Re: [PATCH] CONFIG_NR_CPUS, redux

[Helge Hafting <helgehaf@aitel.hist.no>]

Ruth Ivimey-Cook wrote:

> Perhaps it's just because I'm coming in late, but I cannot understand why
> NR_CPUS cannot be as low as 4 by default, for all archs, and then in the
> kernel boot messages, should more be found than is configured for a message is
> emitted to say "reconfigure your kernel", and continue with the number it was
> configured for. I personally only rarely see 2-way boxes, 4-way is pretty
> rare, and anything more must surely count as very specialized.
> 
Why not let the boot process select the highest of two numbers,
the (default-low) NR_CPUS and the number of CPU's detected?

Boot with "too many" cpu's and you still get to use them - you
merely can't hotplug even more.  

Configuring a high NR_CPUS becomes something only hot-pluggers
need to do, or those whose architecture doesn't support
cpu detection in the early boot process.  Those with a fixed
number of detectable CPUs can simply go with a default of 
NR_CPUS=2 no matter what they actually have.

Helge Hafting