mm/Kconfig

   1 # SPDX-License-Identifier: GPL-2.0-only
   2
   3 menu "Memory Management options"
   4
   5 config SELECT_MEMORY_MODEL
   6         def_bool y
   7         depends on ARCH_SELECT_MEMORY_MODEL
   8
   9 choice
  10         prompt "Memory model"
  11         depends on SELECT_MEMORY_MODEL
  12         default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
  13         default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
  14         default FLATMEM_MANUAL
  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 selected by the architecture
  19           configuration. This is normal.
  20
  21 config FLATMEM_MANUAL
  22         bool "Flat Memory"
  23         depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
  24         help
  25           This option is best suited for non-NUMA systems with
  26           flat address space. The FLATMEM is the most efficient
  27           system in terms of performance and resource consumption
  28           and it is the best option for smaller systems.
  29
  30           For systems that have holes in their physical address
  31           spaces and for features like NUMA and memory hotplug,
  32           choose "Sparse Memory"
  33
  34           If unsure, choose this option (Flat Memory) over any other.
  35
  36 config DISCONTIGMEM_MANUAL
  37         bool "Discontiguous Memory"
  38         depends on ARCH_DISCONTIGMEM_ENABLE
  39         help
  40           This option provides enhanced support for discontiguous
  41           memory systems, over FLATMEM.  These systems have holes
  42           in their physical address spaces, and this option provides
  43           more efficient handling of these holes.
  44
  45           Although "Discontiguous Memory" is still used by several
  46           architectures, it is considered deprecated in favor of
  47           "Sparse Memory".
  48
  49           If unsure, choose "Sparse Memory" over this option.
  50
  51 config SPARSEMEM_MANUAL
  52         bool "Sparse Memory"
  53         depends on ARCH_SPARSEMEM_ENABLE
  54         help
  55           This will be the only option for some systems, including
  56           memory hot-plug systems.  This is normal.
  57
  58           This option provides efficient support for systems with
  59           holes is their physical address space and allows memory
  60           hot-plug and hot-remove.
  61
  62           If unsure, choose "Flat Memory" over this option.
  63
  64 endchoice
  65
  66 config DISCONTIGMEM
  67         def_bool y
  68         depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
  69
  70 config SPARSEMEM
  71         def_bool y
  72         depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
  73
  74 config FLATMEM
  75         def_bool y
  76         depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
  77
  78 config FLAT_NODE_MEM_MAP
  79         def_bool y
  80         depends on !SPARSEMEM
  81
  82 #
  83 # Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
  84 # to represent different areas of memory.  This variable allows
  85 # those dependencies to exist individually.
  86 #
  87 config NEED_MULTIPLE_NODES
  88         def_bool y
  89         depends on DISCONTIGMEM || NUMA
  90
  91 config HAVE_MEMORY_PRESENT
  92         def_bool y
  93         depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
  94
  95 #
  96 # SPARSEMEM_EXTREME (which is the default) does some bootmem
  97 # allocations when memory_present() is called.  If this cannot
  98 # be done on your architecture, select this option.  However,
  99 # statically allocating the mem_section[] array can potentially
 100 # consume vast quantities of .bss, so be careful.
 101 #
 102 # This option will also potentially produce smaller runtime code
 103 # with gcc 3.4 and later.
 104 #
 105 config SPARSEMEM_STATIC
 106         bool
 107
 108 #
 109 # Architecture platforms which require a two level mem_section in SPARSEMEM
 110 # must select this option. This is usually for architecture platforms with
 111 # an extremely sparse physical address space.
 112 #
 113 config SPARSEMEM_EXTREME
 114         def_bool y
 115         depends on SPARSEMEM && !SPARSEMEM_STATIC
 116
 117 config SPARSEMEM_VMEMMAP_ENABLE
 118         bool
 119
 120 config SPARSEMEM_VMEMMAP
 121         bool "Sparse Memory virtual memmap"
 122         depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
 123         default y
 124         help
 125          SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
 126          pfn_to_page and page_to_pfn operations.  This is the most
 127          efficient option when sufficient kernel resources are available.
 128
 129 config HAVE_MEMBLOCK_NODE_MAP
 130         bool
 131
 132 config HAVE_MEMBLOCK_PHYS_MAP
 133         bool
 134
 135 config HAVE_GENERIC_GUP
 136         bool
 137
 138 config ARCH_KEEP_MEMBLOCK
 139         bool
 140
 141 config MEMORY_ISOLATION
 142         bool
 143
 144 #
 145 # Only be set on architectures that have completely implemented memory hotplug
 146 # feature. If you are not sure, don't touch it.
 147 #
 148 config HAVE_BOOTMEM_INFO_NODE
 149         def_bool n
 150
 151 # eventually, we can have this option just 'select SPARSEMEM'
 152 config MEMORY_HOTPLUG
 153         bool "Allow for memory hot-add"
 154         depends on SPARSEMEM || X86_64_ACPI_NUMA
 155         depends on ARCH_ENABLE_MEMORY_HOTPLUG
 156
 157 config MEMORY_HOTPLUG_SPARSE
 158         def_bool y
 159         depends on SPARSEMEM && MEMORY_HOTPLUG
 160
 161 config MEMORY_HOTPLUG_DEFAULT_ONLINE
 162         bool "Online the newly added memory blocks by default"
 163         depends on MEMORY_HOTPLUG
 164         help
 165           This option sets the default policy setting for memory hotplug
 166           onlining policy (/sys/devices/system/memory/auto_online_blocks) which
 167           determines what happens to newly added memory regions. Policy setting
 168           can always be changed at runtime.
 169           See Documentation/memory-hotplug.txt for more information.
 170
 171           Say Y here if you want all hot-plugged memory blocks to appear in
 172           'online' state by default.
 173           Say N here if you want the default policy to keep all hot-plugged
 174           memory blocks in 'offline' state.
 175
 176 config MEMORY_HOTREMOVE
 177         bool "Allow for memory hot remove"
 178         select MEMORY_ISOLATION
 179         select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
 180         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 181         depends on MIGRATION
 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 #
 191 config SPLIT_PTLOCK_CPUS
 192         int
 193         default "999999" if !MMU
 194         default "999999" if ARM && !CPU_CACHE_VIPT
 195         default "999999" if PARISC && !PA20
 196         default "4"
 197
 198 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
 199         bool
 200
 201 #
 202 # support for memory balloon
 203 config MEMORY_BALLOON
 204         bool
 205
 206 #
 207 # support for memory balloon compaction
 208 config BALLOON_COMPACTION
 209         bool "Allow for balloon memory compaction/migration"
 210         def_bool y
 211         depends on COMPACTION && MEMORY_BALLOON
 212         help
 213           Memory fragmentation introduced by ballooning might reduce
 214           significantly the number of 2MB contiguous memory blocks that can be
 215           used within a guest, thus imposing performance penalties associated
 216           with the reduced number of transparent huge pages that could be used
 217           by the guest workload. Allowing the compaction & migration for memory
 218           pages enlisted as being part of memory balloon devices avoids the
 219           scenario aforementioned and helps improving memory defragmentation.
 220
 221 #
 222 # support for memory compaction
 223 config COMPACTION
 224         bool "Allow for memory compaction"
 225         def_bool y
 226         select MIGRATION
 227         depends on MMU
 228         help
 229           Compaction is the only memory management component to form
 230           high order (larger physically contiguous) memory blocks
 231           reliably. The page allocator relies on compaction heavily and
 232           the lack of the feature can lead to unexpected OOM killer
 233           invocations for high order memory requests. You shouldn't
 234           disable this option unless there really is a strong reason for
 235           it and then we would be really interested to hear about that at
 236           linux-mm@kvack.org.
 237
 238 #
 239 # support for page migration
 240 #
 241 config MIGRATION
 242         bool "Page migration"
 243         def_bool y
 244         depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
 245         help
 246           Allows the migration of the physical location of pages of processes
 247           while the virtual addresses are not changed. This is useful in
 248           two situations. The first is on NUMA systems to put pages nearer
 249           to the processors accessing. The second is when allocating huge
 250           pages as migration can relocate pages to satisfy a huge page
 251           allocation instead of reclaiming.
 252
 253 config ARCH_ENABLE_HUGEPAGE_MIGRATION
 254         bool
 255
 256 config ARCH_ENABLE_THP_MIGRATION
 257         bool
 258
 259 config CONTIG_ALLOC
 260        def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
 261
 262 config PHYS_ADDR_T_64BIT
 263         def_bool 64BIT
 264
 265 config BOUNCE
 266         bool "Enable bounce buffers"
 267         default y
 268         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 269         help
 270           Enable bounce buffers for devices that cannot access
 271           the full range of memory available to the CPU. Enabled
 272           by default when ZONE_DMA or HIGHMEM is selected, but you
 273           may say n to override this.
 274
 275 config NR_QUICK
 276         int
 277         depends on QUICKLIST
 278         default "1"
 279
 280 config VIRT_TO_BUS
 281         bool
 282         help
 283           An architecture should select this if it implements the
 284           deprecated interface virt_to_bus().  All new architectures
 285           should probably not select this.
 286
 287
 288 config MMU_NOTIFIER
 289         bool
 290         select SRCU
 291
 292 config KSM
 293         bool "Enable KSM for page merging"
 294         depends on MMU
 295         select XXHASH
 296         help
 297           Enable Kernel Samepage Merging: KSM periodically scans those areas
 298           of an application's address space that an app has advised may be
 299           mergeable.  When it finds pages of identical content, it replaces
 300           the many instances by a single page with that content, so
 301           saving memory until one or another app needs to modify the content.
 302           Recommended for use with KVM, or with other duplicative applications.
 303           See Documentation/vm/ksm.rst for more information: KSM is inactive
 304           until a program has madvised that an area is MADV_MERGEABLE, and
 305           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 306
 307 config DEFAULT_MMAP_MIN_ADDR
 308         int "Low address space to protect from user allocation"
 309         depends on MMU
 310         default 4096
 311         help
 312           This is the portion of low virtual memory which should be protected
 313           from userspace allocation.  Keeping a user from writing to low pages
 314           can help reduce the impact of kernel NULL pointer bugs.
 315
 316           For most ia64, ppc64 and x86 users with lots of address space
 317           a value of 65536 is reasonable and should cause no problems.
 318           On arm and other archs it should not be higher than 32768.
 319           Programs which use vm86 functionality or have some need to map
 320           this low address space will need CAP_SYS_RAWIO or disable this
 321           protection by setting the value to 0.
 322
 323           This value can be changed after boot using the
 324           /proc/sys/vm/mmap_min_addr tunable.
 325
 326 config ARCH_SUPPORTS_MEMORY_FAILURE
 327         bool
 328
 329 config MEMORY_FAILURE
 330         depends on MMU
 331         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 332         bool "Enable recovery from hardware memory errors"
 333         select MEMORY_ISOLATION
 334         select RAS
 335         help
 336           Enables code to recover from some memory failures on systems
 337           with MCA recovery. This allows a system to continue running
 338           even when some of its memory has uncorrected errors. This requires
 339           special hardware support and typically ECC memory.
 340
 341 config HWPOISON_INJECT
 342         tristate "HWPoison pages injector"
 343         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 344         select PROC_PAGE_MONITOR
 345
 346 config NOMMU_INITIAL_TRIM_EXCESS
 347         int "Turn on mmap() excess space trimming before booting"
 348         depends on !MMU
 349         default 1
 350         help
 351           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 352           of memory on which to store mappings, but it can only ask the system
 353           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 354           more than it requires.  To deal with this, mmap() is able to trim off
 355           the excess and return it to the allocator.
 356
 357           If trimming is enabled, the excess is trimmed off and returned to the
 358           system allocator, which can cause extra fragmentation, particularly
 359           if there are a lot of transient processes.
 360
 361           If trimming is disabled, the excess is kept, but not used, which for
 362           long-term mappings means that the space is wasted.
 363
 364           Trimming can be dynamically controlled through a sysctl option
 365           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 366           excess pages there must be before trimming should occur, or zero if
 367           no trimming is to occur.
 368
 369           This option specifies the initial value of this option.  The default
 370           of 1 says that all excess pages should be trimmed.
 371
 372           See Documentation/nommu-mmap.txt for more information.
 373
 374 config TRANSPARENT_HUGEPAGE
 375         bool "Transparent Hugepage Support"
 376         depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
 377         select COMPACTION
 378         select XARRAY_MULTI
 379         help
 380           Transparent Hugepages allows the kernel to use huge pages and
 381           huge tlb transparently to the applications whenever possible.
 382           This feature can improve computing performance to certain
 383           applications by speeding up page faults during memory
 384           allocation, by reducing the number of tlb misses and by speeding
 385           up the pagetable walking.
 386
 387           If memory constrained on embedded, you may want to say N.
 388
 389 choice
 390         prompt "Transparent Hugepage Support sysfs defaults"
 391         depends on TRANSPARENT_HUGEPAGE
 392         default TRANSPARENT_HUGEPAGE_ALWAYS
 393         help
 394           Selects the sysfs defaults for Transparent Hugepage Support.
 395
 396         config TRANSPARENT_HUGEPAGE_ALWAYS
 397                 bool "always"
 398         help
 399           Enabling Transparent Hugepage always, can increase the
 400           memory footprint of applications without a guaranteed
 401           benefit but it will work automatically for all applications.
 402
 403         config TRANSPARENT_HUGEPAGE_MADVISE
 404                 bool "madvise"
 405         help
 406           Enabling Transparent Hugepage madvise, will only provide a
 407           performance improvement benefit to the applications using
 408           madvise(MADV_HUGEPAGE) but it won't risk to increase the
 409           memory footprint of applications without a guaranteed
 410           benefit.
 411 endchoice
 412
 413 config ARCH_WANTS_THP_SWAP
 414        def_bool n
 415
 416 config THP_SWAP
 417         def_bool y
 418         depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
 419         help
 420           Swap transparent huge pages in one piece, without splitting.
 421           XXX: For now, swap cluster backing transparent huge page
 422           will be split after swapout.
 423
 424           For selection by architectures with reasonable THP sizes.
 425
 426 config  TRANSPARENT_HUGE_PAGECACHE
 427         def_bool y
 428         depends on TRANSPARENT_HUGEPAGE
 429
 430 #
 431 # UP and nommu archs use km based percpu allocator
 432 #
 433 config NEED_PER_CPU_KM
 434         depends on !SMP
 435         bool
 436         default y
 437
 438 config CLEANCACHE
 439         bool "Enable cleancache driver to cache clean pages if tmem is present"
 440         help
 441           Cleancache can be thought of as a page-granularity victim cache
 442           for clean pages that the kernel's pageframe replacement algorithm
 443           (PFRA) would like to keep around, but can't since there isn't enough
 444           memory.  So when the PFRA "evicts" a page, it first attempts to use
 445           cleancache code to put the data contained in that page into
 446           "transcendent memory", memory that is not directly accessible or
 447           addressable by the kernel and is of unknown and possibly
 448           time-varying size.  And when a cleancache-enabled
 449           filesystem wishes to access a page in a file on disk, it first
 450           checks cleancache to see if it already contains it; if it does,
 451           the page is copied into the kernel and a disk access is avoided.
 452           When a transcendent memory driver is available (such as zcache or
 453           Xen transcendent memory), a significant I/O reduction
 454           may be achieved.  When none is available, all cleancache calls
 455           are reduced to a single pointer-compare-against-NULL resulting
 456           in a negligible performance hit.
 457
 458           If unsure, say Y to enable cleancache
 459
 460 config FRONTSWAP
 461         bool "Enable frontswap to cache swap pages if tmem is present"
 462         depends on SWAP
 463         help
 464           Frontswap is so named because it can be thought of as the opposite
 465           of a "backing" store for a swap device.  The data is stored into
 466           "transcendent memory", memory that is not directly accessible or
 467           addressable by the kernel and is of unknown and possibly
 468           time-varying size.  When space in transcendent memory is available,
 469           a significant swap I/O reduction may be achieved.  When none is
 470           available, all frontswap calls are reduced to a single pointer-
 471           compare-against-NULL resulting in a negligible performance hit
 472           and swap data is stored as normal on the matching swap device.
 473
 474           If unsure, say Y to enable frontswap.
 475
 476 config CMA
 477         bool "Contiguous Memory Allocator"
 478         depends on MMU
 479         select MIGRATION
 480         select MEMORY_ISOLATION
 481         help
 482           This enables the Contiguous Memory Allocator which allows other
 483           subsystems to allocate big physically-contiguous blocks of memory.
 484           CMA reserves a region of memory and allows only movable pages to
 485           be allocated from it. This way, the kernel can use the memory for
 486           pagecache and when a subsystem requests for contiguous area, the
 487           allocated pages are migrated away to serve the contiguous request.
 488
 489           If unsure, say "n".
 490
 491 config CMA_DEBUG
 492         bool "CMA debug messages (DEVELOPMENT)"
 493         depends on DEBUG_KERNEL && CMA
 494         help
 495           Turns on debug messages in CMA.  This produces KERN_DEBUG
 496           messages for every CMA call as well as various messages while
 497           processing calls such as dma_alloc_from_contiguous().
 498           This option does not affect warning and error messages.
 499
 500 config CMA_DEBUGFS
 501         bool "CMA debugfs interface"
 502         depends on CMA && DEBUG_FS
 503         help
 504           Turns on the DebugFS interface for CMA.
 505
 506 config CMA_AREAS
 507         int "Maximum count of the CMA areas"
 508         depends on CMA
 509         default 7
 510         help
 511           CMA allows to create CMA areas for particular purpose, mainly,
 512           used as device private area. This parameter sets the maximum
 513           number of CMA area in the system.
 514
 515           If unsure, leave the default value "7".
 516
 517 config MEM_SOFT_DIRTY
 518         bool "Track memory changes"
 519         depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
 520         select PROC_PAGE_MONITOR
 521         help
 522           This option enables memory changes tracking by introducing a
 523           soft-dirty bit on pte-s. This bit it set when someone writes
 524           into a page just as regular dirty bit, but unlike the latter
 525           it can be cleared by hands.
 526
 527           See Documentation/admin-guide/mm/soft-dirty.rst for more details.
 528
 529 config ZSWAP
 530         bool "Compressed cache for swap pages (EXPERIMENTAL)"
 531         depends on FRONTSWAP && CRYPTO=y
 532         select CRYPTO_LZO
 533         select ZPOOL
 534         help
 535           A lightweight compressed cache for swap pages.  It takes
 536           pages that are in the process of being swapped out and attempts to
 537           compress them into a dynamically allocated RAM-based memory pool.
 538           This can result in a significant I/O reduction on swap device and,
 539           in the case where decompressing from RAM is faster that swap device
 540           reads, can also improve workload performance.
 541
 542           This is marked experimental because it is a new feature (as of
 543           v3.11) that interacts heavily with memory reclaim.  While these
 544           interactions don't cause any known issues on simple memory setups,
 545           they have not be fully explored on the large set of potential
 546           configurations and workloads that exist.
 547
 548 config ZPOOL
 549         tristate "Common API for compressed memory storage"
 550         help
 551           Compressed memory storage API.  This allows using either zbud or
 552           zsmalloc.
 553
 554 config ZBUD
 555         tristate "Low (Up to 2x) density storage for compressed pages"
 556         help
 557           A special purpose allocator for storing compressed pages.
 558           It is designed to store up to two compressed pages per physical
 559           page.  While this design limits storage density, it has simple and
 560           deterministic reclaim properties that make it preferable to a higher
 561           density approach when reclaim will be used.
 562
 563 config Z3FOLD
 564         tristate "Up to 3x density storage for compressed pages"
 565         depends on ZPOOL
 566         help
 567           A special purpose allocator for storing compressed pages.
 568           It is designed to store up to three compressed pages per physical
 569           page. It is a ZBUD derivative so the simplicity and determinism are
 570           still there.
 571
 572 config ZSMALLOC
 573         tristate "Memory allocator for compressed pages"
 574         depends on MMU
 575         help
 576           zsmalloc is a slab-based memory allocator designed to store
 577           compressed RAM pages.  zsmalloc uses virtual memory mapping
 578           in order to reduce fragmentation.  However, this results in a
 579           non-standard allocator interface where a handle, not a pointer, is
 580           returned by an alloc().  This handle must be mapped in order to
 581           access the allocated space.
 582
 583 config PGTABLE_MAPPING
 584         bool "Use page table mapping to access object in zsmalloc"
 585         depends on ZSMALLOC
 586         help
 587           By default, zsmalloc uses a copy-based object mapping method to
 588           access allocations that span two pages. However, if a particular
 589           architecture (ex, ARM) performs VM mapping faster than copying,
 590           then you should select this. This causes zsmalloc to use page table
 591           mapping rather than copying for object mapping.
 592
 593           You can check speed with zsmalloc benchmark:
 594           https://github.com/spartacus06/zsmapbench
 595
 596 config ZSMALLOC_STAT
 597         bool "Export zsmalloc statistics"
 598         depends on ZSMALLOC
 599         select DEBUG_FS
 600         help
 601           This option enables code in the zsmalloc to collect various
 602           statistics about whats happening in zsmalloc and exports that
 603           information to userspace via debugfs.
 604           If unsure, say N.
 605
 606 config GENERIC_EARLY_IOREMAP
 607         bool
 608
 609 config MAX_STACK_SIZE_MB
 610         int "Maximum user stack size for 32-bit processes (MB)"
 611         default 80
 612         range 8 2048
 613         depends on STACK_GROWSUP && (!64BIT || COMPAT)
 614         help
 615           This is the maximum stack size in Megabytes in the VM layout of 32-bit
 616           user processes when the stack grows upwards (currently only on parisc
 617           arch). The stack will be located at the highest memory address minus
 618           the given value, unless the RLIMIT_STACK hard limit is changed to a
 619           smaller value in which case that is used.
 620
 621           A sane initial value is 80 MB.
 622
 623 config DEFERRED_STRUCT_PAGE_INIT
 624         bool "Defer initialisation of struct pages to kthreads"
 625         depends on SPARSEMEM
 626         depends on !NEED_PER_CPU_KM
 627         depends on 64BIT
 628         help
 629           Ordinarily all struct pages are initialised during early boot in a
 630           single thread. On very large machines this can take a considerable
 631           amount of time. If this option is set, large machines will bring up
 632           a subset of memmap at boot and then initialise the rest in parallel
 633           by starting one-off "pgdatinitX" kernel thread for each node X. This
 634           has a potential performance impact on processes running early in the
 635           lifetime of the system until these kthreads finish the
 636           initialisation.
 637
 638 config IDLE_PAGE_TRACKING
 639         bool "Enable idle page tracking"
 640         depends on SYSFS && MMU
 641         select PAGE_EXTENSION if !64BIT
 642         help
 643           This feature allows to estimate the amount of user pages that have
 644           not been touched during a given period of time. This information can
 645           be useful to tune memory cgroup limits and/or for job placement
 646           within a compute cluster.
 647
 648           See Documentation/admin-guide/mm/idle_page_tracking.rst for
 649           more details.
 650
 651 # arch_add_memory() comprehends device memory
 652 config ARCH_HAS_ZONE_DEVICE
 653         bool
 654
 655 config ZONE_DEVICE
 656         bool "Device memory (pmem, HMM, etc...) hotplug support"
 657         depends on MEMORY_HOTPLUG
 658         depends on MEMORY_HOTREMOVE
 659         depends on SPARSEMEM_VMEMMAP
 660         depends on ARCH_HAS_ZONE_DEVICE
 661         select XARRAY_MULTI
 662
 663         help
 664           Device memory hotplug support allows for establishing pmem,
 665           or other device driver discovered memory regions, in the
 666           memmap. This allows pfn_to_page() lookups of otherwise
 667           "device-physical" addresses which is needed for using a DAX
 668           mapping in an O_DIRECT operation, among other things.
 669
 670           If FS_DAX is enabled, then say Y.
 671
 672 config ARCH_HAS_HMM_MIRROR
 673         bool
 674         default y
 675         depends on (X86_64 || PPC64)
 676         depends on MMU && 64BIT
 677
 678 config ARCH_HAS_HMM_DEVICE
 679         bool
 680         default y
 681         depends on (X86_64 || PPC64)
 682         depends on MEMORY_HOTPLUG
 683         depends on MEMORY_HOTREMOVE
 684         depends on SPARSEMEM_VMEMMAP
 685         depends on ARCH_HAS_ZONE_DEVICE
 686         select XARRAY_MULTI
 687
 688 config ARCH_HAS_HMM
 689         bool
 690         default y
 691         depends on (X86_64 || PPC64)
 692         depends on ZONE_DEVICE
 693         depends on MMU && 64BIT
 694         depends on MEMORY_HOTPLUG
 695         depends on MEMORY_HOTREMOVE
 696         depends on SPARSEMEM_VMEMMAP
 697
 698 config MIGRATE_VMA_HELPER
 699         bool
 700
 701 config DEV_PAGEMAP_OPS
 702         bool
 703
 704 config HMM
 705         bool
 706         select MMU_NOTIFIER
 707         select MIGRATE_VMA_HELPER
 708
 709 config HMM_MIRROR
 710         bool "HMM mirror CPU page table into a device page table"
 711         depends on ARCH_HAS_HMM
 712         select HMM
 713         help
 714           Select HMM_MIRROR if you want to mirror range of the CPU page table of a
 715           process into a device page table. Here, mirror means "keep synchronized".
 716           Prerequisites: the device must provide the ability to write-protect its
 717           page tables (at PAGE_SIZE granularity), and must be able to recover from
 718           the resulting potential page faults.
 719
 720 config DEVICE_PRIVATE
 721         bool "Unaddressable device memory (GPU memory, ...)"
 722         depends on ARCH_HAS_HMM
 723         select HMM
 724         select DEV_PAGEMAP_OPS
 725
 726         help
 727           Allows creation of struct pages to represent unaddressable device
 728           memory; i.e., memory that is only accessible from the device (or
 729           group of devices). You likely also want to select HMM_MIRROR.
 730
 731 config DEVICE_PUBLIC
 732         bool "Addressable device memory (like GPU memory)"
 733         depends on ARCH_HAS_HMM
 734         select HMM
 735         select DEV_PAGEMAP_OPS
 736
 737         help
 738           Allows creation of struct pages to represent addressable device
 739           memory; i.e., memory that is accessible from both the device and
 740           the CPU
 741
 742 config FRAME_VECTOR
 743         bool
 744
 745 config ARCH_USES_HIGH_VMA_FLAGS
 746         bool
 747 config ARCH_HAS_PKEYS
 748         bool
 749
 750 config PERCPU_STATS
 751         bool "Collect percpu memory statistics"
 752         help
 753           This feature collects and exposes statistics via debugfs. The
 754           information includes global and per chunk statistics, which can
 755           be used to help understand percpu memory usage.
 756
 757 config GUP_BENCHMARK
 758         bool "Enable infrastructure for get_user_pages_fast() benchmarking"
 759         help
 760           Provides /sys/kernel/debug/gup_benchmark that helps with testing
 761           performance of get_user_pages_fast().
 762
 763           See tools/testing/selftests/vm/gup_benchmark.c
 764
 765 config ARCH_HAS_PTE_SPECIAL
 766         bool
 767
 768 endmenu