Re: [PATCH -mm] do_migrate_pages() calls migrate_to_node() even if task is already on a correct node

[Larry Woodman <lwoodman@redhat.com>]

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On 03/22/2012 03:30 PM, Christoph Lameter wrote:
> On Thu, 22 Mar 2012, Larry Woodman wrote:
>
>>> Application may manage their locality given a range of nodes and each of
>>> the x .. x+n nodes has their particular purpose.
>> So to be clear on this, in that case the intention would be move 3 to 4, 4 to
>> 5 and 5 to 6
>> to keep the node ordering the same?
> Yup. Have a look at do_migrate_pages and the descrition in the comment by
> there by Paul Jackson.
>
>
Christoph and others what do you think about this???



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diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 47296fe..6c189fa 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1012,6 +1012,16 @@ int do_migrate_pages(struct mm_struct *mm,
 		int dest = 0;
 
 		for_each_node_mask(s, tmp) {
+
+			/* IFF there is an equal number of source and
+			 * destination nodes, maintain relative node distance
+			 * even when source and destination nodes overlap.
+			 * However, when the node weight is unequal, never move
+			 * memory out of any destination nodes */
+			if ((nodes_weight(*from_nodes) != nodes_weight(*to_nodes)) && 
+						(node_isset(s, *to_nodes)))
+				continue;
+
 			d = node_remap(s, *from_nodes, *to_nodes);
 			if (s == d)
 				continue;