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_PHYS_MAP
 130         bool
 131
 132 config HAVE_FAST_GUP
 133         depends on MMU
 134         bool
 135
 136 # Don't discard allocated memory used to track "memory" and "reserved" memblocks
 137 # after early boot, so it can still be used to test for validity of memory.
 138 # Also, memblocks are updated with memory hot(un)plug.
 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         depends on 64BIT || BROKEN
 162         select NUMA_KEEP_MEMINFO if NUMA
 163
 164 config MEMORY_HOTPLUG_SPARSE
 165         def_bool y
 166         depends on SPARSEMEM && MEMORY_HOTPLUG
 167
 168 config MEMORY_HOTPLUG_DEFAULT_ONLINE
 169         bool "Online the newly added memory blocks by default"
 170         depends on MEMORY_HOTPLUG
 171         help
 172           This option sets the default policy setting for memory hotplug
 173           onlining policy (/sys/devices/system/memory/auto_online_blocks) which
 174           determines what happens to newly added memory regions. Policy setting
 175           can always be changed at runtime.
 176           See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
 177
 178           Say Y here if you want all hot-plugged memory blocks to appear in
 179           'online' state by default.
 180           Say N here if you want the default policy to keep all hot-plugged
 181           memory blocks in 'offline' state.
 182
 183 config MEMORY_HOTREMOVE
 184         bool "Allow for memory hot remove"
 185         select MEMORY_ISOLATION
 186         select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
 187         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 188         depends on MIGRATION
 189
 190 # Heavily threaded applications may benefit from splitting the mm-wide
 191 # page_table_lock, so that faults on different parts of the user address
 192 # space can be handled with less contention: split it at this NR_CPUS.
 193 # Default to 4 for wider testing, though 8 might be more appropriate.
 194 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 195 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 196 # SPARC32 allocates multiple pte tables within a single page, and therefore
 197 # a per-page lock leads to problems when multiple tables need to be locked
 198 # at the same time (e.g. copy_page_range()).
 199 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
 200 #
 201 config SPLIT_PTLOCK_CPUS
 202         int
 203         default "999999" if !MMU
 204         default "999999" if ARM && !CPU_CACHE_VIPT
 205         default "999999" if PARISC && !PA20
 206         default "999999" if SPARC32
 207         default "4"
 208
 209 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
 210         bool
 211
 212 #
 213 # support for memory balloon
 214 config MEMORY_BALLOON
 215         bool
 216
 217 #
 218 # support for memory balloon compaction
 219 config BALLOON_COMPACTION
 220         bool "Allow for balloon memory compaction/migration"
 221         def_bool y
 222         depends on COMPACTION && MEMORY_BALLOON
 223         help
 224           Memory fragmentation introduced by ballooning might reduce
 225           significantly the number of 2MB contiguous memory blocks that can be
 226           used within a guest, thus imposing performance penalties associated
 227           with the reduced number of transparent huge pages that could be used
 228           by the guest workload. Allowing the compaction & migration for memory
 229           pages enlisted as being part of memory balloon devices avoids the
 230           scenario aforementioned and helps improving memory defragmentation.
 231
 232 #
 233 # support for memory compaction
 234 config COMPACTION
 235         bool "Allow for memory compaction"
 236         def_bool y
 237         select MIGRATION
 238         depends on MMU
 239         help
 240           Compaction is the only memory management component to form
 241           high order (larger physically contiguous) memory blocks
 242           reliably. The page allocator relies on compaction heavily and
 243           the lack of the feature can lead to unexpected OOM killer
 244           invocations for high order memory requests. You shouldn't
 245           disable this option unless there really is a strong reason for
 246           it and then we would be really interested to hear about that at
 247           linux-mm@kvack.org.
 248
 249 #
 250 # support for free page reporting
 251 config PAGE_REPORTING
 252         bool "Free page reporting"
 253         def_bool n
 254         help
 255           Free page reporting allows for the incremental acquisition of
 256           free pages from the buddy allocator for the purpose of reporting
 257           those pages to another entity, such as a hypervisor, so that the
 258           memory can be freed within the host for other uses.
 259
 260 #
 261 # support for page migration
 262 #
 263 config MIGRATION
 264         bool "Page migration"
 265         def_bool y
 266         depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
 267         help
 268           Allows the migration of the physical location of pages of processes
 269           while the virtual addresses are not changed. This is useful in
 270           two situations. The first is on NUMA systems to put pages nearer
 271           to the processors accessing. The second is when allocating huge
 272           pages as migration can relocate pages to satisfy a huge page
 273           allocation instead of reclaiming.
 274
 275 config ARCH_ENABLE_HUGEPAGE_MIGRATION
 276         bool
 277
 278 config ARCH_ENABLE_THP_MIGRATION
 279         bool
 280
 281 config CONTIG_ALLOC
 282         def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
 283
 284 config PHYS_ADDR_T_64BIT
 285         def_bool 64BIT
 286
 287 config BOUNCE
 288         bool "Enable bounce buffers"
 289         default y
 290         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 291         help
 292           Enable bounce buffers for devices that cannot access
 293           the full range of memory available to the CPU. Enabled
 294           by default when ZONE_DMA or HIGHMEM is selected, but you
 295           may say n to override this.
 296
 297 config VIRT_TO_BUS
 298         bool
 299         help
 300           An architecture should select this if it implements the
 301           deprecated interface virt_to_bus().  All new architectures
 302           should probably not select this.
 303
 304
 305 config MMU_NOTIFIER
 306         bool
 307         select SRCU
 308         select INTERVAL_TREE
 309
 310 config KSM
 311         bool "Enable KSM for page merging"
 312         depends on MMU
 313         select XXHASH
 314         help
 315           Enable Kernel Samepage Merging: KSM periodically scans those areas
 316           of an application's address space that an app has advised may be
 317           mergeable.  When it finds pages of identical content, it replaces
 318           the many instances by a single page with that content, so
 319           saving memory until one or another app needs to modify the content.
 320           Recommended for use with KVM, or with other duplicative applications.
 321           See Documentation/vm/ksm.rst for more information: KSM is inactive
 322           until a program has madvised that an area is MADV_MERGEABLE, and
 323           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 324
 325 config DEFAULT_MMAP_MIN_ADDR
 326         int "Low address space to protect from user allocation"
 327         depends on MMU
 328         default 4096
 329         help
 330           This is the portion of low virtual memory which should be protected
 331           from userspace allocation.  Keeping a user from writing to low pages
 332           can help reduce the impact of kernel NULL pointer bugs.
 333
 334           For most ia64, ppc64 and x86 users with lots of address space
 335           a value of 65536 is reasonable and should cause no problems.
 336           On arm and other archs it should not be higher than 32768.
 337           Programs which use vm86 functionality or have some need to map
 338           this low address space will need CAP_SYS_RAWIO or disable this
 339           protection by setting the value to 0.
 340
 341           This value can be changed after boot using the
 342           /proc/sys/vm/mmap_min_addr tunable.
 343
 344 config ARCH_SUPPORTS_MEMORY_FAILURE
 345         bool
 346
 347 config MEMORY_FAILURE
 348         depends on MMU
 349         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 350         bool "Enable recovery from hardware memory errors"
 351         select MEMORY_ISOLATION
 352         select RAS
 353         help
 354           Enables code to recover from some memory failures on systems
 355           with MCA recovery. This allows a system to continue running
 356           even when some of its memory has uncorrected errors. This requires
 357           special hardware support and typically ECC memory.
 358
 359 config HWPOISON_INJECT
 360         tristate "HWPoison pages injector"
 361         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 362         select PROC_PAGE_MONITOR
 363
 364 config NOMMU_INITIAL_TRIM_EXCESS
 365         int "Turn on mmap() excess space trimming before booting"
 366         depends on !MMU
 367         default 1
 368         help
 369           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 370           of memory on which to store mappings, but it can only ask the system
 371           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 372           more than it requires.  To deal with this, mmap() is able to trim off
 373           the excess and return it to the allocator.
 374
 375           If trimming is enabled, the excess is trimmed off and returned to the
 376           system allocator, which can cause extra fragmentation, particularly
 377           if there are a lot of transient processes.
 378
 379           If trimming is disabled, the excess is kept, but not used, which for
 380           long-term mappings means that the space is wasted.
 381
 382           Trimming can be dynamically controlled through a sysctl option
 383           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 384           excess pages there must be before trimming should occur, or zero if
 385           no trimming is to occur.
 386
 387           This option specifies the initial value of this option.  The default
 388           of 1 says that all excess pages should be trimmed.
 389
 390           See Documentation/nommu-mmap.txt for more information.
 391
 392 config TRANSPARENT_HUGEPAGE
 393         bool "Transparent Hugepage Support"
 394         depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
 395         select COMPACTION
 396         select XARRAY_MULTI
 397         help
 398           Transparent Hugepages allows the kernel to use huge pages and
 399           huge tlb transparently to the applications whenever possible.
 400           This feature can improve computing performance to certain
 401           applications by speeding up page faults during memory
 402           allocation, by reducing the number of tlb misses and by speeding
 403           up the pagetable walking.
 404
 405           If memory constrained on embedded, you may want to say N.
 406
 407 choice
 408         prompt "Transparent Hugepage Support sysfs defaults"
 409         depends on TRANSPARENT_HUGEPAGE
 410         default TRANSPARENT_HUGEPAGE_ALWAYS
 411         help
 412           Selects the sysfs defaults for Transparent Hugepage Support.
 413
 414         config TRANSPARENT_HUGEPAGE_ALWAYS
 415                 bool "always"
 416         help
 417           Enabling Transparent Hugepage always, can increase the
 418           memory footprint of applications without a guaranteed
 419           benefit but it will work automatically for all applications.
 420
 421         config TRANSPARENT_HUGEPAGE_MADVISE
 422                 bool "madvise"
 423         help
 424           Enabling Transparent Hugepage madvise, will only provide a
 425           performance improvement benefit to the applications using
 426           madvise(MADV_HUGEPAGE) but it won't risk to increase the
 427           memory footprint of applications without a guaranteed
 428           benefit.
 429 endchoice
 430
 431 config ARCH_WANTS_THP_SWAP
 432         def_bool n
 433
 434 config THP_SWAP
 435         def_bool y
 436         depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
 437         help
 438           Swap transparent huge pages in one piece, without splitting.
 439           XXX: For now, swap cluster backing transparent huge page
 440           will be split after swapout.
 441
 442           For selection by architectures with reasonable THP sizes.
 443
 444 #
 445 # UP and nommu archs use km based percpu allocator
 446 #
 447 config NEED_PER_CPU_KM
 448         depends on !SMP
 449         bool
 450         default y
 451
 452 config CLEANCACHE
 453         bool "Enable cleancache driver to cache clean pages if tmem is present"
 454         help
 455           Cleancache can be thought of as a page-granularity victim cache
 456           for clean pages that the kernel's pageframe replacement algorithm
 457           (PFRA) would like to keep around, but can't since there isn't enough
 458           memory.  So when the PFRA "evicts" a page, it first attempts to use
 459           cleancache code to put the data contained in that page into
 460           "transcendent memory", memory that is not directly accessible or
 461           addressable by the kernel and is of unknown and possibly
 462           time-varying size.  And when a cleancache-enabled
 463           filesystem wishes to access a page in a file on disk, it first
 464           checks cleancache to see if it already contains it; if it does,
 465           the page is copied into the kernel and a disk access is avoided.
 466           When a transcendent memory driver is available (such as zcache or
 467           Xen transcendent memory), a significant I/O reduction
 468           may be achieved.  When none is available, all cleancache calls
 469           are reduced to a single pointer-compare-against-NULL resulting
 470           in a negligible performance hit.
 471
 472           If unsure, say Y to enable cleancache
 473
 474 config FRONTSWAP
 475         bool "Enable frontswap to cache swap pages if tmem is present"
 476         depends on SWAP
 477         help
 478           Frontswap is so named because it can be thought of as the opposite
 479           of a "backing" store for a swap device.  The data is stored into
 480           "transcendent memory", memory that is not directly accessible or
 481           addressable by the kernel and is of unknown and possibly
 482           time-varying size.  When space in transcendent memory is available,
 483           a significant swap I/O reduction may be achieved.  When none is
 484           available, all frontswap calls are reduced to a single pointer-
 485           compare-against-NULL resulting in a negligible performance hit
 486           and swap data is stored as normal on the matching swap device.
 487
 488           If unsure, say Y to enable frontswap.
 489
 490 config CMA
 491         bool "Contiguous Memory Allocator"
 492         depends on MMU
 493         select MIGRATION
 494         select MEMORY_ISOLATION
 495         help
 496           This enables the Contiguous Memory Allocator which allows other
 497           subsystems to allocate big physically-contiguous blocks of memory.
 498           CMA reserves a region of memory and allows only movable pages to
 499           be allocated from it. This way, the kernel can use the memory for
 500           pagecache and when a subsystem requests for contiguous area, the
 501           allocated pages are migrated away to serve the contiguous request.
 502
 503           If unsure, say "n".
 504
 505 config CMA_DEBUG
 506         bool "CMA debug messages (DEVELOPMENT)"
 507         depends on DEBUG_KERNEL && CMA
 508         help
 509           Turns on debug messages in CMA.  This produces KERN_DEBUG
 510           messages for every CMA call as well as various messages while
 511           processing calls such as dma_alloc_from_contiguous().
 512           This option does not affect warning and error messages.
 513
 514 config CMA_DEBUGFS
 515         bool "CMA debugfs interface"
 516         depends on CMA && DEBUG_FS
 517         help
 518           Turns on the DebugFS interface for CMA.
 519
 520 config CMA_AREAS
 521         int "Maximum count of the CMA areas"
 522         depends on CMA
 523         default 7
 524         help
 525           CMA allows to create CMA areas for particular purpose, mainly,
 526           used as device private area. This parameter sets the maximum
 527           number of CMA area in the system.
 528
 529           If unsure, leave the default value "7".
 530
 531 config MEM_SOFT_DIRTY
 532         bool "Track memory changes"
 533         depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
 534         select PROC_PAGE_MONITOR
 535         help
 536           This option enables memory changes tracking by introducing a
 537           soft-dirty bit on pte-s. This bit it set when someone writes
 538           into a page just as regular dirty bit, but unlike the latter
 539           it can be cleared by hands.
 540
 541           See Documentation/admin-guide/mm/soft-dirty.rst for more details.
 542
 543 config ZSWAP
 544         bool "Compressed cache for swap pages (EXPERIMENTAL)"
 545         depends on FRONTSWAP && CRYPTO=y
 546         select ZPOOL
 547         help
 548           A lightweight compressed cache for swap pages.  It takes
 549           pages that are in the process of being swapped out and attempts to
 550           compress them into a dynamically allocated RAM-based memory pool.
 551           This can result in a significant I/O reduction on swap device and,
 552           in the case where decompressing from RAM is faster that swap device
 553           reads, can also improve workload performance.
 554
 555           This is marked experimental because it is a new feature (as of
 556           v3.11) that interacts heavily with memory reclaim.  While these
 557           interactions don't cause any known issues on simple memory setups,
 558           they have not be fully explored on the large set of potential
 559           configurations and workloads that exist.
 560
 561 choice
 562         prompt "Compressed cache for swap pages default compressor"
 563         depends on ZSWAP
 564         default ZSWAP_COMPRESSOR_DEFAULT_LZO
 565         help
 566           Selects the default compression algorithm for the compressed cache
 567           for swap pages.
 568
 569           For an overview what kind of performance can be expected from
 570           a particular compression algorithm please refer to the benchmarks
 571           available at the following LWN page:
 572           https://lwn.net/Articles/751795/
 573
 574           If in doubt, select 'LZO'.
 575
 576           The selection made here can be overridden by using the kernel
 577           command line 'zswap.compressor=' option.
 578
 579 config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
 580         bool "Deflate"
 581         select CRYPTO_DEFLATE
 582         help
 583           Use the Deflate algorithm as the default compression algorithm.
 584
 585 config ZSWAP_COMPRESSOR_DEFAULT_LZO
 586         bool "LZO"
 587         select CRYPTO_LZO
 588         help
 589           Use the LZO algorithm as the default compression algorithm.
 590
 591 config ZSWAP_COMPRESSOR_DEFAULT_842
 592         bool "842"
 593         select CRYPTO_842
 594         help
 595           Use the 842 algorithm as the default compression algorithm.
 596
 597 config ZSWAP_COMPRESSOR_DEFAULT_LZ4
 598         bool "LZ4"
 599         select CRYPTO_LZ4
 600         help
 601           Use the LZ4 algorithm as the default compression algorithm.
 602
 603 config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
 604         bool "LZ4HC"
 605         select CRYPTO_LZ4HC
 606         help
 607           Use the LZ4HC algorithm as the default compression algorithm.
 608
 609 config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
 610         bool "zstd"
 611         select CRYPTO_ZSTD
 612         help
 613           Use the zstd algorithm as the default compression algorithm.
 614 endchoice
 615
 616 config ZSWAP_COMPRESSOR_DEFAULT
 617        string
 618        depends on ZSWAP
 619        default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
 620        default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
 621        default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
 622        default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
 623        default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
 624        default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
 625        default ""
 626
 627 choice
 628         prompt "Compressed cache for swap pages default allocator"
 629         depends on ZSWAP
 630         default ZSWAP_ZPOOL_DEFAULT_ZBUD
 631         help
 632           Selects the default allocator for the compressed cache for
 633           swap pages.
 634           The default is 'zbud' for compatibility, however please do
 635           read the description of each of the allocators below before
 636           making a right choice.
 637
 638           The selection made here can be overridden by using the kernel
 639           command line 'zswap.zpool=' option.
 640
 641 config ZSWAP_ZPOOL_DEFAULT_ZBUD
 642         bool "zbud"
 643         select ZBUD
 644         help
 645           Use the zbud allocator as the default allocator.
 646
 647 config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
 648         bool "z3fold"
 649         select Z3FOLD
 650         help
 651           Use the z3fold allocator as the default allocator.
 652
 653 config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
 654         bool "zsmalloc"
 655         select ZSMALLOC
 656         help
 657           Use the zsmalloc allocator as the default allocator.
 658 endchoice
 659
 660 config ZSWAP_ZPOOL_DEFAULT
 661        string
 662        depends on ZSWAP
 663        default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
 664        default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
 665        default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
 666        default ""
 667
 668 config ZSWAP_DEFAULT_ON
 669         bool "Enable the compressed cache for swap pages by default"
 670         depends on ZSWAP
 671         help
 672           If selected, the compressed cache for swap pages will be enabled
 673           at boot, otherwise it will be disabled.
 674
 675           The selection made here can be overridden by using the kernel
 676           command line 'zswap.enabled=' option.
 677
 678 config ZPOOL
 679         tristate "Common API for compressed memory storage"
 680         help
 681           Compressed memory storage API.  This allows using either zbud or
 682           zsmalloc.
 683
 684 config ZBUD
 685         tristate "Low (Up to 2x) density storage for compressed pages"
 686         help
 687           A special purpose allocator for storing compressed pages.
 688           It is designed to store up to two compressed pages per physical
 689           page.  While this design limits storage density, it has simple and
 690           deterministic reclaim properties that make it preferable to a higher
 691           density approach when reclaim will be used.
 692
 693 config Z3FOLD
 694         tristate "Up to 3x density storage for compressed pages"
 695         depends on ZPOOL
 696         help
 697           A special purpose allocator for storing compressed pages.
 698           It is designed to store up to three compressed pages per physical
 699           page. It is a ZBUD derivative so the simplicity and determinism are
 700           still there.
 701
 702 config ZSMALLOC
 703         tristate "Memory allocator for compressed pages"
 704         depends on MMU
 705         help
 706           zsmalloc is a slab-based memory allocator designed to store
 707           compressed RAM pages.  zsmalloc uses virtual memory mapping
 708           in order to reduce fragmentation.  However, this results in a
 709           non-standard allocator interface where a handle, not a pointer, is
 710           returned by an alloc().  This handle must be mapped in order to
 711           access the allocated space.
 712
 713 config ZSMALLOC_PGTABLE_MAPPING
 714         bool "Use page table mapping to access object in zsmalloc"
 715         depends on ZSMALLOC=y
 716         help
 717           By default, zsmalloc uses a copy-based object mapping method to
 718           access allocations that span two pages. However, if a particular
 719           architecture (ex, ARM) performs VM mapping faster than copying,
 720           then you should select this. This causes zsmalloc to use page table
 721           mapping rather than copying for object mapping.
 722
 723           You can check speed with zsmalloc benchmark:
 724           https://github.com/spartacus06/zsmapbench
 725
 726 config ZSMALLOC_STAT
 727         bool "Export zsmalloc statistics"
 728         depends on ZSMALLOC
 729         select DEBUG_FS
 730         help
 731           This option enables code in the zsmalloc to collect various
 732           statistics about whats happening in zsmalloc and exports that
 733           information to userspace via debugfs.
 734           If unsure, say N.
 735
 736 config GENERIC_EARLY_IOREMAP
 737         bool
 738
 739 config MAX_STACK_SIZE_MB
 740         int "Maximum user stack size for 32-bit processes (MB)"
 741         default 80
 742         range 8 2048
 743         depends on STACK_GROWSUP && (!64BIT || COMPAT)
 744         help
 745           This is the maximum stack size in Megabytes in the VM layout of 32-bit
 746           user processes when the stack grows upwards (currently only on parisc
 747           arch). The stack will be located at the highest memory address minus
 748           the given value, unless the RLIMIT_STACK hard limit is changed to a
 749           smaller value in which case that is used.
 750
 751           A sane initial value is 80 MB.
 752
 753 config DEFERRED_STRUCT_PAGE_INIT
 754         bool "Defer initialisation of struct pages to kthreads"
 755         depends on SPARSEMEM
 756         depends on !NEED_PER_CPU_KM
 757         depends on 64BIT
 758         select PADATA
 759         help
 760           Ordinarily all struct pages are initialised during early boot in a
 761           single thread. On very large machines this can take a considerable
 762           amount of time. If this option is set, large machines will bring up
 763           a subset of memmap at boot and then initialise the rest in parallel.
 764           This has a potential performance impact on tasks running early in the
 765           lifetime of the system until these kthreads finish the
 766           initialisation.
 767
 768 config IDLE_PAGE_TRACKING
 769         bool "Enable idle page tracking"
 770         depends on SYSFS && MMU
 771         select PAGE_EXTENSION if !64BIT
 772         help
 773           This feature allows to estimate the amount of user pages that have
 774           not been touched during a given period of time. This information can
 775           be useful to tune memory cgroup limits and/or for job placement
 776           within a compute cluster.
 777
 778           See Documentation/admin-guide/mm/idle_page_tracking.rst for
 779           more details.
 780
 781 config ARCH_HAS_PTE_DEVMAP
 782         bool
 783
 784 config ZONE_DEVICE
 785         bool "Device memory (pmem, HMM, etc...) hotplug support"
 786         depends on MEMORY_HOTPLUG
 787         depends on MEMORY_HOTREMOVE
 788         depends on SPARSEMEM_VMEMMAP
 789         depends on ARCH_HAS_PTE_DEVMAP
 790         select XARRAY_MULTI
 791
 792         help
 793           Device memory hotplug support allows for establishing pmem,
 794           or other device driver discovered memory regions, in the
 795           memmap. This allows pfn_to_page() lookups of otherwise
 796           "device-physical" addresses which is needed for using a DAX
 797           mapping in an O_DIRECT operation, among other things.
 798
 799           If FS_DAX is enabled, then say Y.
 800
 801 config DEV_PAGEMAP_OPS
 802         bool
 803
 804 #
 805 # Helpers to mirror range of the CPU page tables of a process into device page
 806 # tables.
 807 #
 808 config HMM_MIRROR
 809         bool
 810         depends on MMU
 811
 812 config DEVICE_PRIVATE
 813         bool "Unaddressable device memory (GPU memory, ...)"
 814         depends on ZONE_DEVICE
 815         select DEV_PAGEMAP_OPS
 816
 817         help
 818           Allows creation of struct pages to represent unaddressable device
 819           memory; i.e., memory that is only accessible from the device (or
 820           group of devices). You likely also want to select HMM_MIRROR.
 821
 822 config FRAME_VECTOR
 823         bool
 824
 825 config ARCH_USES_HIGH_VMA_FLAGS
 826         bool
 827 config ARCH_HAS_PKEYS
 828         bool
 829
 830 config PERCPU_STATS
 831         bool "Collect percpu memory statistics"
 832         help
 833           This feature collects and exposes statistics via debugfs. The
 834           information includes global and per chunk statistics, which can
 835           be used to help understand percpu memory usage.
 836
 837 config GUP_BENCHMARK
 838         bool "Enable infrastructure for get_user_pages_fast() benchmarking"
 839         help
 840           Provides /sys/kernel/debug/gup_benchmark that helps with testing
 841           performance of get_user_pages_fast().
 842
 843           See tools/testing/selftests/vm/gup_benchmark.c
 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 endmenu