summaryrefslogtreecommitdiff
path: root/include/linux/energy_model.h
blob: 3f221dbf5f95d9f75b47d4758aede461fba22ad8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_ENERGY_MODEL_H
#define _LINUX_ENERGY_MODEL_H
#include <linux/cpumask.h>
#include <linux/device.h>
#include <linux/jump_label.h>
#include <linux/kobject.h>
#include <linux/rcupdate.h>
#include <linux/sched/cpufreq.h>
#include <linux/sched/topology.h>
#include <linux/types.h>

/**
 * em_perf_state - Performance state of a performance domain
 * @frequency:	The frequency in KHz, for consistency with CPUFreq
 * @power:	The power consumed at this level (by 1 CPU or by a registered
 *		device). It can be a total power: static and dynamic.
 * @cost:	The cost coefficient associated with this level, used during
 *		energy calculation. Equal to: power * max_frequency / frequency
 */
struct em_perf_state {
	unsigned long frequency;
	unsigned long power;
	unsigned long cost;
};

/**
 * em_perf_domain - Performance domain
 * @table:		List of performance states, in ascending order
 * @nr_perf_states:	Number of performance states
 * @milliwatts:		Flag indicating the power values are in milli-Watts
 *			or some other scale.
 * @cpus:		Cpumask covering the CPUs of the domain. It's here
 *			for performance reasons to avoid potential cache
 *			misses during energy calculations in the scheduler
 *			and simplifies allocating/freeing that memory region.
 *
 * In case of CPU device, a "performance domain" represents a group of CPUs
 * whose performance is scaled together. All CPUs of a performance domain
 * must have the same micro-architecture. Performance domains often have
 * a 1-to-1 mapping with CPUFreq policies. In case of other devices the @cpus
 * field is unused.
 */
struct em_perf_domain {
	struct em_perf_state *table;
	int nr_perf_states;
	int milliwatts;
	unsigned long cpus[];
};

#define em_span_cpus(em) (to_cpumask((em)->cpus))

#ifdef CONFIG_ENERGY_MODEL
#define EM_MAX_POWER 0xFFFF

struct em_data_callback {
	/**
	 * active_power() - Provide power at the next performance state of
	 *		a device
	 * @power	: Active power at the performance state
	 *		(modified)
	 * @freq	: Frequency at the performance state in kHz
	 *		(modified)
	 * @dev		: Device for which we do this operation (can be a CPU)
	 *
	 * active_power() must find the lowest performance state of 'dev' above
	 * 'freq' and update 'power' and 'freq' to the matching active power
	 * and frequency.
	 *
	 * In case of CPUs, the power is the one of a single CPU in the domain,
	 * expressed in milli-Watts or an abstract scale. It is expected to
	 * fit in the [0, EM_MAX_POWER] range.
	 *
	 * Return 0 on success.
	 */
	int (*active_power)(unsigned long *power, unsigned long *freq,
			    struct device *dev);
};
#define EM_DATA_CB(_active_power_cb) { .active_power = &_active_power_cb }

struct em_perf_domain *em_cpu_get(int cpu);
struct em_perf_domain *em_pd_get(struct device *dev);
int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
				struct em_data_callback *cb, cpumask_t *span,
				bool milliwatts);
void em_dev_unregister_perf_domain(struct device *dev);

/**
 * em_cpu_energy() - Estimates the energy consumed by the CPUs of a
		performance domain
 * @pd		: performance domain for which energy has to be estimated
 * @max_util	: highest utilization among CPUs of the domain
 * @sum_util	: sum of the utilization of all CPUs in the domain
 * @allowed_cpu_cap	: maximum allowed CPU capacity for the @pd, which
			  might reflect reduced frequency (due to thermal)
 *
 * This function must be used only for CPU devices. There is no validation,
 * i.e. if the EM is a CPU type and has cpumask allocated. It is called from
 * the scheduler code quite frequently and that is why there is not checks.
 *
 * Return: the sum of the energy consumed by the CPUs of the domain assuming
 * a capacity state satisfying the max utilization of the domain.
 */
static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
				unsigned long max_util, unsigned long sum_util,
				unsigned long allowed_cpu_cap)
{
	unsigned long freq, scale_cpu;
	struct em_perf_state *ps;
	int i, cpu;

	if (!sum_util)
		return 0;

	/*
	 * In order to predict the performance state, map the utilization of
	 * the most utilized CPU of the performance domain to a requested
	 * frequency, like schedutil. Take also into account that the real
	 * frequency might be set lower (due to thermal capping). Thus, clamp
	 * max utilization to the allowed CPU capacity before calculating
	 * effective frequency.
	 */
	cpu = cpumask_first(to_cpumask(pd->cpus));
	scale_cpu = arch_scale_cpu_capacity(cpu);
	ps = &pd->table[pd->nr_perf_states - 1];

	max_util = map_util_perf(max_util);
	max_util = min(max_util, allowed_cpu_cap);
	freq = map_util_freq(max_util, ps->frequency, scale_cpu);

	/*
	 * Find the lowest performance state of the Energy Model above the
	 * requested frequency.
	 */
	for (i = 0; i < pd->nr_perf_states; i++) {
		ps = &pd->table[i];
		if (ps->frequency >= freq)
			break;
	}

	/*
	 * The capacity of a CPU in the domain at the performance state (ps)
	 * can be computed as:
	 *
	 *             ps->freq * scale_cpu
	 *   ps->cap = --------------------                          (1)
	 *                 cpu_max_freq
	 *
	 * So, ignoring the costs of idle states (which are not available in
	 * the EM), the energy consumed by this CPU at that performance state
	 * is estimated as:
	 *
	 *             ps->power * cpu_util
	 *   cpu_nrg = --------------------                          (2)
	 *                   ps->cap
	 *
	 * since 'cpu_util / ps->cap' represents its percentage of busy time.
	 *
	 *   NOTE: Although the result of this computation actually is in
	 *         units of power, it can be manipulated as an energy value
	 *         over a scheduling period, since it is assumed to be
	 *         constant during that interval.
	 *
	 * By injecting (1) in (2), 'cpu_nrg' can be re-expressed as a product
	 * of two terms:
	 *
	 *             ps->power * cpu_max_freq   cpu_util
	 *   cpu_nrg = ------------------------ * ---------          (3)
	 *                    ps->freq            scale_cpu
	 *
	 * The first term is static, and is stored in the em_perf_state struct
	 * as 'ps->cost'.
	 *
	 * Since all CPUs of the domain have the same micro-architecture, they
	 * share the same 'ps->cost', and the same CPU capacity. Hence, the
	 * total energy of the domain (which is the simple sum of the energy of
	 * all of its CPUs) can be factorized as:
	 *
	 *            ps->cost * \Sum cpu_util
	 *   pd_nrg = ------------------------                       (4)
	 *                  scale_cpu
	 */
	return ps->cost * sum_util / scale_cpu;
}

/**
 * em_pd_nr_perf_states() - Get the number of performance states of a perf.
 *				domain
 * @pd		: performance domain for which this must be done
 *
 * Return: the number of performance states in the performance domain table
 */
static inline int em_pd_nr_perf_states(struct em_perf_domain *pd)
{
	return pd->nr_perf_states;
}

#else
struct em_data_callback {};
#define EM_DATA_CB(_active_power_cb) { }

static inline
int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states,
				struct em_data_callback *cb, cpumask_t *span,
				bool milliwatts)
{
	return -EINVAL;
}
static inline void em_dev_unregister_perf_domain(struct device *dev)
{
}
static inline struct em_perf_domain *em_cpu_get(int cpu)
{
	return NULL;
}
static inline struct em_perf_domain *em_pd_get(struct device *dev)
{
	return NULL;
}
static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
			unsigned long max_util, unsigned long sum_util,
			unsigned long allowed_cpu_cap)
{
	return 0;
}
static inline int em_pd_nr_perf_states(struct em_perf_domain *pd)
{
	return 0;
}
#endif

#endif