CPU stat for VM %USED is greater than 100%

[CapNeo]

Hi All,

I was running esxtop and found on one of our VM has 120 for %Used.

This VM has one vCPU, not sure how can we have this counter more 100 %.

Any suggestions?

Thanks,

[jrmunday]

Hi CapNeo,

See this blog (Esxtop Guide | Simon Greaves) for details, but the relevant section is below;

Counter normalisation
By default counters are displayed for the group, in group view the counters are cumulative whereas in expanded view, counters are normalised per entity. Because of the cumulative stats, percentage displayed can often exceed 100%. To view expanded stats, press e.

Snapshots
esxtop takes snapshots. Snapshots are every 5 seconds by default. To display a metric it takes two snapshots and makes a comparison of the two to display the difference. The lowest snapshot value is 2 seconds. Metrics such as %USED and %RUN show the CPU occupancy delta between successive snapshots.

Sorry for the straight copy and paste (without further explanation), but I'm about to leg it for my train

Cheers,

Jon

[MKguy]

I was running esxtop and found on one of our VM has 120 for %Used.

This VM has one vCPU, not sure how can we have this counter more 100 %.

Any suggestions?

This can happen even with a single vCPU due to dynamic CPU clocking with Intel Turbo Boost.

This is explained on page 10 of this document: Host Power Management in VMware vSphere 5.5

[...]%USED is the percentage of its nominal speed that the logical CPU has been operating at (with idle time counted as operating at zero speed). So %USED can be greater than 100 if the CPU has been in turbo mode, and it can be less than %UTIL in P-states slower than P0. This phenomenon can also happen when the BIOS is handling power management instead of ESXi. Be careful in interpreting these values when HPM is enabled (BIOS managed or ESXi managed). [...]