From bde6f5f59c2b2b48a7a849c129d5b48838fe77ee Mon Sep 17 00:00:00 2001 From: Venki Pallipadi Date: Wed, 30 Jan 2008 13:32:01 +0100 Subject: x86: voluntary leave_mm before entering ACPI C3 Aviod TLB flush IPIs during C3 states by voluntary leave_mm() before entering C3. The performance impact of TLB flush on C3 should not be significant with respect to C3 wakeup latency. Also, CPUs tend to flush TLB in hardware while in C3 anyways. On a 8 logical CPU system, running make -j2, the number of tlbflush IPIs goes down from 40 per second to ~ 0. Total number of interrupts during the run of this workload was ~1200 per second, which makes it ~3% savings in wakeups. There was no measurable performance or power impact however. [ akpm@linux-foundation.org: symbol export fixes. ] Signed-off-by: Venkatesh Pallipadi Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- drivers/acpi/processor_idle.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers') diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index 2235f4e02d26..0721a8183c89 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -534,6 +534,7 @@ static void acpi_processor_idle(void) break; case ACPI_STATE_C3: + acpi_unlazy_tlb(smp_processor_id()); /* * Must be done before busmaster disable as we might * need to access HPET ! @@ -1423,6 +1424,7 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev, return 0; } + acpi_unlazy_tlb(smp_processor_id()); /* * Must be done before busmaster disable as we might need to * access HPET ! -- cgit v1.2.3