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 default n 153 help 154 Allow a node to have only movable memory. Pages used by the kernel, 155 such as direct mapping pages cannot be migrated. So the corresponding 156 memory device cannot be hotplugged. This option allows users to 157 online all the memory of a node as movable memory so that the whole 158 node can be hotplugged. Users who don't use the memory hotplug 159 feature are fine with this option on since they don't online memory 160 as movable. 161 162 Say Y here if you want to hotplug a whole node. 163 Say N here if you want kernel to use memory on all nodes evenly. 164 165# eventually, we can have this option just 'select SPARSEMEM' 166config MEMORY_HOTPLUG 167 bool "Allow for memory hot-add" 168 select MEMORY_ISOLATION 169 depends on SPARSEMEM || X86_64_ACPI_NUMA 170 depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG 171 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390) 172 173config MEMORY_HOTPLUG_SPARSE 174 def_bool y 175 depends on SPARSEMEM && MEMORY_HOTPLUG 176 177config MEMORY_HOTREMOVE 178 bool "Allow for memory hot remove" 179 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 180 depends on MIGRATION 181 182# 183# If we have space for more page flags then we can enable additional 184# optimizations and functionality. 185# 186# Regular Sparsemem takes page flag bits for the sectionid if it does not 187# use a virtual memmap. Disable extended page flags for 32 bit platforms 188# that require the use of a sectionid in the page flags. 189# 190config PAGEFLAGS_EXTENDED 191 def_bool y 192 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM 193 194# Heavily threaded applications may benefit from splitting the mm-wide 195# page_table_lock, so that faults on different parts of the user address 196# space can be handled with less contention: split it at this NR_CPUS. 197# Default to 4 for wider testing, though 8 might be more appropriate. 198# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 199# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 200# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 201# 202config SPLIT_PTLOCK_CPUS 203 int 204 default "999999" if ARM && !CPU_CACHE_VIPT 205 default "999999" if PARISC && !PA20 206 default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC 207 default "4" 208 209# 210# support for memory balloon compaction 211config BALLOON_COMPACTION 212 bool "Allow for balloon memory compaction/migration" 213 def_bool y 214 depends on COMPACTION && VIRTIO_BALLOON 215 help 216 Memory fragmentation introduced by ballooning might reduce 217 significantly the number of 2MB contiguous memory blocks that can be 218 used within a guest, thus imposing performance penalties associated 219 with the reduced number of transparent huge pages that could be used 220 by the guest workload. Allowing the compaction & migration for memory 221 pages enlisted as being part of memory balloon devices avoids the 222 scenario aforementioned and helps improving memory defragmentation. 223 224# 225# support for memory compaction 226config COMPACTION 227 bool "Allow for memory compaction" 228 def_bool y 229 select MIGRATION 230 depends on MMU 231 help 232 Allows the compaction of memory for the allocation of huge pages. 233 234# 235# support for page migration 236# 237config MIGRATION 238 bool "Page migration" 239 def_bool y 240 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA 241 help 242 Allows the migration of the physical location of pages of processes 243 while the virtual addresses are not changed. This is useful in 244 two situations. The first is on NUMA systems to put pages nearer 245 to the processors accessing. The second is when allocating huge 246 pages as migration can relocate pages to satisfy a huge page 247 allocation instead of reclaiming. 248 249config PHYS_ADDR_T_64BIT 250 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 251 252config ZONE_DMA_FLAG 253 int 254 default "0" if !ZONE_DMA 255 default "1" 256 257config BOUNCE 258 def_bool y 259 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 260 261config NR_QUICK 262 int 263 depends on QUICKLIST 264 default "2" if AVR32 265 default "1" 266 267config VIRT_TO_BUS 268 def_bool y 269 depends on !ARCH_NO_VIRT_TO_BUS 270 271config MMU_NOTIFIER 272 bool 273 274config KSM 275 bool "Enable KSM for page merging" 276 depends on MMU 277 help 278 Enable Kernel Samepage Merging: KSM periodically scans those areas 279 of an application's address space that an app has advised may be 280 mergeable. When it finds pages of identical content, it replaces 281 the many instances by a single page with that content, so 282 saving memory until one or another app needs to modify the content. 283 Recommended for use with KVM, or with other duplicative applications. 284 See Documentation/vm/ksm.txt for more information: KSM is inactive 285 until a program has madvised that an area is MADV_MERGEABLE, and 286 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 287 288config DEFAULT_MMAP_MIN_ADDR 289 int "Low address space to protect from user allocation" 290 depends on MMU 291 default 4096 292 help 293 This is the portion of low virtual memory which should be protected 294 from userspace allocation. Keeping a user from writing to low pages 295 can help reduce the impact of kernel NULL pointer bugs. 296 297 For most ia64, ppc64 and x86 users with lots of address space 298 a value of 65536 is reasonable and should cause no problems. 299 On arm and other archs it should not be higher than 32768. 300 Programs which use vm86 functionality or have some need to map 301 this low address space will need CAP_SYS_RAWIO or disable this 302 protection by setting the value to 0. 303 304 This value can be changed after boot using the 305 /proc/sys/vm/mmap_min_addr tunable. 306 307config ARCH_SUPPORTS_MEMORY_FAILURE 308 bool 309 310config MEMORY_FAILURE 311 depends on MMU 312 depends on ARCH_SUPPORTS_MEMORY_FAILURE 313 bool "Enable recovery from hardware memory errors" 314 select MEMORY_ISOLATION 315 help 316 Enables code to recover from some memory failures on systems 317 with MCA recovery. This allows a system to continue running 318 even when some of its memory has uncorrected errors. This requires 319 special hardware support and typically ECC memory. 320 321config HWPOISON_INJECT 322 tristate "HWPoison pages injector" 323 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 324 select PROC_PAGE_MONITOR 325 326config NOMMU_INITIAL_TRIM_EXCESS 327 int "Turn on mmap() excess space trimming before booting" 328 depends on !MMU 329 default 1 330 help 331 The NOMMU mmap() frequently needs to allocate large contiguous chunks 332 of memory on which to store mappings, but it can only ask the system 333 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 334 more than it requires. To deal with this, mmap() is able to trim off 335 the excess and return it to the allocator. 336 337 If trimming is enabled, the excess is trimmed off and returned to the 338 system allocator, which can cause extra fragmentation, particularly 339 if there are a lot of transient processes. 340 341 If trimming is disabled, the excess is kept, but not used, which for 342 long-term mappings means that the space is wasted. 343 344 Trimming can be dynamically controlled through a sysctl option 345 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 346 excess pages there must be before trimming should occur, or zero if 347 no trimming is to occur. 348 349 This option specifies the initial value of this option. The default 350 of 1 says that all excess pages should be trimmed. 351 352 See Documentation/nommu-mmap.txt for more information. 353 354config TRANSPARENT_HUGEPAGE 355 bool "Transparent Hugepage Support" 356 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 357 select COMPACTION 358 help 359 Transparent Hugepages allows the kernel to use huge pages and 360 huge tlb transparently to the applications whenever possible. 361 This feature can improve computing performance to certain 362 applications by speeding up page faults during memory 363 allocation, by reducing the number of tlb misses and by speeding 364 up the pagetable walking. 365 366 If memory constrained on embedded, you may want to say N. 367 368choice 369 prompt "Transparent Hugepage Support sysfs defaults" 370 depends on TRANSPARENT_HUGEPAGE 371 default TRANSPARENT_HUGEPAGE_ALWAYS 372 help 373 Selects the sysfs defaults for Transparent Hugepage Support. 374 375 config TRANSPARENT_HUGEPAGE_ALWAYS 376 bool "always" 377 help 378 Enabling Transparent Hugepage always, can increase the 379 memory footprint of applications without a guaranteed 380 benefit but it will work automatically for all applications. 381 382 config TRANSPARENT_HUGEPAGE_MADVISE 383 bool "madvise" 384 help 385 Enabling Transparent Hugepage madvise, will only provide a 386 performance improvement benefit to the applications using 387 madvise(MADV_HUGEPAGE) but it won't risk to increase the 388 memory footprint of applications without a guaranteed 389 benefit. 390endchoice 391 392config CROSS_MEMORY_ATTACH 393 bool "Cross Memory Support" 394 depends on MMU 395 default y 396 help 397 Enabling this option adds the system calls process_vm_readv and 398 process_vm_writev which allow a process with the correct privileges 399 to directly read from or write to to another process's address space. 400 See the man page for more details. 401 402# 403# UP and nommu archs use km based percpu allocator 404# 405config NEED_PER_CPU_KM 406 depends on !SMP 407 bool 408 default y 409 410config CLEANCACHE 411 bool "Enable cleancache driver to cache clean pages if tmem is present" 412 default n 413 help 414 Cleancache can be thought of as a page-granularity victim cache 415 for clean pages that the kernel's pageframe replacement algorithm 416 (PFRA) would like to keep around, but can't since there isn't enough 417 memory. So when the PFRA "evicts" a page, it first attempts to use 418 cleancache code to put the data contained in that page into 419 "transcendent memory", memory that is not directly accessible or 420 addressable by the kernel and is of unknown and possibly 421 time-varying size. And when a cleancache-enabled 422 filesystem wishes to access a page in a file on disk, it first 423 checks cleancache to see if it already contains it; if it does, 424 the page is copied into the kernel and a disk access is avoided. 425 When a transcendent memory driver is available (such as zcache or 426 Xen transcendent memory), a significant I/O reduction 427 may be achieved. When none is available, all cleancache calls 428 are reduced to a single pointer-compare-against-NULL resulting 429 in a negligible performance hit. 430 431 If unsure, say Y to enable cleancache 432 433config FRONTSWAP 434 bool "Enable frontswap to cache swap pages if tmem is present" 435 depends on SWAP 436 default n 437 help 438 Frontswap is so named because it can be thought of as the opposite 439 of a "backing" store for a swap device. The data is stored into 440 "transcendent memory", memory that is not directly accessible or 441 addressable by the kernel and is of unknown and possibly 442 time-varying size. When space in transcendent memory is available, 443 a significant swap I/O reduction may be achieved. When none is 444 available, all frontswap calls are reduced to a single pointer- 445 compare-against-NULL resulting in a negligible performance hit 446 and swap data is stored as normal on the matching swap device. 447 448 If unsure, say Y to enable frontswap. 449