[Bug 225579] CPU usage in top command not matching with VMWare Host's esxtop command's vCPU output

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=225579

            Bug ID: 225579
           Summary: CPU usage in top command not matching with VMWare
                    Host's esxtop command's vCPU output
           Product: Base System
           Version: 11.0-STABLE
          Hardware: arm64
                OS: Any
            Status: New
          Severity: Affects Many People
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: nirmalanandj at gmail.com

Created attachment 190217
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=190217&action=edit
Schreenshot of top and esxtop with FreeBSD VM 10.3

Hello Experts,

VM: FreeBSD 11.0 Stable [Seen with FreeBSD 10.3 stable and lower version as
well]
Hypervisor : ESX 6.0  (ESXi-6.0.0-20171104001-standard (Build 6921384))

5 vCPUs are allocated for the VM, 10 GB RAM and 20 GB disk. vCPU pinning is
done for the VM.

Test Case: A shell script with the following commands:
dd if=</a_2gb_file> of=<an output file> &
dd if=</a_2gb_file> of=<an output file> &
dd if=</a_2gb_file> of=<an output file> &
dd if=</a_2gb_file> of=<an output file> &
dd if=</a_2gb_file> of=<an output file> &

The top command output and esxtop command output is attached for FreeBSD VM:
Freebsd_VM.jpg
If we compare the vCPU IDLE times, there is a difference of around 60%.

We would like understand why it is happening and fix it as needed.

Few additional notes:
- This issue is seen with XenServer 7.1. So issue is hypervisor agnostic.
- Another data point, we do not observe similar issue with a Ubuntu VM on the
same ESX hypervisor.


Let us know.

Regards,
Nirmal

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