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_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 #
 153 # Only be set on architectures that have completely implemented memory hotplug
 154 # feature. If you are not sure, don't touch it.
 155 #
 156 config HAVE_BOOTMEM_INFO_NODE
 157         def_bool n
 158
 159 # eventually, we can have this option just 'select SPARSEMEM'
 160 config MEMORY_HOTPLUG
 161         bool "Allow for memory hot-add"
 162         depends on SPARSEMEM || X86_64_ACPI_NUMA
 163         depends on ARCH_ENABLE_MEMORY_HOTPLUG
 164
 165 config MEMORY_HOTPLUG_SPARSE
 166         def_bool y
 167         depends on SPARSEMEM && MEMORY_HOTPLUG
 168
 169 config MEMORY_HOTPLUG_DEFAULT_ONLINE
 170         bool "Online the newly added memory blocks by default"
 171         default n
 172         depends on MEMORY_HOTPLUG
 173         help
 174           This option sets the default policy setting for memory hotplug
 175           onlining policy (/sys/devices/system/memory/auto_online_blocks) which
 176           determines what happens to newly added memory regions. Policy setting
 177           can always be changed at runtime.
 178           See Documentation/memory-hotplug.txt for more information.
 179
 180           Say Y here if you want all hot-plugged memory blocks to appear in
 181           'online' state by default.
 182           Say N here if you want the default policy to keep all hot-plugged
 183           memory blocks in 'offline' state.
 184
 185 config MEMORY_HOTREMOVE
 186         bool "Allow for memory hot remove"
 187         select MEMORY_ISOLATION
 188         select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
 189         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 190         depends on MIGRATION
 191
 192 # Heavily threaded applications may benefit from splitting the mm-wide
 193 # page_table_lock, so that faults on different parts of the user address
 194 # space can be handled with less contention: split it at this NR_CPUS.
 195 # Default to 4 for wider testing, though 8 might be more appropriate.
 196 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 197 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 198 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
 199 #
 200 config SPLIT_PTLOCK_CPUS
 201         int
 202         default "999999" if !MMU
 203         default "999999" if ARM && !CPU_CACHE_VIPT
 204         default "999999" if PARISC && !PA20
 205         default "4"
 206
 207 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
 208         bool
 209
 210 #
 211 # support for memory balloon
 212 config MEMORY_BALLOON
 213         bool
 214
 215 #
 216 # support for memory balloon compaction
 217 config BALLOON_COMPACTION
 218         bool "Allow for balloon memory compaction/migration"
 219         def_bool y
 220         depends on COMPACTION && MEMORY_BALLOON
 221         help
 222           Memory fragmentation introduced by ballooning might reduce
 223           significantly the number of 2MB contiguous memory blocks that can be
 224           used within a guest, thus imposing performance penalties associated
 225           with the reduced number of transparent huge pages that could be used
 226           by the guest workload. Allowing the compaction & migration for memory
 227           pages enlisted as being part of memory balloon devices avoids the
 228           scenario aforementioned and helps improving memory defragmentation.
 229
 230 #
 231 # support for memory compaction
 232 config COMPACTION
 233         bool "Allow for memory compaction"
 234         def_bool y
 235         select MIGRATION
 236         depends on MMU
 237         help
 238           Compaction is the only memory management component to form
 239           high order (larger physically contiguous) memory blocks
 240           reliably. The page allocator relies on compaction heavily and
 241           the lack of the feature can lead to unexpected OOM killer
 242           invocations for high order memory requests. You shouldn't
 243           disable this option unless there really is a strong reason for
 244           it and then we would be really interested to hear about that at
 245           linux-mm@kvack.org.
 246
 247 config PROCESS_RECLAIM
 248         bool "Enable process reclaim"
 249         depends on PROC_FS
 250         default n
 251         help
 252          It allows to reclaim pages of the process by /proc/pid/reclaim.
 253
 254          (echo file > /proc/PID/reclaim) reclaims file-backed pages only.
 255          (echo anon > /proc/PID/reclaim) reclaims anonymous pages only.
 256          (echo all > /proc/PID/reclaim) reclaims all pages.
 257
 258          Any other value is ignored.
 259 #
 260 # support for page migration
 261 #
 262 config MIGRATION
 263         bool "Page migration"
 264         def_bool y
 265         depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
 266         help
 267           Allows the migration of the physical location of pages of processes
 268           while the virtual addresses are not changed. This is useful in
 269           two situations. The first is on NUMA systems to put pages nearer
 270           to the processors accessing. The second is when allocating huge
 271           pages as migration can relocate pages to satisfy a huge page
 272           allocation instead of reclaiming.
 273
 274 config ARCH_ENABLE_HUGEPAGE_MIGRATION
 275         bool
 276
 277 config ARCH_ENABLE_THP_MIGRATION
 278         bool
 279
 280 config PHYS_ADDR_T_64BIT
 281         def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
 282
 283 config BOUNCE
 284         bool "Enable bounce buffers"
 285         default y
 286         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 287         help
 288           Enable bounce buffers for devices that cannot access
 289           the full range of memory available to the CPU. Enabled
 290           by default when ZONE_DMA or HIGHMEM is selected, but you
 291           may say n to override this.
 292
 293 # On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
 294 # have more than 4GB of memory, but we don't currently use the IOTLB to present
 295 # a 32-bit address to OHCI.  So we need to use a bounce pool instead.
 296 config NEED_BOUNCE_POOL
 297         bool
 298         default y if TILE && USB_OHCI_HCD
 299
 300 config NR_QUICK
 301         int
 302         depends on QUICKLIST
 303         default "1"
 304
 305 config VIRT_TO_BUS
 306         bool
 307         help
 308           An architecture should select this if it implements the
 309           deprecated interface virt_to_bus().  All new architectures
 310           should probably not select this.
 311
 312
 313 config MMU_NOTIFIER
 314         bool
 315         select SRCU
 316
 317 config KSM
 318         bool "Enable KSM for page merging"
 319         depends on MMU
 320         help
 321           Enable Kernel Samepage Merging: KSM periodically scans those areas
 322           of an application's address space that an app has advised may be
 323           mergeable.  When it finds pages of identical content, it replaces
 324           the many instances by a single page with that content, so
 325           saving memory until one or another app needs to modify the content.
 326           Recommended for use with KVM, or with other duplicative applications.
 327           See Documentation/vm/ksm.txt for more information: KSM is inactive
 328           until a program has madvised that an area is MADV_MERGEABLE, and
 329           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 330
 331 config DEFAULT_MMAP_MIN_ADDR
 332         int "Low address space to protect from user allocation"
 333         depends on MMU
 334         default 4096
 335         help
 336           This is the portion of low virtual memory which should be protected
 337           from userspace allocation.  Keeping a user from writing to low pages
 338           can help reduce the impact of kernel NULL pointer bugs.
 339
 340           For most ia64, ppc64 and x86 users with lots of address space
 341           a value of 65536 is reasonable and should cause no problems.
 342           On arm and other archs it should not be higher than 32768.
 343           Programs which use vm86 functionality or have some need to map
 344           this low address space will need CAP_SYS_RAWIO or disable this
 345           protection by setting the value to 0.
 346
 347           This value can be changed after boot using the
 348           /proc/sys/vm/mmap_min_addr tunable.
 349
 350 config ARCH_SUPPORTS_MEMORY_FAILURE
 351         bool
 352
 353 config MEMORY_FAILURE
 354         depends on MMU
 355         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 356         bool "Enable recovery from hardware memory errors"
 357         select MEMORY_ISOLATION
 358         select RAS
 359         help
 360           Enables code to recover from some memory failures on systems
 361           with MCA recovery. This allows a system to continue running
 362           even when some of its memory has uncorrected errors. This requires
 363           special hardware support and typically ECC memory.
 364
 365 config HWPOISON_INJECT
 366         tristate "HWPoison pages injector"
 367         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 368         select PROC_PAGE_MONITOR
 369
 370 config NOMMU_INITIAL_TRIM_EXCESS
 371         int "Turn on mmap() excess space trimming before booting"
 372         depends on !MMU
 373         default 1
 374         help
 375           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 376           of memory on which to store mappings, but it can only ask the system
 377           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 378           more than it requires.  To deal with this, mmap() is able to trim off
 379           the excess and return it to the allocator.
 380
 381           If trimming is enabled, the excess is trimmed off and returned to the
 382           system allocator, which can cause extra fragmentation, particularly
 383           if there are a lot of transient processes.
 384
 385           If trimming is disabled, the excess is kept, but not used, which for
 386           long-term mappings means that the space is wasted.
 387
 388           Trimming can be dynamically controlled through a sysctl option
 389           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 390           excess pages there must be before trimming should occur, or zero if
 391           no trimming is to occur.
 392
 393           This option specifies the initial value of this option.  The default
 394           of 1 says that all excess pages should be trimmed.
 395
 396           See Documentation/nommu-mmap.txt for more information.
 397
 398 config TRANSPARENT_HUGEPAGE
 399         bool "Transparent Hugepage Support"
 400         depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
 401         select COMPACTION
 402         select RADIX_TREE_MULTIORDER
 403         help
 404           Transparent Hugepages allows the kernel to use huge pages and
 405           huge tlb transparently to the applications whenever possible.
 406           This feature can improve computing performance to certain
 407           applications by speeding up page faults during memory
 408           allocation, by reducing the number of tlb misses and by speeding
 409           up the pagetable walking.
 410
 411           If memory constrained on embedded, you may want to say N.
 412
 413 choice
 414         prompt "Transparent Hugepage Support sysfs defaults"
 415         depends on TRANSPARENT_HUGEPAGE
 416         default TRANSPARENT_HUGEPAGE_ALWAYS
 417         help
 418           Selects the sysfs defaults for Transparent Hugepage Support.
 419
 420         config TRANSPARENT_HUGEPAGE_ALWAYS
 421                 bool "always"
 422         help
 423           Enabling Transparent Hugepage always, can increase the
 424           memory footprint of applications without a guaranteed
 425           benefit but it will work automatically for all applications.
 426
 427         config TRANSPARENT_HUGEPAGE_MADVISE
 428                 bool "madvise"
 429         help
 430           Enabling Transparent Hugepage madvise, will only provide a
 431           performance improvement benefit to the applications using
 432           madvise(MADV_HUGEPAGE) but it won't risk to increase the
 433           memory footprint of applications without a guaranteed
 434           benefit.
 435 endchoice
 436
 437 config ARCH_WANTS_THP_SWAP
 438        def_bool n
 439
 440 config THP_SWAP
 441         def_bool y
 442         depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP
 443         help
 444           Swap transparent huge pages in one piece, without splitting.
 445           XXX: For now this only does clustered swap space allocation.
 446
 447           For selection by architectures with reasonable THP sizes.
 448
 449 config  TRANSPARENT_HUGE_PAGECACHE
 450         def_bool y
 451         depends on TRANSPARENT_HUGEPAGE
 452
 453 #
 454 # UP and nommu archs use km based percpu allocator
 455 #
 456 config NEED_PER_CPU_KM
 457         depends on !SMP
 458         bool
 459         default y
 460
 461 config CLEANCACHE
 462         bool "Enable cleancache driver to cache clean pages if tmem is present"
 463         default n
 464         help
 465           Cleancache can be thought of as a page-granularity victim cache
 466           for clean pages that the kernel's pageframe replacement algorithm
 467           (PFRA) would like to keep around, but can't since there isn't enough
 468           memory.  So when the PFRA "evicts" a page, it first attempts to use
 469           cleancache code to put the data contained in that page into
 470           "transcendent memory", memory that is not directly accessible or
 471           addressable by the kernel and is of unknown and possibly
 472           time-varying size.  And when a cleancache-enabled
 473           filesystem wishes to access a page in a file on disk, it first
 474           checks cleancache to see if it already contains it; if it does,
 475           the page is copied into the kernel and a disk access is avoided.
 476           When a transcendent memory driver is available (such as zcache or
 477           Xen transcendent memory), a significant I/O reduction
 478           may be achieved.  When none is available, all cleancache calls
 479           are reduced to a single pointer-compare-against-NULL resulting
 480           in a negligible performance hit.
 481
 482           If unsure, say Y to enable cleancache
 483
 484 config FRONTSWAP
 485         bool "Enable frontswap to cache swap pages if tmem is present"
 486         depends on SWAP
 487         default n
 488         help
 489           Frontswap is so named because it can be thought of as the opposite
 490           of a "backing" store for a swap device.  The data is stored into
 491           "transcendent memory", memory that is not directly accessible or
 492           addressable by the kernel and is of unknown and possibly
 493           time-varying size.  When space in transcendent memory is available,
 494           a significant swap I/O reduction may be achieved.  When none is
 495           available, all frontswap calls are reduced to a single pointer-
 496           compare-against-NULL resulting in a negligible performance hit
 497           and swap data is stored as normal on the matching swap device.
 498
 499           If unsure, say Y to enable frontswap.
 500
 501 config CMA
 502         bool "Contiguous Memory Allocator"
 503         depends on HAVE_MEMBLOCK && MMU
 504         select MIGRATION
 505         select MEMORY_ISOLATION
 506         help
 507           This enables the Contiguous Memory Allocator which allows other
 508           subsystems to allocate big physically-contiguous blocks of memory.
 509           CMA reserves a region of memory and allows only movable pages to
 510           be allocated from it. This way, the kernel can use the memory for
 511           pagecache and when a subsystem requests for contiguous area, the
 512           allocated pages are migrated away to serve the contiguous request.
 513
 514           If unsure, say "n".
 515
 516 config CMA_DEBUG
 517         bool "CMA debug messages (DEVELOPMENT)"
 518         depends on DEBUG_KERNEL && CMA
 519         help
 520           Turns on debug messages in CMA.  This produces KERN_DEBUG
 521           messages for every CMA call as well as various messages while
 522           processing calls such as dma_alloc_from_contiguous().
 523           This option does not affect warning and error messages.
 524
 525 config CMA_DEBUGFS
 526         bool "CMA debugfs interface"
 527         depends on CMA && DEBUG_FS
 528         help
 529           Turns on the DebugFS interface for CMA.
 530
 531 config CMA_AREAS
 532         int "Maximum count of the CMA areas"
 533         depends on CMA
 534         default 7
 535         help
 536           CMA allows to create CMA areas for particular purpose, mainly,
 537           used as device private area. This parameter sets the maximum
 538           number of CMA area in the system.
 539
 540           If unsure, leave the default value "7".
 541
 542 config MEM_SOFT_DIRTY
 543         bool "Track memory changes"
 544         depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
 545         select PROC_PAGE_MONITOR
 546         help
 547           This option enables memory changes tracking by introducing a
 548           soft-dirty bit on pte-s. This bit it set when someone writes
 549           into a page just as regular dirty bit, but unlike the latter
 550           it can be cleared by hands.
 551
 552           See Documentation/vm/soft-dirty.txt for more details.
 553
 554 config ZSWAP
 555         bool "Compressed cache for swap pages (EXPERIMENTAL)"
 556         depends on FRONTSWAP && CRYPTO=y
 557         select CRYPTO_LZO
 558         select ZPOOL
 559         default n
 560         help
 561           A lightweight compressed cache for swap pages.  It takes
 562           pages that are in the process of being swapped out and attempts to
 563           compress them into a dynamically allocated RAM-based memory pool.
 564           This can result in a significant I/O reduction on swap device and,
 565           in the case where decompressing from RAM is faster that swap device
 566           reads, can also improve workload performance.
 567
 568           This is marked experimental because it is a new feature (as of
 569           v3.11) that interacts heavily with memory reclaim.  While these
 570           interactions don't cause any known issues on simple memory setups,
 571           they have not be fully explored on the large set of potential
 572           configurations and workloads that exist.
 573
 574 config ZPOOL
 575         tristate "Common API for compressed memory storage"
 576         default n
 577         help
 578           Compressed memory storage API.  This allows using either zbud or
 579           zsmalloc.
 580
 581 config ZBUD
 582         tristate "Low (Up to 2x) density storage for compressed pages"
 583         default n
 584         help
 585           A special purpose allocator for storing compressed pages.
 586           It is designed to store up to two compressed pages per physical
 587           page.  While this design limits storage density, it has simple and
 588           deterministic reclaim properties that make it preferable to a higher
 589           density approach when reclaim will be used.
 590
 591 config Z3FOLD
 592         tristate "Up to 3x density storage for compressed pages"
 593         depends on ZPOOL
 594         default n
 595         help
 596           A special purpose allocator for storing compressed pages.
 597           It is designed to store up to three compressed pages per physical
 598           page. It is a ZBUD derivative so the simplicity and determinism are
 599           still there.
 600
 601 config ZSMALLOC
 602         tristate "Memory allocator for compressed pages"
 603         depends on MMU
 604         default n
 605         help
 606           zsmalloc is a slab-based memory allocator designed to store
 607           compressed RAM pages.  zsmalloc uses virtual memory mapping
 608           in order to reduce fragmentation.  However, this results in a
 609           non-standard allocator interface where a handle, not a pointer, is
 610           returned by an alloc().  This handle must be mapped in order to
 611           access the allocated space.
 612
 613 config PGTABLE_MAPPING
 614         bool "Use page table mapping to access object in zsmalloc"
 615         depends on ZSMALLOC
 616         help
 617           By default, zsmalloc uses a copy-based object mapping method to
 618           access allocations that span two pages. However, if a particular
 619           architecture (ex, ARM) performs VM mapping faster than copying,
 620           then you should select this. This causes zsmalloc to use page table
 621           mapping rather than copying for object mapping.
 622
 623           You can check speed with zsmalloc benchmark:
 624           https://github.com/spartacus06/zsmapbench
 625
 626 config ZSMALLOC_STAT
 627         bool "Export zsmalloc statistics"
 628         depends on ZSMALLOC
 629         select DEBUG_FS
 630         help
 631           This option enables code in the zsmalloc to collect various
 632           statistics about whats happening in zsmalloc and exports that
 633           information to userspace via debugfs.
 634           If unsure, say N.
 635
 636 config MM_EVENT_STAT
 637         bool "Track per-process MM event"
 638         depends on MMU
 639         help
 640           This option enables per-process mm event stat(e.g., fault, reclaim,
 641           compaction and so on ) with some interval(Default is 0.5sec).
 642           Admin can see the stat from trace file via debugfs(e.g.,
 643           /sys/kernel/debug/tracing/trace)
 644
 645           It includes max/average memory allocation latency for the interval
 646           as well as event count so that admin can see what happens in VM side
 647           (how many each event happens and how much processes spent time for
 648           the MM event). If it's too large, that would be not good situation.
 649
 650           System can dump the trace into bugreport when user allows the dump.
 651
 652 config GENERIC_EARLY_IOREMAP
 653         bool
 654
 655 config MAX_STACK_SIZE_MB
 656         int "Maximum user stack size for 32-bit processes (MB)"
 657         default 80
 658         range 8 256 if METAG
 659         range 8 2048
 660         depends on STACK_GROWSUP && (!64BIT || COMPAT)
 661         help
 662           This is the maximum stack size in Megabytes in the VM layout of 32-bit
 663           user processes when the stack grows upwards (currently only on parisc
 664           and metag arch). The stack will be located at the highest memory
 665           address minus the given value, unless the RLIMIT_STACK hard limit is
 666           changed to a smaller value in which case that is used.
 667
 668           A sane initial value is 80 MB.
 669
 670 config BALANCE_ANON_FILE_RECLAIM
 671         bool "During reclaim treat anon and file backed pages equally"
 672         depends on SWAP
 673         help
 674           When performing memory reclaim treat anonymous and file backed pages
 675           equally.
 676           Swapping anonymous pages out to memory can be efficient enough to justify
 677           treating anonymous and file backed pages equally.
 678
 679 config HPA
 680         bool "High-order Pages Allocator"
 681         select CMA
 682         help
 683           Turns on High-order Pages Allocator based on page migration.
 684
 685 # For architectures that support deferred memory initialisation
 686 config ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
 687         bool
 688
 689 config DEFERRED_STRUCT_PAGE_INIT
 690         bool "Defer initialisation of struct pages to kthreads"
 691         default n
 692         depends on ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
 693         depends on NO_BOOTMEM && MEMORY_HOTPLUG
 694         depends on !FLATMEM
 695         depends on !NEED_PER_CPU_KM
 696         help
 697           Ordinarily all struct pages are initialised during early boot in a
 698           single thread. On very large machines this can take a considerable
 699           amount of time. If this option is set, large machines will bring up
 700           a subset of memmap at boot and then initialise the rest in parallel
 701           by starting one-off "pgdatinitX" kernel thread for each node X. This
 702           has a potential performance impact on processes running early in the
 703           lifetime of the system until these kthreads finish the
 704           initialisation.
 705
 706 config IDLE_PAGE_TRACKING
 707         bool "Enable idle page tracking"
 708         depends on SYSFS && MMU
 709         select PAGE_EXTENSION if !64BIT
 710         help
 711           This feature allows to estimate the amount of user pages that have
 712           not been touched during a given period of time. This information can
 713           be useful to tune memory cgroup limits and/or for job placement
 714           within a compute cluster.
 715
 716           See Documentation/vm/idle_page_tracking.txt for more details.
 717
 718 # arch_add_memory() comprehends device memory
 719 config ARCH_HAS_ZONE_DEVICE
 720         bool
 721
 722 config ZONE_DEVICE
 723         bool "Device memory (pmem, HMM, etc...) hotplug support"
 724         depends on MEMORY_HOTPLUG
 725         depends on MEMORY_HOTREMOVE
 726         depends on SPARSEMEM_VMEMMAP
 727         depends on ARCH_HAS_ZONE_DEVICE
 728         select RADIX_TREE_MULTIORDER
 729
 730         help
 731           Device memory hotplug support allows for establishing pmem,
 732           or other device driver discovered memory regions, in the
 733           memmap. This allows pfn_to_page() lookups of otherwise
 734           "device-physical" addresses which is needed for using a DAX
 735           mapping in an O_DIRECT operation, among other things.
 736
 737           If FS_DAX is enabled, then say Y.
 738
 739 config ARCH_HAS_HMM
 740         bool
 741         default y
 742         depends on (X86_64 || PPC64)
 743         depends on ZONE_DEVICE
 744         depends on MMU && 64BIT
 745         depends on MEMORY_HOTPLUG
 746         depends on MEMORY_HOTREMOVE
 747         depends on SPARSEMEM_VMEMMAP
 748
 749 config MIGRATE_VMA_HELPER
 750         bool
 751
 752 config HMM
 753         bool
 754         select MIGRATE_VMA_HELPER
 755
 756 config HMM_MIRROR
 757         bool "HMM mirror CPU page table into a device page table"
 758         depends on ARCH_HAS_HMM
 759         select MMU_NOTIFIER
 760         select HMM
 761         help
 762           Select HMM_MIRROR if you want to mirror range of the CPU page table of a
 763           process into a device page table. Here, mirror means "keep synchronized".
 764           Prerequisites: the device must provide the ability to write-protect its
 765           page tables (at PAGE_SIZE granularity), and must be able to recover from
 766           the resulting potential page faults.
 767
 768 config DEVICE_PRIVATE
 769         bool "Unaddressable device memory (GPU memory, ...)"
 770         depends on ARCH_HAS_HMM
 771         select HMM
 772
 773         help
 774           Allows creation of struct pages to represent unaddressable device
 775           memory; i.e., memory that is only accessible from the device (or
 776           group of devices). You likely also want to select HMM_MIRROR.
 777
 778 config DEVICE_PUBLIC
 779         bool "Addressable device memory (like GPU memory)"
 780         depends on ARCH_HAS_HMM
 781         select HMM
 782
 783         help
 784           Allows creation of struct pages to represent addressable device
 785           memory; i.e., memory that is accessible from both the device and
 786           the CPU
 787
 788 config FRAME_VECTOR
 789         bool
 790
 791 config ARCH_USES_HIGH_VMA_FLAGS
 792         bool
 793 config ARCH_HAS_PKEYS
 794         bool
 795
 796 config PERCPU_STATS
 797         bool "Collect percpu memory statistics"
 798         default n
 799         help
 800           This feature collects and exposes statistics via debugfs. The
 801           information includes global and per chunk statistics, which can
 802           be used to help understand percpu memory usage.