The isolcpus= kernel boot option behaves differently when specifying a comma separated list vs. a range

Solution In Progress - Updated -

Issue

  • With the range syntax, isolcpus= fails silently and no CPUs are isolated.
  • With a comma separated list, the kernel isolates the CPUs it is able to isolate and ignores the rest.

Environment

  • The number of CPUs specified in the isolcpus= option on the kernel boot line is greater than the number of CPUs in the system.
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7

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