linux-kernel - Re: [patch 1/5] mm: page_alloc: increase __GFP_BITS_SHIFT to include __GFP_OTHER

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Date:	Wed, 27 Jul 2011 14:50:08 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <jweiner@...hat.com>
Cc:	linux-mm@...ck.org, Dave Chinner <david@...morbit.com>,
	Christoph Hellwig <hch@...radead.org>,
	Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>, Jan Kara <jack@...e.cz>,
	Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org
Subject: Re: [patch 1/5] mm: page_alloc: increase __GFP_BITS_SHIFT to include
 __GFP_OTHER_NODE

On Mon 25-07-11 22:19:15, Johannes Weiner wrote:
> From: Johannes Weiner <hannes@...xchg.org>
> 
> __GFP_OTHER_NODE is used for NUMA allocations on behalf of other
> nodes.  It's supposed to be passed through from the page allocator to
> zone_statistics(), but it never gets there as gfp_allowed_mask is not
> wide enough and masks out the flag early in the allocation path.
> 
> The result is an accounting glitch where successful NUMA allocations
> by-agent are not properly attributed as local.
> 
> Increase __GFP_BITS_SHIFT so that it includes __GFP_OTHER_NODE.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Reviewed-by: Michal Hocko <mhocko@...e.cz>

> ---
>  include/linux/gfp.h |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index cb40892..3a76faf 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -92,7 +92,7 @@ struct vm_area_struct;
>   */
>  #define __GFP_NOTRACK_FALSE_POSITIVE (__GFP_NOTRACK)
>  
> -#define __GFP_BITS_SHIFT 23	/* Room for 23 __GFP_FOO bits */
> +#define __GFP_BITS_SHIFT 24	/* Room for N __GFP_FOO bits */
>  #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
>  
>  /* This equals 0, but use constants in case they ever change */
> -- 
> 1.7.6

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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