Commit fbed53b4 authored Aug 17, 2022 by Huang Ying Committed by Andrew Morton Sep 26, 2022

migrate_pages(): fix THP failure counting for -ENOMEM

In unmap_and_move(), if the new THP cannot be allocated, -ENOMEM will be
returned, and migrate_pages() will try to split the THP unless "reason" is
MR_NUMA_MISPLACED (that is, nosplit == true).  But when nosplit == true,
the THP migration failure will not be counted.

This is incorrect, so in this patch, the THP migration failure will be
counted for -ENOMEM regardless of nosplit is true or false.  The nr_failed
counting isn't fixed because it's not used.  Added some comments for it
per Baolin's suggestion.

Link: https://lkml.kernel.org/r/20220817081408.513338-4-ying.huang@intel.com


Fixes: 5984fabb ("mm: move_pages: report the number of non-attempted pages")
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent 9c62ff00

mm/migrate.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -1494,11 +1494,11 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
		/*
		* 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 && !nosplit) {
		if (is_thp) {
		nr_thp_failed++;
		if (!try_split_thp(page, &thp_split_pages)) {
		/* THP NUMA faulting doesn't split THP to retry. */
		if (!nosplit && !try_split_thp(page, &thp_split_pages)) {
		nr_thp_split++;
		goto retry;
		}
		@@ -1514,6 +1514,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
		* the caller otherwise the page refcnt will be leaked.
		*/
		list_splice_init(&thp_split_pages, from);
		/* nr_failed isn't updated for not used */
		nr_thp_failed += thp_retry;
		goto out;
		case -EAGAIN: