xref: /openbmc/linux/mm/Kconfig (revision 643d1f7f) 
1config SELECT_MEMORY_MODEL
2	def_bool y
3	depends on EXPERIMENTAL || ARCH_SELECT_MEMORY_MODEL
4
5choice
6	prompt "Memory model"
7	depends on SELECT_MEMORY_MODEL
8	default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
9	default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
10	default FLATMEM_MANUAL
11
12config FLATMEM_MANUAL
13	bool "Flat Memory"
14	depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
15	help
16	  This option allows you to change some of the ways that
17	  Linux manages its memory internally.  Most users will
18	  only have one option here: FLATMEM.  This is normal
19	  and a correct option.
20
21	  Some users of more advanced features like NUMA and
22	  memory hotplug may have different options here.
23	  DISCONTIGMEM is an more mature, better tested system,
24	  but is incompatible with memory hotplug and may suffer
25	  decreased performance over SPARSEMEM.  If unsure between
26	  "Sparse Memory" and "Discontiguous Memory", choose
27	  "Discontiguous Memory".
28
29	  If unsure, choose this option (Flat Memory) over any other.
30
31config DISCONTIGMEM_MANUAL
32	bool "Discontiguous Memory"
33	depends on ARCH_DISCONTIGMEM_ENABLE
34	help
35	  This option provides enhanced support for discontiguous
36	  memory systems, over FLATMEM.  These systems have holes
37	  in their physical address spaces, and this option provides
38	  more efficient handling of these holes.  However, the vast
39	  majority of hardware has quite flat address spaces, and
40	  can have degraded performance from the extra overhead that
41	  this option imposes.
42
43	  Many NUMA configurations will have this as the only option.
44
45	  If unsure, choose "Flat Memory" over this option.
46
47config SPARSEMEM_MANUAL
48	bool "Sparse Memory"
49	depends on ARCH_SPARSEMEM_ENABLE
50	help
51	  This will be the only option for some systems, including
52	  memory hotplug systems.  This is normal.
53
54	  For many other systems, this will be an alternative to
55	  "Discontiguous Memory".  This option provides some potential
56	  performance benefits, along with decreased code complexity,
57	  but it is newer, and more experimental.
58
59	  If unsure, choose "Discontiguous Memory" or "Flat Memory"
60	  over this option.
61
62endchoice
63
64config DISCONTIGMEM
65	def_bool y
66	depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
67
68config SPARSEMEM
69	def_bool y
70	depends on SPARSEMEM_MANUAL
71
72config FLATMEM
73	def_bool y
74	depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
75
76config FLAT_NODE_MEM_MAP
77	def_bool y
78	depends on !SPARSEMEM
79
80#
81# Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
82# to represent different areas of memory.  This variable allows
83# those dependencies to exist individually.
84#
85config NEED_MULTIPLE_NODES
86	def_bool y
87	depends on DISCONTIGMEM || NUMA
88
89config HAVE_MEMORY_PRESENT
90	def_bool y
91	depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
92
93#
94# SPARSEMEM_EXTREME (which is the default) does some bootmem
95# allocations when memory_present() is called.  If this cannot
96# be done on your architecture, select this option.  However,
97# statically allocating the mem_section[] array can potentially
98# consume vast quantities of .bss, so be careful.
99#
100# This option will also potentially produce smaller runtime code
101# with gcc 3.4 and later.
102#
103config SPARSEMEM_STATIC
104	def_bool n
105
106#
107# Architecture platforms which require a two level mem_section in SPARSEMEM
108# must select this option. This is usually for architecture platforms with
109# an extremely sparse physical address space.
110#
111config SPARSEMEM_EXTREME
112	def_bool y
113	depends on SPARSEMEM && !SPARSEMEM_STATIC
114
115config SPARSEMEM_VMEMMAP_ENABLE
116	def_bool n
117
118config SPARSEMEM_VMEMMAP
119	bool "Sparse Memory virtual memmap"
120	depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
121	default y
122	help
123	 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
124	 pfn_to_page and page_to_pfn operations.  This is the most
125	 efficient option when sufficient kernel resources are available.
126
127# eventually, we can have this option just 'select SPARSEMEM'
128config MEMORY_HOTPLUG
129	bool "Allow for memory hot-add"
130	depends on SPARSEMEM || X86_64_ACPI_NUMA
131	depends on HOTPLUG && !HIBERNATION && ARCH_ENABLE_MEMORY_HOTPLUG
132	depends on (IA64 || X86 || PPC64 || SUPERH)
133
134comment "Memory hotplug is currently incompatible with Software Suspend"
135	depends on SPARSEMEM && HOTPLUG && HIBERNATION
136
137config MEMORY_HOTPLUG_SPARSE
138	def_bool y
139	depends on SPARSEMEM && MEMORY_HOTPLUG
140
141config MEMORY_HOTREMOVE
142	bool "Allow for memory hot remove"
143	depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
144	depends on MIGRATION
145
146# Heavily threaded applications may benefit from splitting the mm-wide
147# page_table_lock, so that faults on different parts of the user address
148# space can be handled with less contention: split it at this NR_CPUS.
149# Default to 4 for wider testing, though 8 might be more appropriate.
150# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
151# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
152#
153config SPLIT_PTLOCK_CPUS
154	int
155	default "4096" if ARM && !CPU_CACHE_VIPT
156	default "4096" if PARISC && !PA20
157	default "4"
158
159#
160# support for page migration
161#
162config MIGRATION
163	bool "Page migration"
164	def_bool y
165	depends on NUMA
166	help
167	  Allows the migration of the physical location of pages of processes
168	  while the virtual addresses are not changed. This is useful for
169	  example on NUMA systems to put pages nearer to the processors accessing
170	  the page.
171
172config RESOURCES_64BIT
173	bool "64 bit Memory and IO resources (EXPERIMENTAL)" if (!64BIT && EXPERIMENTAL)
174	default 64BIT
175	help
176	  This option allows memory and IO resources to be 64 bit.
177
178config ZONE_DMA_FLAG
179	int
180	default "0" if !ZONE_DMA
181	default "1"
182
183config BOUNCE
184	def_bool y
185	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
186
187config NR_QUICK
188	int
189	depends on QUICKLIST
190	default "2" if SUPERH
191	default "1"
192
193config VIRT_TO_BUS
194	def_bool y
195	depends on !ARCH_NO_VIRT_TO_BUS
196