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Date:   Thu, 15 Dec 2022 18:18:03 +0000
In-Reply-To: <20221215091907.763801-1-haifeng.xu@shopee.com>
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Message-ID: <20221215181803.ome46pkh6g7qu3t4@google.com>
Subject: Re: [PATCH] mm/memcontrol: Skip root memcg in memcg_memory_event_mm
From:   Shakeel Butt <shakeelb@google.com>
To:     Haifeng Xu <haifeng.xu@shopee.com>
Cc:     akpm@linux-foundation.org, roman.gushchin@linux.dev,
        songmuchun@bytedance.com, hannes@cmpxchg.org, vbabka@suse.cz,
        willy@infradead.org, vasily.averin@linux.dev,
        linux-kernel@vger.kernel.org
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On Thu, Dec 15, 2022 at 09:19:07AM +0000, Haifeng Xu wrote:
> The memory events aren't supported on root cgroup, so there is no need
> to account MEMCG_OOM_KILL on root memcg.
> 

Can you explain the scenario where this is happening and causing issue
for you?

> Signed-off-by: Haifeng Xu <haifeng.xu@shopee.com>
> ---
>  include/linux/memcontrol.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 567f12323f55..09f75161a3bc 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1142,7 +1142,7 @@ static inline void memcg_memory_event_mm(struct mm_struct *mm,
>  
>  	rcu_read_lock();
>  	memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
> -	if (likely(memcg))
> +	if (likely(memcg && !mem_cgroup_is_root(memcg)))

Even if we need this additional check, this is not the right place.

>  		memcg_memory_event(memcg, event);
>  	rcu_read_unlock();
>  }
> -- 
> 2.25.1
>