Kconfig revision 1a83e175dc2c7be931a3ea9c7fb0769e6de55e90 
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 (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || 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	bool
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	bool
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 && !S390) && ARCH_ENABLE_MEMORY_HOTPLUG
132	depends on (IA64 || X86 || PPC64 || SUPERH || S390)
133
134comment "Memory hotplug is currently incompatible with Software Suspend"
135	depends on SPARSEMEM && HOTPLUG && HIBERNATION && !S390
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#
147# If we have space for more page flags then we can enable additional
148# optimizations and functionality.
149#
150# Regular Sparsemem takes page flag bits for the sectionid if it does not
151# use a virtual memmap. Disable extended page flags for 32 bit platforms
152# that require the use of a sectionid in the page flags.
153#
154config PAGEFLAGS_EXTENDED
155	def_bool y
156	depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
157
158# Heavily threaded applications may benefit from splitting the mm-wide
159# page_table_lock, so that faults on different parts of the user address
160# space can be handled with less contention: split it at this NR_CPUS.
161# Default to 4 for wider testing, though 8 might be more appropriate.
162# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
163# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
164#
165config SPLIT_PTLOCK_CPUS
166	int
167	default "4096" if ARM && !CPU_CACHE_VIPT
168	default "4096" if PARISC && !PA20
169	default "4"
170
171#
172# support for page migration
173#
174config MIGRATION
175	bool "Page migration"
176	def_bool y
177	depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
178	help
179	  Allows the migration of the physical location of pages of processes
180	  while the virtual addresses are not changed. This is useful for
181	  example on NUMA systems to put pages nearer to the processors accessing
182	  the page.
183
184config PHYS_ADDR_T_64BIT
185	def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
186
187config ZONE_DMA_FLAG
188	int
189	default "0" if !ZONE_DMA
190	default "1"
191
192config BOUNCE
193	def_bool y
194	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
195
196config NR_QUICK
197	int
198	depends on QUICKLIST
199	default "2" if SUPERH || AVR32
200	default "1"
201
202config VIRT_TO_BUS
203	def_bool y
204	depends on !ARCH_NO_VIRT_TO_BUS
205
206config HAVE_MLOCK
207	bool
208	default y if MMU=y
209
210config HAVE_MLOCKED_PAGE_BIT
211	bool
212	default y if HAVE_MLOCK=y
213
214config MMU_NOTIFIER
215	bool
216
217config KSM
218	bool "Enable KSM for page merging"
219	depends on MMU
220	help
221	  Enable Kernel Samepage Merging: KSM periodically scans those areas
222	  of an application's address space that an app has advised may be
223	  mergeable.  When it finds pages of identical content, it replaces
224	  the many instances by a single resident page with that content, so
225	  saving memory until one or another app needs to modify the content.
226	  Recommended for use with KVM, or with other duplicative applications.
227	  See Documentation/vm/ksm.txt for more information: KSM is inactive
228	  until a program has madvised that an area is MADV_MERGEABLE, and
229	  root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
230
231config DEFAULT_MMAP_MIN_ADDR
232        int "Low address space to protect from user allocation"
233        default 4096
234        help
235	  This is the portion of low virtual memory which should be protected
236	  from userspace allocation.  Keeping a user from writing to low pages
237	  can help reduce the impact of kernel NULL pointer bugs.
238
239	  For most ia64, ppc64 and x86 users with lots of address space
240	  a value of 65536 is reasonable and should cause no problems.
241	  On arm and other archs it should not be higher than 32768.
242	  Programs which use vm86 functionality or have some need to map
243	  this low address space will need CAP_SYS_RAWIO or disable this
244	  protection by setting the value to 0.
245
246	  This value can be changed after boot using the
247	  /proc/sys/vm/mmap_min_addr tunable.
248
249config ARCH_SUPPORTS_MEMORY_FAILURE
250	bool
251
252config MEMORY_FAILURE
253	depends on MMU
254	depends on ARCH_SUPPORTS_MEMORY_FAILURE
255	bool "Enable recovery from hardware memory errors"
256	help
257	  Enables code to recover from some memory failures on systems
258	  with MCA recovery. This allows a system to continue running
259	  even when some of its memory has uncorrected errors. This requires
260	  special hardware support and typically ECC memory.
261
262config HWPOISON_INJECT
263	tristate "Poison pages injector"
264	depends on MEMORY_FAILURE && DEBUG_KERNEL
265
266config NOMMU_INITIAL_TRIM_EXCESS
267	int "Turn on mmap() excess space trimming before booting"
268	depends on !MMU
269	default 1
270	help
271	  The NOMMU mmap() frequently needs to allocate large contiguous chunks
272	  of memory on which to store mappings, but it can only ask the system
273	  allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
274	  more than it requires.  To deal with this, mmap() is able to trim off
275	  the excess and return it to the allocator.
276
277	  If trimming is enabled, the excess is trimmed off and returned to the
278	  system allocator, which can cause extra fragmentation, particularly
279	  if there are a lot of transient processes.
280
281	  If trimming is disabled, the excess is kept, but not used, which for
282	  long-term mappings means that the space is wasted.
283
284	  Trimming can be dynamically controlled through a sysctl option
285	  (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
286	  excess pages there must be before trimming should occur, or zero if
287	  no trimming is to occur.
288
289	  This option specifies the initial value of this option.  The default
290	  of 1 says that all excess pages should be trimmed.
291
292	  See Documentation/nommu-mmap.txt for more information.
293