linux-kernel - Re: [Resend PATCH 1/6] mm/memcg: warning on !memcg after readahead page charged

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Message-ID: <12425e06-38ce-7ff4-28ce-b0418353fc67@linux.alibaba.com>
Date:   Tue, 25 Aug 2020 09:25:01 +0800
From:   Alex Shi <alex.shi@...ux.alibaba.com>
To:     Michal Hocko <mhocko@...e.com>, Qian Cai <cai@....pw>
Cc:     akpm@...ux-foundation.org, Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, nao.horiguchi@...il.com,
        osalvador@...e.de, mike.kravetz@...cle.com
Subject: Re: [Resend PATCH 1/6] mm/memcg: warning on !memcg after readahead
 page charged

reproduce using our linux-mm random bug collection on NUMA systems.
>>
>> OK, I must have missed that this was on ppc. The order makes more sense
>> now. I will have a look at this next week.
> 
> OK, so I've had a look and I know what's going on there. The
> move_pages12 is migrating hugetlb pages. Those are not charged to any
> memcg. We have completely missed this case. There are two ways going
> around that. Drop the warning and update the comment so that we do not
> forget about that or special case hugetlb pages.
> 
> I think the first option is better.
> 


Hi Michal,

Compare to ignore the warning which is designed to give, seems addressing
the hugetlb out of charge issue is a better solution, otherwise the memcg
memory usage is out of control on hugetlb, is that right?

Thanks
Alex