Kconfig revision 6e1415467614e854fee660ff6648bd10fa976e95 
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 && ARCH_ENABLE_MEMORY_HOTPLUG
132	depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
133
134config MEMORY_HOTPLUG_SPARSE
135	def_bool y
136	depends on SPARSEMEM && MEMORY_HOTPLUG
137
138config MEMORY_HOTREMOVE
139	bool "Allow for memory hot remove"
140	depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
141	depends on MIGRATION
142
143#
144# If we have space for more page flags then we can enable additional
145# optimizations and functionality.
146#
147# Regular Sparsemem takes page flag bits for the sectionid if it does not
148# use a virtual memmap. Disable extended page flags for 32 bit platforms
149# that require the use of a sectionid in the page flags.
150#
151config PAGEFLAGS_EXTENDED
152	def_bool y
153	depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
154
155# Heavily threaded applications may benefit from splitting the mm-wide
156# page_table_lock, so that faults on different parts of the user address
157# space can be handled with less contention: split it at this NR_CPUS.
158# Default to 4 for wider testing, though 8 might be more appropriate.
159# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
160# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
161# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
162#
163config SPLIT_PTLOCK_CPUS
164	int
165	default "999999" if ARM && !CPU_CACHE_VIPT
166	default "999999" if PARISC && !PA20
167	default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
168	default "4"
169
170#
171# support for page migration
172#
173config MIGRATION
174	bool "Page migration"
175	def_bool y
176	depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
177	help
178	  Allows the migration of the physical location of pages of processes
179	  while the virtual addresses are not changed. This is useful for
180	  example on NUMA systems to put pages nearer to the processors accessing
181	  the page.
182
183config PHYS_ADDR_T_64BIT
184	def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
185
186config ZONE_DMA_FLAG
187	int
188	default "0" if !ZONE_DMA
189	default "1"
190
191config BOUNCE
192	def_bool y
193	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
194
195config NR_QUICK
196	int
197	depends on QUICKLIST
198	default "2" if SUPERH || AVR32
199	default "1"
200
201config VIRT_TO_BUS
202	def_bool y
203	depends on !ARCH_NO_VIRT_TO_BUS
204
205config MMU_NOTIFIER
206	bool
207
208config KSM
209	bool "Enable KSM for page merging"
210	depends on MMU
211	help
212	  Enable Kernel Samepage Merging: KSM periodically scans those areas
213	  of an application's address space that an app has advised may be
214	  mergeable.  When it finds pages of identical content, it replaces
215	  the many instances by a single page with that content, so
216	  saving memory until one or another app needs to modify the content.
217	  Recommended for use with KVM, or with other duplicative applications.
218	  See Documentation/vm/ksm.txt for more information: KSM is inactive
219	  until a program has madvised that an area is MADV_MERGEABLE, and
220	  root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
221
222config DEFAULT_MMAP_MIN_ADDR
223        int "Low address space to protect from user allocation"
224	depends on MMU
225        default 4096
226        help
227	  This is the portion of low virtual memory which should be protected
228	  from userspace allocation.  Keeping a user from writing to low pages
229	  can help reduce the impact of kernel NULL pointer bugs.
230
231	  For most ia64, ppc64 and x86 users with lots of address space
232	  a value of 65536 is reasonable and should cause no problems.
233	  On arm and other archs it should not be higher than 32768.
234	  Programs which use vm86 functionality or have some need to map
235	  this low address space will need CAP_SYS_RAWIO or disable this
236	  protection by setting the value to 0.
237
238	  This value can be changed after boot using the
239	  /proc/sys/vm/mmap_min_addr tunable.
240
241config ARCH_SUPPORTS_MEMORY_FAILURE
242	bool
243
244config MEMORY_FAILURE
245	depends on MMU
246	depends on ARCH_SUPPORTS_MEMORY_FAILURE
247	bool "Enable recovery from hardware memory errors"
248	help
249	  Enables code to recover from some memory failures on systems
250	  with MCA recovery. This allows a system to continue running
251	  even when some of its memory has uncorrected errors. This requires
252	  special hardware support and typically ECC memory.
253
254config HWPOISON_INJECT
255	tristate "HWPoison pages injector"
256	depends on MEMORY_FAILURE && DEBUG_KERNEL
257	select PROC_PAGE_MONITOR
258
259config NOMMU_INITIAL_TRIM_EXCESS
260	int "Turn on mmap() excess space trimming before booting"
261	depends on !MMU
262	default 1
263	help
264	  The NOMMU mmap() frequently needs to allocate large contiguous chunks
265	  of memory on which to store mappings, but it can only ask the system
266	  allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
267	  more than it requires.  To deal with this, mmap() is able to trim off
268	  the excess and return it to the allocator.
269
270	  If trimming is enabled, the excess is trimmed off and returned to the
271	  system allocator, which can cause extra fragmentation, particularly
272	  if there are a lot of transient processes.
273
274	  If trimming is disabled, the excess is kept, but not used, which for
275	  long-term mappings means that the space is wasted.
276
277	  Trimming can be dynamically controlled through a sysctl option
278	  (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
279	  excess pages there must be before trimming should occur, or zero if
280	  no trimming is to occur.
281
282	  This option specifies the initial value of this option.  The default
283	  of 1 says that all excess pages should be trimmed.
284
285	  See Documentation/nommu-mmap.txt for more information.
286