mm/Kconfig

   1 # SPDX-License-Identifier: GPL-2.0-only
   2
   3 menu "Memory Management options"
   4
   5 #
   6 # For some reason microblaze and nios2 hard code SWAP=n.  Hopefully we can
   7 # add proper SWAP support to them, in which case this can be remove.
   8 #
   9 config ARCH_NO_SWAP
  10         bool
  11
  12 config ZPOOL
  13         bool
  14
  15 menuconfig SWAP
  16         bool "Support for paging of anonymous memory (swap)"
  17         depends on MMU && BLOCK && !ARCH_NO_SWAP
  18         default y
  19         help
  20           This option allows you to choose whether you want to have support
  21           for so called swap devices or swap files in your kernel that are
  22           used to provide more virtual memory than the actual RAM present
  23           in your computer.  If unsure say Y.
  24
  25 config ZSWAP
  26         bool "Compressed cache for swap pages"
  27         depends on SWAP
  28         select FRONTSWAP
  29         select CRYPTO
  30         select ZPOOL
  31         help
  32           A lightweight compressed cache for swap pages.  It takes
  33           pages that are in the process of being swapped out and attempts to
  34           compress them into a dynamically allocated RAM-based memory pool.
  35           This can result in a significant I/O reduction on swap device and,
  36           in the case where decompressing from RAM is faster than swap device
  37           reads, can also improve workload performance.
  38
  39 config ZSWAP_DEFAULT_ON
  40         bool "Enable the compressed cache for swap pages by default"
  41         depends on ZSWAP
  42         help
  43           If selected, the compressed cache for swap pages will be enabled
  44           at boot, otherwise it will be disabled.
  45
  46           The selection made here can be overridden by using the kernel
  47           command line 'zswap.enabled=' option.
  48
  49 choice
  50         prompt "Default compressor"
  51         depends on ZSWAP
  52         default ZSWAP_COMPRESSOR_DEFAULT_LZO
  53         help
  54           Selects the default compression algorithm for the compressed cache
  55           for swap pages.
  56
  57           For an overview what kind of performance can be expected from
  58           a particular compression algorithm please refer to the benchmarks
  59           available at the following LWN page:
  60           https://lwn.net/Articles/751795/
  61
  62           If in doubt, select 'LZO'.
  63
  64           The selection made here can be overridden by using the kernel
  65           command line 'zswap.compressor=' option.
  66
  67 config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
  68         bool "Deflate"
  69         select CRYPTO_DEFLATE
  70         help
  71           Use the Deflate algorithm as the default compression algorithm.
  72
  73 config ZSWAP_COMPRESSOR_DEFAULT_LZO
  74         bool "LZO"
  75         select CRYPTO_LZO
  76         help
  77           Use the LZO algorithm as the default compression algorithm.
  78
  79 config ZSWAP_COMPRESSOR_DEFAULT_842
  80         bool "842"
  81         select CRYPTO_842
  82         help
  83           Use the 842 algorithm as the default compression algorithm.
  84
  85 config ZSWAP_COMPRESSOR_DEFAULT_LZ4
  86         bool "LZ4"
  87         select CRYPTO_LZ4
  88         help
  89           Use the LZ4 algorithm as the default compression algorithm.
  90
  91 config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
  92         bool "LZ4HC"
  93         select CRYPTO_LZ4HC
  94         help
  95           Use the LZ4HC algorithm as the default compression algorithm.
  96
  97 config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
  98         bool "zstd"
  99         select CRYPTO_ZSTD
 100         help
 101           Use the zstd algorithm as the default compression algorithm.
 102 endchoice
 103
 104 config ZSWAP_COMPRESSOR_DEFAULT
 105        string
 106        depends on ZSWAP
 107        default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
 108        default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
 109        default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
 110        default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
 111        default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
 112        default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
 113        default ""
 114
 115 choice
 116         prompt "Default allocator"
 117         depends on ZSWAP
 118         default ZSWAP_ZPOOL_DEFAULT_ZBUD
 119         help
 120           Selects the default allocator for the compressed cache for
 121           swap pages.
 122           The default is 'zbud' for compatibility, however please do
 123           read the description of each of the allocators below before
 124           making a right choice.
 125
 126           The selection made here can be overridden by using the kernel
 127           command line 'zswap.zpool=' option.
 128
 129 config ZSWAP_ZPOOL_DEFAULT_ZBUD
 130         bool "zbud"
 131         select ZBUD
 132         help
 133           Use the zbud allocator as the default allocator.
 134
 135 config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
 136         bool "z3fold"
 137         select Z3FOLD
 138         help
 139           Use the z3fold allocator as the default allocator.
 140
 141 config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
 142         bool "zsmalloc"
 143         select ZSMALLOC
 144         help
 145           Use the zsmalloc allocator as the default allocator.
 146 endchoice
 147
 148 config ZSWAP_ZPOOL_DEFAULT
 149        string
 150        depends on ZSWAP
 151        default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
 152        default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
 153        default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
 154        default ""
 155
 156 config ZBUD
 157         tristate "2:1 compression allocator (zbud)"
 158         depends on ZSWAP
 159         help
 160           A special purpose allocator for storing compressed pages.
 161           It is designed to store up to two compressed pages per physical
 162           page.  While this design limits storage density, it has simple and
 163           deterministic reclaim properties that make it preferable to a higher
 164           density approach when reclaim will be used.
 165
 166 config Z3FOLD
 167         tristate "3:1 compression allocator (z3fold)"
 168         depends on ZSWAP
 169         help
 170           A special purpose allocator for storing compressed pages.
 171           It is designed to store up to three compressed pages per physical
 172           page. It is a ZBUD derivative so the simplicity and determinism are
 173           still there.
 174
 175 config ZSMALLOC
 176         tristate
 177         prompt "N:1 compression allocator (zsmalloc)" if ZSWAP
 178         depends on MMU
 179         help
 180           zsmalloc is a slab-based memory allocator designed to store
 181           pages of various compression levels efficiently. It achieves
 182           the highest storage density with the least amount of fragmentation.
 183
 184 config ZSMALLOC_STAT
 185         bool "Export zsmalloc statistics"
 186         depends on ZSMALLOC
 187         select DEBUG_FS
 188         help
 189           This option enables code in the zsmalloc to collect various
 190           statistics about what's happening in zsmalloc and exports that
 191           information to userspace via debugfs.
 192           If unsure, say N.
 193
 194 config ZSMALLOC_CHAIN_SIZE
 195         int "Maximum number of physical pages per-zspage"
 196         default 8
 197         range 4 16
 198         depends on ZSMALLOC
 199         help
 200           This option sets the upper limit on the number of physical pages
 201           that a zmalloc page (zspage) can consist of. The optimal zspage
 202           chain size is calculated for each size class during the
 203           initialization of the pool.
 204
 205           Changing this option can alter the characteristics of size classes,
 206           such as the number of pages per zspage and the number of objects
 207           per zspage. This can also result in different configurations of
 208           the pool, as zsmalloc merges size classes with similar
 209           characteristics.
 210
 211           For more information, see zsmalloc documentation.
 212
 213 menu "SLAB allocator options"
 214
 215 choice
 216         prompt "Choose SLAB allocator"
 217         default SLUB
 218         help
 219            This option allows to select a slab allocator.
 220
 221 config SLAB
 222         bool "SLAB"
 223         depends on !PREEMPT_RT
 224         select HAVE_HARDENED_USERCOPY_ALLOCATOR
 225         help
 226           The regular slab allocator that is established and known to work
 227           well in all environments. It organizes cache hot objects in
 228           per cpu and per node queues.
 229
 230 config SLUB
 231         bool "SLUB (Unqueued Allocator)"
 232         select HAVE_HARDENED_USERCOPY_ALLOCATOR
 233         help
 234            SLUB is a slab allocator that minimizes cache line usage
 235            instead of managing queues of cached objects (SLAB approach).
 236            Per cpu caching is realized using slabs of objects instead
 237            of queues of objects. SLUB can use memory efficiently
 238            and has enhanced diagnostics. SLUB is the default choice for
 239            a slab allocator.
 240
 241 endchoice
 242
 243 config SLUB_TINY
 244         bool "Configure SLUB for minimal memory footprint"
 245         depends on SLUB && EXPERT
 246         select SLAB_MERGE_DEFAULT
 247         help
 248            Configures the SLUB allocator in a way to achieve minimal memory
 249            footprint, sacrificing scalability, debugging and other features.
 250            This is intended only for the smallest system that had used the
 251            SLOB allocator and is not recommended for systems with more than
 252            16MB RAM.
 253
 254            If unsure, say N.
 255
 256 config SLAB_MERGE_DEFAULT
 257         bool "Allow slab caches to be merged"
 258         default y
 259         depends on SLAB || SLUB
 260         help
 261           For reduced kernel memory fragmentation, slab caches can be
 262           merged when they share the same size and other characteristics.
 263           This carries a risk of kernel heap overflows being able to
 264           overwrite objects from merged caches (and more easily control
 265           cache layout), which makes such heap attacks easier to exploit
 266           by attackers. By keeping caches unmerged, these kinds of exploits
 267           can usually only damage objects in the same cache. To disable
 268           merging at runtime, "slab_nomerge" can be passed on the kernel
 269           command line.
 270
 271 config SLAB_FREELIST_RANDOM
 272         bool "Randomize slab freelist"
 273         depends on SLAB || (SLUB && !SLUB_TINY)
 274         help
 275           Randomizes the freelist order used on creating new pages. This
 276           security feature reduces the predictability of the kernel slab
 277           allocator against heap overflows.
 278
 279 config SLAB_FREELIST_HARDENED
 280         bool "Harden slab freelist metadata"
 281         depends on SLAB || (SLUB && !SLUB_TINY)
 282         help
 283           Many kernel heap attacks try to target slab cache metadata and
 284           other infrastructure. This options makes minor performance
 285           sacrifices to harden the kernel slab allocator against common
 286           freelist exploit methods. Some slab implementations have more
 287           sanity-checking than others. This option is most effective with
 288           CONFIG_SLUB.
 289
 290 config SLUB_STATS
 291         default n
 292         bool "Enable SLUB performance statistics"
 293         depends on SLUB && SYSFS && !SLUB_TINY
 294         help
 295           SLUB statistics are useful to debug SLUBs allocation behavior in
 296           order find ways to optimize the allocator. This should never be
 297           enabled for production use since keeping statistics slows down
 298           the allocator by a few percentage points. The slabinfo command
 299           supports the determination of the most active slabs to figure
 300           out which slabs are relevant to a particular load.
 301           Try running: slabinfo -DA
 302
 303 config SLUB_CPU_PARTIAL
 304         default y
 305         depends on SLUB && SMP && !SLUB_TINY
 306         bool "SLUB per cpu partial cache"
 307         help
 308           Per cpu partial caches accelerate objects allocation and freeing
 309           that is local to a processor at the price of more indeterminism
 310           in the latency of the free. On overflow these caches will be cleared
 311           which requires the taking of locks that may cause latency spikes.
 312           Typically one would choose no for a realtime system.
 313
 314 endmenu # SLAB allocator options
 315
 316 config SHUFFLE_PAGE_ALLOCATOR
 317         bool "Page allocator randomization"
 318         default SLAB_FREELIST_RANDOM && ACPI_NUMA
 319         help
 320           Randomization of the page allocator improves the average
 321           utilization of a direct-mapped memory-side-cache. See section
 322           5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
 323           6.2a specification for an example of how a platform advertises
 324           the presence of a memory-side-cache. There are also incidental
 325           security benefits as it reduces the predictability of page
 326           allocations to compliment SLAB_FREELIST_RANDOM, but the
 327           default granularity of shuffling on the MAX_ORDER i.e, 10th
 328           order of pages is selected based on cache utilization benefits
 329           on x86.
 330
 331           While the randomization improves cache utilization it may
 332           negatively impact workloads on platforms without a cache. For
 333           this reason, by default, the randomization is enabled only
 334           after runtime detection of a direct-mapped memory-side-cache.
 335           Otherwise, the randomization may be force enabled with the
 336           'page_alloc.shuffle' kernel command line parameter.
 337
 338           Say Y if unsure.
 339
 340 config COMPAT_BRK
 341         bool "Disable heap randomization"
 342         default y
 343         help
 344           Randomizing heap placement makes heap exploits harder, but it
 345           also breaks ancient binaries (including anything libc5 based).
 346           This option changes the bootup default to heap randomization
 347           disabled, and can be overridden at runtime by setting
 348           /proc/sys/kernel/randomize_va_space to 2.
 349
 350           On non-ancient distros (post-2000 ones) N is usually a safe choice.
 351
 352 config MMAP_ALLOW_UNINITIALIZED
 353         bool "Allow mmapped anonymous memory to be uninitialized"
 354         depends on EXPERT && !MMU
 355         default n
 356         help
 357           Normally, and according to the Linux spec, anonymous memory obtained
 358           from mmap() has its contents cleared before it is passed to
 359           userspace.  Enabling this config option allows you to request that
 360           mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
 361           providing a huge performance boost.  If this option is not enabled,
 362           then the flag will be ignored.
 363
 364           This is taken advantage of by uClibc's malloc(), and also by
 365           ELF-FDPIC binfmt's brk and stack allocator.
 366
 367           Because of the obvious security issues, this option should only be
 368           enabled on embedded devices where you control what is run in
 369           userspace.  Since that isn't generally a problem on no-MMU systems,
 370           it is normally safe to say Y here.
 371
 372           See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
 373
 374 config SELECT_MEMORY_MODEL
 375         def_bool y
 376         depends on ARCH_SELECT_MEMORY_MODEL
 377
 378 choice
 379         prompt "Memory model"
 380         depends on SELECT_MEMORY_MODEL
 381         default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
 382         default FLATMEM_MANUAL
 383         help
 384           This option allows you to change some of the ways that
 385           Linux manages its memory internally. Most users will
 386           only have one option here selected by the architecture
 387           configuration. This is normal.
 388
 389 config FLATMEM_MANUAL
 390         bool "Flat Memory"
 391         depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE
 392         help
 393           This option is best suited for non-NUMA systems with
 394           flat address space. The FLATMEM is the most efficient
 395           system in terms of performance and resource consumption
 396           and it is the best option for smaller systems.
 397
 398           For systems that have holes in their physical address
 399           spaces and for features like NUMA and memory hotplug,
 400           choose "Sparse Memory".
 401
 402           If unsure, choose this option (Flat Memory) over any other.
 403
 404 config SPARSEMEM_MANUAL
 405         bool "Sparse Memory"
 406         depends on ARCH_SPARSEMEM_ENABLE
 407         help
 408           This will be the only option for some systems, including
 409           memory hot-plug systems.  This is normal.
 410
 411           This option provides efficient support for systems with
 412           holes is their physical address space and allows memory
 413           hot-plug and hot-remove.
 414
 415           If unsure, choose "Flat Memory" over this option.
 416
 417 endchoice
 418
 419 config SPARSEMEM
 420         def_bool y
 421         depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
 422
 423 config FLATMEM
 424         def_bool y
 425         depends on !SPARSEMEM || FLATMEM_MANUAL
 426
 427 #
 428 # SPARSEMEM_EXTREME (which is the default) does some bootmem
 429 # allocations when sparse_init() is called.  If this cannot
 430 # be done on your architecture, select this option.  However,
 431 # statically allocating the mem_section[] array can potentially
 432 # consume vast quantities of .bss, so be careful.
 433 #
 434 # This option will also potentially produce smaller runtime code
 435 # with gcc 3.4 and later.
 436 #
 437 config SPARSEMEM_STATIC
 438         bool
 439
 440 #
 441 # Architecture platforms which require a two level mem_section in SPARSEMEM
 442 # must select this option. This is usually for architecture platforms with
 443 # an extremely sparse physical address space.
 444 #
 445 config SPARSEMEM_EXTREME
 446         def_bool y
 447         depends on SPARSEMEM && !SPARSEMEM_STATIC
 448
 449 config SPARSEMEM_VMEMMAP_ENABLE
 450         bool
 451
 452 config SPARSEMEM_VMEMMAP
 453         bool "Sparse Memory virtual memmap"
 454         depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
 455         default y
 456         help
 457           SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
 458           pfn_to_page and page_to_pfn operations.  This is the most
 459           efficient option when sufficient kernel resources are available.
 460 #
 461 # Select this config option from the architecture Kconfig, if it is preferred
 462 # to enable the feature of HugeTLB/dev_dax vmemmap optimization.
 463 #
 464 config ARCH_WANT_OPTIMIZE_VMEMMAP
 465         bool
 466
 467 config HAVE_MEMBLOCK_PHYS_MAP
 468         bool
 469
 470 config HAVE_FAST_GUP
 471         depends on MMU
 472         bool
 473
 474 # Don't discard allocated memory used to track "memory" and "reserved" memblocks
 475 # after early boot, so it can still be used to test for validity of memory.
 476 # Also, memblocks are updated with memory hot(un)plug.
 477 config ARCH_KEEP_MEMBLOCK
 478         bool
 479
 480 # Keep arch NUMA mapping infrastructure post-init.
 481 config NUMA_KEEP_MEMINFO
 482         bool
 483
 484 config MEMORY_ISOLATION
 485         bool
 486
 487 # IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked
 488 # IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via
 489 # /dev/mem.
 490 config EXCLUSIVE_SYSTEM_RAM
 491         def_bool y
 492         depends on !DEVMEM || STRICT_DEVMEM
 493
 494 #
 495 # Only be set on architectures that have completely implemented memory hotplug
 496 # feature. If you are not sure, don't touch it.
 497 #
 498 config HAVE_BOOTMEM_INFO_NODE
 499         def_bool n
 500
 501 config ARCH_ENABLE_MEMORY_HOTPLUG
 502         bool
 503
 504 config ARCH_ENABLE_MEMORY_HOTREMOVE
 505         bool
 506
 507 # eventually, we can have this option just 'select SPARSEMEM'
 508 menuconfig MEMORY_HOTPLUG
 509         bool "Memory hotplug"
 510         select MEMORY_ISOLATION
 511         depends on SPARSEMEM
 512         depends on ARCH_ENABLE_MEMORY_HOTPLUG
 513         depends on 64BIT
 514         select NUMA_KEEP_MEMINFO if NUMA
 515
 516 if MEMORY_HOTPLUG
 517
 518 config MEMORY_HOTPLUG_DEFAULT_ONLINE
 519         bool "Online the newly added memory blocks by default"
 520         depends on MEMORY_HOTPLUG
 521         help
 522           This option sets the default policy setting for memory hotplug
 523           onlining policy (/sys/devices/system/memory/auto_online_blocks) which
 524           determines what happens to newly added memory regions. Policy setting
 525           can always be changed at runtime.
 526           See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
 527
 528           Say Y here if you want all hot-plugged memory blocks to appear in
 529           'online' state by default.
 530           Say N here if you want the default policy to keep all hot-plugged
 531           memory blocks in 'offline' state.
 532
 533 config MEMORY_HOTREMOVE
 534         bool "Allow for memory hot remove"
 535         select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
 536         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 537         depends on MIGRATION
 538
 539 config MHP_MEMMAP_ON_MEMORY
 540         def_bool y
 541         depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
 542         depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
 543
 544 endif # MEMORY_HOTPLUG
 545
 546 # Heavily threaded applications may benefit from splitting the mm-wide
 547 # page_table_lock, so that faults on different parts of the user address
 548 # space can be handled with less contention: split it at this NR_CPUS.
 549 # Default to 4 for wider testing, though 8 might be more appropriate.
 550 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 551 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 552 # SPARC32 allocates multiple pte tables within a single page, and therefore
 553 # a per-page lock leads to problems when multiple tables need to be locked
 554 # at the same time (e.g. copy_page_range()).
 555 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
 556 #
 557 config SPLIT_PTLOCK_CPUS
 558         int
 559         default "999999" if !MMU
 560         default "999999" if ARM && !CPU_CACHE_VIPT
 561         default "999999" if PARISC && !PA20
 562         default "999999" if SPARC32
 563         default "4"
 564
 565 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
 566         bool
 567
 568 #
 569 # support for memory balloon
 570 config MEMORY_BALLOON
 571         bool
 572
 573 #
 574 # support for memory balloon compaction
 575 config BALLOON_COMPACTION
 576         bool "Allow for balloon memory compaction/migration"
 577         def_bool y
 578         depends on COMPACTION && MEMORY_BALLOON
 579         help
 580           Memory fragmentation introduced by ballooning might reduce
 581           significantly the number of 2MB contiguous memory blocks that can be
 582           used within a guest, thus imposing performance penalties associated
 583           with the reduced number of transparent huge pages that could be used
 584           by the guest workload. Allowing the compaction & migration for memory
 585           pages enlisted as being part of memory balloon devices avoids the
 586           scenario aforementioned and helps improving memory defragmentation.
 587
 588 #
 589 # support for memory compaction
 590 config COMPACTION
 591         bool "Allow for memory compaction"
 592         def_bool y
 593         select MIGRATION
 594         depends on MMU
 595         help
 596           Compaction is the only memory management component to form
 597           high order (larger physically contiguous) memory blocks
 598           reliably. The page allocator relies on compaction heavily and
 599           the lack of the feature can lead to unexpected OOM killer
 600           invocations for high order memory requests. You shouldn't
 601           disable this option unless there really is a strong reason for
 602           it and then we would be really interested to hear about that at
 603           linux-mm@kvack.org.
 604
 605 config COMPACT_UNEVICTABLE_DEFAULT
 606         int
 607         depends on COMPACTION
 608         default 0 if PREEMPT_RT
 609         default 1
 610
 611 #
 612 # support for free page reporting
 613 config PAGE_REPORTING
 614         bool "Free page reporting"
 615         def_bool n
 616         help
 617           Free page reporting allows for the incremental acquisition of
 618           free pages from the buddy allocator for the purpose of reporting
 619           those pages to another entity, such as a hypervisor, so that the
 620           memory can be freed within the host for other uses.
 621
 622 #
 623 # support for page migration
 624 #
 625 config MIGRATION
 626         bool "Page migration"
 627         def_bool y
 628         depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
 629         help
 630           Allows the migration of the physical location of pages of processes
 631           while the virtual addresses are not changed. This is useful in
 632           two situations. The first is on NUMA systems to put pages nearer
 633           to the processors accessing. The second is when allocating huge
 634           pages as migration can relocate pages to satisfy a huge page
 635           allocation instead of reclaiming.
 636
 637 config DEVICE_MIGRATION
 638         def_bool MIGRATION && ZONE_DEVICE
 639
 640 config ARCH_ENABLE_HUGEPAGE_MIGRATION
 641         bool
 642
 643 config ARCH_ENABLE_THP_MIGRATION
 644         bool
 645
 646 config HUGETLB_PAGE_SIZE_VARIABLE
 647         def_bool n
 648         help
 649           Allows the pageblock_order value to be dynamic instead of just standard
 650           HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available
 651           on a platform.
 652
 653           Note that the pageblock_order cannot exceed MAX_ORDER and will be
 654           clamped down to MAX_ORDER.
 655
 656 config CONTIG_ALLOC
 657         def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
 658
 659 config PHYS_ADDR_T_64BIT
 660         def_bool 64BIT
 661
 662 config BOUNCE
 663         bool "Enable bounce buffers"
 664         default y
 665         depends on BLOCK && MMU && HIGHMEM
 666         help
 667           Enable bounce buffers for devices that cannot access the full range of
 668           memory available to the CPU. Enabled by default when HIGHMEM is
 669           selected, but you may say n to override this.
 670
 671 config MMU_NOTIFIER
 672         bool
 673         select INTERVAL_TREE
 674
 675 config KSM
 676         bool "Enable KSM for page merging"
 677         depends on MMU
 678         select XXHASH
 679         help
 680           Enable Kernel Samepage Merging: KSM periodically scans those areas
 681           of an application's address space that an app has advised may be
 682           mergeable.  When it finds pages of identical content, it replaces
 683           the many instances by a single page with that content, so
 684           saving memory until one or another app needs to modify the content.
 685           Recommended for use with KVM, or with other duplicative applications.
 686           See Documentation/mm/ksm.rst for more information: KSM is inactive
 687           until a program has madvised that an area is MADV_MERGEABLE, and
 688           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 689
 690 config DEFAULT_MMAP_MIN_ADDR
 691         int "Low address space to protect from user allocation"
 692         depends on MMU
 693         default 4096
 694         help
 695           This is the portion of low virtual memory which should be protected
 696           from userspace allocation.  Keeping a user from writing to low pages
 697           can help reduce the impact of kernel NULL pointer bugs.
 698
 699           For most ia64, ppc64 and x86 users with lots of address space
 700           a value of 65536 is reasonable and should cause no problems.
 701           On arm and other archs it should not be higher than 32768.
 702           Programs which use vm86 functionality or have some need to map
 703           this low address space will need CAP_SYS_RAWIO or disable this
 704           protection by setting the value to 0.
 705
 706           This value can be changed after boot using the
 707           /proc/sys/vm/mmap_min_addr tunable.
 708
 709 config ARCH_SUPPORTS_MEMORY_FAILURE
 710         bool
 711
 712 config MEMORY_FAILURE
 713         depends on MMU
 714         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 715         bool "Enable recovery from hardware memory errors"
 716         select MEMORY_ISOLATION
 717         select RAS
 718         help
 719           Enables code to recover from some memory failures on systems
 720           with MCA recovery. This allows a system to continue running
 721           even when some of its memory has uncorrected errors. This requires
 722           special hardware support and typically ECC memory.
 723
 724 config HWPOISON_INJECT
 725         tristate "HWPoison pages injector"
 726         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 727         select PROC_PAGE_MONITOR
 728
 729 config NOMMU_INITIAL_TRIM_EXCESS
 730         int "Turn on mmap() excess space trimming before booting"
 731         depends on !MMU
 732         default 1
 733         help
 734           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 735           of memory on which to store mappings, but it can only ask the system
 736           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 737           more than it requires.  To deal with this, mmap() is able to trim off
 738           the excess and return it to the allocator.
 739
 740           If trimming is enabled, the excess is trimmed off and returned to the
 741           system allocator, which can cause extra fragmentation, particularly
 742           if there are a lot of transient processes.
 743
 744           If trimming is disabled, the excess is kept, but not used, which for
 745           long-term mappings means that the space is wasted.
 746
 747           Trimming can be dynamically controlled through a sysctl option
 748           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 749           excess pages there must be before trimming should occur, or zero if
 750           no trimming is to occur.
 751
 752           This option specifies the initial value of this option.  The default
 753           of 1 says that all excess pages should be trimmed.
 754
 755           See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
 756
 757 config ARCH_WANT_GENERAL_HUGETLB
 758         bool
 759
 760 config ARCH_WANTS_THP_SWAP
 761         def_bool n
 762
 763 menuconfig TRANSPARENT_HUGEPAGE
 764         bool "Transparent Hugepage Support"
 765         depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT
 766         select COMPACTION
 767         select XARRAY_MULTI
 768         help
 769           Transparent Hugepages allows the kernel to use huge pages and
 770           huge tlb transparently to the applications whenever possible.
 771           This feature can improve computing performance to certain
 772           applications by speeding up page faults during memory
 773           allocation, by reducing the number of tlb misses and by speeding
 774           up the pagetable walking.
 775
 776           If memory constrained on embedded, you may want to say N.
 777
 778 if TRANSPARENT_HUGEPAGE
 779
 780 choice
 781         prompt "Transparent Hugepage Support sysfs defaults"
 782         depends on TRANSPARENT_HUGEPAGE
 783         default TRANSPARENT_HUGEPAGE_ALWAYS
 784         help
 785           Selects the sysfs defaults for Transparent Hugepage Support.
 786
 787         config TRANSPARENT_HUGEPAGE_ALWAYS
 788                 bool "always"
 789         help
 790           Enabling Transparent Hugepage always, can increase the
 791           memory footprint of applications without a guaranteed
 792           benefit but it will work automatically for all applications.
 793
 794         config TRANSPARENT_HUGEPAGE_MADVISE
 795                 bool "madvise"
 796         help
 797           Enabling Transparent Hugepage madvise, will only provide a
 798           performance improvement benefit to the applications using
 799           madvise(MADV_HUGEPAGE) but it won't risk to increase the
 800           memory footprint of applications without a guaranteed
 801           benefit.
 802 endchoice
 803
 804 config THP_SWAP
 805         def_bool y
 806         depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT
 807         help
 808           Swap transparent huge pages in one piece, without splitting.
 809           XXX: For now, swap cluster backing transparent huge page
 810           will be split after swapout.
 811
 812           For selection by architectures with reasonable THP sizes.
 813
 814 config READ_ONLY_THP_FOR_FS
 815         bool "Read-only THP for filesystems (EXPERIMENTAL)"
 816         depends on TRANSPARENT_HUGEPAGE && SHMEM
 817
 818         help
 819           Allow khugepaged to put read-only file-backed pages in THP.
 820
 821           This is marked experimental because it is a new feature. Write
 822           support of file THPs will be developed in the next few release
 823           cycles.
 824
 825 endif # TRANSPARENT_HUGEPAGE
 826
 827 #
 828 # UP and nommu archs use km based percpu allocator
 829 #
 830 config NEED_PER_CPU_KM
 831         depends on !SMP || !MMU
 832         bool
 833         default y
 834
 835 config NEED_PER_CPU_EMBED_FIRST_CHUNK
 836         bool
 837
 838 config NEED_PER_CPU_PAGE_FIRST_CHUNK
 839         bool
 840
 841 config USE_PERCPU_NUMA_NODE_ID
 842         bool
 843
 844 config HAVE_SETUP_PER_CPU_AREA
 845         bool
 846
 847 config FRONTSWAP
 848         bool
 849
 850 config CMA
 851         bool "Contiguous Memory Allocator"
 852         depends on MMU
 853         select MIGRATION
 854         select MEMORY_ISOLATION
 855         help
 856           This enables the Contiguous Memory Allocator which allows other
 857           subsystems to allocate big physically-contiguous blocks of memory.
 858           CMA reserves a region of memory and allows only movable pages to
 859           be allocated from it. This way, the kernel can use the memory for
 860           pagecache and when a subsystem requests for contiguous area, the
 861           allocated pages are migrated away to serve the contiguous request.
 862
 863           If unsure, say "n".
 864
 865 config CMA_DEBUG
 866         bool "CMA debug messages (DEVELOPMENT)"
 867         depends on DEBUG_KERNEL && CMA
 868         help
 869           Turns on debug messages in CMA.  This produces KERN_DEBUG
 870           messages for every CMA call as well as various messages while
 871           processing calls such as dma_alloc_from_contiguous().
 872           This option does not affect warning and error messages.
 873
 874 config CMA_DEBUGFS
 875         bool "CMA debugfs interface"
 876         depends on CMA && DEBUG_FS
 877         help
 878           Turns on the DebugFS interface for CMA.
 879
 880 config CMA_SYSFS
 881         bool "CMA information through sysfs interface"
 882         depends on CMA && SYSFS
 883         help
 884           This option exposes some sysfs attributes to get information
 885           from CMA.
 886
 887 config CMA_AREAS
 888         int "Maximum count of the CMA areas"
 889         depends on CMA
 890         default 19 if NUMA
 891         default 7
 892         help
 893           CMA allows to create CMA areas for particular purpose, mainly,
 894           used as device private area. This parameter sets the maximum
 895           number of CMA area in the system.
 896
 897           If unsure, leave the default value "7" in UMA and "19" in NUMA.
 898
 899 config MEM_SOFT_DIRTY
 900         bool "Track memory changes"
 901         depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
 902         select PROC_PAGE_MONITOR
 903         help
 904           This option enables memory changes tracking by introducing a
 905           soft-dirty bit on pte-s. This bit it set when someone writes
 906           into a page just as regular dirty bit, but unlike the latter
 907           it can be cleared by hands.
 908
 909           See Documentation/admin-guide/mm/soft-dirty.rst for more details.
 910
 911 config GENERIC_EARLY_IOREMAP
 912         bool
 913
 914 config STACK_MAX_DEFAULT_SIZE_MB
 915         int "Default maximum user stack size for 32-bit processes (MB)"
 916         default 100
 917         range 8 2048
 918         depends on STACK_GROWSUP && (!64BIT || COMPAT)
 919         help
 920           This is the maximum stack size in Megabytes in the VM layout of 32-bit
 921           user processes when the stack grows upwards (currently only on parisc
 922           arch) when the RLIMIT_STACK hard limit is unlimited.
 923
 924           A sane initial value is 100 MB.
 925
 926 config DEFERRED_STRUCT_PAGE_INIT
 927         bool "Defer initialisation of struct pages to kthreads"
 928         depends on SPARSEMEM
 929         depends on !NEED_PER_CPU_KM
 930         depends on 64BIT
 931         select PADATA
 932         help
 933           Ordinarily all struct pages are initialised during early boot in a
 934           single thread. On very large machines this can take a considerable
 935           amount of time. If this option is set, large machines will bring up
 936           a subset of memmap at boot and then initialise the rest in parallel.
 937           This has a potential performance impact on tasks running early in the
 938           lifetime of the system until these kthreads finish the
 939           initialisation.
 940
 941 config PAGE_IDLE_FLAG
 942         bool
 943         select PAGE_EXTENSION if !64BIT
 944         help
 945           This adds PG_idle and PG_young flags to 'struct page'.  PTE Accessed
 946           bit writers can set the state of the bit in the flags so that PTE
 947           Accessed bit readers may avoid disturbance.
 948
 949 config IDLE_PAGE_TRACKING
 950         bool "Enable idle page tracking"
 951         depends on SYSFS && MMU
 952         select PAGE_IDLE_FLAG
 953         help
 954           This feature allows to estimate the amount of user pages that have
 955           not been touched during a given period of time. This information can
 956           be useful to tune memory cgroup limits and/or for job placement
 957           within a compute cluster.
 958
 959           See Documentation/admin-guide/mm/idle_page_tracking.rst for
 960           more details.
 961
 962 config ARCH_HAS_CACHE_LINE_SIZE
 963         bool
 964
 965 config ARCH_HAS_CURRENT_STACK_POINTER
 966         bool
 967         help
 968           In support of HARDENED_USERCOPY performing stack variable lifetime
 969           checking, an architecture-agnostic way to find the stack pointer
 970           is needed. Once an architecture defines an unsigned long global
 971           register alias named "current_stack_pointer", this config can be
 972           selected.
 973
 974 config ARCH_HAS_PTE_DEVMAP
 975         bool
 976
 977 config ARCH_HAS_ZONE_DMA_SET
 978         bool
 979
 980 config ZONE_DMA
 981         bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET
 982         default y if ARM64 || X86
 983
 984 config ZONE_DMA32
 985         bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET
 986         depends on !X86_32
 987         default y if ARM64
 988
 989 config ZONE_DEVICE
 990         bool "Device memory (pmem, HMM, etc...) hotplug support"
 991         depends on MEMORY_HOTPLUG
 992         depends on MEMORY_HOTREMOVE
 993         depends on SPARSEMEM_VMEMMAP
 994         depends on ARCH_HAS_PTE_DEVMAP
 995         select XARRAY_MULTI
 996
 997         help
 998           Device memory hotplug support allows for establishing pmem,
 999           or other device driver discovered memory regions, in the
1000           memmap. This allows pfn_to_page() lookups of otherwise
1001           "device-physical" addresses which is needed for using a DAX
1002           mapping in an O_DIRECT operation, among other things.
1003
1004           If FS_DAX is enabled, then say Y.
1005
1006 #
1007 # Helpers to mirror range of the CPU page tables of a process into device page
1008 # tables.
1009 #
1010 config HMM_MIRROR
1011         bool
1012         depends on MMU
1013
1014 config GET_FREE_REGION
1015         depends on SPARSEMEM
1016         bool
1017
1018 config DEVICE_PRIVATE
1019         bool "Unaddressable device memory (GPU memory, ...)"
1020         depends on ZONE_DEVICE
1021         select GET_FREE_REGION
1022
1023         help
1024           Allows creation of struct pages to represent unaddressable device
1025           memory; i.e., memory that is only accessible from the device (or
1026           group of devices). You likely also want to select HMM_MIRROR.
1027
1028 config VMAP_PFN
1029         bool
1030
1031 config ARCH_USES_HIGH_VMA_FLAGS
1032         bool
1033 config ARCH_HAS_PKEYS
1034         bool
1035
1036 config ARCH_USES_PG_ARCH_X
1037         bool
1038         help
1039           Enable the definition of PG_arch_x page flags with x > 1. Only
1040           suitable for 64-bit architectures with CONFIG_FLATMEM or
1041           CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be
1042           enough room for additional bits in page->flags.
1043
1044 config VM_EVENT_COUNTERS
1045         default y
1046         bool "Enable VM event counters for /proc/vmstat" if EXPERT
1047         help
1048           VM event counters are needed for event counts to be shown.
1049           This option allows the disabling of the VM event counters
1050           on EXPERT systems.  /proc/vmstat will only show page counts
1051           if VM event counters are disabled.
1052
1053 config PERCPU_STATS
1054         bool "Collect percpu memory statistics"
1055         help
1056           This feature collects and exposes statistics via debugfs. The
1057           information includes global and per chunk statistics, which can
1058           be used to help understand percpu memory usage.
1059
1060 config GUP_TEST
1061         bool "Enable infrastructure for get_user_pages()-related unit tests"
1062         depends on DEBUG_FS
1063         help
1064           Provides /sys/kernel/debug/gup_test, which in turn provides a way
1065           to make ioctl calls that can launch kernel-based unit tests for
1066           the get_user_pages*() and pin_user_pages*() family of API calls.
1067
1068           These tests include benchmark testing of the _fast variants of
1069           get_user_pages*() and pin_user_pages*(), as well as smoke tests of
1070           the non-_fast variants.
1071
1072           There is also a sub-test that allows running dump_page() on any
1073           of up to eight pages (selected by command line args) within the
1074           range of user-space addresses. These pages are either pinned via
1075           pin_user_pages*(), or pinned via get_user_pages*(), as specified
1076           by other command line arguments.
1077
1078           See tools/testing/selftests/mm/gup_test.c
1079
1080 comment "GUP_TEST needs to have DEBUG_FS enabled"
1081         depends on !GUP_TEST && !DEBUG_FS
1082
1083 config GUP_GET_PXX_LOW_HIGH
1084         bool
1085
1086 config DMAPOOL_TEST
1087         tristate "Enable a module to run time tests on dma_pool"
1088         depends on HAS_DMA
1089         help
1090           Provides a test module that will allocate and free many blocks of
1091           various sizes and report how long it takes. This is intended to
1092           provide a consistent way to measure how changes to the
1093           dma_pool_alloc/free routines affect performance.
1094
1095 config ARCH_HAS_PTE_SPECIAL
1096         bool
1097
1098 #
1099 # Some architectures require a special hugepage directory format that is
1100 # required to support multiple hugepage sizes. For example a4fe3ce76
1101 # "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
1102 # introduced it on powerpc.  This allows for a more flexible hugepage
1103 # pagetable layouts.
1104 #
1105 config ARCH_HAS_HUGEPD
1106         bool
1107
1108 config MAPPING_DIRTY_HELPERS
1109         bool
1110
1111 config KMAP_LOCAL
1112         bool
1113
1114 config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY
1115         bool
1116
1117 # struct io_mapping based helper.  Selected by drivers that need them
1118 config IO_MAPPING
1119         bool
1120
1121 config SECRETMEM
1122         default y
1123         bool "Enable memfd_secret() system call" if EXPERT
1124         depends on ARCH_HAS_SET_DIRECT_MAP
1125         help
1126           Enable the memfd_secret() system call with the ability to create
1127           memory areas visible only in the context of the owning process and
1128           not mapped to other processes and other kernel page tables.
1129
1130 config ANON_VMA_NAME
1131         bool "Anonymous VMA name support"
1132         depends on PROC_FS && ADVISE_SYSCALLS && MMU
1133
1134         help
1135           Allow naming anonymous virtual memory areas.
1136
1137           This feature allows assigning names to virtual memory areas. Assigned
1138           names can be later retrieved from /proc/pid/maps and /proc/pid/smaps
1139           and help identifying individual anonymous memory areas.
1140           Assigning a name to anonymous virtual memory area might prevent that
1141           area from being merged with adjacent virtual memory areas due to the
1142           difference in their name.
1143
1144 config USERFAULTFD
1145         bool "Enable userfaultfd() system call"
1146         depends on MMU
1147         help
1148           Enable the userfaultfd() system call that allows to intercept and
1149           handle page faults in userland.
1150
1151 config HAVE_ARCH_USERFAULTFD_WP
1152         bool
1153         help
1154           Arch has userfaultfd write protection support
1155
1156 config HAVE_ARCH_USERFAULTFD_MINOR
1157         bool
1158         help
1159           Arch has userfaultfd minor fault support
1160
1161 config PTE_MARKER_UFFD_WP
1162         bool "Userfaultfd write protection support for shmem/hugetlbfs"
1163         default y
1164         depends on HAVE_ARCH_USERFAULTFD_WP
1165
1166         help
1167           Allows to create marker PTEs for userfaultfd write protection
1168           purposes.  It is required to enable userfaultfd write protection on
1169           file-backed memory types like shmem and hugetlbfs.
1170
1171 # multi-gen LRU {
1172 config LRU_GEN
1173         bool "Multi-Gen LRU"
1174         depends on MMU
1175         # make sure folio->flags has enough spare bits
1176         depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP
1177         help
1178           A high performance LRU implementation to overcommit memory. See
1179           Documentation/admin-guide/mm/multigen_lru.rst for details.
1180
1181 config LRU_GEN_ENABLED
1182         bool "Enable by default"
1183         depends on LRU_GEN
1184         help
1185           This option enables the multi-gen LRU by default.
1186
1187 config LRU_GEN_STATS
1188         bool "Full stats for debugging"
1189         depends on LRU_GEN
1190         help
1191           Do not enable this option unless you plan to look at historical stats
1192           from evicted generations for debugging purpose.
1193
1194           This option has a per-memcg and per-node memory overhead.
1195 # }
1196
1197 config ARCH_SUPPORTS_PER_VMA_LOCK
1198        def_bool n
1199
1200 config PER_VMA_LOCK
1201         def_bool y
1202         depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP
1203         help
1204           Allow per-vma locking during page fault handling.
1205
1206           This feature allows locking each virtual memory area separately when
1207           handling page faults instead of taking mmap_lock.
1208
1209 source "mm/damon/Kconfig"
1210
1211 endmenu