LXR linux/include/linux/page-flags-layout.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   2#ifndef PAGE_FLAGS_LAYOUT_H
   3#define PAGE_FLAGS_LAYOUT_H
   4
   5#include <linux/numa.h>
   6#include <generated/bounds.h>
   7
   8/*
   9 * When a memory allocation must conform to specific limitations (such
  10 * as being suitable for DMA) the caller will pass in hints to the
  11 * allocator in the gfp_mask, in the zone modifier bits.  These bits
  12 * are used to select a priority ordered list of memory zones which
  13 * match the requested limits. See gfp_zone() in include/linux/gfp.h
  14 */
  15#if MAX_NR_ZONES < 2
  16#define ZONES_SHIFT 0
  17#elif MAX_NR_ZONES <= 2
  18#define ZONES_SHIFT 1
  19#elif MAX_NR_ZONES <= 4
  20#define ZONES_SHIFT 2
  21#elif MAX_NR_ZONES <= 8
  22#define ZONES_SHIFT 3
  23#else
  24#error ZONES_SHIFT -- too many zones configured adjust calculation
  25#endif
  26
  27#ifdef CONFIG_SPARSEMEM
  28#include <asm/sparsemem.h>
  29
  30/* SECTION_SHIFT        #bits space required to store a section # */
  31#define SECTIONS_SHIFT  (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS)
  32
  33#endif /* CONFIG_SPARSEMEM */
  34
  35/*
  36 * page->flags layout:
  37 *
  38 * There are five possibilities for how page->flags get laid out.  The first
  39 * pair is for the normal case without sparsemem. The second pair is for
  40 * sparsemem when there is plenty of space for node and section information.
  41 * The last is when there is insufficient space in page->flags and a separate
  42 * lookup is necessary.
  43 *
  44 * No sparsemem or sparsemem vmemmap: |       NODE     | ZONE |             ... | FLAGS |
  45 *      " plus space for last_cpupid: |       NODE     | ZONE | LAST_CPUPID ... | FLAGS |
  46 * classic sparse with space for node:| SECTION | NODE | ZONE |             ... | FLAGS |
  47 *      " plus space for last_cpupid: | SECTION | NODE | ZONE | LAST_CPUPID ... | FLAGS |
  48 * classic sparse no space for node:  | SECTION |     ZONE    | ... | FLAGS |
  49 */
  50#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
  51#define SECTIONS_WIDTH          SECTIONS_SHIFT
  52#else
  53#define SECTIONS_WIDTH          0
  54#endif
  55
  56#define ZONES_WIDTH             ZONES_SHIFT
  57
  58#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
  59#define NODES_WIDTH             NODES_SHIFT
  60#else
  61#ifdef CONFIG_SPARSEMEM_VMEMMAP
  62#error "Vmemmap: No space for nodes field in page flags"
  63#endif
  64#define NODES_WIDTH             0
  65#endif
  66
  67#ifdef CONFIG_NUMA_BALANCING
  68#define LAST__PID_SHIFT 8
  69#define LAST__PID_MASK  ((1 << LAST__PID_SHIFT)-1)
  70
  71#define LAST__CPU_SHIFT NR_CPUS_BITS
  72#define LAST__CPU_MASK  ((1 << LAST__CPU_SHIFT)-1)
  73
  74#define LAST_CPUPID_SHIFT (LAST__PID_SHIFT+LAST__CPU_SHIFT)
  75#else
  76#define LAST_CPUPID_SHIFT 0
  77#endif
  78
  79#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
  80#define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
  81#else
  82#define LAST_CPUPID_WIDTH 0
  83#endif
  84
  85/*
  86 * We are going to use the flags for the page to node mapping if its in
  87 * there.  This includes the case where there is no node, so it is implicit.
  88 */
  89#if !(NODES_WIDTH > 0 || NODES_SHIFT == 0)
  90#define NODE_NOT_IN_PAGE_FLAGS
  91#endif
  92
  93#if defined(CONFIG_NUMA_BALANCING) && LAST_CPUPID_WIDTH == 0
  94#define LAST_CPUPID_NOT_IN_PAGE_FLAGS
  95#endif
  96
  97#endif /* _LINUX_PAGE_FLAGS_LAYOUT */
  98