Lines Matching +full:25 +full:a
32 Consider the situation where a system’s power consumption must be
68 If the kernel can also inject idle time to the system, then a
70 level C-state. The intel_powerclamp driver is conceived as such a
71 control system, where the target set point is a user-selected idle
82 of jiffies, so accumulated errors can be prevented to avoid a jittery
90 values. This effect can be better visualized using a Perf timechart.
93 for a given "duration", then relinquishes the CPU to other tasks,
98 have a dramatic impact on the effectiveness of the powerclamp driver
119 this document. The controlling CPU is elected at runtime, with a
120 policy that favors BSP, taking into account the possibility of a CPU
124 time is considered largely as a non-causal system where its behavior
128 powerclamp monitors the actual idle for a given time window and adjust
131 When used in a causal control system, such as a temperature control,
133 past samples and outputs are included in the feedback. For example, a
135 maintain a desired target temperature, based on integral and
144 also true for the ability of a system to enter package level C-states.
147 calibration is implemented. The goals for doing such a calibration
150 a) determine the effective range of idle injection ratio
155 a) steady state error compensation
164 A debugfs file is provided for the user to examine compensation
165 progress and results, such as on a Westmere system::
204 adjacent ratios have reached satisfactory level. A confidence level
206 collected during a period without extra interrupts is considered
210 idle time is injected when such a condition is detected. Currently,
211 we have a simple algorithm to double the injection ratio. A possible
213 EOI for level triggered interrupts. But it is a challenge to be
222 to other CPUs, after a CPU offline event.
235 effectiveness. The extreme case would be doing a ping -f to generated
238 normal cases, such as scp a large file, applications can be throttled
252 Tests also show a minor, but measurable, difference between the 4P/8P
260 achieve up to 40% better performance per watt. (measured by a spin
266 The powerclamp driver is registered to the generic thermal layer as a
275 cur_state will stop idle injection. Writing a value between 1 and
284 - To inject 25% idle time::
286 $ sudo sh -c "echo 25 > /sys/class/thermal/cooling_device80/cur_state
288 If the system is not busy and has more than 25% idle time already,
292 If the system is busy (spin test below) and has less than 25% natural
298 user determine the cause of slowdown, when a powerclamp driver is in action::
308 3341 root -51 0 0 0 0 D 25 0.0 0:01.62 kidle_inject/0
309 3344 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/3
310 3342 root -51 0 0 0 0 D 25 0.0 0:01.61 kidle_inject/1
311 3343 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/2
316 Tests have shown that by using the powerclamp driver as a cooling
317 device, a PID based userspace thermal controller can manage to
319 is added. For example, a UltraBook user can compile the kernel under