Re: [PATCH 12/25] Remove a branch by assuming __GFP_HIGH == ALLOC_HIGH

KOSAKI Motohiro
2009-04-21T09:08:19Z

> Allocations that specify __GFP_HIGH get the ALLOC_HIGH flag. If these
> flags are equal to each other, we can eliminate a branch.
>
> [akpm@linux-foundation.org: Suggested the hack]
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> ---
> mm/page_alloc.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 51e1ded..b13fc29 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1639,8 +1639,8 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
> * policy or is asking for __GFP_HIGH memory. GFP_ATOMIC requests will
> * set both ALLOC_HARDER (!wait) and ALLOC_HIGH (__GFP_HIGH).
> */
> - if (gfp_mask & __GFP_HIGH)
> - alloc_flags |= ALLOC_HIGH;
> + VM_BUG_ON(__GFP_HIGH != ALLOC_HIGH);
> + alloc_flags |= (gfp_mask & __GFP_HIGH);
>
> if (!wait) {
> alloc_flags |= ALLOC_HARDER;

Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>