admin-guide/thermal/intel_powerclamp.rst

15 	    - Idle Injection
46 idle injection across all online CPU threads was introduced. The goal
57 Idle Injection
70 If the kernel can also inject idle time to the system, then a
73 control system, where the target set point is a user-selected idle
75 between the actual package level C-state residency ratio and the target idle
83 thread synchronizes its idle time and duration, based on the rounding
91 Alignment of idle time around jiffies ensures scalability for HZ
94 kidle_inject/cpu. During idle injection, it runs monitor/mwait idle
98 The NOHZ schedule tick is disabled during idle time, but interrupts
125 In terms of dynamics of the idle control system, package level idle
128 intel_powerclamp driver attempts to enforce the desired idle time
129 instantly as given input (target idle ratio). After injection,
130 powerclamp monitors the actual idle for a given time window and adjust
152 a) determine the effective range of idle injection ratio
160 	   enter idle without extra wakeups (such as external interrupts).
164 	   When an excessive amount of wakeups occurs during idle, an
165 	   additional idle ratio can be added to quiet interrupts, by
213 To compensate for excessive amounts of wakeup during idle, additional
214 idle time is injected when such a condition is detected. Currently,
236 The maximum range that idle injection is allowed is capped at 50
238 forced idle time, excessive interrupts could result in less
241 case, little can be done from the idle injection threads. In most
248 with the changes. During this time, idle injection is out of sync,
251 ratio is updated much less frequently than the idle injection
257 Ivy Bridge system and the 80P Westmere server under 50% idle ratio.
259 target idle ratio. The compensation also increases as the idle ratio
278 cur_state allows user to set the desired idle percentage. Writing 0 to
279 cur_state will stop idle injection. Writing a value between 1 and
280 max_state will start the idle injection. Reading cur_state returns the
281 actual and current idle percentage. This may not be the same value
282 set by the user in that current idle percentage depends on workload
283 and includes natural idle. When idle injection is disabled, reading
289 - To inject 25% idle time::
293 If the system is not busy and has more than 25% idle time already,
294 then the powerclamp driver will not start idle injection. Using Top
295 will not show idle injection kernel threads.
298 idle time, powerclamp kernel threads will do idle injection. Forced
299 idle time is accounted as normal idle in that common code path is
300 taken as the idle task.
302 In this example, 24.1% idle is shown. This helps the system admin or
331 	A bit mask of CPUs to inject idle. The format of the bitmask is same as
340 	Maximum injected idle time to the total CPU time ratio in percent range
342 	this parameter allows to add a max idle percent limit. The default is 50,