xref: /openbmc/linux/mm/Kconfig (revision 1fa6ac37) 
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 memory compaction
176config COMPACTION
177	bool "Allow for memory compaction"
178	select MIGRATION
179	depends on EXPERIMENTAL && HUGETLB_PAGE && MMU
180	help
181	  Allows the compaction of memory for the allocation of huge pages.
182
183#
184# support for page migration
185#
186config MIGRATION
187	bool "Page migration"
188	def_bool y
189	depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
190	help
191	  Allows the migration of the physical location of pages of processes
192	  while the virtual addresses are not changed. This is useful in
193	  two situations. The first is on NUMA systems to put pages nearer
194	  to the processors accessing. The second is when allocating huge
195	  pages as migration can relocate pages to satisfy a huge page
196	  allocation instead of reclaiming.
197
198config PHYS_ADDR_T_64BIT
199	def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
200
201config ZONE_DMA_FLAG
202	int
203	default "0" if !ZONE_DMA
204	default "1"
205
206config BOUNCE
207	def_bool y
208	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
209
210config NR_QUICK
211	int
212	depends on QUICKLIST
213	default "2" if AVR32
214	default "1"
215
216config VIRT_TO_BUS
217	def_bool y
218	depends on !ARCH_NO_VIRT_TO_BUS
219
220config MMU_NOTIFIER
221	bool
222
223config KSM
224	bool "Enable KSM for page merging"
225	depends on MMU
226	help
227	  Enable Kernel Samepage Merging: KSM periodically scans those areas
228	  of an application's address space that an app has advised may be
229	  mergeable.  When it finds pages of identical content, it replaces
230	  the many instances by a single page with that content, so
231	  saving memory until one or another app needs to modify the content.
232	  Recommended for use with KVM, or with other duplicative applications.
233	  See Documentation/vm/ksm.txt for more information: KSM is inactive
234	  until a program has madvised that an area is MADV_MERGEABLE, and
235	  root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
236
237config DEFAULT_MMAP_MIN_ADDR
238        int "Low address space to protect from user allocation"
239	depends on MMU
240        default 4096
241        help
242	  This is the portion of low virtual memory which should be protected
243	  from userspace allocation.  Keeping a user from writing to low pages
244	  can help reduce the impact of kernel NULL pointer bugs.
245
246	  For most ia64, ppc64 and x86 users with lots of address space
247	  a value of 65536 is reasonable and should cause no problems.
248	  On arm and other archs it should not be higher than 32768.
249	  Programs which use vm86 functionality or have some need to map
250	  this low address space will need CAP_SYS_RAWIO or disable this
251	  protection by setting the value to 0.
252
253	  This value can be changed after boot using the
254	  /proc/sys/vm/mmap_min_addr tunable.
255
256config ARCH_SUPPORTS_MEMORY_FAILURE
257	bool
258
259config MEMORY_FAILURE
260	depends on MMU
261	depends on ARCH_SUPPORTS_MEMORY_FAILURE
262	bool "Enable recovery from hardware memory errors"
263	help
264	  Enables code to recover from some memory failures on systems
265	  with MCA recovery. This allows a system to continue running
266	  even when some of its memory has uncorrected errors. This requires
267	  special hardware support and typically ECC memory.
268
269config HWPOISON_INJECT
270	tristate "HWPoison pages injector"
271	depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
272	select PROC_PAGE_MONITOR
273
274config NOMMU_INITIAL_TRIM_EXCESS
275	int "Turn on mmap() excess space trimming before booting"
276	depends on !MMU
277	default 1
278	help
279	  The NOMMU mmap() frequently needs to allocate large contiguous chunks
280	  of memory on which to store mappings, but it can only ask the system
281	  allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
282	  more than it requires.  To deal with this, mmap() is able to trim off
283	  the excess and return it to the allocator.
284
285	  If trimming is enabled, the excess is trimmed off and returned to the
286	  system allocator, which can cause extra fragmentation, particularly
287	  if there are a lot of transient processes.
288
289	  If trimming is disabled, the excess is kept, but not used, which for
290	  long-term mappings means that the space is wasted.
291
292	  Trimming can be dynamically controlled through a sysctl option
293	  (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
294	  excess pages there must be before trimming should occur, or zero if
295	  no trimming is to occur.
296
297	  This option specifies the initial value of this option.  The default
298	  of 1 says that all excess pages should be trimmed.
299
300	  See Documentation/nommu-mmap.txt for more information.
301