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