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

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Message-ID: <4F75EDC3.7050104@redhat.com>
Date:	Fri, 30 Mar 2012 13:30:43 -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>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Motohiro Kosaki <mkosaki@...hat.com>
Subject: Re: [PATCH -mm] do_migrate_pages() calls migrate_to_node() even if
 task is already on a correct node

On 03/30/2012 12:15 PM, Christoph Lameter wrote:
> On Thu, 29 Mar 2012, KOSAKI Motohiro wrote:
>
>>> 		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;
>> I'm confused. Could you please explain why you choose nodes_weight()? On my
>> first impression,
>> it seems almostly unrelated factor.
> Isnt this the original code by Paul?
No, I added the test to see if the source and destination has the same 
number of nodes.
>   I would think that the 1-1 movement
> is only useful to do if the number of nodes in both the destination and
> the source is the same.
Agreed, thats exactly what this patch does.  are you OK with this change 
then???

Larry


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