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Date:	Thu, 19 Mar 2015 19:10:43 +0200
From:	"Kirill A. Shutemov" <>
To:	"Aneesh Kumar K.V" <>
Cc:	"Kirill A. Shutemov" <>,
	Andrew Morton <>,
	Andrea Arcangeli <>,
	Dave Hansen <>,
	Hugh Dickins <>, Mel Gorman <>,
	Rik van Riel <>,
	Vlastimil Babka <>,
	Christoph Lameter <>,
	Naoya Horiguchi <>,
	Steve Capper <>,
	Johannes Weiner <>,
	Michal Hocko <>,
	Jerome Marchand <>,,
Subject: Re: [PATCHv4 00/24] THP refcounting redesign

On Tue, Mar 17, 2015 at 03:12:05PM +0530, Aneesh Kumar K.V wrote:
> "Kirill A. Shutemov" <> 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.

Thanks a lot.

Could you also prepare patch to drop power-specific code related to
pmd_trans_splitting()? It's not needed anymore with the patchset.

 Kirill A. Shutemov
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