linux-kernel - Re: [PATCH v2 0/7] mm: pages for hugetlb's overcommit may be able to charge to memcg

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Message-ID: <504b1ca0-9030-29be-4657-9cc18575eacb@ascade.co.jp>
Date:   Fri, 25 May 2018 10:51:50 +0900
From:   TSUKADA Koutaro <tsukada@...ade.co.jp>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Jonathan Corbet <corbet@....net>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>,
        David Rientjes <rientjes@...gle.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        Marc-Andre Lureau <marcandre.lureau@...hat.com>,
        Punit Agrawal <punit.agrawal@....com>,
        Dan Williams <dan.j.williams@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, cgroups@...r.kernel.org
Subject: Re: [PATCH v2 0/7] mm: pages for hugetlb's overcommit may be able to
 charge to memcg

On 2018/05/24 22:24, Michal Hocko wrote
[...]> I do not see anything like that. adjust_pool_surplus is simply and
> accounting thing. At least the last time I've checked. Maybe your
> patchset handles that?

As you said, my patch did not consider handling when manipulating the
pool. And even if that handling is done well, it will not be a valid
reason to charge surplus hugepage to memcg.

[...]
>> Absolutely you are saying the right thing, but, for example, can mlock(2)ed
>> pages be swapped out by reclaim?(What is the difference between mlock(2)ed
>> pages and hugetlb page?)
> 
> No mlocked pages cannot be reclaimed and that is why we restrict them to
> a relatively small amount.

I understood the concept of memcg.

[...]
> Fatal? Not sure. It simply tries to add an alien memory to the memcg
> concept so I would pressume an unexpected behavior (e.g. not being able
> to reclaim memcg or, over reclaim, trashing etc.).

As you said, it must be an alien. Thanks to the interaction up to here,
I understood that my solution is inappropriate. I will look for another
way.

Thank you for your kind explanation.

-- 
Thanks,
Tsukada