mm/Kconfig

   1 config SELECT_MEMORY_MODEL
   2         def_bool y
   3         depends on EXPERIMENTAL || ARCH_SELECT_MEMORY_MODEL
   4
   5 choice
   6         prompt "Memory model"
   7         depends on SELECT_MEMORY_MODEL
   8         default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
   9         default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
  10         default FLATMEM_MANUAL
  11
  12 config FLATMEM_MANUAL
  13         bool "Flat Memory"
  14         depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
  15         help
  16           This option allows you to change some of the ways that
  17           Linux manages its memory internally.  Most users will
  18           only have one option here: FLATMEM.  This is normal
  19           and a correct option.
  20
  21           Some users of more advanced features like NUMA and
  22           memory hotplug may have different options here.
  23           DISCONTIGMEM is an more mature, better tested system,
  24           but is incompatible with memory hotplug and may suffer
  25           decreased performance over SPARSEMEM.  If unsure between
  26           "Sparse Memory" and "Discontiguous Memory", choose
  27           "Discontiguous Memory".
  28
  29           If unsure, choose this option (Flat Memory) over any other.
  30
  31 config DISCONTIGMEM_MANUAL
  32         bool "Discontiguous Memory"
  33         depends on ARCH_DISCONTIGMEM_ENABLE
  34         help
  35           This option provides enhanced support for discontiguous
  36           memory systems, over FLATMEM.  These systems have holes
  37           in their physical address spaces, and this option provides
  38           more efficient handling of these holes.  However, the vast
  39           majority of hardware has quite flat address spaces, and
  40           can have degraded performance from extra overhead that
  41           this option imposes.
  42
  43           Many NUMA configurations will have this as the only option.
  44
  45           If unsure, choose "Flat Memory" over this option.
  46
  47 config SPARSEMEM_MANUAL
  48         bool "Sparse Memory"
  49         depends on ARCH_SPARSEMEM_ENABLE
  50         help
  51           This will be the only option for some systems, including
  52           memory hotplug systems.  This is normal.
  53
  54           For many other systems, this will be an alternative to
  55           "Discontiguous Memory".  This option provides some potential
  56           performance benefits, along with decreased code complexity,
  57           but it is newer, and more experimental.
  58
  59           If unsure, choose "Discontiguous Memory" or "Flat Memory"
  60           over this option.
  61
  62 endchoice
  63
  64 config DISCONTIGMEM
  65         def_bool y
  66         depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
  67
  68 config SPARSEMEM
  69         def_bool y
  70         depends on SPARSEMEM_MANUAL
  71
  72 config FLATMEM
  73         def_bool y
  74         depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
  75
  76 config FLAT_NODE_MEM_MAP
  77         def_bool y
  78         depends on !SPARSEMEM
  79
  80 #
  81 # Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
  82 # to represent different areas of memory.  This variable allows
  83 # those dependencies to exist individually.
  84 #
  85 config NEED_MULTIPLE_NODES
  86         def_bool y
  87         depends on DISCONTIGMEM || NUMA
  88
  89 config HAVE_MEMORY_PRESENT
  90         def_bool y
  91         depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
  92
  93 #
  94 # SPARSEMEM_EXTREME (which is the default) does some bootmem
  95 # allocations when memory_present() is called.  If this cannot
  96 # be done on your architecture, select this option.  However,
  97 # statically allocating the mem_section[] array can potentially
  98 # consume vast quantities of .bss, so be careful.
  99 #
 100 # This option will also potentially produce smaller runtime code
 101 # with gcc 3.4 and later.
 102 #
 103 config SPARSEMEM_STATIC
 104         def_bool n
 105
 106 #
 107 # Architecture platforms which require a two level mem_section in SPARSEMEM
 108 # must select this option. This is usually for architecture platforms with
 109 # an extremely sparse physical address space.
 110 #
 111 config SPARSEMEM_EXTREME
 112         def_bool y
 113         depends on SPARSEMEM && !SPARSEMEM_STATIC
 114
 115 #
 116 # SPARSEMEM_VMEMMAP uses a virtually mapped mem_map to optimise pfn_to_page
 117 # and page_to_pfn.  The most efficient option where kernel virtual space is
 118 # not under pressure.
 119 #
 120 config SPARSEMEM_VMEMMAP_ENABLE
 121         def_bool n
 122
 123 config SPARSEMEM_VMEMMAP
 124         bool
 125         depends on SPARSEMEM
 126         default y if (SPARSEMEM_VMEMMAP_ENABLE)
 127
 128 # eventually, we can have this option just 'select SPARSEMEM'
 129 config MEMORY_HOTPLUG
 130         bool "Allow for memory hot-add"
 131         depends on SPARSEMEM || X86_64_ACPI_NUMA
 132         depends on HOTPLUG && !HIBERNATION && ARCH_ENABLE_MEMORY_HOTPLUG
 133         depends on (IA64 || X86 || PPC64 || SUPERH)
 134
 135 comment "Memory hotplug is currently incompatible with Software Suspend"
 136         depends on SPARSEMEM && HOTPLUG && HIBERNATION
 137
 138 config MEMORY_HOTPLUG_SPARSE
 139         def_bool y
 140         depends on SPARSEMEM && MEMORY_HOTPLUG
 141
 142 # Heavily threaded applications may benefit from splitting the mm-wide
 143 # page_table_lock, so that faults on different parts of the user address
 144 # space can be handled with less contention: split it at this NR_CPUS.
 145 # Default to 4 for wider testing, though 8 might be more appropriate.
 146 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 147 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 148 #
 149 config SPLIT_PTLOCK_CPUS
 150         int
 151         default "4096" if ARM && !CPU_CACHE_VIPT
 152         default "4096" if PARISC && !PA20
 153         default "4096" if XEN
 154         default "4"
 155
 156 #
 157 # support for page migration
 158 #
 159 config MIGRATION
 160         bool "Page migration"
 161         def_bool y
 162         depends on NUMA
 163         help
 164           Allows the migration of the physical location of pages of processes
 165           while the virtual addresses are not changed. This is useful for
 166           example on NUMA systems to put pages nearer to the processors accessing
 167           the page.
 168
 169 config RESOURCES_64BIT
 170         bool "64 bit Memory and IO resources (EXPERIMENTAL)" if (!64BIT && EXPERIMENTAL)
 171         default 64BIT
 172         help
 173           This option allows memory and IO resources to be 64 bit.
 174
 175 config ZONE_DMA_FLAG
 176         int
 177         default "0" if !ZONE_DMA
 178         default "1"
 179
 180 config BOUNCE
 181         def_bool y
 182         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 183
 184 config NR_QUICK
 185         int
 186         depends on QUICKLIST
 187         default "2" if (SUPERH && !SUPERH64)
 188         default "1"
 189
 190 config VIRT_TO_BUS
 191         def_bool y
 192         depends on !ARCH_NO_VIRT_TO_BUS