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1 | .TH "CPUPOWER-IDLE-INFO" "1" "0.1" "" "cpupower Manual" |
2 | .SH "NAME" | |
3 | .LP | |
4 | cpupower idle\-info \- Utility to retrieve cpu idle kernel information | |
5 | .SH "SYNTAX" | |
6 | .LP | |
7 | cpupower [ \-c cpulist ] idle\-info [\fIoptions\fP] | |
8 | .SH "DESCRIPTION" | |
9 | .LP | |
10 | A tool which prints out per cpu idle information helpful to developers and interested users. | |
11 | .SH "OPTIONS" | |
12 | .LP | |
13 | .TP | |
14 | \fB\-f\fR \fB\-\-silent\fR | |
15 | Only print a summary of all available C-states in the system. | |
16 | .TP | |
17 | \fB\-e\fR \fB\-\-proc\fR | |
18 | deprecated. | |
19 | Prints out idle information in old /proc/acpi/processor/*/power format. This | |
20 | interface has been removed from the kernel for quite some time, do not let | |
21 | further code depend on this option, best do not use it. | |
22 | ||
23 | .SH IDLE\-INFO DESCRIPTIONS | |
24 | CPU sleep state statistics and descriptions are retrieved from sysfs files, | |
25 | exported by the cpuidle kernel subsystem. The kernel only updates these | |
26 | statistics when it enters or leaves an idle state, therefore on a very idle or | |
27 | a very busy system, these statistics may not be accurate. They still provide a | |
28 | good overview about the usage and availability of processor sleep states on | |
29 | the platform. | |
30 | ||
31 | Be aware that the sleep states as exported by the hardware or BIOS and used by | |
32 | the Linux kernel may not exactly reflect the capabilities of the | |
33 | processor. This often is the case on the X86 architecture when the acpi_idle | |
34 | driver is used. It is also possible that the hardware overrules the kernel | |
35 | requests, due to internal activity monitors or other reasons. | |
36 | On recent X86 platforms it is often possible to read out hardware registers | |
37 | which monitor the duration of sleep states the processor resided in. The | |
38 | cpupower monitor tool (cpupower\-monitor(1)) can be used to show real sleep | |
39 | state residencies. Please refer to the architecture specific description | |
40 | section below. | |
41 | ||
42 | .SH IDLE\-INFO ARCHITECTURE SPECIFIC DESCRIPTIONS | |
43 | .SS "X86" | |
44 | POLL idle state | |
45 | ||
46 | If cpuidle is active, X86 platforms have one special idle state. | |
47 | The POLL idle state is not a real idle state, it does not save any | |
48 | power. Instead, a busy\-loop is executed doing nothing for a short period of | |
49 | time. This state is used if the kernel knows that work has to be processed | |
50 | very soon and entering any real hardware idle state may result in a slight | |
51 | performance penalty. | |
52 | ||
53 | There exist two different cpuidle drivers on the X86 architecture platform: | |
54 | ||
55 | "acpi_idle" cpuidle driver | |
56 | ||
57 | The acpi_idle cpuidle driver retrieves available sleep states (C\-states) from | |
58 | the ACPI BIOS tables (from the _CST ACPI function on recent platforms or from | |
59 | the FADT BIOS table on older ones). | |
60 | The C1 state is not retrieved from ACPI tables. If the C1 state is entered, | |
61 | the kernel will call the hlt instruction (or mwait on Intel). | |
62 | ||
63 | "intel_idle" cpuidle driver | |
64 | ||
65 | In kernel 2.6.36 the intel_idle driver was introduced. | |
66 | It only serves recent Intel CPUs (Nehalem, Westmere, Sandybridge, Atoms or | |
67 | newer). On older Intel CPUs the acpi_idle driver is still used (if the BIOS | |
68 | provides C\-state ACPI tables). | |
69 | The intel_idle driver knows the sleep state capabilities of the processor and | |
70 | ignores ACPI BIOS exported processor sleep states tables. | |
71 | ||
72 | .SH "REMARKS" | |
73 | .LP | |
74 | By default only values of core zero are displayed. How to display settings of | |
75 | other cores is described in the cpupower(1) manpage in the \-\-cpu option | |
76 | section. | |
77 | .SH REFERENCES | |
78 | http://www.acpi.info/spec.htm | |
79 | .SH "FILES" | |
80 | .nf | |
81 | \fI/sys/devices/system/cpu/cpu*/cpuidle/state*\fP | |
82 | \fI/sys/devices/system/cpu/cpuidle/*\fP | |
83 | .fi | |
84 | .SH "AUTHORS" | |
85 | .nf | |
86 | Thomas Renninger <trenn@suse.de> | |
87 | .fi | |
88 | .SH "SEE ALSO" | |
89 | .LP | |
5094d271 TR |
90 | cpupower(1), cpupower\-monitor(1), cpupower\-info(1), cpupower\-set(1), |
91 | cpupower\-idle\-set(1) |