As Zi Yan pointed out, the syscall move_pages() can return a non-migrated
number larger than the number of pages the users tried to migrate, when a
THP page is failed to migrate. This is confusing for users.
Since other migration scenarios do not care about the actual non-migrated
number of pages except the memory compaction migration which will fix in
following patch. Thus we can change the return value to return the number
of {normal page, THP, hugetlb} instead to avoid this issue, and the number
of THP splits will be considered as the number of non-migrated THP, no matter
how many subpages of the THP are migrated successfully. Meanwhile we should
still keep the migration counters using the number of normal pages.
Co-developed-by: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 63 +++++++++++++++++++++++++++++++++++++++++++++---------------
1 file changed, 47 insertions(+), 16 deletions(-)
diff --git a/mm/migrate.c b/mm/migrate.c
index a11e948..9aafdab 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1428,7 +1428,7 @@ static inline int try_split_thp(struct page *page, struct page **page2,
* @mode: The migration mode that specifies the constraints for
* page migration, if any.
* @reason: The reason for page migration.
- * @ret_succeeded: Set to the number of pages migrated successfully if
+ * @ret_succeeded: Set to the number of normal pages migrated successfully if
* the caller passes a non-NULL pointer.
*
* The function returns after 10 attempts or if no pages are movable any more
@@ -1436,7 +1436,9 @@ static inline int try_split_thp(struct page *page, struct page **page2,
* It is caller's responsibility to call putback_movable_pages() to return pages
* to the LRU or free list only if ret != 0.
*
- * Returns the number of pages that were not migrated, or an error code.
+ * Returns the number of {normal page, THP} that were not migrated, or an error code.
+ * The number of THP splits will be considered as the number of non-migrated THP,
+ * no matter how many subpages of the THP are migrated successfully.
*/
int migrate_pages(struct list_head *from, new_page_t get_new_page,
free_page_t put_new_page, unsigned long private,
@@ -1445,6 +1447,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
int retry = 1;
int thp_retry = 1;
int nr_failed = 0;
+ int nr_failed_pages = 0;
int nr_succeeded = 0;
int nr_thp_succeeded = 0;
int nr_thp_failed = 0;
@@ -1456,13 +1459,16 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
int swapwrite = current->flags & PF_SWAPWRITE;
int rc, nr_subpages;
LIST_HEAD(ret_pages);
+ LIST_HEAD(thp_split_pages);
bool nosplit = (reason == MR_NUMA_MISPLACED);
+ bool no_subpage_counting = false;
trace_mm_migrate_pages_start(mode, reason);
if (!swapwrite)
current->flags |= PF_SWAPWRITE;
+thp_subpage_migration:
for (pass = 0; pass < 10 && (retry || thp_retry); pass++) {
retry = 0;
thp_retry = 0;
@@ -1511,18 +1517,20 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
case -ENOSYS:
/* THP migration is unsupported */
if (is_thp) {
- if (!try_split_thp(page, &page2, from)) {
+ nr_thp_failed++;
+ if (!try_split_thp(page, &page2, &thp_split_pages)) {
