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 def_bool y 195 select MIGRATION 196 depends on MMU 197 help 198 Allows the compaction of memory for the allocation of huge pages. 199 200# 201# support for page migration 202# 203config MIGRATION 204 bool "Page migration" 205 def_bool y 206 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA 207 help 208 Allows the migration of the physical location of pages of processes 209 while the virtual addresses are not changed. This is useful in 210 two situations. The first is on NUMA systems to put pages nearer 211 to the processors accessing. The second is when allocating huge 212 pages as migration can relocate pages to satisfy a huge page 213 allocation instead of reclaiming. 214 215config PHYS_ADDR_T_64BIT 216 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 217 218config ZONE_DMA_FLAG 219 int 220 default "0" if !ZONE_DMA 221 default "1" 222 223config BOUNCE 224 def_bool y 225 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 226 227config NR_QUICK 228 int 229 depends on QUICKLIST 230 default "2" if AVR32 231 default "1" 232 233config VIRT_TO_BUS 234 def_bool y 235 depends on !ARCH_NO_VIRT_TO_BUS 236 237config MMU_NOTIFIER 238 bool 239 240config KSM 241 bool "Enable KSM for page merging" 242 depends on MMU 243 help 244 Enable Kernel Samepage Merging: KSM periodically scans those areas 245 of an application's address space that an app has advised may be 246 mergeable. When it finds pages of identical content, it replaces 247 the many instances by a single page with that content, so 248 saving memory until one or another app needs to modify the content. 249 Recommended for use with KVM, or with other duplicative applications. 250 See Documentation/vm/ksm.txt for more information: KSM is inactive 251 until a program has madvised that an area is MADV_MERGEABLE, and 252 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 253 254config DEFAULT_MMAP_MIN_ADDR 255 int "Low address space to protect from user allocation" 256 depends on MMU 257 default 4096 258 help 259 This is the portion of low virtual memory which should be protected 260 from userspace allocation. Keeping a user from writing to low pages 261 can help reduce the impact of kernel NULL pointer bugs. 262 263 For most ia64, ppc64 and x86 users with lots of address space 264 a value of 65536 is reasonable and should cause no problems. 265 On arm and other archs it should not be higher than 32768. 266 Programs which use vm86 functionality or have some need to map 267 this low address space will need CAP_SYS_RAWIO or disable this 268 protection by setting the value to 0. 269 270 This value can be changed after boot using the 271 /proc/sys/vm/mmap_min_addr tunable. 272 273config ARCH_SUPPORTS_MEMORY_FAILURE 274 bool 275 276config MEMORY_FAILURE 277 depends on MMU 278 depends on ARCH_SUPPORTS_MEMORY_FAILURE 279 bool "Enable recovery from hardware memory errors" 280 select MEMORY_ISOLATION 281 help 282 Enables code to recover from some memory failures on systems 283 with MCA recovery. This allows a system to continue running 284 even when some of its memory has uncorrected errors. This requires 285 special hardware support and typically ECC memory. 286 287config HWPOISON_INJECT 288 tristate "HWPoison pages injector" 289 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 290 select PROC_PAGE_MONITOR 291 292config NOMMU_INITIAL_TRIM_EXCESS 293 int "Turn on mmap() excess space trimming before booting" 294 depends on !MMU 295 default 1 296 help 297 The NOMMU mmap() frequently needs to allocate large contiguous chunks 298 of memory on which to store mappings, but it can only ask the system 299 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 300 more than it requires. To deal with this, mmap() is able to trim off 301 the excess and return it to the allocator. 302 303 If trimming is enabled, the excess is trimmed off and returned to the 304 system allocator, which can cause extra fragmentation, particularly 305 if there are a lot of transient processes. 306 307 If trimming is disabled, the excess is kept, but not used, which for 308 long-term mappings means that the space is wasted. 309 310 Trimming can be dynamically controlled through a sysctl option 311 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 312 excess pages there must be before trimming should occur, or zero if 313 no trimming is to occur. 314 315 This option specifies the initial value of this option. The default 316 of 1 says that all excess pages should be trimmed. 317 318 See Documentation/nommu-mmap.txt for more information. 319 320config TRANSPARENT_HUGEPAGE 321 bool "Transparent Hugepage Support" 322 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 323 select COMPACTION 324 help 325 Transparent Hugepages allows the kernel to use huge pages and 326 huge tlb transparently to the applications whenever possible. 327 This feature can improve computing performance to certain 328 applications by speeding up page faults during memory 329 allocation, by reducing the number of tlb misses and by speeding 330 up the pagetable walking. 331 332 If memory constrained on embedded, you may want to say N. 333 334choice 335 prompt "Transparent Hugepage Support sysfs defaults" 336 depends on TRANSPARENT_HUGEPAGE 337 default TRANSPARENT_HUGEPAGE_ALWAYS 338 help 339 Selects the sysfs defaults for Transparent Hugepage Support. 340 341 config TRANSPARENT_HUGEPAGE_ALWAYS 342 bool "always" 343 help 344 Enabling Transparent Hugepage always, can increase the 345 memory footprint of applications without a guaranteed 346 benefit but it will work automatically for all applications. 347 348 config TRANSPARENT_HUGEPAGE_MADVISE 349 bool "madvise" 350 help 351 Enabling Transparent Hugepage madvise, will only provide a 352 performance improvement benefit to the applications using 353 madvise(MADV_HUGEPAGE) but it won't risk to increase the 354 memory footprint of applications without a guaranteed 355 benefit. 356endchoice 357 358config CROSS_MEMORY_ATTACH 359 bool "Cross Memory Support" 360 depends on MMU 361 default y 362 help 363 Enabling this option adds the system calls process_vm_readv and 364 process_vm_writev which allow a process with the correct privileges 365 to directly read from or write to to another process's address space. 366 See the man page for more details. 367 368# 369# UP and nommu archs use km based percpu allocator 370# 371config NEED_PER_CPU_KM 372 depends on !SMP 373 bool 374 default y 375 376config CLEANCACHE 377 bool "Enable cleancache driver to cache clean pages if tmem is present" 378 default n 379 help 380 Cleancache can be thought of as a page-granularity victim cache 381 for clean pages that the kernel's pageframe replacement algorithm 382 (PFRA) would like to keep around, but can't since there isn't enough 383 memory. So when the PFRA "evicts" a page, it first attempts to use 384 cleancache code to put the data contained in that page into 385 "transcendent memory", memory that is not directly accessible or 386 addressable by the kernel and is of unknown and possibly 387 time-varying size. And when a cleancache-enabled 388 filesystem wishes to access a page in a file on disk, it first 389 checks cleancache to see if it already contains it; if it does, 390 the page is copied into the kernel and a disk access is avoided. 391 When a transcendent memory driver is available (such as zcache or 392 Xen transcendent memory), a significant I/O reduction 393 may be achieved. When none is available, all cleancache calls 394 are reduced to a single pointer-compare-against-NULL resulting 395 in a negligible performance hit. 396 397 If unsure, say Y to enable cleancache 398 399config FRONTSWAP 400 bool "Enable frontswap to cache swap pages if tmem is present" 401 depends on SWAP 402 default n 403 help 404 Frontswap is so named because it can be thought of as the opposite 405 of a "backing" store for a swap device. The data is stored into 406 "transcendent memory", memory that is not directly accessible or 407 addressable by the kernel and is of unknown and possibly 408 time-varying size. When space in transcendent memory is available, 409 a significant swap I/O reduction may be achieved. When none is 410 available, all frontswap calls are reduced to a single pointer- 411 compare-against-NULL resulting in a negligible performance hit 412 and swap data is stored as normal on the matching swap device. 413 414 If unsure, say Y to enable frontswap. 415