## page was renamed from Kernel/Reference/fwts/cpufreq
== Firmware Test Suite - cpufreq test ==

The cpufreq test is an experimental test. (and thus may yield incorrect results because of kernel scheduling policies and loading on the machine). It checks [[http://software.intel.com/en-us/blogs/2008/05/29/what-exactly-is-a-p-state-pt-1|Processor Performance States]] (P-States).   The test tries to step through all the various P-states that the BIOS advertised to the processor. For each processor/frequency combination a quick performance value is measured.   

The test will try to validate:

 * Each processor has the same number of frequency states
 * Higher advertised frequencies have a higher performance
 * No duplicate frequency values are reported by the BIOS
 * Is BIOS wrongly doing Sw_All P-state coordination across cores
 * Is BIOS wrongly doing Sw_Any P-state coordination across cores

Note: 
 * Sw_All - Operating System is responsible and will set throttling across all CPUs
 * Sw_Any - Operating System is responsible and will set throttling per CPU.

For more information See section 8.4.2.2 _CSD (C-State Dependency) of the ACPI specification and also drivers/acpi/processor_throttling.c

=== Examples: ===

{{{
sudo fwts cpufreq - 
}}}

..runs the test on your machine and dumps the output to stdout.

== Explanation of test results ==

Certain test results may require a little more explanation. This section will try and give some context to specific test failures.

||Error ID||Explanation||
||CPU``Freq``PStates||Not all processors support the same number of P states, this is inconsistent and very unexpected.||
||CPU``Freq``Dup``Freq||/sys/devices/system/cpu/cpu*/cpufreq/scaling_available_frequencies has a duplicate scaling frequency. This is normally due to a firmware misconfiguration with the ACPI _PSS object, see section 8.4.4.2 _PSS (Performance Supported States) of the ACPI specification.||
||CPU``Freq``SW_ALL||The BIOS may be doing Sw_ALL co-ordination, which is not what we expected.||
||CPU``Freq``SW_ANY||The BIOS may be doing Sw_ANY co-ordination, which is not what we expected.||