From: Wei Yang Subject: mm/page_alloc: adding same penalty is enough to get round-robin order 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. Since we just increase a constance of 1 to node penalty, it is not necessary to multiply MAX_NODE_LOAD for preference. Link: https://lkml.kernel.org/r/20220123013537.20491-1-richard.weiyang@gmail.com Signed-off-by: Wei Yang Acked-by: Vlastimil Babka Acked-by: David Hildenbrand Acked-by: Oscar Salvador Cc: David Rientjes Cc: KAMEZAWA Hiroyuki Cc: Krupa Ramakrishnan Cc: Michal Hocko Signed-off-by: Andrew Morton --- mm/page_alloc.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) --- a/mm/page_alloc.c~mm-page_alloc-add-same-penalty-is-enough-to-get-round-robin-order +++ a/mm/page_alloc.c @@ -6286,13 +6286,12 @@ static void build_thisnode_zonelists(pg_ 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)); @@ -6304,11 +6303,10 @@ static void build_zonelists(pg_data_t *p */ 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); _