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From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Hugh Dickins <hughd@google.com>, Mel Gorman <mgorman@suse.de>,
	Rik van Riel <riel@redhat.com>, Vlastimil Babka <vbabka@suse.cz>,
	Christoph Lameter <cl@gentwo.org>,
	Steve Capper <steve.capper@linaro.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@suse.cz>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH 10/19] thp: PMD splitting without splitting compound page
Date: Wed, 19 Nov 2014 15:02:14 +0200	[thread overview]
Message-ID: <20141119130214.GB29884@node.dhcp.inet.fi> (raw)
In-Reply-To: <20141119065823.GA16887@hori1.linux.bs1.fc.nec.co.jp>

On Wed, Nov 19, 2014 at 06:57:47AM +0000, Naoya Horiguchi wrote:
> On Wed, Nov 05, 2014 at 04:49:45PM +0200, Kirill A. Shutemov wrote:
> > Current split_huge_page() combines two operations: splitting PMDs into
> > tables of PTEs and splitting underlying compound page. This patch
> > changes split_huge_pmd() implementation to split the given PMD without
> > splitting other PMDs this page mapped with or underlying compound page.
> > 
> > In order to do this we have to get rid of tail page refcounting, which
> > uses _mapcount of tail pages. Tail page refcounting is needed to be able
> > to split THP page at any point: we always know which of tail pages is
> > pinned (i.e. by get_user_pages()) and can distribute page count
> > correctly.
> > 
> > We can avoid this by allowing split_huge_page() to fail if the compound
> > page is pinned. This patch removes all infrastructure for tail page
> > refcounting and make split_huge_page() to always return -EBUSY. All
> > split_huge_page() users already know how to handle its fail. Proper
> > implementation will be added later.
> > 
> > Without tail page refcounting, implementation of split_huge_pmd() is
> > pretty straight-forward.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> > ---
> ...
> 
> > diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
> > index 7e70ae968e5f..e4ba17694b6b 100644
> > --- a/arch/powerpc/mm/hugetlbpage.c
> > +++ b/arch/powerpc/mm/hugetlbpage.c
> > @@ -1022,7 +1022,6 @@ int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
> >  {
> >  	unsigned long mask;
> >  	unsigned long pte_end;
> > -	struct page *head, *page, *tail;
> >  	pte_t pte;
> >  	int refs;
> >  
> 
> This breaks build of powerpc, so you need keep *head and *page as
> you do for other architectures.

Yeah. I've already fixed this localy after 0-DAY kernel testing
complained.

Thanks.

-- 
 Kirill A. Shutemov

  reply	other threads:[~2014-11-19 13:02 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-05 14:49 [PATCHv2 RFC 00/19] THP refcounting redesign Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 01/19] mm, thp: drop FOLL_SPLIT Kirill A. Shutemov
2014-11-25  3:01   ` Naoya Horiguchi
2014-11-25 14:04     ` Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 02/19] thp: cluster split_huge_page* code together Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 03/19] mm: change PageAnon() to work on tail pages Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 04/19] mm: avoid PG_locked " Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 05/19] rmap: add argument to charge compound page Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 06/19] mm: store mapcount for compound page separate Kirill A. Shutemov
2014-11-18  8:43   ` Naoya Horiguchi
2014-11-18  9:58     ` Kirill A. Shutemov
2014-11-18 23:41       ` Naoya Horiguchi
2014-11-19  0:54         ` Kirill A. Shutemov
2014-11-21  6:41       ` Aneesh Kumar K.V
2014-11-21 11:47         ` Kirill A. Shutemov
2014-11-19 10:51   ` Jerome Marchand
2014-11-19 13:00     ` Kirill A. Shutemov
2014-11-19 13:15       ` Jerome Marchand
2014-11-20 20:06       ` Christoph Lameter
2014-11-21 12:01         ` Kirill A. Shutemov
2014-11-21  6:12   ` Aneesh Kumar K.V
2014-11-21 12:02     ` Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 07/19] mm, thp: adjust conditions when we can reuse the page on WP fault Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 08/19] mm: prepare migration code for new THP refcounting Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 09/19] thp: rename split_huge_page_pmd() to split_huge_pmd() Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 10/19] thp: PMD splitting without splitting compound page Kirill A. Shutemov
2014-11-19  6:57   ` Naoya Horiguchi
2014-11-19 13:02     ` Kirill A. Shutemov [this message]
2014-11-05 14:49 ` [PATCH 11/19] mm, vmstats: new THP splitting event Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 12/19] thp: implement new split_huge_page() Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 13/19] mm, thp: remove infrastructure for handling splitting PMDs Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 14/19] x86, thp: remove " Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 15/19] futex, thp: remove special case for THP in get_futex_key Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 16/19] thp: update documentation Kirill A. Shutemov
2014-11-19  8:07   ` Naoya Horiguchi
2014-11-19 13:11     ` Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 17/19] mlock, thp: HACK: split all pages in VM_LOCKED vma Kirill A. Shutemov
2014-11-19  9:02   ` Naoya Horiguchi
2014-11-19 13:08     ` Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 18/19] tho, mm: use migration entries to freeze page counts on split Kirill A. Shutemov
2014-11-05 14:49 ` [PATCH 19/19] mm, thp: remove compound_lock Kirill A. Shutemov

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