Date: Fri, 5 May 2023 09:38:25 -0400 From: Ed Maste <emaste@freebsd.org> To: freebsd-arch <freebsd-arch@freebsd.org>, FreeBSD Current <freebsd-current@freebsd.org> Subject: Support for more than 256 CPU cores Message-ID: <CAPyFy2DODJVhs5o8xddaj7GD8zZfC3g1zm_guWKeCmeE07wn-w@mail.gmail.com>
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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=E2=80=99= 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
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