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Doc/PM: Sync with intel_powerclamp code behavior 

Commit feb6cd6a0f ("thermal/intel_powerclamp: stop sched tick in forced
idle") changed how idle injection accouting, so we need to update
the documentation accordingly.

This patch also expands more details on the behavior of cur_state.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reported-by: Wang, Xiaolong <xiaolong.wang@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Jacob Pan 2017-04-14 11:19:24 -07:00 committed by Jonathan Corbet
parent 50c28f803a
commit d73350568c
1 changed files with 15 additions and 5 deletions
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20
Documentation/thermal/intel_powerclamp.txt
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@ -268,6 +268,15 @@ cur_state:0
max_state:50
type:intel_powerclamp
cur_state allows user to set the desired idle percentage. Writing 0 to
cur_state will stop idle injection. Writing a value between 1 and
max_state will start the idle injection. Reading cur_state returns the
actual and current idle percentage. This may not be the same value
set by the user in that current idle percentage depends on workload
and includes natural idle. When idle injection is disabled, reading
cur_state returns value -1 instead of 0 which is to avoid confusing
100% busy state with the disabled state.
Example usage:
- To inject 25% idle time
$ sudo sh -c "echo 25 > /sys/class/thermal/cooling_device80/cur_state
@ -278,11 +287,12 @@ then the powerclamp driver will not start idle injection. Using Top
will not show idle injection kernel threads.
If the system is busy (spin test below) and has less than 25% natural
idle time, powerclamp kernel threads will do idle injection, which
appear running to the scheduler. But the overall system idle is still
reflected. In this example, 24.1% idle is shown. This helps the
system admin or user determine the cause of slowdown, when a
powerclamp driver is in action.
idle time, powerclamp kernel threads will do idle injection. Forced
idle time is accounted as normal idle in that common code path is
taken as the idle task.
In this example, 24.1% idle is shown. This helps the system admin or
user determine the cause of slowdown, when a powerclamp driver is in action.
Tasks: 197 total, 1 running, 196 sleeping, 0 stopped, 0 zombie