On Tue 07-07-20 16:44:49, Joonsoo Kim wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
>
> To calculate the correct node to migrate the page for hotplug, we need
> to check node id of the page. Wrapper for alloc_migration_target() exists
> for this purpose.
>
> However, Vlastimil informs that all migration source pages come from
> a single node. In this case, we don't need to check the node id for each
> page and we don't need to re-set the target nodemask for each page by
> using the wrapper. Set up the migration_target_control once and use it for
> all pages.
yes, memory offlining only operates on a single zone. Have a look at
test_pages_in_a_zone().
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> mm/memory_hotplug.c | 46 ++++++++++++++++++++++------------------------
> 1 file changed, 22 insertions(+), 24 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 86bc2ad..269e8ca 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1265,27 +1265,6 @@ static int scan_movable_pages(unsigned long start, unsigned long end,
> return 0;
> }
>
> -static struct page *new_node_page(struct page *page, unsigned long private)
> -{
> - nodemask_t nmask = node_states[N_MEMORY];
> - struct migration_target_control mtc = {
> - .nid = page_to_nid(page),
> - .nmask = &nmask,
> - .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
> - };
> -
> - /*
> - * try to allocate from a different node but reuse this node if there
> - * are no other online nodes to be used (e.g. we are offlining a part
> - * of the only existing node)
> - */
> - node_clear(mtc.nid, *mtc.nmask);
> - if (nodes_empty(*mtc.nmask))
> - node_set(mtc.nid, *mtc.nmask);
> -
> - return alloc_migration_target(page, (unsigned long)&mtc);
> -}
> -
> static int
> do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
> {
> @@ -1345,9 +1324,28 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
> put_page(page);
> }
> if (!list_empty(&source)) {
> - /* Allocate a new page from the nearest neighbor node */
> - ret = migrate_pages(&source, new_node_page, NULL, 0,
> - MIGRATE_SYNC, MR_MEMORY_HOTPLUG);
> + nodemask_t nmask = node_states[N_MEMORY];
> + struct migration_target_control mtc = {
> + .nmask = &nmask,
> + .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL,
> + };
> +
> + /*
> + * We have checked that migration range is on a single zone so
> + * we can use the nid of the first page to all the others.
> + */
> + mtc.nid = page_to_nid(list_first_entry(&source, struct page, lru));
> +
> + /*
> + * try to allocate from a different node but reuse this node
> + * if there are no other online nodes to be used (e.g. we are
> + * offlining a part of the only existing node)
> + */
> + node_clear(mtc.nid, *mtc.nmask);
> + if (nodes_empty(*mtc.nmask))
> + node_set(mtc.nid, *mtc.nmask);
> + ret = migrate_pages(&source, alloc_migration_target, NULL,
> + (unsigned long)&mtc, MIGRATE_SYNC, MR_MEMORY_HOTPLUG);
> if (ret) {
> list_for_each_entry(page, &source, lru) {
> pr_warn("migrating pfn %lx failed ret:%d ",
> --
> 2.7.4
>
--
Michal Hocko
SUSE Labs
