On Wed 19-02-14 08:33:45, Nishanth Aravamudan wrote:

On 19.02.2014 [08:24:38 -0800], Nishanth Aravamudan wrote:

quoted

On 18.02.2014 [17:43:38 -0800], David Rientjes wrote:

quoted

On Tue, 18 Feb 2014, Nishanth Aravamudan wrote:

quoted

How about the following?

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5de4337..1a0eced 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c

@@ -1854,7 +1854,8 @@ static void __paginginit init_zone_allows_reclaim(int nid)
        int i;
 
        for_each_online_node(i)
-               if (node_distance(nid, i) <= RECLAIM_DISTANCE)
+               if (node_distance(nid, i) <= RECLAIM_DISTANCE ||
+                                       !NODE_DATA(i)->node_present_pages)
                        node_set(i, NODE_DATA(nid)->reclaim_nodes);
                else
                        zone_reclaim_mode = 1;

 [ I changed the above from NODE_DATA(nid) -> NODE_DATA(i) as you caught 
   so we're looking at the right code. ]

That can't be right, it would allow reclaiming from a memoryless node.  I 
think what you want is

Gah, you're right.

quoted

	for_each_online_node(i) {
		if (!node_present_pages(i))
			continue;
		if (node_distance(nid, i) <= RECLAIM_DISTANCE) {
			node_set(i, NODE_DATA(nid)->reclaim_nodes);
			continue;
		}
		/* Always try to reclaim locally */
		zone_reclaim_mode = 1;
	}

but we really should be able to do for_each_node_state(i, N_MEMORY) here 
and memoryless nodes should already be excluded from that mask.

Yep, I found that afterwards, which simplifies the logic. I'll add this
to my series :)

In looking at the code, I am wondering about the following:

init_zone_allows_reclaim() is called for each nid from
free_area_init_node(). Which means that calculate_node_totalpages for
other "later" nids and check_for_memory() [which sets up the N_MEMORY
nodemask] hasn't been called yet.

So, would it make sense to pull up the
                /* Any memory on that node */
                if (pgdat->node_present_pages)
                        node_set_state(nid, N_MEMORY);
                check_for_memory(pgdat, nid);
into free_area_init_node()?

Dunno, but it shouldn't be needed because nodes are set N_MEMORY earlier
in early_calculate_totalpages as mentioned in other email.

-- 
Michal Hocko
SUSE Labs