mm/Kconfig

   1 # SPDX-License-Identifier: GPL-2.0-only
   2
   3 menu "Memory Management options"
   4
   5 config SELECT_MEMORY_MODEL
   6         def_bool y
   7         depends on ARCH_SELECT_MEMORY_MODEL
   8
   9 choice
  10         prompt "Memory model"
  11         depends on SELECT_MEMORY_MODEL
  12         default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
  13         default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
  14         default FLATMEM_MANUAL
  15         help
  16           This option allows you to change some of the ways that
  17           Linux manages its memory internally. Most users will
  18           only have one option here selected by the architecture
  19           configuration. This is normal.
  20
  21 config FLATMEM_MANUAL
  22         bool "Flat Memory"
  23         depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
  24         help
  25           This option is best suited for non-NUMA systems with
  26           flat address space. The FLATMEM is the most efficient
  27           system in terms of performance and resource consumption
  28           and it is the best option for smaller systems.
  29
  30           For systems that have holes in their physical address
  31           spaces and for features like NUMA and memory hotplug,
  32           choose "Sparse Memory".
  33
  34           If unsure, choose this option (Flat Memory) over any other.
  35
  36 config DISCONTIGMEM_MANUAL
  37         bool "Discontiguous Memory"
  38         depends on ARCH_DISCONTIGMEM_ENABLE
  39         help
  40           This option provides enhanced support for discontiguous
  41           memory systems, over FLATMEM.  These systems have holes
  42           in their physical address spaces, and this option provides
  43           more efficient handling of these holes.
  44
  45           Although "Discontiguous Memory" is still used by several
  46           architectures, it is considered deprecated in favor of
  47           "Sparse Memory".
  48
  49           If unsure, choose "Sparse Memory" over this option.
  50
  51 config SPARSEMEM_MANUAL
  52         bool "Sparse Memory"
  53         depends on ARCH_SPARSEMEM_ENABLE
  54         help
  55           This will be the only option for some systems, including
  56           memory hot-plug systems.  This is normal.
  57
  58           This option provides efficient support for systems with
  59           holes is their physical address space and allows memory
  60           hot-plug and hot-remove.
  61
  62           If unsure, choose "Flat Memory" over this option.
  63
  64 endchoice
  65
  66 config DISCONTIGMEM
  67         def_bool y
  68         depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
  69
  70 config SPARSEMEM
  71         def_bool y
  72         depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
  73
  74 config FLATMEM
  75         def_bool y
  76         depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
  77
  78 config FLAT_NODE_MEM_MAP
  79         def_bool y
  80         depends on !SPARSEMEM
  81
  82 #
  83 # Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
  84 # to represent different areas of memory.  This variable allows
  85 # those dependencies to exist individually.
  86 #
  87 config NEED_MULTIPLE_NODES
  88         def_bool y
  89         depends on DISCONTIGMEM || NUMA
  90
  91 config HAVE_MEMORY_PRESENT
  92         def_bool y
  93         depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
  94
  95 #
  96 # SPARSEMEM_EXTREME (which is the default) does some bootmem
  97 # allocations when memory_present() is called.  If this cannot
  98 # be done on your architecture, select this option.  However,
  99 # statically allocating the mem_section[] array can potentially
 100 # consume vast quantities of .bss, so be careful.
 101 #
 102 # This option will also potentially produce smaller runtime code
 103 # with gcc 3.4 and later.
 104 #
 105 config SPARSEMEM_STATIC
 106         bool
 107
 108 #
 109 # Architecture platforms which require a two level mem_section in SPARSEMEM
 110 # must select this option. This is usually for architecture platforms with
 111 # an extremely sparse physical address space.
 112 #
 113 config SPARSEMEM_EXTREME
 114         def_bool y
 115         depends on SPARSEMEM && !SPARSEMEM_STATIC
 116
 117 config SPARSEMEM_VMEMMAP_ENABLE
 118         bool
 119
 120 config SPARSEMEM_VMEMMAP
 121         bool "Sparse Memory virtual memmap"
 122         depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
 123         default y
 124         help
 125           SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
 126           pfn_to_page and page_to_pfn operations.  This is the most
 127           efficient option when sufficient kernel resources are available.
 128
 129 config HAVE_MEMBLOCK_NODE_MAP
 130         bool
 131
 132 config HAVE_MEMBLOCK_PHYS_MAP
 133         bool
 134
 135 config HAVE_FAST_GUP
 136         depends on MMU
 137         bool
 138
 139 config ARCH_KEEP_MEMBLOCK
 140         bool
 141
 142 # Keep arch NUMA mapping infrastructure post-init.
 143 config NUMA_KEEP_MEMINFO
 144         bool
 145
 146 config MEMORY_ISOLATION
 147         bool
 148
 149 #
 150 # Only be set on architectures that have completely implemented memory hotplug
 151 # feature. If you are not sure, don't touch it.
 152 #
 153 config HAVE_BOOTMEM_INFO_NODE
 154         def_bool n
 155
 156 # eventually, we can have this option just 'select SPARSEMEM'
 157 config MEMORY_HOTPLUG
 158         bool "Allow for memory hot-add"
 159         depends on SPARSEMEM || X86_64_ACPI_NUMA
 160         depends on ARCH_ENABLE_MEMORY_HOTPLUG
 161         select NUMA_KEEP_MEMINFO if NUMA
 162
 163 config MEMORY_HOTPLUG_SPARSE
 164         def_bool y
 165         depends on SPARSEMEM && MEMORY_HOTPLUG
 166
 167 config MEMORY_HOTPLUG_DEFAULT_ONLINE
 168         bool "Online the newly added memory blocks by default"
 169         depends on MEMORY_HOTPLUG
 170         help
 171           This option sets the default policy setting for memory hotplug
 172           onlining policy (/sys/devices/system/memory/auto_online_blocks) which
 173           determines what happens to newly added memory regions. Policy setting
 174           can always be changed at runtime.
 175           See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
 176
 177           Say Y here if you want all hot-plugged memory blocks to appear in
 178           'online' state by default.
 179           Say N here if you want the default policy to keep all hot-plugged
 180           memory blocks in 'offline' state.
 181
 182 config MEMORY_HOTREMOVE
 183         bool "Allow for memory hot remove"
 184         select MEMORY_ISOLATION
 185         select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
 186         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 187         depends on MIGRATION
 188
 189 # Heavily threaded applications may benefit from splitting the mm-wide
 190 # page_table_lock, so that faults on different parts of the user address
 191 # space can be handled with less contention: split it at this NR_CPUS.
 192 # Default to 4 for wider testing, though 8 might be more appropriate.
 193 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 194 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 195 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
 196 #
 197 config SPLIT_PTLOCK_CPUS
 198         int
 199         default "999999" if !MMU
 200         default "999999" if ARM && !CPU_CACHE_VIPT
 201         default "999999" if PARISC && !PA20
 202         default "4"
 203
 204 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
 205         bool
 206
 207 #
 208 # support for memory balloon
 209 config MEMORY_BALLOON
 210         bool
 211
 212 #
 213 # support for memory balloon compaction
 214 config BALLOON_COMPACTION
 215         bool "Allow for balloon memory compaction/migration"
 216         def_bool y
 217         depends on COMPACTION && MEMORY_BALLOON
 218         help
 219           Memory fragmentation introduced by ballooning might reduce
 220           significantly the number of 2MB contiguous memory blocks that can be
 221           used within a guest, thus imposing performance penalties associated
 222           with the reduced number of transparent huge pages that could be used
 223           by the guest workload. Allowing the compaction & migration for memory
 224           pages enlisted as being part of memory balloon devices avoids the
 225           scenario aforementioned and helps improving memory defragmentation.
 226
 227 #
 228 # support for memory compaction
 229 config COMPACTION
 230         bool "Allow for memory compaction"
 231         def_bool y
 232         select MIGRATION
 233         depends on MMU
 234         help
 235           Compaction is the only memory management component to form
 236           high order (larger physically contiguous) memory blocks
 237           reliably. The page allocator relies on compaction heavily and
 238           the lack of the feature can lead to unexpected OOM killer
 239           invocations for high order memory requests. You shouldn't
 240           disable this option unless there really is a strong reason for
 241           it and then we would be really interested to hear about that at
 242           linux-mm@kvack.org.
 243
 244 #
 245 # support for free page reporting
 246 config PAGE_REPORTING
 247         bool "Free page reporting"
 248         def_bool n
 249         help
 250           Free page reporting allows for the incremental acquisition of
 251           free pages from the buddy allocator for the purpose of reporting
 252           those pages to another entity, such as a hypervisor, so that the
 253           memory can be freed within the host for other uses.
 254
 255 #
 256 # support for page migration
 257 #
 258 config MIGRATION
 259         bool "Page migration"
 260         def_bool y
 261         depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
 262         help
 263           Allows the migration of the physical location of pages of processes
 264           while the virtual addresses are not changed. This is useful in
 265           two situations. The first is on NUMA systems to put pages nearer
 266           to the processors accessing. The second is when allocating huge
 267           pages as migration can relocate pages to satisfy a huge page
 268           allocation instead of reclaiming.
 269
 270 config ARCH_ENABLE_HUGEPAGE_MIGRATION
 271         bool
 272
 273 config ARCH_ENABLE_THP_MIGRATION
 274         bool
 275
 276 config CONTIG_ALLOC
 277         def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
 278
 279 config PHYS_ADDR_T_64BIT
 280         def_bool 64BIT
 281
 282 config BOUNCE
 283         bool "Enable bounce buffers"
 284         default y
 285         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 286         help
 287           Enable bounce buffers for devices that cannot access
 288           the full range of memory available to the CPU. Enabled
 289           by default when ZONE_DMA or HIGHMEM is selected, but you
 290           may say n to override this.
 291
 292 config VIRT_TO_BUS
 293         bool
 294         help
 295           An architecture should select this if it implements the
 296           deprecated interface virt_to_bus().  All new architectures
 297           should probably not select this.
 298
 299
 300 config MMU_NOTIFIER
 301         bool
 302         select SRCU
 303         select INTERVAL_TREE
 304
 305 config KSM
 306         bool "Enable KSM for page merging"
 307         depends on MMU
 308         select XXHASH
 309         help
 310           Enable Kernel Samepage Merging: KSM periodically scans those areas
 311           of an application's address space that an app has advised may be
 312           mergeable.  When it finds pages of identical content, it replaces
 313           the many instances by a single page with that content, so
 314           saving memory until one or another app needs to modify the content.
 315           Recommended for use with KVM, or with other duplicative applications.
 316           See Documentation/vm/ksm.rst for more information: KSM is inactive
 317           until a program has madvised that an area is MADV_MERGEABLE, and
 318           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 319
 320 config DEFAULT_MMAP_MIN_ADDR
 321         int "Low address space to protect from user allocation"
 322         depends on MMU
 323         default 4096
 324         help
 325           This is the portion of low virtual memory which should be protected
 326           from userspace allocation.  Keeping a user from writing to low pages
 327           can help reduce the impact of kernel NULL pointer bugs.
 328
 329           For most ia64, ppc64 and x86 users with lots of address space
 330           a value of 65536 is reasonable and should cause no problems.
 331           On arm and other archs it should not be higher than 32768.
 332           Programs which use vm86 functionality or have some need to map
 333           this low address space will need CAP_SYS_RAWIO or disable this
 334           protection by setting the value to 0.
 335
 336           This value can be changed after boot using the
 337           /proc/sys/vm/mmap_min_addr tunable.
 338
 339 config ARCH_SUPPORTS_MEMORY_FAILURE
 340         bool
 341
 342 config MEMORY_FAILURE
 343         depends on MMU
 344         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 345         bool "Enable recovery from hardware memory errors"
 346         select MEMORY_ISOLATION
 347         select RAS
 348         help
 349           Enables code to recover from some memory failures on systems
 350           with MCA recovery. This allows a system to continue running
 351           even when some of its memory has uncorrected errors. This requires
 352           special hardware support and typically ECC memory.
 353
 354 config HWPOISON_INJECT
 355         tristate "HWPoison pages injector"
 356         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 357         select PROC_PAGE_MONITOR
 358
 359 config NOMMU_INITIAL_TRIM_EXCESS
 360         int "Turn on mmap() excess space trimming before booting"
 361         depends on !MMU
 362         default 1
 363         help
 364           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 365           of memory on which to store mappings, but it can only ask the system
 366           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 367           more than it requires.  To deal with this, mmap() is able to trim off
 368           the excess and return it to the allocator.
 369
 370           If trimming is enabled, the excess is trimmed off and returned to the
 371           system allocator, which can cause extra fragmentation, particularly
 372           if there are a lot of transient processes.
 373
 374           If trimming is disabled, the excess is kept, but not used, which for
 375           long-term mappings means that the space is wasted.
 376
 377           Trimming can be dynamically controlled through a sysctl option
 378           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 379           excess pages there must be before trimming should occur, or zero if
 380           no trimming is to occur.
 381
 382           This option specifies the initial value of this option.  The default
 383           of 1 says that all excess pages should be trimmed.
 384
 385           See Documentation/nommu-mmap.txt for more information.
 386
 387 config TRANSPARENT_HUGEPAGE
 388         bool "Transparent Hugepage Support"
 389         depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
 390         select COMPACTION
 391         select XARRAY_MULTI
 392         help
 393           Transparent Hugepages allows the kernel to use huge pages and
 394           huge tlb transparently to the applications whenever possible.
 395           This feature can improve computing performance to certain
 396           applications by speeding up page faults during memory
 397           allocation, by reducing the number of tlb misses and by speeding
 398           up the pagetable walking.
 399
 400           If memory constrained on embedded, you may want to say N.
 401
 402 choice
 403         prompt "Transparent Hugepage Support sysfs defaults"
 404         depends on TRANSPARENT_HUGEPAGE
 405         default TRANSPARENT_HUGEPAGE_ALWAYS
 406         help
 407           Selects the sysfs defaults for Transparent Hugepage Support.
 408
 409         config TRANSPARENT_HUGEPAGE_ALWAYS
 410                 bool "always"
 411         help
 412           Enabling Transparent Hugepage always, can increase the
 413           memory footprint of applications without a guaranteed
 414           benefit but it will work automatically for all applications.
 415
 416         config TRANSPARENT_HUGEPAGE_MADVISE
 417                 bool "madvise"
 418         help
 419           Enabling Transparent Hugepage madvise, will only provide a
 420           performance improvement benefit to the applications using
 421           madvise(MADV_HUGEPAGE) but it won't risk to increase the
 422           memory footprint of applications without a guaranteed
 423           benefit.
 424 endchoice
 425
 426 config ARCH_WANTS_THP_SWAP
 427         def_bool n
 428
 429 config THP_SWAP
 430         def_bool y
 431         depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
 432         help
 433           Swap transparent huge pages in one piece, without splitting.
 434           XXX: For now, swap cluster backing transparent huge page
 435           will be split after swapout.
 436
 437           For selection by architectures with reasonable THP sizes.
 438
 439 #
 440 # UP and nommu archs use km based percpu allocator
 441 #
 442 config NEED_PER_CPU_KM
 443         depends on !SMP
 444         bool
 445         default y
 446
 447 config CLEANCACHE
 448         bool "Enable cleancache driver to cache clean pages if tmem is present"
 449         help
 450           Cleancache can be thought of as a page-granularity victim cache
 451           for clean pages that the kernel's pageframe replacement algorithm
 452           (PFRA) would like to keep around, but can't since there isn't enough
 453           memory.  So when the PFRA "evicts" a page, it first attempts to use
 454           cleancache code to put the data contained in that page into
 455           "transcendent memory", memory that is not directly accessible or
 456           addressable by the kernel and is of unknown and possibly
 457           time-varying size.  And when a cleancache-enabled
 458           filesystem wishes to access a page in a file on disk, it first
 459           checks cleancache to see if it already contains it; if it does,
 460           the page is copied into the kernel and a disk access is avoided.
 461           When a transcendent memory driver is available (such as zcache or
 462           Xen transcendent memory), a significant I/O reduction
 463           may be achieved.  When none is available, all cleancache calls
 464           are reduced to a single pointer-compare-against-NULL resulting
 465           in a negligible performance hit.
 466
 467           If unsure, say Y to enable cleancache
 468
 469 config FRONTSWAP
 470         bool "Enable frontswap to cache swap pages if tmem is present"
 471         depends on SWAP
 472         help
 473           Frontswap is so named because it can be thought of as the opposite
 474           of a "backing" store for a swap device.  The data is stored into
 475           "transcendent memory", memory that is not directly accessible or
 476           addressable by the kernel and is of unknown and possibly
 477           time-varying size.  When space in transcendent memory is available,
 478           a significant swap I/O reduction may be achieved.  When none is
 479           available, all frontswap calls are reduced to a single pointer-
 480           compare-against-NULL resulting in a negligible performance hit
 481           and swap data is stored as normal on the matching swap device.
 482
 483           If unsure, say Y to enable frontswap.
 484
 485 config CMA
 486         bool "Contiguous Memory Allocator"
 487         depends on MMU
 488         select MIGRATION
 489         select MEMORY_ISOLATION
 490         help
 491           This enables the Contiguous Memory Allocator which allows other
 492           subsystems to allocate big physically-contiguous blocks of memory.
 493           CMA reserves a region of memory and allows only movable pages to
 494           be allocated from it. This way, the kernel can use the memory for
 495           pagecache and when a subsystem requests for contiguous area, the
 496           allocated pages are migrated away to serve the contiguous request.
 497
 498           If unsure, say "n".
 499
 500 config CMA_DEBUG
 501         bool "CMA debug messages (DEVELOPMENT)"
 502         depends on DEBUG_KERNEL && CMA
 503         help
 504           Turns on debug messages in CMA.  This produces KERN_DEBUG
 505           messages for every CMA call as well as various messages while
 506           processing calls such as dma_alloc_from_contiguous().
 507           This option does not affect warning and error messages.
 508
 509 config CMA_DEBUGFS
 510         bool "CMA debugfs interface"
 511         depends on CMA && DEBUG_FS
 512         help
 513           Turns on the DebugFS interface for CMA.
 514
 515 config CMA_AREAS
 516         int "Maximum count of the CMA areas"
 517         depends on CMA
 518         default 7
 519         help
 520           CMA allows to create CMA areas for particular purpose, mainly,
 521           used as device private area. This parameter sets the maximum
 522           number of CMA area in the system.
 523
 524           If unsure, leave the default value "7".
 525
 526 config MEM_SOFT_DIRTY
 527         bool "Track memory changes"
 528         depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
 529         select PROC_PAGE_MONITOR
 530         help
 531           This option enables memory changes tracking by introducing a
 532           soft-dirty bit on pte-s. This bit it set when someone writes
 533           into a page just as regular dirty bit, but unlike the latter
 534           it can be cleared by hands.
 535
 536           See Documentation/admin-guide/mm/soft-dirty.rst for more details.
 537
 538 config ZSWAP
 539         bool "Compressed cache for swap pages (EXPERIMENTAL)"
 540         depends on FRONTSWAP && CRYPTO=y
 541         select ZPOOL
 542         help
 543           A lightweight compressed cache for swap pages.  It takes
 544           pages that are in the process of being swapped out and attempts to
 545           compress them into a dynamically allocated RAM-based memory pool.
 546           This can result in a significant I/O reduction on swap device and,
 547           in the case where decompressing from RAM is faster that swap device
 548           reads, can also improve workload performance.
 549
 550           This is marked experimental because it is a new feature (as of
 551           v3.11) that interacts heavily with memory reclaim.  While these
 552           interactions don't cause any known issues on simple memory setups,
 553           they have not be fully explored on the large set of potential
 554           configurations and workloads that exist.
 555
 556 choice
 557         prompt "Compressed cache for swap pages default compressor"
 558         depends on ZSWAP
 559         default ZSWAP_COMPRESSOR_DEFAULT_LZO
 560         help
 561           Selects the default compression algorithm for the compressed cache
 562           for swap pages.
 563
 564           For an overview what kind of performance can be expected from
 565           a particular compression algorithm please refer to the benchmarks
 566           available at the following LWN page:
 567           https://lwn.net/Articles/751795/
 568
 569           If in doubt, select 'LZO'.
 570
 571           The selection made here can be overridden by using the kernel
 572           command line 'zswap.compressor=' option.
 573
 574 config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
 575         bool "Deflate"
 576         select CRYPTO_DEFLATE
 577         help
 578           Use the Deflate algorithm as the default compression algorithm.
 579
 580 config ZSWAP_COMPRESSOR_DEFAULT_LZO
 581         bool "LZO"
 582         select CRYPTO_LZO
 583         help
 584           Use the LZO algorithm as the default compression algorithm.
 585
 586 config ZSWAP_COMPRESSOR_DEFAULT_842
 587         bool "842"
 588         select CRYPTO_842
 589         help
 590           Use the 842 algorithm as the default compression algorithm.
 591
 592 config ZSWAP_COMPRESSOR_DEFAULT_LZ4
 593         bool "LZ4"
 594         select CRYPTO_LZ4
 595         help
 596           Use the LZ4 algorithm as the default compression algorithm.
 597
 598 config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
 599         bool "LZ4HC"
 600         select CRYPTO_LZ4HC
 601         help
 602           Use the LZ4HC algorithm as the default compression algorithm.
 603
 604 config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
 605         bool "zstd"
 606         select CRYPTO_ZSTD
 607         help
 608           Use the zstd algorithm as the default compression algorithm.
 609 endchoice
 610
 611 config ZSWAP_COMPRESSOR_DEFAULT
 612        string
 613        depends on ZSWAP
 614        default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
 615        default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
 616        default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
 617        default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
 618        default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
 619        default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
 620        default ""
 621
 622 choice
 623         prompt "Compressed cache for swap pages default allocator"
 624         depends on ZSWAP
 625         default ZSWAP_ZPOOL_DEFAULT_ZBUD
 626         help
 627           Selects the default allocator for the compressed cache for
 628           swap pages.
 629           The default is 'zbud' for compatibility, however please do
 630           read the description of each of the allocators below before
 631           making a right choice.
 632
 633           The selection made here can be overridden by using the kernel
 634           command line 'zswap.zpool=' option.
 635
 636 config ZSWAP_ZPOOL_DEFAULT_ZBUD
 637         bool "zbud"
 638         select ZBUD
 639         help
 640           Use the zbud allocator as the default allocator.
 641
 642 config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
 643         bool "z3fold"
 644         select Z3FOLD
 645         help
 646           Use the z3fold allocator as the default allocator.
 647
 648 config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
 649         bool "zsmalloc"
 650         select ZSMALLOC
 651         help
 652           Use the zsmalloc allocator as the default allocator.
 653 endchoice
 654
 655 config ZSWAP_ZPOOL_DEFAULT
 656        string
 657        depends on ZSWAP
 658        default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
 659        default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
 660        default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
 661        default ""
 662
 663 config ZSWAP_DEFAULT_ON
 664         bool "Enable the compressed cache for swap pages by default"
 665         depends on ZSWAP
 666         help
 667           If selected, the compressed cache for swap pages will be enabled
 668           at boot, otherwise it will be disabled.
 669
 670           The selection made here can be overridden by using the kernel
 671           command line 'zswap.enabled=' option.
 672
 673 config ZPOOL
 674         tristate "Common API for compressed memory storage"
 675         help
 676           Compressed memory storage API.  This allows using either zbud or
 677           zsmalloc.
 678
 679 config ZBUD
 680         tristate "Low (Up to 2x) density storage for compressed pages"
 681         help
 682           A special purpose allocator for storing compressed pages.
 683           It is designed to store up to two compressed pages per physical
 684           page.  While this design limits storage density, it has simple and
 685           deterministic reclaim properties that make it preferable to a higher
 686           density approach when reclaim will be used.
 687
 688 config Z3FOLD
 689         tristate "Up to 3x density storage for compressed pages"
 690         depends on ZPOOL
 691         help
 692           A special purpose allocator for storing compressed pages.
 693           It is designed to store up to three compressed pages per physical
 694           page. It is a ZBUD derivative so the simplicity and determinism are
 695           still there.
 696
 697 config ZSMALLOC
 698         tristate "Memory allocator for compressed pages"
 699         depends on MMU
 700         help
 701           zsmalloc is a slab-based memory allocator designed to store
 702           compressed RAM pages.  zsmalloc uses virtual memory mapping
 703           in order to reduce fragmentation.  However, this results in a
 704           non-standard allocator interface where a handle, not a pointer, is
 705           returned by an alloc().  This handle must be mapped in order to
 706           access the allocated space.
 707
 708 config PGTABLE_MAPPING
 709         bool "Use page table mapping to access object in zsmalloc"
 710         depends on ZSMALLOC
 711         help
 712           By default, zsmalloc uses a copy-based object mapping method to
 713           access allocations that span two pages. However, if a particular
 714           architecture (ex, ARM) performs VM mapping faster than copying,
 715           then you should select this. This causes zsmalloc to use page table
 716           mapping rather than copying for object mapping.
 717
 718           You can check speed with zsmalloc benchmark:
 719           https://github.com/spartacus06/zsmapbench
 720
 721 config ZSMALLOC_STAT
 722         bool "Export zsmalloc statistics"
 723         depends on ZSMALLOC
 724         select DEBUG_FS
 725         help
 726           This option enables code in the zsmalloc to collect various
 727           statistics about whats happening in zsmalloc and exports that
 728           information to userspace via debugfs.
 729           If unsure, say N.
 730
 731 config GENERIC_EARLY_IOREMAP
 732         bool
 733
 734 config MAX_STACK_SIZE_MB
 735         int "Maximum user stack size for 32-bit processes (MB)"
 736         default 80
 737         range 8 2048
 738         depends on STACK_GROWSUP && (!64BIT || COMPAT)
 739         help
 740           This is the maximum stack size in Megabytes in the VM layout of 32-bit
 741           user processes when the stack grows upwards (currently only on parisc
 742           arch). The stack will be located at the highest memory address minus
 743           the given value, unless the RLIMIT_STACK hard limit is changed to a
 744           smaller value in which case that is used.
 745
 746           A sane initial value is 80 MB.
 747
 748 config DEFERRED_STRUCT_PAGE_INIT
 749         bool "Defer initialisation of struct pages to kthreads"
 750         depends on SPARSEMEM
 751         depends on !NEED_PER_CPU_KM
 752         depends on 64BIT
 753         help
 754           Ordinarily all struct pages are initialised during early boot in a
 755           single thread. On very large machines this can take a considerable
 756           amount of time. If this option is set, large machines will bring up
 757           a subset of memmap at boot and then initialise the rest in parallel
 758           by starting one-off "pgdatinitX" kernel thread for each node X. This
 759           has a potential performance impact on processes running early in the
 760           lifetime of the system until these kthreads finish the
 761           initialisation.
 762
 763 config IDLE_PAGE_TRACKING
 764         bool "Enable idle page tracking"
 765         depends on SYSFS && MMU
 766         select PAGE_EXTENSION if !64BIT
 767         help
 768           This feature allows to estimate the amount of user pages that have
 769           not been touched during a given period of time. This information can
 770           be useful to tune memory cgroup limits and/or for job placement
 771           within a compute cluster.
 772
 773           See Documentation/admin-guide/mm/idle_page_tracking.rst for
 774           more details.
 775
 776 config ARCH_HAS_PTE_DEVMAP
 777         bool
 778
 779 config ZONE_DEVICE
 780         bool "Device memory (pmem, HMM, etc...) hotplug support"
 781         depends on MEMORY_HOTPLUG
 782         depends on MEMORY_HOTREMOVE
 783         depends on SPARSEMEM_VMEMMAP
 784         depends on ARCH_HAS_PTE_DEVMAP
 785         select XARRAY_MULTI
 786
 787         help
 788           Device memory hotplug support allows for establishing pmem,
 789           or other device driver discovered memory regions, in the
 790           memmap. This allows pfn_to_page() lookups of otherwise
 791           "device-physical" addresses which is needed for using a DAX
 792           mapping in an O_DIRECT operation, among other things.
 793
 794           If FS_DAX is enabled, then say Y.
 795
 796 config DEV_PAGEMAP_OPS
 797         bool
 798
 799 #
 800 # Helpers to mirror range of the CPU page tables of a process into device page
 801 # tables.
 802 #
 803 config HMM_MIRROR
 804         bool
 805         depends on MMU
 806
 807 config DEVICE_PRIVATE
 808         bool "Unaddressable device memory (GPU memory, ...)"
 809         depends on ZONE_DEVICE
 810         select DEV_PAGEMAP_OPS
 811
 812         help
 813           Allows creation of struct pages to represent unaddressable device
 814           memory; i.e., memory that is only accessible from the device (or
 815           group of devices). You likely also want to select HMM_MIRROR.
 816
 817 config FRAME_VECTOR
 818         bool
 819
 820 config ARCH_USES_HIGH_VMA_FLAGS
 821         bool
 822 config ARCH_HAS_PKEYS
 823         bool
 824
 825 config PERCPU_STATS
 826         bool "Collect percpu memory statistics"
 827         help
 828           This feature collects and exposes statistics via debugfs. The
 829           information includes global and per chunk statistics, which can
 830           be used to help understand percpu memory usage.
 831
 832 config GUP_BENCHMARK
 833         bool "Enable infrastructure for get_user_pages_fast() benchmarking"
 834         help
 835           Provides /sys/kernel/debug/gup_benchmark that helps with testing
 836           performance of get_user_pages_fast().
 837
 838           See tools/testing/selftests/vm/gup_benchmark.c
 839
 840 config GUP_GET_PTE_LOW_HIGH
 841         bool
 842
 843 config READ_ONLY_THP_FOR_FS
 844         bool "Read-only THP for filesystems (EXPERIMENTAL)"
 845         depends on TRANSPARENT_HUGEPAGE && SHMEM
 846
 847         help
 848           Allow khugepaged to put read-only file-backed pages in THP.
 849
 850           This is marked experimental because it is a new feature. Write
 851           support of file THPs will be developed in the next few release
 852           cycles.
 853
 854 config ARCH_HAS_PTE_SPECIAL
 855         bool
 856
 857 #
 858 # Some architectures require a special hugepage directory format that is
 859 # required to support multiple hugepage sizes. For example a4fe3ce76
 860 # "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
 861 # introduced it on powerpc.  This allows for a more flexible hugepage
 862 # pagetable layouts.
 863 #
 864 config ARCH_HAS_HUGEPD
 865         bool
 866
 867 config MAPPING_DIRTY_HELPERS
 868         bool
 869
 870 endmenu