1
2
3		Supporting multiple CPU idle levels in kernel
4
5				cpuidle sysfs
6
7System global cpuidle related information and tunables are under
8/sys/devices/system/cpu/cpuidle
9
10The current interfaces in this directory has self-explanatory names:
11* current_driver
12* current_governor_ro
13
14With cpuidle_sysfs_switch boot option (meant for developer testing)
15following objects are visible instead.
16* current_driver
17* available_governors
18* current_governor
19In this case users can switch the governor at run time by writing
20to current_governor.
21
22
23Per logical CPU specific cpuidle information are under
24/sys/devices/system/cpu/cpuX/cpuidle
25for each online cpu X
26
27--------------------------------------------------------------------------------
28# ls -lR /sys/devices/system/cpu/cpu0/cpuidle/
29/sys/devices/system/cpu/cpu0/cpuidle/:
30total 0
31drwxr-xr-x 2 root root 0 Feb  8 10:42 state0
32drwxr-xr-x 2 root root 0 Feb  8 10:42 state1
33drwxr-xr-x 2 root root 0 Feb  8 10:42 state2
34drwxr-xr-x 2 root root 0 Feb  8 10:42 state3
35
36/sys/devices/system/cpu/cpu0/cpuidle/state0:
37total 0
38-r--r--r-- 1 root root 4096 Feb  8 10:42 desc
39-rw-r--r-- 1 root root 4096 Feb  8 10:42 disable
40-r--r--r-- 1 root root 4096 Feb  8 10:42 latency
41-r--r--r-- 1 root root 4096 Feb  8 10:42 name
42-r--r--r-- 1 root root 4096 Feb  8 10:42 power
43-r--r--r-- 1 root root 4096 Feb  8 10:42 time
44-r--r--r-- 1 root root 4096 Feb  8 10:42 usage
45
46/sys/devices/system/cpu/cpu0/cpuidle/state1:
47total 0
48-r--r--r-- 1 root root 4096 Feb  8 10:42 desc
49-rw-r--r-- 1 root root 4096 Feb  8 10:42 disable
50-r--r--r-- 1 root root 4096 Feb  8 10:42 latency
51-r--r--r-- 1 root root 4096 Feb  8 10:42 name
52-r--r--r-- 1 root root 4096 Feb  8 10:42 power
53-r--r--r-- 1 root root 4096 Feb  8 10:42 time
54-r--r--r-- 1 root root 4096 Feb  8 10:42 usage
55
56/sys/devices/system/cpu/cpu0/cpuidle/state2:
57total 0
58-r--r--r-- 1 root root 4096 Feb  8 10:42 desc
59-rw-r--r-- 1 root root 4096 Feb  8 10:42 disable
60-r--r--r-- 1 root root 4096 Feb  8 10:42 latency
61-r--r--r-- 1 root root 4096 Feb  8 10:42 name
62-r--r--r-- 1 root root 4096 Feb  8 10:42 power
63-r--r--r-- 1 root root 4096 Feb  8 10:42 time
64-r--r--r-- 1 root root 4096 Feb  8 10:42 usage
65
66/sys/devices/system/cpu/cpu0/cpuidle/state3:
67total 0
68-r--r--r-- 1 root root 4096 Feb  8 10:42 desc
69-rw-r--r-- 1 root root 4096 Feb  8 10:42 disable
70-r--r--r-- 1 root root 4096 Feb  8 10:42 latency
71-r--r--r-- 1 root root 4096 Feb  8 10:42 name
72-r--r--r-- 1 root root 4096 Feb  8 10:42 power
73-r--r--r-- 1 root root 4096 Feb  8 10:42 time
74-r--r--r-- 1 root root 4096 Feb  8 10:42 usage
75--------------------------------------------------------------------------------
76
77
78* desc : Small description about the idle state (string)
79* disable : Option to disable this idle state (bool) -> see note below
80* latency : Latency to exit out of this idle state (in microseconds)
81* name : Name of the idle state (string)
82* power : Power consumed while in this idle state (in milliwatts)
83* time : Total time spent in this idle state (in microseconds)
84* usage : Number of times this state was entered (count)
85
86Note:
87The behavior and the effect of the disable variable depends on the
88implementation of a particular governor. In the ladder governor, for
89example, it is not coherent, i.e. if one is disabling a light state,
90then all deeper states are disabled as well, but the disable variable
91does not reflect it. Likewise, if one enables a deep state but a lighter
92state still is disabled, then this has no effect.
93