Subject: Re: [PATCH v5 2/6] powerpc/pseries: rename distance_ref_points_depth to max_associativity_domain_index

From: David Gibson <[email-masked]>
Date: Thu, 22 Jul 2021 11:19:12 +1000

On Thu, Jul 22, 2021 at 10:59:09AM +1000, David Gibson wrote:
> On Mon, Jun 28, 2021 at 08:41:13PM +0530, Aneesh Kumar K.V wrote:
> > No functional change in this patch
> > 
> > Signed-off-by: Aneesh Kumar K.V <[email-masked]>
> 
> Reviewed-by: David Gibson <[email-masked]>

No... wait, I take that back.  This change makes the code *more*
confusing.

"distance_ref_points_depth" is accurate - it's the length of the
distance_ref_points array.

"max_associativity_domain_index" is not.  That implies it's the
maximum value that a domain index can have - which it isn't.  You
could have 15 entries in every associativity array, but if only 2 of
them are referenced in distance_ref_points, then
"max_associativity_domain_index" would only be 2.

> 
> > ---
> >  arch/powerpc/mm/numa.c | 20 ++++++++++----------
> >  1 file changed, 10 insertions(+), 10 deletions(-)
> > 
> > diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> > index 8365b298ec48..132813dd1a6c 100644
> > --- a/arch/powerpc/mm/numa.c
> > +++ b/arch/powerpc/mm/numa.c
> > @@ -56,7 +56,7 @@ static int n_mem_addr_cells, n_mem_size_cells;
> >  static int form1_affinity;
> >  
> >  #define MAX_DISTANCE_REF_POINTS 4
> > -static int distance_ref_points_depth;
> > +static int max_associativity_domain_index;
> >  static const __be32 *distance_ref_points;
> >  static int distance_lookup_table[MAX_NUMNODES][MAX_DISTANCE_REF_POINTS];
> >  
> > @@ -169,7 +169,7 @@ int cpu_distance(__be32 *cpu1_assoc, __be32 *cpu2_assoc)
> >  
> >  	int i, index;
> >  
> > -	for (i = 0; i < distance_ref_points_depth; i++) {
> > +	for (i = 0; i < max_associativity_domain_index; i++) {
> >  		index = be32_to_cpu(distance_ref_points[i]);
> >  		if (cpu1_assoc[index] == cpu2_assoc[index])
> >  			break;
> > @@ -193,7 +193,7 @@ int __node_distance(int a, int b)
> >  	if (!form1_affinity)
> >  		return ((a == b) ? LOCAL_DISTANCE : REMOTE_DISTANCE);
> >  
> > -	for (i = 0; i < distance_ref_points_depth; i++) {
> > +	for (i = 0; i < max_associativity_domain_index; i++) {
> >  		if (distance_lookup_table[a][i] == distance_lookup_table[b][i])
> >  			break;
> >  
> > @@ -213,7 +213,7 @@ static void initialize_distance_lookup_table(int nid,
> >  	if (!form1_affinity)
> >  		return;
> >  
> > -	for (i = 0; i < distance_ref_points_depth; i++) {
> > +	for (i = 0; i < max_associativity_domain_index; i++) {
> >  		const __be32 *entry;
> >  
> >  		entry = &associativity[be32_to_cpu(distance_ref_points[i]) - 1];
> > @@ -240,7 +240,7 @@ static int associativity_to_nid(const __be32 *associativity)
> >  		nid = NUMA_NO_NODE;
> >  
> >  	if (nid > 0 &&
> > -		of_read_number(associativity, 1) >= distance_ref_points_depth) {
> > +		of_read_number(associativity, 1) >= max_associativity_domain_index) {
> >  		/*
> >  		 * Skip the length field and send start of associativity array
> >  		 */
> > @@ -310,14 +310,14 @@ static int __init find_primary_domain_index(void)
> >  	 */
> >  	distance_ref_points = of_get_property(root,
> >  					"ibm,associativity-reference-points",
> > -					&distance_ref_points_depth);
> > +					&max_associativity_domain_index);
> >  
> >  	if (!distance_ref_points) {
> >  		dbg("NUMA: ibm,associativity-reference-points not found.\n");
> >  		goto err;
> >  	}
> >  
> > -	distance_ref_points_depth /= sizeof(int);
> > +	max_associativity_domain_index /= sizeof(int);
> >  
> >  	if (firmware_has_feature(FW_FEATURE_OPAL) ||
> >  	    firmware_has_feature(FW_FEATURE_TYPE1_AFFINITY)) {
> > @@ -328,7 +328,7 @@ static int __init find_primary_domain_index(void)
> >  	if (form1_affinity) {
> >  		index = of_read_number(distance_ref_points, 1);
> >  	} else {
> > -		if (distance_ref_points_depth < 2) {
> > +		if (max_associativity_domain_index < 2) {
> >  			printk(KERN_WARNING "NUMA: "
> >  				"short ibm,associativity-reference-points\n");
> >  			goto err;
> > @@ -341,10 +341,10 @@ static int __init find_primary_domain_index(void)
> >  	 * Warn and cap if the hardware supports more than
> >  	 * MAX_DISTANCE_REF_POINTS domains.
> >  	 */
> > -	if (distance_ref_points_depth > MAX_DISTANCE_REF_POINTS) {
> > +	if (max_associativity_domain_index > MAX_DISTANCE_REF_POINTS) {
> >  		printk(KERN_WARNING "NUMA: distance array capped at "
> >  			"%d entries\n", MAX_DISTANCE_REF_POINTS);
> > -		distance_ref_points_depth = MAX_DISTANCE_REF_POINTS;
> > +		max_associativity_domain_index = MAX_DISTANCE_REF_POINTS;
> >  	}
> >  
> >  	of_node_put(root);
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson