]> git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - mm/Kconfig
Linux 2.6.31-rc1
[mirror_ubuntu-jammy-kernel.git] / mm / Kconfig
1 config SELECT_MEMORY_MODEL
2 def_bool y
3 depends on EXPERIMENTAL || ARCH_SELECT_MEMORY_MODEL
4
5 choice
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
12 config 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
31 config 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
47 config 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
62 endchoice
63
64 config DISCONTIGMEM
65 def_bool y
66 depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
67
68 config SPARSEMEM
69 def_bool y
70 depends on SPARSEMEM_MANUAL
71
72 config FLATMEM
73 def_bool y
74 depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
75
76 config 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 #
85 config NEED_MULTIPLE_NODES
86 def_bool y
87 depends on DISCONTIGMEM || NUMA
88
89 config 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 #
103 config 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 #
111 config SPARSEMEM_EXTREME
112 def_bool y
113 depends on SPARSEMEM && !SPARSEMEM_STATIC
114
115 config SPARSEMEM_VMEMMAP_ENABLE
116 bool
117
118 config 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'
128 config 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
134 comment "Memory hotplug is currently incompatible with Software Suspend"
135 depends on SPARSEMEM && HOTPLUG && HIBERNATION && !S390
136
137 config MEMORY_HOTPLUG_SPARSE
138 def_bool y
139 depends on SPARSEMEM && MEMORY_HOTPLUG
140
141 config 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 #
154 config PAGEFLAGS_EXTENDED
155 def_bool y
156 depends on 64BIT || SPARSEMEM_VMEMMAP || !NUMA || !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 #
165 config 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 #
174 config 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
184 config PHYS_ADDR_T_64BIT
185 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
186
187 config ZONE_DMA_FLAG
188 int
189 default "0" if !ZONE_DMA
190 default "1"
191
192 config BOUNCE
193 def_bool y
194 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
195
196 config NR_QUICK
197 int
198 depends on QUICKLIST
199 default "2" if SUPERH || AVR32
200 default "1"
201
202 config VIRT_TO_BUS
203 def_bool y
204 depends on !ARCH_NO_VIRT_TO_BUS
205
206 config HAVE_MLOCK
207 bool
208 default y if MMU=y
209
210 config HAVE_MLOCKED_PAGE_BIT
211 bool
212 default y if HAVE_MLOCK=y
213
214 config MMU_NOTIFIER
215 bool
216
217 config DEFAULT_MMAP_MIN_ADDR
218 int "Low address space to protect from user allocation"
219 default 4096
220 help
221 This is the portion of low virtual memory which should be protected
222 from userspace allocation. Keeping a user from writing to low pages
223 can help reduce the impact of kernel NULL pointer bugs.
224
225 For most ia64, ppc64 and x86 users with lots of address space
226 a value of 65536 is reasonable and should cause no problems.
227 On arm and other archs it should not be higher than 32768.
228 Programs which use vm86 functionality would either need additional
229 permissions from either the LSM or the capabilities module or have
230 this protection disabled.
231
232 This value can be changed after boot using the
233 /proc/sys/vm/mmap_min_addr tunable.
234
235
236 config NOMMU_INITIAL_TRIM_EXCESS
237 int "Turn on mmap() excess space trimming before booting"
238 depends on !MMU
239 default 1
240 help
241 The NOMMU mmap() frequently needs to allocate large contiguous chunks
242 of memory on which to store mappings, but it can only ask the system
243 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
244 more than it requires. To deal with this, mmap() is able to trim off
245 the excess and return it to the allocator.
246
247 If trimming is enabled, the excess is trimmed off and returned to the
248 system allocator, which can cause extra fragmentation, particularly
249 if there are a lot of transient processes.
250
251 If trimming is disabled, the excess is kept, but not used, which for
252 long-term mappings means that the space is wasted.
253
254 Trimming can be dynamically controlled through a sysctl option
255 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
256 excess pages there must be before trimming should occur, or zero if
257 no trimming is to occur.
258
259 This option specifies the initial value of this option. The default
260 of 1 says that all excess pages should be trimmed.
261
262 See Documentation/nommu-mmap.txt for more information.