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         depends on SPARSEMEM || X86_64_ACPI_NUMA
 156         depends on ARCH_ENABLE_MEMORY_HOTPLUG
 157         depends on 64BIT || BROKEN
 158         select NUMA_KEEP_MEMINFO if NUMA
 159
 160 config MEMORY_HOTPLUG_SPARSE
 161         def_bool y
 162         depends on SPARSEMEM && MEMORY_HOTPLUG
 163
 164 config MEMORY_HOTPLUG_DEFAULT_ONLINE
 165         bool "Online the newly added memory blocks by default"
 166         depends on MEMORY_HOTPLUG
 167         help
 168           This option sets the default policy setting for memory hotplug
 169           onlining policy (/sys/devices/system/memory/auto_online_blocks) which
 170           determines what happens to newly added memory regions. Policy setting
 171           can always be changed at runtime.
 172           See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
 173
 174           Say Y here if you want all hot-plugged memory blocks to appear in
 175           'online' state by default.
 176           Say N here if you want the default policy to keep all hot-plugged
 177           memory blocks in 'offline' state.
 178
 179 config MEMORY_HOTREMOVE
 180         bool "Allow for memory hot remove"
 181         select MEMORY_ISOLATION
 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 7
 520         help
 521           CMA allows to create CMA areas for particular purpose, mainly,
 522           used as device private area. This parameter sets the maximum
 523           number of CMA area in the system.
 524
 525           If unsure, leave the default value "7".
 526
 527 config MEM_SOFT_DIRTY
 528         bool "Track memory changes"
 529         depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
 530         select PROC_PAGE_MONITOR
 531         help
 532           This option enables memory changes tracking by introducing a
 533           soft-dirty bit on pte-s. This bit it set when someone writes
 534           into a page just as regular dirty bit, but unlike the latter
 535           it can be cleared by hands.
 536
 537           See Documentation/admin-guide/mm/soft-dirty.rst for more details.
 538
 539 config ZSWAP
 540         bool "Compressed cache for swap pages (EXPERIMENTAL)"
 541         depends on FRONTSWAP && CRYPTO=y
 542         select ZPOOL
 543         help
 544           A lightweight compressed cache for swap pages.  It takes
 545           pages that are in the process of being swapped out and attempts to
 546           compress them into a dynamically allocated RAM-based memory pool.
 547           This can result in a significant I/O reduction on swap device and,
 548           in the case where decompressing from RAM is faster that swap device
 549           reads, can also improve workload performance.
 550
 551           This is marked experimental because it is a new feature (as of
 552           v3.11) that interacts heavily with memory reclaim.  While these
 553           interactions don't cause any known issues on simple memory setups,
 554           they have not be fully explored on the large set of potential
 555           configurations and workloads that exist.
 556
 557 choice
 558         prompt "Compressed cache for swap pages default compressor"
 559         depends on ZSWAP
 560         default ZSWAP_COMPRESSOR_DEFAULT_LZO
 561         help
 562           Selects the default compression algorithm for the compressed cache
 563           for swap pages.
 564
 565           For an overview what kind of performance can be expected from
 566           a particular compression algorithm please refer to the benchmarks
 567           available at the following LWN page:
 568           https://lwn.net/Articles/751795/
 569
 570           If in doubt, select 'LZO'.
 571
 572           The selection made here can be overridden by using the kernel
 573           command line 'zswap.compressor=' option.
 574
 575 config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
 576         bool "Deflate"
 577         select CRYPTO_DEFLATE
 578         help
 579           Use the Deflate algorithm as the default compression algorithm.
 580
 581 config ZSWAP_COMPRESSOR_DEFAULT_LZO
 582         bool "LZO"
 583         select CRYPTO_LZO
 584         help
 585           Use the LZO algorithm as the default compression algorithm.
 586
 587 config ZSWAP_COMPRESSOR_DEFAULT_842
 588         bool "842"
 589         select CRYPTO_842
 590         help
 591           Use the 842 algorithm as the default compression algorithm.
 592
 593 config ZSWAP_COMPRESSOR_DEFAULT_LZ4
 594         bool "LZ4"
 595         select CRYPTO_LZ4
 596         help
 597           Use the LZ4 algorithm as the default compression algorithm.
 598
 599 config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
 600         bool "LZ4HC"
 601         select CRYPTO_LZ4HC
 602         help
 603           Use the LZ4HC algorithm as the default compression algorithm.
 604
 605 config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
 606         bool "zstd"
 607         select CRYPTO_ZSTD
 608         help
 609           Use the zstd algorithm as the default compression algorithm.
 610 endchoice
 611
 612 config ZSWAP_COMPRESSOR_DEFAULT
 613        string
 614        depends on ZSWAP
 615        default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
 616        default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
 617        default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
 618        default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
 619        default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
 620        default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
 621        default ""
 622
 623 choice
 624         prompt "Compressed cache for swap pages default allocator"
 625         depends on ZSWAP
 626         default ZSWAP_ZPOOL_DEFAULT_ZBUD
 627         help
 628           Selects the default allocator for the compressed cache for
 629           swap pages.
 630           The default is 'zbud' for compatibility, however please do
 631           read the description of each of the allocators below before
 632           making a right choice.
 633
 634           The selection made here can be overridden by using the kernel
 635           command line 'zswap.zpool=' option.
 636
 637 config ZSWAP_ZPOOL_DEFAULT_ZBUD
 638         bool "zbud"
 639         select ZBUD
 640         help
 641           Use the zbud allocator as the default allocator.
 642
 643 config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
 644         bool "z3fold"
 645         select Z3FOLD
 646         help
 647           Use the z3fold allocator as the default allocator.
 648
 649 config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
 650         bool "zsmalloc"
 651         select ZSMALLOC
 652         help
 653           Use the zsmalloc allocator as the default allocator.
 654 endchoice
 655
 656 config ZSWAP_ZPOOL_DEFAULT
 657        string
 658        depends on ZSWAP
 659        default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
 660        default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
 661        default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
 662        default ""
 663
 664 config ZSWAP_DEFAULT_ON
 665         bool "Enable the compressed cache for swap pages by default"
 666         depends on ZSWAP
 667         help
 668           If selected, the compressed cache for swap pages will be enabled
 669           at boot, otherwise it will be disabled.
 670
 671           The selection made here can be overridden by using the kernel
 672           command line 'zswap.enabled=' option.
 673
 674 config ZPOOL
 675         tristate "Common API for compressed memory storage"
 676         help
 677           Compressed memory storage API.  This allows using either zbud or
 678           zsmalloc.
 679
 680 config ZBUD
 681         tristate "Low (Up to 2x) density storage for compressed pages"
 682         help
 683           A special purpose allocator for storing compressed pages.
 684           It is designed to store up to two compressed pages per physical
 685           page.  While this design limits storage density, it has simple and
 686           deterministic reclaim properties that make it preferable to a higher
 687           density approach when reclaim will be used.
 688
 689 config Z3FOLD
 690         tristate "Up to 3x density storage for compressed pages"
 691         depends on ZPOOL
 692         help
 693           A special purpose allocator for storing compressed pages.
 694           It is designed to store up to three compressed pages per physical
 695           page. It is a ZBUD derivative so the simplicity and determinism are
 696           still there.
 697
 698 config ZSMALLOC
 699         tristate "Memory allocator for compressed pages"
 700         depends on MMU
 701         help
 702           zsmalloc is a slab-based memory allocator designed to store
 703           compressed RAM pages.  zsmalloc uses virtual memory mapping
 704           in order to reduce fragmentation.  However, this results in a
 705           non-standard allocator interface where a handle, not a pointer, is
 706           returned by an alloc().  This handle must be mapped in order to
 707           access the allocated space.
 708
 709 config ZSMALLOC_PGTABLE_MAPPING
 710         bool "Use page table mapping to access object in zsmalloc"
 711         depends on ZSMALLOC=y
 712         help
 713           By default, zsmalloc uses a copy-based object mapping method to
 714           access allocations that span two pages. However, if a particular
 715           architecture (ex, ARM) performs VM mapping faster than copying,
 716           then you should select this. This causes zsmalloc to use page table
 717           mapping rather than copying for object mapping.
 718
 719           You can check speed with zsmalloc benchmark:
 720           https://github.com/spartacus06/zsmapbench
 721
 722 config ZSMALLOC_STAT
 723         bool "Export zsmalloc statistics"
 724         depends on ZSMALLOC
 725         select DEBUG_FS
 726         help
 727           This option enables code in the zsmalloc to collect various
 728           statistics about whats happening in zsmalloc and exports that
 729           information to userspace via debugfs.
 730           If unsure, say N.
 731
 732 config GENERIC_EARLY_IOREMAP
 733         bool
 734
 735 config MAX_STACK_SIZE_MB
 736         int "Maximum user stack size for 32-bit processes (MB)"
 737         default 80
 738         range 8 2048
 739         depends on STACK_GROWSUP && (!64BIT || COMPAT)
 740         help
 741           This is the maximum stack size in Megabytes in the VM layout of 32-bit
 742           user processes when the stack grows upwards (currently only on parisc
 743           arch). The stack will be located at the highest memory address minus
 744           the given value, unless the RLIMIT_STACK hard limit is changed to a
 745           smaller value in which case that is used.
 746
 747           A sane initial value is 80 MB.
 748
 749 config DEFERRED_STRUCT_PAGE_INIT
 750         bool "Defer initialisation of struct pages to kthreads"
 751         depends on SPARSEMEM
 752         depends on !NEED_PER_CPU_KM
 753         depends on 64BIT
 754         select PADATA
 755         help
 756           Ordinarily all struct pages are initialised during early boot in a
 757           single thread. On very large machines this can take a considerable
 758           amount of time. If this option is set, large machines will bring up
 759           a subset of memmap at boot and then initialise the rest in parallel.
 760           This has a potential performance impact on tasks running early in the
 761           lifetime of the system until these kthreads finish the
 762           initialisation.
 763
 764 config IDLE_PAGE_TRACKING
 765         bool "Enable idle page tracking"
 766         depends on SYSFS && MMU
 767         select PAGE_EXTENSION if !64BIT
 768         help
 769           This feature allows to estimate the amount of user pages that have
 770           not been touched during a given period of time. This information can
 771           be useful to tune memory cgroup limits and/or for job placement
 772           within a compute cluster.
 773
 774           See Documentation/admin-guide/mm/idle_page_tracking.rst for
 775           more details.
 776
 777 config ARCH_HAS_PTE_DEVMAP
 778         bool
 779
 780 config ZONE_DEVICE
 781         bool "Device memory (pmem, HMM, etc...) hotplug support"
 782         depends on MEMORY_HOTPLUG
 783         depends on MEMORY_HOTREMOVE
 784         depends on SPARSEMEM_VMEMMAP
 785         depends on ARCH_HAS_PTE_DEVMAP
 786         select XARRAY_MULTI
 787
 788         help
 789           Device memory hotplug support allows for establishing pmem,
 790           or other device driver discovered memory regions, in the
 791           memmap. This allows pfn_to_page() lookups of otherwise
 792           "device-physical" addresses which is needed for using a DAX
 793           mapping in an O_DIRECT operation, among other things.
 794
 795           If FS_DAX is enabled, then say Y.
 796
 797 config DEV_PAGEMAP_OPS
 798         bool
 799
 800 #
 801 # Helpers to mirror range of the CPU page tables of a process into device page
 802 # tables.
 803 #
 804 config HMM_MIRROR
 805         bool
 806         depends on MMU
 807
 808 config DEVICE_PRIVATE
 809         bool "Unaddressable device memory (GPU memory, ...)"
 810         depends on ZONE_DEVICE
 811         select DEV_PAGEMAP_OPS
 812
 813         help
 814           Allows creation of struct pages to represent unaddressable device
 815           memory; i.e., memory that is only accessible from the device (or
 816           group of devices). You likely also want to select HMM_MIRROR.
 817
 818 config FRAME_VECTOR
 819         bool
 820
 821 config ARCH_USES_HIGH_VMA_FLAGS
 822         bool
 823 config ARCH_HAS_PKEYS
 824         bool
 825
 826 config PERCPU_STATS
 827         bool "Collect percpu memory statistics"
 828         help
 829           This feature collects and exposes statistics via debugfs. The
 830           information includes global and per chunk statistics, which can
 831           be used to help understand percpu memory usage.
 832
 833 config GUP_BENCHMARK
 834         bool "Enable infrastructure for get_user_pages() and related calls benchmarking"
 835         help
 836           Provides /sys/kernel/debug/gup_benchmark that helps with testing
 837           performance of get_user_pages() and related calls.
 838
 839           See tools/testing/selftests/vm/gup_benchmark.c
 840
 841 config GUP_GET_PTE_LOW_HIGH
 842         bool
 843
 844 config READ_ONLY_THP_FOR_FS
 845         bool "Read-only THP for filesystems (EXPERIMENTAL)"
 846         depends on TRANSPARENT_HUGEPAGE && SHMEM
 847
 848         help
 849           Allow khugepaged to put read-only file-backed pages in THP.
 850
 851           This is marked experimental because it is a new feature. Write
 852           support of file THPs will be developed in the next few release
 853           cycles.
 854
 855 config ARCH_HAS_PTE_SPECIAL
 856         bool
 857
 858 #
 859 # Some architectures require a special hugepage directory format that is
 860 # required to support multiple hugepage sizes. For example a4fe3ce76
 861 # "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
 862 # introduced it on powerpc.  This allows for a more flexible hugepage
 863 # pagetable layouts.
 864 #
 865 config ARCH_HAS_HUGEPD
 866         bool
 867
 868 config MAPPING_DIRTY_HELPERS
 869         bool
 870
 871 endmenu