xref: /openbmc/linux/mm/Kconfig (revision d5532ee7) 
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
131config HAVE_MEMBLOCK
132	boolean
133
134# eventually, we can have this option just 'select SPARSEMEM'
135config MEMORY_HOTPLUG
136	bool "Allow for memory hot-add"
137	depends on SPARSEMEM || X86_64_ACPI_NUMA
138	depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG
139	depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
140
141config MEMORY_HOTPLUG_SPARSE
142	def_bool y
143	depends on SPARSEMEM && MEMORY_HOTPLUG
144
145config MEMORY_HOTREMOVE
146	bool "Allow for memory hot remove"
147	depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
148	depends on MIGRATION
149
150#
151# If we have space for more page flags then we can enable additional
152# optimizations and functionality.
153#
154# Regular Sparsemem takes page flag bits for the sectionid if it does not
155# use a virtual memmap. Disable extended page flags for 32 bit platforms
156# that require the use of a sectionid in the page flags.
157#
158config PAGEFLAGS_EXTENDED
159	def_bool y
160	depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
161
162# Heavily threaded applications may benefit from splitting the mm-wide
163# page_table_lock, so that faults on different parts of the user address
164# space can be handled with less contention: split it at this NR_CPUS.
165# Default to 4 for wider testing, though 8 might be more appropriate.
166# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
167# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
168# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
169#
170config SPLIT_PTLOCK_CPUS
171	int
172	default "999999" if ARM && !CPU_CACHE_VIPT
173	default "999999" if PARISC && !PA20
174	default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
175	default "4"
176
177#
178# support for memory compaction
179config COMPACTION
180	bool "Allow for memory compaction"
181	select MIGRATION
182	depends on EXPERIMENTAL && HUGETLB_PAGE && MMU
183	help
184	  Allows the compaction of memory for the allocation of huge pages.
185
186#
187# support for page migration
188#
189config MIGRATION
190	bool "Page migration"
191	def_bool y
192	depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION
193	help
194	  Allows the migration of the physical location of pages of processes
195	  while the virtual addresses are not changed. This is useful in
196	  two situations. The first is on NUMA systems to put pages nearer
197	  to the processors accessing. The second is when allocating huge
198	  pages as migration can relocate pages to satisfy a huge page
199	  allocation instead of reclaiming.
200
201config PHYS_ADDR_T_64BIT
202	def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
203
204config ZONE_DMA_FLAG
205	int
206	default "0" if !ZONE_DMA
207	default "1"
208
209config BOUNCE
210	def_bool y
211	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
212
213config NR_QUICK
214	int
215	depends on QUICKLIST
216	default "2" if AVR32
217	default "1"
218
219config VIRT_TO_BUS
220	def_bool y
221	depends on !ARCH_NO_VIRT_TO_BUS
222
223config MMU_NOTIFIER
224	bool
225
226config KSM
227	bool "Enable KSM for page merging"
228	depends on MMU
229	help
230	  Enable Kernel Samepage Merging: KSM periodically scans those areas
231	  of an application's address space that an app has advised may be
232	  mergeable.  When it finds pages of identical content, it replaces
233	  the many instances by a single page with that content, so
234	  saving memory until one or another app needs to modify the content.
235	  Recommended for use with KVM, or with other duplicative applications.
236	  See Documentation/vm/ksm.txt for more information: KSM is inactive
237	  until a program has madvised that an area is MADV_MERGEABLE, and
238	  root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
239
240config DEFAULT_MMAP_MIN_ADDR
241        int "Low address space to protect from user allocation"
242	depends on MMU
243        default 4096
244        help
245	  This is the portion of low virtual memory which should be protected
246	  from userspace allocation.  Keeping a user from writing to low pages
247	  can help reduce the impact of kernel NULL pointer bugs.
248
249	  For most ia64, ppc64 and x86 users with lots of address space
250	  a value of 65536 is reasonable and should cause no problems.
251	  On arm and other archs it should not be higher than 32768.
252	  Programs which use vm86 functionality or have some need to map
253	  this low address space will need CAP_SYS_RAWIO or disable this
254	  protection by setting the value to 0.
255
256	  This value can be changed after boot using the
257	  /proc/sys/vm/mmap_min_addr tunable.
258
259config ARCH_SUPPORTS_MEMORY_FAILURE
260	bool
261
262config MEMORY_FAILURE
263	depends on MMU
264	depends on ARCH_SUPPORTS_MEMORY_FAILURE
265	bool "Enable recovery from hardware memory errors"
266	help
267	  Enables code to recover from some memory failures on systems
268	  with MCA recovery. This allows a system to continue running
269	  even when some of its memory has uncorrected errors. This requires
270	  special hardware support and typically ECC memory.
271
272config HWPOISON_INJECT
273	tristate "HWPoison pages injector"
274	depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
275	select PROC_PAGE_MONITOR
276
277config NOMMU_INITIAL_TRIM_EXCESS
278	int "Turn on mmap() excess space trimming before booting"
279	depends on !MMU
280	default 1
281	help
282	  The NOMMU mmap() frequently needs to allocate large contiguous chunks
283	  of memory on which to store mappings, but it can only ask the system
284	  allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
285	  more than it requires.  To deal with this, mmap() is able to trim off
286	  the excess and return it to the allocator.
287
288	  If trimming is enabled, the excess is trimmed off and returned to the
289	  system allocator, which can cause extra fragmentation, particularly
290	  if there are a lot of transient processes.
291
292	  If trimming is disabled, the excess is kept, but not used, which for
293	  long-term mappings means that the space is wasted.
294
295	  Trimming can be dynamically controlled through a sysctl option
296	  (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
297	  excess pages there must be before trimming should occur, or zero if
298	  no trimming is to occur.
299
300	  This option specifies the initial value of this option.  The default
301	  of 1 says that all excess pages should be trimmed.
302
303	  See Documentation/nommu-mmap.txt for more information.
304