From: Muchun Song <songmuchun@xxxxxxxxxxxxx> Subject: mm: memcontrol: change ug->dummy_page only if memcg changed Just like assignment to ug->memcg, we only need to update ug->dummy_page if memcg changed. So move it to there. This is a very small optimization. Link: https://lkml.kernel.org/r/20210319163821.20704-5-songmuchun@xxxxxxxxxxxxx Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Roman Gushchin <guro@xxxxxx> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Cc: Xiongchun Duan <duanxiongchun@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/memcontrol.c~mm-memcontrol-change-ug-dummy_page-only-if-memcg-changed +++ a/mm/memcontrol.c @@ -6843,6 +6843,7 @@ static void uncharge_page(struct page *p uncharge_gather_clear(ug); } ug->memcg = page_memcg(page); + ug->dummy_page = page; /* pairs with css_put in uncharge_batch */ css_get(&ug->memcg->css); @@ -6856,7 +6857,6 @@ static void uncharge_page(struct page *p else ug->pgpgout++; - ug->dummy_page = page; page->memcg_data = 0; css_put(&ug->memcg->css); } _
