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