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_VMEMMAP 119 bool "Sparse Memory virtual memmap" 120 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE 121 default y 122 help 123 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise 124 pfn_to_page and page_to_pfn operations. This is the most 125 efficient option when sufficient kernel resources are available. 126 127# eventually, we can have this option just 'select SPARSEMEM' 128config MEMORY_HOTPLUG 129 bool "Allow for memory hot-add" 130 depends on SPARSEMEM || X86_64_ACPI_NUMA 131 depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG 132 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390) 133 134config MEMORY_HOTPLUG_SPARSE 135 def_bool y 136 depends on SPARSEMEM && MEMORY_HOTPLUG 137 138config MEMORY_HOTREMOVE 139 bool "Allow for memory hot remove" 140 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 141 depends on MIGRATION 142 143# 144# If we have space for more page flags then we can enable additional 145# optimizations and functionality. 146# 147# Regular Sparsemem takes page flag bits for the sectionid if it does not 148# use a virtual memmap. Disable extended page flags for 32 bit platforms 149# that require the use of a sectionid in the page flags. 150# 151config PAGEFLAGS_EXTENDED 152 def_bool y 153 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM 154 155# Heavily threaded applications may benefit from splitting the mm-wide 156# page_table_lock, so that faults on different parts of the user address 157# space can be handled with less contention: split it at this NR_CPUS. 158# Default to 4 for wider testing, though 8 might be more appropriate. 159# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 160# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 161# 162config SPLIT_PTLOCK_CPUS 163 int 164 default "4096" if ARM && !CPU_CACHE_VIPT 165 default "4096" if PARISC && !PA20 166 default "4" 167 168# 169# support for page migration 170# 171config MIGRATION 172 bool "Page migration" 173 def_bool y 174 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE 175 help 176 Allows the migration of the physical location of pages of processes 177 while the virtual addresses are not changed. This is useful for 178 example on NUMA systems to put pages nearer to the processors accessing 179 the page. 180 181config PHYS_ADDR_T_64BIT 182 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 183 184config ZONE_DMA_FLAG 185 int 186 default "0" if !ZONE_DMA 187 default "1" 188 189config BOUNCE 190 def_bool y 191 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 192 193config NR_QUICK 194 int 195 depends on QUICKLIST 196 default "2" if SUPERH || AVR32 197 default "1" 198 199config VIRT_TO_BUS 200 def_bool y 201 depends on !ARCH_NO_VIRT_TO_BUS 202 203config HAVE_MLOCK 204 bool 205 default y if MMU=y 206 207config HAVE_MLOCKED_PAGE_BIT 208 bool 209 default y if HAVE_MLOCK=y 210 211config MMU_NOTIFIER 212 bool 213 214config KSM 215 bool "Enable KSM for page merging" 216 depends on MMU 217 help 218 Enable Kernel Samepage Merging: KSM periodically scans those areas 219 of an application's address space that an app has advised may be 220 mergeable. When it finds pages of identical content, it replaces 221 the many instances by a single resident page with that content, so 222 saving memory until one or another app needs to modify the content. 223 Recommended for use with KVM, or with other duplicative applications. 224 See Documentation/vm/ksm.txt for more information: KSM is inactive 225 until a program has madvised that an area is MADV_MERGEABLE, and 226 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 227 228config DEFAULT_MMAP_MIN_ADDR 229 int "Low address space to protect from user allocation" 230 default 4096 231 help 232 This is the portion of low virtual memory which should be protected 233 from userspace allocation. Keeping a user from writing to low pages 234 can help reduce the impact of kernel NULL pointer bugs. 235 236 For most ia64, ppc64 and x86 users with lots of address space 237 a value of 65536 is reasonable and should cause no problems. 238 On arm and other archs it should not be higher than 32768. 239 Programs which use vm86 functionality or have some need to map 240 this low address space will need CAP_SYS_RAWIO or disable this 241 protection by setting the value to 0. 242 243 This value can be changed after boot using the 244 /proc/sys/vm/mmap_min_addr tunable. 245 246config ARCH_SUPPORTS_MEMORY_FAILURE 247 bool 248 249config MEMORY_FAILURE 250 depends on MMU 251 depends on ARCH_SUPPORTS_MEMORY_FAILURE 252 bool "Enable recovery from hardware memory errors" 253 help 254 Enables code to recover from some memory failures on systems 255 with MCA recovery. This allows a system to continue running 256 even when some of its memory has uncorrected errors. This requires 257 special hardware support and typically ECC memory. 258 259config HWPOISON_INJECT 260 tristate "Poison pages injector" 261 depends on MEMORY_FAILURE && DEBUG_KERNEL 262 263config NOMMU_INITIAL_TRIM_EXCESS 264 int "Turn on mmap() excess space trimming before booting" 265 depends on !MMU 266 default 1 267 help 268 The NOMMU mmap() frequently needs to allocate large contiguous chunks 269 of memory on which to store mappings, but it can only ask the system 270 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 271 more than it requires. To deal with this, mmap() is able to trim off 272 the excess and return it to the allocator. 273 274 If trimming is enabled, the excess is trimmed off and returned to the 275 system allocator, which can cause extra fragmentation, particularly 276 if there are a lot of transient processes. 277 278 If trimming is disabled, the excess is kept, but not used, which for 279 long-term mappings means that the space is wasted. 280 281 Trimming can be dynamically controlled through a sysctl option 282 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 283 excess pages there must be before trimming should occur, or zero if 284 no trimming is to occur. 285 286 This option specifies the initial value of this option. The default 287 of 1 says that all excess pages should be trimmed. 288 289 See Documentation/nommu-mmap.txt for more information. 290