Re: [PATCH 1/5] x86/smpboot: Add the missing description of possible_cpus

[Dou Liyang]

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.

> 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.
>