1config SELECT_MEMORY_MODEL 2 def_bool y 3 depends on 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 a 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 HAVE_MEMBLOCK_PHYS_MAP 138 boolean 139 140config ARCH_DISCARD_MEMBLOCK 141 boolean 142 143config NO_BOOTMEM 144 boolean 145 146config MEMORY_ISOLATION 147 boolean 148 149config MOVABLE_NODE 150 boolean "Enable to assign a node which has only movable memory" 151 depends on HAVE_MEMBLOCK 152 depends on NO_BOOTMEM 153 depends on X86_64 154 depends on NUMA 155 default n 156 help 157 Allow a node to have only movable memory. Pages used by the kernel, 158 such as direct mapping pages cannot be migrated. So the corresponding 159 memory device cannot be hotplugged. This option allows the following 160 two things: 161 - When the system is booting, node full of hotpluggable memory can 162 be arranged to have only movable memory so that the whole node can 163 be hot-removed. (need movable_node boot option specified). 164 - After the system is up, the option allows users to online all the 165 memory of a node as movable memory so that the whole node can be 166 hot-removed. 167 168 Users who don't use the memory hotplug feature are fine with this 169 option on since they don't specify movable_node boot option or they 170 don't online memory as movable. 171 172 Say Y here if you want to hotplug a whole node. 173 Say N here if you want kernel to use memory on all nodes evenly. 174 175# 176# Only be set on architectures that have completely implemented memory hotplug 177# feature. If you are not sure, don't touch it. 178# 179config HAVE_BOOTMEM_INFO_NODE 180 def_bool n 181 182# eventually, we can have this option just 'select SPARSEMEM' 183config MEMORY_HOTPLUG 184 bool "Allow for memory hot-add" 185 depends on SPARSEMEM || X86_64_ACPI_NUMA 186 depends on ARCH_ENABLE_MEMORY_HOTPLUG 187 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390) 188 189config MEMORY_HOTPLUG_SPARSE 190 def_bool y 191 depends on SPARSEMEM && MEMORY_HOTPLUG 192 193config MEMORY_HOTREMOVE 194 bool "Allow for memory hot remove" 195 select MEMORY_ISOLATION 196 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64) 197 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 198 depends on MIGRATION 199 200# 201# If we have space for more page flags then we can enable additional 202# optimizations and functionality. 203# 204# Regular Sparsemem takes page flag bits for the sectionid if it does not 205# use a virtual memmap. Disable extended page flags for 32 bit platforms 206# that require the use of a sectionid in the page flags. 207# 208config PAGEFLAGS_EXTENDED 209 def_bool y 210 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM 211 212# Heavily threaded applications may benefit from splitting the mm-wide 213# page_table_lock, so that faults on different parts of the user address 214# space can be handled with less contention: split it at this NR_CPUS. 215# Default to 4 for wider testing, though 8 might be more appropriate. 216# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 217# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 218# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 219# 220config SPLIT_PTLOCK_CPUS 221 int 222 default "999999" if !MMU 223 default "999999" if ARM && !CPU_CACHE_VIPT 224 default "999999" if PARISC && !PA20 225 default "4" 226 227config ARCH_ENABLE_SPLIT_PMD_PTLOCK 228 boolean 229 230# 231# support for memory balloon compaction 232config BALLOON_COMPACTION 233 bool "Allow for balloon memory compaction/migration" 234 def_bool y 235 depends on COMPACTION && VIRTIO_BALLOON 236 help 237 Memory fragmentation introduced by ballooning might reduce 238 significantly the number of 2MB contiguous memory blocks that can be 239 used within a guest, thus imposing performance penalties associated 240 with the reduced number of transparent huge pages that could be used 241 by the guest workload. Allowing the compaction & migration for memory 242 pages enlisted as being part of memory balloon devices avoids the 243 scenario aforementioned and helps improving memory defragmentation. 244 245# 246# support for memory compaction 247config COMPACTION 248 bool "Allow for memory compaction" 249 def_bool y 250 select MIGRATION 251 depends on MMU 252 help 253 Allows the compaction of memory for the allocation of huge pages. 254 255# 256# support for page migration 257# 258config MIGRATION 259 bool "Page migration" 260 def_bool y 261 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU 262 help 263 Allows the migration of the physical location of pages of processes 264 while the virtual addresses are not changed. This is useful in 265 two situations. The first is on NUMA systems to put pages nearer 266 to the processors accessing. The second is when allocating huge 267 pages as migration can relocate pages to satisfy a huge page 268 allocation instead of reclaiming. 269 270config ARCH_ENABLE_HUGEPAGE_MIGRATION 271 boolean 272 273config PHYS_ADDR_T_64BIT 274 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 275 276config ZONE_DMA_FLAG 277 int 278 default "0" if !ZONE_DMA 279 default "1" 280 281config BOUNCE 282 bool "Enable bounce buffers" 283 default y 284 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 285 help 286 Enable bounce buffers for devices that cannot access 287 the full range of memory available to the CPU. Enabled 288 by default when ZONE_DMA or HIGHMEM is selected, but you 289 may say n to override this. 290 291# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often 292# have more than 4GB of memory, but we don't currently use the IOTLB to present 293# a 32-bit address to OHCI. So we need to use a bounce pool instead. 294# 295# We also use the bounce pool to provide stable page writes for jbd. jbd 296# initiates buffer writeback without locking the page or setting PG_writeback, 297# and fixing that behavior (a second time; jbd2 doesn't have this problem) is 298# a major rework effort. Instead, use the bounce buffer to snapshot pages 299# (until jbd goes away). The only jbd user is ext3. 300config NEED_BOUNCE_POOL 301 bool 302 default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD) 303 304config NR_QUICK 305 int 306 depends on QUICKLIST 307 default "2" if AVR32 308 default "1" 309 310config VIRT_TO_BUS 311 bool 312 help 313 An architecture should select this if it implements the 314 deprecated interface virt_to_bus(). All new architectures 315 should probably not select this. 316 317 318config MMU_NOTIFIER 319 bool 320 321config KSM 322 bool "Enable KSM for page merging" 323 depends on MMU 324 help 325 Enable Kernel Samepage Merging: KSM periodically scans those areas 326 of an application's address space that an app has advised may be 327 mergeable. When it finds pages of identical content, it replaces 328 the many instances by a single page with that content, so 329 saving memory until one or another app needs to modify the content. 330 Recommended for use with KVM, or with other duplicative applications. 331 See Documentation/vm/ksm.txt for more information: KSM is inactive 332 until a program has madvised that an area is MADV_MERGEABLE, and 333 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 334 335config DEFAULT_MMAP_MIN_ADDR 336 int "Low address space to protect from user allocation" 337 depends on MMU 338 default 4096 339 help 340 This is the portion of low virtual memory which should be protected 341 from userspace allocation. Keeping a user from writing to low pages 342 can help reduce the impact of kernel NULL pointer bugs. 343 344 For most ia64, ppc64 and x86 users with lots of address space 345 a value of 65536 is reasonable and should cause no problems. 346 On arm and other archs it should not be higher than 32768. 347 Programs which use vm86 functionality or have some need to map 348 this low address space will need CAP_SYS_RAWIO or disable this 349 protection by setting the value to 0. 350 351 This value can be changed after boot using the 352 /proc/sys/vm/mmap_min_addr tunable. 353 354config ARCH_SUPPORTS_MEMORY_FAILURE 355 bool 356 357config MEMORY_FAILURE 358 depends on MMU 359 depends on ARCH_SUPPORTS_MEMORY_FAILURE 360 bool "Enable recovery from hardware memory errors" 361 select MEMORY_ISOLATION 362 help 363 Enables code to recover from some memory failures on systems 364 with MCA recovery. This allows a system to continue running 365 even when some of its memory has uncorrected errors. This requires 366 special hardware support and typically ECC memory. 367 368config HWPOISON_INJECT 369 tristate "HWPoison pages injector" 370 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 371 select PROC_PAGE_MONITOR 372 373config NOMMU_INITIAL_TRIM_EXCESS 374 int "Turn on mmap() excess space trimming before booting" 375 depends on !MMU 376 default 1 377 help 378 The NOMMU mmap() frequently needs to allocate large contiguous chunks 379 of memory on which to store mappings, but it can only ask the system 380 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 381 more than it requires. To deal with this, mmap() is able to trim off 382 the excess and return it to the allocator. 383 384 If trimming is enabled, the excess is trimmed off and returned to the 385 system allocator, which can cause extra fragmentation, particularly 386 if there are a lot of transient processes. 387 388 If trimming is disabled, the excess is kept, but not used, which for 389 long-term mappings means that the space is wasted. 390 391 Trimming can be dynamically controlled through a sysctl option 392 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 393 excess pages there must be before trimming should occur, or zero if 394 no trimming is to occur. 395 396 This option specifies the initial value of this option. The default 397 of 1 says that all excess pages should be trimmed. 398 399 See Documentation/nommu-mmap.txt for more information. 400 401config TRANSPARENT_HUGEPAGE 402 bool "Transparent Hugepage Support" 403 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 404 select COMPACTION 405 help 406 Transparent Hugepages allows the kernel to use huge pages and 407 huge tlb transparently to the applications whenever possible. 408 This feature can improve computing performance to certain 409 applications by speeding up page faults during memory 410 allocation, by reducing the number of tlb misses and by speeding 411 up the pagetable walking. 412 413 If memory constrained on embedded, you may want to say N. 414 415choice 416 prompt "Transparent Hugepage Support sysfs defaults" 417 depends on TRANSPARENT_HUGEPAGE 418 default TRANSPARENT_HUGEPAGE_ALWAYS 419 help 420 Selects the sysfs defaults for Transparent Hugepage Support. 421 422 config TRANSPARENT_HUGEPAGE_ALWAYS 423 bool "always" 424 help 425 Enabling Transparent Hugepage always, can increase the 426 memory footprint of applications without a guaranteed 427 benefit but it will work automatically for all applications. 428 429 config TRANSPARENT_HUGEPAGE_MADVISE 430 bool "madvise" 431 help 432 Enabling Transparent Hugepage madvise, will only provide a 433 performance improvement benefit to the applications using 434 madvise(MADV_HUGEPAGE) but it won't risk to increase the 435 memory footprint of applications without a guaranteed 436 benefit. 437endchoice 438 439# 440# UP and nommu archs use km based percpu allocator 441# 442config NEED_PER_CPU_KM 443 depends on !SMP 444 bool 445 default y 446 447config CLEANCACHE 448 bool "Enable cleancache driver to cache clean pages if tmem is present" 449 default n 450 help 451 Cleancache can be thought of as a page-granularity victim cache 452 for clean pages that the kernel's pageframe replacement algorithm 453 (PFRA) would like to keep around, but can't since there isn't enough 454 memory. So when the PFRA "evicts" a page, it first attempts to use 455 cleancache code to put the data contained in that page into 456 "transcendent memory", memory that is not directly accessible or 457 addressable by the kernel and is of unknown and possibly 458 time-varying size. And when a cleancache-enabled 459 filesystem wishes to access a page in a file on disk, it first 460 checks cleancache to see if it already contains it; if it does, 461 the page is copied into the kernel and a disk access is avoided. 462 When a transcendent memory driver is available (such as zcache or 463 Xen transcendent memory), a significant I/O reduction 464 may be achieved. When none is available, all cleancache calls 465 are reduced to a single pointer-compare-against-NULL resulting 466 in a negligible performance hit. 467 468 If unsure, say Y to enable cleancache 469 470config FRONTSWAP 471 bool "Enable frontswap to cache swap pages if tmem is present" 472 depends on SWAP 473 default n 474 help 475 Frontswap is so named because it can be thought of as the opposite 476 of a "backing" store for a swap device. The data is stored into 477 "transcendent memory", memory that is not directly accessible or 478 addressable by the kernel and is of unknown and possibly 479 time-varying size. When space in transcendent memory is available, 480 a significant swap I/O reduction may be achieved. When none is 481 available, all frontswap calls are reduced to a single pointer- 482 compare-against-NULL resulting in a negligible performance hit 483 and swap data is stored as normal on the matching swap device. 484 485 If unsure, say Y to enable frontswap. 486 487config CMA 488 bool "Contiguous Memory Allocator" 489 depends on HAVE_MEMBLOCK && MMU 490 select MIGRATION 491 select MEMORY_ISOLATION 492 help 493 This enables the Contiguous Memory Allocator which allows other 494 subsystems to allocate big physically-contiguous blocks of memory. 495 CMA reserves a region of memory and allows only movable pages to 496 be allocated from it. This way, the kernel can use the memory for 497 pagecache and when a subsystem requests for contiguous area, the 498 allocated pages are migrated away to serve the contiguous request. 499 500 If unsure, say "n". 501 502config CMA_DEBUG 503 bool "CMA debug messages (DEVELOPMENT)" 504 depends on DEBUG_KERNEL && CMA 505 help 506 Turns on debug messages in CMA. This produces KERN_DEBUG 507 messages for every CMA call as well as various messages while 508 processing calls such as dma_alloc_from_contiguous(). 509 This option does not affect warning and error messages. 510 511config ZBUD 512 tristate 513 default n 514 help 515 A special purpose allocator for storing compressed pages. 516 It is designed to store up to two compressed pages per physical 517 page. While this design limits storage density, it has simple and 518 deterministic reclaim properties that make it preferable to a higher 519 density approach when reclaim will be used. 520 521config ZSWAP 522 bool "Compressed cache for swap pages (EXPERIMENTAL)" 523 depends on FRONTSWAP && CRYPTO=y 524 select CRYPTO_LZO 525 select ZBUD 526 default n 527 help 528 A lightweight compressed cache for swap pages. It takes 529 pages that are in the process of being swapped out and attempts to 530 compress them into a dynamically allocated RAM-based memory pool. 531 This can result in a significant I/O reduction on swap device and, 532 in the case where decompressing from RAM is faster that swap device 533 reads, can also improve workload performance. 534 535 This is marked experimental because it is a new feature (as of 536 v3.11) that interacts heavily with memory reclaim. While these 537 interactions don't cause any known issues on simple memory setups, 538 they have not be fully explored on the large set of potential 539 configurations and workloads that exist. 540 541config MEM_SOFT_DIRTY 542 bool "Track memory changes" 543 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 544 select PROC_PAGE_MONITOR 545 help 546 This option enables memory changes tracking by introducing a 547 soft-dirty bit on pte-s. This bit it set when someone writes 548 into a page just as regular dirty bit, but unlike the latter 549 it can be cleared by hands. 550 551 See Documentation/vm/soft-dirty.txt for more details. 552 553config ZSMALLOC 554 tristate "Memory allocator for compressed pages" 555 depends on MMU 556 default n 557 help 558 zsmalloc is a slab-based memory allocator designed to store 559 compressed RAM pages. zsmalloc uses virtual memory mapping 560 in order to reduce fragmentation. However, this results in a 561 non-standard allocator interface where a handle, not a pointer, is 562 returned by an alloc(). This handle must be mapped in order to 563 access the allocated space. 564 565config PGTABLE_MAPPING 566 bool "Use page table mapping to access object in zsmalloc" 567 depends on ZSMALLOC 568 help 569 By default, zsmalloc uses a copy-based object mapping method to 570 access allocations that span two pages. However, if a particular 571 architecture (ex, ARM) performs VM mapping faster than copying, 572 then you should select this. This causes zsmalloc to use page table 573 mapping rather than copying for object mapping. 574 575 You can check speed with zsmalloc benchmark: 576 https://github.com/spartacus06/zsmapbench 577 578config GENERIC_EARLY_IOREMAP 579 bool 580 581config MAX_STACK_SIZE_MB 582 int "Maximum user stack size for 32-bit processes (MB)" 583 default 80 584 range 8 256 if METAG 585 range 8 2048 586 depends on STACK_GROWSUP && (!64BIT || COMPAT) 587 help 588 This is the maximum stack size in Megabytes in the VM layout of 32-bit 589 user processes when the stack grows upwards (currently only on parisc 590 and metag arch). The stack will be located at the highest memory 591 address minus the given value, unless the RLIMIT_STACK hard limit is 592 changed to a smaller value in which case that is used. 593 594 A sane initial value is 80 MB. 595