1 .TH "CPUPOWER-IDLE-INFO" "1" "0.1" "" "cpupowe 1 .TH "CPUPOWER-IDLE-INFO" "1" "0.1" "" "cpupower Manual"
2 .SH "NAME" 2 .SH "NAME"
3 .LP 3 .LP
4 cpupower\-idle\-info \- Utility to retrieve cp 4 cpupower\-idle\-info \- Utility to retrieve cpu idle kernel information
5 .SH "SYNTAX" 5 .SH "SYNTAX"
6 .LP 6 .LP
7 cpupower [ \-c cpulist ] idle\-info [\fIoption 7 cpupower [ \-c cpulist ] idle\-info [\fIoptions\fP]
8 .SH "DESCRIPTION" 8 .SH "DESCRIPTION"
9 .LP 9 .LP
10 A tool which prints out per cpu idle informati 10 A tool which prints out per cpu idle information helpful to developers and interested users.
11 .SH "OPTIONS" 11 .SH "OPTIONS"
12 .LP 12 .LP
13 .TP 13 .TP
14 \fB\-f\fR \fB\-\-silent\fR 14 \fB\-f\fR \fB\-\-silent\fR
15 Only print a summary of all available C-states 15 Only print a summary of all available C-states in the system.
16 .TP 16 .TP
17 \fB\-e\fR \fB\-\-proc\fR 17 \fB\-e\fR \fB\-\-proc\fR
18 deprecated. 18 deprecated.
19 Prints out idle information in old /proc/acpi/ 19 Prints out idle information in old /proc/acpi/processor/*/power format. This
20 interface has been removed from the kernel for 20 interface has been removed from the kernel for quite some time, do not let
21 further code depend on this option, best do no 21 further code depend on this option, best do not use it.
22 22
23 .SH IDLE\-INFO DESCRIPTIONS 23 .SH IDLE\-INFO DESCRIPTIONS
24 CPU sleep state statistics and descriptions ar 24 CPU sleep state statistics and descriptions are retrieved from sysfs files,
25 exported by the cpuidle kernel subsystem. The 25 exported by the cpuidle kernel subsystem. The kernel only updates these
26 statistics when it enters or leaves an idle st 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 b 27 a very busy system, these statistics may not be accurate. They still provide a
28 good overview about the usage and availability 28 good overview about the usage and availability of processor sleep states on
29 the platform. 29 the platform.
30 30
31 Be aware that the sleep states as exported by 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 c 32 the Linux kernel may not exactly reflect the capabilities of the
33 processor. This often is the case on the X86 a 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 h 34 driver is used. It is also possible that the hardware overrules the kernel
35 requests, due to internal activity monitors or 35 requests, due to internal activity monitors or other reasons.
36 On recent X86 platforms it is often possible t 36 On recent X86 platforms it is often possible to read out hardware registers
37 which monitor the duration of sleep states the 37 which monitor the duration of sleep states the processor resided in. The
38 cpupower monitor tool (cpupower\-monitor(1)) c 38 cpupower monitor tool (cpupower\-monitor(1)) can be used to show real sleep
39 state residencies. Please refer to the archite 39 state residencies. Please refer to the architecture specific description
40 section below. 40 section below.
41 41
42 .SH IDLE\-INFO ARCHITECTURE SPECIFIC DESCRIPTI 42 .SH IDLE\-INFO ARCHITECTURE SPECIFIC DESCRIPTIONS
43 .SS "X86" 43 .SS "X86"
44 POLL idle state 44 POLL idle state
45 45
46 If cpuidle is active, X86 platforms have one s 46 If cpuidle is active, X86 platforms have one special idle state.
47 The POLL idle state is not a real 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 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 t 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 50 very soon and entering any real hardware idle state may result in a slight
51 performance penalty. 51 performance penalty.
52 52
53 There exist two different cpuidle drivers on t 53 There exist two different cpuidle drivers on the X86 architecture platform:
54 54
55 "acpi_idle" cpuidle driver 55 "acpi_idle" cpuidle driver
56 56
57 The acpi_idle cpuidle driver retrieves availab 57 The acpi_idle cpuidle driver retrieves available sleep states (C\-states) from
58 the ACPI BIOS tables (from the _CST ACPI funct 58 the ACPI BIOS tables (from the _CST ACPI function on recent platforms or from
59 the FADT BIOS table on older ones). 59 the FADT BIOS table on older ones).
60 The C1 state is not retrieved from ACPI tables 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 m 61 the kernel will call the hlt instruction (or mwait on Intel).
62 62
63 "intel_idle" cpuidle driver 63 "intel_idle" cpuidle driver
64 64
65 In kernel 2.6.36 the intel_idle driver was int 65 In kernel 2.6.36 the intel_idle driver was introduced.
66 It only serves recent Intel CPUs (Nehalem, Wes 66 It only serves recent Intel CPUs (Nehalem, Westmere, Sandybridge, Atoms or
67 newer). On older Intel CPUs the acpi_idle driv 67 newer). On older Intel CPUs the acpi_idle driver is still used (if the BIOS
68 provides C\-state ACPI tables). 68 provides C\-state ACPI tables).
69 The intel_idle driver knows the sleep state ca 69 The intel_idle driver knows the sleep state capabilities of the processor and
70 ignores ACPI BIOS exported processor sleep sta 70 ignores ACPI BIOS exported processor sleep states tables.
71 71
72 .SH "REMARKS" 72 .SH "REMARKS"
73 .LP 73 .LP
74 By default only values of core zero are displa 74 By default only values of core zero are displayed. How to display settings of
75 other cores is described in the cpupower(1) ma 75 other cores is described in the cpupower(1) manpage in the \-\-cpu option
76 section. 76 section.
77 .SH REFERENCES 77 .SH REFERENCES
78 https://uefi.org/specifications 78 https://uefi.org/specifications
79 .SH "FILES" 79 .SH "FILES"
80 .nf 80 .nf
81 \fI/sys/devices/system/cpu/cpu*/cpuidle/state* 81 \fI/sys/devices/system/cpu/cpu*/cpuidle/state*\fP
82 \fI/sys/devices/system/cpu/cpuidle/*\fP 82 \fI/sys/devices/system/cpu/cpuidle/*\fP
83 .fi 83 .fi
84 .SH "AUTHORS" 84 .SH "AUTHORS"
85 .nf 85 .nf
86 Thomas Renninger <trenn@suse.de> 86 Thomas Renninger <trenn@suse.de>
87 .fi 87 .fi
88 .SH "SEE ALSO" 88 .SH "SEE ALSO"
89 .LP 89 .LP
90 cpupower(1), cpupower\-monitor(1), cpupower\-i 90 cpupower(1), cpupower\-monitor(1), cpupower\-info(1), cpupower\-set(1),
91 cpupower\-idle\-set(1) 91 cpupower\-idle\-set(1)
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