On 1/23/22 02:35, Wei Yang wrote:
> To make node order in round-robin in the same distance group, we add a
> penalty to the first node we got in each round.
>
> To get a round-robin order in the same distance group, we don't need to
> decrease the penalty since:
>
> * find_next_best_node() always iterates node in the same order
> * distance matters more then penalty in find_next_best_node()
> * in nodes with the same distance, the first one would be picked up
>
> So it is fine to increase same penalty when we get the first node in the
> same distance group.
With that logic I'm not even sure if we need nr_online_nodes as penalty or
it could be just 1. Would you know?
>
> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
> ---
> mm/page_alloc.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index c5952749ad40..f27afd517652 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6245,13 +6245,12 @@ static void build_thisnode_zonelists(pg_data_t *pgdat)
> static void build_zonelists(pg_data_t *pgdat)
> {
> static int node_order[MAX_NUMNODES];
> - int node, load, nr_nodes = 0;
> + int node, nr_nodes = 0;
> nodemask_t used_mask = NODE_MASK_NONE;
> int local_node, prev_node;
>
> /* NUMA-aware ordering of nodes */
> local_node = pgdat->node_id;
> - load = nr_online_nodes;
> prev_node = local_node;
>
> memset(node_order, 0, sizeof(node_order));
> @@ -6263,11 +6262,10 @@ static void build_zonelists(pg_data_t *pgdat)
> */
> if (node_distance(local_node, node) !=
> node_distance(local_node, prev_node))
> - node_load[node] += load;
> + node_load[node] += nr_online_nodes;
>
> node_order[nr_nodes++] = node;
> prev_node = node;
> - load--;
> }
>
> build_zonelists_in_node_order(pgdat, node_order, nr_nodes);
