Parallel CPU Bring-Up Poised For Linux 6.5

Months in the making have been the patches for x86_64 parallel CPU boot support to allow secondary CPU cores to be booted in parallel for shortening Linux kernel boot times. Over time the Linux parallel CPU bring-up patches have gone through many revisions while it looks like this work is now positioned for introduction with the Linux 6.5 kernel later this summer.

As good news for high core count Intel Xeon and AMD EPYC processors as well as higher-core HEDT processors too, the parallel CPU bring-up patches have been queued into the TIP/TIP.GIT repository ahead of the Linux 6.5 merge window opening up around early July.

The parallel CPU bring-up patches were most recently tackled by longtime kernel developer Thomas Gleixner. As of yesterday all the parallel bring-up patches were queued into TIP's smp/core branch. With these patches now part of a TIP branch, barring any last minute issues from being uncovered or objections from Linus Torvalds, the patches in turn should be submitted as part of the next merge window that will be Linux 6.5.

This parallel bring-up support will help with kernel boot times on high core count systems, especially beneficial for large core count servers that may Kexec into new kernel versions for security/maintenance reasons and where minimizing system downtime is critical. Many hyperscalers and other large deployers rely on Kexec'ing the kernel to reduce system downtime during reboots while these patches will also help from cold boots, albeit the time saved is minimal compared to the lengthy POST'ing process with memory training on today's high-end servers.

Ahead of the next kernel cycle, these patches are in tip.git's smp/core branch.