linux-kernel - Re: [PATCH v10 7/7] mm: Don't split THP page when syscall is called

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Message-ID: <20140708094810.GB3490@node.dhcp.inet.fi>
Date:	Tue, 8 Jul 2014 12:48:10 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Linux API <linux-api@...r.kernel.org>,
	Hugh Dickins <hughd@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>, Jason Evans <je@...com>,
	Zhang Yanfei <zhangyanfei@...fujitsu.com>
Subject: Re: [PATCH v10 7/7] mm: Don't split THP page when syscall is called

On Tue, Jul 08, 2014 at 10:30:38AM +0900, Minchan Kim wrote:
> Actually, I did but found no problem except CONFIG_DEBUG_VM but rollback
> after peeking [1].
> When I read the description in detail by your review, I think we can remove
> BUG_ON(PageTransHuge(page)) in try_to_unmap and go with no split for lazyfree
> page because they are not in swapcache any more so the assumption of [1] is
> not valid. Will do it in next revision.

No. try_to_unmap() knows nothing about PMDs, so page_check_address() will
always return NULL for THP and you will not unmap anything.

-- 
 Kirill A. Shutemov
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