1 // SPDX-License-Identifier: GPL-2.0-only
3  * menu.c - the menu idle governor
5  * Copyright (C) 2006-2007 Adam Belay <abelay@novell.com>
40  * -----------------------
43  * provides us this duration in the "target_residency" field. So all that we
68  * Repeatable-interval-detector
69  * ----------------------------
79  * ---------------------------
88  * This rule-of-thumb is implemented using a performance-multiplier:
122 	 * This allows us to calculate  in which_bucket()
167 	unsigned int min, max, thresh, avg;  in get_typical_interval()  local
175 	min = UINT_MAX;  in get_typical_interval()
180 		unsigned int value = data->intervals[i];  in get_typical_interval()
187 			if (value < min)  in get_typical_interval()
188 				min = value;  in get_typical_interval()
203 		unsigned int value = data->intervals[i];  in get_typical_interval()
205 			int64_t diff = (int64_t)value - avg;  in get_typical_interval()
216 	 * small (stddev <= 20 us, variance <= 400 us^2) or standard  in get_typical_interval()
224 	 * Use this result only if there is no timer to wake us up sooner.  in get_typical_interval()
245 	thresh = max - 1;  in get_typical_interval()
250  * menu_select - selects the next idle state to enter
259 	s64 latency_req = cpuidle_governor_latency_req(dev->cpu);  in menu_select()
266 	if (data->needs_update) {  in menu_select()
268 		data->needs_update = 0;  in menu_select()
271 	nr_iowaiters = nr_iowait_cpu(dev->cpu);  in menu_select()
285 		data->next_timer_ns = delta;  in menu_select()
286 		data->bucket = which_bucket(data->next_timer_ns, nr_iowaiters);  in menu_select()
290 					data->next_timer_ns *  in menu_select()
291 						data->correction_factor[data->bucket],  in menu_select()
294 		predicted_ns = min((u64)timer_us * NSEC_PER_USEC, predicted_ns);  in menu_select()
302 		data->next_timer_ns = KTIME_MAX;  in menu_select()
304 		data->bucket = which_bucket(KTIME_MAX, nr_iowaiters);  in menu_select()
307 	if (unlikely(drv->state_count <= 1 || latency_req == 0) ||  in menu_select()
308 	    ((data->next_timer_ns < drv->states[1].target_residency_ns ||  in menu_select()
309 	      latency_req < drv->states[1].exit_latency_ns) &&  in menu_select()
310 	     !dev->states_usage[0].disable)) {  in menu_select()
316 		*stop_tick = !(drv->states[0].flags & CPUIDLE_FLAG_POLLING);  in menu_select()
330 			predicted_ns = data->next_timer_ns;  in menu_select()
333 		 * Use the performance multiplier and the user-configurable  in menu_select()
346 	idx = -1;  in menu_select()
347 	for (i = 0; i < drv->state_count; i++) {  in menu_select()
348 		struct cpuidle_state *s = &drv->states[i];  in menu_select()
350 		if (dev->states_usage[i].disable)  in menu_select()
353 		if (idx == -1)  in menu_select()
356 		if (s->target_residency_ns > predicted_ns) {  in menu_select()
361 			if ((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) &&  in menu_select()
362 			    s->exit_latency_ns <= latency_req &&  in menu_select()
363 			    s->target_residency_ns <= data->next_timer_ns) {  in menu_select()
364 				predicted_ns = s->target_residency_ns;  in menu_select()
378 				predicted_ns = drv->states[idx].target_residency_ns;  in menu_select()
384 			 * state's target residency matches the time till the  in menu_select()
388 			if (drv->states[idx].target_residency_ns < TICK_NSEC &&  in menu_select()
389 			    s->target_residency_ns <= delta_tick)  in menu_select()
394 		if (s->exit_latency_ns > latency_req)  in menu_select()
400 	if (idx == -1)  in menu_select()
407 	if (((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) ||  in menu_select()
411 		if (idx > 0 && drv->states[idx].target_residency_ns > delta_tick) {  in menu_select()
414 			 * residency of the state to be returned is not within  in menu_select()
418 			for (i = idx - 1; i >= 0; i--) {  in menu_select()
419 				if (dev->states_usage[i].disable)  in menu_select()
423 				if (drv->states[i].target_residency_ns <= delta_tick)  in menu_select()
433  * menu_reflect - records that data structures need update
444 	dev->last_state_idx = index;  in menu_reflect()
445 	data->needs_update = 1;  in menu_reflect()
446 	data->tick_wakeup = tick_nohz_idle_got_tick();  in menu_reflect()
450  * menu_update - attempts to guess what happened after entry
457 	int last_idx = dev->last_state_idx;  in menu_update()
458 	struct cpuidle_state *target = &drv->states[last_idx];  in menu_update()
466 	 * If the entered idle state didn't support residency measurements,  in menu_update()
477 	if (data->tick_wakeup && data->next_timer_ns > TICK_NSEC) {  in menu_update()
488 	} else if ((drv->states[last_idx].flags & CPUIDLE_FLAG_POLLING) &&  in menu_update()
489 		   dev->poll_time_limit) {  in menu_update()
497 		measured_ns = data->next_timer_ns;  in menu_update()
500 		measured_ns = dev->last_residency_ns;  in menu_update()
503 		if (measured_ns > 2 * target->exit_latency_ns)  in menu_update()
504 			measured_ns -= target->exit_latency_ns;  in menu_update()
510 	if (measured_ns > data->next_timer_ns)  in menu_update()
511 		measured_ns = data->next_timer_ns;  in menu_update()
514 	new_factor = data->correction_factor[data->bucket];  in menu_update()
515 	new_factor -= new_factor / DECAY;  in menu_update()
517 	if (data->next_timer_ns > 0 && measured_ns < MAX_INTERESTING)  in menu_update()
519 					data->next_timer_ns);  in menu_update()
536 	data->correction_factor[data->bucket] = new_factor;  in menu_update()
538 	/* update the repeating-pattern data */  in menu_update()
539 	data->intervals[data->interval_ptr++] = ktime_to_us(measured_ns);  in menu_update()
540 	if (data->interval_ptr >= INTERVALS)  in menu_update()
541 		data->interval_ptr = 0;  in menu_update()
545  * menu_enable_device - scans a CPU's states and does setup
552 	struct menu_device *data = &per_cpu(menu_devices, dev->cpu);  in menu_enable_device()
562 		data->correction_factor[i] = RESOLUTION * DECAY;  in menu_enable_device()
576  * init_menu - initializes the governor