[Bug 222916] [bhyve] Debian guest kernel panics with message "CPU#0 stuck for Xs!"

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=222916

--- Comment #5 from karihre at gmail.com ---
Thanks for that tip. I reduced the ARC size with sysctl and confirmed it to be
20GB with zfs-info.

Thinking back to the 4 guest / 4 host cpus. Lets say the collection of guests
consume 4 cpus and four tasks on the host consume 4 cpus (totaling a load
average of 8), does the host system scheduler not shuffle tasks around like it
would if I were running 8 cpu intensive processes on the host? Or does the
interaction between bhyve and the host scheduler somehow result in the virtual
cpus being set aside for tens of seconds?

I guess I'm just trying to understand, I would think one of the main
motivations for using a hypervisor is exactly over-subscribing cpu cores as you
may have guests with "bursty" load behavior, so on average your total
guests+host load is less than the number of cpus, but surely you can divide the
cpu time in a "fair" manner when the system is overloaded.

Memory I would think is a little trickyer, there it makes sense to make sure
the host system consumption + guest consumption never exceeds the total host
memory.

Anyhow, just trying to make sense of this, there doesn't seem to be too much
information available online on these topics, or perhaps I'm looking in all the
wrong places.

Thank you,
Kari

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