mm/Kconfig

   1 # SPDX-License-Identifier: GPL-2.0-only
   2
   3 menu "Memory Management options"
   4
   5 config SELECT_MEMORY_MODEL
   6         def_bool y
   7         depends on ARCH_SELECT_MEMORY_MODEL
   8
   9 choice
  10         prompt "Memory model"
  11         depends on SELECT_MEMORY_MODEL
  12         default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
  13         default FLATMEM_MANUAL
  14         help
  15           This option allows you to change some of the ways that
  16           Linux manages its memory internally. Most users will
  17           only have one option here selected by the architecture
  18           configuration. This is normal.
  19
  20 config FLATMEM_MANUAL
  21         bool "Flat Memory"
  22         depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE
  23         help
  24           This option is best suited for non-NUMA systems with
  25           flat address space. The FLATMEM is the most efficient
  26           system in terms of performance and resource consumption
  27           and it is the best option for smaller systems.
  28
  29           For systems that have holes in their physical address
  30           spaces and for features like NUMA and memory hotplug,
  31           choose "Sparse Memory".
  32
  33           If unsure, choose this option (Flat Memory) over any other.
  34
  35 config SPARSEMEM_MANUAL
  36         bool "Sparse Memory"
  37         depends on ARCH_SPARSEMEM_ENABLE
  38         help
  39           This will be the only option for some systems, including
  40           memory hot-plug systems.  This is normal.
  41
  42           This option provides efficient support for systems with
  43           holes is their physical address space and allows memory
  44           hot-plug and hot-remove.
  45
  46           If unsure, choose "Flat Memory" over this option.
  47
  48 endchoice
  49
  50 config SPARSEMEM
  51         def_bool y
  52         depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
  53
  54 config FLATMEM
  55         def_bool y
  56         depends on !SPARSEMEM || FLATMEM_MANUAL
  57
  58 #
  59 # SPARSEMEM_EXTREME (which is the default) does some bootmem
  60 # allocations when sparse_init() is called.  If this cannot
  61 # be done on your architecture, select this option.  However,
  62 # statically allocating the mem_section[] array can potentially
  63 # consume vast quantities of .bss, so be careful.
  64 #
  65 # This option will also potentially produce smaller runtime code
  66 # with gcc 3.4 and later.
  67 #
  68 config SPARSEMEM_STATIC
  69         bool
  70
  71 #
  72 # Architecture platforms which require a two level mem_section in SPARSEMEM
  73 # must select this option. This is usually for architecture platforms with
  74 # an extremely sparse physical address space.
  75 #
  76 config SPARSEMEM_EXTREME
  77         def_bool y
  78         depends on SPARSEMEM && !SPARSEMEM_STATIC
  79
  80 config SPARSEMEM_VMEMMAP_ENABLE
  81         bool
  82
  83 config SPARSEMEM_VMEMMAP
  84         bool "Sparse Memory virtual memmap"
  85         depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
  86         default y
  87         help
  88           SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
  89           pfn_to_page and page_to_pfn operations.  This is the most
  90           efficient option when sufficient kernel resources are available.
  91
  92 config HAVE_MEMBLOCK_PHYS_MAP
  93         bool
  94
  95 config HAVE_FAST_GUP
  96         depends on MMU
  97         bool
  98
  99 # Don't discard allocated memory used to track "memory" and "reserved" memblocks
 100 # after early boot, so it can still be used to test for validity of memory.
 101 # Also, memblocks are updated with memory hot(un)plug.
 102 config ARCH_KEEP_MEMBLOCK
 103         bool
 104
 105 # Keep arch NUMA mapping infrastructure post-init.
 106 config NUMA_KEEP_MEMINFO
 107         bool
 108
 109 config MEMORY_ISOLATION
 110         bool
 111
 112 # IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked
 113 # IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via
 114 # /dev/mem.
 115 config EXCLUSIVE_SYSTEM_RAM
 116         def_bool y
 117         depends on !DEVMEM || STRICT_DEVMEM
 118
 119 #
 120 # Only be set on architectures that have completely implemented memory hotplug
 121 # feature. If you are not sure, don't touch it.
 122 #
 123 config HAVE_BOOTMEM_INFO_NODE
 124         def_bool n
 125
 126 config ARCH_ENABLE_MEMORY_HOTPLUG
 127         bool
 128
 129 # eventually, we can have this option just 'select SPARSEMEM'
 130 config MEMORY_HOTPLUG
 131         bool "Allow for memory hot-add"
 132         select MEMORY_ISOLATION
 133         depends on SPARSEMEM
 134         depends on ARCH_ENABLE_MEMORY_HOTPLUG
 135         depends on 64BIT
 136         select NUMA_KEEP_MEMINFO if NUMA
 137
 138 config MEMORY_HOTPLUG_DEFAULT_ONLINE
 139         bool "Online the newly added memory blocks by default"
 140         depends on MEMORY_HOTPLUG
 141         help
 142           This option sets the default policy setting for memory hotplug
 143           onlining policy (/sys/devices/system/memory/auto_online_blocks) which
 144           determines what happens to newly added memory regions. Policy setting
 145           can always be changed at runtime.
 146           See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
 147
 148           Say Y here if you want all hot-plugged memory blocks to appear in
 149           'online' state by default.
 150           Say N here if you want the default policy to keep all hot-plugged
 151           memory blocks in 'offline' state.
 152
 153 config ARCH_ENABLE_MEMORY_HOTREMOVE
 154         bool
 155
 156 config MEMORY_HOTREMOVE
 157         bool "Allow for memory hot remove"
 158         select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
 159         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 160         depends on MIGRATION
 161
 162 config MHP_MEMMAP_ON_MEMORY
 163         def_bool y
 164         depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
 165         depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
 166
 167 # Heavily threaded applications may benefit from splitting the mm-wide
 168 # page_table_lock, so that faults on different parts of the user address
 169 # space can be handled with less contention: split it at this NR_CPUS.
 170 # Default to 4 for wider testing, though 8 might be more appropriate.
 171 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 172 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 173 # SPARC32 allocates multiple pte tables within a single page, and therefore
 174 # a per-page lock leads to problems when multiple tables need to be locked
 175 # at the same time (e.g. copy_page_range()).
 176 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
 177 #
 178 config SPLIT_PTLOCK_CPUS
 179         int
 180         default "999999" if !MMU
 181         default "999999" if ARM && !CPU_CACHE_VIPT
 182         default "999999" if PARISC && !PA20
 183         default "999999" if SPARC32
 184         default "4"
 185
 186 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
 187         bool
 188
 189 #
 190 # support for memory balloon
 191 config MEMORY_BALLOON
 192         bool
 193
 194 #
 195 # support for memory balloon compaction
 196 config BALLOON_COMPACTION
 197         bool "Allow for balloon memory compaction/migration"
 198         def_bool y
 199         depends on COMPACTION && MEMORY_BALLOON
 200         help
 201           Memory fragmentation introduced by ballooning might reduce
 202           significantly the number of 2MB contiguous memory blocks that can be
 203           used within a guest, thus imposing performance penalties associated
 204           with the reduced number of transparent huge pages that could be used
 205           by the guest workload. Allowing the compaction & migration for memory
 206           pages enlisted as being part of memory balloon devices avoids the
 207           scenario aforementioned and helps improving memory defragmentation.
 208
 209 #
 210 # support for memory compaction
 211 config COMPACTION
 212         bool "Allow for memory compaction"
 213         def_bool y
 214         select MIGRATION
 215         depends on MMU
 216         help
 217           Compaction is the only memory management component to form
 218           high order (larger physically contiguous) memory blocks
 219           reliably. The page allocator relies on compaction heavily and
 220           the lack of the feature can lead to unexpected OOM killer
 221           invocations for high order memory requests. You shouldn't
 222           disable this option unless there really is a strong reason for
 223           it and then we would be really interested to hear about that at
 224           linux-mm@kvack.org.
 225
 226 #
 227 # support for free page reporting
 228 config PAGE_REPORTING
 229         bool "Free page reporting"
 230         def_bool n
 231         help
 232           Free page reporting allows for the incremental acquisition of
 233           free pages from the buddy allocator for the purpose of reporting
 234           those pages to another entity, such as a hypervisor, so that the
 235           memory can be freed within the host for other uses.
 236
 237 #
 238 # support for page migration
 239 #
 240 config MIGRATION
 241         bool "Page migration"
 242         def_bool y
 243         depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
 244         help
 245           Allows the migration of the physical location of pages of processes
 246           while the virtual addresses are not changed. This is useful in
 247           two situations. The first is on NUMA systems to put pages nearer
 248           to the processors accessing. The second is when allocating huge
 249           pages as migration can relocate pages to satisfy a huge page
 250           allocation instead of reclaiming.
 251
 252 config ARCH_ENABLE_HUGEPAGE_MIGRATION
 253         bool
 254
 255 config ARCH_ENABLE_THP_MIGRATION
 256         bool
 257
 258 config HUGETLB_PAGE_SIZE_VARIABLE
 259         def_bool n
 260         help
 261           Allows the pageblock_order value to be dynamic instead of just standard
 262           HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available
 263           on a platform.
 264
 265 config CONTIG_ALLOC
 266         def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
 267
 268 config PHYS_ADDR_T_64BIT
 269         def_bool 64BIT
 270
 271 config BOUNCE
 272         bool "Enable bounce buffers"
 273         default y
 274         depends on BLOCK && MMU && HIGHMEM
 275         help
 276           Enable bounce buffers for devices that cannot access the full range of
 277           memory available to the CPU. Enabled by default when HIGHMEM is
 278           selected, but you may say n to override this.
 279
 280 config VIRT_TO_BUS
 281         bool
 282         help
 283           An architecture should select this if it implements the
 284           deprecated interface virt_to_bus().  All new architectures
 285           should probably not select this.
 286
 287
 288 config MMU_NOTIFIER
 289         bool
 290         select SRCU
 291         select INTERVAL_TREE
 292
 293 config KSM
 294         bool "Enable KSM for page merging"
 295         depends on MMU
 296         select XXHASH
 297         help
 298           Enable Kernel Samepage Merging: KSM periodically scans those areas
 299           of an application's address space that an app has advised may be
 300           mergeable.  When it finds pages of identical content, it replaces
 301           the many instances by a single page with that content, so
 302           saving memory until one or another app needs to modify the content.
 303           Recommended for use with KVM, or with other duplicative applications.
 304           See Documentation/vm/ksm.rst for more information: KSM is inactive
 305           until a program has madvised that an area is MADV_MERGEABLE, and
 306           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 307
 308 config DEFAULT_MMAP_MIN_ADDR
 309         int "Low address space to protect from user allocation"
 310         depends on MMU
 311         default 4096
 312         help
 313           This is the portion of low virtual memory which should be protected
 314           from userspace allocation.  Keeping a user from writing to low pages
 315           can help reduce the impact of kernel NULL pointer bugs.
 316
 317           For most ia64, ppc64 and x86 users with lots of address space
 318           a value of 65536 is reasonable and should cause no problems.
 319           On arm and other archs it should not be higher than 32768.
 320           Programs which use vm86 functionality or have some need to map
 321           this low address space will need CAP_SYS_RAWIO or disable this
 322           protection by setting the value to 0.
 323
 324           This value can be changed after boot using the
 325           /proc/sys/vm/mmap_min_addr tunable.
 326
 327 config ARCH_SUPPORTS_MEMORY_FAILURE
 328         bool
 329
 330 config MEMORY_FAILURE
 331         depends on MMU
 332         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 333         bool "Enable recovery from hardware memory errors"
 334         select MEMORY_ISOLATION
 335         select RAS
 336         help
 337           Enables code to recover from some memory failures on systems
 338           with MCA recovery. This allows a system to continue running
 339           even when some of its memory has uncorrected errors. This requires
 340           special hardware support and typically ECC memory.
 341
 342 config HWPOISON_INJECT
 343         tristate "HWPoison pages injector"
 344         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 345         select PROC_PAGE_MONITOR
 346
 347 config NOMMU_INITIAL_TRIM_EXCESS
 348         int "Turn on mmap() excess space trimming before booting"
 349         depends on !MMU
 350         default 1
 351         help
 352           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 353           of memory on which to store mappings, but it can only ask the system
 354           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 355           more than it requires.  To deal with this, mmap() is able to trim off
 356           the excess and return it to the allocator.
 357
 358           If trimming is enabled, the excess is trimmed off and returned to the
 359           system allocator, which can cause extra fragmentation, particularly
 360           if there are a lot of transient processes.
 361
 362           If trimming is disabled, the excess is kept, but not used, which for
 363           long-term mappings means that the space is wasted.
 364
 365           Trimming can be dynamically controlled through a sysctl option
 366           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 367           excess pages there must be before trimming should occur, or zero if
 368           no trimming is to occur.
 369
 370           This option specifies the initial value of this option.  The default
 371           of 1 says that all excess pages should be trimmed.
 372
 373           See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
 374
 375 config TRANSPARENT_HUGEPAGE
 376         bool "Transparent Hugepage Support"
 377         depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT
 378         select COMPACTION
 379         select XARRAY_MULTI
 380         help
 381           Transparent Hugepages allows the kernel to use huge pages and
 382           huge tlb transparently to the applications whenever possible.
 383           This feature can improve computing performance to certain
 384           applications by speeding up page faults during memory
 385           allocation, by reducing the number of tlb misses and by speeding
 386           up the pagetable walking.
 387
 388           If memory constrained on embedded, you may want to say N.
 389
 390 choice
 391         prompt "Transparent Hugepage Support sysfs defaults"
 392         depends on TRANSPARENT_HUGEPAGE
 393         default TRANSPARENT_HUGEPAGE_ALWAYS
 394         help
 395           Selects the sysfs defaults for Transparent Hugepage Support.
 396
 397         config TRANSPARENT_HUGEPAGE_ALWAYS
 398                 bool "always"
 399         help
 400           Enabling Transparent Hugepage always, can increase the
 401           memory footprint of applications without a guaranteed
 402           benefit but it will work automatically for all applications.
 403
 404         config TRANSPARENT_HUGEPAGE_MADVISE
 405                 bool "madvise"
 406         help
 407           Enabling Transparent Hugepage madvise, will only provide a
 408           performance improvement benefit to the applications using
 409           madvise(MADV_HUGEPAGE) but it won't risk to increase the
 410           memory footprint of applications without a guaranteed
 411           benefit.
 412 endchoice
 413
 414 config ARCH_WANTS_THP_SWAP
 415         def_bool n
 416
 417 config THP_SWAP
 418         def_bool y
 419         depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
 420         help
 421           Swap transparent huge pages in one piece, without splitting.
 422           XXX: For now, swap cluster backing transparent huge page
 423           will be split after swapout.
 424
 425           For selection by architectures with reasonable THP sizes.
 426
 427 #
 428 # UP and nommu archs use km based percpu allocator
 429 #
 430 config NEED_PER_CPU_KM
 431         depends on !SMP || !MMU
 432         bool
 433         default y
 434
 435 config NEED_PER_CPU_EMBED_FIRST_CHUNK
 436         bool
 437
 438 config NEED_PER_CPU_PAGE_FIRST_CHUNK
 439         bool
 440
 441 config USE_PERCPU_NUMA_NODE_ID
 442         bool
 443
 444 config HAVE_SETUP_PER_CPU_AREA
 445         bool
 446
 447 config CLEANCACHE
 448         bool "Enable cleancache driver to cache clean pages if tmem is present"
 449         help
 450           Cleancache can be thought of as a page-granularity victim cache
 451           for clean pages that the kernel's pageframe replacement algorithm
 452           (PFRA) would like to keep around, but can't since there isn't enough
 453           memory.  So when the PFRA "evicts" a page, it first attempts to use
 454           cleancache code to put the data contained in that page into
 455           "transcendent memory", memory that is not directly accessible or
 456           addressable by the kernel and is of unknown and possibly
 457           time-varying size.  And when a cleancache-enabled
 458           filesystem wishes to access a page in a file on disk, it first
 459           checks cleancache to see if it already contains it; if it does,
 460           the page is copied into the kernel and a disk access is avoided.
 461           When a transcendent memory driver is available (such as zcache or
 462           Xen transcendent memory), a significant I/O reduction
 463           may be achieved.  When none is available, all cleancache calls
 464           are reduced to a single pointer-compare-against-NULL resulting
 465           in a negligible performance hit.
 466
 467           If unsure, say Y to enable cleancache
 468
 469 config FRONTSWAP
 470         bool "Enable frontswap to cache swap pages if tmem is present"
 471         depends on SWAP
 472         help
 473           Frontswap is so named because it can be thought of as the opposite
 474           of a "backing" store for a swap device.  The data is stored into
 475           "transcendent memory", memory that is not directly accessible or
 476           addressable by the kernel and is of unknown and possibly
 477           time-varying size.  When space in transcendent memory is available,
 478           a significant swap I/O reduction may be achieved.  When none is
 479           available, all frontswap calls are reduced to a single pointer-
 480           compare-against-NULL resulting in a negligible performance hit
 481           and swap data is stored as normal on the matching swap device.
 482
 483           If unsure, say Y to enable frontswap.
 484
 485 config CMA
 486         bool "Contiguous Memory Allocator"
 487         depends on MMU
 488         select MIGRATION
 489         select MEMORY_ISOLATION
 490         help
 491           This enables the Contiguous Memory Allocator which allows other
 492           subsystems to allocate big physically-contiguous blocks of memory.
 493           CMA reserves a region of memory and allows only movable pages to
 494           be allocated from it. This way, the kernel can use the memory for
 495           pagecache and when a subsystem requests for contiguous area, the
 496           allocated pages are migrated away to serve the contiguous request.
 497
 498           If unsure, say "n".
 499
 500 config CMA_DEBUG
 501         bool "CMA debug messages (DEVELOPMENT)"
 502         depends on DEBUG_KERNEL && CMA
 503         help
 504           Turns on debug messages in CMA.  This produces KERN_DEBUG
 505           messages for every CMA call as well as various messages while
 506           processing calls such as dma_alloc_from_contiguous().
 507           This option does not affect warning and error messages.
 508
 509 config CMA_DEBUGFS
 510         bool "CMA debugfs interface"
 511         depends on CMA && DEBUG_FS
 512         help
 513           Turns on the DebugFS interface for CMA.
 514
 515 config CMA_SYSFS
 516         bool "CMA information through sysfs interface"
 517         depends on CMA && SYSFS
 518         help
 519           This option exposes some sysfs attributes to get information
 520           from CMA.
 521
 522 config CMA_AREAS
 523         int "Maximum count of the CMA areas"
 524         depends on CMA
 525         default 19 if NUMA
 526         default 7
 527         help
 528           CMA allows to create CMA areas for particular purpose, mainly,
 529           used as device private area. This parameter sets the maximum
 530           number of CMA area in the system.
 531
 532           If unsure, leave the default value "7" in UMA and "19" in NUMA.
 533
 534 config MEM_SOFT_DIRTY
 535         bool "Track memory changes"
 536         depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
 537         select PROC_PAGE_MONITOR
 538         help
 539           This option enables memory changes tracking by introducing a
 540           soft-dirty bit on pte-s. This bit it set when someone writes
 541           into a page just as regular dirty bit, but unlike the latter
 542           it can be cleared by hands.
 543
 544           See Documentation/admin-guide/mm/soft-dirty.rst for more details.
 545
 546 config ZSWAP
 547         bool "Compressed cache for swap pages (EXPERIMENTAL)"
 548         depends on FRONTSWAP && CRYPTO=y
 549         select ZPOOL
 550         help
 551           A lightweight compressed cache for swap pages.  It takes
 552           pages that are in the process of being swapped out and attempts to
 553           compress them into a dynamically allocated RAM-based memory pool.
 554           This can result in a significant I/O reduction on swap device and,
 555           in the case where decompressing from RAM is faster that swap device
 556           reads, can also improve workload performance.
 557
 558           This is marked experimental because it is a new feature (as of
 559           v3.11) that interacts heavily with memory reclaim.  While these
 560           interactions don't cause any known issues on simple memory setups,
 561           they have not be fully explored on the large set of potential
 562           configurations and workloads that exist.
 563
 564 choice
 565         prompt "Compressed cache for swap pages default compressor"
 566         depends on ZSWAP
 567         default ZSWAP_COMPRESSOR_DEFAULT_LZO
 568         help
 569           Selects the default compression algorithm for the compressed cache
 570           for swap pages.
 571
 572           For an overview what kind of performance can be expected from
 573           a particular compression algorithm please refer to the benchmarks
 574           available at the following LWN page:
 575           https://lwn.net/Articles/751795/
 576
 577           If in doubt, select 'LZO'.
 578
 579           The selection made here can be overridden by using the kernel
 580           command line 'zswap.compressor=' option.
 581
 582 config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
 583         bool "Deflate"
 584         select CRYPTO_DEFLATE
 585         help
 586           Use the Deflate algorithm as the default compression algorithm.
 587
 588 config ZSWAP_COMPRESSOR_DEFAULT_LZO
 589         bool "LZO"
 590         select CRYPTO_LZO
 591         help
 592           Use the LZO algorithm as the default compression algorithm.
 593
 594 config ZSWAP_COMPRESSOR_DEFAULT_842
 595         bool "842"
 596         select CRYPTO_842
 597         help
 598           Use the 842 algorithm as the default compression algorithm.
 599
 600 config ZSWAP_COMPRESSOR_DEFAULT_LZ4
 601         bool "LZ4"
 602         select CRYPTO_LZ4
 603         help
 604           Use the LZ4 algorithm as the default compression algorithm.
 605
 606 config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
 607         bool "LZ4HC"
 608         select CRYPTO_LZ4HC
 609         help
 610           Use the LZ4HC algorithm as the default compression algorithm.
 611
 612 config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
 613         bool "zstd"
 614         select CRYPTO_ZSTD
 615         help
 616           Use the zstd algorithm as the default compression algorithm.
 617 endchoice
 618
 619 config ZSWAP_COMPRESSOR_DEFAULT
 620        string
 621        depends on ZSWAP
 622        default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
 623        default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
 624        default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
 625        default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
 626        default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
 627        default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
 628        default ""
 629
 630 choice
 631         prompt "Compressed cache for swap pages default allocator"
 632         depends on ZSWAP
 633         default ZSWAP_ZPOOL_DEFAULT_ZBUD
 634         help
 635           Selects the default allocator for the compressed cache for
 636           swap pages.
 637           The default is 'zbud' for compatibility, however please do
 638           read the description of each of the allocators below before
 639           making a right choice.
 640
 641           The selection made here can be overridden by using the kernel
 642           command line 'zswap.zpool=' option.
 643
 644 config ZSWAP_ZPOOL_DEFAULT_ZBUD
 645         bool "zbud"
 646         select ZBUD
 647         help
 648           Use the zbud allocator as the default allocator.
 649
 650 config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
 651         bool "z3fold"
 652         select Z3FOLD
 653         help
 654           Use the z3fold allocator as the default allocator.
 655
 656 config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
 657         bool "zsmalloc"
 658         select ZSMALLOC
 659         help
 660           Use the zsmalloc allocator as the default allocator.
 661 endchoice
 662
 663 config ZSWAP_ZPOOL_DEFAULT
 664        string
 665        depends on ZSWAP
 666        default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
 667        default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
 668        default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
 669        default ""
 670
 671 config ZSWAP_DEFAULT_ON
 672         bool "Enable the compressed cache for swap pages by default"
 673         depends on ZSWAP
 674         help
 675           If selected, the compressed cache for swap pages will be enabled
 676           at boot, otherwise it will be disabled.
 677
 678           The selection made here can be overridden by using the kernel
 679           command line 'zswap.enabled=' option.
 680
 681 config ZPOOL
 682         tristate "Common API for compressed memory storage"
 683         help
 684           Compressed memory storage API.  This allows using either zbud or
 685           zsmalloc.
 686
 687 config ZBUD
 688         tristate "Low (Up to 2x) density storage for compressed pages"
 689         depends on ZPOOL
 690         help
 691           A special purpose allocator for storing compressed pages.
 692           It is designed to store up to two compressed pages per physical
 693           page.  While this design limits storage density, it has simple and
 694           deterministic reclaim properties that make it preferable to a higher
 695           density approach when reclaim will be used.
 696
 697 config Z3FOLD
 698         tristate "Up to 3x density storage for compressed pages"
 699         depends on ZPOOL
 700         help
 701           A special purpose allocator for storing compressed pages.
 702           It is designed to store up to three compressed pages per physical
 703           page. It is a ZBUD derivative so the simplicity and determinism are
 704           still there.
 705
 706 config ZSMALLOC
 707         tristate "Memory allocator for compressed pages"
 708         depends on MMU
 709         help
 710           zsmalloc is a slab-based memory allocator designed to store
 711           compressed RAM pages.  zsmalloc uses virtual memory mapping
 712           in order to reduce fragmentation.  However, this results in a
 713           non-standard allocator interface where a handle, not a pointer, is
 714           returned by an alloc().  This handle must be mapped in order to
 715           access the allocated space.
 716
 717 config ZSMALLOC_STAT
 718         bool "Export zsmalloc statistics"
 719         depends on ZSMALLOC
 720         select DEBUG_FS
 721         help
 722           This option enables code in the zsmalloc to collect various
 723           statistics about what's happening in zsmalloc and exports that
 724           information to userspace via debugfs.
 725           If unsure, say N.
 726
 727 config GENERIC_EARLY_IOREMAP
 728         bool
 729
 730 config STACK_MAX_DEFAULT_SIZE_MB
 731         int "Default maximum user stack size for 32-bit processes (MB)"
 732         default 100
 733         range 8 2048
 734         depends on STACK_GROWSUP && (!64BIT || COMPAT)
 735         help
 736           This is the maximum stack size in Megabytes in the VM layout of 32-bit
 737           user processes when the stack grows upwards (currently only on parisc
 738           arch) when the RLIMIT_STACK hard limit is unlimited.
 739
 740           A sane initial value is 100 MB.
 741
 742 config DEFERRED_STRUCT_PAGE_INIT
 743         bool "Defer initialisation of struct pages to kthreads"
 744         depends on SPARSEMEM
 745         depends on !NEED_PER_CPU_KM
 746         depends on 64BIT
 747         select PADATA
 748         help
 749           Ordinarily all struct pages are initialised during early boot in a
 750           single thread. On very large machines this can take a considerable
 751           amount of time. If this option is set, large machines will bring up
 752           a subset of memmap at boot and then initialise the rest in parallel.
 753           This has a potential performance impact on tasks running early in the
 754           lifetime of the system until these kthreads finish the
 755           initialisation.
 756
 757 config PAGE_IDLE_FLAG
 758         bool
 759         select PAGE_EXTENSION if !64BIT
 760         help
 761           This adds PG_idle and PG_young flags to 'struct page'.  PTE Accessed
 762           bit writers can set the state of the bit in the flags so that PTE
 763           Accessed bit readers may avoid disturbance.
 764
 765 config IDLE_PAGE_TRACKING
 766         bool "Enable idle page tracking"
 767         depends on SYSFS && MMU
 768         select PAGE_IDLE_FLAG
 769         help
 770           This feature allows to estimate the amount of user pages that have
 771           not been touched during a given period of time. This information can
 772           be useful to tune memory cgroup limits and/or for job placement
 773           within a compute cluster.
 774
 775           See Documentation/admin-guide/mm/idle_page_tracking.rst for
 776           more details.
 777
 778 config ARCH_HAS_CACHE_LINE_SIZE
 779         bool
 780
 781 config ARCH_HAS_PTE_DEVMAP
 782         bool
 783
 784 config ARCH_HAS_ZONE_DMA_SET
 785         bool
 786
 787 config ZONE_DMA
 788         bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET
 789         default y if ARM64 || X86
 790
 791 config ZONE_DMA32
 792         bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET
 793         depends on !X86_32
 794         default y if ARM64
 795
 796 config ZONE_DEVICE
 797         bool "Device memory (pmem, HMM, etc...) hotplug support"
 798         depends on MEMORY_HOTPLUG
 799         depends on MEMORY_HOTREMOVE
 800         depends on SPARSEMEM_VMEMMAP
 801         depends on ARCH_HAS_PTE_DEVMAP
 802         select XARRAY_MULTI
 803
 804         help
 805           Device memory hotplug support allows for establishing pmem,
 806           or other device driver discovered memory regions, in the
 807           memmap. This allows pfn_to_page() lookups of otherwise
 808           "device-physical" addresses which is needed for using a DAX
 809           mapping in an O_DIRECT operation, among other things.
 810
 811           If FS_DAX is enabled, then say Y.
 812
 813 config DEV_PAGEMAP_OPS
 814         bool
 815
 816 #
 817 # Helpers to mirror range of the CPU page tables of a process into device page
 818 # tables.
 819 #
 820 config HMM_MIRROR
 821         bool
 822         depends on MMU
 823
 824 config DEVICE_PRIVATE
 825         bool "Unaddressable device memory (GPU memory, ...)"
 826         depends on ZONE_DEVICE
 827         select DEV_PAGEMAP_OPS
 828
 829         help
 830           Allows creation of struct pages to represent unaddressable device
 831           memory; i.e., memory that is only accessible from the device (or
 832           group of devices). You likely also want to select HMM_MIRROR.
 833
 834 config VMAP_PFN
 835         bool
 836
 837 config ARCH_USES_HIGH_VMA_FLAGS
 838         bool
 839 config ARCH_HAS_PKEYS
 840         bool
 841
 842 config PERCPU_STATS
 843         bool "Collect percpu memory statistics"
 844         help
 845           This feature collects and exposes statistics via debugfs. The
 846           information includes global and per chunk statistics, which can
 847           be used to help understand percpu memory usage.
 848
 849 config GUP_TEST
 850         bool "Enable infrastructure for get_user_pages()-related unit tests"
 851         depends on DEBUG_FS
 852         help
 853           Provides /sys/kernel/debug/gup_test, which in turn provides a way
 854           to make ioctl calls that can launch kernel-based unit tests for
 855           the get_user_pages*() and pin_user_pages*() family of API calls.
 856
 857           These tests include benchmark testing of the _fast variants of
 858           get_user_pages*() and pin_user_pages*(), as well as smoke tests of
 859           the non-_fast variants.
 860
 861           There is also a sub-test that allows running dump_page() on any
 862           of up to eight pages (selected by command line args) within the
 863           range of user-space addresses. These pages are either pinned via
 864           pin_user_pages*(), or pinned via get_user_pages*(), as specified
 865           by other command line arguments.
 866
 867           See tools/testing/selftests/vm/gup_test.c
 868
 869 comment "GUP_TEST needs to have DEBUG_FS enabled"
 870         depends on !GUP_TEST && !DEBUG_FS
 871
 872 config GUP_GET_PTE_LOW_HIGH
 873         bool
 874
 875 config READ_ONLY_THP_FOR_FS
 876         bool "Read-only THP for filesystems (EXPERIMENTAL)"
 877         depends on TRANSPARENT_HUGEPAGE && SHMEM
 878
 879         help
 880           Allow khugepaged to put read-only file-backed pages in THP.
 881
 882           This is marked experimental because it is a new feature. Write
 883           support of file THPs will be developed in the next few release
 884           cycles.
 885
 886 config ARCH_HAS_PTE_SPECIAL
 887         bool
 888
 889 #
 890 # Some architectures require a special hugepage directory format that is
 891 # required to support multiple hugepage sizes. For example a4fe3ce76
 892 # "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
 893 # introduced it on powerpc.  This allows for a more flexible hugepage
 894 # pagetable layouts.
 895 #
 896 config ARCH_HAS_HUGEPD
 897         bool
 898
 899 config MAPPING_DIRTY_HELPERS
 900         bool
 901
 902 config KMAP_LOCAL
 903         bool
 904
 905 config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY
 906         bool
 907
 908 # struct io_mapping based helper.  Selected by drivers that need them
 909 config IO_MAPPING
 910         bool
 911
 912 config SECRETMEM
 913         def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED
 914
 915 config ANON_VMA_NAME
 916         bool "Anonymous VMA name support"
 917         depends on PROC_FS && ADVISE_SYSCALLS && MMU
 918
 919         help
 920           Allow naming anonymous virtual memory areas.
 921
 922           This feature allows assigning names to virtual memory areas. Assigned
 923           names can be later retrieved from /proc/pid/maps and /proc/pid/smaps
 924           and help identifying individual anonymous memory areas.
 925           Assigning a name to anonymous virtual memory area might prevent that
 926           area from being merged with adjacent virtual memory areas due to the
 927           difference in their name.
 928
 929 source "mm/damon/Kconfig"
 930
 931 endmenu