drm/panfrost: Remove set but not used variable 'bo'
[linux/fpc-iii.git] / kernel / sched / pelt.c
blobbd006b79b3608b9d5d371996dfe523b7f5bbfacd
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Per Entity Load Tracking
5 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
7 * Interactivity improvements by Mike Galbraith
8 * (C) 2007 Mike Galbraith <efault@gmx.de>
10 * Various enhancements by Dmitry Adamushko.
11 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
13 * Group scheduling enhancements by Srivatsa Vaddagiri
14 * Copyright IBM Corporation, 2007
15 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
17 * Scaled math optimizations by Thomas Gleixner
18 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
20 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra
21 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
23 * Move PELT related code from fair.c into this pelt.c file
24 * Author: Vincent Guittot <vincent.guittot@linaro.org>
27 #include <linux/sched.h>
28 #include "sched.h"
29 #include "pelt.h"
31 #include <trace/events/sched.h>
34 * Approximate:
35 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
37 static u64 decay_load(u64 val, u64 n)
39 unsigned int local_n;
41 if (unlikely(n > LOAD_AVG_PERIOD * 63))
42 return 0;
44 /* after bounds checking we can collapse to 32-bit */
45 local_n = n;
48 * As y^PERIOD = 1/2, we can combine
49 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
50 * With a look-up table which covers y^n (n<PERIOD)
52 * To achieve constant time decay_load.
54 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
55 val >>= local_n / LOAD_AVG_PERIOD;
56 local_n %= LOAD_AVG_PERIOD;
59 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
60 return val;
63 static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3)
65 u32 c1, c2, c3 = d3; /* y^0 == 1 */
68 * c1 = d1 y^p
70 c1 = decay_load((u64)d1, periods);
73 * p-1
74 * c2 = 1024 \Sum y^n
75 * n=1
77 * inf inf
78 * = 1024 ( \Sum y^n - \Sum y^n - y^0 )
79 * n=0 n=p
81 c2 = LOAD_AVG_MAX - decay_load(LOAD_AVG_MAX, periods) - 1024;
83 return c1 + c2 + c3;
86 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
89 * Accumulate the three separate parts of the sum; d1 the remainder
90 * of the last (incomplete) period, d2 the span of full periods and d3
91 * the remainder of the (incomplete) current period.
93 * d1 d2 d3
94 * ^ ^ ^
95 * | | |
96 * |<->|<----------------->|<--->|
97 * ... |---x---|------| ... |------|-----x (now)
99 * p-1
100 * u' = (u + d1) y^p + 1024 \Sum y^n + d3 y^0
101 * n=1
103 * = u y^p + (Step 1)
105 * p-1
106 * d1 y^p + 1024 \Sum y^n + d3 y^0 (Step 2)
107 * n=1
109 static __always_inline u32
110 accumulate_sum(u64 delta, struct sched_avg *sa,
111 unsigned long load, unsigned long runnable, int running)
113 u32 contrib = (u32)delta; /* p == 0 -> delta < 1024 */
114 u64 periods;
116 delta += sa->period_contrib;
117 periods = delta / 1024; /* A period is 1024us (~1ms) */
120 * Step 1: decay old *_sum if we crossed period boundaries.
122 if (periods) {
123 sa->load_sum = decay_load(sa->load_sum, periods);
124 sa->runnable_load_sum =
125 decay_load(sa->runnable_load_sum, periods);
126 sa->util_sum = decay_load((u64)(sa->util_sum), periods);
129 * Step 2
131 delta %= 1024;
132 if (load) {
134 * This relies on the:
136 * if (!load)
137 * runnable = running = 0;
139 * clause from ___update_load_sum(); this results in
140 * the below usage of @contrib to dissapear entirely,
141 * so no point in calculating it.
143 contrib = __accumulate_pelt_segments(periods,
144 1024 - sa->period_contrib, delta);
147 sa->period_contrib = delta;
149 if (load)
150 sa->load_sum += load * contrib;
151 if (runnable)
152 sa->runnable_load_sum += runnable * contrib;
153 if (running)
154 sa->util_sum += contrib << SCHED_CAPACITY_SHIFT;
156 return periods;
160 * We can represent the historical contribution to runnable average as the
161 * coefficients of a geometric series. To do this we sub-divide our runnable
162 * history into segments of approximately 1ms (1024us); label the segment that
163 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
165 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
166 * p0 p1 p2
167 * (now) (~1ms ago) (~2ms ago)
169 * Let u_i denote the fraction of p_i that the entity was runnable.
171 * We then designate the fractions u_i as our co-efficients, yielding the
172 * following representation of historical load:
173 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
175 * We choose y based on the with of a reasonably scheduling period, fixing:
176 * y^32 = 0.5
178 * This means that the contribution to load ~32ms ago (u_32) will be weighted
179 * approximately half as much as the contribution to load within the last ms
180 * (u_0).
182 * When a period "rolls over" and we have new u_0`, multiplying the previous
183 * sum again by y is sufficient to update:
184 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
185 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
187 static __always_inline int
188 ___update_load_sum(u64 now, struct sched_avg *sa,
189 unsigned long load, unsigned long runnable, int running)
191 u64 delta;
193 delta = now - sa->last_update_time;
195 * This should only happen when time goes backwards, which it
196 * unfortunately does during sched clock init when we swap over to TSC.
198 if ((s64)delta < 0) {
199 sa->last_update_time = now;
200 return 0;
204 * Use 1024ns as the unit of measurement since it's a reasonable
205 * approximation of 1us and fast to compute.
207 delta >>= 10;
208 if (!delta)
209 return 0;
211 sa->last_update_time += delta << 10;
214 * running is a subset of runnable (weight) so running can't be set if
215 * runnable is clear. But there are some corner cases where the current
216 * se has been already dequeued but cfs_rq->curr still points to it.
217 * This means that weight will be 0 but not running for a sched_entity
218 * but also for a cfs_rq if the latter becomes idle. As an example,
219 * this happens during idle_balance() which calls
220 * update_blocked_averages().
222 * Also see the comment in accumulate_sum().
224 if (!load)
225 runnable = running = 0;
228 * Now we know we crossed measurement unit boundaries. The *_avg
229 * accrues by two steps:
231 * Step 1: accumulate *_sum since last_update_time. If we haven't
232 * crossed period boundaries, finish.
234 if (!accumulate_sum(delta, sa, load, runnable, running))
235 return 0;
237 return 1;
240 static __always_inline void
241 ___update_load_avg(struct sched_avg *sa, unsigned long load, unsigned long runnable)
243 u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
246 * Step 2: update *_avg.
248 sa->load_avg = div_u64(load * sa->load_sum, divider);
249 sa->runnable_load_avg = div_u64(runnable * sa->runnable_load_sum, divider);
250 WRITE_ONCE(sa->util_avg, sa->util_sum / divider);
254 * sched_entity:
256 * task:
257 * se_runnable() == se_weight()
259 * group: [ see update_cfs_group() ]
260 * se_weight() = tg->weight * grq->load_avg / tg->load_avg
261 * se_runnable() = se_weight(se) * grq->runnable_load_avg / grq->load_avg
263 * load_sum := runnable_sum
264 * load_avg = se_weight(se) * runnable_avg
266 * runnable_load_sum := runnable_sum
267 * runnable_load_avg = se_runnable(se) * runnable_avg
269 * XXX collapse load_sum and runnable_load_sum
271 * cfq_rq:
273 * load_sum = \Sum se_weight(se) * se->avg.load_sum
274 * load_avg = \Sum se->avg.load_avg
276 * runnable_load_sum = \Sum se_runnable(se) * se->avg.runnable_load_sum
277 * runnable_load_avg = \Sum se->avg.runable_load_avg
280 int __update_load_avg_blocked_se(u64 now, struct sched_entity *se)
282 if (___update_load_sum(now, &se->avg, 0, 0, 0)) {
283 ___update_load_avg(&se->avg, se_weight(se), se_runnable(se));
284 trace_pelt_se_tp(se);
285 return 1;
288 return 0;
291 int __update_load_avg_se(u64 now, struct cfs_rq *cfs_rq, struct sched_entity *se)
293 if (___update_load_sum(now, &se->avg, !!se->on_rq, !!se->on_rq,
294 cfs_rq->curr == se)) {
296 ___update_load_avg(&se->avg, se_weight(se), se_runnable(se));
297 cfs_se_util_change(&se->avg);
298 trace_pelt_se_tp(se);
299 return 1;
302 return 0;
305 int __update_load_avg_cfs_rq(u64 now, struct cfs_rq *cfs_rq)
307 if (___update_load_sum(now, &cfs_rq->avg,
308 scale_load_down(cfs_rq->load.weight),
309 scale_load_down(cfs_rq->runnable_weight),
310 cfs_rq->curr != NULL)) {
312 ___update_load_avg(&cfs_rq->avg, 1, 1);
313 trace_pelt_cfs_tp(cfs_rq);
314 return 1;
317 return 0;
321 * rt_rq:
323 * util_sum = \Sum se->avg.util_sum but se->avg.util_sum is not tracked
324 * util_sum = cpu_scale * load_sum
325 * runnable_load_sum = load_sum
327 * load_avg and runnable_load_avg are not supported and meaningless.
331 int update_rt_rq_load_avg(u64 now, struct rq *rq, int running)
333 if (___update_load_sum(now, &rq->avg_rt,
334 running,
335 running,
336 running)) {
338 ___update_load_avg(&rq->avg_rt, 1, 1);
339 trace_pelt_rt_tp(rq);
340 return 1;
343 return 0;
347 * dl_rq:
349 * util_sum = \Sum se->avg.util_sum but se->avg.util_sum is not tracked
350 * util_sum = cpu_scale * load_sum
351 * runnable_load_sum = load_sum
355 int update_dl_rq_load_avg(u64 now, struct rq *rq, int running)
357 if (___update_load_sum(now, &rq->avg_dl,
358 running,
359 running,
360 running)) {
362 ___update_load_avg(&rq->avg_dl, 1, 1);
363 trace_pelt_dl_tp(rq);
364 return 1;
367 return 0;
370 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
372 * irq:
374 * util_sum = \Sum se->avg.util_sum but se->avg.util_sum is not tracked
375 * util_sum = cpu_scale * load_sum
376 * runnable_load_sum = load_sum
380 int update_irq_load_avg(struct rq *rq, u64 running)
382 int ret = 0;
385 * We can't use clock_pelt because irq time is not accounted in
386 * clock_task. Instead we directly scale the running time to
387 * reflect the real amount of computation
389 running = cap_scale(running, arch_scale_freq_capacity(cpu_of(rq)));
390 running = cap_scale(running, arch_scale_cpu_capacity(cpu_of(rq)));
393 * We know the time that has been used by interrupt since last update
394 * but we don't when. Let be pessimistic and assume that interrupt has
395 * happened just before the update. This is not so far from reality
396 * because interrupt will most probably wake up task and trig an update
397 * of rq clock during which the metric is updated.
398 * We start to decay with normal context time and then we add the
399 * interrupt context time.
400 * We can safely remove running from rq->clock because
401 * rq->clock += delta with delta >= running
403 ret = ___update_load_sum(rq->clock - running, &rq->avg_irq,
407 ret += ___update_load_sum(rq->clock, &rq->avg_irq,
412 if (ret) {
413 ___update_load_avg(&rq->avg_irq, 1, 1);
414 trace_pelt_irq_tp(rq);
417 return ret;
419 #endif