// SPDX-License-Identifier: GPL-2.0/* * Per Entity Load Tracking (PELT) * *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> * *  Interactivity improvements by Mike Galbraith *  (C) 2007 Mike Galbraith <efault@gmx.de> * *  Various enhancements by Dmitry Adamushko. *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com> * *  Group scheduling enhancements by Srivatsa Vaddagiri *  Copyright IBM Corporation, 2007 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> * *  Scaled math optimizations by Thomas Gleixner *  Copyright (C) 2007, Linutronix GmbH, Thomas Gleixner <tglx@kernel.org> * *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra * *  Move PELT related code from fair.c into this pelt.c file *  Author: Vincent Guittot <vincent.guittot@linaro.org> */#include "pelt.h" /* * Approximate: *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period) */static u64 decay_load(u64 val, u64 n){	unsigned int local_n; 	if (unlikely(n > LOAD_AVG_PERIOD * 63))		return 0; 	/* after bounds checking we can collapse to 32-bit */	local_n = n; 	/*	 * As y^PERIOD = 1/2, we can combine	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)	 * With a look-up table which covers y^n (n<PERIOD)	 *	 * To achieve constant time decay_load.	 */	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {		val >>= local_n / LOAD_AVG_PERIOD;		local_n %= LOAD_AVG_PERIOD;	} 	val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);	return val;} static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3){	u32 c1, c2, c3 = d3; /* y^0 == 1 */ 	/*	 * c1 = d1 y^p	 */	c1 = decay_load((u64)d1, periods); 	/*	 *            p-1	 * c2 = 1024 \Sum y^n	 *            n=1	 *	 *              inf        inf	 *    = 1024 ( \Sum y^n - \Sum y^n - y^0 )	 *              n=0        n=p	 */	c2 = LOAD_AVG_MAX - decay_load(LOAD_AVG_MAX, periods) - 1024; 	return c1 + c2 + c3;} /* * Accumulate the three separate parts of the sum; d1 the remainder * of the last (incomplete) period, d2 the span of full periods and d3 * the remainder of the (incomplete) current period. * *           d1          d2           d3 *           ^           ^            ^ *           |           |            | *         |<->|<----------------->|<--->| * ... |---x---|------| ... |------|-----x (now) * *                           p-1 * u' = (u + d1) y^p + 1024 \Sum y^n + d3 y^0 *                           n=1 * *    = u y^p +					(Step 1) * *                     p-1 *      d1 y^p + 1024 \Sum y^n + d3 y^0		(Step 2) *                     n=1 */static __always_inline u32accumulate_sum(u64 delta, struct sched_avg *sa,	       unsigned long load, unsigned long runnable, int running){	u32 contrib = (u32)delta; /* p == 0 -> delta < 1024 */	u64 periods; 	delta += sa->period_contrib;	periods = delta / 1024; /* A period is 1024us (~1ms) */ 	/*	 * Step 1: decay old *_sum if we crossed period boundaries.	 */	if (periods) {		sa->load_sum = decay_load(sa->load_sum, periods);		sa->runnable_sum =			decay_load(sa->runnable_sum, periods);		sa->util_sum = decay_load((u64)(sa->util_sum), periods); 		/*		 * Step 2		 */		delta %= 1024;		if (load) {			/*			 * This relies on the:			 *			 * if (!load)			 *	runnable = running = 0;			 *			 * clause from ___update_load_sum(); this results in			 * the below usage of @contrib to disappear entirely,			 * so no point in calculating it.			 */			contrib = __accumulate_pelt_segments(periods,					1024 - sa->period_contrib, delta);		}	}	sa->period_contrib = delta; 	if (load)		sa->load_sum += load * contrib;	if (runnable)		sa->runnable_sum += runnable * contrib << SCHED_CAPACITY_SHIFT;	if (running)		sa->util_sum += contrib << SCHED_CAPACITY_SHIFT; 	return periods;} /* * We can represent the historical contribution to runnable average as the * coefficients of a geometric series.  To do this we sub-divide our runnable * history into segments of approximately 1ms (1024us); label the segment that * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g. * * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ... *      p0            p1           p2 *     (now)       (~1ms ago)  (~2ms ago) * * Let u_i denote the fraction of p_i that the entity was runnable. * * We then designate the fractions u_i as our co-efficients, yielding the * following representation of historical load: *   u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ... * * We choose y based on the with of a reasonably scheduling period, fixing: *   y^32 = 0.5 * * This means that the contribution to load ~32ms ago (u_32) will be weighted * approximately half as much as the contribution to load within the last ms * (u_0). * * When a period "rolls over" and we have new u_0`, multiplying the previous * sum again by y is sufficient to update: *   load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... ) *            = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}] */static __always_inline int___update_load_sum(u64 now, struct sched_avg *sa,		  unsigned long load, unsigned long runnable, int running){	u64 delta; 	delta = now - sa->last_update_time;	/*	 * This should only happen when time goes backwards, which it	 * unfortunately does during sched clock init when we swap over to TSC.	 */	if ((s64)delta < 0) {		sa->last_update_time = now;		return 0;	} 	/*	 * Use 1024ns as the unit of measurement since it's a reasonable	 * approximation of 1us and fast to compute.	 */	delta >>= 10;	if (!delta)		return 0; 	sa->last_update_time += delta << 10; 	/*	 * running is a subset of runnable (weight) so running can't be set if	 * runnable is clear. But there are some corner cases where the current	 * se has been already dequeued but cfs_rq->h_curr still points to it.	 * This means that weight will be 0 but not running for a sched_entity	 * but also for a cfs_rq if the latter becomes idle. As an example,	 * this happens during sched_balance_newidle() which calls	 * sched_balance_update_blocked_averages().	 *	 * Also see the comment in accumulate_sum().	 */	if (!load)		runnable = running = 0; 	/*	 * Now we know we crossed measurement unit boundaries. The *_avg	 * accrues by two steps:	 *	 * Step 1: accumulate *_sum since last_update_time. If we haven't	 * crossed period boundaries, finish.	 */	if (!accumulate_sum(delta, sa, load, runnable, running))		return 0; 	return 1;} /* * When syncing *_avg with *_sum, we must take into account the current * position in the PELT segment otherwise the remaining part of the segment * will be considered as idle time whereas it's not yet elapsed and this will * generate unwanted oscillation in the range [1002..1024[. * * The max value of *_sum varies with the position in the time segment and is * equals to : * *   LOAD_AVG_MAX*y + sa->period_contrib * * which can be simplified into: * *   LOAD_AVG_MAX - 1024 + sa->period_contrib * * because LOAD_AVG_MAX*y == LOAD_AVG_MAX-1024 * * The same care must be taken when a sched entity is added, updated or * removed from a cfs_rq and we need to update sched_avg. Scheduler entities * and the cfs rq, to which they are attached, have the same position in the * time segment because they use the same clock. This means that we can use * the period_contrib of cfs_rq when updating the sched_avg of a sched_entity * if it's more convenient. */static __always_inline void___update_load_avg(struct sched_avg *sa, unsigned long load){	u32 divider = get_pelt_divider(sa); 	/*	 * Step 2: update *_avg.	 */	sa->load_avg = div_u64(load * sa->load_sum, divider);	sa->runnable_avg = div_u64(sa->runnable_sum, divider);	WRITE_ONCE(sa->util_avg, sa->util_sum / divider);} /* * sched_entity: * *   task: *     se_weight()   = se->load.weight *     se_runnable() = !!on_rq * *   group: [ see update_cfs_group() ] *     se_weight()   = tg->weight * grq->load_avg / tg->load_avg *     se_runnable() = grq->h_nr_runnable * *   runnable_sum = se_runnable() * runnable = grq->runnable_sum *   runnable_avg = runnable_sum * *   load_sum := runnable *   load_avg = se_weight(se) * load_sum * * cfq_rq: * *   runnable_sum = \Sum se->avg.runnable_sum *   runnable_avg = \Sum se->avg.runnable_avg * *   load_sum = \Sum se_weight(se) * se->avg.load_sum *   load_avg = \Sum se->avg.load_avg */ int __update_load_avg_blocked_se(u64 now, struct sched_entity *se){	if (___update_load_sum(now, &se->avg, 0, 0, 0)) {		___update_load_avg(&se->avg, se_weight(se));		trace_pelt_se_tp(se);		return 1;	} 	return 0;} int __update_load_avg_se(u64 now, struct cfs_rq *cfs_rq, struct sched_entity *se){	if (___update_load_sum(now, &se->avg, !!se->on_rq, se_runnable(se),				cfs_rq->h_curr == se)) { 		___update_load_avg(&se->avg, se_weight(se));		cfs_se_util_change(&se->avg);		trace_pelt_se_tp(se);		return 1;	} 	return 0;} int __update_load_avg_cfs_rq(u64 now, struct cfs_rq *cfs_rq){	if (___update_load_sum(now, &cfs_rq->avg,				scale_load_down(cfs_rq->load.weight),				cfs_rq->h_nr_runnable,				cfs_rq->h_curr != NULL)) { 		___update_load_avg(&cfs_rq->avg, 1);		trace_pelt_cfs_tp(cfs_rq);		return 1;	} 	return 0;} /* * rt_rq: * *   util_sum = \Sum se->avg.util_sum but se->avg.util_sum is not tracked *   util_sum = cpu_scale * load_sum *   runnable_sum = util_sum * *   load_avg and runnable_avg are not supported and meaningless. * */ int update_rt_rq_load_avg(u64 now, struct rq *rq, int running){	if (___update_load_sum(now, &rq->avg_rt,				running,				running,				running)) { 		___update_load_avg(&rq->avg_rt, 1);		trace_pelt_rt_tp(rq);		return 1;	} 	return 0;} /* * dl_rq: * *   util_sum = \Sum se->avg.util_sum but se->avg.util_sum is not tracked *   util_sum = cpu_scale * load_sum *   runnable_sum = util_sum * *   load_avg and runnable_avg are not supported and meaningless. * */ int update_dl_rq_load_avg(u64 now, struct rq *rq, int running){	if (___update_load_sum(now, &rq->avg_dl,				running,				running,				running)) { 		___update_load_avg(&rq->avg_dl, 1);		trace_pelt_dl_tp(rq);		return 1;	} 	return 0;} #ifdef CONFIG_SCHED_HW_PRESSURE/* * hardware: * *   load_sum = \Sum se->avg.load_sum but se->avg.load_sum is not tracked * *   util_avg and runnable_load_avg are not supported and meaningless. * * Unlike rt/dl utilization tracking that track time spent by a cpu * running a rt/dl task through util_avg, the average HW pressure is * tracked through load_avg. This is because HW pressure signal is * time weighted "delta" capacity unlike util_avg which is binary. * "delta capacity" =  actual capacity  - *			capped capacity a cpu due to a HW event. */ int update_hw_load_avg(u64 now, struct rq *rq, u64 capacity){	if (___update_load_sum(now, &rq->avg_hw,			       capacity,			       capacity,			       capacity)) {		___update_load_avg(&rq->avg_hw, 1);		trace_pelt_hw_tp(rq);		return 1;	} 	return 0;}#endif /* CONFIG_SCHED_HW_PRESSURE */ #ifdef CONFIG_HAVE_SCHED_AVG_IRQ/* * IRQ: * *   util_sum = \Sum se->avg.util_sum but se->avg.util_sum is not tracked *   util_sum = cpu_scale * load_sum *   runnable_sum = util_sum * *   load_avg and runnable_avg are not supported and meaningless. * */ int update_irq_load_avg(struct rq *rq, u64 running){	int ret = 0; 	/*	 * We can't use clock_pelt because IRQ time is not accounted in	 * clock_task. Instead we directly scale the running time to	 * reflect the real amount of computation	 */	running = cap_scale(running, arch_scale_freq_capacity(cpu_of(rq)));	running = cap_scale(running, arch_scale_cpu_capacity(cpu_of(rq))); 	/*	 * We know the time that has been used by interrupt since last update	 * but we don't when. Let be pessimistic and assume that interrupt has	 * happened just before the update. This is not so far from reality	 * because interrupt will most probably wake up task and trig an update	 * of rq clock during which the metric is updated.	 * We start to decay with normal context time and then we add the	 * interrupt context time.	 * We can safely remove running from rq->clock because	 * rq->clock += delta with delta >= running	 */	ret = ___update_load_sum(rq->clock - running, &rq->avg_irq,				0,				0,				0);	ret += ___update_load_sum(rq->clock, &rq->avg_irq,				1,				1,				1); 	if (ret) {		___update_load_avg(&rq->avg_irq, 1);		trace_pelt_irq_tp(rq);	} 	return ret;}#endif /* CONFIG_HAVE_SCHED_AVG_IRQ */ /* * Load avg and utiliztion metrics need to be updated periodically and before * consumption. This function updates the metrics for all subsystems except for * the fair class. @rq must be locked and have its clock updated. */bool update_other_load_avgs(struct rq *rq){	u64 now = rq_clock_pelt(rq);	const struct sched_class *curr_class = rq->donor->sched_class;	unsigned long hw_pressure = arch_scale_hw_pressure(cpu_of(rq)); 	lockdep_assert_rq_held(rq); 	/* hw_pressure doesn't care about invariance */	return update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |		update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |		update_hw_load_avg(rq_clock_task(rq), rq, hw_pressure) |		update_irq_load_avg(rq, 0);}