[RFC PATCH 1/3] mm: migrate: Fix the return value of migrate_pages()
From: Baolin Wang <baolin.wang@linux.alibaba.com>
Date: 2021-11-03 10:51:33
Also in:
lkml
Subsystem:
memory management, memory management - memory policy and migration, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
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, meanwhile we
should still keep the migration counters using the number of normal pages.
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
mm/migrate.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/mm/migrate.c b/mm/migrate.c
index a11e948..00b8922 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 +1436,7 @@ 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. */ int migrate_pages(struct list_head *from, new_page_t get_new_page, free_page_t put_new_page, unsigned long private,
@@ -1445,6 +1445,7 @@ 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;
@@ -1517,7 +1518,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, } nr_thp_failed++; - nr_failed += nr_subpages; + nr_failed_pages += nr_subpages; break; }
@@ -1537,7 +1538,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, } nr_thp_failed++; - nr_failed += nr_subpages; + nr_failed_pages += nr_subpages; goto out; } nr_failed++;
@@ -1566,7 +1567,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, */ if (is_thp) { nr_thp_failed++; - nr_failed += nr_subpages; + nr_failed_pages += nr_subpages; break; } nr_failed++;
@@ -1575,8 +1576,9 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, } } nr_failed += retry + thp_retry; + nr_failed_pages += nr_failed; nr_thp_failed += thp_retry; - rc = nr_failed; + rc = nr_failed + nr_thp_failed; out: /* * Put the permanent failure page back to migration list, they
@@ -1585,11 +1587,11 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, list_splice(&ret_pages, from); count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded); - count_vm_events(PGMIGRATE_FAIL, nr_failed); + count_vm_events(PGMIGRATE_FAIL, nr_failed_pages); count_vm_events(THP_MIGRATION_SUCCESS, nr_thp_succeeded); count_vm_events(THP_MIGRATION_FAIL, nr_thp_failed); count_vm_events(THP_MIGRATION_SPLIT, nr_thp_split); - trace_mm_migrate_pages(nr_succeeded, nr_failed, nr_thp_succeeded, + trace_mm_migrate_pages(nr_succeeded, nr_failed_pages, nr_thp_succeeded, nr_thp_failed, nr_thp_split, mode, reason); if (!swapwrite)
--
1.8.3.1