On 29 Oct 2021, at 3:42, Baolin Wang wrote:
> Now hugetlb migration is also available for some scenarios, such as
> soft offling or memory compaction. So we should correct the migration
hugetlb migration is available at the time if (PageHuge(page)) branch
is added. I am not sure what is new here.
> stats for hugetlb with using compound_nr() instead of thp_nr_pages()
> to get the number of pages.
nr_failed records the number of pages, not subpages. It is returned to
user space when move_pages() syscall is used. After your change,
if users try to migrate a list of pages including THPs and/or hugetlb
pages and some of THPs and/or hugetlb fail to migrate, move_pages()
will return a number larger than the number of pages the users tried
to migrate. I am not sure this is the change we want. Or at least,
the comment of migrate_pages() and the manpage of move_pages() need
to be changed and linux-api mailing list should be cc’d.
>
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> ---
> mm/migrate.c | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index a11e948..2b45a29 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1475,7 +1475,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
> * during migration.
> */
> is_thp = PageTransHuge(page) && !PageHuge(page);
> - nr_subpages = thp_nr_pages(page);
> + nr_subpages = compound_nr(page);
> cond_resched();
>
> if (PageHuge(page))
> @@ -1540,7 +1540,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
> nr_failed += nr_subpages;
> goto out;
> }
> - nr_failed++;
> + nr_failed += nr_subpages;
> goto out;
> case -EAGAIN:
> if (is_thp) {
> @@ -1550,14 +1550,14 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
> retry++;
> break;
> case MIGRATEPAGE_SUCCESS:
> + nr_succeeded += nr_subpages;
> if (is_thp) {
> nr_thp_succeeded++;
> - nr_succeeded += nr_subpages;
> break;
> }
> - nr_succeeded++;
> break;
> default:
> + nr_failed += nr_subpages;
> /*
> * Permanent failure (-EBUSY, etc.):
> * unlike -EAGAIN case, the failed page is
> @@ -1566,10 +1566,8 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
> */
> if (is_thp) {
> nr_thp_failed++;
> - nr_failed += nr_subpages;
> break;
> }
> - nr_failed++;
> break;
> }
> }
> --
> 1.8.3.1
--
Best Regards,
Yan, Zi
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