on bhyve statistics

Rodney W. Grimes freebsd-rwg at pdx.rh.CN85.dnsmgr.net
Mon Aug 27 15:20:01 UTC 2018

> Hi list,
> I'm currently looking at getting the libvirt prometheus exporter[1] to
> work with libvirt+bhyve. In its current state this doesn't work because
> at least one of the API calls exposed by libvirt isn't implemented by
> the libvirt bhyve driver - so I started looking at implementing it.
> The first API call in question is virDomainBlockStats[2], which returns
> statistics (number of read and written bytes and ops, respectively).
> Currently, bhyve does not expose any of these statistics. All the stats
> available through bhyvectl --get-stats seem to be coming from the VMM,
> not from the userspace emulation.

That is correct, byhvectl is a diagnostics tool for getting
information from the kernel/vmm module.

> OTOH, I did see that there are *some*
> stats being collected in bhyverun.c (see struct bhyvestats {...}
> stats;). I can't see how these are exposed though -  a grep of /usr/src
> turned up no other uses. Which brings me to the following questions:
> - are the stats in struct bhyvestats {...} stats exposed or used in any
>   non-obvious way?

Not that I am aware of.

> - architecturally, what would be the best ways to get stats out of the
>   user-space emulations? Off of the top of my head, I could think of the
>   following possibilities:
>   - prometheus exporter
>   - having some socket or pipe to request them
>   - DTrace probes
> I wouldn't mind implementing any of the above, and so would like to know
> which of these (or other options) would be the most acceptable, and
> would appreciate some guidance.

I differ to others on what may be the best way to do this.

> CC'ing novel@ for the libvirt side, and grehan@ for the architectural
> bhyve questions.

You should replace @grehan with @jhb, at tychon as Peter has moved on,
and John and Tycho are now the bhyve maintainers.  I was going to
add them, and remove Peter, but I see no cc: anyway, so I am sure
that they are on the virtualization list though.

> Fabian
> [1] https://github.com/kumina/libvirt_exporter
> [2] https://libvirt.org/html/libvirt-libvirt-domain.html#virDomainBlockStats
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Rod Grimes                                                 rgrimes at freebsd.org

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