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Date: Sat, 19 Mar 2016 04:02:40 +0300
From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Hugh Dickins <hughd@google.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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        Sasha Levin <sasha.levin@oracle.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCHv4 08/25] thp: support file pages in zap_huge_pmd()
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On Fri, Mar 18, 2016 at 07:23:41PM +0530, Aneesh Kumar K.V wrote:
> "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> writes:
> 
> > [ text/plain ]
> > split_huge_pmd() for file mappings (and DAX too) is implemented by just
> > clearing pmd entry as we can re-fill this area from page cache on pte
> > level later.
> >
> > This means we don't need deposit page tables when file THP is mapped.
> > Therefore we shouldn't try to withdraw a page table on zap_huge_pmd()
> > file THP PMD.
> 
> Archs like ppc64 use deposited page table to track the hardware page
> table slot information. We probably may want to add hooks which arch can
> use to achieve the same even with file THP 

Could you describe more on what kind of information you're talking about?

-- 
 Kirill A. Shutemov