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