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 the 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 config HAVE_GET_USER_PAGES_FAST
  81         bool
  82
  83 #
  84 # Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
  85 # to represent different areas of memory.  This variable allows
  86 # those dependencies to exist individually.
  87 #
  88 config NEED_MULTIPLE_NODES
  89         def_bool y
  90         depends on DISCONTIGMEM || NUMA
  91
  92 config HAVE_MEMORY_PRESENT
  93         def_bool y
  94         depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
  95
  96 #
  97 # SPARSEMEM_EXTREME (which is the default) does some bootmem
  98 # allocations when memory_present() is called.  If this cannot
  99 # be done on your architecture, select this option.  However,
 100 # statically allocating the mem_section[] array can potentially
 101 # consume vast quantities of .bss, so be careful.
 102 #
 103 # This option will also potentially produce smaller runtime code
 104 # with gcc 3.4 and later.
 105 #
 106 config SPARSEMEM_STATIC
 107         def_bool n
 108
 109 #
 110 # Architecture platforms which require a two level mem_section in SPARSEMEM
 111 # must select this option. This is usually for architecture platforms with
 112 # an extremely sparse physical address space.
 113 #
 114 config SPARSEMEM_EXTREME
 115         def_bool y
 116         depends on SPARSEMEM && !SPARSEMEM_STATIC
 117
 118 config SPARSEMEM_VMEMMAP_ENABLE
 119         def_bool n
 120
 121 config SPARSEMEM_VMEMMAP
 122         bool "Sparse Memory virtual memmap"
 123         depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
 124         default y
 125         help
 126          SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
 127          pfn_to_page and page_to_pfn operations.  This is the most
 128          efficient option when sufficient kernel resources are available.
 129
 130 # eventually, we can have this option just 'select SPARSEMEM'
 131 config MEMORY_HOTPLUG
 132         bool "Allow for memory hot-add"
 133         depends on SPARSEMEM || X86_64_ACPI_NUMA
 134         depends on HOTPLUG && !HIBERNATION && ARCH_ENABLE_MEMORY_HOTPLUG
 135         depends on (IA64 || X86 || PPC64 || SUPERH || S390)
 136
 137 comment "Memory hotplug is currently incompatible with Software Suspend"
 138         depends on SPARSEMEM && HOTPLUG && HIBERNATION
 139
 140 config MEMORY_HOTPLUG_SPARSE
 141         def_bool y
 142         depends on SPARSEMEM && MEMORY_HOTPLUG
 143
 144 config MEMORY_HOTREMOVE
 145         bool "Allow for memory hot remove"
 146         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 147         depends on MIGRATION
 148
 149 #
 150 # If we have space for more page flags then we can enable additional
 151 # optimizations and functionality.
 152 #
 153 # Regular Sparsemem takes page flag bits for the sectionid if it does not
 154 # use a virtual memmap. Disable extended page flags for 32 bit platforms
 155 # that require the use of a sectionid in the page flags.
 156 #
 157 config PAGEFLAGS_EXTENDED
 158         def_bool y
 159         depends on 64BIT || SPARSEMEM_VMEMMAP || !NUMA || !SPARSEMEM
 160
 161 # Heavily threaded applications may benefit from splitting the mm-wide
 162 # page_table_lock, so that faults on different parts of the user address
 163 # space can be handled with less contention: split it at this NR_CPUS.
 164 # Default to 4 for wider testing, though 8 might be more appropriate.
 165 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 166 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 167 #
 168 config SPLIT_PTLOCK_CPUS
 169         int
 170         default "4096" if ARM && !CPU_CACHE_VIPT
 171         default "4096" if PARISC && !PA20
 172         default "4"
 173
 174 #
 175 # support for page migration
 176 #
 177 config MIGRATION
 178         bool "Page migration"
 179         def_bool y
 180         depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
 181         help
 182           Allows the migration of the physical location of pages of processes
 183           while the virtual addresses are not changed. This is useful for
 184           example on NUMA systems to put pages nearer to the processors accessing
 185           the page.
 186
 187 config RESOURCES_64BIT
 188         bool "64 bit Memory and IO resources (EXPERIMENTAL)" if (!64BIT && EXPERIMENTAL)
 189         default 64BIT
 190         help
 191           This option allows memory and IO resources to be 64 bit.
 192
 193 config ZONE_DMA_FLAG
 194         int
 195         default "0" if !ZONE_DMA
 196         default "1"
 197
 198 config BOUNCE
 199         def_bool y
 200         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 201
 202 config NR_QUICK
 203         int
 204         depends on QUICKLIST
 205         default "2" if SUPERH || AVR32
 206         default "1"
 207
 208 config VIRT_TO_BUS
 209         def_bool y
 210         depends on !ARCH_NO_VIRT_TO_BUS