default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
default FLATMEM_MANUAL
+ 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 selected by the architecture
+ configuration. This is normal.
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 a 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".
+ This option is best suited for non-NUMA systems with
+ flat address space. The FLATMEM is the most efficient
+ system in terms of performance and resource consumption
+ and it is the best option for smaller systems.
+
+ For systems that have holes in their physical address
+ spaces and for features like NUMA and memory hotplug,
+ choose "Sparse Memory"
If unsure, choose this option (Flat Memory) over any other.
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 the extra overhead that
- this option imposes.
+ more efficient handling of these holes.
- Many NUMA configurations will have this as the only option.
+ Although "Discontiguous Memory" is still used by several
+ architectures, it is considered deprecated in favor of
+ "Sparse Memory".
- If unsure, choose "Flat Memory" over this option.
+ If unsure, choose "Sparse 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.
+ memory hot-plug 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.
+ This option provides efficient support for systems with
+ holes is their physical address space and allows memory
+ hot-plug and hot-remove.
- If unsure, choose "Discontiguous Memory" or "Flat Memory"
- over this option.
+ If unsure, choose "Flat Memory" over this option.
endchoice