Red Hat Bugzilla – Bug 588702
v7 incorrectly uses 'processor.can_throttle' to plan CPUSCALING tests
Last modified: 2010-10-23 11:12:04 EDT
The v7 cert suite uses the info “processor.can_throttle = true (bool)” to find out if the CPUs are scalable. This is incorrect because:
throttling (T states)
..are different to:
cpu_scaling (C states)
In some old documents it seems to be the same, but there’s now a mandatory difference between both states.
A system can offer “cpu_scaling”, but must not offer “throttling”. It depends what is implemented in the BIOS.
It is being 'assumed' (but not yet proven) that this is the reason that 'v7 plan' never automatically adds CPUSCALING tests to the plan on Fujitsu hardware.
v7 does not automatically add CPUSCALING tests for each core on Fujitsu hardware
v7 should automatically add CPUSCALING tests for each core on Fujitsu hardware
We're seeing the same issue at SGI. With Intel 5600 cpus and AMI bios,
cpuscaling is not turned on by v7. But with the same cpus and an Intel
bios cpu scaling is automatically selected.
Created attachment 435093 [details]
cpuscaling test patch to check /sys/../cpu<n>/cpufreq/scaling_available_frequencies for test planning
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.
Technical note added. If any revisions are required, please edit the "Technical Notes" field
accordingly. All revisions will be proofread by the Engineering Content Services team.
The CPU scaling test now checks the content of /sys/devices/system/cpu/cpu<n>/cpufreq/scaling_available_frequencies file.