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# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 162# 163config SPLIT_PTLOCK_CPUS 164 int 165 default "999999" if ARM && !CPU_CACHE_VIPT 166 default "999999" if PARISC && !PA20 167 default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC 168 default "4" 169 170# 171# support for page migration 172# 173config MIGRATION 174 bool "Page migration" 175 def_bool y 176 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE 177 help 178 Allows the migration of the physical location of pages of processes 179 while the virtual addresses are not changed. This is useful for 180 example on NUMA systems to put pages nearer to the processors accessing 181 the page. 182 183config PHYS_ADDR_T_64BIT 184 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 185 186config ZONE_DMA_FLAG 187 int 188 default "0" if !ZONE_DMA 189 default "1" 190 191config BOUNCE 192 def_bool y 193 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 194 195config NR_QUICK 196 int 197 depends on QUICKLIST 198 default "2" if SUPERH || AVR32 199 default "1" 200 201config VIRT_TO_BUS 202 def_bool y 203 depends on !ARCH_NO_VIRT_TO_BUS 204 205config MMU_NOTIFIER 206 bool 207 208config KSM 209 bool "Enable KSM for page merging" 210 depends on MMU 211 help 212 Enable Kernel Samepage Merging: KSM periodically scans those areas 213 of an application's address space that an app has advised may be 214 mergeable. When it finds pages of identical content, it replaces 215 the many instances by a single page with that content, so 216 saving memory until one or another app needs to modify the content. 217 Recommended for use with KVM, or with other duplicative applications. 218 See Documentation/vm/ksm.txt for more information: KSM is inactive 219 until a program has madvised that an area is MADV_MERGEABLE, and 220 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 221 222config DEFAULT_MMAP_MIN_ADDR 223 int "Low address space to protect from user allocation" 224 depends on MMU 225 default 4096 226 help 227 This is the portion of low virtual memory which should be protected 228 from userspace allocation. Keeping a user from writing to low pages 229 can help reduce the impact of kernel NULL pointer bugs. 230 231 For most ia64, ppc64 and x86 users with lots of address space 232 a value of 65536 is reasonable and should cause no problems. 233 On arm and other archs it should not be higher than 32768. 234 Programs which use vm86 functionality or have some need to map 235 this low address space will need CAP_SYS_RAWIO or disable this 236 protection by setting the value to 0. 237 238 This value can be changed after boot using the 239 /proc/sys/vm/mmap_min_addr tunable. 240 241config ARCH_SUPPORTS_MEMORY_FAILURE 242 bool 243 244config MEMORY_FAILURE 245 depends on MMU 246 depends on ARCH_SUPPORTS_MEMORY_FAILURE 247 bool "Enable recovery from hardware memory errors" 248 help 249 Enables code to recover from some memory failures on systems 250 with MCA recovery. This allows a system to continue running 251 even when some of its memory has uncorrected errors. This requires 252 special hardware support and typically ECC memory. 253 254config HWPOISON_INJECT 255 tristate "HWPoison pages injector" 256 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 257 select PROC_PAGE_MONITOR 258 259config NOMMU_INITIAL_TRIM_EXCESS 260 int "Turn on mmap() excess space trimming before booting" 261 depends on !MMU 262 default 1 263 help 264 The NOMMU mmap() frequently needs to allocate large contiguous chunks 265 of memory on which to store mappings, but it can only ask the system 266 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 267 more than it requires. To deal with this, mmap() is able to trim off 268 the excess and return it to the allocator. 269 270 If trimming is enabled, the excess is trimmed off and returned to the 271 system allocator, which can cause extra fragmentation, particularly 272 if there are a lot of transient processes. 273 274 If trimming is disabled, the excess is kept, but not used, which for 275 long-term mappings means that the space is wasted. 276 277 Trimming can be dynamically controlled through a sysctl option 278 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 279 excess pages there must be before trimming should occur, or zero if 280 no trimming is to occur. 281 282 This option specifies the initial value of this option. The default 283 of 1 says that all excess pages should be trimmed. 284 285 See Documentation/nommu-mmap.txt for more information. 286