linux-kernel - Re: [PATCH 00/36] THP refcounting redesign

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Message-ID: <87twt51wuw.fsf@linux.vnet.ibm.com>
Date:	Wed, 15 Jul 2015 17:00:47 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hughd@...gle.com>
Cc:	Dave Hansen <dave.hansen@...el.com>, Mel Gorman <mgorman@...e.de>,
	Rik van Riel <riel@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Christoph Lameter <cl@...two.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Steve Capper <steve.capper@...aro.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Jerome Marchand <jmarchan@...hat.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH 00/36] THP refcounting redesign

"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> writes:

> Hello everybody,
>
> The THP refcounting has been rebased onto current since-4.1 as requested.
>
> 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.
>
> The patchset drastically lower complexity of get_page()/put_page()
> codepaths. I encourage people look on this code before-and-after to
> justify time budget on reviewing this patchset.
>

Tested this series of ppc64. Please feel free to add to the series

Tested-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>

-aneesh

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