Re: [PATCH 7/8] mm/migrate.c: move page on next iteration

Michal Hocko
2020-01-20T10:02:08Z

On Sun 19-01-20 11:06:35, Wei Yang wrote:
> When page is not successfully queued for migration, we would move pages
> on pagelist immediately. Actually, this could be done in the next
> iteration by telling it we need some help.
>
> This patch adds a new variable need_move to be an indication. After
> this, we only need to call move_pages_and_store_status() twice.

No! Not another iterator. There are two and this makes the function
quite hard to follow already. We do not want to add a third one.

> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> ---
> mm/migrate.c | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index aee5aeb082c4..2a857fec65b6 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1610,6 +1610,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
> LIST_HEAD(pagelist);
> int start, i;
> int err = 0, err1;
> + int need_move = 0;
>
> migrate_prep();
>
> @@ -1641,13 +1642,15 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
> if (current_node == NUMA_NO_NODE) {
> current_node = node;
> start = i;
> - } else if (node != current_node) {
> + } else if (node != current_node || need_move) {
> err = move_pages_and_store_status(mm, current_node,
> - &pagelist, status, start, i - start);
> + &pagelist, status, start,
> + i - start - need_move);
> if (err)
> goto out;
> start = i;
> current_node = node;
> + need_move = 0;
> }
>
> /*
> @@ -1662,6 +1665,9 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
> continue;
> }
>
> + /* Ask next iteration to move us */
> + need_move = 1;
> +
> /*
> * Two possible cases for err here:
> * == 0: page is already on the target node, then store
> @@ -1671,17 +1677,11 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
> err = store_status(status, i, err ? : current_node, 1);
> if (err)
> goto out_flush;
> -
> - err = move_pages_and_store_status(mm, current_node, &pagelist,
> - status, start, i - start);
> - if (err)
> - goto out;
> - current_node = NUMA_NO_NODE;
> }
> out_flush:
> /* Make sure we do not overwrite the existing error */
> err1 = move_pages_and_store_status(mm, current_node, &pagelist,
> - status, start, i - start);
> + status, start, i - start - need_move);
> if (err >= 0)
> err = err1;
> out:
> --
> 2.17.1
>

--
Michal Hocko
SUSE Labs