include/linux/page-flags-layout.h

   1 #ifndef PAGE_FLAGS_LAYOUT_H
   2 #define PAGE_FLAGS_LAYOUT_H
   3
   4 #include <linux/numa.h>
   5 #include <generated/bounds.h>
   6
   7 /*
   8  * When a memory allocation must conform to specific limitations (such
   9  * as being suitable for DMA) the caller will pass in hints to the
  10  * allocator in the gfp_mask, in the zone modifier bits.  These bits
  11  * are used to select a priority ordered list of memory zones which
  12  * match the requested limits. See gfp_zone() in include/linux/gfp.h
  13  */
  14 #if MAX_NR_ZONES < 2
  15 #define ZONES_SHIFT 0
  16 #elif MAX_NR_ZONES <= 2
  17 #define ZONES_SHIFT 1
  18 #elif MAX_NR_ZONES <= 4
  19 #define ZONES_SHIFT 2
  20 #elif MAX_NR_ZONES <= 8
  21 #define ZONES_SHIFT 3
  22 #else
  23 #error ZONES_SHIFT -- too many zones configured adjust calculation
  24 #endif
  25
  26 #ifdef CONFIG_SPARSEMEM
  27 #include <asm/sparsemem.h>
  28
  29 /* SECTION_SHIFT        #bits space required to store a section # */
  30 #define SECTIONS_SHIFT  (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS)
  31
  32 #endif /* CONFIG_SPARSEMEM */
  33
  34 /*
  35  * page->flags layout:
  36  *
  37  * There are five possibilities for how page->flags get laid out.  The first
  38  * pair is for the normal case without sparsemem. The second pair is for
  39  * sparsemem when there is plenty of space for node and section information.
  40  * The last is when there is insufficient space in page->flags and a separate
  41  * lookup is necessary.
  42  *
  43  * No sparsemem or sparsemem vmemmap: |       NODE     | ZONE |             ... | FLAGS |
  44  *      " plus space for last_cpupid: |       NODE     | ZONE | LAST_CPUPID ... | FLAGS |
  45  * classic sparse with space for node:| SECTION | NODE | ZONE |             ... | FLAGS |
  46  *      " plus space for last_cpupid: | SECTION | NODE | ZONE | LAST_CPUPID ... | FLAGS |
  47  * classic sparse no space for node:  | SECTION |     ZONE    | ... | FLAGS |
  48  */
  49 #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
  50 #define SECTIONS_WIDTH          SECTIONS_SHIFT
  51 #else
  52 #define SECTIONS_WIDTH          0
  53 #endif
  54
  55 #define ZONES_WIDTH             ZONES_SHIFT
  56
  57 #if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
  58 #define NODES_WIDTH             NODES_SHIFT
  59 #else
  60 #ifdef CONFIG_SPARSEMEM_VMEMMAP
  61 #error "Vmemmap: No space for nodes field in page flags"
  62 #endif
  63 #define NODES_WIDTH             0
  64 #endif
  65
  66 #ifdef CONFIG_NUMA_BALANCING
  67 #define LAST__PID_SHIFT 8
  68 #define LAST__PID_MASK  ((1 << LAST__PID_SHIFT)-1)
  69
  70 #define LAST__CPU_SHIFT NR_CPUS_BITS
  71 #define LAST__CPU_MASK  ((1 << LAST__CPU_SHIFT)-1)
  72
  73 #define LAST_CPUPID_SHIFT (LAST__PID_SHIFT+LAST__CPU_SHIFT)
  74 #else
  75 #define LAST_CPUPID_SHIFT 0
  76 #endif
  77
  78 #if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
  79 #define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
  80 #else
  81 #define LAST_CPUPID_WIDTH 0
  82 #endif
  83
  84 /*
  85  * We are going to use the flags for the page to node mapping if its in
  86  * there.  This includes the case where there is no node, so it is implicit.
  87  */
  88 #if !(NODES_WIDTH > 0 || NODES_SHIFT == 0)
  89 #define NODE_NOT_IN_PAGE_FLAGS
  90 #endif
  91
  92 #if defined(CONFIG_NUMA_BALANCING) && LAST_CPUPID_WIDTH == 0
  93 #define LAST_CPUPID_NOT_IN_PAGE_FLAGS
  94 #endif
  95
  96 #endif /* _LINUX_PAGE_FLAGS_LAYOUT */