'acpi=ht' in RHEL 6.9 and above detects only one CPU.

Solution Verified - Updated -

Issue

  • Appending acpi=ht in GRUB for kernels 2.6.32-696.el6 and above in any multi CPU environment brings up only one CPU.
  • dmesg detects a single CPU.
SMP: Allowing 1 CPUs, 0 hotplug CPUs
...
Brought up 1 CPUs

Environment

  • Red Hat Enterprise Linux 6
  • Kernel versions 2.6.32-696.el6 and above.

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