[PATCH 02/19] x86/mm: Only do a local tlb flush in ptep_set_access_flags()
From: Ingo Molnar <mingo@kernel.org>
Date: 2012-11-16 16:30:22
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lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit), x86 mm · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Andy Lutomirski, Peter Zijlstra
From: Rik van Riel <redacted> Because we only ever upgrade a PTE when calling ptep_set_access_flags(), it is safe to skip flushing entries on remote TLBs. The worst that can happen is a spurious page fault on other CPUs, which would flush that TLB entry. Lazily letting another CPU incur a spurious page fault occasionally is (much!) cheaper than aggressively flushing everybody else's TLB. Signed-off-by: Rik van Riel <redacted> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Acked-by: Peter Zijlstra <redacted> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Michel Lespinasse <redacted> Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/mm/pgtable.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 8573b83..be3bb46 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c@@ -301,6 +301,13 @@ void pgd_free(struct mm_struct *mm, pgd_t *pgd) free_page((unsigned long)pgd); } +/* + * Used to set accessed or dirty bits in the page table entries + * on other architectures. On x86, the accessed and dirty bits + * are tracked by hardware. However, do_wp_page calls this function + * to also make the pte writeable at the same time the dirty bit is + * set. In that case we do actually need to write the PTE. + */ int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address, pte_t *ptep, pte_t entry, int dirty)
@@ -310,7 +317,7 @@ int ptep_set_access_flags(struct vm_area_struct *vma, if (changed && dirty) { *ptep = entry; pte_update_defer(vma->vm_mm, address, ptep); - flush_tlb_page(vma, address); + __flush_tlb_one(address); } return changed;
--
1.7.11.7
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