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 #
  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         bool
 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 config SPARSEMEM_VMEMMAP_ENABLE
 116         bool
 117
 118 config SPARSEMEM_VMEMMAP
 119         bool "Sparse Memory virtual memmap"
 120         depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
 121         default y
 122         help
 123          SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
 124          pfn_to_page and page_to_pfn operations.  This is the most
 125          efficient option when sufficient kernel resources are available.
 126
 127 # eventually, we can have this option just 'select SPARSEMEM'
 128 config MEMORY_HOTPLUG
 129         bool "Allow for memory hot-add"
 130         depends on SPARSEMEM || X86_64_ACPI_NUMA
 131         depends on HOTPLUG && !HIBERNATION && ARCH_ENABLE_MEMORY_HOTPLUG
 132         depends on (IA64 || X86 || PPC64 || SUPERH || S390)
 133
 134 comment "Memory hotplug is currently incompatible with Software Suspend"
 135         depends on SPARSEMEM && HOTPLUG && HIBERNATION
 136
 137 config MEMORY_HOTPLUG_SPARSE
 138         def_bool y
 139         depends on SPARSEMEM && MEMORY_HOTPLUG
 140
 141 config MEMORY_HOTREMOVE
 142         bool "Allow for memory hot remove"
 143         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 144         depends on MIGRATION
 145
 146 #
 147 # If we have space for more page flags then we can enable additional
 148 # optimizations and functionality.
 149 #
 150 # Regular Sparsemem takes page flag bits for the sectionid if it does not
 151 # use a virtual memmap. Disable extended page flags for 32 bit platforms
 152 # that require the use of a sectionid in the page flags.
 153 #
 154 config PAGEFLAGS_EXTENDED
 155         def_bool y
 156         depends on 64BIT || SPARSEMEM_VMEMMAP || !NUMA || !SPARSEMEM
 157
 158 # Heavily threaded applications may benefit from splitting the mm-wide
 159 # page_table_lock, so that faults on different parts of the user address
 160 # space can be handled with less contention: split it at this NR_CPUS.
 161 # Default to 4 for wider testing, though 8 might be more appropriate.
 162 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 163 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 164 #
 165 config SPLIT_PTLOCK_CPUS
 166         int
 167         default "4096" if ARM && !CPU_CACHE_VIPT
 168         default "4096" if PARISC && !PA20
 169         default "4"
 170
 171 #
 172 # support for page migration
 173 #
 174 config MIGRATION
 175         bool "Page migration"
 176         def_bool y
 177         depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
 178         help
 179           Allows the migration of the physical location of pages of processes
 180           while the virtual addresses are not changed. This is useful for
 181           example on NUMA systems to put pages nearer to the processors accessing
 182           the page.
 183
 184 config RESOURCES_64BIT
 185         bool "64 bit Memory and IO resources (EXPERIMENTAL)" if (!64BIT && EXPERIMENTAL)
 186         default 64BIT
 187         help
 188           This option allows memory and IO resources to be 64 bit.
 189
 190 config PHYS_ADDR_T_64BIT
 191         def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
 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
 211
 212 config UNEVICTABLE_LRU
 213         bool "Add LRU list to track non-evictable pages"
 214         default y
 215         depends on MMU
 216         help
 217           Keeps unevictable pages off of the active and inactive pageout
 218           lists, so kswapd will not waste CPU time or have its balancing
 219           algorithms thrown off by scanning these pages.  Selecting this
 220           will use one page flag and increase the code size a little,
 221           say Y unless you know what you are doing.
 222
 223 config MMU_NOTIFIER
 224         bool