On Tue, 26 Apr 2011 08:36:44 +0100 Mel Gorman <mgorman@xxxxxxx> wrote:
> __GFP_MEMALLOC will allow the allocation to disregard the watermarks,
> much like PF_MEMALLOC. It allows one to pass along the memalloc state in
> object related allocation flags as opposed to task related flags, such
> as sk->sk_allocation. This removes the need for ALLOC_PFMEMALLOC as
> callers using __GFP_MEMALLOC can get the ALLOC_NO_WATERMARK flag which
> is now enough to identify allocations related to page reclaim.
>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
> ---
> include/linux/gfp.h | 4 +++-
> include/linux/mm_types.h | 2 +-
> mm/page_alloc.c | 14 ++++++--------
> mm/slab.c | 2 +-
> 4 files changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index bfb8f93..4e011e7 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -23,6 +23,7 @@ struct vm_area_struct;
> #define ___GFP_REPEAT 0x400u
> #define ___GFP_NOFAIL 0x800u
> #define ___GFP_NORETRY 0x1000u
> +#define ___GFP_MEMALLOC 0x2000u
> #define ___GFP_COMP 0x4000u
> #define ___GFP_ZERO 0x8000u
> #define ___GFP_NOMEMALLOC 0x10000u
> @@ -75,6 +76,7 @@ struct vm_area_struct;
> #define __GFP_REPEAT ((__force gfp_t)___GFP_REPEAT) /* See above */
> #define __GFP_NOFAIL ((__force gfp_t)___GFP_NOFAIL) /* See above */
> #define __GFP_NORETRY ((__force gfp_t)___GFP_NORETRY) /* See above */
> +#define __GFP_MEMALLOC ((__force gfp_t)___GFP_MEMALLOC)/* Allow access to emergency reserves */
> #define __GFP_COMP ((__force gfp_t)___GFP_COMP) /* Add compound page metadata */
> #define __GFP_ZERO ((__force gfp_t)___GFP_ZERO) /* Return zeroed page on success */
> #define __GFP_NOMEMALLOC ((__force gfp_t)___GFP_NOMEMALLOC) /* Don't use emergency reserves */
Having both "MEMALLOC" and "NOMEMALLOC" seems ... unfortunate.
It appears that NOMEMALLOC over-rides MEMALLOC. It might be good to document
this
> +#define __GFP_MEMALLOC ((__force gfp_t)___GFP_MEMALLOC)/* Allow access to emergency reserves
unless __GFP_NOMEMALLOC is set*/
> #define __GFP_NOMEMALLOC ((__force gfp_t)___GFP_NOMEMALLOC) /* Don't use emergency reserves
Overrides __GFP_MEMALLOC */
I suspect that it is never valid to set both. So NOMEMALLOC is really
NO_PF_MEMALLOC, but making that change is probably just noise.
Maybe a
WARN_ON((gfp_mask & __GFP_MEMALLOC) && (gfp_mask & __GFP_NOMEMALLOC));
might be wise?
NeilBrown.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxxx For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>