mm: migrate: don't split THP for misplaced NUMA page

The old behavior didn't split THP if migration is failed due to lack of
memory on the target node.  But the THP migration does split THP, so keep
the old behavior for misplaced NUMA page migration.

Link: https://lkml.kernel.org/r/20210518200801.7413-6-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

diff --git a/mm/migrate.c b/mm/migrate.c
index 485781f294c10810cd54c352f5093631883ea765..04edeff96a0f40e2d292eeaa5597440554d1e346 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1427,6 +1427,7 @@ 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);
+       bool nosplit = (reason == MR_NUMA_MISPLACED);
 
        trace_mm_migrate_pages_start(mode, reason);
 
@@ -1498,8 +1499,9 @@ retry:
                                /*
                                 * When memory is low, don't bother to try to migrate
                                 * other pages, just exit.
+                                * THP NUMA faulting doesn't split THP to retry.
                                 */
-                               if (is_thp) {
+                               if (is_thp && !nosplit) {
                                        if (!try_split_thp(page, &page2, from)) {
                                                nr_thp_split++;
                                                goto retry;