud_val(pud))) + #endif /* CONFIG_ARM64_64K_PAGES */ /* to find an entry in a page-table-directory */ diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c index e4193e3..ddf96c1 100644 --- a/arch/arm64/mm/flush.c +++ b/arch/arm64/mm/flush.c @@ -103,3 +103,22 @@ EXPORT_SYMBOL(flush_dcache_page); */ EXPORT_SYMBOL(flush_cache_all); EXPORT_SYMBOL(flush_icache_range); + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +#ifdef CONFIG_HAVE_RCU_TABLE_FREE +static void thp_splitting_flush_sync(void *arg) +{ +} + +void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address, + pmd_t *pmdp) +{ + pmd_t pmd = pmd_mksplitting(*pmdp); + VM_BUG_ON(address & ~PMD_MASK); + set_pmd_at(vma->vm_mm, address, pmdp, pmd); + + /* dummy IPI to serialise against fast_gup */ + smp_call_function(thp_splitting_flush_sync, NULL, 1); +} +#endif /* CONFIG_HAVE_RCU_TABLE_FREE */ +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
Activate the RCU fast_gup for ARM64. We also need to force THP splits to broadcast an IPI s.t. we block in the fast_gup page walker. As THP splits are comparatively rare, this should not lead to a noticeable performance degradation. Some pre-requisite functions pud_write and pud_page are also added. Signed-off-by: Steve Capper <steve.capper@linaro.org> --- arch/arm64/Kconfig | 3 +++ arch/arm64/include/asm/pgtable.h | 11 ++++++++++- arch/arm64/mm/flush.c | 19 +++++++++++++++++++ 3 files changed, 32 insertions(+), 1 deletion(-)