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 #
  92 # SPARSEMEM_EXTREME (which is the default) does some bootmem
  93 # allocations when sparse_init() is called.  If this cannot
  94 # be done on your architecture, select this option.  However,
  95 # statically allocating the mem_section[] array can potentially
  96 # consume vast quantities of .bss, so be careful.
  97 #
  98 # This option will also potentially produce smaller runtime code
  99 # with gcc 3.4 and later.
 100 #
 101 config SPARSEMEM_STATIC
 102         bool
 103
 104 #
 105 # Architecture platforms which require a two level mem_section in SPARSEMEM
 106 # must select this option. This is usually for architecture platforms with
 107 # an extremely sparse physical address space.
 108 #
 109 config SPARSEMEM_EXTREME
 110         def_bool y
 111         depends on SPARSEMEM && !SPARSEMEM_STATIC
 112
 113 config SPARSEMEM_VMEMMAP_ENABLE
 114         bool
 115
 116 config SPARSEMEM_VMEMMAP
 117         bool "Sparse Memory virtual memmap"
 118         depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
 119         default y
 120         help
 121           SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
 122           pfn_to_page and page_to_pfn operations.  This is the most
 123           efficient option when sufficient kernel resources are available.
 124
 125 config HAVE_MEMBLOCK_PHYS_MAP
 126         bool
 127
 128 config HAVE_FAST_GUP
 129         depends on MMU
 130         bool
 131
 132 # Don't discard allocated memory used to track "memory" and "reserved" memblocks
 133 # after early boot, so it can still be used to test for validity of memory.
 134 # Also, memblocks are updated with memory hot(un)plug.
 135 config ARCH_KEEP_MEMBLOCK
 136         bool
 137
 138 # Keep arch NUMA mapping infrastructure post-init.
 139 config NUMA_KEEP_MEMINFO
 140         bool
 141
 142 config MEMORY_ISOLATION
 143         bool
 144
 145 #
 146 # Only be set on architectures that have completely implemented memory hotplug
 147 # feature. If you are not sure, don't touch it.
 148 #
 149 config HAVE_BOOTMEM_INFO_NODE
 150         def_bool n
 151
 152 # eventually, we can have this option just 'select SPARSEMEM'
 153 config MEMORY_HOTPLUG
 154         bool "Allow for memory hot-add"
 155         select MEMORY_ISOLATION
 156         depends on SPARSEMEM || X86_64_ACPI_NUMA
 157         depends on ARCH_ENABLE_MEMORY_HOTPLUG
 158         depends on 64BIT || BROKEN
 159         select NUMA_KEEP_MEMINFO if NUMA
 160
 161 config MEMORY_HOTPLUG_SPARSE
 162         def_bool y
 163         depends on SPARSEMEM && MEMORY_HOTPLUG
 164
 165 config MEMORY_HOTPLUG_DEFAULT_ONLINE
 166         bool "Online the newly added memory blocks by default"
 167         depends on MEMORY_HOTPLUG
 168         help
 169           This option sets the default policy setting for memory hotplug
 170           onlining policy (/sys/devices/system/memory/auto_online_blocks) which
 171           determines what happens to newly added memory regions. Policy setting
 172           can always be changed at runtime.
 173           See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
 174
 175           Say Y here if you want all hot-plugged memory blocks to appear in
 176           'online' state by default.
 177           Say N here if you want the default policy to keep all hot-plugged
 178           memory blocks in 'offline' state.
 179
 180 config MEMORY_HOTREMOVE
 181         bool "Allow for memory hot remove"
 182         select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
 183         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 184         depends on MIGRATION
 185
 186 # Heavily threaded applications may benefit from splitting the mm-wide
 187 # page_table_lock, so that faults on different parts of the user address
 188 # space can be handled with less contention: split it at this NR_CPUS.
 189 # Default to 4 for wider testing, though 8 might be more appropriate.
 190 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 191 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 192 # SPARC32 allocates multiple pte tables within a single page, and therefore
 193 # a per-page lock leads to problems when multiple tables need to be locked
 194 # at the same time (e.g. copy_page_range()).
 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 "999999" if SPARC32
 203         default "4"
 204
 205 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
 206         bool
 207
 208 #
 209 # support for memory balloon
 210 config MEMORY_BALLOON
 211         bool
 212
 213 #
 214 # support for memory balloon compaction
 215 config BALLOON_COMPACTION
 216         bool "Allow for balloon memory compaction/migration"
 217         def_bool y
 218         depends on COMPACTION && MEMORY_BALLOON
 219         help
 220           Memory fragmentation introduced by ballooning might reduce
 221           significantly the number of 2MB contiguous memory blocks that can be
 222           used within a guest, thus imposing performance penalties associated
 223           with the reduced number of transparent huge pages that could be used
 224           by the guest workload. Allowing the compaction & migration for memory
 225           pages enlisted as being part of memory balloon devices avoids the
 226           scenario aforementioned and helps improving memory defragmentation.
 227
 228 #
 229 # support for memory compaction
 230 config COMPACTION
 231         bool "Allow for memory compaction"
 232         def_bool y
 233         select MIGRATION
 234         depends on MMU
 235         help
 236           Compaction is the only memory management component to form
 237           high order (larger physically contiguous) memory blocks
 238           reliably. The page allocator relies on compaction heavily and
 239           the lack of the feature can lead to unexpected OOM killer
 240           invocations for high order memory requests. You shouldn't
 241           disable this option unless there really is a strong reason for
 242           it and then we would be really interested to hear about that at
 243           linux-mm@kvack.org.
 244
 245 #
 246 # support for free page reporting
 247 config PAGE_REPORTING
 248         bool "Free page reporting"
 249         def_bool n
 250         help
 251           Free page reporting allows for the incremental acquisition of
 252           free pages from the buddy allocator for the purpose of reporting
 253           those pages to another entity, such as a hypervisor, so that the
 254           memory can be freed within the host for other uses.
 255
 256 #
 257 # support for page migration
 258 #
 259 config MIGRATION
 260         bool "Page migration"
 261         def_bool y
 262         depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
 263         help
 264           Allows the migration of the physical location of pages of processes
 265           while the virtual addresses are not changed. This is useful in
 266           two situations. The first is on NUMA systems to put pages nearer
 267           to the processors accessing. The second is when allocating huge
 268           pages as migration can relocate pages to satisfy a huge page
 269           allocation instead of reclaiming.
 270
 271 config ARCH_ENABLE_HUGEPAGE_MIGRATION
 272         bool
 273
 274 config ARCH_ENABLE_THP_MIGRATION
 275         bool
 276
 277 config CONTIG_ALLOC
 278         def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
 279
 280 config PHYS_ADDR_T_64BIT
 281         def_bool 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 config VIRT_TO_BUS
 294         bool
 295         help
 296           An architecture should select this if it implements the
 297           deprecated interface virt_to_bus().  All new architectures
 298           should probably not select this.
 299
 300
 301 config MMU_NOTIFIER
 302         bool
 303         select SRCU
 304         select INTERVAL_TREE
 305
 306 config KSM
 307         bool "Enable KSM for page merging"
 308         depends on MMU
 309         select XXHASH
 310         help
 311           Enable Kernel Samepage Merging: KSM periodically scans those areas
 312           of an application's address space that an app has advised may be
 313           mergeable.  When it finds pages of identical content, it replaces
 314           the many instances by a single page with that content, so
 315           saving memory until one or another app needs to modify the content.
 316           Recommended for use with KVM, or with other duplicative applications.
 317           See Documentation/vm/ksm.rst for more information: KSM is inactive
 318           until a program has madvised that an area is MADV_MERGEABLE, and
 319           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 320
 321 config DEFAULT_MMAP_MIN_ADDR
 322         int "Low address space to protect from user allocation"
 323         depends on MMU
 324         default 4096
 325         help
 326           This is the portion of low virtual memory which should be protected
 327           from userspace allocation.  Keeping a user from writing to low pages
 328           can help reduce the impact of kernel NULL pointer bugs.
 329
 330           For most ia64, ppc64 and x86 users with lots of address space
 331           a value of 65536 is reasonable and should cause no problems.
 332           On arm and other archs it should not be higher than 32768.
 333           Programs which use vm86 functionality or have some need to map
 334           this low address space will need CAP_SYS_RAWIO or disable this
 335           protection by setting the value to 0.
 336
 337           This value can be changed after boot using the
 338           /proc/sys/vm/mmap_min_addr tunable.
 339
 340 config ARCH_SUPPORTS_MEMORY_FAILURE
 341         bool
 342
 343 config MEMORY_FAILURE
 344         depends on MMU
 345         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 346         bool "Enable recovery from hardware memory errors"
 347         select MEMORY_ISOLATION
 348         select RAS
 349         help
 350           Enables code to recover from some memory failures on systems
 351           with MCA recovery. This allows a system to continue running
 352           even when some of its memory has uncorrected errors. This requires
 353           special hardware support and typically ECC memory.
 354
 355 config HWPOISON_INJECT
 356         tristate "HWPoison pages injector"
 357         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 358         select PROC_PAGE_MONITOR
 359
 360 config NOMMU_INITIAL_TRIM_EXCESS
 361         int "Turn on mmap() excess space trimming before booting"
 362         depends on !MMU
 363         default 1
 364         help
 365           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 366           of memory on which to store mappings, but it can only ask the system
 367           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 368           more than it requires.  To deal with this, mmap() is able to trim off
 369           the excess and return it to the allocator.
 370
 371           If trimming is enabled, the excess is trimmed off and returned to the
 372           system allocator, which can cause extra fragmentation, particularly
 373           if there are a lot of transient processes.
 374
 375           If trimming is disabled, the excess is kept, but not used, which for
 376           long-term mappings means that the space is wasted.
 377
 378           Trimming can be dynamically controlled through a sysctl option
 379           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 380           excess pages there must be before trimming should occur, or zero if
 381           no trimming is to occur.
 382
 383           This option specifies the initial value of this option.  The default
 384           of 1 says that all excess pages should be trimmed.
 385
 386           See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
 387
 388 config TRANSPARENT_HUGEPAGE
 389         bool "Transparent Hugepage Support"
 390         depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
 391         select COMPACTION
 392         select XARRAY_MULTI
 393         help
 394           Transparent Hugepages allows the kernel to use huge pages and
 395           huge tlb transparently to the applications whenever possible.
 396           This feature can improve computing performance to certain
 397           applications by speeding up page faults during memory
 398           allocation, by reducing the number of tlb misses and by speeding
 399           up the pagetable walking.
 400
 401           If memory constrained on embedded, you may want to say N.
 402
 403 choice
 404         prompt "Transparent Hugepage Support sysfs defaults"
 405         depends on TRANSPARENT_HUGEPAGE
 406         default TRANSPARENT_HUGEPAGE_ALWAYS
 407         help
 408           Selects the sysfs defaults for Transparent Hugepage Support.
 409
 410         config TRANSPARENT_HUGEPAGE_ALWAYS
 411                 bool "always"
 412         help
 413           Enabling Transparent Hugepage always, can increase the
 414           memory footprint of applications without a guaranteed
 415           benefit but it will work automatically for all applications.
 416
 417         config TRANSPARENT_HUGEPAGE_MADVISE
 418                 bool "madvise"
 419         help
 420           Enabling Transparent Hugepage madvise, will only provide a
 421           performance improvement benefit to the applications using
 422           madvise(MADV_HUGEPAGE) but it won't risk to increase the
 423           memory footprint of applications without a guaranteed
 424           benefit.
 425 endchoice
 426
 427 config ARCH_WANTS_THP_SWAP
 428         def_bool n
 429
 430 config THP_SWAP
 431         def_bool y
 432         depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
 433         help
 434           Swap transparent huge pages in one piece, without splitting.
 435           XXX: For now, swap cluster backing transparent huge page
 436           will be split after swapout.
 437
 438           For selection by architectures with reasonable THP sizes.
 439
 440 #
 441 # UP and nommu archs use km based percpu allocator
 442 #
 443 config NEED_PER_CPU_KM
 444         depends on !SMP
 445         bool
 446         default y
 447
 448 config CLEANCACHE
 449         bool "Enable cleancache driver to cache clean pages if tmem is present"
 450         help
 451           Cleancache can be thought of as a page-granularity victim cache
 452           for clean pages that the kernel's pageframe replacement algorithm
 453           (PFRA) would like to keep around, but can't since there isn't enough
 454           memory.  So when the PFRA "evicts" a page, it first attempts to use
 455           cleancache code to put the data contained in that page into
 456           "transcendent memory", memory that is not directly accessible or
 457           addressable by the kernel and is of unknown and possibly
 458           time-varying size.  And when a cleancache-enabled
 459           filesystem wishes to access a page in a file on disk, it first
 460           checks cleancache to see if it already contains it; if it does,
 461           the page is copied into the kernel and a disk access is avoided.
 462           When a transcendent memory driver is available (such as zcache or
 463           Xen transcendent memory), a significant I/O reduction
 464           may be achieved.  When none is available, all cleancache calls
 465           are reduced to a single pointer-compare-against-NULL resulting
 466           in a negligible performance hit.
 467
 468           If unsure, say Y to enable cleancache
 469
 470 config FRONTSWAP
 471         bool "Enable frontswap to cache swap pages if tmem is present"
 472         depends on SWAP
 473         help
 474           Frontswap is so named because it can be thought of as the opposite
 475           of a "backing" store for a swap device.  The data is stored into
 476           "transcendent memory", memory that is not directly accessible or
 477           addressable by the kernel and is of unknown and possibly
 478           time-varying size.  When space in transcendent memory is available,
 479           a significant swap I/O reduction may be achieved.  When none is
 480           available, all frontswap calls are reduced to a single pointer-
 481           compare-against-NULL resulting in a negligible performance hit
 482           and swap data is stored as normal on the matching swap device.
 483
 484           If unsure, say Y to enable frontswap.
 485
 486 config CMA
 487         bool "Contiguous Memory Allocator"
 488         depends on MMU
 489         select MIGRATION
 490         select MEMORY_ISOLATION
 491         help
 492           This enables the Contiguous Memory Allocator which allows other
 493           subsystems to allocate big physically-contiguous blocks of memory.
 494           CMA reserves a region of memory and allows only movable pages to
 495           be allocated from it. This way, the kernel can use the memory for
 496           pagecache and when a subsystem requests for contiguous area, the
 497           allocated pages are migrated away to serve the contiguous request.
 498
 499           If unsure, say "n".
 500
 501 config CMA_DEBUG
 502         bool "CMA debug messages (DEVELOPMENT)"
 503         depends on DEBUG_KERNEL && CMA
 504         help
 505           Turns on debug messages in CMA.  This produces KERN_DEBUG
 506           messages for every CMA call as well as various messages while
 507           processing calls such as dma_alloc_from_contiguous().
 508           This option does not affect warning and error messages.
 509
 510 config CMA_DEBUGFS
 511         bool "CMA debugfs interface"
 512         depends on CMA && DEBUG_FS
 513         help
 514           Turns on the DebugFS interface for CMA.
 515
 516 config CMA_AREAS
 517         int "Maximum count of the CMA areas"
 518         depends on CMA
 519         default 19 if NUMA
 520         default 7
 521         help
 522           CMA allows to create CMA areas for particular purpose, mainly,
 523           used as device private area. This parameter sets the maximum
 524           number of CMA area in the system.
 525
 526           If unsure, leave the default value "7" in UMA and "19" in NUMA.
 527
 528 config MEM_SOFT_DIRTY
 529         bool "Track memory changes"
 530         depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
 531         select PROC_PAGE_MONITOR
 532         help
 533           This option enables memory changes tracking by introducing a
 534           soft-dirty bit on pte-s. This bit it set when someone writes
 535           into a page just as regular dirty bit, but unlike the latter
 536           it can be cleared by hands.
 537
 538           See Documentation/admin-guide/mm/soft-dirty.rst for more details.
 539
 540 config ZSWAP
 541         bool "Compressed cache for swap pages (EXPERIMENTAL)"
 542         depends on FRONTSWAP && CRYPTO=y
 543         select ZPOOL
 544         help
 545           A lightweight compressed cache for swap pages.  It takes
 546           pages that are in the process of being swapped out and attempts to
 547           compress them into a dynamically allocated RAM-based memory pool.
 548           This can result in a significant I/O reduction on swap device and,
 549           in the case where decompressing from RAM is faster that swap device
 550           reads, can also improve workload performance.
 551
 552           This is marked experimental because it is a new feature (as of
 553           v3.11) that interacts heavily with memory reclaim.  While these
 554           interactions don't cause any known issues on simple memory setups,
 555           they have not be fully explored on the large set of potential
 556           configurations and workloads that exist.
 557
 558 choice
 559         prompt "Compressed cache for swap pages default compressor"
 560         depends on ZSWAP
 561         default ZSWAP_COMPRESSOR_DEFAULT_LZO
 562         help
 563           Selects the default compression algorithm for the compressed cache
 564           for swap pages.
 565
 566           For an overview what kind of performance can be expected from
 567           a particular compression algorithm please refer to the benchmarks
 568           available at the following LWN page:
 569           https://lwn.net/Articles/751795/
 570
 571           If in doubt, select 'LZO'.
 572
 573           The selection made here can be overridden by using the kernel
 574           command line 'zswap.compressor=' option.
 575
 576 config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
 577         bool "Deflate"
 578         select CRYPTO_DEFLATE
 579         help
 580           Use the Deflate algorithm as the default compression algorithm.
 581
 582 config ZSWAP_COMPRESSOR_DEFAULT_LZO
 583         bool "LZO"
 584         select CRYPTO_LZO
 585         help
 586           Use the LZO algorithm as the default compression algorithm.
 587
 588 config ZSWAP_COMPRESSOR_DEFAULT_842
 589         bool "842"
 590         select CRYPTO_842
 591         help
 592           Use the 842 algorithm as the default compression algorithm.
 593
 594 config ZSWAP_COMPRESSOR_DEFAULT_LZ4
 595         bool "LZ4"
 596         select CRYPTO_LZ4
 597         help
 598           Use the LZ4 algorithm as the default compression algorithm.
 599
 600 config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
 601         bool "LZ4HC"
 602         select CRYPTO_LZ4HC
 603         help
 604           Use the LZ4HC algorithm as the default compression algorithm.
 605
 606 config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
 607         bool "zstd"
 608         select CRYPTO_ZSTD
 609         help
 610           Use the zstd algorithm as the default compression algorithm.
 611 endchoice
 612
 613 config ZSWAP_COMPRESSOR_DEFAULT
 614        string
 615        depends on ZSWAP
 616        default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
 617        default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
 618        default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
 619        default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
 620        default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
 621        default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
 622        default ""
 623
 624 choice
 625         prompt "Compressed cache for swap pages default allocator"
 626         depends on ZSWAP
 627         default ZSWAP_ZPOOL_DEFAULT_ZBUD
 628         help
 629           Selects the default allocator for the compressed cache for
 630           swap pages.
 631           The default is 'zbud' for compatibility, however please do
 632           read the description of each of the allocators below before
 633           making a right choice.
 634
 635           The selection made here can be overridden by using the kernel
 636           command line 'zswap.zpool=' option.
 637
 638 config ZSWAP_ZPOOL_DEFAULT_ZBUD
 639         bool "zbud"
 640         select ZBUD
 641         help
 642           Use the zbud allocator as the default allocator.
 643
 644 config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
 645         bool "z3fold"
 646         select Z3FOLD
 647         help
 648           Use the z3fold allocator as the default allocator.
 649
 650 config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
 651         bool "zsmalloc"
 652         select ZSMALLOC
 653         help
 654           Use the zsmalloc allocator as the default allocator.
 655 endchoice
 656
 657 config ZSWAP_ZPOOL_DEFAULT
 658        string
 659        depends on ZSWAP
 660        default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
 661        default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
 662        default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
 663        default ""
 664
 665 config ZSWAP_DEFAULT_ON
 666         bool "Enable the compressed cache for swap pages by default"
 667         depends on ZSWAP
 668         help
 669           If selected, the compressed cache for swap pages will be enabled
 670           at boot, otherwise it will be disabled.
 671
 672           The selection made here can be overridden by using the kernel
 673           command line 'zswap.enabled=' option.
 674
 675 config ZPOOL
 676         tristate "Common API for compressed memory storage"
 677         help
 678           Compressed memory storage API.  This allows using either zbud or
 679           zsmalloc.
 680
 681 config ZBUD
 682         tristate "Low (Up to 2x) density storage for compressed pages"
 683         help
 684           A special purpose allocator for storing compressed pages.
 685           It is designed to store up to two compressed pages per physical
 686           page.  While this design limits storage density, it has simple and
 687           deterministic reclaim properties that make it preferable to a higher
 688           density approach when reclaim will be used.
 689
 690 config Z3FOLD
 691         tristate "Up to 3x density storage for compressed pages"
 692         depends on ZPOOL
 693         help
 694           A special purpose allocator for storing compressed pages.
 695           It is designed to store up to three compressed pages per physical
 696           page. It is a ZBUD derivative so the simplicity and determinism are
 697           still there.
 698
 699 config ZSMALLOC
 700         tristate "Memory allocator for compressed pages"
 701         depends on MMU
 702         help
 703           zsmalloc is a slab-based memory allocator designed to store
 704           compressed RAM pages.  zsmalloc uses virtual memory mapping
 705           in order to reduce fragmentation.  However, this results in a
 706           non-standard allocator interface where a handle, not a pointer, is
 707           returned by an alloc().  This handle must be mapped in order to
 708           access the allocated space.
 709
 710 config ZSMALLOC_STAT
 711         bool "Export zsmalloc statistics"
 712         depends on ZSMALLOC
 713         select DEBUG_FS
 714         help
 715           This option enables code in the zsmalloc to collect various
 716           statistics about what's happening in zsmalloc and exports that
 717           information to userspace via debugfs.
 718           If unsure, say N.
 719
 720 config GENERIC_EARLY_IOREMAP
 721         bool
 722
 723 config STACK_MAX_DEFAULT_SIZE_MB
 724         int "Default maximum user stack size for 32-bit processes (MB)"
 725         default 100
 726         range 8 2048
 727         depends on STACK_GROWSUP && (!64BIT || COMPAT)
 728         help
 729           This is the maximum stack size in Megabytes in the VM layout of 32-bit
 730           user processes when the stack grows upwards (currently only on parisc
 731           arch) when the RLIMIT_STACK hard limit is unlimited.
 732
 733           A sane initial value is 100 MB.
 734
 735 config DEFERRED_STRUCT_PAGE_INIT
 736         bool "Defer initialisation of struct pages to kthreads"
 737         depends on SPARSEMEM
 738         depends on !NEED_PER_CPU_KM
 739         depends on 64BIT
 740         select PADATA
 741         help
 742           Ordinarily all struct pages are initialised during early boot in a
 743           single thread. On very large machines this can take a considerable
 744           amount of time. If this option is set, large machines will bring up
 745           a subset of memmap at boot and then initialise the rest in parallel.
 746           This has a potential performance impact on tasks running early in the
 747           lifetime of the system until these kthreads finish the
 748           initialisation.
 749
 750 config IDLE_PAGE_TRACKING
 751         bool "Enable idle page tracking"
 752         depends on SYSFS && MMU
 753         select PAGE_EXTENSION if !64BIT
 754         help
 755           This feature allows to estimate the amount of user pages that have
 756           not been touched during a given period of time. This information can
 757           be useful to tune memory cgroup limits and/or for job placement
 758           within a compute cluster.
 759
 760           See Documentation/admin-guide/mm/idle_page_tracking.rst for
 761           more details.
 762
 763 config ARCH_HAS_PTE_DEVMAP
 764         bool
 765
 766 config ZONE_DEVICE
 767         bool "Device memory (pmem, HMM, etc...) hotplug support"
 768         depends on MEMORY_HOTPLUG
 769         depends on MEMORY_HOTREMOVE
 770         depends on SPARSEMEM_VMEMMAP
 771         depends on ARCH_HAS_PTE_DEVMAP
 772         select XARRAY_MULTI
 773
 774         help
 775           Device memory hotplug support allows for establishing pmem,
 776           or other device driver discovered memory regions, in the
 777           memmap. This allows pfn_to_page() lookups of otherwise
 778           "device-physical" addresses which is needed for using a DAX
 779           mapping in an O_DIRECT operation, among other things.
 780
 781           If FS_DAX is enabled, then say Y.
 782
 783 config DEV_PAGEMAP_OPS
 784         bool
 785
 786 #
 787 # Helpers to mirror range of the CPU page tables of a process into device page
 788 # tables.
 789 #
 790 config HMM_MIRROR
 791         bool
 792         depends on MMU
 793
 794 config DEVICE_PRIVATE
 795         bool "Unaddressable device memory (GPU memory, ...)"
 796         depends on ZONE_DEVICE
 797         select DEV_PAGEMAP_OPS
 798
 799         help
 800           Allows creation of struct pages to represent unaddressable device
 801           memory; i.e., memory that is only accessible from the device (or
 802           group of devices). You likely also want to select HMM_MIRROR.
 803
 804 config VMAP_PFN
 805         bool
 806
 807 config FRAME_VECTOR
 808         bool
 809
 810 config ARCH_USES_HIGH_VMA_FLAGS
 811         bool
 812 config ARCH_HAS_PKEYS
 813         bool
 814
 815 config PERCPU_STATS
 816         bool "Collect percpu memory statistics"
 817         help
 818           This feature collects and exposes statistics via debugfs. The
 819           information includes global and per chunk statistics, which can
 820           be used to help understand percpu memory usage.
 821
 822 config GUP_TEST
 823         bool "Enable infrastructure for get_user_pages()-related unit tests"
 824         depends on DEBUG_FS
 825         help
 826           Provides /sys/kernel/debug/gup_test, which in turn provides a way
 827           to make ioctl calls that can launch kernel-based unit tests for
 828           the get_user_pages*() and pin_user_pages*() family of API calls.
 829
 830           These tests include benchmark testing of the _fast variants of
 831           get_user_pages*() and pin_user_pages*(), as well as smoke tests of
 832           the non-_fast variants.
 833
 834           There is also a sub-test that allows running dump_page() on any
 835           of up to eight pages (selected by command line args) within the
 836           range of user-space addresses. These pages are either pinned via
 837           pin_user_pages*(), or pinned via get_user_pages*(), as specified
 838           by other command line arguments.
 839
 840           See tools/testing/selftests/vm/gup_test.c
 841
 842 comment "GUP_TEST needs to have DEBUG_FS enabled"
 843         depends on !GUP_TEST && !DEBUG_FS
 844
 845 config GUP_GET_PTE_LOW_HIGH
 846         bool
 847
 848 config READ_ONLY_THP_FOR_FS
 849         bool "Read-only THP for filesystems (EXPERIMENTAL)"
 850         depends on TRANSPARENT_HUGEPAGE && SHMEM
 851
 852         help
 853           Allow khugepaged to put read-only file-backed pages in THP.
 854
 855           This is marked experimental because it is a new feature. Write
 856           support of file THPs will be developed in the next few release
 857           cycles.
 858
 859 config ARCH_HAS_PTE_SPECIAL
 860         bool
 861
 862 #
 863 # Some architectures require a special hugepage directory format that is
 864 # required to support multiple hugepage sizes. For example a4fe3ce76
 865 # "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
 866 # introduced it on powerpc.  This allows for a more flexible hugepage
 867 # pagetable layouts.
 868 #
 869 config ARCH_HAS_HUGEPD
 870         bool
 871
 872 config MAPPING_DIRTY_HELPERS
 873         bool
 874
 875 config KMAP_LOCAL
 876         bool
 877
 878 endmenu