turbostat: missing Skylake Cstates

[Wolf480pl]

• Version of collectd: 5.12.0
• Operating system / distribution: Debian 11
• Kernel version (if applicable): 5.10.0-20-amd64

Beginning of /proc/cpuinfo:

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 94
model name      : Intel(R) Core(TM) i3-6100 CPU @ 3.70GHz

Expected behavior

Turbostat plugin automatically detects, and reports usage for, all Cstates supported by the Intel i3-6100 CPU

Actual behavior

Only thread C0 and C1 are detected.
Eg. write_prometheus output:

# HELP collectd_turbostat_percent write_prometheus plugin: 'turbostat' Type: 'percent', Dstype: 'gauge', Dsname: 'value'
# TYPE collectd_turbostat_percent gauge
collectd_turbostat_percent{turbostat="cpu00",type="c0",instance="redacted"} 0.909267010093825 1687127969866
collectd_turbostat_percent{turbostat="cpu00",type="c1",instance="redacted"} 99.0907329899062 1687127969866
collectd_turbostat_percent{turbostat="cpu01",type="c0",instance="redacted"} 1.02867876108538 1687127969866
collectd_turbostat_percent{turbostat="cpu01",type="c1",instance="redacted"} 98.9713212389146 1687127969866
collectd_turbostat_percent{turbostat="cpu02",type="c0",instance="redacted"} 1.03555693203002 1687127969866
collectd_turbostat_percent{turbostat="cpu02",type="c1",instance="redacted"} 98.96444306797 1687127969866
collectd_turbostat_percent{turbostat="cpu03",type="c0",instance="redacted"} 1.13315045864024 1687127969866
collectd_turbostat_percent{turbostat="cpu03",type="c1",instance="redacted"} 98.8668495413598 1687127969866

I had to set in collectd.conf:

<Plugin turbostat>
  CoreCstates "200" # C3 C6 C7
  PackageCstates "460" # C2 C3 C6 C7 C8
</Plugin>

to get the same package and core Cstates that were reported by powertop(8) and turbostat(8)

Steps to reproduce

• have a machine with Skylake CPU running Debian 11
• install collectd from Debian repos
• enable turbostat plugin in collectd.conf, restart collectd
• observe lack of any package or core cstates

[eero-t]

Thanks for reporting this!

However, PR fixing the issue would be welcome. Otherwise it can take a long time until there's a fix for the issue (there are only few active developers, and a lot of plugins).

[Wolf480pl]

I don't feel competent enough to modify the code that touches MSRs.
If there was a reviewer who was familiar with Intel CPUs enough to be able to check if I'm not doing something dangerous, or applying my fix to too wide a range of CPUs, then I could send a pull request.