Subject: x86: idle wakeup event in the HLT loop From: Ingo Molnar do a proper idle-wakeup event on HLT as well - some CPUs stop the TSC in HLT too, not just when going through the ACPI methods. (the ACPI idle code already does this.) [ update the 64-bit side too, as noticed by Jiri Slaby. ] Signed-off-by: Ingo Molnar --- arch/x86/kernel/process_32.c | 15 ++++++++++++--- arch/x86/kernel/process_64.c | 13 ++++++++++--- 2 files changed, 22 insertions(+), 6 deletions(-) Index: linux-x86.q/arch/x86/kernel/process_32.c =================================================================== --- linux-x86.q.orig/arch/x86/kernel/process_32.c +++ linux-x86.q/arch/x86/kernel/process_32.c @@ -113,10 +113,19 @@ void default_idle(void) smp_mb(); local_irq_disable(); - if (!need_resched()) + if (!need_resched()) { + ktime_t t0, t1; + u64 t0n, t1n; + + t0 = ktime_get(); + t0n = ktime_to_ns(t0); safe_halt(); /* enables interrupts racelessly */ - else - local_irq_enable(); + local_irq_disable(); + t1 = ktime_get(); + t1n = ktime_to_ns(t1); + sched_clock_idle_wakeup_event(t1n - t0n); + } + local_irq_enable(); current_thread_info()->status |= TS_POLLING; } else { /* loop is done by the caller */ Index: linux-x86.q/arch/x86/kernel/process_64.c =================================================================== --- linux-x86.q.orig/arch/x86/kernel/process_64.c +++ linux-x86.q/arch/x86/kernel/process_64.c @@ -116,9 +116,16 @@ static void default_idle(void) smp_mb(); local_irq_disable(); if (!need_resched()) { - /* Enables interrupts one instruction before HLT. - x86 special cases this so there is no race. */ - safe_halt(); + ktime_t t0, t1; + u64 t0n, t1n; + + t0 = ktime_get(); + t0n = ktime_to_ns(t0); + safe_halt(); /* enables interrupts racelessly */ + local_irq_disable(); + t1 = ktime_get(); + t1n = ktime_to_ns(t1); + sched_clock_idle_wakeup_event(t1n - t0n); } else local_irq_enable(); current_thread_info()->status |= TS_POLLING;