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[PATCH] reduce MAX_NR_ZONES: use enum to define zones, reformat and comment

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Use enum for zones and reformat zones dependent information

Add comments explaning the use of zones and add a zones_t type for zone
numbers.

Line up information that will be #ifdefd by the following patches.

[akpm@osdl.org: comment cleanups]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Christoph Lameter
2006-09-25 23:31:13 -07:00
committed by Linus Torvalds
parent 98d2b0ebda
commit 2f1b624868
3 changed files with 69 additions and 28 deletions
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66
include/linux/mmzone.h
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@ -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);
}