linux-kernel - Re: [External] Re: [PATCH v15 4/8] mm: hugetlb: alloc the vmemmap pages associated with each HugeTLB page

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Message-ID: <YCuAbWJC751ROfTS@dhcp22.suse.cz>
Date:   Tue, 16 Feb 2021 09:21:01 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     Muchun Song <songmuchun@...edance.com>,
        Jonathan Corbet <corbet@....net>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org,
        Peter Zijlstra <peterz@...radead.org>, viro@...iv.linux.org.uk,
        Andrew Morton <akpm@...ux-foundation.org>, paulmck@...nel.org,
        mchehab+huawei@...nel.org, pawan.kumar.gupta@...ux.intel.com,
        Randy Dunlap <rdunlap@...radead.org>, oneukum@...e.com,
        anshuman.khandual@....com, jroedel@...e.de,
        Mina Almasry <almasrymina@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Oscar Salvador <osalvador@...e.de>,
        "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>,
        HORIGUCHI NAOYA(堀口 直也) 
        <naoya.horiguchi@....com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Xiongchun duan <duanxiongchun@...edance.com>,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [External] Re: [PATCH v15 4/8] mm: hugetlb: alloc the vmemmap
 pages associated with each HugeTLB page

On Tue 16-02-21 09:13:09, David Hildenbrand wrote:
> On 15.02.21 20:02, Michal Hocko wrote:
> > Would it be feasible to reused parts of the freed page in
> > the worst case?
> 
> As already discussed, this is only possible when the huge page does not
> reside on ZONE_MOVABLE/CMA.

Right. But usually this is not the case so it would be at least
something.

> In addition, we can no longer form a huge page at that memory location ever.

Yes, that's why I am saying in the worst case. E.g. when dissolving is
really necessary like in hwpoison case.

Maybe we are really far from needing something like that. I just wanted
to mention this option and I was not aware this has been discussed
previously.
-- 
Michal Hocko
SUSE Labs