[063/131] khugepaged: drain all LRU caches before scanning pages

Commit Message

Andrew Morton June 3, 2020, 11 p.m. UTC

From: "Kirill A. Shutemov" <[e-mail]>
Subject: khugepaged: drain all LRU caches before scanning pages

Having a page in LRU add cache offsets page refcount and gives
false-negative on PageLRU().  It reduces collapse success rate.

Drain all LRU add caches before scanning.  It happens relatively rare and
should not disturb the system too much.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Kirill A. Shutemov <[e-mail]>
Reviewed-by: William Kucharski <[e-mail]>
Reviewed-by: Zi Yan <[e-mail]>
Tested-by: Zi Yan <[e-mail]>
Acked-by: Yang Shi <[e-mail]>
Cc: Andrea Arcangeli <[e-mail]>
Cc: John Hubbard <[e-mail]>
Cc: Mike Kravetz <[e-mail]>
Cc: Ralph Campbell <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/khugepaged.c |    2 ++
 1 file changed, 2 insertions(+)

Patch

--- a/mm/khugepaged.c~khugepaged-drain-all-lru-caches-before-scanning-pages
+++ a/mm/khugepaged.c
@@ -2079,6 +2079,8 @@  static void khugepaged_do_scan(void)
 
 	barrier(); /* write khugepaged_pages_to_scan to local stack */
 
+	lru_add_drain_all();
+
 	while (progress < pages) {
 		if (!khugepaged_prealloc_page(&hpage, &wait))
 			break;