At 03/21/2018 05:34 PM, Dou Liyang wrote:
Hi Peter,

At 03/21/2018 05:08 PM, Peter Zijlstra wrote:
On Wed, Mar 21, 2018 at 01:33:24PM +0800, Dou Liyang wrote:
How about:

possible_cpus=    [s390,x86_64] Set the number of possible CPUs which
        are determined by the ACPI tables MADT or mptables by
        default. possible_cpus=n : n >= 1 enforces the possible
        number to be 'n'.
        While nr_cpus is also be set: nr_cpus=m, choice the
        minimum one for the number of possible CPUs.

So what is the exact difference between possible_cpus and nr_cpus ? I

the possible_cpus= can reset the number of possible CPUs, even bigger
than 'num_processors + disabled_cpus', But nr_cpus= can't.
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      the maximum number kernel gets from ACPI/mptables, no matter what
number nr_cpus= is, the number of possible CPUs will not bigger than it.


konw maxcpus= limits the number of CPUs we bring up, and possible_cpus
limits the possible_map, but I'm not entirely sure what nr_cpus does
here.


nr_cpus can limited the maximum CPUs that the kernel could support.

Here is a double check in case of using them at the same time, even if I
think just using possible_cpus= is enough. :-)

Thanks,
     dou.




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