|.TH "CPUPOWER-IDLE-INFO" "1" "0.1" "" "cpupower Manual"
|cpupower\-idle\-info \- Utility to retrieve cpu idle kernel information
|cpupower [ \-c cpulist ] idle\-info [\fIoptions\fP]
|A tool which prints out per cpu idle information helpful to developers and interested users.
|Only print a summary of all available C-states in the system.
|Prints out idle information in old /proc/acpi/processor/*/power format. This
|interface has been removed from the kernel for quite some time, do not let
|further code depend on this option, best do not use it.
|.SH IDLE\-INFO DESCRIPTIONS
|CPU sleep state statistics and descriptions are retrieved from sysfs files,
|exported by the cpuidle kernel subsystem. The kernel only updates these
|statistics when it enters or leaves an idle state, therefore on a very idle or
|a very busy system, these statistics may not be accurate. They still provide a
|good overview about the usage and availability of processor sleep states on
|Be aware that the sleep states as exported by the hardware or BIOS and used by
|the Linux kernel may not exactly reflect the capabilities of the
|processor. This often is the case on the X86 architecture when the acpi_idle
|driver is used. It is also possible that the hardware overrules the kernel
|requests, due to internal activity monitors or other reasons.
|On recent X86 platforms it is often possible to read out hardware registers
|which monitor the duration of sleep states the processor resided in. The
|cpupower monitor tool (cpupower\-monitor(1)) can be used to show real sleep
|state residencies. Please refer to the architecture specific description
|.SH IDLE\-INFO ARCHITECTURE SPECIFIC DESCRIPTIONS
|POLL idle state
|If cpuidle is active, X86 platforms have one special idle state.
|The POLL idle state is not a real idle state, it does not save any
|power. Instead, a busy\-loop is executed doing nothing for a short period of
|time. This state is used if the kernel knows that work has to be processed
|very soon and entering any real hardware idle state may result in a slight
|There exist two different cpuidle drivers on the X86 architecture platform:
|"acpi_idle" cpuidle driver
|The acpi_idle cpuidle driver retrieves available sleep states (C\-states) from
|the ACPI BIOS tables (from the _CST ACPI function on recent platforms or from
|the FADT BIOS table on older ones).
|The C1 state is not retrieved from ACPI tables. If the C1 state is entered,
|the kernel will call the hlt instruction (or mwait on Intel).
|"intel_idle" cpuidle driver
|In kernel 2.6.36 the intel_idle driver was introduced.
|It only serves recent Intel CPUs (Nehalem, Westmere, Sandybridge, Atoms or
|newer). On older Intel CPUs the acpi_idle driver is still used (if the BIOS
|provides C\-state ACPI tables).
|The intel_idle driver knows the sleep state capabilities of the processor and
|ignores ACPI BIOS exported processor sleep states tables.
|By default only values of core zero are displayed. How to display settings of
|other cores is described in the cpupower(1) manpage in the \-\-cpu option
|Thomas Renninger <email@example.com>
|.SH "SEE ALSO"
|cpupower(1), cpupower\-monitor(1), cpupower\-info(1), cpupower\-set(1),