diff options
Diffstat (limited to 'include/linux/page-flags-layout.h')
| -rw-r--r-- | include/linux/page-flags-layout.h | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h new file mode 100644 index 000000000000..93506a114034 --- /dev/null +++ b/include/linux/page-flags-layout.h @@ -0,0 +1,88 @@ +#ifndef PAGE_FLAGS_LAYOUT_H +#define PAGE_FLAGS_LAYOUT_H + +#include <linux/numa.h> +#include <generated/bounds.h> + +/* + * When a memory allocation must conform to specific limitations (such + * as being suitable for DMA) the caller will pass in hints to the + * allocator in the gfp_mask, in the zone modifier bits. These bits + * are used to select a priority ordered list of memory zones which + * match the requested limits. See gfp_zone() in include/linux/gfp.h + */ +#if MAX_NR_ZONES < 2 +#define ZONES_SHIFT 0 +#elif MAX_NR_ZONES <= 2 +#define ZONES_SHIFT 1 +#elif MAX_NR_ZONES <= 4 +#define ZONES_SHIFT 2 +#else +#error ZONES_SHIFT -- too many zones configured adjust calculation +#endif + +#ifdef CONFIG_SPARSEMEM +#include <asm/sparsemem.h> + +/* SECTION_SHIFT #bits space required to store a section # */ +#define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS) + +#endif /* CONFIG_SPARSEMEM */ + +/* + * page->flags layout: + * + * There are five possibilities for how page->flags get laid out. The first + * pair is for the normal case without sparsemem. The second pair is for + * sparsemem when there is plenty of space for node and section information. + * The last is when there is insufficient space in page->flags and a separate + * lookup is necessary. + * + * No sparsemem or sparsemem vmemmap: | NODE | ZONE | ... | FLAGS | + * " plus space for last_nid: | NODE | ZONE | LAST_NID ... | FLAGS | + * classic sparse with space for node:| SECTION | NODE | ZONE | ... | FLAGS | + * " plus space for last_nid: | SECTION | NODE | ZONE | LAST_NID ... | FLAGS | + * classic sparse no space for node: | SECTION | ZONE | ... | FLAGS | + */ +#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP) +#define SECTIONS_WIDTH SECTIONS_SHIFT +#else +#define SECTIONS_WIDTH 0 +#endif + +#define ZONES_WIDTH ZONES_SHIFT + +#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS +#define NODES_WIDTH NODES_SHIFT +#else +#ifdef CONFIG_SPARSEMEM_VMEMMAP +#error "Vmemmap: No space for nodes field in page flags" +#endif +#define NODES_WIDTH 0 +#endif + +#ifdef CONFIG_NUMA_BALANCING +#define LAST_NID_SHIFT NODES_SHIFT +#else +#define LAST_NID_SHIFT 0 +#endif + +#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_NID_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS +#define LAST_NID_WIDTH LAST_NID_SHIFT +#else +#define LAST_NID_WIDTH 0 +#endif + +/* + * We are going to use the flags for the page to node mapping if its in + * there. This includes the case where there is no node, so it is implicit. + */ +#if !(NODES_WIDTH > 0 || NODES_SHIFT == 0) +#define NODE_NOT_IN_PAGE_FLAGS +#endif + +#if defined(CONFIG_NUMA_BALANCING) && LAST_NID_WIDTH == 0 +#define LAST_NID_NOT_IN_PAGE_FLAGS +#endif + +#endif /* _LINUX_PAGE_FLAGS_LAYOUT */ |