From: Nadav Amit <[email protected]> Blindly writing to is_lazy for no reason, when the written value is identical to the old value, makes the cacheline dirty for no reason. Avoid making such writes to prevent cache coherency traffic for no reason.
Cc: Andy Lutomirski <[email protected]> Cc: Peter Zijlstra <[email protected]> Suggested-by: Dave Hansen <[email protected]> Reviewed-by: Dave Hansen <[email protected]> Signed-off-by: Nadav Amit <[email protected]> --- arch/x86/mm/tlb.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index e0271e0f84ea..98d212518f67 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -469,7 +469,8 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, __flush_tlb_all(); } #endif - this_cpu_write(cpu_tlbstate_shared.is_lazy, false); + if (was_lazy) + this_cpu_write(cpu_tlbstate_shared.is_lazy, false); /* * The membarrier system call requires a full memory barrier and -- 2.25.1
