The patch titled
Subject: mm/Kconfig: update "Memory Model" help text
has been added to the -mm tree. Its filename is
mm-kconfig-update-memory-model-help-text.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-kconfig-update-memory-model-help-text.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-kconfig-update-memory-model-help-text.patch
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------------------------------------------------------
From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Subject: mm/Kconfig: update "Memory Model" help text
The help describing the memory model selection is outdated. It still says
that SPARSEMEM is experimental and DISCONTIGMEM is a preferred over
SPARSEMEM.
Update the help text for the relevant options:
* add a generic help for the "Memory Model" prompt
* add description for FLATMEM
* reduce the description of DISCONTIGMEM and add a deprecation note
* prefer SPARSEMEM over DISCONTIGMEM
Link: http://lkml.kernel.org/r/1556188531-20728-1-git-send-email-rppt@xxxxxxxxxxxxx
Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/Kconfig | 48 +++++++++++++++++++++++-------------------------
1 file changed, 23 insertions(+), 25 deletions(-)
--- a/mm/Kconfig~mm-kconfig-update-memory-model-help-text
+++ a/mm/Kconfig
@@ -11,23 +11,24 @@ choice
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.
@@ -38,29 +39,26 @@ config DISCONTIGMEM_MANUAL
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
_
Patches currently in -mm which might be from rppt@xxxxxxxxxxxxx are
init-provide-a-generic-free_initmem-implementation.patch
hexagon-switch-over-to-generic-free_initmem.patch
init-free_initmem-poison-freed-init-memory.patch
riscv-switch-over-to-generic-free_initmem.patch
memblock-make-keeping-memblock-memory-opt-in-rather-than-opt-out.patch
mm-kconfig-update-memory-model-help-text.patch
