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 134config NO_BOOTMEM 135 boolean 136 137# eventually, we can have this option just 'select SPARSEMEM' 138config MEMORY_HOTPLUG 139 bool "Allow for memory hot-add" 140 depends on SPARSEMEM || X86_64_ACPI_NUMA 141 depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG 142 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390) 143 144config MEMORY_HOTPLUG_SPARSE 145 def_bool y 146 depends on SPARSEMEM && MEMORY_HOTPLUG 147 148config MEMORY_HOTREMOVE 149 bool "Allow for memory hot remove" 150 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 151 depends on MIGRATION 152 153# 154# If we have space for more page flags then we can enable additional 155# optimizations and functionality. 156# 157# Regular Sparsemem takes page flag bits for the sectionid if it does not 158# use a virtual memmap. Disable extended page flags for 32 bit platforms 159# that require the use of a sectionid in the page flags. 160# 161config PAGEFLAGS_EXTENDED 162 def_bool y 163 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM 164 165# Heavily threaded applications may benefit from splitting the mm-wide 166# page_table_lock, so that faults on different parts of the user address 167# space can be handled with less contention: split it at this NR_CPUS. 168# Default to 4 for wider testing, though 8 might be more appropriate. 169# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 170# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 171# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 172# 173config SPLIT_PTLOCK_CPUS 174 int 175 default "999999" if ARM && !CPU_CACHE_VIPT 176 default "999999" if PARISC && !PA20 177 default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC 178 default "4" 179 180# 181# support for memory compaction 182config COMPACTION 183 bool "Allow for memory compaction" 184 select MIGRATION 185 depends on MMU 186 help 187 Allows the compaction of memory for the allocation of huge pages. 188 189# 190# support for page migration 191# 192config MIGRATION 193 bool "Page migration" 194 def_bool y 195 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION 196 help 197 Allows the migration of the physical location of pages of processes 198 while the virtual addresses are not changed. This is useful in 199 two situations. The first is on NUMA systems to put pages nearer 200 to the processors accessing. The second is when allocating huge 201 pages as migration can relocate pages to satisfy a huge page 202 allocation instead of reclaiming. 203 204config PHYS_ADDR_T_64BIT 205 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 206 207config ZONE_DMA_FLAG 208 int 209 default "0" if !ZONE_DMA 210 default "1" 211 212config BOUNCE 213 def_bool y 214 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 215 216config NR_QUICK 217 int 218 depends on QUICKLIST 219 default "2" if AVR32 220 default "1" 221 222config VIRT_TO_BUS 223 def_bool y 224 depends on !ARCH_NO_VIRT_TO_BUS 225 226config MMU_NOTIFIER 227 bool 228 229config KSM 230 bool "Enable KSM for page merging" 231 depends on MMU 232 help 233 Enable Kernel Samepage Merging: KSM periodically scans those areas 234 of an application's address space that an app has advised may be 235 mergeable. When it finds pages of identical content, it replaces 236 the many instances by a single page with that content, so 237 saving memory until one or another app needs to modify the content. 238 Recommended for use with KVM, or with other duplicative applications. 239 See Documentation/vm/ksm.txt for more information: KSM is inactive 240 until a program has madvised that an area is MADV_MERGEABLE, and 241 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 242 243config DEFAULT_MMAP_MIN_ADDR 244 int "Low address space to protect from user allocation" 245 depends on MMU 246 default 4096 247 help 248 This is the portion of low virtual memory which should be protected 249 from userspace allocation. Keeping a user from writing to low pages 250 can help reduce the impact of kernel NULL pointer bugs. 251 252 For most ia64, ppc64 and x86 users with lots of address space 253 a value of 65536 is reasonable and should cause no problems. 254 On arm and other archs it should not be higher than 32768. 255 Programs which use vm86 functionality or have some need to map 256 this low address space will need CAP_SYS_RAWIO or disable this 257 protection by setting the value to 0. 258 259 This value can be changed after boot using the 260 /proc/sys/vm/mmap_min_addr tunable. 261 262config ARCH_SUPPORTS_MEMORY_FAILURE 263 bool 264 265config MEMORY_FAILURE 266 depends on MMU 267 depends on ARCH_SUPPORTS_MEMORY_FAILURE 268 bool "Enable recovery from hardware memory errors" 269 help 270 Enables code to recover from some memory failures on systems 271 with MCA recovery. This allows a system to continue running 272 even when some of its memory has uncorrected errors. This requires 273 special hardware support and typically ECC memory. 274 275config HWPOISON_INJECT 276 tristate "HWPoison pages injector" 277 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 278 select PROC_PAGE_MONITOR 279 280config NOMMU_INITIAL_TRIM_EXCESS 281 int "Turn on mmap() excess space trimming before booting" 282 depends on !MMU 283 default 1 284 help 285 The NOMMU mmap() frequently needs to allocate large contiguous chunks 286 of memory on which to store mappings, but it can only ask the system 287 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 288 more than it requires. To deal with this, mmap() is able to trim off 289 the excess and return it to the allocator. 290 291 If trimming is enabled, the excess is trimmed off and returned to the 292 system allocator, which can cause extra fragmentation, particularly 293 if there are a lot of transient processes. 294 295 If trimming is disabled, the excess is kept, but not used, which for 296 long-term mappings means that the space is wasted. 297 298 Trimming can be dynamically controlled through a sysctl option 299 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 300 excess pages there must be before trimming should occur, or zero if 301 no trimming is to occur. 302 303 This option specifies the initial value of this option. The default 304 of 1 says that all excess pages should be trimmed. 305 306 See Documentation/nommu-mmap.txt for more information. 307 308config TRANSPARENT_HUGEPAGE 309 bool "Transparent Hugepage Support" 310 depends on X86 && MMU 311 select COMPACTION 312 help 313 Transparent Hugepages allows the kernel to use huge pages and 314 huge tlb transparently to the applications whenever possible. 315 This feature can improve computing performance to certain 316 applications by speeding up page faults during memory 317 allocation, by reducing the number of tlb misses and by speeding 318 up the pagetable walking. 319 320 If memory constrained on embedded, you may want to say N. 321 322choice 323 prompt "Transparent Hugepage Support sysfs defaults" 324 depends on TRANSPARENT_HUGEPAGE 325 default TRANSPARENT_HUGEPAGE_ALWAYS 326 help 327 Selects the sysfs defaults for Transparent Hugepage Support. 328 329 config TRANSPARENT_HUGEPAGE_ALWAYS 330 bool "always" 331 help 332 Enabling Transparent Hugepage always, can increase the 333 memory footprint of applications without a guaranteed 334 benefit but it will work automatically for all applications. 335 336 config TRANSPARENT_HUGEPAGE_MADVISE 337 bool "madvise" 338 help 339 Enabling Transparent Hugepage madvise, will only provide a 340 performance improvement benefit to the applications using 341 madvise(MADV_HUGEPAGE) but it won't risk to increase the 342 memory footprint of applications without a guaranteed 343 benefit. 344endchoice 345 346# 347# UP and nommu archs use km based percpu allocator 348# 349config NEED_PER_CPU_KM 350 depends on !SMP 351 bool 352 default y 353 354config CLEANCACHE 355 bool "Enable cleancache driver to cache clean pages if tmem is present" 356 default n 357 help 358 Cleancache can be thought of as a page-granularity victim cache 359 for clean pages that the kernel's pageframe replacement algorithm 360 (PFRA) would like to keep around, but can't since there isn't enough 361 memory. So when the PFRA "evicts" a page, it first attempts to use 362 cleancache code to put the data contained in that page into 363 "transcendent memory", memory that is not directly accessible or 364 addressable by the kernel and is of unknown and possibly 365 time-varying size. And when a cleancache-enabled 366 filesystem wishes to access a page in a file on disk, it first 367 checks cleancache to see if it already contains it; if it does, 368 the page is copied into the kernel and a disk access is avoided. 369 When a transcendent memory driver is available (such as zcache or 370 Xen transcendent memory), a significant I/O reduction 371 may be achieved. When none is available, all cleancache calls 372 are reduced to a single pointer-compare-against-NULL resulting 373 in a negligible performance hit. 374 375 If unsure, say Y to enable cleancache 376