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 HAVE_MEMBLOCK_NODE_MAP 135 boolean 136 137config ARCH_DISCARD_MEMBLOCK 138 boolean 139 140config NO_BOOTMEM 141 boolean 142 143config MEMORY_ISOLATION 144 boolean 145 146# eventually, we can have this option just 'select SPARSEMEM' 147config MEMORY_HOTPLUG 148 bool "Allow for memory hot-add" 149 select MEMORY_ISOLATION 150 depends on SPARSEMEM || X86_64_ACPI_NUMA 151 depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG 152 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390) 153 154config MEMORY_HOTPLUG_SPARSE 155 def_bool y 156 depends on SPARSEMEM && MEMORY_HOTPLUG 157 158config MEMORY_HOTREMOVE 159 bool "Allow for memory hot remove" 160 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 161 depends on MIGRATION 162 163# 164# If we have space for more page flags then we can enable additional 165# optimizations and functionality. 166# 167# Regular Sparsemem takes page flag bits for the sectionid if it does not 168# use a virtual memmap. Disable extended page flags for 32 bit platforms 169# that require the use of a sectionid in the page flags. 170# 171config PAGEFLAGS_EXTENDED 172 def_bool y 173 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM 174 175# Heavily threaded applications may benefit from splitting the mm-wide 176# page_table_lock, so that faults on different parts of the user address 177# space can be handled with less contention: split it at this NR_CPUS. 178# Default to 4 for wider testing, though 8 might be more appropriate. 179# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 180# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 181# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 182# 183config SPLIT_PTLOCK_CPUS 184 int 185 default "999999" if ARM && !CPU_CACHE_VIPT 186 default "999999" if PARISC && !PA20 187 default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC 188 default "4" 189 190# 191# support for memory compaction 192config COMPACTION 193 bool "Allow for memory compaction" 194 select MIGRATION 195 depends on MMU 196 help 197 Allows the compaction of memory for the allocation of huge pages. 198 199# 200# support for page migration 201# 202config MIGRATION 203 bool "Page migration" 204 def_bool y 205 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA 206 help 207 Allows the migration of the physical location of pages of processes 208 while the virtual addresses are not changed. This is useful in 209 two situations. The first is on NUMA systems to put pages nearer 210 to the processors accessing. The second is when allocating huge 211 pages as migration can relocate pages to satisfy a huge page 212 allocation instead of reclaiming. 213 214config PHYS_ADDR_T_64BIT 215 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 216 217config ZONE_DMA_FLAG 218 int 219 default "0" if !ZONE_DMA 220 default "1" 221 222config BOUNCE 223 def_bool y 224 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 225 226config NR_QUICK 227 int 228 depends on QUICKLIST 229 default "2" if AVR32 230 default "1" 231 232config VIRT_TO_BUS 233 def_bool y 234 depends on !ARCH_NO_VIRT_TO_BUS 235 236config MMU_NOTIFIER 237 bool 238 239config KSM 240 bool "Enable KSM for page merging" 241 depends on MMU 242 help 243 Enable Kernel Samepage Merging: KSM periodically scans those areas 244 of an application's address space that an app has advised may be 245 mergeable. When it finds pages of identical content, it replaces 246 the many instances by a single page with that content, so 247 saving memory until one or another app needs to modify the content. 248 Recommended for use with KVM, or with other duplicative applications. 249 See Documentation/vm/ksm.txt for more information: KSM is inactive 250 until a program has madvised that an area is MADV_MERGEABLE, and 251 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 252 253config DEFAULT_MMAP_MIN_ADDR 254 int "Low address space to protect from user allocation" 255 depends on MMU 256 default 4096 257 help 258 This is the portion of low virtual memory which should be protected 259 from userspace allocation. Keeping a user from writing to low pages 260 can help reduce the impact of kernel NULL pointer bugs. 261 262 For most ia64, ppc64 and x86 users with lots of address space 263 a value of 65536 is reasonable and should cause no problems. 264 On arm and other archs it should not be higher than 32768. 265 Programs which use vm86 functionality or have some need to map 266 this low address space will need CAP_SYS_RAWIO or disable this 267 protection by setting the value to 0. 268 269 This value can be changed after boot using the 270 /proc/sys/vm/mmap_min_addr tunable. 271 272config ARCH_SUPPORTS_MEMORY_FAILURE 273 bool 274 275config MEMORY_FAILURE 276 depends on MMU 277 depends on ARCH_SUPPORTS_MEMORY_FAILURE 278 bool "Enable recovery from hardware memory errors" 279 select MEMORY_ISOLATION 280 help 281 Enables code to recover from some memory failures on systems 282 with MCA recovery. This allows a system to continue running 283 even when some of its memory has uncorrected errors. This requires 284 special hardware support and typically ECC memory. 285 286config HWPOISON_INJECT 287 tristate "HWPoison pages injector" 288 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 289 select PROC_PAGE_MONITOR 290 291config NOMMU_INITIAL_TRIM_EXCESS 292 int "Turn on mmap() excess space trimming before booting" 293 depends on !MMU 294 default 1 295 help 296 The NOMMU mmap() frequently needs to allocate large contiguous chunks 297 of memory on which to store mappings, but it can only ask the system 298 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 299 more than it requires. To deal with this, mmap() is able to trim off 300 the excess and return it to the allocator. 301 302 If trimming is enabled, the excess is trimmed off and returned to the 303 system allocator, which can cause extra fragmentation, particularly 304 if there are a lot of transient processes. 305 306 If trimming is disabled, the excess is kept, but not used, which for 307 long-term mappings means that the space is wasted. 308 309 Trimming can be dynamically controlled through a sysctl option 310 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 311 excess pages there must be before trimming should occur, or zero if 312 no trimming is to occur. 313 314 This option specifies the initial value of this option. The default 315 of 1 says that all excess pages should be trimmed. 316 317 See Documentation/nommu-mmap.txt for more information. 318 319config TRANSPARENT_HUGEPAGE 320 bool "Transparent Hugepage Support" 321 depends on X86 && MMU 322 select COMPACTION 323 help 324 Transparent Hugepages allows the kernel to use huge pages and 325 huge tlb transparently to the applications whenever possible. 326 This feature can improve computing performance to certain 327 applications by speeding up page faults during memory 328 allocation, by reducing the number of tlb misses and by speeding 329 up the pagetable walking. 330 331 If memory constrained on embedded, you may want to say N. 332 333choice 334 prompt "Transparent Hugepage Support sysfs defaults" 335 depends on TRANSPARENT_HUGEPAGE 336 default TRANSPARENT_HUGEPAGE_ALWAYS 337 help 338 Selects the sysfs defaults for Transparent Hugepage Support. 339 340 config TRANSPARENT_HUGEPAGE_ALWAYS 341 bool "always" 342 help 343 Enabling Transparent Hugepage always, can increase the 344 memory footprint of applications without a guaranteed 345 benefit but it will work automatically for all applications. 346 347 config TRANSPARENT_HUGEPAGE_MADVISE 348 bool "madvise" 349 help 350 Enabling Transparent Hugepage madvise, will only provide a 351 performance improvement benefit to the applications using 352 madvise(MADV_HUGEPAGE) but it won't risk to increase the 353 memory footprint of applications without a guaranteed 354 benefit. 355endchoice 356 357config CROSS_MEMORY_ATTACH 358 bool "Cross Memory Support" 359 depends on MMU 360 default y 361 help 362 Enabling this option adds the system calls process_vm_readv and 363 process_vm_writev which allow a process with the correct privileges 364 to directly read from or write to to another process's address space. 365 See the man page for more details. 366 367# 368# UP and nommu archs use km based percpu allocator 369# 370config NEED_PER_CPU_KM 371 depends on !SMP 372 bool 373 default y 374 375config CLEANCACHE 376 bool "Enable cleancache driver to cache clean pages if tmem is present" 377 default n 378 help 379 Cleancache can be thought of as a page-granularity victim cache 380 for clean pages that the kernel's pageframe replacement algorithm 381 (PFRA) would like to keep around, but can't since there isn't enough 382 memory. So when the PFRA "evicts" a page, it first attempts to use 383 cleancache code to put the data contained in that page into 384 "transcendent memory", memory that is not directly accessible or 385 addressable by the kernel and is of unknown and possibly 386 time-varying size. And when a cleancache-enabled 387 filesystem wishes to access a page in a file on disk, it first 388 checks cleancache to see if it already contains it; if it does, 389 the page is copied into the kernel and a disk access is avoided. 390 When a transcendent memory driver is available (such as zcache or 391 Xen transcendent memory), a significant I/O reduction 392 may be achieved. When none is available, all cleancache calls 393 are reduced to a single pointer-compare-against-NULL resulting 394 in a negligible performance hit. 395 396 If unsure, say Y to enable cleancache 397 398config FRONTSWAP 399 bool "Enable frontswap to cache swap pages if tmem is present" 400 depends on SWAP 401 default n 402 help 403 Frontswap is so named because it can be thought of as the opposite 404 of a "backing" store for a swap device. The data is stored into 405 "transcendent memory", memory that is not directly accessible or 406 addressable by the kernel and is of unknown and possibly 407 time-varying size. When space in transcendent memory is available, 408 a significant swap I/O reduction may be achieved. When none is 409 available, all frontswap calls are reduced to a single pointer- 410 compare-against-NULL resulting in a negligible performance hit 411 and swap data is stored as normal on the matching swap device. 412 413 If unsure, say Y to enable frontswap. 414