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The help describing the memory model selection is outdated.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@linux.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/Kconfig b/mm/Kconfig
index c5124c2cb0b2508fe5dee863cbc0eaa16152804b..ee8d1f311858833c56ffd96b6f61f0d5d1b9740b 100644 (file)
--- a/mm/Kconfig
+++ b/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