1 config SELECT_MEMORY_MODEL
3 depends on EXPERIMENTAL || ARCH_SELECT_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
14 depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
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
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".
29 If unsure, choose this option (Flat Memory) over any other.
31 config DISCONTIGMEM_MANUAL
32 bool "Discontiguous Memory"
33 depends on ARCH_DISCONTIGMEM_ENABLE
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
43 Many NUMA configurations will have this as the only option.
45 If unsure, choose "Flat Memory" over this option.
47 config SPARSEMEM_MANUAL
49 depends on ARCH_SPARSEMEM_ENABLE
51 This will be the only option for some systems, including
52 memory hotplug systems. This is normal.
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.
59 If unsure, choose "Discontiguous Memory" or "Flat Memory"
66 depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
70 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
74 depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
76 config FLAT_NODE_MEM_MAP
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.
85 config NEED_MULTIPLE_NODES
87 depends on DISCONTIGMEM || NUMA
89 config HAVE_MEMORY_PRESENT
91 depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
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.
100 # This option will also potentially produce smaller runtime code
101 # with gcc 3.4 and later.
103 config SPARSEMEM_STATIC
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.
111 config SPARSEMEM_EXTREME
113 depends on SPARSEMEM && !SPARSEMEM_STATIC
115 config SPARSEMEM_VMEMMAP_ENABLE
118 config SPARSEMEM_VMEMMAP
119 bool "Sparse Memory virtual memmap"
120 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
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.
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)
134 comment "Memory hotplug is currently incompatible with Software Suspend"
135 depends on SPARSEMEM && HOTPLUG && HIBERNATION && !S390
137 config MEMORY_HOTPLUG_SPARSE
139 depends on SPARSEMEM && MEMORY_HOTPLUG
141 config MEMORY_HOTREMOVE
142 bool "Allow for memory hot remove"
143 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
147 # If we have space for more page flags then we can enable additional
148 # optimizations and functionality.
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.
154 config PAGEFLAGS_EXTENDED
156 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
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.
165 config SPLIT_PTLOCK_CPUS
167 default "4096" if ARM && !CPU_CACHE_VIPT
168 default "4096" if PARISC && !PA20
172 # support for page migration
175 bool "Page migration"
177 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
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
184 config PHYS_ADDR_T_64BIT
185 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
189 default "0" if !ZONE_DMA
194 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
199 default "2" if SUPERH || AVR32
204 depends on !ARCH_NO_VIRT_TO_BUS
210 config HAVE_MLOCKED_PAGE_BIT
212 default y if HAVE_MLOCK=y
218 bool "Enable KSM for page merging"
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).
231 config DEFAULT_MMAP_MIN_ADDR
232 int "Low address space to protect from user allocation"
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.
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.
246 This value can be changed after boot using the
247 /proc/sys/vm/mmap_min_addr tunable.
249 config ARCH_SUPPORTS_MEMORY_FAILURE
252 config MEMORY_FAILURE
254 depends on ARCH_SUPPORTS_MEMORY_FAILURE
255 bool "Enable recovery from hardware memory errors"
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.
262 config HWPOISON_INJECT
263 tristate "Poison pages injector"
264 depends on MEMORY_FAILURE && DEBUG_KERNEL
266 config NOMMU_INITIAL_TRIM_EXCESS
267 int "Turn on mmap() excess space trimming before booting"
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.
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.
281 If trimming is disabled, the excess is kept, but not used, which for
282 long-term mappings means that the space is wasted.
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.
289 This option specifies the initial value of this option. The default
290 of 1 says that all excess pages should be trimmed.
292 See Documentation/nommu-mmap.txt for more information.