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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 | cleancacne 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 |
373 |
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