From 3cb1aa7aa39402f4f2cb847b1f16ade3bce43a97 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Thu, 17 Dec 2020 23:47:31 +1000 Subject: [PATCH] powerpc/64s: Implement ptep_clear_flush_young that does not flush TLBs Similarly to the x86 commit b13b1d2d8692 ("x86/mm: In the PTE swapout page reclaim case clear the accessed bit instead of flushing the TLB"), implement ptep_clear_flush_young that does not actually flush the TLB in the case the referenced bit is cleared. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20201217134731.488135-8-npiggin@gmail.com --- arch/powerpc/include/asm/book3s/64/pgtable.h | 23 +++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h index a398866816297..058601efbc8a3 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h @@ -388,11 +388,28 @@ static inline int __ptep_test_and_clear_young(struct mm_struct *mm, #define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG #define ptep_test_and_clear_young(__vma, __addr, __ptep) \ ({ \ - int __r; \ - __r = __ptep_test_and_clear_young((__vma)->vm_mm, __addr, __ptep); \ - __r; \ + __ptep_test_and_clear_young((__vma)->vm_mm, __addr, __ptep); \ }) +/* + * On Book3S CPUs, clearing the accessed bit without a TLB flush + * doesn't cause data corruption. [ It could cause incorrect + * page aging and the (mistaken) reclaim of hot pages, but the + * chance of that should be relatively low. ] + * + * So as a performance optimization don't flush the TLB when + * clearing the accessed bit, it will eventually be flushed by + * a context switch or a VM operation anyway. [ In the rare + * event of it not getting flushed for a long time the delay + * shouldn't really matter because there's no real memory + * pressure for swapout to react to. ] + */ +#define __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH +#define ptep_clear_flush_young ptep_test_and_clear_young + +#define __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH +#define pmdp_clear_flush_young pmdp_test_and_clear_young + static inline int __pte_write(pte_t pte) { return !!(pte_raw(pte) & cpu_to_be64(_PAGE_WRITE)); -- 2.39.5