Re: [Patch v2 2/2] mm/page_alloc: not necessary to multiply MAX_NODE_LOAD

[David Hildenbrand <david@redhat.com>]

On 08.04.22 04:59, Wei Yang wrote:
> Since we just increase a constance of 1 to node penalty, it is not
> necessary to multiply MAX_NODE_LOAD for preference.
> 
> This patch also remove the definition.
> 
> [vbabka@suse.cz: suggests]
> 
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> CC: Vlastimil Babka <vbabka@suse.cz>
> CC: David Hildenbrand <david@redhat.com>
> CC: Oscar Salvador <osalvador@suse.de>
> ---
>  mm/page_alloc.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 86b6573fbeb5..ca6a127bbc26 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6170,7 +6170,6 @@ int numa_zonelist_order_handler(struct ctl_table *table, int write,
>  }
>  
>  
> -#define MAX_NODE_LOAD (nr_online_nodes)
>  static int node_load[MAX_NUMNODES];
>  
>  /**
> @@ -6217,7 +6216,7 @@ int find_next_best_node(int node, nodemask_t *used_node_mask)
>  			val += PENALTY_FOR_NODE_WITH_CPUS;
>  
>  		/* Slight preference for less loaded node */
> -		val *= (MAX_NODE_LOAD*MAX_NUMNODES);
> +		val *= MAX_NUMNODES;
>  		val += node_load[n];
>  
>  		if (val < min_val) {

I feel like this should be squashed into the previous patch. It has the
same effect of making this code independent of nr_online_nodes. And I
had to scratch my head a couple of times in patch #1 why the change in
patch #1 is fine with thus remaining in place.


Having that said, I consider this code highly unnecessary
over-complicated at first sight. Removing some of the magic most
certainly is very welcome.

This semantics of the global variable node_load[] remains mostly
mysterious for me.

-- 
Thanks,

David / dhildenb