Re: [PATCH] add init_start_cpus to config boot cpus -v2

[Andrew Morton <akpm@linux-foundation.org>]

On Sat, 13 Dec 2008 23:28:36 -0800 Yinghai Lu <yinghai@kernel.org> wrote:

> 
> Impact: new command line
> 
> so could select cpus to be started during init stage.

I already knew that :(


> example:
> init_start_cpus=2,4,6
> to start core 0 only on every node or thread 0 or all cores
> 
> init_start_cpus=0
> not start other APs, and later let user to use
>  echo 1 > /sys/devices/cpu/cpu2
> to start them in user space.
> 

But why?  Why is this useful?  Why did you even bother writing the
code?  Who wants this?  For what reason?  What value has it?

This stuff matters.

> +static __initdata cpumask_var_t cpu_init_start_mask;

OK.

I also suggested that this code not be added in init/main.c.  What
happened to that idea?