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Date:   Wed, 17 Feb 2021 14:54:24 +0100
From:   Michal Hocko <mhocko@suse.com>
To:     Oscar Salvador <osalvador@suse.de>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        David Hildenbrand <david@redhat.com>,
        Muchun Song <songmuchun@bytedance.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] mm: Make alloc_contig_range handle in-use hugetlb
 pages
Message-ID: <YC0gEBEeeDT1lZhD@dhcp22.suse.cz>
References: <20210217100816.28860-1-osalvador@suse.de>
 <20210217100816.28860-3-osalvador@suse.de>
 <YC0b39IfoI+c0ts1@dhcp22.suse.cz>
 <20210217134649.GB32488@linux>
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On Wed 17-02-21 14:46:49, Oscar Salvador wrote:
> On Wed, Feb 17, 2021 at 02:36:31PM +0100, Michal Hocko wrote:
> > On Wed 17-02-21 11:08:16, Oscar Salvador wrote:
> > > In-use hugetlb pages can be migrated as any other page (LRU
> > > and Movable), so let alloc_contig_range handle them.
> > > 
> > > All we need is to succesfully isolate such page.
> > 
> > Again, this is missing a problem statement and a justification why we
> > want/need this.
> 
> Heh, I was poor in words.
> 
> "alloc_contig_range() will fail miserably if it finds a HugeTLB page within
>  the range without a chance to handle them. Since HugeTLB pages can be migrated
>  as any other page (LRU and Movable), it does not make sense to bail out.
>  Enable the interface to recognize in-use HugeTLB pages and have a chance
>  to migrate them"
> 
> What about something along those lines?

Is this a real life problem? I know we _can_ but I do not see any
reasoning _why_ should we care all that much.
-- 
Michal Hocko
SUSE Labs