Commit aa5eee35 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki

Documentation: admin-guide: PM: Add cpuidle document

Important information is missing from user/admin cpuidle documentation
available today, so add a new user/admin document for cpuidle containing
current and comprehensive information to admin-guide and drop the old
.txt documents it is replacing.
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
parent 2e6e902d
This diff is collapsed.
...@@ -5,5 +5,6 @@ Working-State Power Management ...@@ -5,5 +5,6 @@ Working-State Power Management
.. toctree:: .. toctree::
:maxdepth: 2 :maxdepth: 2
cpuidle
cpufreq cpufreq
intel_pstate intel_pstate
Supporting multiple CPU idle levels in kernel
cpuidle
General Information:
Various CPUs today support multiple idle levels that are differentiated
by varying exit latencies and power consumption during idle.
cpuidle is a generic in-kernel infrastructure that separates
idle policy (governor) from idle mechanism (driver) and provides a
standardized infrastructure to support independent development of
governors and drivers.
cpuidle resides under drivers/cpuidle.
Boot options:
"cpuidle_sysfs_switch"
enables current_governor interface in /sys/devices/system/cpu/cpuidle/,
which can be used to switch governors at run time. This boot option
is meant for developer testing only. In normal usage, kernel picks the
best governor based on governor ratings.
SEE ALSO: sysfs.txt in this directory.
Supporting multiple CPU idle levels in kernel
cpuidle sysfs
System global cpuidle related information and tunables are under
/sys/devices/system/cpu/cpuidle
The current interfaces in this directory has self-explanatory names:
* current_driver
* current_governor_ro
With cpuidle_sysfs_switch boot option (meant for developer testing)
following objects are visible instead.
* current_driver
* available_governors
* current_governor
In this case users can switch the governor at run time by writing
to current_governor.
Per logical CPU specific cpuidle information are under
/sys/devices/system/cpu/cpuX/cpuidle
for each online cpu X
--------------------------------------------------------------------------------
# ls -lR /sys/devices/system/cpu/cpu0/cpuidle/
/sys/devices/system/cpu/cpu0/cpuidle/:
total 0
drwxr-xr-x 2 root root 0 Feb 8 10:42 state0
drwxr-xr-x 2 root root 0 Feb 8 10:42 state1
drwxr-xr-x 2 root root 0 Feb 8 10:42 state2
drwxr-xr-x 2 root root 0 Feb 8 10:42 state3
/sys/devices/system/cpu/cpu0/cpuidle/state0:
total 0
-r--r--r-- 1 root root 4096 Feb 8 10:42 desc
-rw-r--r-- 1 root root 4096 Feb 8 10:42 disable
-r--r--r-- 1 root root 4096 Feb 8 10:42 latency
-r--r--r-- 1 root root 4096 Feb 8 10:42 name
-r--r--r-- 1 root root 4096 Feb 8 10:42 power
-r--r--r-- 1 root root 4096 Feb 8 10:42 residency
-r--r--r-- 1 root root 4096 Feb 8 10:42 time
-r--r--r-- 1 root root 4096 Feb 8 10:42 usage
/sys/devices/system/cpu/cpu0/cpuidle/state1:
total 0
-r--r--r-- 1 root root 4096 Feb 8 10:42 desc
-rw-r--r-- 1 root root 4096 Feb 8 10:42 disable
-r--r--r-- 1 root root 4096 Feb 8 10:42 latency
-r--r--r-- 1 root root 4096 Feb 8 10:42 name
-r--r--r-- 1 root root 4096 Feb 8 10:42 power
-r--r--r-- 1 root root 4096 Feb 8 10:42 residency
-r--r--r-- 1 root root 4096 Feb 8 10:42 time
-r--r--r-- 1 root root 4096 Feb 8 10:42 usage
/sys/devices/system/cpu/cpu0/cpuidle/state2:
total 0
-r--r--r-- 1 root root 4096 Feb 8 10:42 desc
-rw-r--r-- 1 root root 4096 Feb 8 10:42 disable
-r--r--r-- 1 root root 4096 Feb 8 10:42 latency
-r--r--r-- 1 root root 4096 Feb 8 10:42 name
-r--r--r-- 1 root root 4096 Feb 8 10:42 power
-r--r--r-- 1 root root 4096 Feb 8 10:42 residency
-r--r--r-- 1 root root 4096 Feb 8 10:42 time
-r--r--r-- 1 root root 4096 Feb 8 10:42 usage
/sys/devices/system/cpu/cpu0/cpuidle/state3:
total 0
-r--r--r-- 1 root root 4096 Feb 8 10:42 desc
-rw-r--r-- 1 root root 4096 Feb 8 10:42 disable
-r--r--r-- 1 root root 4096 Feb 8 10:42 latency
-r--r--r-- 1 root root 4096 Feb 8 10:42 name
-r--r--r-- 1 root root 4096 Feb 8 10:42 power
-r--r--r-- 1 root root 4096 Feb 8 10:42 residency
-r--r--r-- 1 root root 4096 Feb 8 10:42 time
-r--r--r-- 1 root root 4096 Feb 8 10:42 usage
--------------------------------------------------------------------------------
* desc : Small description about the idle state (string)
* disable : Option to disable this idle state (bool) -> see note below
* latency : Latency to exit out of this idle state (in microseconds)
* residency : Time after which a state becomes more effecient than any
shallower state (in microseconds)
* name : Name of the idle state (string)
* power : Power consumed while in this idle state (in milliwatts)
* time : Total time spent in this idle state (in microseconds)
* usage : Number of times this state was entered (count)
Note:
The behavior and the effect of the disable variable depends on the
implementation of a particular governor. In the ladder governor, for
example, it is not coherent, i.e. if one is disabling a light state,
then all deeper states are disabled as well, but the disable variable
does not reflect it. Likewise, if one enables a deep state but a lighter
state still is disabled, then this has no effect.
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment