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
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
|
=======================
Power Capping Framework
=======================
The power capping framework provides a consistent interface between the kernel
and the user space that allows power capping drivers to expose the settings to
user space in a uniform way.
Terminology
===========
The framework exposes power capping devices to user space via sysfs in the
form of a tree of objects. The objects at the root level of the tree represent
'control types', which correspond to different methods of power capping. For
example, the intel-rapl control type represents the Intel "Running Average
Power Limit" (RAPL) technology, whereas the 'idle-injection' control type
corresponds to the use of idle injection for controlling power.
Power zones represent different parts of the system, which can be controlled and
monitored using the power capping method determined by the control type the
given zone belongs to. They each contain attributes for monitoring power, as
well as controls represented in the form of power constraints. If the parts of
the system represented by different power zones are hierarchical (that is, one
bigger part consists of multiple smaller parts that each have their own power
controls), those power zones may also be organized in a hierarchy with one
parent power zone containing multiple subzones and so on to reflect the power
control topology of the system. In that case, it is possible to apply power
capping to a set of devices together using the parent power zone and if more
fine grained control is required, it can be applied through the subzones.
Example sysfs interface tree::
/sys/devices/virtual/powercap
└──intel-rapl
├──intel-rapl:0
│ ├──constraint_0_name
│ ├──constraint_0_power_limit_uw
│ ├──constraint_0_time_window_us
│ ├──constraint_1_name
│ ├──constraint_1_power_limit_uw
│ ├──constraint_1_time_window_us
│ ├──device -> ../../intel-rapl
│ ├──energy_uj
│ ├──intel-rapl:0:0
│ │ ├──constraint_0_name
│ │ ├──constraint_0_power_limit_uw
│ │ ├──constraint_0_time_window_us
│ │ ├──constraint_1_name
│ │ ├──constraint_1_power_limit_uw
│ │ ├──constraint_1_time_window_us
│ │ ├──device -> ../../intel-rapl:0
│ │ ├──energy_uj
│ │ ├──max_energy_range_uj
│ │ ├──name
│ │ ├──enabled
│ │ ├──power
│ │ │ ├──async
│ │ │ []
│ │ ├──subsystem -> ../../../../../../class/power_cap
│ │ └──uevent
│ ├──intel-rapl:0:1
│ │ ├──constraint_0_name
│ │ ├──constraint_0_power_limit_uw
│ │ ├──constraint_0_time_window_us
│ │ ├──constraint_1_name
│ │ ├──constraint_1_power_limit_uw
│ │ ├──constraint_1_time_window_us
│ │ ├──device -> ../../intel-rapl:0
│ │ ├──energy_uj
│ │ ├──max_energy_range_uj
│ │ ├──name
│ │ ├──enabled
│ │ ├──power
│ │ │ ├──async
│ │ │ []
│ │ ├──subsystem -> ../../../../../../class/power_cap
│ │ └──uevent
│ ├──max_energy_range_uj
│ ├──max_power_range_uw
│ ├──name
│ ├──enabled
│ ├──power
│ │ ├──async
│ │ []
│ ├──subsystem -> ../../../../../class/power_cap
│ ├──enabled
│ ├──uevent
├──intel-rapl:1
│ ├──constraint_0_name
│ ├──constraint_0_power_limit_uw
│ ├──constraint_0_time_window_us
│ ├──constraint_1_name
│ ├──constraint_1_power_limit_uw
│ ├──constraint_1_time_window_us
│ ├──device -> ../../intel-rapl
│ ├──energy_uj
│ ├──intel-rapl:1:0
│ │ ├──constraint_0_name
│ │ ├──constraint_0_power_limit_uw
│ │ ├──constraint_0_time_window_us
│ │ ├──constraint_1_name
│ │ ├──constraint_1_power_limit_uw
│ │ ├──constraint_1_time_window_us
│ │ ├──device -> ../../intel-rapl:1
│ │ ├──energy_uj
│ │ ├──max_energy_range_uj
│ │ ├──name
│ │ ├──enabled
│ │ ├──power
│ │ │ ├──async
│ │ │ []
│ │ ├──subsystem -> ../../../../../../class/power_cap
│ │ └──uevent
│ ├──intel-rapl:1:1
│ │ ├──constraint_0_name
│ │ ├──constraint_0_power_limit_uw
│ │ ├──constraint_0_time_window_us
│ │ ├──constraint_1_name
│ │ ├──constraint_1_power_limit_uw
│ │ ├──constraint_1_time_window_us
│ │ ├──device -> ../../intel-rapl:1
│ │ ├──energy_uj
│ │ ├──max_energy_range_uj
│ │ ├──name
│ │ ├──enabled
│ │ ├──power
│ │ │ ├──async
│ │ │ []
│ │ ├──subsystem -> ../../../../../../class/power_cap
│ │ └──uevent
│ ├──max_energy_range_uj
│ ├──max_power_range_uw
│ ├──name
│ ├──enabled
│ ├──power
│ │ ├──async
│ │ []
│ ├──subsystem -> ../../../../../class/power_cap
│ ├──uevent
├──power
│ ├──async
│ []
├──subsystem -> ../../../../class/power_cap
├──enabled
└──uevent
The above example illustrates a case in which the Intel RAPL technology,
available in Intel® IA-64 and IA-32 Processor Architectures, is used. There is one
control type called intel-rapl which contains two power zones, intel-rapl:0 and
intel-rapl:1, representing CPU packages. Each of these power zones contains
two subzones, intel-rapl:j:0 and intel-rapl:j:1 (j = 0, 1), representing the
"core" and the "uncore" parts of the given CPU package, respectively. All of
the zones and subzones contain energy monitoring attributes (energy_uj,
max_energy_range_uj) and constraint attributes (constraint_*) allowing controls
to be applied (the constraints in the 'package' power zones apply to the whole
CPU packages and the subzone constraints only apply to the respective parts of
the given package individually). Since Intel RAPL doesn't provide instantaneous
power value, there is no power_uw attribute.
In addition to that, each power zone contains a name attribute, allowing the
part of the system represented by that zone to be identified.
For example::
cat /sys/class/power_cap/intel-rapl/intel-rapl:0/name
package-0
---------
The Intel RAPL technology allows two constraints, short term and long term,
with two different time windows to be applied to each power zone. Thus for
each zone there are 2 attributes representing the constraint names, 2 power
limits and 2 attributes representing the sizes of the time windows. Such that,
constraint_j_* attributes correspond to the jth constraint (j = 0,1).
For example::
constraint_0_name
constraint_0_power_limit_uw
constraint_0_time_window_us
constraint_1_name
constraint_1_power_limit_uw
constraint_1_time_window_us
Power Zone Attributes
=====================
Monitoring attributes
---------------------
energy_uj (rw)
Current energy counter in micro joules. Write "0" to reset.
If the counter can not be reset, then this attribute is read only.
max_energy_range_uj (ro)
Range of the above energy counter in micro-joules.
power_uw (ro)
Current power in micro watts.
max_power_range_uw (ro)
Range of the above power value in micro-watts.
name (ro)
Name of this power zone.
It is possible that some domains have both power ranges and energy counter ranges;
however, only one is mandatory.
Constraints
-----------
constraint_X_power_limit_uw (rw)
Power limit in micro watts, which should be applicable for the
time window specified by "constraint_X_time_window_us".
constraint_X_time_window_us (rw)
Time window in micro seconds.
constraint_X_name (ro)
An optional name of the constraint
constraint_X_max_power_uw(ro)
Maximum allowed power in micro watts.
constraint_X_min_power_uw(ro)
Minimum allowed power in micro watts.
constraint_X_max_time_window_us(ro)
Maximum allowed time window in micro seconds.
constraint_X_min_time_window_us(ro)
Minimum allowed time window in micro seconds.
Except power_limit_uw and time_window_us other fields are optional.
Common zone and control type attributes
---------------------------------------
enabled (rw): Enable/Disable controls at zone level or for all zones using
a control type.
Power Cap Client Driver Interface
=================================
The API summary:
Call powercap_register_control_type() to register control type object.
Call powercap_register_zone() to register a power zone (under a given
control type), either as a top-level power zone or as a subzone of another
power zone registered earlier.
The number of constraints in a power zone and the corresponding callbacks have
to be defined prior to calling powercap_register_zone() to register that zone.
To Free a power zone call powercap_unregister_zone().
To free a control type object call powercap_unregister_control_type().
Detailed API can be generated using kernel-doc on include/linux/powercap.h.
|
