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Date:   Mon, 23 Nov 2020 14:34:18 -0400
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     Pavel Tatashin <pasha.tatashin@soleen.com>
Cc:     Michal Hocko <mhocko@suse.com>, linux-mm <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        LKML <linux-kernel@vger.kernel.org>,
        David Hildenbrand <david@redhat.com>,
        Oscar Salvador <osalvador@suse.de>,
        Dan Williams <dan.j.williams@intel.com>,
        Sasha Levin <sashal@kernel.org>,
        Tyler Hicks <tyhicks@linux.microsoft.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Stephen Hemminger <sthemmin@microsoft.com>
Subject: Re: Pinning ZONE_MOVABLE pages
Message-ID: <20201123183418.GB5487@ziepe.ca>
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On Mon, Nov 23, 2020 at 12:54:16PM -0500, Pavel Tatashin wrote:
> > I agree with the other emails, ZONE_MOVABLE needs to be reconciled
> > with FOLL_LONGTERM - most likely by preventing ZONE_MOVABLE pages from
> > being returned. This will need migration like CMA does and the point
> > about faulting is only an optimization to prevent fault then immediate
> > migration.
> 
> That is right, as the first step we could just do fault and immediate
> migration, which is silly, but still better than what we have now.

I was looking at this CMA code lately and would love to see a
cleaner/faster implementation.

If you really understand how this works maybe it is an opportunity to
make it all work better.

Jason