Commit be3a0ee8 authored May 10, 2024 by Kirill A. Shutemov Committed by Wupeng Ma May 10, 2024

mm, thp: do not queue fully unmapped pages for deferred split

mainline inclusion
from mainline-v5.5-rc1
commit f1fe80d4
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I9NU9F

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=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: Ma Wupeng <mawupeng1@huawei.com>

parent 7d91c9c7

mm/rmap.c

+10 −4

Original line number	Diff line number	Diff line
		@@ -1281,12 +1281,20 @@ 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;
		}
		@@ -1294,10 +1302,8 @@ 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);
		}
		}

		/**