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Wed, 26 May 2021 23:24:28 -0700 (PDT) Received: from localhost.localdomain ([139.177.225.254]) by smtp.gmail.com with ESMTPSA id m5sm882971pgl.75.2021.05.26.23.24.21 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 26 May 2021 23:24:28 -0700 (PDT) From: Muchun Song To: willy@infradead.org, akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, shakeelb@google.com, guro@fb.com, shy828301@gmail.com, alexs@kernel.org, richard.weiyang@gmail.com, david@fromorbit.com, trond.myklebust@hammerspace.com, anna.schumaker@netapp.com Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-nfs@vger.kernel.org, zhengqi.arch@bytedance.com, duanxiongchun@bytedance.com, fam.zheng@bytedance.com, Muchun Song Subject: [PATCH v2 02/21] mm: memcontrol: remove kmemcg_id reparenting Date: Thu, 27 May 2021 14:21:29 +0800 Message-Id: <20210527062148.9361-3-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) In-Reply-To: <20210527062148.9361-1-songmuchun@bytedance.com> References: <20210527062148.9361-1-songmuchun@bytedance.com> MIME-Version: 1.0 X-Rspamd-Queue-Id: B7A8D500166D Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=bytedance-com.20150623.gappssmtp.com header.s=20150623 header.b=MJSyMYT7; spf=pass (imf01.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.215.181 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com; dmarc=pass (policy=none) header.from=bytedance.com X-Rspamd-Server: rspam04 X-Stat-Signature: gntzqoae3tmw5f8kau4s1e6z69im5kgp X-HE-Tag: 1622096661-691676 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Since slab objects and kmem pages are charged to object cgroup instead of memory cgroup, memcg_reparent_objcgs() will reparent this cgroup and all its descendants to the parent cgroup. This already makes further list_lru_add()'s add elements to the parent's list. So we do not need to change kmemcg_id of an offline cgroup to its parent's id. It is just waste CPU cycles. Just remove those redundant code. Signed-off-by: Muchun Song --- mm/memcontrol.c | 20 ++------------------ 1 file changed, 2 insertions(+), 18 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index db29b96f7311..9add859f69d7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3654,8 +3654,7 @@ static int memcg_online_kmem(struct mem_cgroup *mem= cg) =20 static void memcg_offline_kmem(struct mem_cgroup *memcg) { - struct cgroup_subsys_state *css; - struct mem_cgroup *parent, *child; + struct mem_cgroup *parent; int kmemcg_id; =20 if (memcg->kmem_state !=3D KMEM_ONLINE) @@ -3672,22 +3671,7 @@ static void memcg_offline_kmem(struct mem_cgroup *= memcg) kmemcg_id =3D memcg->kmemcg_id; BUG_ON(kmemcg_id < 0); =20 - /* - * Change kmemcg_id of this cgroup and all its descendants to the - * parent's id, and then move all entries from this cgroup's list_lrus - * to ones of the parent. After we have finished, all list_lrus - * corresponding to this cgroup are guaranteed to remain empty. The - * ordering is imposed by list_lru_node->lock taken by - * memcg_drain_all_list_lrus(). - */ - rcu_read_lock(); /* can be called from css_free w/o cgroup_mutex */ - css_for_each_descendant_pre(css, &memcg->css) { - child =3D mem_cgroup_from_css(css); - BUG_ON(child->kmemcg_id !=3D kmemcg_id); - child->kmemcg_id =3D parent->kmemcg_id; - } - rcu_read_unlock(); - + /* memcg_reparent_objcgs() must be called before this. */ memcg_drain_all_list_lrus(kmemcg_id, parent); =20 memcg_free_cache_id(kmemcg_id); --=20 2.11.0