diff options
Diffstat (limited to 'include/linux/mmzone.h')
| -rw-r--r-- | include/linux/mmzone.h | 66 |
1 files changed, 47 insertions, 19 deletions
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index f45163c528e8..03a5a6eb0ffa 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -88,14 +88,53 @@ struct per_cpu_pageset { #define zone_pcp(__z, __cpu) (&(__z)->pageset[(__cpu)]) #endif -#define ZONE_DMA 0 -#define ZONE_DMA32 1 -#define ZONE_NORMAL 2 -#define ZONE_HIGHMEM 3 +enum zone_type { + /* + * ZONE_DMA is used when there are devices that are not able + * to do DMA to all of addressable memory (ZONE_NORMAL). Then we + * carve out the portion of memory that is needed for these devices. + * The range is arch specific. + * + * Some examples + * + * Architecture Limit + * --------------------------- + * parisc, ia64, sparc <4G + * s390 <2G + * arm26 <48M + * arm Various + * alpha Unlimited or 0-16MB. + * + * i386, x86_64 and multiple other arches + * <16M. + */ + ZONE_DMA, + /* + * x86_64 needs two ZONE_DMAs because it supports devices that are + * only able to do DMA to the lower 16M but also 32 bit devices that + * can only do DMA areas below 4G. + */ + ZONE_DMA32, + /* + * Normal addressable memory is in ZONE_NORMAL. DMA operations can be + * performed on pages in ZONE_NORMAL if the DMA devices support + * transfers to all addressable memory. + */ + ZONE_NORMAL, + /* + * A memory area that is only addressable by the kernel through + * mapping portions into its own address space. This is for example + * used by i386 to allow the kernel to address the memory beyond + * 900MB. The kernel will set up special mappings (page + * table entries on i386) for each page that the kernel needs to + * access. + */ + ZONE_HIGHMEM, -#define MAX_NR_ZONES 4 /* Sync this with ZONES_SHIFT */ -#define ZONES_SHIFT 2 /* ceil(log2(MAX_NR_ZONES)) */ + MAX_NR_ZONES +}; +#define ZONES_SHIFT 2 /* ceil(log2(MAX_NR_ZONES)) */ /* * When a memory allocation must conform to specific limitations (such @@ -126,16 +165,6 @@ struct per_cpu_pageset { /* #define GFP_ZONETYPES (GFP_ZONEMASK + 1) */ /* Non-loner */ #define GFP_ZONETYPES ((GFP_ZONEMASK + 1) / 2 + 1) /* Loner */ -/* - * On machines where it is needed (eg PCs) we divide physical memory - * into multiple physical zones. On a 32bit PC we have 4 zones: - * - * ZONE_DMA < 16 MB ISA DMA capable memory - * ZONE_DMA32 0 MB Empty - * ZONE_NORMAL 16-896 MB direct mapped by the kernel - * ZONE_HIGHMEM > 896 MB only page cache and user processes - */ - struct zone { /* Fields commonly accessed by the page allocator */ unsigned long free_pages; @@ -266,7 +295,6 @@ struct zone { char *name; } ____cacheline_internodealigned_in_smp; - /* * The "priority" of VM scanning is how much of the queues we will scan in one * go. A value of 12 for DEF_PRIORITY implies that we will scan 1/4096th of the @@ -373,12 +401,12 @@ static inline int populated_zone(struct zone *zone) return (!!zone->present_pages); } -static inline int is_highmem_idx(int idx) +static inline int is_highmem_idx(enum zone_type idx) { return (idx == ZONE_HIGHMEM); } -static inline int is_normal_idx(int idx) +static inline int is_normal_idx(enum zone_type idx) { return (idx == ZONE_NORMAL); } |