diff options
Diffstat (limited to 'drivers/cpuidle/governors')
| -rw-r--r-- | drivers/cpuidle/governors/ladder.c | 12 | ||||
| -rw-r--r-- | drivers/cpuidle/governors/menu.c | 192 |
2 files changed, 116 insertions, 88 deletions
diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c index 9b784051ec1..9f08e8cce1a 100644 --- a/drivers/cpuidle/governors/ladder.c +++ b/drivers/cpuidle/governors/ladder.c @@ -192,14 +192,4 @@ static int __init init_ladder(void) return cpuidle_register_governor(&ladder_governor); } -/** - * exit_ladder - exits the governor - */ -static void __exit exit_ladder(void) -{ - cpuidle_unregister_governor(&ladder_governor); -} - -MODULE_LICENSE("GPL"); -module_init(init_ladder); -module_exit(exit_ladder); +postcore_initcall(init_ladder); diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index bc580b67a65..c4f80c15a48 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -21,6 +21,15 @@ #include <linux/math64.h> #include <linux/module.h> +/* + * Please note when changing the tuning values: + * If (MAX_INTERESTING-1) * RESOLUTION > UINT_MAX, the result of + * a scaling operation multiplication may overflow on 32 bit platforms. + * In that case, #define RESOLUTION as ULL to get 64 bit result: + * #define RESOLUTION 1024ULL + * + * The default values do not overflow. + */ #define BUCKETS 12 #define INTERVALS 8 #define RESOLUTION 1024 @@ -113,12 +122,11 @@ struct menu_device { int last_state_idx; int needs_update; - unsigned int expected_us; - u64 predicted_us; - unsigned int exit_us; + unsigned int next_timer_us; + unsigned int predicted_us; unsigned int bucket; - u64 correction_factor[BUCKETS]; - u32 intervals[INTERVALS]; + unsigned int correction_factor[BUCKETS]; + unsigned int intervals[INTERVALS]; int interval_ptr; }; @@ -199,16 +207,20 @@ static u64 div_round64(u64 dividend, u32 divisor) */ static void get_typical_interval(struct menu_device *data) { - int i = 0, divisor = 0; - uint64_t max = 0, avg = 0, stddev = 0; - int64_t thresh = LLONG_MAX; /* Discard outliers above this value. */ + int i, divisor; + unsigned int max, thresh; + uint64_t avg, stddev; + + thresh = UINT_MAX; /* Discard outliers above this value */ again: - /* first calculate average and standard deviation of the past */ - max = avg = divisor = stddev = 0; + /* First calculate the average of past intervals */ + max = 0; + avg = 0; + divisor = 0; for (i = 0; i < INTERVALS; i++) { - int64_t value = data->intervals[i]; + unsigned int value = data->intervals[i]; if (value <= thresh) { avg += value; divisor++; @@ -218,15 +230,38 @@ again: } do_div(avg, divisor); + /* Then try to determine standard deviation */ + stddev = 0; for (i = 0; i < INTERVALS; i++) { - int64_t value = data->intervals[i]; + unsigned int value = data->intervals[i]; if (value <= thresh) { int64_t diff = value - avg; stddev += diff * diff; } } do_div(stddev, divisor); - stddev = int_sqrt(stddev); + /* + * The typical interval is obtained when standard deviation is small + * or standard deviation is small compared to the average interval. + * + * int_sqrt() formal parameter type is unsigned long. When the + * greatest difference to an outlier exceeds ~65 ms * sqrt(divisor) + * the resulting squared standard deviation exceeds the input domain + * of int_sqrt on platforms where unsigned long is 32 bits in size. + * In such case reject the candidate average. + * + * Use this result only if there is no timer to wake us up sooner. + */ + if (likely(stddev <= ULONG_MAX)) { + stddev = int_sqrt(stddev); + if (((avg > stddev * 6) && (divisor * 4 >= INTERVALS * 3)) + || stddev <= 20) { + if (data->next_timer_us > avg) + data->predicted_us = avg; + return; + } + } + /* * If we have outliers to the upside in our distribution, discard * those by setting the threshold to exclude these outliers, then @@ -235,20 +270,12 @@ again: * * This can deal with workloads that have long pauses interspersed * with sporadic activity with a bunch of short pauses. - * - * The typical interval is obtained when standard deviation is small - * or standard deviation is small compared to the average interval. */ - if (((avg > stddev * 6) && (divisor * 4 >= INTERVALS * 3)) - || stddev <= 20) { - data->predicted_us = avg; + if ((divisor * 4) <= INTERVALS * 3) return; - } else if ((divisor * 4) > INTERVALS * 3) { - /* Exclude the max interval */ - thresh = max - 1; - goto again; - } + thresh = max - 1; + goto again; } /** @@ -261,7 +288,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) struct menu_device *data = &__get_cpu_var(menu_devices); int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY); int i; - int multiplier; + unsigned int interactivity_req; struct timespec t; if (data->needs_update) { @@ -269,8 +296,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) data->needs_update = 0; } - data->last_state_idx = 0; - data->exit_us = 0; + data->last_state_idx = CPUIDLE_DRIVER_STATE_START - 1; /* Special case when user has set very strict latency requirement */ if (unlikely(latency_req == 0)) @@ -278,32 +304,37 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) /* determine the expected residency time, round up */ t = ktime_to_timespec(tick_nohz_get_sleep_length()); - data->expected_us = + data->next_timer_us = t.tv_sec * USEC_PER_SEC + t.tv_nsec / NSEC_PER_USEC; - data->bucket = which_bucket(data->expected_us); - - multiplier = performance_multiplier(); + data->bucket = which_bucket(data->next_timer_us); /* - * if the correction factor is 0 (eg first time init or cpu hotplug - * etc), we actually want to start out with a unity factor. + * Force the result of multiplication to be 64 bits even if both + * operands are 32 bits. + * Make sure to round up for half microseconds. */ - if (data->correction_factor[data->bucket] == 0) - data->correction_factor[data->bucket] = RESOLUTION * DECAY; - - /* Make sure to round up for half microseconds */ - data->predicted_us = div_round64(data->expected_us * data->correction_factor[data->bucket], + data->predicted_us = div_round64((uint64_t)data->next_timer_us * + data->correction_factor[data->bucket], RESOLUTION * DECAY); get_typical_interval(data); /* + * Performance multiplier defines a minimum predicted idle + * duration / latency ratio. Adjust the latency limit if + * necessary. + */ + interactivity_req = data->predicted_us / performance_multiplier(); + if (latency_req > interactivity_req) + latency_req = interactivity_req; + + /* * We want to default to C1 (hlt), not to busy polling * unless the timer is happening really really soon. */ - if (data->expected_us > 5 && + if (data->next_timer_us > 5 && !drv->states[CPUIDLE_DRIVER_STATE_START].disabled && dev->states_usage[CPUIDLE_DRIVER_STATE_START].disable == 0) data->last_state_idx = CPUIDLE_DRIVER_STATE_START; @@ -322,11 +353,8 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) continue; if (s->exit_latency > latency_req) continue; - if (s->exit_latency * multiplier > data->predicted_us) - continue; data->last_state_idx = i; - data->exit_us = s->exit_latency; } return data->last_state_idx; @@ -357,37 +385,47 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev) { struct menu_device *data = &__get_cpu_var(menu_devices); int last_idx = data->last_state_idx; - unsigned int last_idle_us = cpuidle_get_last_residency(dev); struct cpuidle_state *target = &drv->states[last_idx]; unsigned int measured_us; - u64 new_factor; + unsigned int new_factor; /* - * Ugh, this idle state doesn't support residency measurements, so we - * are basically lost in the dark. As a compromise, assume we slept - * for the whole expected time. + * Try to figure out how much time passed between entry to low + * power state and occurrence of the wakeup event. + * + * If the entered idle state didn't support residency measurements, + * we are basically lost in the dark how much time passed. + * As a compromise, assume we slept for the whole expected time. + * + * Any measured amount of time will include the exit latency. + * Since we are interested in when the wakeup begun, not when it + * was completed, we must substract the exit latency. However, if + * the measured amount of time is less than the exit latency, + * assume the state was never reached and the exit latency is 0. */ - if (unlikely(!(target->flags & CPUIDLE_FLAG_TIME_VALID))) - last_idle_us = data->expected_us; + if (unlikely(!(target->flags & CPUIDLE_FLAG_TIME_VALID))) { + /* Use timer value as is */ + measured_us = data->next_timer_us; + } else { + /* Use measured value */ + measured_us = cpuidle_get_last_residency(dev); - measured_us = last_idle_us; + /* Deduct exit latency */ + if (measured_us > target->exit_latency) + measured_us -= target->exit_latency; - /* - * We correct for the exit latency; we are assuming here that the - * exit latency happens after the event that we're interested in. - */ - if (measured_us > data->exit_us) - measured_us -= data->exit_us; - - - /* update our correction ratio */ + /* Make sure our coefficients do not exceed unity */ + if (measured_us > data->next_timer_us) + measured_us = data->next_timer_us; + } - new_factor = data->correction_factor[data->bucket] - * (DECAY - 1) / DECAY; + /* Update our correction ratio */ + new_factor = data->correction_factor[data->bucket]; + new_factor -= new_factor / DECAY; - if (data->expected_us > 0 && measured_us < MAX_INTERESTING) - new_factor += RESOLUTION * measured_us / data->expected_us; + if (data->next_timer_us > 0 && measured_us < MAX_INTERESTING) + new_factor += RESOLUTION * measured_us / data->next_timer_us; else /* * we were idle so long that we count it as a perfect @@ -397,15 +435,17 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev) /* * We don't want 0 as factor; we always want at least - * a tiny bit of estimated time. + * a tiny bit of estimated time. Fortunately, due to rounding, + * new_factor will stay nonzero regardless of measured_us values + * and the compiler can eliminate this test as long as DECAY > 1. */ - if (new_factor == 0) + if (DECAY == 1 && unlikely(new_factor == 0)) new_factor = 1; data->correction_factor[data->bucket] = new_factor; /* update the repeating-pattern data */ - data->intervals[data->interval_ptr++] = last_idle_us; + data->intervals[data->interval_ptr++] = measured_us; if (data->interval_ptr >= INTERVALS) data->interval_ptr = 0; } @@ -419,9 +459,17 @@ static int menu_enable_device(struct cpuidle_driver *drv, struct cpuidle_device *dev) { struct menu_device *data = &per_cpu(menu_devices, dev->cpu); + int i; memset(data, 0, sizeof(struct menu_device)); + /* + * if the correction factor is 0 (eg first time init or cpu hotplug + * etc), we actually want to start out with a unity factor. + */ + for(i = 0; i < BUCKETS; i++) + data->correction_factor[i] = RESOLUTION * DECAY; + return 0; } @@ -442,14 +490,4 @@ static int __init init_menu(void) return cpuidle_register_governor(&menu_governor); } -/** - * exit_menu - exits the governor - */ -static void __exit exit_menu(void) -{ - cpuidle_unregister_governor(&menu_governor); -} - -MODULE_LICENSE("GPL"); -module_init(init_menu); -module_exit(exit_menu); +postcore_initcall(init_menu); |