On 11/13/2012 10:52 PM, Julius Werner wrote:
Many cpuidle drivers measure their time spent in an idle state by reading the wallclock time before and after idling and calculating the difference. This leads to erroneous results when the wallclock time gets updated by another processor in the meantime, adding that clock adjustment to the idle state's time counter.
If the clock adjustment was negative, the result is even worse due to an erroneous cast from int to unsigned long long of the last_residency variable. The negative 32 bit integer will zero-extend and result in a forward time jump of roughly four billion milliseconds or 1.3 hours on the idle state residency counter.
This patch changes all affected cpuidle drivers to use the monotonic clock for their measurements instead. It also removes the erroneous cast, making sure that negative residency values are applied correctly even though they should not appear anymore.
Signed-off-by: Julius Werner jwerner@chromium.org
arch/powerpc/platforms/pseries/processor_idle.c | 4 ++-- drivers/acpi/processor_idle.c | 12 ++++++------ drivers/cpuidle/cpuidle.c | 3 +-- drivers/idle/intel_idle.c | 13 ++++--------- 4 files changed, 13 insertions(+), 19 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/processor_idle.c b/arch/powerpc/platforms/pseries/processor_idle.c index 45d00e5..4d806b4 100644 --- a/arch/powerpc/platforms/pseries/processor_idle.c +++ b/arch/powerpc/platforms/pseries/processor_idle.c @@ -36,7 +36,7 @@ static struct cpuidle_state *cpuidle_state_table; static inline void idle_loop_prolog(unsigned long *in_purr, ktime_t *kt_before) {
- *kt_before = ktime_get_real();
- *kt_before = ktime_get(); *in_purr = mfspr(SPRN_PURR); /*
- Indicate to the HV that we are idle. Now would be
@@ -50,7 +50,7 @@ static inline s64 idle_loop_epilog(unsigned long in_purr, ktime_t kt_before) get_lppaca()->wait_state_cycles += mfspr(SPRN_PURR) - in_purr; get_lppaca()->idle = 0;
- return ktime_to_us(ktime_sub(ktime_get_real(), kt_before));
- return ktime_to_us(ktime_sub(ktime_get(), kt_before));
} static int snooze_loop(struct cpuidle_device *dev, diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index e8086c7..8c98d73 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -751,9 +751,9 @@ static int acpi_idle_enter_c1(struct cpuidle_device *dev, lapic_timer_state_broadcast(pr, cx, 1);
- kt1 = ktime_get_real();
- kt1 = ktime_get(); acpi_idle_do_entry(cx);
- kt2 = ktime_get_real();
- kt2 = ktime_get(); idle_time = ktime_to_us(ktime_sub(kt2, kt1));
/* Update device last_residency*/ @@ -843,11 +843,11 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev, if (cx->type == ACPI_STATE_C3) ACPI_FLUSH_CPU_CACHE();
- kt1 = ktime_get_real();
- kt1 = ktime_get(); /* Tell the scheduler that we are going deep-idle: */ sched_clock_idle_sleep_event(); acpi_idle_do_entry(cx);
- kt2 = ktime_get_real();
- kt2 = ktime_get(); idle_time_ns = ktime_to_ns(ktime_sub(kt2, kt1)); idle_time = idle_time_ns; do_div(idle_time, NSEC_PER_USEC);
@@ -934,7 +934,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, */ lapic_timer_state_broadcast(pr, cx, 1);
- kt1 = ktime_get_real();
- kt1 = ktime_get(); /*
- disable bus master
- bm_check implies we need ARB_DIS
@@ -965,7 +965,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, c3_cpu_count--; raw_spin_unlock(&c3_lock); }
- kt2 = ktime_get_real();
- kt2 = ktime_get(); idle_time_ns = ktime_to_ns(ktime_sub(kt2, kt1)); idle_time = idle_time_ns; do_div(idle_time, NSEC_PER_USEC);
Maybe you can remove all these computations and set the flag en_core_tk_irqen for the driver ? That will be handled by the cpuidle framework, no ?
Same comment for the intel_idle driver.
Thanks -- Daniel
Maybe you can remove all these computations and set the flag en_core_tk_irqen for the driver ? That will be handled by the cpuidle framework, no ?
Same comment for the intel_idle driver.
Yeah, I thought about that, too. I was a little too afraid of touching the sched_clock_idle_wakeup_event() parameter that is tied to the measurement, but it seems to have been vestigial for some time now and other drivers also just set it 0. I will whip up another version of the patch (won't change the PPC further though, if this version works I would just leave it at that... thanks for testing, Deepthi).
Many cpuidle drivers measure their time spent in an idle state by reading the wallclock time before and after idling and calculating the difference. This leads to erroneous results when the wallclock time gets updated by another processor in the meantime, adding that clock adjustment to the idle state's time counter.
If the clock adjustment was negative, the result is even worse due to an erroneous cast from int to unsigned long long of the last_residency variable. The negative 32 bit integer will zero-extend and result in a forward time jump of roughly four billion milliseconds or 1.3 hours on the idle state residency counter.
This patch changes all affected cpuidle drivers to either use the monotonic clock for their measurements or make use of the generic time measurement wrapper in cpuidle.c, which was already working correctly. Some superfluous CLIs/STIs in the ACPI code are removed (interrupts should always already be disabled before entering the idle function, and not get reenabled until the generic wrapper has performed its second measurement). It also removes the erroneous cast, making sure that negative residency values are applied correctly even though they should not appear anymore.
Signed-off-by: Julius Werner jwerner@chromium.org --- arch/powerpc/platforms/pseries/processor_idle.c | 4 +- drivers/acpi/processor_idle.c | 57 +--------------------- drivers/cpuidle/cpuidle.c | 3 +- drivers/idle/intel_idle.c | 14 +----- 4 files changed, 7 insertions(+), 71 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/processor_idle.c b/arch/powerpc/platforms/pseries/processor_idle.c index 45d00e5..4d806b4 100644 --- a/arch/powerpc/platforms/pseries/processor_idle.c +++ b/arch/powerpc/platforms/pseries/processor_idle.c @@ -36,7 +36,7 @@ static struct cpuidle_state *cpuidle_state_table; static inline void idle_loop_prolog(unsigned long *in_purr, ktime_t *kt_before) {
- *kt_before = ktime_get_real(); + *kt_before = ktime_get(); *in_purr = mfspr(SPRN_PURR); /* * Indicate to the HV that we are idle. Now would be @@ -50,7 +50,7 @@ static inline s64 idle_loop_epilog(unsigned long in_purr, ktime_t kt_before) get_lppaca()->wait_state_cycles += mfspr(SPRN_PURR) - in_purr; get_lppaca()->idle = 0;
- return ktime_to_us(ktime_sub(ktime_get_real(), kt_before)); + return ktime_to_us(ktime_sub(ktime_get(), kt_before)); }
static int snooze_loop(struct cpuidle_device *dev, diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index e8086c7..f1a5da4 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -735,31 +735,18 @@ static inline void acpi_idle_do_entry(struct acpi_processor_cx *cx) static int acpi_idle_enter_c1(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { - ktime_t kt1, kt2; - s64 idle_time; struct acpi_processor *pr; struct cpuidle_state_usage *state_usage = &dev->states_usage[index]; struct acpi_processor_cx *cx = cpuidle_get_statedata(state_usage);
pr = __this_cpu_read(processors); - dev->last_residency = 0;
if (unlikely(!pr)) return -EINVAL;
- local_irq_disable(); - - lapic_timer_state_broadcast(pr, cx, 1); - kt1 = ktime_get_real(); acpi_idle_do_entry(cx); - kt2 = ktime_get_real(); - idle_time = ktime_to_us(ktime_sub(kt2, kt1)); - - /* Update device last_residency*/ - dev->last_residency = (int)idle_time;
- local_irq_enable(); lapic_timer_state_broadcast(pr, cx, 0);
return index; @@ -806,19 +793,12 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev, struct acpi_processor *pr; struct cpuidle_state_usage *state_usage = &dev->states_usage[index]; struct acpi_processor_cx *cx = cpuidle_get_statedata(state_usage); - ktime_t kt1, kt2; - s64 idle_time_ns; - s64 idle_time;
pr = __this_cpu_read(processors); - dev->last_residency = 0;
if (unlikely(!pr)) return -EINVAL;
- local_irq_disable(); - - if (cx->entry_method != ACPI_CSTATE_FFH) { current_thread_info()->status &= ~TS_POLLING; /* @@ -829,7 +809,6 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
if (unlikely(need_resched())) { current_thread_info()->status |= TS_POLLING; - local_irq_enable(); return -EINVAL; } } @@ -843,22 +822,12 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev, if (cx->type == ACPI_STATE_C3) ACPI_FLUSH_CPU_CACHE();
- kt1 = ktime_get_real(); /* Tell the scheduler that we are going deep-idle: */ sched_clock_idle_sleep_event(); acpi_idle_do_entry(cx); - kt2 = ktime_get_real(); - idle_time_ns = ktime_to_ns(ktime_sub(kt2, kt1)); - idle_time = idle_time_ns; - do_div(idle_time, NSEC_PER_USEC);
- /* Update device last_residency*/ - dev->last_residency = (int)idle_time; + sched_clock_idle_wakeup_event(0);
- /* Tell the scheduler how much we idled: */ - sched_clock_idle_wakeup_event(idle_time_ns); - - local_irq_enable(); if (cx->entry_method != ACPI_CSTATE_FFH) current_thread_info()->status |= TS_POLLING;
@@ -883,13 +852,8 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, struct acpi_processor *pr; struct cpuidle_state_usage *state_usage = &dev->states_usage[index]; struct acpi_processor_cx *cx = cpuidle_get_statedata(state_usage); - ktime_t kt1, kt2; - s64 idle_time_ns; - s64 idle_time; -
pr = __this_cpu_read(processors); - dev->last_residency = 0;
if (unlikely(!pr)) return -EINVAL; @@ -899,16 +863,11 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, return drv->states[drv->safe_state_index].enter(dev, drv, drv->safe_state_index); } else { - local_irq_disable(); acpi_safe_halt(); - local_irq_enable(); return -EBUSY; } }
- local_irq_disable(); - - if (cx->entry_method != ACPI_CSTATE_FFH) { current_thread_info()->status &= ~TS_POLLING; /* @@ -919,7 +878,6 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
if (unlikely(need_resched())) { current_thread_info()->status |= TS_POLLING; - local_irq_enable(); return -EINVAL; } } @@ -934,7 +892,6 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, */ lapic_timer_state_broadcast(pr, cx, 1);
- kt1 = ktime_get_real(); /* * disable bus master * bm_check implies we need ARB_DIS @@ -965,18 +922,9 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, c3_cpu_count--; raw_spin_unlock(&c3_lock); } - kt2 = ktime_get_real(); - idle_time_ns = ktime_to_ns(ktime_sub(kt2, kt1)); - idle_time = idle_time_ns; - do_div(idle_time, NSEC_PER_USEC); - - /* Update device last_residency*/ - dev->last_residency = (int)idle_time;
- /* Tell the scheduler how much we idled: */ - sched_clock_idle_wakeup_event(idle_time_ns); + sched_clock_idle_wakeup_event(0);
- local_irq_enable(); if (cx->entry_method != ACPI_CSTATE_FFH) current_thread_info()->status |= TS_POLLING;
@@ -987,6 +935,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, struct cpuidle_driver acpi_idle_driver = { .name = "acpi_idle", .owner = THIS_MODULE, + .en_core_tk_irqen = 1, };
/** diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 7f15b85..1536edd 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -109,8 +109,7 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, /* This can be moved to within driver enter routine * but that results in multiple copies of same code. */ - dev->states_usage[entered_state].time += - (unsigned long long)dev->last_residency; + dev->states_usage[entered_state].time += dev->last_residency; dev->states_usage[entered_state].usage++; } else { dev->last_residency = 0; diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index b0f6b4c..c49c04d 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -56,7 +56,6 @@ #include <linux/kernel.h> #include <linux/cpuidle.h> #include <linux/clockchips.h> -#include <linux/hrtimer.h> /* ktime_get_real() */ #include <trace/events/power.h> #include <linux/sched.h> #include <linux/notifier.h> @@ -72,6 +71,7 @@ static struct cpuidle_driver intel_idle_driver = { .name = "intel_idle", .owner = THIS_MODULE, + .en_core_tk_irqen = 1, }; /* intel_idle.max_cstate=0 disables driver */ static int max_cstate = MWAIT_MAX_NUM_CSTATES - 1; @@ -281,8 +281,6 @@ static int intel_idle(struct cpuidle_device *dev, struct cpuidle_state_usage *state_usage = &dev->states_usage[index]; unsigned long eax = (unsigned long)cpuidle_get_statedata(state_usage); unsigned int cstate; - ktime_t kt_before, kt_after; - s64 usec_delta; int cpu = smp_processor_id();
cstate = (((eax) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) + 1; @@ -297,8 +295,6 @@ static int intel_idle(struct cpuidle_device *dev, if (!(lapic_timer_reliable_states & (1 << (cstate)))) clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
- kt_before = ktime_get_real(); - stop_critical_timings(); if (!need_resched()) {
@@ -310,17 +306,9 @@ static int intel_idle(struct cpuidle_device *dev,
start_critical_timings();
- kt_after = ktime_get_real(); - usec_delta = ktime_to_us(ktime_sub(kt_after, kt_before)); - - local_irq_enable(); - if (!(lapic_timer_reliable_states & (1 << (cstate)))) clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
- /* Update cpuidle counters */ - dev->last_residency = (int)usec_delta; - return index; }
Hi all,
The code looks correct and inviting to me as it has led to good cleanups. I dont think passing 0 as the argument to the function sched_clock_idle_wakeup_event() should lead to problems,as it does not do anything useful with the passed arguments.
My only curiosity is what was the purpose of passing idle residency time to sched_clock_idle_wakeup_event() when this data could always be retrieved from dev->last_residency for each cpu,which gets almost immediately updated.
But this does not seem to come in way of this patch for now.Anyway I have added Peter to the list so that he can opine about this issue if possible and needed.
Reviewed-by: Preeti U Murthy preeti@linux.vnet.ibm.com
Regards Preeti U Murthy
On 11/15/2012 04:04 AM, Preeti Murthy wrote:
Hi all,
The code looks correct and inviting to me as it has led to good cleanups. I dont think passing 0 as the argument to the function sched_clock_idle_wakeup_event() should lead to problems,as it does not do anything useful with the passed arguments.
My only curiosity is what was the purpose of passing idle residency time to sched_clock_idle_wakeup_event() when this data could always be retrieved from dev->last_residency for each cpu,which gets almost immediately updated.
sched_clock_idle_wakeup_event() is part of the scheduler. The scheduler doesn't know what a cpuidle_device is, and probably should not grow such a dependency.
cheers, -Len Brown, Intel Open Source Technology Center
But this does not seem to come in way of this patch for now.Anyway I have added Peter to the list so that he can opine about this issue if possible and needed.
Reviewed-by: Preeti U Murthy preeti@linux.vnet.ibm.com
Regards Preeti U Murthy
On 11/15/2012 02:56 AM, Julius Werner wrote:
Many cpuidle drivers measure their time spent in an idle state by reading the wallclock time before and after idling and calculating the difference. This leads to erroneous results when the wallclock time gets updated by another processor in the meantime, adding that clock adjustment to the idle state's time counter.
If the clock adjustment was negative, the result is even worse due to an erroneous cast from int to unsigned long long of the last_residency variable. The negative 32 bit integer will zero-extend and result in a forward time jump of roughly four billion milliseconds or 1.3 hours on the idle state residency counter.
This patch changes all affected cpuidle drivers to either use the monotonic clock for their measurements or make use of the generic time measurement wrapper in cpuidle.c, which was already working correctly. Some superfluous CLIs/STIs in the ACPI code are removed (interrupts should always already be disabled before entering the idle function, and not get reenabled until the generic wrapper has performed its second measurement). It also removes the erroneous cast, making sure that negative residency values are applied correctly even though they should not appear anymore.
Signed-off-by: Julius Werner jwerner@chromium.org
Tested on a Core 2 Duo (processor_idle driver).
Tested-by: Daniel Lezcano daniel.lezcano@linaro.org Acked-by: Daniel Lezcano daniel.lezcano@linaro.org
On Wednesday, November 14, 2012 05:56:30 PM Julius Werner wrote:
Many cpuidle drivers measure their time spent in an idle state by reading the wallclock time before and after idling and calculating the difference. This leads to erroneous results when the wallclock time gets updated by another processor in the meantime, adding that clock adjustment to the idle state's time counter.
If the clock adjustment was negative, the result is even worse due to an erroneous cast from int to unsigned long long of the last_residency variable. The negative 32 bit integer will zero-extend and result in a forward time jump of roughly four billion milliseconds or 1.3 hours on the idle state residency counter.
This patch changes all affected cpuidle drivers to either use the monotonic clock for their measurements or make use of the generic time measurement wrapper in cpuidle.c, which was already working correctly. Some superfluous CLIs/STIs in the ACPI code are removed (interrupts should always already be disabled before entering the idle function, and not get reenabled until the generic wrapper has performed its second measurement). It also removes the erroneous cast, making sure that negative residency values are applied correctly even though they should not appear anymore.
Signed-off-by: Julius Werner jwerner@chromium.org
Len, I need your ACK on intel_idle change in this patch if you agree with it.
Thanks, Rafael
arch/powerpc/platforms/pseries/processor_idle.c | 4 +- drivers/acpi/processor_idle.c | 57 +--------------------- drivers/cpuidle/cpuidle.c | 3 +- drivers/idle/intel_idle.c | 14 +----- 4 files changed, 7 insertions(+), 71 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/processor_idle.c b/arch/powerpc/platforms/pseries/processor_idle.c index 45d00e5..4d806b4 100644 --- a/arch/powerpc/platforms/pseries/processor_idle.c +++ b/arch/powerpc/platforms/pseries/processor_idle.c @@ -36,7 +36,7 @@ static struct cpuidle_state *cpuidle_state_table; static inline void idle_loop_prolog(unsigned long *in_purr, ktime_t *kt_before) {
- *kt_before = ktime_get_real();
- *kt_before = ktime_get(); *in_purr = mfspr(SPRN_PURR); /*
- Indicate to the HV that we are idle. Now would be
@@ -50,7 +50,7 @@ static inline s64 idle_loop_epilog(unsigned long in_purr, ktime_t kt_before) get_lppaca()->wait_state_cycles += mfspr(SPRN_PURR) - in_purr; get_lppaca()->idle = 0;
- return ktime_to_us(ktime_sub(ktime_get_real(), kt_before));
- return ktime_to_us(ktime_sub(ktime_get(), kt_before));
} static int snooze_loop(struct cpuidle_device *dev, diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index e8086c7..f1a5da4 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -735,31 +735,18 @@ static inline void acpi_idle_do_entry(struct acpi_processor_cx *cx) static int acpi_idle_enter_c1(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) {
- ktime_t kt1, kt2;
- s64 idle_time; struct acpi_processor *pr; struct cpuidle_state_usage *state_usage = &dev->states_usage[index]; struct acpi_processor_cx *cx = cpuidle_get_statedata(state_usage);
pr = __this_cpu_read(processors);
- dev->last_residency = 0;
if (unlikely(!pr)) return -EINVAL;
- local_irq_disable();
- lapic_timer_state_broadcast(pr, cx, 1);
- kt1 = ktime_get_real(); acpi_idle_do_entry(cx);
- kt2 = ktime_get_real();
- idle_time = ktime_to_us(ktime_sub(kt2, kt1));
- /* Update device last_residency*/
- dev->last_residency = (int)idle_time;
- local_irq_enable(); lapic_timer_state_broadcast(pr, cx, 0);
return index; @@ -806,19 +793,12 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev, struct acpi_processor *pr; struct cpuidle_state_usage *state_usage = &dev->states_usage[index]; struct acpi_processor_cx *cx = cpuidle_get_statedata(state_usage);
- ktime_t kt1, kt2;
- s64 idle_time_ns;
- s64 idle_time;
pr = __this_cpu_read(processors);
- dev->last_residency = 0;
if (unlikely(!pr)) return -EINVAL;
- local_irq_disable();
- if (cx->entry_method != ACPI_CSTATE_FFH) { current_thread_info()->status &= ~TS_POLLING; /*
@@ -829,7 +809,6 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev, if (unlikely(need_resched())) { current_thread_info()->status |= TS_POLLING;
local_irq_enable(); return -EINVAL;@@ -843,22 +822,12 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev, if (cx->type == ACPI_STATE_C3) ACPI_FLUSH_CPU_CACHE();
- kt1 = ktime_get_real(); /* Tell the scheduler that we are going deep-idle: */ sched_clock_idle_sleep_event(); acpi_idle_do_entry(cx);
- kt2 = ktime_get_real();
- idle_time_ns = ktime_to_ns(ktime_sub(kt2, kt1));
- idle_time = idle_time_ns;
- do_div(idle_time, NSEC_PER_USEC);
- /* Update device last_residency*/
- dev->last_residency = (int)idle_time;
- sched_clock_idle_wakeup_event(0);
- /* Tell the scheduler how much we idled: */
- sched_clock_idle_wakeup_event(idle_time_ns);
- local_irq_enable(); if (cx->entry_method != ACPI_CSTATE_FFH) current_thread_info()->status |= TS_POLLING;
@@ -883,13 +852,8 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, struct acpi_processor *pr; struct cpuidle_state_usage *state_usage = &dev->states_usage[index]; struct acpi_processor_cx *cx = cpuidle_get_statedata(state_usage);
- ktime_t kt1, kt2;
- s64 idle_time_ns;
- s64 idle_time;
pr = __this_cpu_read(processors);
- dev->last_residency = 0;
if (unlikely(!pr)) return -EINVAL; @@ -899,16 +863,11 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, return drv->states[drv->safe_state_index].enter(dev, drv, drv->safe_state_index); } else {
local_irq_disable(); acpi_safe_halt();local_irq_enable(); return -EBUSY;
- local_irq_disable();
- if (cx->entry_method != ACPI_CSTATE_FFH) { current_thread_info()->status &= ~TS_POLLING; /*
@@ -919,7 +878,6 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, if (unlikely(need_resched())) { current_thread_info()->status |= TS_POLLING;
local_irq_enable(); return -EINVAL;@@ -934,7 +892,6 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, */ lapic_timer_state_broadcast(pr, cx, 1);
- kt1 = ktime_get_real(); /*
- disable bus master
- bm_check implies we need ARB_DIS
@@ -965,18 +922,9 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, c3_cpu_count--; raw_spin_unlock(&c3_lock); }
- kt2 = ktime_get_real();
- idle_time_ns = ktime_to_ns(ktime_sub(kt2, kt1));
- idle_time = idle_time_ns;
- do_div(idle_time, NSEC_PER_USEC);
- /* Update device last_residency*/
- dev->last_residency = (int)idle_time;
- /* Tell the scheduler how much we idled: */
- sched_clock_idle_wakeup_event(idle_time_ns);
- sched_clock_idle_wakeup_event(0);
- local_irq_enable(); if (cx->entry_method != ACPI_CSTATE_FFH) current_thread_info()->status |= TS_POLLING;
@@ -987,6 +935,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, struct cpuidle_driver acpi_idle_driver = { .name = "acpi_idle", .owner = THIS_MODULE,
- .en_core_tk_irqen = 1,
}; /** diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 7f15b85..1536edd 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -109,8 +109,7 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, /* This can be moved to within driver enter routine * but that results in multiple copies of same code. */
dev->states_usage[entered_state].time +=(unsigned long long)dev->last_residency;
dev->states_usage[entered_state].time += dev->last_residency;diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index b0f6b4c..c49c04d 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -56,7 +56,6 @@ #include <linux/kernel.h> #include <linux/cpuidle.h> #include <linux/clockchips.h> -#include <linux/hrtimer.h> /* ktime_get_real() */ #include <trace/events/power.h> #include <linux/sched.h> #include <linux/notifier.h> @@ -72,6 +71,7 @@ static struct cpuidle_driver intel_idle_driver = { .name = "intel_idle", .owner = THIS_MODULE,
- .en_core_tk_irqen = 1,
}; /* intel_idle.max_cstate=0 disables driver */ static int max_cstate = MWAIT_MAX_NUM_CSTATES - 1; @@ -281,8 +281,6 @@ static int intel_idle(struct cpuidle_device *dev, struct cpuidle_state_usage *state_usage = &dev->states_usage[index]; unsigned long eax = (unsigned long)cpuidle_get_statedata(state_usage); unsigned int cstate;
- ktime_t kt_before, kt_after;
- s64 usec_delta; int cpu = smp_processor_id();
cstate = (((eax) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) + 1; @@ -297,8 +295,6 @@ static int intel_idle(struct cpuidle_device *dev, if (!(lapic_timer_reliable_states & (1 << (cstate)))) clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
- kt_before = ktime_get_real();
- stop_critical_timings(); if (!need_resched()) {
@@ -310,17 +306,9 @@ static int intel_idle(struct cpuidle_device *dev, start_critical_timings();
- kt_after = ktime_get_real();
- usec_delta = ktime_to_us(ktime_sub(kt_after, kt_before));
- local_irq_enable();
- if (!(lapic_timer_reliable_states & (1 << (cstate)))) clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
- /* Update cpuidle counters */
- dev->last_residency = (int)usec_delta;
- return index;
}
On Wednesday, November 14, 2012 05:56:30 PM Julius Werner wrote:
Many cpuidle drivers measure their time spent in an idle state by reading the wallclock time before and after idling and calculating the difference. This leads to erroneous results when the wallclock time gets updated by another processor in the meantime, adding that clock adjustment to the idle state's time counter.
If the clock adjustment was negative, the result is even worse due to an erroneous cast from int to unsigned long long of the last_residency variable. The negative 32 bit integer will zero-extend and result in a forward time jump of roughly four billion milliseconds or 1.3 hours on the idle state residency counter.
This patch changes all affected cpuidle drivers to either use the monotonic clock for their measurements or make use of the generic time measurement wrapper in cpuidle.c, which was already working correctly. Some superfluous CLIs/STIs in the ACPI code are removed (interrupts should always already be disabled before entering the idle function, and not get reenabled until the generic wrapper has performed its second measurement). It also removes the erroneous cast, making sure that negative residency values are applied correctly even though they should not appear anymore.
Applied to the linux-next branch of the linux-pm.git tree.
Thanks, Rafael
Signed-off-by: Julius Werner jwerner@chromium.org
arch/powerpc/platforms/pseries/processor_idle.c | 4 +- drivers/acpi/processor_idle.c | 57 +--------------------- drivers/cpuidle/cpuidle.c | 3 +- drivers/idle/intel_idle.c | 14 +----- 4 files changed, 7 insertions(+), 71 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/processor_idle.c b/arch/powerpc/platforms/pseries/processor_idle.c index 45d00e5..4d806b4 100644 --- a/arch/powerpc/platforms/pseries/processor_idle.c +++ b/arch/powerpc/platforms/pseries/processor_idle.c @@ -36,7 +36,7 @@ static struct cpuidle_state *cpuidle_state_table; static inline void idle_loop_prolog(unsigned long *in_purr, ktime_t *kt_before) {
- *kt_before = ktime_get_real();
- *kt_before = ktime_get(); *in_purr = mfspr(SPRN_PURR); /*
- Indicate to the HV that we are idle. Now would be
@@ -50,7 +50,7 @@ static inline s64 idle_loop_epilog(unsigned long in_purr, ktime_t kt_before) get_lppaca()->wait_state_cycles += mfspr(SPRN_PURR) - in_purr; get_lppaca()->idle = 0;
- return ktime_to_us(ktime_sub(ktime_get_real(), kt_before));
- return ktime_to_us(ktime_sub(ktime_get(), kt_before));
} static int snooze_loop(struct cpuidle_device *dev, diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index e8086c7..f1a5da4 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -735,31 +735,18 @@ static inline void acpi_idle_do_entry(struct acpi_processor_cx *cx) static int acpi_idle_enter_c1(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) {
- ktime_t kt1, kt2;
- s64 idle_time; struct acpi_processor *pr; struct cpuidle_state_usage *state_usage = &dev->states_usage[index]; struct acpi_processor_cx *cx = cpuidle_get_statedata(state_usage);
pr = __this_cpu_read(processors);
- dev->last_residency = 0;
if (unlikely(!pr)) return -EINVAL;
- local_irq_disable();
- lapic_timer_state_broadcast(pr, cx, 1);
- kt1 = ktime_get_real(); acpi_idle_do_entry(cx);
- kt2 = ktime_get_real();
- idle_time = ktime_to_us(ktime_sub(kt2, kt1));
- /* Update device last_residency*/
- dev->last_residency = (int)idle_time;
- local_irq_enable(); lapic_timer_state_broadcast(pr, cx, 0);
return index; @@ -806,19 +793,12 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev, struct acpi_processor *pr; struct cpuidle_state_usage *state_usage = &dev->states_usage[index]; struct acpi_processor_cx *cx = cpuidle_get_statedata(state_usage);
- ktime_t kt1, kt2;
- s64 idle_time_ns;
- s64 idle_time;
pr = __this_cpu_read(processors);
- dev->last_residency = 0;
if (unlikely(!pr)) return -EINVAL;
- local_irq_disable();
- if (cx->entry_method != ACPI_CSTATE_FFH) { current_thread_info()->status &= ~TS_POLLING; /*
@@ -829,7 +809,6 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev, if (unlikely(need_resched())) { current_thread_info()->status |= TS_POLLING;
local_irq_enable(); return -EINVAL;@@ -843,22 +822,12 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev, if (cx->type == ACPI_STATE_C3) ACPI_FLUSH_CPU_CACHE();
- kt1 = ktime_get_real(); /* Tell the scheduler that we are going deep-idle: */ sched_clock_idle_sleep_event(); acpi_idle_do_entry(cx);
- kt2 = ktime_get_real();
- idle_time_ns = ktime_to_ns(ktime_sub(kt2, kt1));
- idle_time = idle_time_ns;
- do_div(idle_time, NSEC_PER_USEC);
- /* Update device last_residency*/
- dev->last_residency = (int)idle_time;
- sched_clock_idle_wakeup_event(0);
- /* Tell the scheduler how much we idled: */
- sched_clock_idle_wakeup_event(idle_time_ns);
- local_irq_enable(); if (cx->entry_method != ACPI_CSTATE_FFH) current_thread_info()->status |= TS_POLLING;
@@ -883,13 +852,8 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, struct acpi_processor *pr; struct cpuidle_state_usage *state_usage = &dev->states_usage[index]; struct acpi_processor_cx *cx = cpuidle_get_statedata(state_usage);
- ktime_t kt1, kt2;
- s64 idle_time_ns;
- s64 idle_time;
pr = __this_cpu_read(processors);
- dev->last_residency = 0;
if (unlikely(!pr)) return -EINVAL; @@ -899,16 +863,11 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, return drv->states[drv->safe_state_index].enter(dev, drv, drv->safe_state_index); } else {
local_irq_disable(); acpi_safe_halt();local_irq_enable(); return -EBUSY;
- local_irq_disable();
- if (cx->entry_method != ACPI_CSTATE_FFH) { current_thread_info()->status &= ~TS_POLLING; /*
@@ -919,7 +878,6 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, if (unlikely(need_resched())) { current_thread_info()->status |= TS_POLLING;
local_irq_enable(); return -EINVAL;@@ -934,7 +892,6 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, */ lapic_timer_state_broadcast(pr, cx, 1);
- kt1 = ktime_get_real(); /*
- disable bus master
- bm_check implies we need ARB_DIS
@@ -965,18 +922,9 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, c3_cpu_count--; raw_spin_unlock(&c3_lock); }
- kt2 = ktime_get_real();
- idle_time_ns = ktime_to_ns(ktime_sub(kt2, kt1));
- idle_time = idle_time_ns;
- do_div(idle_time, NSEC_PER_USEC);
- /* Update device last_residency*/
- dev->last_residency = (int)idle_time;
- /* Tell the scheduler how much we idled: */
- sched_clock_idle_wakeup_event(idle_time_ns);
- sched_clock_idle_wakeup_event(0);
- local_irq_enable(); if (cx->entry_method != ACPI_CSTATE_FFH) current_thread_info()->status |= TS_POLLING;
@@ -987,6 +935,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, struct cpuidle_driver acpi_idle_driver = { .name = "acpi_idle", .owner = THIS_MODULE,
- .en_core_tk_irqen = 1,
}; /** diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 7f15b85..1536edd 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -109,8 +109,7 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, /* This can be moved to within driver enter routine * but that results in multiple copies of same code. */
dev->states_usage[entered_state].time +=(unsigned long long)dev->last_residency;
dev->states_usage[entered_state].time += dev->last_residency;diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index b0f6b4c..c49c04d 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -56,7 +56,6 @@ #include <linux/kernel.h> #include <linux/cpuidle.h> #include <linux/clockchips.h> -#include <linux/hrtimer.h> /* ktime_get_real() */ #include <trace/events/power.h> #include <linux/sched.h> #include <linux/notifier.h> @@ -72,6 +71,7 @@ static struct cpuidle_driver intel_idle_driver = { .name = "intel_idle", .owner = THIS_MODULE,
- .en_core_tk_irqen = 1,
}; /* intel_idle.max_cstate=0 disables driver */ static int max_cstate = MWAIT_MAX_NUM_CSTATES - 1; @@ -281,8 +281,6 @@ static int intel_idle(struct cpuidle_device *dev, struct cpuidle_state_usage *state_usage = &dev->states_usage[index]; unsigned long eax = (unsigned long)cpuidle_get_statedata(state_usage); unsigned int cstate;
- ktime_t kt_before, kt_after;
- s64 usec_delta; int cpu = smp_processor_id();
cstate = (((eax) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) + 1; @@ -297,8 +295,6 @@ static int intel_idle(struct cpuidle_device *dev, if (!(lapic_timer_reliable_states & (1 << (cstate)))) clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
- kt_before = ktime_get_real();
- stop_critical_timings(); if (!need_resched()) {
@@ -310,17 +306,9 @@ static int intel_idle(struct cpuidle_device *dev, start_critical_timings();
- kt_after = ktime_get_real();
- usec_delta = ktime_to_us(ktime_sub(kt_after, kt_before));
- local_irq_enable();
- if (!(lapic_timer_reliable_states & (1 << (cstate)))) clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
- /* Update cpuidle counters */
- dev->last_residency = (int)usec_delta;
- return index;
}
-
Daniel Lezcano -
Julius Werner -
Len Brown -
Preeti Murthy -
Rafael J. Wysocki