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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_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 "Discontigious 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
"Discontigious 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 can not
# 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
#
# Architectecture 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
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