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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 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
305config TRANSPARENT_HUGEPAGE
306 bool "Transparent Hugepage Support"
307 depends on X86 && MMU
308 select COMPACTION
309 help
310 Transparent Hugepages allows the kernel to use huge pages and
311 huge tlb transparently to the applications whenever possible.
312 This feature can improve computing performance to certain
313 applications by speeding up page faults during memory
314 allocation, by reducing the number of tlb misses and by speeding
315 up the pagetable walking.
316
317 If memory constrained on embedded, you may want to say N.
318
319choice
320 prompt "Transparent Hugepage Support sysfs defaults"
321 depends on TRANSPARENT_HUGEPAGE
322 default TRANSPARENT_HUGEPAGE_ALWAYS
323 help
324 Selects the sysfs defaults for Transparent Hugepage Support.
325
326 config TRANSPARENT_HUGEPAGE_ALWAYS
327 bool "always"
328 help
329 Enabling Transparent Hugepage always, can increase the
330 memory footprint of applications without a guaranteed
331 benefit but it will work automatically for all applications.
332
333 config TRANSPARENT_HUGEPAGE_MADVISE
334 bool "madvise"
335 help
336 Enabling Transparent Hugepage madvise, will only provide a
337 performance improvement benefit to the applications using
338 madvise(MADV_HUGEPAGE) but it won't risk to increase the
339 memory footprint of applications without a guaranteed
340 benefit.
341endchoice
342
343#
344# UP and nommu archs use km based percpu allocator
345#
346config NEED_PER_CPU_KM
347 depends on !SMP
348 bool
349 default y
350
351config CLEANCACHE
352 bool "Enable cleancache driver to cache clean pages if tmem is present"
353 default n
354 help
355 Cleancache can be thought of as a page-granularity victim cache
356 for clean pages that the kernel's pageframe replacement algorithm
357 (PFRA) would like to keep around, but can't since there isn't enough
358 memory. So when the PFRA "evicts" a page, it first attempts to use
359 cleancache code to put the data contained in that page into
360 "transcendent memory", memory that is not directly accessible or
361 addressable by the kernel and is of unknown and possibly
362 time-varying size. And when a cleancache-enabled
363 filesystem wishes to access a page in a file on disk, it first
364 checks cleancache to see if it already contains it; if it does,
365 the page is copied into the kernel and a disk access is avoided.
366 When a transcendent memory driver is available (such as zcache or
367 Xen transcendent memory), a significant I/O reduction
368 may be achieved. When none is available, all cleancache calls
369 are reduced to a single pointer-compare-against-NULL resulting
370 in a negligible performance hit.
371
372 If unsure, say Y to enable cleancache
1config SELECT_MEMORY_MODEL
2 def_bool y
3 depends on 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 a 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 bool
133
134config HAVE_MEMBLOCK_NODE_MAP
135 bool
136
137config HAVE_MEMBLOCK_PHYS_MAP
138 bool
139
140config HAVE_GENERIC_GUP
141 bool
142
143config ARCH_DISCARD_MEMBLOCK
144 bool
145
146config NO_BOOTMEM
147 bool
148
149config MEMORY_ISOLATION
150 bool
151
152#
153# Only be set on architectures that have completely implemented memory hotplug
154# feature. If you are not sure, don't touch it.
155#
156config HAVE_BOOTMEM_INFO_NODE
157 def_bool n
158
159# eventually, we can have this option just 'select SPARSEMEM'
160config MEMORY_HOTPLUG
161 bool "Allow for memory hot-add"
162 depends on SPARSEMEM || X86_64_ACPI_NUMA
163 depends on ARCH_ENABLE_MEMORY_HOTPLUG
164
165config MEMORY_HOTPLUG_SPARSE
166 def_bool y
167 depends on SPARSEMEM && MEMORY_HOTPLUG
168
169config MEMORY_HOTPLUG_DEFAULT_ONLINE
170 bool "Online the newly added memory blocks by default"
171 default n
172 depends on MEMORY_HOTPLUG
173 help
174 This option sets the default policy setting for memory hotplug
175 onlining policy (/sys/devices/system/memory/auto_online_blocks) which
176 determines what happens to newly added memory regions. Policy setting
177 can always be changed at runtime.
178 See Documentation/memory-hotplug.txt for more information.
179
180 Say Y here if you want all hot-plugged memory blocks to appear in
181 'online' state by default.
182 Say N here if you want the default policy to keep all hot-plugged
183 memory blocks in 'offline' state.
184
185config MEMORY_HOTREMOVE
186 bool "Allow for memory hot remove"
187 select MEMORY_ISOLATION
188 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
189 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
190 depends on MIGRATION
191
192# Heavily threaded applications may benefit from splitting the mm-wide
193# page_table_lock, so that faults on different parts of the user address
194# space can be handled with less contention: split it at this NR_CPUS.
195# Default to 4 for wider testing, though 8 might be more appropriate.
196# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
197# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
198# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
199#
200config SPLIT_PTLOCK_CPUS
201 int
202 default "999999" if !MMU
203 default "999999" if ARM && !CPU_CACHE_VIPT
204 default "999999" if PARISC && !PA20
205 default "4"
206
207config ARCH_ENABLE_SPLIT_PMD_PTLOCK
208 bool
209
210#
211# support for memory balloon
212config MEMORY_BALLOON
213 bool
214
215#
216# support for memory balloon compaction
217config BALLOON_COMPACTION
218 bool "Allow for balloon memory compaction/migration"
219 def_bool y
220 depends on COMPACTION && MEMORY_BALLOON
221 help
222 Memory fragmentation introduced by ballooning might reduce
223 significantly the number of 2MB contiguous memory blocks that can be
224 used within a guest, thus imposing performance penalties associated
225 with the reduced number of transparent huge pages that could be used
226 by the guest workload. Allowing the compaction & migration for memory
227 pages enlisted as being part of memory balloon devices avoids the
228 scenario aforementioned and helps improving memory defragmentation.
229
230#
231# support for memory compaction
232config COMPACTION
233 bool "Allow for memory compaction"
234 def_bool y
235 select MIGRATION
236 depends on MMU
237 help
238 Compaction is the only memory management component to form
239 high order (larger physically contiguous) memory blocks
240 reliably. The page allocator relies on compaction heavily and
241 the lack of the feature can lead to unexpected OOM killer
242 invocations for high order memory requests. You shouldn't
243 disable this option unless there really is a strong reason for
244 it and then we would be really interested to hear about that at
245 linux-mm@kvack.org.
246
247#
248# support for page migration
249#
250config MIGRATION
251 bool "Page migration"
252 def_bool y
253 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
254 help
255 Allows the migration of the physical location of pages of processes
256 while the virtual addresses are not changed. This is useful in
257 two situations. The first is on NUMA systems to put pages nearer
258 to the processors accessing. The second is when allocating huge
259 pages as migration can relocate pages to satisfy a huge page
260 allocation instead of reclaiming.
261
262config ARCH_ENABLE_HUGEPAGE_MIGRATION
263 bool
264
265config ARCH_ENABLE_THP_MIGRATION
266 bool
267
268config PHYS_ADDR_T_64BIT
269 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
270
271config BOUNCE
272 bool "Enable bounce buffers"
273 default y
274 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
275 help
276 Enable bounce buffers for devices that cannot access
277 the full range of memory available to the CPU. Enabled
278 by default when ZONE_DMA or HIGHMEM is selected, but you
279 may say n to override this.
280
281config NR_QUICK
282 int
283 depends on QUICKLIST
284 default "1"
285
286config VIRT_TO_BUS
287 bool
288 help
289 An architecture should select this if it implements the
290 deprecated interface virt_to_bus(). All new architectures
291 should probably not select this.
292
293
294config MMU_NOTIFIER
295 bool
296 select SRCU
297
298config KSM
299 bool "Enable KSM for page merging"
300 depends on MMU
301 help
302 Enable Kernel Samepage Merging: KSM periodically scans those areas
303 of an application's address space that an app has advised may be
304 mergeable. When it finds pages of identical content, it replaces
305 the many instances by a single page with that content, so
306 saving memory until one or another app needs to modify the content.
307 Recommended for use with KVM, or with other duplicative applications.
308 See Documentation/vm/ksm.txt for more information: KSM is inactive
309 until a program has madvised that an area is MADV_MERGEABLE, and
310 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
311
312config DEFAULT_MMAP_MIN_ADDR
313 int "Low address space to protect from user allocation"
314 depends on MMU
315 default 4096
316 help
317 This is the portion of low virtual memory which should be protected
318 from userspace allocation. Keeping a user from writing to low pages
319 can help reduce the impact of kernel NULL pointer bugs.
320
321 For most ia64, ppc64 and x86 users with lots of address space
322 a value of 65536 is reasonable and should cause no problems.
323 On arm and other archs it should not be higher than 32768.
324 Programs which use vm86 functionality or have some need to map
325 this low address space will need CAP_SYS_RAWIO or disable this
326 protection by setting the value to 0.
327
328 This value can be changed after boot using the
329 /proc/sys/vm/mmap_min_addr tunable.
330
331config ARCH_SUPPORTS_MEMORY_FAILURE
332 bool
333
334config MEMORY_FAILURE
335 depends on MMU
336 depends on ARCH_SUPPORTS_MEMORY_FAILURE
337 bool "Enable recovery from hardware memory errors"
338 select MEMORY_ISOLATION
339 select RAS
340 help
341 Enables code to recover from some memory failures on systems
342 with MCA recovery. This allows a system to continue running
343 even when some of its memory has uncorrected errors. This requires
344 special hardware support and typically ECC memory.
345
346config HWPOISON_INJECT
347 tristate "HWPoison pages injector"
348 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
349 select PROC_PAGE_MONITOR
350
351config NOMMU_INITIAL_TRIM_EXCESS
352 int "Turn on mmap() excess space trimming before booting"
353 depends on !MMU
354 default 1
355 help
356 The NOMMU mmap() frequently needs to allocate large contiguous chunks
357 of memory on which to store mappings, but it can only ask the system
358 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
359 more than it requires. To deal with this, mmap() is able to trim off
360 the excess and return it to the allocator.
361
362 If trimming is enabled, the excess is trimmed off and returned to the
363 system allocator, which can cause extra fragmentation, particularly
364 if there are a lot of transient processes.
365
366 If trimming is disabled, the excess is kept, but not used, which for
367 long-term mappings means that the space is wasted.
368
369 Trimming can be dynamically controlled through a sysctl option
370 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
371 excess pages there must be before trimming should occur, or zero if
372 no trimming is to occur.
373
374 This option specifies the initial value of this option. The default
375 of 1 says that all excess pages should be trimmed.
376
377 See Documentation/nommu-mmap.txt for more information.
378
379config TRANSPARENT_HUGEPAGE
380 bool "Transparent Hugepage Support"
381 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
382 select COMPACTION
383 select RADIX_TREE_MULTIORDER
384 help
385 Transparent Hugepages allows the kernel to use huge pages and
386 huge tlb transparently to the applications whenever possible.
387 This feature can improve computing performance to certain
388 applications by speeding up page faults during memory
389 allocation, by reducing the number of tlb misses and by speeding
390 up the pagetable walking.
391
392 If memory constrained on embedded, you may want to say N.
393
394choice
395 prompt "Transparent Hugepage Support sysfs defaults"
396 depends on TRANSPARENT_HUGEPAGE
397 default TRANSPARENT_HUGEPAGE_ALWAYS
398 help
399 Selects the sysfs defaults for Transparent Hugepage Support.
400
401 config TRANSPARENT_HUGEPAGE_ALWAYS
402 bool "always"
403 help
404 Enabling Transparent Hugepage always, can increase the
405 memory footprint of applications without a guaranteed
406 benefit but it will work automatically for all applications.
407
408 config TRANSPARENT_HUGEPAGE_MADVISE
409 bool "madvise"
410 help
411 Enabling Transparent Hugepage madvise, will only provide a
412 performance improvement benefit to the applications using
413 madvise(MADV_HUGEPAGE) but it won't risk to increase the
414 memory footprint of applications without a guaranteed
415 benefit.
416endchoice
417
418config ARCH_WANTS_THP_SWAP
419 def_bool n
420
421config THP_SWAP
422 def_bool y
423 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP
424 help
425 Swap transparent huge pages in one piece, without splitting.
426 XXX: For now this only does clustered swap space allocation.
427
428 For selection by architectures with reasonable THP sizes.
429
430config TRANSPARENT_HUGE_PAGECACHE
431 def_bool y
432 depends on TRANSPARENT_HUGEPAGE
433
434#
435# UP and nommu archs use km based percpu allocator
436#
437config NEED_PER_CPU_KM
438 depends on !SMP
439 bool
440 default y
441
442config CLEANCACHE
443 bool "Enable cleancache driver to cache clean pages if tmem is present"
444 default n
445 help
446 Cleancache can be thought of as a page-granularity victim cache
447 for clean pages that the kernel's pageframe replacement algorithm
448 (PFRA) would like to keep around, but can't since there isn't enough
449 memory. So when the PFRA "evicts" a page, it first attempts to use
450 cleancache code to put the data contained in that page into
451 "transcendent memory", memory that is not directly accessible or
452 addressable by the kernel and is of unknown and possibly
453 time-varying size. And when a cleancache-enabled
454 filesystem wishes to access a page in a file on disk, it first
455 checks cleancache to see if it already contains it; if it does,
456 the page is copied into the kernel and a disk access is avoided.
457 When a transcendent memory driver is available (such as zcache or
458 Xen transcendent memory), a significant I/O reduction
459 may be achieved. When none is available, all cleancache calls
460 are reduced to a single pointer-compare-against-NULL resulting
461 in a negligible performance hit.
462
463 If unsure, say Y to enable cleancache
464
465config FRONTSWAP
466 bool "Enable frontswap to cache swap pages if tmem is present"
467 depends on SWAP
468 default n
469 help
470 Frontswap is so named because it can be thought of as the opposite
471 of a "backing" store for a swap device. The data is stored into
472 "transcendent memory", memory that is not directly accessible or
473 addressable by the kernel and is of unknown and possibly
474 time-varying size. When space in transcendent memory is available,
475 a significant swap I/O reduction may be achieved. When none is
476 available, all frontswap calls are reduced to a single pointer-
477 compare-against-NULL resulting in a negligible performance hit
478 and swap data is stored as normal on the matching swap device.
479
480 If unsure, say Y to enable frontswap.
481
482config CMA
483 bool "Contiguous Memory Allocator"
484 depends on HAVE_MEMBLOCK && MMU
485 select MIGRATION
486 select MEMORY_ISOLATION
487 help
488 This enables the Contiguous Memory Allocator which allows other
489 subsystems to allocate big physically-contiguous blocks of memory.
490 CMA reserves a region of memory and allows only movable pages to
491 be allocated from it. This way, the kernel can use the memory for
492 pagecache and when a subsystem requests for contiguous area, the
493 allocated pages are migrated away to serve the contiguous request.
494
495 If unsure, say "n".
496
497config CMA_DEBUG
498 bool "CMA debug messages (DEVELOPMENT)"
499 depends on DEBUG_KERNEL && CMA
500 help
501 Turns on debug messages in CMA. This produces KERN_DEBUG
502 messages for every CMA call as well as various messages while
503 processing calls such as dma_alloc_from_contiguous().
504 This option does not affect warning and error messages.
505
506config CMA_DEBUGFS
507 bool "CMA debugfs interface"
508 depends on CMA && DEBUG_FS
509 help
510 Turns on the DebugFS interface for CMA.
511
512config CMA_AREAS
513 int "Maximum count of the CMA areas"
514 depends on CMA
515 default 7
516 help
517 CMA allows to create CMA areas for particular purpose, mainly,
518 used as device private area. This parameter sets the maximum
519 number of CMA area in the system.
520
521 If unsure, leave the default value "7".
522
523config MEM_SOFT_DIRTY
524 bool "Track memory changes"
525 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
526 select PROC_PAGE_MONITOR
527 help
528 This option enables memory changes tracking by introducing a
529 soft-dirty bit on pte-s. This bit it set when someone writes
530 into a page just as regular dirty bit, but unlike the latter
531 it can be cleared by hands.
532
533 See Documentation/vm/soft-dirty.txt for more details.
534
535config ZSWAP
536 bool "Compressed cache for swap pages (EXPERIMENTAL)"
537 depends on FRONTSWAP && CRYPTO=y
538 select CRYPTO_LZO
539 select ZPOOL
540 default n
541 help
542 A lightweight compressed cache for swap pages. It takes
543 pages that are in the process of being swapped out and attempts to
544 compress them into a dynamically allocated RAM-based memory pool.
545 This can result in a significant I/O reduction on swap device and,
546 in the case where decompressing from RAM is faster that swap device
547 reads, can also improve workload performance.
548
549 This is marked experimental because it is a new feature (as of
550 v3.11) that interacts heavily with memory reclaim. While these
551 interactions don't cause any known issues on simple memory setups,
552 they have not be fully explored on the large set of potential
553 configurations and workloads that exist.
554
555config ZPOOL
556 tristate "Common API for compressed memory storage"
557 default n
558 help
559 Compressed memory storage API. This allows using either zbud or
560 zsmalloc.
561
562config ZBUD
563 tristate "Low (Up to 2x) density storage for compressed pages"
564 default n
565 help
566 A special purpose allocator for storing compressed pages.
567 It is designed to store up to two compressed pages per physical
568 page. While this design limits storage density, it has simple and
569 deterministic reclaim properties that make it preferable to a higher
570 density approach when reclaim will be used.
571
572config Z3FOLD
573 tristate "Up to 3x density storage for compressed pages"
574 depends on ZPOOL
575 default n
576 help
577 A special purpose allocator for storing compressed pages.
578 It is designed to store up to three compressed pages per physical
579 page. It is a ZBUD derivative so the simplicity and determinism are
580 still there.
581
582config ZSMALLOC
583 tristate "Memory allocator for compressed pages"
584 depends on MMU
585 default n
586 help
587 zsmalloc is a slab-based memory allocator designed to store
588 compressed RAM pages. zsmalloc uses virtual memory mapping
589 in order to reduce fragmentation. However, this results in a
590 non-standard allocator interface where a handle, not a pointer, is
591 returned by an alloc(). This handle must be mapped in order to
592 access the allocated space.
593
594config PGTABLE_MAPPING
595 bool "Use page table mapping to access object in zsmalloc"
596 depends on ZSMALLOC
597 help
598 By default, zsmalloc uses a copy-based object mapping method to
599 access allocations that span two pages. However, if a particular
600 architecture (ex, ARM) performs VM mapping faster than copying,
601 then you should select this. This causes zsmalloc to use page table
602 mapping rather than copying for object mapping.
603
604 You can check speed with zsmalloc benchmark:
605 https://github.com/spartacus06/zsmapbench
606
607config ZSMALLOC_STAT
608 bool "Export zsmalloc statistics"
609 depends on ZSMALLOC
610 select DEBUG_FS
611 help
612 This option enables code in the zsmalloc to collect various
613 statistics about whats happening in zsmalloc and exports that
614 information to userspace via debugfs.
615 If unsure, say N.
616
617config GENERIC_EARLY_IOREMAP
618 bool
619
620config MAX_STACK_SIZE_MB
621 int "Maximum user stack size for 32-bit processes (MB)"
622 default 80
623 range 8 2048
624 depends on STACK_GROWSUP && (!64BIT || COMPAT)
625 help
626 This is the maximum stack size in Megabytes in the VM layout of 32-bit
627 user processes when the stack grows upwards (currently only on parisc
628 arch). The stack will be located at the highest memory address minus
629 the given value, unless the RLIMIT_STACK hard limit is changed to a
630 smaller value in which case that is used.
631
632 A sane initial value is 80 MB.
633
634config DEFERRED_STRUCT_PAGE_INIT
635 bool "Defer initialisation of struct pages to kthreads"
636 default n
637 depends on NO_BOOTMEM
638 depends on !FLATMEM
639 depends on !NEED_PER_CPU_KM
640 help
641 Ordinarily all struct pages are initialised during early boot in a
642 single thread. On very large machines this can take a considerable
643 amount of time. If this option is set, large machines will bring up
644 a subset of memmap at boot and then initialise the rest in parallel
645 by starting one-off "pgdatinitX" kernel thread for each node X. This
646 has a potential performance impact on processes running early in the
647 lifetime of the system until these kthreads finish the
648 initialisation.
649
650config IDLE_PAGE_TRACKING
651 bool "Enable idle page tracking"
652 depends on SYSFS && MMU
653 select PAGE_EXTENSION if !64BIT
654 help
655 This feature allows to estimate the amount of user pages that have
656 not been touched during a given period of time. This information can
657 be useful to tune memory cgroup limits and/or for job placement
658 within a compute cluster.
659
660 See Documentation/vm/idle_page_tracking.txt for more details.
661
662# arch_add_memory() comprehends device memory
663config ARCH_HAS_ZONE_DEVICE
664 bool
665
666config ZONE_DEVICE
667 bool "Device memory (pmem, HMM, etc...) hotplug support"
668 depends on MEMORY_HOTPLUG
669 depends on MEMORY_HOTREMOVE
670 depends on SPARSEMEM_VMEMMAP
671 depends on ARCH_HAS_ZONE_DEVICE
672 select RADIX_TREE_MULTIORDER
673
674 help
675 Device memory hotplug support allows for establishing pmem,
676 or other device driver discovered memory regions, in the
677 memmap. This allows pfn_to_page() lookups of otherwise
678 "device-physical" addresses which is needed for using a DAX
679 mapping in an O_DIRECT operation, among other things.
680
681 If FS_DAX is enabled, then say Y.
682
683config ARCH_HAS_HMM
684 bool
685 default y
686 depends on (X86_64 || PPC64)
687 depends on ZONE_DEVICE
688 depends on MMU && 64BIT
689 depends on MEMORY_HOTPLUG
690 depends on MEMORY_HOTREMOVE
691 depends on SPARSEMEM_VMEMMAP
692
693config MIGRATE_VMA_HELPER
694 bool
695
696config HMM
697 bool
698 select MIGRATE_VMA_HELPER
699
700config HMM_MIRROR
701 bool "HMM mirror CPU page table into a device page table"
702 depends on ARCH_HAS_HMM
703 select MMU_NOTIFIER
704 select HMM
705 help
706 Select HMM_MIRROR if you want to mirror range of the CPU page table of a
707 process into a device page table. Here, mirror means "keep synchronized".
708 Prerequisites: the device must provide the ability to write-protect its
709 page tables (at PAGE_SIZE granularity), and must be able to recover from
710 the resulting potential page faults.
711
712config DEVICE_PRIVATE
713 bool "Unaddressable device memory (GPU memory, ...)"
714 depends on ARCH_HAS_HMM
715 select HMM
716
717 help
718 Allows creation of struct pages to represent unaddressable device
719 memory; i.e., memory that is only accessible from the device (or
720 group of devices). You likely also want to select HMM_MIRROR.
721
722config DEVICE_PUBLIC
723 bool "Addressable device memory (like GPU memory)"
724 depends on ARCH_HAS_HMM
725 select HMM
726
727 help
728 Allows creation of struct pages to represent addressable device
729 memory; i.e., memory that is accessible from both the device and
730 the CPU
731
732config FRAME_VECTOR
733 bool
734
735config ARCH_USES_HIGH_VMA_FLAGS
736 bool
737config ARCH_HAS_PKEYS
738 bool
739
740config PERCPU_STATS
741 bool "Collect percpu memory statistics"
742 default n
743 help
744 This feature collects and exposes statistics via debugfs. The
745 information includes global and per chunk statistics, which can
746 be used to help understand percpu memory usage.
747
748config GUP_BENCHMARK
749 bool "Enable infrastructure for get_user_pages_fast() benchmarking"
750 default n
751 help
752 Provides /sys/kernel/debug/gup_benchmark that helps with testing
753 performance of get_user_pages_fast().
754
755 See tools/testing/selftests/vm/gup_benchmark.c