From: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> Subject: mm, thp: do not queue fully unmapped pages for deferred split 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@xxxxxxxxxxxxxxx Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Reviewed-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/rmap.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) --- a/mm/rmap.c~mm-thp-do-not-queue-fully-unmapped-pages-for-deferred-split +++ a/mm/rmap.c @@ -1292,12 +1292,20 @@ static void page_remove_anon_compound_rm 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; } @@ -1305,10 +1313,8 @@ static void page_remove_anon_compound_rm 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); - } } /** _
