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;
MIME-Version: 1.0
References: <20210409122959.82264-1-songmuchun@bytedance.com> <20210409122959.82264-3-songmuchun@bytedance.com>
In-Reply-To: <20210409122959.82264-3-songmuchun@bytedance.com>
From:   Shakeel Butt <shakeelb@google.com>
Date:   Sat, 10 Apr 2021 10:47:08 -0700
Message-ID: <CALvZod5Z4r7RyU-zQdWBUn8bKibviXrfbyqVpgmO_e6VDjBHCg@mail.gmail.com>
Subject: Re: [RFC PATCH v2 02/18] mm: memcontrol: bail out early when !mm in get_mem_cgroup_from_mm
To:     Muchun Song <songmuchun@bytedance.com>
Cc:     Roman Gushchin <guro@fb.com>, Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>,
        Xiongchun duan <duanxiongchun@bytedance.com>,
        fam.zheng@bytedance.com, Balbir Singh <bsingharora@gmail.com>,
        Yang Shi <shy828301@gmail.com>,
        Alex Shi <alex.shi@linux.alibaba.com>,
        Dan Schatzberg <schatzberg.dan@gmail.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, Apr 9, 2021 at 5:32 AM Muchun Song <songmuchun@bytedance.com> wrote:
>
> When mm is NULL, we do not need to hold rcu lock and call css_tryget for
> the root memcg. And we also do not need to check !mm in every loop of
> while. So bail out early when !mm.
>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>

Reviewed-by: Shakeel Butt <shakeelb@google.com>