diff options
Diffstat (limited to 'drivers/cpuidle')
| -rw-r--r-- | drivers/cpuidle/governors/menu.c | 76 |
1 files changed, 9 insertions, 67 deletions
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index f3c9d49f0f2a..28363bfa3e4c 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -19,7 +19,7 @@ #include "gov.h" -#define BUCKETS 12 +#define BUCKETS 6 #define INTERVAL_SHIFT 3 #define INTERVALS (1UL << INTERVAL_SHIFT) #define RESOLUTION 1024 @@ -29,12 +29,11 @@ /* * Concepts and ideas behind the menu governor * - * For the menu governor, there are 3 decision factors for picking a C + * For the menu governor, there are 2 decision factors for picking a C * state: * 1) Energy break even point - * 2) Performance impact - * 3) Latency tolerance (from pmqos infrastructure) - * These three factors are treated independently. + * 2) Latency tolerance (from pmqos infrastructure) + * These two factors are treated independently. * * Energy break even point * ----------------------- @@ -75,30 +74,6 @@ * intervals and if the stand deviation of these 8 intervals is below a * threshold value, we use the average of these intervals as prediction. * - * Limiting Performance Impact - * --------------------------- - * C states, especially those with large exit latencies, can have a real - * noticeable impact on workloads, which is not acceptable for most sysadmins, - * and in addition, less performance has a power price of its own. - * - * As a general rule of thumb, menu assumes that the following heuristic - * holds: - * The busier the system, the less impact of C states is acceptable - * - * This rule-of-thumb is implemented using a performance-multiplier: - * If the exit latency times the performance multiplier is longer than - * the predicted duration, the C state is not considered a candidate - * for selection due to a too high performance impact. So the higher - * this multiplier is, the longer we need to be idle to pick a deep C - * state, and thus the less likely a busy CPU will hit such a deep - * C state. - * - * Currently there is only one value determining the factor: - * 10 points are added for each process that is waiting for IO on this CPU. - * (This value was experimentally determined.) - * Utilization is no longer a factor as it was shown that it never contributed - * significantly to the performance multiplier in the first place. - * */ struct menu_device { @@ -112,19 +87,10 @@ struct menu_device { int interval_ptr; }; -static inline int which_bucket(u64 duration_ns, unsigned int nr_iowaiters) +static inline int which_bucket(u64 duration_ns) { int bucket = 0; - /* - * We keep two groups of stats; one with no - * IO pending, one without. - * This allows us to calculate - * E(duration)|iowait - */ - if (nr_iowaiters) - bucket = BUCKETS/2; - if (duration_ns < 10ULL * NSEC_PER_USEC) return bucket; if (duration_ns < 100ULL * NSEC_PER_USEC) @@ -138,19 +104,6 @@ static inline int which_bucket(u64 duration_ns, unsigned int nr_iowaiters) return bucket + 5; } -/* - * Return a multiplier for the exit latency that is intended - * to take performance requirements into account. - * The more performance critical we estimate the system - * to be, the higher this multiplier, and thus the higher - * the barrier to go to an expensive C state. - */ -static inline int performance_multiplier(unsigned int nr_iowaiters) -{ - /* for IO wait tasks (per cpu!) we add 10x each */ - return 1 + 10 * nr_iowaiters; -} - static DEFINE_PER_CPU(struct menu_device, menu_devices); static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev); @@ -258,8 +211,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, struct menu_device *data = this_cpu_ptr(&menu_devices); s64 latency_req = cpuidle_governor_latency_req(dev->cpu); u64 predicted_ns; - u64 interactivity_req; - unsigned int nr_iowaiters; ktime_t delta, delta_tick; int i, idx; @@ -268,8 +219,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, data->needs_update = 0; } - nr_iowaiters = nr_iowait_cpu(dev->cpu); - /* Find the shortest expected idle interval. */ predicted_ns = get_typical_interval(data) * NSEC_PER_USEC; if (predicted_ns > RESIDENCY_THRESHOLD_NS) { @@ -283,7 +232,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, } data->next_timer_ns = delta; - data->bucket = which_bucket(data->next_timer_ns, nr_iowaiters); + data->bucket = which_bucket(data->next_timer_ns); /* Round up the result for half microseconds. */ timer_us = div_u64((RESOLUTION * DECAY * NSEC_PER_USEC) / 2 + @@ -301,7 +250,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, */ data->next_timer_ns = KTIME_MAX; delta_tick = TICK_NSEC / 2; - data->bucket = which_bucket(KTIME_MAX, nr_iowaiters); + data->bucket = which_bucket(KTIME_MAX); } if (unlikely(drv->state_count <= 1 || latency_req == 0) || @@ -328,15 +277,8 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, */ if (predicted_ns < TICK_NSEC) predicted_ns = data->next_timer_ns; - } else { - /* - * Use the performance multiplier and the user-configurable - * latency_req to determine the maximum exit latency. - */ - interactivity_req = div64_u64(predicted_ns, - performance_multiplier(nr_iowaiters)); - if (latency_req > interactivity_req) - latency_req = interactivity_req; + } else if (latency_req > predicted_ns) { + latency_req = predicted_ns; } /* |