cpupower-idle-info(1)
NAME
cpupower-idle-info - Utility to retrieve cpu idle kernel information
SYNTAX
cpupower [ -c cpulist ] idle-info [options]
DESCRIPTION
A tool which prints out per cpu idle information helpful to developers and interested users.
OPTIONS
-f --silent
Only print a summary of all available C-states in the system.
-e --proc
deprecated. 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.
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 the platform. 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 section below.
IDLE-INFO ARCHITECTURE SPECIFIC DESCRIPTIONS
X86 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 performance penalty. 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.
REMARKS
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 section.
REFERENCES
http://www.acpi.info/spec.htm
FILES
/sys/devices/system/cpu/cpu*/cpuidle/state* /sys/devices/system/cpu/cpuidle/*
AUTHORS
Thomas Renninger <trenn@suse.de>
SEE ALSO
cpupower(1), cpupower-monitor(1), cpupower-info(1), cpupower-set(1), cpupower-idle-set(1) 0.1 CPUPOWER-IDLE-INFO(1)
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
