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 residency
44-r--r--r-- 1 root root 4096 Feb  8 10:42 time
45-r--r--r-- 1 root root 4096 Feb  8 10:42 usage
46
47/sys/devices/system/cpu/cpu0/cpuidle/state1:
48total 0
49-r--r--r-- 1 root root 4096 Feb  8 10:42 desc
50-rw-r--r-- 1 root root 4096 Feb  8 10:42 disable
51-r--r--r-- 1 root root 4096 Feb  8 10:42 latency
52-r--r--r-- 1 root root 4096 Feb  8 10:42 name
53-r--r--r-- 1 root root 4096 Feb  8 10:42 power
54-r--r--r-- 1 root root 4096 Feb  8 10:42 residency
55-r--r--r-- 1 root root 4096 Feb  8 10:42 time
56-r--r--r-- 1 root root 4096 Feb  8 10:42 usage
57
58/sys/devices/system/cpu/cpu0/cpuidle/state2:
59total 0
60-r--r--r-- 1 root root 4096 Feb  8 10:42 desc
61-rw-r--r-- 1 root root 4096 Feb  8 10:42 disable
62-r--r--r-- 1 root root 4096 Feb  8 10:42 latency
63-r--r--r-- 1 root root 4096 Feb  8 10:42 name
64-r--r--r-- 1 root root 4096 Feb  8 10:42 power
65-r--r--r-- 1 root root 4096 Feb  8 10:42 residency
66-r--r--r-- 1 root root 4096 Feb  8 10:42 time
67-r--r--r-- 1 root root 4096 Feb  8 10:42 usage
68
69/sys/devices/system/cpu/cpu0/cpuidle/state3:
70total 0
71-r--r--r-- 1 root root 4096 Feb  8 10:42 desc
72-rw-r--r-- 1 root root 4096 Feb  8 10:42 disable
73-r--r--r-- 1 root root 4096 Feb  8 10:42 latency
74-r--r--r-- 1 root root 4096 Feb  8 10:42 name
75-r--r--r-- 1 root root 4096 Feb  8 10:42 power
76-r--r--r-- 1 root root 4096 Feb  8 10:42 residency
77-r--r--r-- 1 root root 4096 Feb  8 10:42 time
78-r--r--r-- 1 root root 4096 Feb  8 10:42 usage
79--------------------------------------------------------------------------------
80
81
82* desc : Small description about the idle state (string)
83* disable : Option to disable this idle state (bool) -> see note below
84* latency : Latency to exit out of this idle state (in microseconds)
85* residency : Time after which a state becomes more effecient than any
86  shallower state (in microseconds)
87* name : Name of the idle state (string)
88* power : Power consumed while in this idle state (in milliwatts)
89* time : Total time spent in this idle state (in microseconds)
90* usage : Number of times this state was entered (count)
91
92Note:
93The behavior and the effect of the disable variable depends on the
94implementation of a particular governor. In the ladder governor, for
95example, it is not coherent, i.e. if one is disabling a light state,
96then all deeper states are disabled as well, but the disable variable
97does not reflect it. Likewise, if one enables a deep state but a lighter
98state still is disabled, then this has no effect.
99