mm/Kconfig

   1 config SELECT_MEMORY_MODEL
   2         def_bool y
   3         depends on ARCH_SELECT_MEMORY_MODEL
   4
   5 choice
   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
  12 config 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
  31 config 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
  47 config 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
  62 endchoice
  63
  64 config DISCONTIGMEM
  65         def_bool y
  66         depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
  67
  68 config SPARSEMEM
  69         def_bool y
  70         depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
  71
  72 config FLATMEM
  73         def_bool y
  74         depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
  75
  76 config 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 #
  85 config NEED_MULTIPLE_NODES
  86         def_bool y
  87         depends on DISCONTIGMEM || NUMA
  88
  89 config 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 #
 103 config 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 #
 111 config SPARSEMEM_EXTREME
 112         def_bool y
 113         depends on SPARSEMEM && !SPARSEMEM_STATIC
 114
 115 config SPARSEMEM_VMEMMAP_ENABLE
 116         bool
 117
 118 config SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
 119         def_bool y
 120         depends on SPARSEMEM && X86_64
 121
 122 config 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
 131 config HAVE_MEMBLOCK
 132         bool
 133
 134 config HAVE_MEMBLOCK_NODE_MAP
 135         bool
 136
 137 config HAVE_MEMBLOCK_PHYS_MAP
 138         bool
 139
 140 config HAVE_GENERIC_RCU_GUP
 141         bool
 142
 143 config ARCH_DISCARD_MEMBLOCK
 144         bool
 145
 146 config NO_BOOTMEM
 147         bool
 148
 149 config MEMORY_ISOLATION
 150         bool
 151
 152 config 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 #
 182 config HAVE_BOOTMEM_INFO_NODE
 183         def_bool n
 184
 185 # eventually, we can have this option just 'select SPARSEMEM'
 186 config 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 !KASAN
 191
 192 config MEMORY_HOTPLUG_SPARSE
 193         def_bool y
 194         depends on SPARSEMEM && MEMORY_HOTPLUG
 195
 196 config MEMORY_HOTPLUG_DEFAULT_ONLINE
 197         bool "Online the newly added memory blocks by default"
 198         default n
 199         depends on MEMORY_HOTPLUG
 200         help
 201           This option sets the default policy setting for memory hotplug
 202           onlining policy (/sys/devices/system/memory/auto_online_blocks) which
 203           determines what happens to newly added memory regions. Policy setting
 204           can always be changed at runtime.
 205           See Documentation/memory-hotplug.txt for more information.
 206
 207           Say Y here if you want all hot-plugged memory blocks to appear in
 208           'online' state by default.
 209           Say N here if you want the default policy to keep all hot-plugged
 210           memory blocks in 'offline' state.
 211
 212 config MEMORY_HOTREMOVE
 213         bool "Allow for memory hot remove"
 214         select MEMORY_ISOLATION
 215         select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
 216         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 217         depends on MIGRATION
 218
 219 # Heavily threaded applications may benefit from splitting the mm-wide
 220 # page_table_lock, so that faults on different parts of the user address
 221 # space can be handled with less contention: split it at this NR_CPUS.
 222 # Default to 4 for wider testing, though 8 might be more appropriate.
 223 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 224 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 225 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
 226 #
 227 config SPLIT_PTLOCK_CPUS
 228         int
 229         default "999999" if !MMU
 230         default "999999" if ARM && !CPU_CACHE_VIPT
 231         default "999999" if PARISC && !PA20
 232         default "4"
 233
 234 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
 235         bool
 236
 237 #
 238 # support for memory balloon
 239 config MEMORY_BALLOON
 240         bool
 241
 242 #
 243 # support for memory balloon compaction
 244 config BALLOON_COMPACTION
 245         bool "Allow for balloon memory compaction/migration"
 246         def_bool y
 247         depends on COMPACTION && MEMORY_BALLOON
 248         help
 249           Memory fragmentation introduced by ballooning might reduce
 250           significantly the number of 2MB contiguous memory blocks that can be
 251           used within a guest, thus imposing performance penalties associated
 252           with the reduced number of transparent huge pages that could be used
 253           by the guest workload. Allowing the compaction & migration for memory
 254           pages enlisted as being part of memory balloon devices avoids the
 255           scenario aforementioned and helps improving memory defragmentation.
 256
 257 #
 258 # support for memory compaction
 259 config COMPACTION
 260         bool "Allow for memory compaction"
 261         def_bool y
 262         select MIGRATION
 263         depends on MMU
 264         help
 265           Allows the compaction of memory for the allocation of huge pages.
 266
 267 #
 268 # support for page migration
 269 #
 270 config MIGRATION
 271         bool "Page migration"
 272         def_bool y
 273         depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
 274         help
 275           Allows the migration of the physical location of pages of processes
 276           while the virtual addresses are not changed. This is useful in
 277           two situations. The first is on NUMA systems to put pages nearer
 278           to the processors accessing. The second is when allocating huge
 279           pages as migration can relocate pages to satisfy a huge page
 280           allocation instead of reclaiming.
 281
 282 config ARCH_ENABLE_HUGEPAGE_MIGRATION
 283         bool
 284
 285 config PHYS_ADDR_T_64BIT
 286         def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
 287
 288 config BOUNCE
 289         bool "Enable bounce buffers"
 290         default y
 291         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 292         help
 293           Enable bounce buffers for devices that cannot access
 294           the full range of memory available to the CPU. Enabled
 295           by default when ZONE_DMA or HIGHMEM is selected, but you
 296           may say n to override this.
 297
 298 # On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
 299 # have more than 4GB of memory, but we don't currently use the IOTLB to present
 300 # a 32-bit address to OHCI.  So we need to use a bounce pool instead.
 301 config NEED_BOUNCE_POOL
 302         bool
 303         default y if TILE && USB_OHCI_HCD
 304
 305 config NR_QUICK
 306         int
 307         depends on QUICKLIST
 308         default "2" if AVR32
 309         default "1"
 310
 311 config VIRT_TO_BUS
 312         bool
 313         help
 314           An architecture should select this if it implements the
 315           deprecated interface virt_to_bus().  All new architectures
 316           should probably not select this.
 317
 318
 319 config MMU_NOTIFIER
 320         bool
 321         select SRCU
 322
 323 config KSM
 324         bool "Enable KSM for page merging"
 325         depends on MMU
 326         help
 327           Enable Kernel Samepage Merging: KSM periodically scans those areas
 328           of an application's address space that an app has advised may be
 329           mergeable.  When it finds pages of identical content, it replaces
 330           the many instances by a single page with that content, so
 331           saving memory until one or another app needs to modify the content.
 332           Recommended for use with KVM, or with other duplicative applications.
 333           See Documentation/vm/ksm.txt for more information: KSM is inactive
 334           until a program has madvised that an area is MADV_MERGEABLE, and
 335           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 336
 337 config DEFAULT_MMAP_MIN_ADDR
 338         int "Low address space to protect from user allocation"
 339         depends on MMU
 340         default 4096
 341         help
 342           This is the portion of low virtual memory which should be protected
 343           from userspace allocation.  Keeping a user from writing to low pages
 344           can help reduce the impact of kernel NULL pointer bugs.
 345
 346           For most ia64, ppc64 and x86 users with lots of address space
 347           a value of 65536 is reasonable and should cause no problems.
 348           On arm and other archs it should not be higher than 32768.
 349           Programs which use vm86 functionality or have some need to map
 350           this low address space will need CAP_SYS_RAWIO or disable this
 351           protection by setting the value to 0.
 352
 353           This value can be changed after boot using the
 354           /proc/sys/vm/mmap_min_addr tunable.
 355
 356 config ARCH_SUPPORTS_MEMORY_FAILURE
 357         bool
 358
 359 config MEMORY_FAILURE
 360         depends on MMU
 361         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 362         bool "Enable recovery from hardware memory errors"
 363         select MEMORY_ISOLATION
 364         select RAS
 365         help
 366           Enables code to recover from some memory failures on systems
 367           with MCA recovery. This allows a system to continue running
 368           even when some of its memory has uncorrected errors. This requires
 369           special hardware support and typically ECC memory.
 370
 371 config HWPOISON_INJECT
 372         tristate "HWPoison pages injector"
 373         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 374         select PROC_PAGE_MONITOR
 375
 376 config NOMMU_INITIAL_TRIM_EXCESS
 377         int "Turn on mmap() excess space trimming before booting"
 378         depends on !MMU
 379         default 1
 380         help
 381           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 382           of memory on which to store mappings, but it can only ask the system
 383           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 384           more than it requires.  To deal with this, mmap() is able to trim off
 385           the excess and return it to the allocator.
 386
 387           If trimming is enabled, the excess is trimmed off and returned to the
 388           system allocator, which can cause extra fragmentation, particularly
 389           if there are a lot of transient processes.
 390
 391           If trimming is disabled, the excess is kept, but not used, which for
 392           long-term mappings means that the space is wasted.
 393
 394           Trimming can be dynamically controlled through a sysctl option
 395           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 396           excess pages there must be before trimming should occur, or zero if
 397           no trimming is to occur.
 398
 399           This option specifies the initial value of this option.  The default
 400           of 1 says that all excess pages should be trimmed.
 401
 402           See Documentation/nommu-mmap.txt for more information.
 403
 404 config TRANSPARENT_HUGEPAGE
 405         bool "Transparent Hugepage Support"
 406         depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
 407         select COMPACTION
 408         select RADIX_TREE_MULTIORDER
 409         help
 410           Transparent Hugepages allows the kernel to use huge pages and
 411           huge tlb transparently to the applications whenever possible.
 412           This feature can improve computing performance to certain
 413           applications by speeding up page faults during memory
 414           allocation, by reducing the number of tlb misses and by speeding
 415           up the pagetable walking.
 416
 417           If memory constrained on embedded, you may want to say N.
 418
 419 choice
 420         prompt "Transparent Hugepage Support sysfs defaults"
 421         depends on TRANSPARENT_HUGEPAGE
 422         default TRANSPARENT_HUGEPAGE_ALWAYS
 423         help
 424           Selects the sysfs defaults for Transparent Hugepage Support.
 425
 426         config TRANSPARENT_HUGEPAGE_ALWAYS
 427                 bool "always"
 428         help
 429           Enabling Transparent Hugepage always, can increase the
 430           memory footprint of applications without a guaranteed
 431           benefit but it will work automatically for all applications.
 432
 433         config TRANSPARENT_HUGEPAGE_MADVISE
 434                 bool "madvise"
 435         help
 436           Enabling Transparent Hugepage madvise, will only provide a
 437           performance improvement benefit to the applications using
 438           madvise(MADV_HUGEPAGE) but it won't risk to increase the
 439           memory footprint of applications without a guaranteed
 440           benefit.
 441 endchoice
 442
 443 #
 444 # We don't deposit page tables on file THP mapping,
 445 # but Power makes use of them to address MMU quirk.
 446 #
 447 config  TRANSPARENT_HUGE_PAGECACHE
 448         def_bool y
 449         depends on TRANSPARENT_HUGEPAGE && !PPC
 450
 451 #
 452 # UP and nommu archs use km based percpu allocator
 453 #
 454 config NEED_PER_CPU_KM
 455         depends on !SMP
 456         bool
 457         default y
 458
 459 config CLEANCACHE
 460         bool "Enable cleancache driver to cache clean pages if tmem is present"
 461         default n
 462         help
 463           Cleancache can be thought of as a page-granularity victim cache
 464           for clean pages that the kernel's pageframe replacement algorithm
 465           (PFRA) would like to keep around, but can't since there isn't enough
 466           memory.  So when the PFRA "evicts" a page, it first attempts to use
 467           cleancache code to put the data contained in that page into
 468           "transcendent memory", memory that is not directly accessible or
 469           addressable by the kernel and is of unknown and possibly
 470           time-varying size.  And when a cleancache-enabled
 471           filesystem wishes to access a page in a file on disk, it first
 472           checks cleancache to see if it already contains it; if it does,
 473           the page is copied into the kernel and a disk access is avoided.
 474           When a transcendent memory driver is available (such as zcache or
 475           Xen transcendent memory), a significant I/O reduction
 476           may be achieved.  When none is available, all cleancache calls
 477           are reduced to a single pointer-compare-against-NULL resulting
 478           in a negligible performance hit.
 479
 480           If unsure, say Y to enable cleancache
 481
 482 config FRONTSWAP
 483         bool "Enable frontswap to cache swap pages if tmem is present"
 484         depends on SWAP
 485         default n
 486         help
 487           Frontswap is so named because it can be thought of as the opposite
 488           of a "backing" store for a swap device.  The data is stored into
 489           "transcendent memory", memory that is not directly accessible or
 490           addressable by the kernel and is of unknown and possibly
 491           time-varying size.  When space in transcendent memory is available,
 492           a significant swap I/O reduction may be achieved.  When none is
 493           available, all frontswap calls are reduced to a single pointer-
 494           compare-against-NULL resulting in a negligible performance hit
 495           and swap data is stored as normal on the matching swap device.
 496
 497           If unsure, say Y to enable frontswap.
 498
 499 config CMA
 500         bool "Contiguous Memory Allocator"
 501         depends on HAVE_MEMBLOCK && MMU
 502         select MIGRATION
 503         select MEMORY_ISOLATION
 504         help
 505           This enables the Contiguous Memory Allocator which allows other
 506           subsystems to allocate big physically-contiguous blocks of memory.
 507           CMA reserves a region of memory and allows only movable pages to
 508           be allocated from it. This way, the kernel can use the memory for
 509           pagecache and when a subsystem requests for contiguous area, the
 510           allocated pages are migrated away to serve the contiguous request.
 511
 512           If unsure, say "n".
 513
 514 config CMA_DEBUG
 515         bool "CMA debug messages (DEVELOPMENT)"
 516         depends on DEBUG_KERNEL && CMA
 517         help
 518           Turns on debug messages in CMA.  This produces KERN_DEBUG
 519           messages for every CMA call as well as various messages while
 520           processing calls such as dma_alloc_from_contiguous().
 521           This option does not affect warning and error messages.
 522
 523 config CMA_DEBUGFS
 524         bool "CMA debugfs interface"
 525         depends on CMA && DEBUG_FS
 526         help
 527           Turns on the DebugFS interface for CMA.
 528
 529 config CMA_AREAS
 530         int "Maximum count of the CMA areas"
 531         depends on CMA
 532         default 7
 533         help
 534           CMA allows to create CMA areas for particular purpose, mainly,
 535           used as device private area. This parameter sets the maximum
 536           number of CMA area in the system.
 537
 538           If unsure, leave the default value "7".
 539
 540 config MEM_SOFT_DIRTY
 541         bool "Track memory changes"
 542         depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
 543         select PROC_PAGE_MONITOR
 544         help
 545           This option enables memory changes tracking by introducing a
 546           soft-dirty bit on pte-s. This bit it set when someone writes
 547           into a page just as regular dirty bit, but unlike the latter
 548           it can be cleared by hands.
 549
 550           See Documentation/vm/soft-dirty.txt for more details.
 551
 552 config ZSWAP
 553         bool "Compressed cache for swap pages (EXPERIMENTAL)"
 554         depends on FRONTSWAP && CRYPTO=y
 555         select CRYPTO_LZO
 556         select ZPOOL
 557         default n
 558         help
 559           A lightweight compressed cache for swap pages.  It takes
 560           pages that are in the process of being swapped out and attempts to
 561           compress them into a dynamically allocated RAM-based memory pool.
 562           This can result in a significant I/O reduction on swap device and,
 563           in the case where decompressing from RAM is faster that swap device
 564           reads, can also improve workload performance.
 565
 566           This is marked experimental because it is a new feature (as of
 567           v3.11) that interacts heavily with memory reclaim.  While these
 568           interactions don't cause any known issues on simple memory setups,
 569           they have not be fully explored on the large set of potential
 570           configurations and workloads that exist.
 571
 572 config ZPOOL
 573         tristate "Common API for compressed memory storage"
 574         default n
 575         help
 576           Compressed memory storage API.  This allows using either zbud or
 577           zsmalloc.
 578
 579 config ZBUD
 580         tristate "Low (Up to 2x) density storage for compressed pages"
 581         default n
 582         help
 583           A special purpose allocator for storing compressed pages.
 584           It is designed to store up to two compressed pages per physical
 585           page.  While this design limits storage density, it has simple and
 586           deterministic reclaim properties that make it preferable to a higher
 587           density approach when reclaim will be used.
 588
 589 config Z3FOLD
 590         tristate "Up to 3x density storage for compressed pages"
 591         depends on ZPOOL
 592         default n
 593         help
 594           A special purpose allocator for storing compressed pages.
 595           It is designed to store up to three compressed pages per physical
 596           page. It is a ZBUD derivative so the simplicity and determinism are
 597           still there.
 598
 599 config ZSMALLOC
 600         tristate "Memory allocator for compressed pages"
 601         depends on MMU
 602         default n
 603         help
 604           zsmalloc is a slab-based memory allocator designed to store
 605           compressed RAM pages.  zsmalloc uses virtual memory mapping
 606           in order to reduce fragmentation.  However, this results in a
 607           non-standard allocator interface where a handle, not a pointer, is
 608           returned by an alloc().  This handle must be mapped in order to
 609           access the allocated space.
 610
 611 config PGTABLE_MAPPING
 612         bool "Use page table mapping to access object in zsmalloc"
 613         depends on ZSMALLOC
 614         help
 615           By default, zsmalloc uses a copy-based object mapping method to
 616           access allocations that span two pages. However, if a particular
 617           architecture (ex, ARM) performs VM mapping faster than copying,
 618           then you should select this. This causes zsmalloc to use page table
 619           mapping rather than copying for object mapping.
 620
 621           You can check speed with zsmalloc benchmark:
 622           https://github.com/spartacus06/zsmapbench
 623
 624 config ZSMALLOC_STAT
 625         bool "Export zsmalloc statistics"
 626         depends on ZSMALLOC
 627         select DEBUG_FS
 628         help
 629           This option enables code in the zsmalloc to collect various
 630           statistics about whats happening in zsmalloc and exports that
 631           information to userspace via debugfs.
 632           If unsure, say N.
 633
 634 config GENERIC_EARLY_IOREMAP
 635         bool
 636
 637 config MAX_STACK_SIZE_MB
 638         int "Maximum user stack size for 32-bit processes (MB)"
 639         default 80
 640         range 8 256 if METAG
 641         range 8 2048
 642         depends on STACK_GROWSUP && (!64BIT || COMPAT)
 643         help
 644           This is the maximum stack size in Megabytes in the VM layout of 32-bit
 645           user processes when the stack grows upwards (currently only on parisc
 646           and metag arch). The stack will be located at the highest memory
 647           address minus the given value, unless the RLIMIT_STACK hard limit is
 648           changed to a smaller value in which case that is used.
 649
 650           A sane initial value is 80 MB.
 651
 652 # For architectures that support deferred memory initialisation
 653 config ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
 654         bool
 655
 656 config DEFERRED_STRUCT_PAGE_INIT
 657         bool "Defer initialisation of struct pages to kthreads"
 658         default n
 659         depends on ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
 660         depends on NO_BOOTMEM && MEMORY_HOTPLUG
 661         depends on !FLATMEM
 662         help
 663           Ordinarily all struct pages are initialised during early boot in a
 664           single thread. On very large machines this can take a considerable
 665           amount of time. If this option is set, large machines will bring up
 666           a subset of memmap at boot and then initialise the rest in parallel
 667           by starting one-off "pgdatinitX" kernel thread for each node X. This
 668           has a potential performance impact on processes running early in the
 669           lifetime of the system until these kthreads finish the
 670           initialisation.
 671
 672 config IDLE_PAGE_TRACKING
 673         bool "Enable idle page tracking"
 674         depends on SYSFS && MMU
 675         select PAGE_EXTENSION if !64BIT
 676         help
 677           This feature allows to estimate the amount of user pages that have
 678           not been touched during a given period of time. This information can
 679           be useful to tune memory cgroup limits and/or for job placement
 680           within a compute cluster.
 681
 682           See Documentation/vm/idle_page_tracking.txt for more details.
 683
 684 config ZONE_DEVICE
 685         bool "Device memory (pmem, etc...) hotplug support"
 686         depends on MEMORY_HOTPLUG
 687         depends on MEMORY_HOTREMOVE
 688         depends on SPARSEMEM_VMEMMAP
 689         depends on X86_64 #arch_add_memory() comprehends device memory
 690
 691         help
 692           Device memory hotplug support allows for establishing pmem,
 693           or other device driver discovered memory regions, in the
 694           memmap. This allows pfn_to_page() lookups of otherwise
 695           "device-physical" addresses which is needed for using a DAX
 696           mapping in an O_DIRECT operation, among other things.
 697
 698           If FS_DAX is enabled, then say Y.
 699
 700 config FRAME_VECTOR
 701         bool
 702
 703 config ARCH_USES_HIGH_VMA_FLAGS
 704         bool
 705 config ARCH_HAS_PKEYS
 706         bool