Re: [PATCH 03/13] mm: Introduce __GFP_MEMALLOC to allow access to emergency reserves
From: NeilBrown <hidden>
Date: 2011-04-26 09:50:05
Also in:
linux-mm, lkml
On Tue, 26 Apr 2011 08:36:44 +0100 Mel Gorman [off-list ref] wrote:
quoted hunk ↗ jump to hunk
__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 <redacted> Signed-off-by: Mel Gorman <mgorman@suse.de> --- 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@kvack.org. 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@kvack.org"> email@kvack.org </a>