linux-imx/mm/Kconfig

config SELECT_MEMORY_MODEL def_bool y depends on EXPERIMENTAL || ARCH_SELECT_MEMORY_MODEL

choice prompt "Memory model" depends on SELECT_MEMORY_MODEL default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT default FLATMEM_MANUAL

config FLATMEM_MANUAL bool "Flat Memory" depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE help This option allows you to change some of the ways that Linux manages its memory internally. Most users will only have one option here: FLATMEM. This is normal and a correct option.

  Some users of more advanced features like NUMA and
  memory hotplug may have different options here.
  DISCONTIGMEM is an more mature, better tested system,
  but is incompatible with memory hotplug and may suffer
  decreased performance over SPARSEMEM.  If unsure between
  "Sparse Memory" and "Discontiguous Memory", choose
  "Discontiguous Memory".

  If unsure, choose this option (Flat Memory) over any other.

config DISCONTIGMEM_MANUAL bool "Discontiguous Memory" depends on ARCH_DISCONTIGMEM_ENABLE help This option provides enhanced support for discontiguous memory systems, over FLATMEM. These systems have holes in their physical address spaces, and this option provides more efficient handling of these holes. However, the vast majority of hardware has quite flat address spaces, and can have degraded performance from extra overhead that this option imposes.

  Many NUMA configurations will have this as the only option.

  If unsure, choose "Flat Memory" over this option.

config SPARSEMEM_MANUAL bool "Sparse Memory" depends on ARCH_SPARSEMEM_ENABLE help This will be the only option for some systems, including memory hotplug systems. This is normal.

  For many other systems, this will be an alternative to
  "Discontiguous Memory".  This option provides some potential
  performance benefits, along with decreased code complexity,
  but it is newer, and more experimental.

  If unsure, choose "Discontiguous Memory" or "Flat Memory"
  over this option.

endchoice

config DISCONTIGMEM def_bool y depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL

config SPARSEMEM def_bool y depends on SPARSEMEM_MANUAL

config FLATMEM def_bool y depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL

config FLAT_NODE_MEM_MAP def_bool y depends on !SPARSEMEM

Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's

to represent different areas of memory. This variable allows

those dependencies to exist individually.

config NEED_MULTIPLE_NODES def_bool y depends on DISCONTIGMEM || NUMA

config HAVE_MEMORY_PRESENT def_bool y depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM

SPARSEMEM_EXTREME (which is the default) does some bootmem

allocations when memory_present() is called. If this cannot

be done on your architecture, select this option. However,

statically allocating the mem_section[] array can potentially

consume vast quantities of .bss, so be careful.

This option will also potentially produce smaller runtime code

with gcc 3.4 and later.

config SPARSEMEM_STATIC def_bool n

Architecture platforms which require a two level mem_section in SPARSEMEM

must select this option. This is usually for architecture platforms with

an extremely sparse physical address space.

config SPARSEMEM_EXTREME def_bool y depends on SPARSEMEM && !SPARSEMEM_STATIC

eventually, we can have this option just 'select SPARSEMEM'

config MEMORY_HOTPLUG bool "Allow for memory hot-add" depends on SPARSEMEM || X86_64_ACPI_NUMA depends on HOTPLUG && !SOFTWARE_SUSPEND && ARCH_ENABLE_MEMORY_HOTPLUG depends on (IA64 || X86 || PPC64)

comment "Memory hotplug is currently incompatible with Software Suspend" depends on SPARSEMEM && HOTPLUG && SOFTWARE_SUSPEND

config MEMORY_HOTPLUG_SPARSE def_bool y depends on SPARSEMEM && MEMORY_HOTPLUG

Heavily threaded applications may benefit from splitting the mm-wide

page_table_lock, so that faults on different parts of the user address

space can be handled with less contention: split it at this NR_CPUS.

Default to 4 for wider testing, though 8 might be more appropriate.

ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.

PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.

config SPLIT_PTLOCK_CPUS int default "4096" if ARM && !CPU_CACHE_VIPT default "4096" if PARISC && !PA20 default "4"

support for page migration

config MIGRATION bool "Page migration" def_bool y depends on NUMA help Allows the migration of the physical location of pages of processes while the virtual addresses are not changed. This is useful for example on NUMA systems to put pages nearer to the processors accessing the page.

config RESOURCES_64BIT bool "64 bit Memory and IO resources (EXPERIMENTAL)" if (!64BIT && EXPERIMENTAL) default 64BIT help This option allows memory and IO resources to be 64 bit.