On Mon, 2010-03-29 at 22:57 +0800, Bob Liu wrote:
> In current do_migrate_pages(),if from_nodes and to_nodes have some
> intersect nodes,pages in these intersect nodes will also be
> migrated.
> eg. Assume that, from_nodes: 1,2,3,4 to_nodes: 2,3,4,5. Then these
> migrates will happen:
> migrate_pages(4,5);
> migrate_pages(3,4);
> migrate_pages(2,3);
> migrate_pages(1,2);
>
> But the user just want all pages in from_nodes move to to_nodes,
> only migrate(1,2)(ignore the intersect nodes.) can satisfied
> the user's request.
>
> I amn't sure what's migrate_page's semantic.
> Hoping for your suggestions.
I believe that the current code matches the intended semantics. I can't
find a man pages for the migrate_pages() system call, but the
migratepages(8) man page says:
"If multiple nodes are specified for from-nodes or to-nodes then an
attempt is made to preserve the relative location of each page in each
nodeset."
If one just wanted to move all task pages from node 1 to 2, one would
specify:
to_nodes: 1
from_nodes: 2
Christoph L may have more to say. I believe he wrote migrate_pages()
and that very interesting remapping function.
Lee
>
> Signed-off-by: Bob Liu <lliubbo@xxxxxxxxx>
> ---
> mm/mempolicy.c | 7 ++-----
> 1 files changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 08f40a2..c6dd931 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -922,7 +922,7 @@ int do_migrate_pages(struct mm_struct *mm,
> * moved to an empty node, then there is nothing left worth migrating.
> */
>
> - tmp = *from_nodes;
> + nodes_andnot(tmp, *from_nodes, *to_nodes);
> while (!nodes_empty(tmp)) {
> int s,d;
> int source = -1;
> @@ -935,10 +935,7 @@ int do_migrate_pages(struct mm_struct *mm,
>
> source = s; /* Node moved. Memorize */
> dest = d;
> -
> - /* dest not in remaining from nodes? */
> - if (!node_isset(dest, tmp))
> - break;
> + break;
> }
> if (source == -1)
> break;
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