Re: [PATCH] mm, thp: move invariant bug check out of loop in __split_huge_page_map

Kirill A. Shutemov
2014-06-16T20:52:30Z

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?