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 bool 133 134config HAVE_MEMBLOCK_NODE_MAP 135 bool 136 137config HAVE_MEMBLOCK_PHYS_MAP 138 bool 139 140config HAVE_GENERIC_RCU_GUP 141 bool 142 143config ARCH_DISCARD_MEMBLOCK 144 bool 145 146config NO_BOOTMEM 147 bool 148 149config MEMORY_ISOLATION 150 bool 151 152config MOVABLE_NODE 153 bool "Enable to assign a node which has only movable memory" 154 depends on HAVE_MEMBLOCK 155 depends on NO_BOOTMEM 156 depends on X86_64 157 depends on NUMA 158 default n 159 help 160 Allow a node to have only movable memory. Pages used by the kernel, 161 such as direct mapping pages cannot be migrated. So the corresponding 162 memory device cannot be hotplugged. This option allows the following 163 two things: 164 - When the system is booting, node full of hotpluggable memory can 165 be arranged to have only movable memory so that the whole node can 166 be hot-removed. (need movable_node boot option specified). 167 - After the system is up, the option allows users to online all the 168 memory of a node as movable memory so that the whole node can be 169 hot-removed. 170 171 Users who don't use the memory hotplug feature are fine with this 172 option on since they don't specify movable_node boot option or they 173 don't online memory as movable. 174 175 Say Y here if you want to hotplug a whole node. 176 Say N here if you want kernel to use memory on all nodes evenly. 177 178# 179# Only be set on architectures that have completely implemented memory hotplug 180# feature. If you are not sure, don't touch it. 181# 182config HAVE_BOOTMEM_INFO_NODE 183 def_bool n 184 185# eventually, we can have this option just 'select SPARSEMEM' 186config MEMORY_HOTPLUG 187 bool "Allow for memory hot-add" 188 depends on SPARSEMEM || X86_64_ACPI_NUMA 189 depends on ARCH_ENABLE_MEMORY_HOTPLUG 190 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390) 191 192config MEMORY_HOTPLUG_SPARSE 193 def_bool y 194 depends on SPARSEMEM && MEMORY_HOTPLUG 195 196config MEMORY_HOTREMOVE 197 bool "Allow for memory hot remove" 198 select MEMORY_ISOLATION 199 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64) 200 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 201 depends on MIGRATION 202 203# 204# If we have space for more page flags then we can enable additional 205# optimizations and functionality. 206# 207# Regular Sparsemem takes page flag bits for the sectionid if it does not 208# use a virtual memmap. Disable extended page flags for 32 bit platforms 209# that require the use of a sectionid in the page flags. 210# 211config PAGEFLAGS_EXTENDED 212 def_bool y 213 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM 214 215# Heavily threaded applications may benefit from splitting the mm-wide 216# page_table_lock, so that faults on different parts of the user address 217# space can be handled with less contention: split it at this NR_CPUS. 218# Default to 4 for wider testing, though 8 might be more appropriate. 219# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 220# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 221# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 222# 223config SPLIT_PTLOCK_CPUS 224 int 225 default "999999" if !MMU 226 default "999999" if ARM && !CPU_CACHE_VIPT 227 default "999999" if PARISC && !PA20 228 default "4" 229 230config ARCH_ENABLE_SPLIT_PMD_PTLOCK 231 bool 232 233# 234# support for memory balloon 235config MEMORY_BALLOON 236 bool 237 238# 239# support for memory balloon compaction 240config BALLOON_COMPACTION 241 bool "Allow for balloon memory compaction/migration" 242 def_bool y 243 depends on COMPACTION && MEMORY_BALLOON 244 help 245 Memory fragmentation introduced by ballooning might reduce 246 significantly the number of 2MB contiguous memory blocks that can be 247 used within a guest, thus imposing performance penalties associated 248 with the reduced number of transparent huge pages that could be used 249 by the guest workload. Allowing the compaction & migration for memory 250 pages enlisted as being part of memory balloon devices avoids the 251 scenario aforementioned and helps improving memory defragmentation. 252 253# 254# support for memory compaction 255config COMPACTION 256 bool "Allow for memory compaction" 257 def_bool y 258 select MIGRATION 259 depends on MMU 260 help 261 Allows the compaction of memory for the allocation of huge pages. 262 263# 264# support for page migration 265# 266config MIGRATION 267 bool "Page migration" 268 def_bool y 269 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU 270 help 271 Allows the migration of the physical location of pages of processes 272 while the virtual addresses are not changed. This is useful in 273 two situations. The first is on NUMA systems to put pages nearer 274 to the processors accessing. The second is when allocating huge 275 pages as migration can relocate pages to satisfy a huge page 276 allocation instead of reclaiming. 277 278config ARCH_ENABLE_HUGEPAGE_MIGRATION 279 bool 280 281config PHYS_ADDR_T_64BIT 282 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 283 284config ZONE_DMA_FLAG 285 int 286 default "0" if !ZONE_DMA 287 default "1" 288 289config BOUNCE 290 bool "Enable bounce buffers" 291 default y 292 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 293 help 294 Enable bounce buffers for devices that cannot access 295 the full range of memory available to the CPU. Enabled 296 by default when ZONE_DMA or HIGHMEM is selected, but you 297 may say n to override this. 298 299# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often 300# have more than 4GB of memory, but we don't currently use the IOTLB to present 301# a 32-bit address to OHCI. So we need to use a bounce pool instead. 302# 303# We also use the bounce pool to provide stable page writes for jbd. jbd 304# initiates buffer writeback without locking the page or setting PG_writeback, 305# and fixing that behavior (a second time; jbd2 doesn't have this problem) is 306# a major rework effort. Instead, use the bounce buffer to snapshot pages 307# (until jbd goes away). The only jbd user is ext3. 308config NEED_BOUNCE_POOL 309 bool 310 default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD) 311 312config NR_QUICK 313 int 314 depends on QUICKLIST 315 default "2" if AVR32 316 default "1" 317 318config VIRT_TO_BUS 319 bool 320 help 321 An architecture should select this if it implements the 322 deprecated interface virt_to_bus(). All new architectures 323 should probably not select this. 324 325 326config MMU_NOTIFIER 327 bool 328 select SRCU 329 330config KSM 331 bool "Enable KSM for page merging" 332 depends on MMU 333 help 334 Enable Kernel Samepage Merging: KSM periodically scans those areas 335 of an application's address space that an app has advised may be 336 mergeable. When it finds pages of identical content, it replaces 337 the many instances by a single page with that content, so 338 saving memory until one or another app needs to modify the content. 339 Recommended for use with KVM, or with other duplicative applications. 340 See Documentation/vm/ksm.txt for more information: KSM is inactive 341 until a program has madvised that an area is MADV_MERGEABLE, and 342 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 343 344config DEFAULT_MMAP_MIN_ADDR 345 int "Low address space to protect from user allocation" 346 depends on MMU 347 default 4096 348 help 349 This is the portion of low virtual memory which should be protected 350 from userspace allocation. Keeping a user from writing to low pages 351 can help reduce the impact of kernel NULL pointer bugs. 352 353 For most ia64, ppc64 and x86 users with lots of address space 354 a value of 65536 is reasonable and should cause no problems. 355 On arm and other archs it should not be higher than 32768. 356 Programs which use vm86 functionality or have some need to map 357 this low address space will need CAP_SYS_RAWIO or disable this 358 protection by setting the value to 0. 359 360 This value can be changed after boot using the 361 /proc/sys/vm/mmap_min_addr tunable. 362 363config ARCH_SUPPORTS_MEMORY_FAILURE 364 bool 365 366config MEMORY_FAILURE 367 depends on MMU 368 depends on ARCH_SUPPORTS_MEMORY_FAILURE 369 bool "Enable recovery from hardware memory errors" 370 select MEMORY_ISOLATION 371 help 372 Enables code to recover from some memory failures on systems 373 with MCA recovery. This allows a system to continue running 374 even when some of its memory has uncorrected errors. This requires 375 special hardware support and typically ECC memory. 376 377config HWPOISON_INJECT 378 tristate "HWPoison pages injector" 379 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 380 select PROC_PAGE_MONITOR 381 382config NOMMU_INITIAL_TRIM_EXCESS 383 int "Turn on mmap() excess space trimming before booting" 384 depends on !MMU 385 default 1 386 help 387 The NOMMU mmap() frequently needs to allocate large contiguous chunks 388 of memory on which to store mappings, but it can only ask the system 389 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 390 more than it requires. To deal with this, mmap() is able to trim off 391 the excess and return it to the allocator. 392 393 If trimming is enabled, the excess is trimmed off and returned to the 394 system allocator, which can cause extra fragmentation, particularly 395 if there are a lot of transient processes. 396 397 If trimming is disabled, the excess is kept, but not used, which for 398 long-term mappings means that the space is wasted. 399 400 Trimming can be dynamically controlled through a sysctl option 401 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 402 excess pages there must be before trimming should occur, or zero if 403 no trimming is to occur. 404 405 This option specifies the initial value of this option. The default 406 of 1 says that all excess pages should be trimmed. 407 408 See Documentation/nommu-mmap.txt for more information. 409 410config TRANSPARENT_HUGEPAGE 411 bool "Transparent Hugepage Support" 412 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 413 select COMPACTION 414 help 415 Transparent Hugepages allows the kernel to use huge pages and 416 huge tlb transparently to the applications whenever possible. 417 This feature can improve computing performance to certain 418 applications by speeding up page faults during memory 419 allocation, by reducing the number of tlb misses and by speeding 420 up the pagetable walking. 421 422 If memory constrained on embedded, you may want to say N. 423 424choice 425 prompt "Transparent Hugepage Support sysfs defaults" 426 depends on TRANSPARENT_HUGEPAGE 427 default TRANSPARENT_HUGEPAGE_ALWAYS 428 help 429 Selects the sysfs defaults for Transparent Hugepage Support. 430 431 config TRANSPARENT_HUGEPAGE_ALWAYS 432 bool "always" 433 help 434 Enabling Transparent Hugepage always, can increase the 435 memory footprint of applications without a guaranteed 436 benefit but it will work automatically for all applications. 437 438 config TRANSPARENT_HUGEPAGE_MADVISE 439 bool "madvise" 440 help 441 Enabling Transparent Hugepage madvise, will only provide a 442 performance improvement benefit to the applications using 443 madvise(MADV_HUGEPAGE) but it won't risk to increase the 444 memory footprint of applications without a guaranteed 445 benefit. 446endchoice 447 448# 449# UP and nommu archs use km based percpu allocator 450# 451config NEED_PER_CPU_KM 452 depends on !SMP 453 bool 454 default y 455 456config CLEANCACHE 457 bool "Enable cleancache driver to cache clean pages if tmem is present" 458 default n 459 help 460 Cleancache can be thought of as a page-granularity victim cache 461 for clean pages that the kernel's pageframe replacement algorithm 462 (PFRA) would like to keep around, but can't since there isn't enough 463 memory. So when the PFRA "evicts" a page, it first attempts to use 464 cleancache code to put the data contained in that page into 465 "transcendent memory", memory that is not directly accessible or 466 addressable by the kernel and is of unknown and possibly 467 time-varying size. And when a cleancache-enabled 468 filesystem wishes to access a page in a file on disk, it first 469 checks cleancache to see if it already contains it; if it does, 470 the page is copied into the kernel and a disk access is avoided. 471 When a transcendent memory driver is available (such as zcache or 472 Xen transcendent memory), a significant I/O reduction 473 may be achieved. When none is available, all cleancache calls 474 are reduced to a single pointer-compare-against-NULL resulting 475 in a negligible performance hit. 476 477 If unsure, say Y to enable cleancache 478 479config FRONTSWAP 480 bool "Enable frontswap to cache swap pages if tmem is present" 481 depends on SWAP 482 default n 483 help 484 Frontswap is so named because it can be thought of as the opposite 485 of a "backing" store for a swap device. The data is stored into 486 "transcendent memory", memory that is not directly accessible or 487 addressable by the kernel and is of unknown and possibly 488 time-varying size. When space in transcendent memory is available, 489 a significant swap I/O reduction may be achieved. When none is 490 available, all frontswap calls are reduced to a single pointer- 491 compare-against-NULL resulting in a negligible performance hit 492 and swap data is stored as normal on the matching swap device. 493 494 If unsure, say Y to enable frontswap. 495 496config CMA 497 bool "Contiguous Memory Allocator" 498 depends on HAVE_MEMBLOCK && MMU 499 select MIGRATION 500 select MEMORY_ISOLATION 501 help 502 This enables the Contiguous Memory Allocator which allows other 503 subsystems to allocate big physically-contiguous blocks of memory. 504 CMA reserves a region of memory and allows only movable pages to 505 be allocated from it. This way, the kernel can use the memory for 506 pagecache and when a subsystem requests for contiguous area, the 507 allocated pages are migrated away to serve the contiguous request. 508 509 If unsure, say "n". 510 511config CMA_DEBUG 512 bool "CMA debug messages (DEVELOPMENT)" 513 depends on DEBUG_KERNEL && CMA 514 help 515 Turns on debug messages in CMA. This produces KERN_DEBUG 516 messages for every CMA call as well as various messages while 517 processing calls such as dma_alloc_from_contiguous(). 518 This option does not affect warning and error messages. 519 520config CMA_DEBUGFS 521 bool "CMA debugfs interface" 522 depends on CMA && DEBUG_FS 523 help 524 Turns on the DebugFS interface for CMA. 525 526config CMA_AREAS 527 int "Maximum count of the CMA areas" 528 depends on CMA 529 default 7 530 help 531 CMA allows to create CMA areas for particular purpose, mainly, 532 used as device private area. This parameter sets the maximum 533 number of CMA area in the system. 534 535 If unsure, leave the default value "7". 536 537config MEM_SOFT_DIRTY 538 bool "Track memory changes" 539 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 540 select PROC_PAGE_MONITOR 541 help 542 This option enables memory changes tracking by introducing a 543 soft-dirty bit on pte-s. This bit it set when someone writes 544 into a page just as regular dirty bit, but unlike the latter 545 it can be cleared by hands. 546 547 See Documentation/vm/soft-dirty.txt for more details. 548 549config ZSWAP 550 bool "Compressed cache for swap pages (EXPERIMENTAL)" 551 depends on FRONTSWAP && CRYPTO=y 552 select CRYPTO_LZO 553 select ZPOOL 554 default n 555 help 556 A lightweight compressed cache for swap pages. It takes 557 pages that are in the process of being swapped out and attempts to 558 compress them into a dynamically allocated RAM-based memory pool. 559 This can result in a significant I/O reduction on swap device and, 560 in the case where decompressing from RAM is faster that swap device 561 reads, can also improve workload performance. 562 563 This is marked experimental because it is a new feature (as of 564 v3.11) that interacts heavily with memory reclaim. While these 565 interactions don't cause any known issues on simple memory setups, 566 they have not be fully explored on the large set of potential 567 configurations and workloads that exist. 568 569config ZPOOL 570 tristate "Common API for compressed memory storage" 571 default n 572 help 573 Compressed memory storage API. This allows using either zbud or 574 zsmalloc. 575 576config ZBUD 577 tristate "Low density storage for compressed pages" 578 default n 579 help 580 A special purpose allocator for storing compressed pages. 581 It is designed to store up to two compressed pages per physical 582 page. While this design limits storage density, it has simple and 583 deterministic reclaim properties that make it preferable to a higher 584 density approach when reclaim will be used. 585 586config ZSMALLOC 587 tristate "Memory allocator for compressed pages" 588 depends on MMU 589 default n 590 help 591 zsmalloc is a slab-based memory allocator designed to store 592 compressed RAM pages. zsmalloc uses virtual memory mapping 593 in order to reduce fragmentation. However, this results in a 594 non-standard allocator interface where a handle, not a pointer, is 595 returned by an alloc(). This handle must be mapped in order to 596 access the allocated space. 597 598config PGTABLE_MAPPING 599 bool "Use page table mapping to access object in zsmalloc" 600 depends on ZSMALLOC 601 help 602 By default, zsmalloc uses a copy-based object mapping method to 603 access allocations that span two pages. However, if a particular 604 architecture (ex, ARM) performs VM mapping faster than copying, 605 then you should select this. This causes zsmalloc to use page table 606 mapping rather than copying for object mapping. 607 608 You can check speed with zsmalloc benchmark: 609 https://github.com/spartacus06/zsmapbench 610 611config ZSMALLOC_STAT 612 bool "Export zsmalloc statistics" 613 depends on ZSMALLOC 614 select DEBUG_FS 615 help 616 This option enables code in the zsmalloc to collect various 617 statistics about whats happening in zsmalloc and exports that 618 information to userspace via debugfs. 619 If unsure, say N. 620 621config GENERIC_EARLY_IOREMAP 622 bool 623 624config MAX_STACK_SIZE_MB 625 int "Maximum user stack size for 32-bit processes (MB)" 626 default 80 627 range 8 256 if METAG 628 range 8 2048 629 depends on STACK_GROWSUP && (!64BIT || COMPAT) 630 help 631 This is the maximum stack size in Megabytes in the VM layout of 32-bit 632 user processes when the stack grows upwards (currently only on parisc 633 and metag arch). The stack will be located at the highest memory 634 address minus the given value, unless the RLIMIT_STACK hard limit is 635 changed to a smaller value in which case that is used. 636 637 A sane initial value is 80 MB. 638