Linux Parallel CPU Start-Up Restored For AMD CPUs To Yield Faster Boot Times

The very promising work around parallel CPU bring-up to speed-up Linux kernel boot times with today's high core count servers and HEDT systems has been revised once more. Notable with the v7 patches is re-enabling support for this time-savings boot feature for AMD processors.

This work to bring-up secondary CPU cores in parallel than sequentially as currently done by the Linux kernel has shown to provide significant time savings for initial boot times on x86_64 systems and servers.

The AMD support though for this boot-time savings was disabled over hitting issues with some older AMD platforms. Fortunately, that appears to be all addressed with the updated patches and AMD CPUs are no longer black-listed from this feature. With the v7 patches, the parallel start-up of secondary CPUs is only disabled though if AMD SEV-ES is activated or other certain conditions around X2APIC.

Usama Arif of Bytedance sent out the v7 patches on Tuesday with the work that was started by Amazon's David Woodhouse and Intel/Linutronix's Thomas Gleixner. Aside from working out the AMD support, the v7 patches also have other minor changes.

The v7 patches are still tested to yield around an 85% improvement in boot speed when testing with 128 CPU cores split across two NUMA nodes. Now with AMD support restored, it will be fun to see the start-up improvements when dealing with EPYC 9004 "Genoa" that have up to 96 physical cores per socket or Begamo coming with 128 cores per socket.