Re: [PATCH] mm/migrate: correct thp migration stats.

[Daniel Jordan]

On Thu, Sep 17, 2020 at 04:27:29PM -0400, Zi Yan wrote:
> From: Zi Yan <z...@nvidia.com>
> 
> PageTransHuge returns true for both thp and hugetlb, so thp stats was
> counting both thp and hugetlb migrations. Exclude hugetlb migration by
> setting is_thp variable right.

Yeah, shoot.

> Fixes: 1a5bae25e3cf ("mm/vmstat: add events for THP migration without split")
> Signed-off-by: Zi Yan <z...@nvidia.com>

Reviewed-by: Daniel Jordan <daniel.m.jor...@oracle.com>

If you wanted, you could also do this.

diff --git a/mm/migrate.c b/mm/migrate.c
index d1ad964165e5..6bc9559afc70 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1471,7 +1471,7 @@ int migrate_pages(struct list_head *from, new_page_t 
get_new_page,
                                 * we encounter them after the rest of the list
                                 * is processed.
                                 */
-                               if (PageTransHuge(page) && !PageHuge(page)) {
+                               if (is_thp) {
                                        lock_page(page);
                                        rc = split_huge_page_to_list(page, 
from);
                                        unlock_page(page);
@@ -1480,8 +1480,7 @@ int migrate_pages(struct list_head *from, new_page_t 
get_new_page,
                                                nr_thp_split++;
                                                goto retry;
                                        }
-                               }
-                               if (is_thp) {
+
                                        nr_thp_failed++;
                                        nr_failed += nr_subpages;
                                        goto out;