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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 (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || 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_ALLOC_MEM_MAP_TOGETHER | |
119 | def_bool y | |
120 | depends on SPARSEMEM && X86_64 | |
121 | ||
122 | config 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 | config HAVE_MEMBLOCK | |
132 | boolean | |
133 | ||
134 | # eventually, we can have this option just 'select SPARSEMEM' | |
135 | config 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 | ||
141 | config MEMORY_HOTPLUG_SPARSE | |
142 | def_bool y | |
143 | depends on SPARSEMEM && MEMORY_HOTPLUG | |
144 | ||
145 | config 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 | # | |
158 | config 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 | # | |
170 | config 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 | |
179 | config 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 | # | |
189 | config 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 | ||
201 | config PHYS_ADDR_T_64BIT | |
202 | def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT | |
203 | ||
204 | config ZONE_DMA_FLAG | |
205 | int | |
206 | default "0" if !ZONE_DMA | |
207 | default "1" | |
208 | ||
209 | config BOUNCE | |
210 | def_bool y | |
211 | depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) | |
212 | ||
213 | config NR_QUICK | |
214 | int | |
215 | depends on QUICKLIST | |
216 | default "2" if AVR32 | |
217 | default "1" | |
218 | ||
219 | config VIRT_TO_BUS | |
220 | def_bool y | |
221 | depends on !ARCH_NO_VIRT_TO_BUS | |
222 | ||
223 | config MMU_NOTIFIER | |
224 | bool | |
225 | ||
226 | config 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 | ||
240 | config 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 | ||
259 | config ARCH_SUPPORTS_MEMORY_FAILURE | |
260 | bool | |
261 | ||
262 | config 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 | ||
272 | config HWPOISON_INJECT | |
273 | tristate "HWPoison pages injector" | |
274 | depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS | |
275 | select PROC_PAGE_MONITOR | |
276 | ||
277 | config 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 | ||
305 | config 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 | ||
319 | choice | |
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. | |
341 | endchoice | |
342 | ||
343 | # | |
344 | # UP and nommu archs use km based percpu allocator | |
345 | # | |
346 | config NEED_PER_CPU_KM | |
347 | depends on !SMP | |
348 | bool | |
349 | default y | |
350 | ||
351 | config 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 |