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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrea Arcangeli <aarcange@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>, Hugh Dickins <hughd@google.com>,
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        Vlastimil Babka <vbabka@suse.cz>, Christoph Lameter <cl@gentwo.org>,
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        Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@suse.cz>,
        Jerome Marchand <jmarchan@redhat.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCHv4 00/24] THP refcounting redesign
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"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> writes:

> Hello everybody,
>
> It's bug-fix update of my thp refcounting work.
>
> The goal of patchset is to make refcounting on THP pages cheaper with
> simpler semantics and allow the same THP compound page to be mapped with
> PMD and PTEs. This is required to get reasonable THP-pagecache
> implementation.
>
> With the new refcounting design it's much easier to protect against
> split_huge_page(): simple reference on a page will make you the deal.
> It makes gup_fast() implementation simpler and doesn't require
> special-case in futex code to handle tail THP pages.
>
> It should improve THP utilization over the system since splitting THP in
> one process doesn't necessary lead to splitting the page in all other
> processes have the page mapped.

I tested this patch on ppc64 and verified thp allocation and split.
I also checked the subpage_prot and it worked as expected. I will
run more tests with this series and update if I find any issues.

-aneesh