xref: /openbmc/linux/mm/Kconfig (revision 5a0e3ad6) 
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_ALLOC_MEM_MAP_TOGETHER
119	def_bool y
120	depends on SPARSEMEM && X86_64
121
122config SPARSEMEM_VMEMMAP
123	bool "Sparse Memory virtual memmap"
124	depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
125	default y
126	help
127	 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
128	 pfn_to_page and page_to_pfn operations.  This is the most
129	 efficient option when sufficient kernel resources are available.
130
131# eventually, we can have this option just 'select SPARSEMEM'
132config MEMORY_HOTPLUG
133	bool "Allow for memory hot-add"
134	depends on SPARSEMEM || X86_64_ACPI_NUMA
135	depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG
136	depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
137
138config MEMORY_HOTPLUG_SPARSE
139	def_bool y
140	depends on SPARSEMEM && MEMORY_HOTPLUG
141
142config MEMORY_HOTREMOVE
143	bool "Allow for memory hot remove"
144	depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
145	depends on MIGRATION
146
147#
148# If we have space for more page flags then we can enable additional
149# optimizations and functionality.
150#
151# Regular Sparsemem takes page flag bits for the sectionid if it does not
152# use a virtual memmap. Disable extended page flags for 32 bit platforms
153# that require the use of a sectionid in the page flags.
154#
155config PAGEFLAGS_EXTENDED
156	def_bool y
157	depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
158
159# Heavily threaded applications may benefit from splitting the mm-wide
160# page_table_lock, so that faults on different parts of the user address
161# space can be handled with less contention: split it at this NR_CPUS.
162# Default to 4 for wider testing, though 8 might be more appropriate.
163# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
164# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
165# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
166#
167config SPLIT_PTLOCK_CPUS
168	int
169	default "999999" if ARM && !CPU_CACHE_VIPT
170	default "999999" if PARISC && !PA20
171	default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
172	default "4"
173
174#
175# support for page migration
176#
177config MIGRATION
178	bool "Page migration"
179	def_bool y
180	depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
181	help
182	  Allows the migration of the physical location of pages of processes
183	  while the virtual addresses are not changed. This is useful for
184	  example on NUMA systems to put pages nearer to the processors accessing
185	  the page.
186
187config PHYS_ADDR_T_64BIT
188	def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
189
190config ZONE_DMA_FLAG
191	int
192	default "0" if !ZONE_DMA
193	default "1"
194
195config BOUNCE
196	def_bool y
197	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
198
199config NR_QUICK
200	int
201	depends on QUICKLIST
202	default "2" if AVR32
203	default "1"
204
205config VIRT_TO_BUS
206	def_bool y
207	depends on !ARCH_NO_VIRT_TO_BUS
208
209config MMU_NOTIFIER
210	bool
211
212config KSM
213	bool "Enable KSM for page merging"
214	depends on MMU
215	help
216	  Enable Kernel Samepage Merging: KSM periodically scans those areas
217	  of an application's address space that an app has advised may be
218	  mergeable.  When it finds pages of identical content, it replaces
219	  the many instances by a single page with that content, so
220	  saving memory until one or another app needs to modify the content.
221	  Recommended for use with KVM, or with other duplicative applications.
222	  See Documentation/vm/ksm.txt for more information: KSM is inactive
223	  until a program has madvised that an area is MADV_MERGEABLE, and
224	  root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
225
226config DEFAULT_MMAP_MIN_ADDR
227        int "Low address space to protect from user allocation"
228	depends on MMU
229        default 4096
230        help
231	  This is the portion of low virtual memory which should be protected
232	  from userspace allocation.  Keeping a user from writing to low pages
233	  can help reduce the impact of kernel NULL pointer bugs.
234
235	  For most ia64, ppc64 and x86 users with lots of address space
236	  a value of 65536 is reasonable and should cause no problems.
237	  On arm and other archs it should not be higher than 32768.
238	  Programs which use vm86 functionality or have some need to map
239	  this low address space will need CAP_SYS_RAWIO or disable this
240	  protection by setting the value to 0.
241
242	  This value can be changed after boot using the
243	  /proc/sys/vm/mmap_min_addr tunable.
244
245config ARCH_SUPPORTS_MEMORY_FAILURE
246	bool
247
248config MEMORY_FAILURE
249	depends on MMU
250	depends on ARCH_SUPPORTS_MEMORY_FAILURE
251	bool "Enable recovery from hardware memory errors"
252	help
253	  Enables code to recover from some memory failures on systems
254	  with MCA recovery. This allows a system to continue running
255	  even when some of its memory has uncorrected errors. This requires
256	  special hardware support and typically ECC memory.
257
258config HWPOISON_INJECT
259	tristate "HWPoison pages injector"
260	depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
261	select PROC_PAGE_MONITOR
262
263config NOMMU_INITIAL_TRIM_EXCESS
264	int "Turn on mmap() excess space trimming before booting"
265	depends on !MMU
266	default 1
267	help
268	  The NOMMU mmap() frequently needs to allocate large contiguous chunks
269	  of memory on which to store mappings, but it can only ask the system
270	  allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
271	  more than it requires.  To deal with this, mmap() is able to trim off
272	  the excess and return it to the allocator.
273
274	  If trimming is enabled, the excess is trimmed off and returned to the
275	  system allocator, which can cause extra fragmentation, particularly
276	  if there are a lot of transient processes.
277
278	  If trimming is disabled, the excess is kept, but not used, which for
279	  long-term mappings means that the space is wasted.
280
281	  Trimming can be dynamically controlled through a sysctl option
282	  (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
283	  excess pages there must be before trimming should occur, or zero if
284	  no trimming is to occur.
285
286	  This option specifies the initial value of this option.  The default
287	  of 1 says that all excess pages should be trimmed.
288
289	  See Documentation/nommu-mmap.txt for more information.
290