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 146config MOVABLE_NODE 147 boolean "Enable to assign a node which has only movable memory" 148 depends on HAVE_MEMBLOCK 149 depends on NO_BOOTMEM 150 depends on X86_64 151 depends on NUMA 152 depends on BROKEN 153 154# eventually, we can have this option just 'select SPARSEMEM' 155config MEMORY_HOTPLUG 156 bool "Allow for memory hot-add" 157 select MEMORY_ISOLATION 158 depends on SPARSEMEM || X86_64_ACPI_NUMA 159 depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG 160 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390) 161 162config MEMORY_HOTPLUG_SPARSE 163 def_bool y 164 depends on SPARSEMEM && MEMORY_HOTPLUG 165 166config MEMORY_HOTREMOVE 167 bool "Allow for memory hot remove" 168 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 169 depends on MIGRATION 170 171# 172# If we have space for more page flags then we can enable additional 173# optimizations and functionality. 174# 175# Regular Sparsemem takes page flag bits for the sectionid if it does not 176# use a virtual memmap. Disable extended page flags for 32 bit platforms 177# that require the use of a sectionid in the page flags. 178# 179config PAGEFLAGS_EXTENDED 180 def_bool y 181 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM 182 183# Heavily threaded applications may benefit from splitting the mm-wide 184# page_table_lock, so that faults on different parts of the user address 185# space can be handled with less contention: split it at this NR_CPUS. 186# Default to 4 for wider testing, though 8 might be more appropriate. 187# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 188# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 189# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 190# 191config SPLIT_PTLOCK_CPUS 192 int 193 default "999999" if ARM && !CPU_CACHE_VIPT 194 default "999999" if PARISC && !PA20 195 default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC 196 default "4" 197 198# 199# support for memory balloon compaction 200config BALLOON_COMPACTION 201 bool "Allow for balloon memory compaction/migration" 202 def_bool y 203 depends on COMPACTION && VIRTIO_BALLOON 204 help 205 Memory fragmentation introduced by ballooning might reduce 206 significantly the number of 2MB contiguous memory blocks that can be 207 used within a guest, thus imposing performance penalties associated 208 with the reduced number of transparent huge pages that could be used 209 by the guest workload. Allowing the compaction & migration for memory 210 pages enlisted as being part of memory balloon devices avoids the 211 scenario aforementioned and helps improving memory defragmentation. 212 213# 214# support for memory compaction 215config COMPACTION 216 bool "Allow for memory compaction" 217 def_bool y 218 select MIGRATION 219 depends on MMU 220 help 221 Allows the compaction of memory for the allocation of huge pages. 222 223# 224# support for page migration 225# 226config MIGRATION 227 bool "Page migration" 228 def_bool y 229 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA 230 help 231 Allows the migration of the physical location of pages of processes 232 while the virtual addresses are not changed. This is useful in 233 two situations. The first is on NUMA systems to put pages nearer 234 to the processors accessing. The second is when allocating huge 235 pages as migration can relocate pages to satisfy a huge page 236 allocation instead of reclaiming. 237 238config PHYS_ADDR_T_64BIT 239 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 240 241config ZONE_DMA_FLAG 242 int 243 default "0" if !ZONE_DMA 244 default "1" 245 246config BOUNCE 247 def_bool y 248 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 249 250config NR_QUICK 251 int 252 depends on QUICKLIST 253 default "2" if AVR32 254 default "1" 255 256config VIRT_TO_BUS 257 def_bool y 258 depends on !ARCH_NO_VIRT_TO_BUS 259 260config MMU_NOTIFIER 261 bool 262 263config KSM 264 bool "Enable KSM for page merging" 265 depends on MMU 266 help 267 Enable Kernel Samepage Merging: KSM periodically scans those areas 268 of an application's address space that an app has advised may be 269 mergeable. When it finds pages of identical content, it replaces 270 the many instances by a single page with that content, so 271 saving memory until one or another app needs to modify the content. 272 Recommended for use with KVM, or with other duplicative applications. 273 See Documentation/vm/ksm.txt for more information: KSM is inactive 274 until a program has madvised that an area is MADV_MERGEABLE, and 275 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 276 277config DEFAULT_MMAP_MIN_ADDR 278 int "Low address space to protect from user allocation" 279 depends on MMU 280 default 4096 281 help 282 This is the portion of low virtual memory which should be protected 283 from userspace allocation. Keeping a user from writing to low pages 284 can help reduce the impact of kernel NULL pointer bugs. 285 286 For most ia64, ppc64 and x86 users with lots of address space 287 a value of 65536 is reasonable and should cause no problems. 288 On arm and other archs it should not be higher than 32768. 289 Programs which use vm86 functionality or have some need to map 290 this low address space will need CAP_SYS_RAWIO or disable this 291 protection by setting the value to 0. 292 293 This value can be changed after boot using the 294 /proc/sys/vm/mmap_min_addr tunable. 295 296config ARCH_SUPPORTS_MEMORY_FAILURE 297 bool 298 299config MEMORY_FAILURE 300 depends on MMU 301 depends on ARCH_SUPPORTS_MEMORY_FAILURE 302 bool "Enable recovery from hardware memory errors" 303 select MEMORY_ISOLATION 304 help 305 Enables code to recover from some memory failures on systems 306 with MCA recovery. This allows a system to continue running 307 even when some of its memory has uncorrected errors. This requires 308 special hardware support and typically ECC memory. 309 310config HWPOISON_INJECT 311 tristate "HWPoison pages injector" 312 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 313 select PROC_PAGE_MONITOR 314 315config NOMMU_INITIAL_TRIM_EXCESS 316 int "Turn on mmap() excess space trimming before booting" 317 depends on !MMU 318 default 1 319 help 320 The NOMMU mmap() frequently needs to allocate large contiguous chunks 321 of memory on which to store mappings, but it can only ask the system 322 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 323 more than it requires. To deal with this, mmap() is able to trim off 324 the excess and return it to the allocator. 325 326 If trimming is enabled, the excess is trimmed off and returned to the 327 system allocator, which can cause extra fragmentation, particularly 328 if there are a lot of transient processes. 329 330 If trimming is disabled, the excess is kept, but not used, which for 331 long-term mappings means that the space is wasted. 332 333 Trimming can be dynamically controlled through a sysctl option 334 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 335 excess pages there must be before trimming should occur, or zero if 336 no trimming is to occur. 337 338 This option specifies the initial value of this option. The default 339 of 1 says that all excess pages should be trimmed. 340 341 See Documentation/nommu-mmap.txt for more information. 342 343config TRANSPARENT_HUGEPAGE 344 bool "Transparent Hugepage Support" 345 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 346 select COMPACTION 347 help 348 Transparent Hugepages allows the kernel to use huge pages and 349 huge tlb transparently to the applications whenever possible. 350 This feature can improve computing performance to certain 351 applications by speeding up page faults during memory 352 allocation, by reducing the number of tlb misses and by speeding 353 up the pagetable walking. 354 355 If memory constrained on embedded, you may want to say N. 356 357choice 358 prompt "Transparent Hugepage Support sysfs defaults" 359 depends on TRANSPARENT_HUGEPAGE 360 default TRANSPARENT_HUGEPAGE_ALWAYS 361 help 362 Selects the sysfs defaults for Transparent Hugepage Support. 363 364 config TRANSPARENT_HUGEPAGE_ALWAYS 365 bool "always" 366 help 367 Enabling Transparent Hugepage always, can increase the 368 memory footprint of applications without a guaranteed 369 benefit but it will work automatically for all applications. 370 371 config TRANSPARENT_HUGEPAGE_MADVISE 372 bool "madvise" 373 help 374 Enabling Transparent Hugepage madvise, will only provide a 375 performance improvement benefit to the applications using 376 madvise(MADV_HUGEPAGE) but it won't risk to increase the 377 memory footprint of applications without a guaranteed 378 benefit. 379endchoice 380 381config CROSS_MEMORY_ATTACH 382 bool "Cross Memory Support" 383 depends on MMU 384 default y 385 help 386 Enabling this option adds the system calls process_vm_readv and 387 process_vm_writev which allow a process with the correct privileges 388 to directly read from or write to to another process's address space. 389 See the man page for more details. 390 391# 392# UP and nommu archs use km based percpu allocator 393# 394config NEED_PER_CPU_KM 395 depends on !SMP 396 bool 397 default y 398 399config CLEANCACHE 400 bool "Enable cleancache driver to cache clean pages if tmem is present" 401 default n 402 help 403 Cleancache can be thought of as a page-granularity victim cache 404 for clean pages that the kernel's pageframe replacement algorithm 405 (PFRA) would like to keep around, but can't since there isn't enough 406 memory. So when the PFRA "evicts" a page, it first attempts to use 407 cleancache code to put the data contained in that page into 408 "transcendent memory", memory that is not directly accessible or 409 addressable by the kernel and is of unknown and possibly 410 time-varying size. And when a cleancache-enabled 411 filesystem wishes to access a page in a file on disk, it first 412 checks cleancache to see if it already contains it; if it does, 413 the page is copied into the kernel and a disk access is avoided. 414 When a transcendent memory driver is available (such as zcache or 415 Xen transcendent memory), a significant I/O reduction 416 may be achieved. When none is available, all cleancache calls 417 are reduced to a single pointer-compare-against-NULL resulting 418 in a negligible performance hit. 419 420 If unsure, say Y to enable cleancache 421 422config FRONTSWAP 423 bool "Enable frontswap to cache swap pages if tmem is present" 424 depends on SWAP 425 default n 426 help 427 Frontswap is so named because it can be thought of as the opposite 428 of a "backing" store for a swap device. The data is stored into 429 "transcendent memory", memory that is not directly accessible or 430 addressable by the kernel and is of unknown and possibly 431 time-varying size. When space in transcendent memory is available, 432 a significant swap I/O reduction may be achieved. When none is 433 available, all frontswap calls are reduced to a single pointer- 434 compare-against-NULL resulting in a negligible performance hit 435 and swap data is stored as normal on the matching swap device. 436 437 If unsure, say Y to enable frontswap. 438