Provide CPU metrics in MHz

[cgthayer]

https://www.nomadproject.io/docs/operations/metrics

Please add nomad.client.allocs.cpu.total_mhz

The metric nomad.client.allocs.cpu.total_ticks is in ticks, but there's no metric for MHz used (although there's one for MHz allocated) making it hard to relate it to the resources in the *.nomad file's resource stanza.

Also the doc page doesn't specify if the Percentage values are 0~100 or 0~1.0 based, so that's also not useful.

[isabeldepapel]

Hi @cgthayer! Thanks for bringing this up. We've talked about adding a total_cpu metric in MHz before, so we'll look at trying to get this in. In the meantime, we've generally found that cpu ticks are equal to 100 Hz. That won't always be true so it's an imperfect workaround.

Also the doc page doesn't specify if the Percentage values are 0100 or 01.0 based, so that's also not useful.

Thanks for pointing this out. For what it's worth, the percentage values are 100 based (for example: 92.92929077148438). If you have time to do a pull request to improve our metrics documentation to make that clear, that would be amazing. Otherwise, we'll look at fixing that up ourselves when we have the chance.