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From:   Shakeel Butt <shakeelb@google.com>
Date:   Wed, 10 Nov 2021 18:59:21 -0800
Message-ID: <CALvZod6bXJR5YKHYiOkc1tSMzGB2EnB8KeLEh3SF2uP6DWYcpQ@mail.gmail.com>
Subject: Re: [PATCH v6] hugetlb: Add hugetlb.*.numa_stat file
To:     Muchun Song <songmuchun@bytedance.com>
Cc:     Mina Almasry <almasrymina@google.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Shuah Khan <shuah@kernel.org>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Oscar Salvador <osalvador@suse.de>,
        Michal Hocko <mhocko@suse.com>,
        David Rientjes <rientjes@google.com>,
        Jue Wang <juew@google.com>, Yang Yao <ygyao@google.com>,
        Joanna Li <joannali@google.com>,
        Cannon Matthews <cannonmatthews@google.com>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Wed, Nov 10, 2021 at 6:36 PM Muchun Song <songmuchun@bytedance.com> wrote:
>
[...]
> > +struct hugetlb_cgroup_per_node {
> > +       /* hugetlb usage in pages over all hstates. */
> > +       atomic_long_t usage[HUGE_MAX_HSTATE];
>
> Why do you use atomic? IIUC, 'usage' is always
> increased/decreased under hugetlb_lock except
> hugetlb_cgroup_read_numa_stat() which is always
> reading it. So I think WRITE_ONCE/READ_ONCE
> is enough.

Oh this is me misguiding Mina, sorry about that. Yes, READ_ONCE()
should be good enough in hugetlb_cgroup_read_numa_stat().