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 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 && !HIBERNATION && ARCH_ENABLE_MEMORY_HOTPLUG 132 depends on (IA64 || X86 || PPC64 || SUPERH || S390) 133 134comment "Memory hotplug is currently incompatible with Software Suspend" 135 depends on SPARSEMEM && HOTPLUG && HIBERNATION 136 137config MEMORY_HOTPLUG_SPARSE 138 def_bool y 139 depends on SPARSEMEM && MEMORY_HOTPLUG 140 141config MEMORY_HOTREMOVE 142 bool "Allow for memory hot remove" 143 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 144 depends on MIGRATION 145 146# 147# If we have space for more page flags then we can enable additional 148# optimizations and functionality. 149# 150# Regular Sparsemem takes page flag bits for the sectionid if it does not 151# use a virtual memmap. Disable extended page flags for 32 bit platforms 152# that require the use of a sectionid in the page flags. 153# 154config PAGEFLAGS_EXTENDED 155 def_bool y 156 depends on 64BIT || SPARSEMEM_VMEMMAP || !NUMA || !SPARSEMEM 157 158# Heavily threaded applications may benefit from splitting the mm-wide 159# page_table_lock, so that faults on different parts of the user address 160# space can be handled with less contention: split it at this NR_CPUS. 161# Default to 4 for wider testing, though 8 might be more appropriate. 162# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 163# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 164# 165config SPLIT_PTLOCK_CPUS 166 int 167 default "4096" if ARM && !CPU_CACHE_VIPT 168 default "4096" if PARISC && !PA20 169 default "4" 170 171# 172# support for page migration 173# 174config MIGRATION 175 bool "Page migration" 176 def_bool y 177 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE 178 help 179 Allows the migration of the physical location of pages of processes 180 while the virtual addresses are not changed. This is useful for 181 example on NUMA systems to put pages nearer to the processors accessing 182 the page. 183 184config PHYS_ADDR_T_64BIT 185 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 186 187config ZONE_DMA_FLAG 188 int 189 default "0" if !ZONE_DMA 190 default "1" 191 192config BOUNCE 193 def_bool y 194 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 195 196config NR_QUICK 197 int 198 depends on QUICKLIST 199 default "2" if SUPERH || AVR32 200 default "1" 201 202config VIRT_TO_BUS 203 def_bool y 204 depends on !ARCH_NO_VIRT_TO_BUS 205 206config UNEVICTABLE_LRU 207 bool "Add LRU list to track non-evictable pages" 208 default y 209 depends on MMU 210 help 211 Keeps unevictable pages off of the active and inactive pageout 212 lists, so kswapd will not waste CPU time or have its balancing 213 algorithms thrown off by scanning these pages. Selecting this 214 will use one page flag and increase the code size a little, 215 say Y unless you know what you are doing. 216 217config MMU_NOTIFIER 218 bool 219 220config DEFAULT_MMAP_MIN_ADDR 221 int "Low address space to protect from user allocation" 222 default 4096 223 help 224 This is the portion of low virtual memory which should be protected 225 from userspace allocation. Keeping a user from writing to low pages 226 can help reduce the impact of kernel NULL pointer bugs. 227 228 For most ia64, ppc64 and x86 users with lots of address space 229 a value of 65536 is reasonable and should cause no problems. 230 On arm and other archs it should not be higher than 32768. 231 Programs which use vm86 functionality would either need additional 232 permissions from either the LSM or the capabilities module or have 233 this protection disabled. 234 235 This value can be changed after boot using the 236 /proc/sys/vm/mmap_min_addr tunable. 237