Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Muchun Song <songmuchun@bytedance.com>
To:     guro@fb.com, hannes@cmpxchg.org, mhocko@kernel.org,
        akpm@linux-foundation.org, shakeelb@google.com,
        vdavydov.dev@gmail.com
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        duanxiongchun@bytedance.com, Muchun Song <songmuchun@bytedance.com>
Subject: [PATCH v4 3/5] mm: memcontrol: change ug->dummy_page only if memcg changed
Date:   Thu, 18 Mar 2021 19:06:56 +0800
Message-Id: <20210318110658.60892-4-songmuchun@bytedance.com>
In-Reply-To: <20210318110658.60892-1-songmuchun@bytedance.com>
References: <20210318110658.60892-1-songmuchun@bytedance.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 mm/memcontrol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index fc22da9805fb..104bddf21314 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6845,6 +6845,7 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
 			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);
@@ -6858,7 +6859,6 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
 	else
 		ug->pgpgout++;
 
-	ug->dummy_page = page;
 	page->memcg_data = 0;
 	css_put(&ug->memcg->css);
 }
-- 
2.11.0