[RFC PATCH V4 4/7] arm: mm: Enable RCU fast_gup
From: Steve Capper <hidden>
Date: 2014-03-28 15:01:48
Also in:
linux-arch, linux-mm
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
Activate the RCU fast_gup for ARM. 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. Signed-off-by: Steve Capper <redacted> --- arch/arm/Kconfig | 3 +++ arch/arm/include/asm/pgtable-3level.h | 6 ++++++ arch/arm/mm/flush.c | 19 +++++++++++++++++++ 3 files changed, 28 insertions(+)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 7d5340d..3cf589e 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig@@ -1788,6 +1788,9 @@ config ARCH_SELECT_MEMORY_MODEL config HAVE_ARCH_PFN_VALID def_bool ARCH_HAS_HOLES_MEMORYMODEL || !SPARSEMEM +config HAVE_RCU_GUP + def_bool y + config HIGHMEM bool "High Memory Support" depends on MMU
diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h
index b286ba9..fdc4a4f 100644
--- a/arch/arm/include/asm/pgtable-3level.h
+++ b/arch/arm/include/asm/pgtable-3level.h@@ -226,6 +226,12 @@ static inline pte_t pte_mkspecial(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) (pmd_val(pmd) & PMD_SECT_SPLITTING) + +#ifdef CONFIG_HAVE_RCU_TABLE_FREE +#define __HAVE_ARCH_PMDP_SPLITTING_FLUSH +void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address, + pmd_t *pmdp); +#endif #endif #define PMD_BIT_FUNC(fn,op) \
diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index 3387e60..91a2b59 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c@@ -377,3 +377,22 @@ void __flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned l */ __cpuc_flush_dcache_area(page_address(page), PAGE_SIZE); } + +#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 */
--
1.8.1.4