Understanding CPU and memory usage in Bhyve

[Roman Bogorodskiy]

Hi,

I'm trying to understand how to obtain resource usage information for a
bhyve guest.

For the CPU, there's some info provided by bhyvectl, e.g.:

/usr/sbin/bhyvectl --vm=bhyve --get-stats --cpu=1

in the field 'vcpu total runtime', for example:

vcpu total runtime                              8178870653

Two question about that:

 1. What are the units used here? Looks like it's ticks, so if I want to
 convert this number, to, say, nanoseconds, would it be right to do
 something like:

     X * 1000**3 / kern.clockrate.stathz 

 (X beeing the value returned by bhyvectl and kern.clockrate is a
 sysctl name)?

 2. This value shows only vcpu time, without hypervisor time?

For the memory stats, it's less obvious. Does guest always use an amount
of memory specified at startup with '-m' (i.e. bhyve -m 1G) or it could
use less?

What is the format of bhyvectl --get-{low,high}mem output?

PS I found it a little confusing that bhyvectl displays vcpu0 stats by
default if --cpu is not provided, expected it provide info of all vcpus
in the guest by default. Also, didn't find a way to get a number of
vcpus in a running guest.

Roman Bogorodskiy
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