On Saturday 28 March 2009 05:30:41 Len Brown wrote:
> From: alex.shi <alex.shi@xxxxxxxxx>
>
> We found Cx states time abnormal in our some of machines which have 16
> LCPUs, the C0 take too many time while system is really idle when kernel
> enabled tickless and highres. powertop output is below:
>
> PowerTOP version 1.9 (C) 2007 Intel Corporation
>
> Cn Avg residency P-states (frequencies)
> C0 (cpu running) (40.5%) 2.53 Ghz 0.0%
> C1 0.0ms ( 0.0%) 2.53 Ghz 0.0%
> C2 128.8ms (59.5%) 2.40 Ghz 0.0%
> 1.60 Ghz 100.0%
>
> Wakeups-from-idle per second : 4.7 interval: 20.0s
> no ACPI power usage estimate available
>
> Top causes for wakeups:
> 41.4% ( 24.9) <interrupt> : extra timer interrupt
> 20.2% ( 12.2) <kernel core> : usb_hcd_poll_rh_status
> (rh_timer_func)
>
> After tacking detailed for this issue, Yakui and I find it is due to 24
> bit PM timer overflows when some of cpu sleep more than 4 seconds. With
> tickless kernel, the CPU want to sleep as much as possible when system
> idle. But the Cx sleep time are recorded by pmtimer which length is
> determined by BIOS. The current Cx time was gotten in the following
> function from driver/acpi/processor_idle.c:
>
> static inline u32 ticks_elapsed(u32 t1, u32 t2)
> {
> if (t2 >= t1)
> return (t2 - t1);
> else if (!(acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER))
> return (((0x00FFFFFF - t1) + t2) & 0x00FFFFFF);
> else
> return ((0xFFFFFFFF - t1) + t2);
> }
>
> If pmtimer is 24 bits and it take 5 seconds from t1 to t2, in above
> function, just about 1 seconds ticks was recorded. So the Cx time will be
> reduced about 4 seconds. and this is why we see above powertop output.
>
> To resolve this problem, Yakui and I use ktime_get() to record the Cx
> states time instead of PM timer as the following patch. the patch was
> tested with i386/x86_64 modes on several platforms.
Is this worth adding:
CC: stable@xxxxxxxxxx
but wait until 2.6.30 is finished and no regressions have been reported?
Then backport things to .29/.28 and eventually others?
Thomas
> Acked-by: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
> Tested-by: Alex Shi <alex.shi@xxxxxxxxx>
> Signed-off-by: Alex Shi <alex.shi@xxxxxxxxx>
> Signed-off-by: Yakui.zhao <yakui.zhao@xxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Len Brown <len.brown@xxxxxxxxx>
> ---
> drivers/acpi/processor_idle.c | 63 +++++++++++++++++-----------------------
> 1 files changed, 27 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index 7bc22a4..879af87 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -64,7 +64,6 @@
> #define _COMPONENT ACPI_PROCESSOR_COMPONENT
> ACPI_MODULE_NAME("processor_idle");
> #define ACPI_PROCESSOR_FILE_POWER "power"
> -#define US_TO_PM_TIMER_TICKS(t) ((t * (PM_TIMER_FREQUENCY/1000)) / 1000)
> #define PM_TIMER_TICK_NS (1000000000ULL/PM_TIMER_FREQUENCY)
> #define C2_OVERHEAD 1 /* 1us */
> #define C3_OVERHEAD 1 /* 1us */
> @@ -78,6 +77,10 @@ module_param(nocst, uint, 0000);
> static unsigned int latency_factor __read_mostly = 2;
> module_param(latency_factor, uint, 0644);
>
> +static s64 us_to_pm_timer_ticks(s64 t)
> +{
> + return div64_u64(t * PM_TIMER_FREQUENCY, 1000000);
> +}
> /*
> * IBM ThinkPad R40e crashes mysteriously when going into C2 or C3.
> * For now disable this. Probably a bug somewhere else.
> @@ -159,25 +162,6 @@ static struct dmi_system_id __cpuinitdata processor_power_dmi_table[] = {
> {},
> };
>
> -static inline u32 ticks_elapsed(u32 t1, u32 t2)
> -{
> - if (t2 >= t1)
> - return (t2 - t1);
> - else if (!(acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER))
> - return (((0x00FFFFFF - t1) + t2) & 0x00FFFFFF);
> - else
> - return ((0xFFFFFFFF - t1) + t2);
> -}
> -
> -static inline u32 ticks_elapsed_in_us(u32 t1, u32 t2)
> -{
> - if (t2 >= t1)
> - return PM_TIMER_TICKS_TO_US(t2 - t1);
> - else if (!(acpi_gbl_FADT.flags & ACPI_FADT_32BIT_TIMER))
> - return PM_TIMER_TICKS_TO_US(((0x00FFFFFF - t1) + t2) & 0x00FFFFFF);
> - else
> - return PM_TIMER_TICKS_TO_US((0xFFFFFFFF - t1) + t2);
> -}
>
> /*
> * Callers should disable interrupts before the call and enable
> @@ -853,7 +837,8 @@ static inline void acpi_idle_do_entry(struct acpi_processor_cx *cx)
> static int acpi_idle_enter_c1(struct cpuidle_device *dev,
> struct cpuidle_state *state)
> {
> - u32 t1, t2;
> + ktime_t kt1, kt2;
> + s64 idle_time;
> struct acpi_processor *pr;
> struct acpi_processor_cx *cx = cpuidle_get_statedata(state);
>
> @@ -871,14 +856,15 @@ static int acpi_idle_enter_c1(struct cpuidle_device *dev,
> return 0;
> }
>
> - t1 = inl(acpi_gbl_FADT.xpm_timer_block.address);
> + kt1 = ktime_get_real();
> acpi_idle_do_entry(cx);
> - t2 = inl(acpi_gbl_FADT.xpm_timer_block.address);
> + kt2 = ktime_get_real();
> + idle_time = ktime_to_us(ktime_sub(kt2, kt1));
>
> local_irq_enable();
> cx->usage++;
>
> - return ticks_elapsed_in_us(t1, t2);
> + return idle_time;
> }
>
> /**
> @@ -891,8 +877,9 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
> {
> struct acpi_processor *pr;
> struct acpi_processor_cx *cx = cpuidle_get_statedata(state);
> - u32 t1, t2;
> - int sleep_ticks = 0;
> + ktime_t kt1, kt2;
> + s64 idle_time;
> + s64 sleep_ticks = 0;
>
> pr = __get_cpu_var(processors);
>
> @@ -925,18 +912,19 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
> if (cx->type == ACPI_STATE_C3)
> ACPI_FLUSH_CPU_CACHE();
>
> - t1 = inl(acpi_gbl_FADT.xpm_timer_block.address);
> + kt1 = ktime_get_real();
> /* Tell the scheduler that we are going deep-idle: */
> sched_clock_idle_sleep_event();
> acpi_idle_do_entry(cx);
> - t2 = inl(acpi_gbl_FADT.xpm_timer_block.address);
> + kt2 = ktime_get_real();
> + idle_time = ktime_to_us(ktime_sub(kt2, kt1));
>
> #if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86)
> /* TSC could halt in idle, so notify users */
> if (tsc_halts_in_c(cx->type))
> mark_tsc_unstable("TSC halts in idle");;
> #endif
> - sleep_ticks = ticks_elapsed(t1, t2);
> + sleep_ticks = us_to_pm_timer_ticks(idle_time);
>
> /* Tell the scheduler how much we idled: */
> sched_clock_idle_wakeup_event(sleep_ticks*PM_TIMER_TICK_NS);
> @@ -948,7 +936,7 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
>
> acpi_state_timer_broadcast(pr, cx, 0);
> cx->time += sleep_ticks;
> - return ticks_elapsed_in_us(t1, t2);
> + return idle_time;
> }
>
> static int c3_cpu_count;
> @@ -966,8 +954,10 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
> {
> struct acpi_processor *pr;
> struct acpi_processor_cx *cx = cpuidle_get_statedata(state);
> - u32 t1, t2;
> - int sleep_ticks = 0;
> + ktime_t kt1, kt2;
> + s64 idle_time;
> + s64 sleep_ticks = 0;
> +
>
> pr = __get_cpu_var(processors);
>
> @@ -1034,9 +1024,10 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
> ACPI_FLUSH_CPU_CACHE();
> }
>
> - t1 = inl(acpi_gbl_FADT.xpm_timer_block.address);
> + kt1 = ktime_get_real();
> acpi_idle_do_entry(cx);
> - t2 = inl(acpi_gbl_FADT.xpm_timer_block.address);
> + kt2 = ktime_get_real();
> + idle_time = ktime_to_us(ktime_sub(kt2, kt1));
>
> /* Re-enable bus master arbitration */
> if (pr->flags.bm_check && pr->flags.bm_control) {
> @@ -1051,7 +1042,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
> if (tsc_halts_in_c(ACPI_STATE_C3))
> mark_tsc_unstable("TSC halts in idle");
> #endif
> - sleep_ticks = ticks_elapsed(t1, t2);
> + sleep_ticks = us_to_pm_timer_ticks(idle_time);
> /* Tell the scheduler how much we idled: */
> sched_clock_idle_wakeup_event(sleep_ticks*PM_TIMER_TICK_NS);
>
> @@ -1062,7 +1053,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
>
> acpi_state_timer_broadcast(pr, cx, 0);
> cx->time += sleep_ticks;
> - return ticks_elapsed_in_us(t1, t2);
> + return idle_time;
> }
>
> struct cpuidle_driver acpi_idle_driver = {
> --
--
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