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Date:	Mon, 16 Jun 2014 23:49:34 +0300
From:	"Kirill A. Shutemov" <>
To:	Waiman Long <>
Cc:	Andrew Morton <>,
	Mel Gorman <>, Rik van Riel <>,
	Ingo Molnar <>,
	Peter Zijlstra <>,,,
	Scott J Norton <>
Subject: Re: [PATCH] mm, thp: move invariant bug check out of loop in

On Mon, Jun 16, 2014 at 03:35:48PM -0400, Waiman Long wrote:
> In the __split_huge_page_map() function, the check for
> page_mapcount(page) is invariant within the for loop. Because of the
> fact that the macro is implemented using atomic_read(), the redundant
> check cannot be optimized away by the compiler leading to unnecessary
> read to the page structure.
> This patch move the invariant bug check out of the loop so that it
> will be done only once.

Looks okay, but why? Was you able to measure difference?

 Kirill A. Shutemov
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