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 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 the following 157 two things: 158 - When the system is booting, node full of hotpluggable memory can 159 be arranged to have only movable memory so that the whole node can 160 be hot-removed. (need movable_node boot option specified). 161 - After the system is up, the option allows users to online all the 162 memory of a node as movable memory so that the whole node can be 163 hot-removed. 164 165 Users who don't use the memory hotplug feature are fine with this 166 option on since they don't specify movable_node boot option or they 167 don't online memory as movable. 168 169 Say Y here if you want to hotplug a whole node. 170 Say N here if you want kernel to use memory on all nodes evenly. 171 172# 173# Only be set on architectures that have completely implemented memory hotplug 174# feature. If you are not sure, don't touch it. 175# 176config HAVE_BOOTMEM_INFO_NODE 177 def_bool n 178 179# eventually, we can have this option just 'select SPARSEMEM' 180config MEMORY_HOTPLUG 181 bool "Allow for memory hot-add" 182 depends on SPARSEMEM || X86_64_ACPI_NUMA 183 depends on ARCH_ENABLE_MEMORY_HOTPLUG 184 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390) 185 186config MEMORY_HOTPLUG_SPARSE 187 def_bool y 188 depends on SPARSEMEM && MEMORY_HOTPLUG 189 190config MEMORY_HOTREMOVE 191 bool "Allow for memory hot remove" 192 select MEMORY_ISOLATION 193 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64) 194 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 195 depends on MIGRATION 196 197# 198# If we have space for more page flags then we can enable additional 199# optimizations and functionality. 200# 201# Regular Sparsemem takes page flag bits for the sectionid if it does not 202# use a virtual memmap. Disable extended page flags for 32 bit platforms 203# that require the use of a sectionid in the page flags. 204# 205config PAGEFLAGS_EXTENDED 206 def_bool y 207 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM 208 209# Heavily threaded applications may benefit from splitting the mm-wide 210# page_table_lock, so that faults on different parts of the user address 211# space can be handled with less contention: split it at this NR_CPUS. 212# Default to 4 for wider testing, though 8 might be more appropriate. 213# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 214# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 215# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 216# 217config SPLIT_PTLOCK_CPUS 218 int 219 default "999999" if !MMU 220 default "999999" if ARM && !CPU_CACHE_VIPT 221 default "999999" if PARISC && !PA20 222 default "4" 223 224config ARCH_ENABLE_SPLIT_PMD_PTLOCK 225 boolean 226 227# 228# support for memory balloon compaction 229config BALLOON_COMPACTION 230 bool "Allow for balloon memory compaction/migration" 231 def_bool y 232 depends on COMPACTION && VIRTIO_BALLOON 233 help 234 Memory fragmentation introduced by ballooning might reduce 235 significantly the number of 2MB contiguous memory blocks that can be 236 used within a guest, thus imposing performance penalties associated 237 with the reduced number of transparent huge pages that could be used 238 by the guest workload. Allowing the compaction & migration for memory 239 pages enlisted as being part of memory balloon devices avoids the 240 scenario aforementioned and helps improving memory defragmentation. 241 242# 243# support for memory compaction 244config COMPACTION 245 bool "Allow for memory compaction" 246 def_bool y 247 select MIGRATION 248 depends on MMU 249 help 250 Allows the compaction of memory for the allocation of huge pages. 251 252# 253# support for page migration 254# 255config MIGRATION 256 bool "Page migration" 257 def_bool y 258 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU 259 help 260 Allows the migration of the physical location of pages of processes 261 while the virtual addresses are not changed. This is useful in 262 two situations. The first is on NUMA systems to put pages nearer 263 to the processors accessing. The second is when allocating huge 264 pages as migration can relocate pages to satisfy a huge page 265 allocation instead of reclaiming. 266 267config PHYS_ADDR_T_64BIT 268 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 269 270config ZONE_DMA_FLAG 271 int 272 default "0" if !ZONE_DMA 273 default "1" 274 275config BOUNCE 276 bool "Enable bounce buffers" 277 default y 278 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 279 help 280 Enable bounce buffers for devices that cannot access 281 the full range of memory available to the CPU. Enabled 282 by default when ZONE_DMA or HIGHMEM is selected, but you 283 may say n to override this. 284 285# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often 286# have more than 4GB of memory, but we don't currently use the IOTLB to present 287# a 32-bit address to OHCI. So we need to use a bounce pool instead. 288# 289# We also use the bounce pool to provide stable page writes for jbd. jbd 290# initiates buffer writeback without locking the page or setting PG_writeback, 291# and fixing that behavior (a second time; jbd2 doesn't have this problem) is 292# a major rework effort. Instead, use the bounce buffer to snapshot pages 293# (until jbd goes away). The only jbd user is ext3. 294config NEED_BOUNCE_POOL 295 bool 296 default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD) 297 298config NR_QUICK 299 int 300 depends on QUICKLIST 301 default "2" if AVR32 302 default "1" 303 304config VIRT_TO_BUS 305 bool 306 help 307 An architecture should select this if it implements the 308 deprecated interface virt_to_bus(). All new architectures 309 should probably not select this. 310 311 312config MMU_NOTIFIER 313 bool 314 315config KSM 316 bool "Enable KSM for page merging" 317 depends on MMU 318 help 319 Enable Kernel Samepage Merging: KSM periodically scans those areas 320 of an application's address space that an app has advised may be 321 mergeable. When it finds pages of identical content, it replaces 322 the many instances by a single page with that content, so 323 saving memory until one or another app needs to modify the content. 324 Recommended for use with KVM, or with other duplicative applications. 325 See Documentation/vm/ksm.txt for more information: KSM is inactive 326 until a program has madvised that an area is MADV_MERGEABLE, and 327 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 328 329config DEFAULT_MMAP_MIN_ADDR 330 int "Low address space to protect from user allocation" 331 depends on MMU 332 default 4096 333 help 334 This is the portion of low virtual memory which should be protected 335 from userspace allocation. Keeping a user from writing to low pages 336 can help reduce the impact of kernel NULL pointer bugs. 337 338 For most ia64, ppc64 and x86 users with lots of address space 339 a value of 65536 is reasonable and should cause no problems. 340 On arm and other archs it should not be higher than 32768. 341 Programs which use vm86 functionality or have some need to map 342 this low address space will need CAP_SYS_RAWIO or disable this 343 protection by setting the value to 0. 344 345 This value can be changed after boot using the 346 /proc/sys/vm/mmap_min_addr tunable. 347 348config ARCH_SUPPORTS_MEMORY_FAILURE 349 bool 350 351config MEMORY_FAILURE 352 depends on MMU 353 depends on ARCH_SUPPORTS_MEMORY_FAILURE 354 bool "Enable recovery from hardware memory errors" 355 select MEMORY_ISOLATION 356 help 357 Enables code to recover from some memory failures on systems 358 with MCA recovery. This allows a system to continue running 359 even when some of its memory has uncorrected errors. This requires 360 special hardware support and typically ECC memory. 361 362config HWPOISON_INJECT 363 tristate "HWPoison pages injector" 364 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 365 select PROC_PAGE_MONITOR 366 367config NOMMU_INITIAL_TRIM_EXCESS 368 int "Turn on mmap() excess space trimming before booting" 369 depends on !MMU 370 default 1 371 help 372 The NOMMU mmap() frequently needs to allocate large contiguous chunks 373 of memory on which to store mappings, but it can only ask the system 374 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 375 more than it requires. To deal with this, mmap() is able to trim off 376 the excess and return it to the allocator. 377 378 If trimming is enabled, the excess is trimmed off and returned to the 379 system allocator, which can cause extra fragmentation, particularly 380 if there are a lot of transient processes. 381 382 If trimming is disabled, the excess is kept, but not used, which for 383 long-term mappings means that the space is wasted. 384 385 Trimming can be dynamically controlled through a sysctl option 386 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 387 excess pages there must be before trimming should occur, or zero if 388 no trimming is to occur. 389 390 This option specifies the initial value of this option. The default 391 of 1 says that all excess pages should be trimmed. 392 393 See Documentation/nommu-mmap.txt for more information. 394 395config TRANSPARENT_HUGEPAGE 396 bool "Transparent Hugepage Support" 397 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 398 select COMPACTION 399 help 400 Transparent Hugepages allows the kernel to use huge pages and 401 huge tlb transparently to the applications whenever possible. 402 This feature can improve computing performance to certain 403 applications by speeding up page faults during memory 404 allocation, by reducing the number of tlb misses and by speeding 405 up the pagetable walking. 406 407 If memory constrained on embedded, you may want to say N. 408 409choice 410 prompt "Transparent Hugepage Support sysfs defaults" 411 depends on TRANSPARENT_HUGEPAGE 412 default TRANSPARENT_HUGEPAGE_ALWAYS 413 help 414 Selects the sysfs defaults for Transparent Hugepage Support. 415 416 config TRANSPARENT_HUGEPAGE_ALWAYS 417 bool "always" 418 help 419 Enabling Transparent Hugepage always, can increase the 420 memory footprint of applications without a guaranteed 421 benefit but it will work automatically for all applications. 422 423 config TRANSPARENT_HUGEPAGE_MADVISE 424 bool "madvise" 425 help 426 Enabling Transparent Hugepage madvise, will only provide a 427 performance improvement benefit to the applications using 428 madvise(MADV_HUGEPAGE) but it won't risk to increase the 429 memory footprint of applications without a guaranteed 430 benefit. 431endchoice 432 433config CROSS_MEMORY_ATTACH 434 bool "Cross Memory Support" 435 depends on MMU 436 default y 437 help 438 Enabling this option adds the system calls process_vm_readv and 439 process_vm_writev which allow a process with the correct privileges 440 to directly read from or write to to another process's address space. 441 See the man page for more details. 442 443# 444# UP and nommu archs use km based percpu allocator 445# 446config NEED_PER_CPU_KM 447 depends on !SMP 448 bool 449 default y 450 451config CLEANCACHE 452 bool "Enable cleancache driver to cache clean pages if tmem is present" 453 default n 454 help 455 Cleancache can be thought of as a page-granularity victim cache 456 for clean pages that the kernel's pageframe replacement algorithm 457 (PFRA) would like to keep around, but can't since there isn't enough 458 memory. So when the PFRA "evicts" a page, it first attempts to use 459 cleancache code to put the data contained in that page into 460 "transcendent memory", memory that is not directly accessible or 461 addressable by the kernel and is of unknown and possibly 462 time-varying size. And when a cleancache-enabled 463 filesystem wishes to access a page in a file on disk, it first 464 checks cleancache to see if it already contains it; if it does, 465 the page is copied into the kernel and a disk access is avoided. 466 When a transcendent memory driver is available (such as zcache or 467 Xen transcendent memory), a significant I/O reduction 468 may be achieved. When none is available, all cleancache calls 469 are reduced to a single pointer-compare-against-NULL resulting 470 in a negligible performance hit. 471 472 If unsure, say Y to enable cleancache 473 474config FRONTSWAP 475 bool "Enable frontswap to cache swap pages if tmem is present" 476 depends on SWAP 477 default n 478 help 479 Frontswap is so named because it can be thought of as the opposite 480 of a "backing" store for a swap device. The data is stored into 481 "transcendent memory", memory that is not directly accessible or 482 addressable by the kernel and is of unknown and possibly 483 time-varying size. When space in transcendent memory is available, 484 a significant swap I/O reduction may be achieved. When none is 485 available, all frontswap calls are reduced to a single pointer- 486 compare-against-NULL resulting in a negligible performance hit 487 and swap data is stored as normal on the matching swap device. 488 489 If unsure, say Y to enable frontswap. 490 491config CMA 492 bool "Contiguous Memory Allocator" 493 depends on HAVE_MEMBLOCK && MMU 494 select MIGRATION 495 select MEMORY_ISOLATION 496 help 497 This enables the Contiguous Memory Allocator which allows other 498 subsystems to allocate big physically-contiguous blocks of memory. 499 CMA reserves a region of memory and allows only movable pages to 500 be allocated from it. This way, the kernel can use the memory for 501 pagecache and when a subsystem requests for contiguous area, the 502 allocated pages are migrated away to serve the contiguous request. 503 504 If unsure, say "n". 505 506config CMA_DEBUG 507 bool "CMA debug messages (DEVELOPMENT)" 508 depends on DEBUG_KERNEL && CMA 509 help 510 Turns on debug messages in CMA. This produces KERN_DEBUG 511 messages for every CMA call as well as various messages while 512 processing calls such as dma_alloc_from_contiguous(). 513 This option does not affect warning and error messages. 514 515config ZBUD 516 tristate 517 default n 518 help 519 A special purpose allocator for storing compressed pages. 520 It is designed to store up to two compressed pages per physical 521 page. While this design limits storage density, it has simple and 522 deterministic reclaim properties that make it preferable to a higher 523 density approach when reclaim will be used. 524 525config ZSWAP 526 bool "Compressed cache for swap pages (EXPERIMENTAL)" 527 depends on FRONTSWAP && CRYPTO=y 528 select CRYPTO_LZO 529 select ZBUD 530 default n 531 help 532 A lightweight compressed cache for swap pages. It takes 533 pages that are in the process of being swapped out and attempts to 534 compress them into a dynamically allocated RAM-based memory pool. 535 This can result in a significant I/O reduction on swap device and, 536 in the case where decompressing from RAM is faster that swap device 537 reads, can also improve workload performance. 538 539 This is marked experimental because it is a new feature (as of 540 v3.11) that interacts heavily with memory reclaim. While these 541 interactions don't cause any known issues on simple memory setups, 542 they have not be fully explored on the large set of potential 543 configurations and workloads that exist. 544 545config MEM_SOFT_DIRTY 546 bool "Track memory changes" 547 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 548 select PROC_PAGE_MONITOR 549 help 550 This option enables memory changes tracking by introducing a 551 soft-dirty bit on pte-s. This bit it set when someone writes 552 into a page just as regular dirty bit, but unlike the latter 553 it can be cleared by hands. 554 555 See Documentation/vm/soft-dirty.txt for more details. 556 557config ZSMALLOC 558 bool "Memory allocator for compressed pages" 559 depends on MMU 560 default n 561 help 562 zsmalloc is a slab-based memory allocator designed to store 563 compressed RAM pages. zsmalloc uses virtual memory mapping 564 in order to reduce fragmentation. However, this results in a 565 non-standard allocator interface where a handle, not a pointer, is 566 returned by an alloc(). This handle must be mapped in order to 567 access the allocated space. 568 569config PGTABLE_MAPPING 570 bool "Use page table mapping to access object in zsmalloc" 571 depends on ZSMALLOC 572 help 573 By default, zsmalloc uses a copy-based object mapping method to 574 access allocations that span two pages. However, if a particular 575 architecture (ex, ARM) performs VM mapping faster than copying, 576 then you should select this. This causes zsmalloc to use page table 577 mapping rather than copying for object mapping. 578 579 You can check speed with zsmalloc benchmark: 580 https://github.com/spartacus06/zsmapbench 581 582config GENERIC_EARLY_IOREMAP 583 bool 584 585config MAX_STACK_SIZE_MB 586 int "Maximum user stack size for 32-bit processes (MB)" 587 default 80 588 range 8 256 if METAG 589 range 8 2048 590 depends on STACK_GROWSUP && (!64BIT || COMPAT) 591 help 592 This is the maximum stack size in Megabytes in the VM layout of 32-bit 593 user processes when the stack grows upwards (currently only on parisc 594 and metag arch). The stack will be located at the highest memory 595 address minus the given value, unless the RLIMIT_STACK hard limit is 596 changed to a smaller value in which case that is used. 597 598 A sane initial value is 80 MB. 599