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

[KOSAKI Motohiro]

(3/29/12 2:00 PM), Larry Woodman wrote:
> 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???
>
>
> 		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.


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