linux-kernel - Re: [PATCH -mm V2] do_migrate_pages() calls migrate_to_node() even if task is already on a correct node

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Date:	Tue, 24 Apr 2012 16:08:11 -0400
From:	Larry Woodman <lwoodman@...hat.com>
To:	Christoph Lameter <cl@...ux.com>
CC:	KOSAKI Motohiro <kosaki.motohiro@...il.com>, linux-mm@...ck.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Motohiro Kosaki <mkosaki@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH -mm V2] do_migrate_pages() calls migrate_to_node() even
 if task is already on a correct node

On 04/24/2012 02:17 PM, Christoph Lameter wrote:
> On Tue, 24 Apr 2012, Larry Woodman wrote:
>
>> How does this look:
>
> Could you please send the patches inline? Its difficult to quote the
> attachment.
>

Sorry all of these email clients are different.


diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index f563fa3..b76b49a 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1012,6 +1012,24 @@ 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/there are
+                        * a different number of source and destination 
nodes,
+                        * never move memory out of a source node that 
is also
+                        * a destination node.
+                        *
+                        * Example: [2,3,4] -> [3,4,5] moves everything.
+                        *          [0-7] - > [3,4,5] moves only 0,1,2,6,7.
+                        */
+
+                       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;

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