Re: [PATCH 1/4] create mm/Kconfig for arch-independent memory options

[Dave Hansen <haveblue@us.ibm.com>]

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Hi Roman,

How does the attached patch look?  It will still give us the flexibility
to override the memory models, but only in the presence of
CONFIG_EXPERIMENTAL.

It also adds some better help text to the DISCONTIGMEM menu.  Is that
something like what you were looking  for?

-- Dave

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---

 memhotplug-dave/mm/Kconfig |   27 +++++++++++++++++++++++----
 1 files changed, 23 insertions(+), 4 deletions(-)

diff -puN mm/Kconfig~Kconfig-experimenta mm/Kconfig
--- memhotplug/mm/Kconfig~Kconfig-experimenta	2005-04-07 09:24:59.000000000 -0700
+++ memhotplug-dave/mm/Kconfig	2005-04-07 09:32:06.000000000 -0700
@@ -1,9 +1,10 @@
 choice
 	prompt "Memory model"
-	default DISCONTIGMEM if ARCH_DISCONTIGMEM_DEFAULT
-	default FLATMEM
+	depends on EXPERIMENTAL
+	default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
+	default FLATMEM_MANUAL
 
-config FLATMEM
+config FLATMEM_MANUAL
 	bool "Flat Memory"
 	depends on !ARCH_DISCONTIGMEM_ENABLE || ARCH_FLATMEM_ENABLE
 	help
@@ -14,14 +15,32 @@ config FLATMEM
 
 	  If unsure, choose this option over any other.
 
-config DISCONTIGMEM
+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.
 
 endchoice
 
+config DISCONTIGMEM
+	def_bool y
+	depends on (!EXPERIMENTAL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
+
+config FLATMEM
+	def_bool y
+	depends on !DISCONTIGMEM || FLATMEM_MANUAL
+
 #
 # Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
 # to represent different areas of memory.  This variable allows
_