Re: bhyve vCPU limit

> On Wed 2021-12-01 11:13 AM MST -0700, <olevole@olevole.ru> wrote:
> 
> > As far as I remember, it is not enough to simply change one parameter
> > in .h file: https://bhyvecon.org/bhyveconOttawa2019-Rodney.pdf
> 
> I may be wrong but my understanding is that prior to the work described 
> in that presentation, some of the bhyve data structures were such that 
> vCPU counts above 21 would not be possible. That work resolved that but 
> the VM_MAXCPU value was left at 16.

That is correct, the work described was committed, and raised
the usable limit of VM_MAXCPU well into the 200 range.  Note
that raising this ABOVE the physcial core count is neither
desirable or performant.

> 
> On my system, I'm sure that all I did was edit vmm.h, make buildworld, 
> and make installworld.

Yes, that would do all that is needed.  There well be some ipi interrupt
stats that dont work right, but that is the only known issue.

> 
> I did some other stuff while sort of stumbling toward that eventual 
> solution, described here:
> 
> <https://lists.freebsd.org/pipermail/freebsd-virtualization/2021-May/009508.html>
> 
> Once what I was doing wrong was pointed out, it seemed to me that after 
> editing that file, "make buildworld" and "make installworld" would be 
> the simplest way to do things, so that's what I did. It's been working 
> fine for six months or so.

In this message of that thread:
  https://lists.freebsd.org/pipermail/freebsd-virtualization/2021-May/009510.html

I correct the error that caused your procedure to not work and
explain why it did not work (compiled with old /usr/include file).

-- 
Rod Grimes                                                 rgrimes@freebsd.org