Messages in this thread | | | Subject | Re: [PATCH 1/5] x86/smpboot: Add the missing description of possible_cpus | From | Dou Liyang <> | Date | Wed, 21 Mar 2018 17:41:45 +0800 |
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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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