If we have a lot of pages in queue to be split, deferred_split_scan()
can spend unreasonable amount of time under spinlock with disabled
interrupts.
Let's cap number of pages to split on scan by sc->nr_to_scan.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reported-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
---
mm/huge_memory.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 36f98459f854..298dbc001b07 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3478,17 +3478,19 @@ static unsigned long deferred_split_scan(struct shrinker *shrink,
int split = 0;
spin_lock_irqsave(&pgdata->split_queue_lock, flags);
- list_splice_init(&pgdata->split_queue, &list);
-
/* Take pin on all head pages to avoid freeing them under us */
list_for_each_safe(pos, next, &list) {
page = list_entry((void *)pos, struct page, mapping);
page = compound_head(page);
- /* race with put_compound_page() */
- if (!get_page_unless_zero(page)) {
+ if (get_page_unless_zero(page)) {
+ list_move(page_deferred_list(page), &list);
+ } else {
+ /* We lost race with put_compound_page() */
list_del_init(page_deferred_list(page));
pgdata->split_queue_len--;
}
+ if (!--sc->nr_to_scan)
+ break;
}
spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
--
2.7.0.rc3
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