Re: Support for more than 256 CPU cores

On Sun, May 7, 2023, 3:51 PM Moin Rahman <bofh@freebsd.org> wrote:

>
>
> > On May 5, 2023, at 3:38 PM, Ed Maste <emaste@freebsd.org> wrote:
> >
> > FreeBSD supports up to 256 CPU cores in the default kernel configuration
> > (on Tier-1 architectures).  Systems with more than 256 cores are
> > available now, and will become increasingly common over FreeBSD 14’s
> > lifetime.  The FreeBSD Foundation is supporting the effort to increase
> > MAXCPU, and PR269572[1] is open to track tasks and changes.
> >
> > As a project we have scalability work ahead of us to make best use of
> > high core count machines, but at a minimum we should be able to boot a
> > GENERIC kernel on such systems, and have an ABI for the FreeBSD 14
> > release that supports such a configuration.
> >
> > Some changes have already been committed in support of increased MAXCPU,
> > including increasing MAX_APIC_ID (commit c8113dad7ed4) and a number of
> > changes to reduce bloat (such as commits 42f722e721cd, e72f7ed43eef,
> > 78cfa762ebf2 and 74ac712f72cf).
> >
> > The next step is to increase the maximum cpuset size for userland.
> > I have this change open in review D39941[2] and an exp-run request in
> > PR271213[3].  Following that the kernel change for increasing MAXCPU is
> > in D36838[4].
> >
> > Additional work on bloat reduction will continue after this change, and
> > looking forward FreeBSD is going to need ongoing effort from the
> > community and the FreeBSD Foundation to continue improving scalability.
> >
> > [1] https://bugs.freebsd.org/269572
> > [2] https://reviews.freebsd.org/D39941
> > [3] https://bugs.freebsd.org/271213
> > [4] https://reviews.freebsd.org/D36838
> >
>
> By any chance will this be merged into 13?
>

Nope. It breaks too many kernel KBIs that are exposed to at least some
modules.

Warner

>
> Kind regards,
> Moin
>