mm: page_alloc: do not cache reclaim distances

pgdat->reclaim_nodes tracks if a remote node is allowed to be reclaimed
by zone_reclaim due to its distance.  As it is expected that
zone_reclaim_mode will be rarely enabled it is unreasonable for all
machines to take a penalty.  Fortunately, the zone_reclaim_mode() path
is already slow and it is the path that takes the hit.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mmzone.h

@@ -763,7 +763,6 @@ typedef struct pglist_data {
 	unsigned long node_spanned_pages; /* total size of physical page
 					     range, including holes */
 	int node_id;
-	nodemask_t reclaim_nodes;	/* Nodes allowed to reclaim from */
 	wait_queue_head_t kswapd_wait;
 	wait_queue_head_t pfmemalloc_wait;
 	struct task_struct *kswapd;	/* Protected by lock_memory_hotplug() */

mm/page_alloc.c

@@ -1850,16 +1850,8 @@ static bool zone_local(struct zone *local_zone, struct zone *zone)
 
 static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
 {
-	return node_isset(local_zone->node, zone->zone_pgdat->reclaim_nodes);
-}
-
-static void __paginginit init_zone_allows_reclaim(int nid)
-{
-	int i;
-
-	for_each_node_state(i, N_MEMORY)
-		if (node_distance(nid, i) <= RECLAIM_DISTANCE)
-			node_set(i, NODE_DATA(nid)->reclaim_nodes);
+	return node_distance(zone_to_nid(local_zone), zone_to_nid(zone)) <
+				RECLAIM_DISTANCE;
 }
 
 #else	/* CONFIG_NUMA */
@@ -1893,9 +1885,6 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
 	return true;
 }
 
-static inline void init_zone_allows_reclaim(int nid)
-{
-}
 #endif	/* CONFIG_NUMA */
 
 /*
@@ -4933,8 +4922,6 @@ void __paginginit free_area_init_node(int nid, unsigned long *zones_size,
 
 	pgdat->node_id = nid;
 	pgdat->node_start_pfn = node_start_pfn;
-	if (node_state(nid, N_MEMORY))
-		init_zone_allows_reclaim(nid);
 #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
 	get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
 #endif