Subject: Re: [RFC][PATCH] powerpc: respect how command line nr_cpus is set

From: Benjamin Herrenschmidt <[email-masked]>
Date: Thu, 05 May 2011 12:25:02 +1000

On Wed, 2011-05-04 at 15:17 -0500, Kumar Gala wrote:
> We should utilize nr_cpus as the max # of CPUs that we can have present
> instead of NR_CPUS.  This way we actually respect how nr_cpus is set on
> the command line rather than ignoring it.
> 
> Signed-off-by: Kumar Gala <[email-masked]>
> ---
> I think this is what we should be doing, but would like someone else to take
> a look.

The main question I have is should max_cpus absolutely limit the number
of possible CPUs or should it limit the number that get automatically
onlined at boot, potentially letting us bring the rest online later on ?

Cheers,
Ben.

> - k
> 
>  arch/powerpc/kernel/setup-common.c |   10 +++++-----
>  1 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
> index 21f30cb..fedf813 100644
> --- a/arch/powerpc/kernel/setup-common.c
> +++ b/arch/powerpc/kernel/setup-common.c
> @@ -424,7 +424,7 @@ void __init smp_setup_cpu_maps(void)
>  
>  	DBG("smp_setup_cpu_maps()\n");
>  
> -	while ((dn = of_find_node_by_type(dn, "cpu")) && cpu < NR_CPUS) {
> +	while ((dn = of_find_node_by_type(dn, "cpu")) && cpu < nr_cpu_ids) {
>  		const int *intserv;
>  		int j, len;
>  
> @@ -443,7 +443,7 @@ void __init smp_setup_cpu_maps(void)
>  				intserv = &cpu;	/* assume logical == phys */
>  		}
>  
> -		for (j = 0; j < nthreads && cpu < NR_CPUS; j++) {
> +		for (j = 0; j < nthreads && cpu < nr_cpu_ids; j++) {
>  			DBG("    thread %d -> cpu %d (hard id %d)\n",
>  			    j, cpu, intserv[j]);
>  			set_cpu_present(cpu, true);
> @@ -483,12 +483,12 @@ void __init smp_setup_cpu_maps(void)
>  		if (cpu_has_feature(CPU_FTR_SMT))
>  			maxcpus *= nthreads;
>  
> -		if (maxcpus > NR_CPUS) {
> +		if (maxcpus > nr_cpu_ids) {
>  			printk(KERN_WARNING
>  			       "Partition configured for %d cpus, "
>  			       "operating system maximum is %d.\n",
> -			       maxcpus, NR_CPUS);
> -			maxcpus = NR_CPUS;
> +			       maxcpus, nr_cpu_ids);
> +			maxcpus = nr_cpu_ids;
>  		} else
>  			printk(KERN_INFO "Partition configured for %d cpus.\n",
>  			       maxcpus);