From 0c43513e35f772c81c1b15a06591b893ccf17b3f Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill@shutemov.name>
Date: Sat, 30 Nov 2019 17:57:15 -0800
Subject: [PATCH] mm, thp: do not queue fully unmapped pages for deferred split
References: bnc#1155780 (VM/FS functional and performance backports)
Patch-mainline: v5.5-rc1
Git-commit: f1fe80d4ae3396cf3665bd6dc77f4004c1c2e9f8
Adding fully unmapped pages into deferred split queue is not productive:
these pages are about to be freed or they are pinned and cannot be split
anyway.
Link: http://lkml.kernel.org/r/20190913091849.11151-1-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
mm/rmap.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index b1fd7ee8e7d4..ca2556bcb465 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1289,12 +1289,20 @@ static void page_remove_anon_compound_rmap(struct page *page)
if (TestClearPageDoubleMap(page)) {
/*
* Subpages can be mapped with PTEs too. Check how many of
- * themi are still mapped.
+ * them are still mapped.
*/
for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) {
if (atomic_add_negative(-1, &page[i]._mapcount))
nr++;
}
+
+ /*
+ * Queue the page for deferred split if at least one small
+ * page of the compound page is unmapped, but at least one
+ * small page is still mapped.
+ */
+ if (nr && nr < HPAGE_PMD_NR)
+ deferred_split_huge_page(page);
} else {
nr = HPAGE_PMD_NR;
}
@@ -1302,10 +1310,8 @@ static void page_remove_anon_compound_rmap(struct page *page)
if (unlikely(PageMlocked(page)))
clear_page_mlock(page);
- if (nr) {
+ if (nr)
__mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, -nr);
- deferred_split_huge_page(page);
- }
}
/**