Re: [PATCH 2/3] mm: free zapped tail pages when splitting isolated thp
From: Kirill A. Shutemov <hidden>
Date: 2021-08-04 14:22:59
Also in:
lkml
On Sat, Jul 31, 2021 at 12:39:37AM -0600, Yu Zhao wrote:
quoted hunk ↗ jump to hunk
@@ -2506,6 +2508,25 @@ static void __split_huge_page(struct page *page, struct list_head *list, continue; unlock_page(subpage); + /* + * If a tail page has only two references left, one inherited + * from the isolation of its head and the other from + * lru_add_page_tail() which we are about to drop, it means this + * tail page was concurrently zapped. Then we can safely free it + * and save page reclaim or migration the trouble of trying it. + */ + if (list && page_ref_freeze(subpage, 2)) { + VM_BUG_ON_PAGE(PageLRU(subpage), subpage); + VM_BUG_ON_PAGE(PageCompound(subpage), subpage); + VM_BUG_ON_PAGE(page_mapped(subpage), subpage); + + ClearPageActive(subpage); + ClearPageUnevictable(subpage);
Why touch PG_Active/PG_Unevictable?
+ list_move(&subpage->lru, &pages_to_free); + nr_pages_to_free++; + continue; + } +
-- Kirill A. Shutemov