mm/Kconfig

   1 config SELECT_MEMORY_MODEL
   2         def_bool y
   3         depends on ARCH_SELECT_MEMORY_MODEL
   4
   5 choice
   6         prompt "Memory model"
   7         depends on SELECT_MEMORY_MODEL
   8         default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
   9         default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
  10         default FLATMEM_MANUAL
  11
  12 config FLATMEM_MANUAL
  13         bool "Flat Memory"
  14         depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
  15         help
  16           This option allows you to change some of the ways that
  17           Linux manages its memory internally.  Most users will
  18           only have one option here: FLATMEM.  This is normal
  19           and a correct option.
  20
  21           Some users of more advanced features like NUMA and
  22           memory hotplug may have different options here.
  23           DISCONTIGMEM is an more mature, better tested system,
  24           but is incompatible with memory hotplug and may suffer
  25           decreased performance over SPARSEMEM.  If unsure between
  26           "Sparse Memory" and "Discontiguous Memory", choose
  27           "Discontiguous Memory".
  28
  29           If unsure, choose this option (Flat Memory) over any other.
  30
  31 config DISCONTIGMEM_MANUAL
  32         bool "Discontiguous Memory"
  33         depends on ARCH_DISCONTIGMEM_ENABLE
  34         help
  35           This option provides enhanced support for discontiguous
  36           memory systems, over FLATMEM.  These systems have holes
  37           in their physical address spaces, and this option provides
  38           more efficient handling of these holes.  However, the vast
  39           majority of hardware has quite flat address spaces, and
  40           can have degraded performance from the extra overhead that
  41           this option imposes.
  42
  43           Many NUMA configurations will have this as the only option.
  44
  45           If unsure, choose "Flat Memory" over this option.
  46
  47 config SPARSEMEM_MANUAL
  48         bool "Sparse Memory"
  49         depends on ARCH_SPARSEMEM_ENABLE
  50         help
  51           This will be the only option for some systems, including
  52           memory hotplug systems.  This is normal.
  53
  54           For many other systems, this will be an alternative to
  55           "Discontiguous Memory".  This option provides some potential
  56           performance benefits, along with decreased code complexity,
  57           but it is newer, and more experimental.
  58
  59           If unsure, choose "Discontiguous Memory" or "Flat Memory"
  60           over this option.
  61
  62 endchoice
  63
  64 config DISCONTIGMEM
  65         def_bool y
  66         depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
  67
  68 config SPARSEMEM
  69         def_bool y
  70         depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
  71
  72 config FLATMEM
  73         def_bool y
  74         depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
  75
  76 config FLAT_NODE_MEM_MAP
  77         def_bool y
  78         depends on !SPARSEMEM
  79
  80 #
  81 # Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
  82 # to represent different areas of memory.  This variable allows
  83 # those dependencies to exist individually.
  84 #
  85 config NEED_MULTIPLE_NODES
  86         def_bool y
  87         depends on DISCONTIGMEM || NUMA
  88
  89 config HAVE_MEMORY_PRESENT
  90         def_bool y
  91         depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
  92
  93 #
  94 # SPARSEMEM_EXTREME (which is the default) does some bootmem
  95 # allocations when memory_present() is called.  If this cannot
  96 # be done on your architecture, select this option.  However,
  97 # statically allocating the mem_section[] array can potentially
  98 # consume vast quantities of .bss, so be careful.
  99 #
 100 # This option will also potentially produce smaller runtime code
 101 # with gcc 3.4 and later.
 102 #
 103 config SPARSEMEM_STATIC
 104         bool
 105
 106 #
 107 # Architecture platforms which require a two level mem_section in SPARSEMEM
 108 # must select this option. This is usually for architecture platforms with
 109 # an extremely sparse physical address space.
 110 #
 111 config SPARSEMEM_EXTREME
 112         def_bool y
 113         depends on SPARSEMEM && !SPARSEMEM_STATIC
 114
 115 config SPARSEMEM_VMEMMAP_ENABLE
 116         bool
 117
 118 config SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
 119         def_bool y
 120         depends on SPARSEMEM && X86_64
 121
 122 config SPARSEMEM_VMEMMAP
 123         bool "Sparse Memory virtual memmap"
 124         depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
 125         default y
 126         help
 127          SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
 128          pfn_to_page and page_to_pfn operations.  This is the most
 129          efficient option when sufficient kernel resources are available.
 130
 131 config HAVE_MEMBLOCK
 132         boolean
 133
 134 config HAVE_MEMBLOCK_NODE_MAP
 135         boolean
 136
 137 config ARCH_DISCARD_MEMBLOCK
 138         boolean
 139
 140 config NO_BOOTMEM
 141         boolean
 142
 143 config MEMORY_ISOLATION
 144         boolean
 145
 146 config MOVABLE_NODE
 147         boolean "Enable to assign a node which has only movable memory"
 148         depends on HAVE_MEMBLOCK
 149         depends on NO_BOOTMEM
 150         depends on X86_64
 151         depends on NUMA
 152         default n
 153         help
 154           Allow a node to have only movable memory.  Pages used by the kernel,
 155           such as direct mapping pages cannot be migrated.  So the corresponding
 156           memory device cannot be hotplugged.  This option allows the following
 157           two things:
 158           - When the system is booting, node full of hotpluggable memory can
 159           be arranged to have only movable memory so that the whole node can
 160           be hot-removed. (need movable_node boot option specified).
 161           - After the system is up, the option allows users to online all the
 162           memory of a node as movable memory so that the whole node can be
 163           hot-removed.
 164
 165           Users who don't use the memory hotplug feature are fine with this
 166           option on since they don't specify movable_node boot option or they
 167           don't online memory as movable.
 168
 169           Say Y here if you want to hotplug a whole node.
 170           Say N here if you want kernel to use memory on all nodes evenly.
 171
 172 #
 173 # Only be set on architectures that have completely implemented memory hotplug
 174 # feature. If you are not sure, don't touch it.
 175 #
 176 config HAVE_BOOTMEM_INFO_NODE
 177         def_bool n
 178
 179 # eventually, we can have this option just 'select SPARSEMEM'
 180 config MEMORY_HOTPLUG
 181         bool "Allow for memory hot-add"
 182         depends on SPARSEMEM || X86_64_ACPI_NUMA
 183         depends on ARCH_ENABLE_MEMORY_HOTPLUG
 184         depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
 185
 186 config MEMORY_HOTPLUG_SPARSE
 187         def_bool y
 188         depends on SPARSEMEM && MEMORY_HOTPLUG
 189
 190 config MEMORY_HOTREMOVE
 191         bool "Allow for memory hot remove"
 192         select MEMORY_ISOLATION
 193         select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
 194         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 195         depends on MIGRATION
 196
 197 #
 198 # If we have space for more page flags then we can enable additional
 199 # optimizations and functionality.
 200 #
 201 # Regular Sparsemem takes page flag bits for the sectionid if it does not
 202 # use a virtual memmap. Disable extended page flags for 32 bit platforms
 203 # that require the use of a sectionid in the page flags.
 204 #
 205 config PAGEFLAGS_EXTENDED
 206         def_bool y
 207         depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
 208
 209 # Heavily threaded applications may benefit from splitting the mm-wide
 210 # page_table_lock, so that faults on different parts of the user address
 211 # space can be handled with less contention: split it at this NR_CPUS.
 212 # Default to 4 for wider testing, though 8 might be more appropriate.
 213 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 214 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 215 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
 216 #
 217 config SPLIT_PTLOCK_CPUS
 218         int
 219         default "999999" if ARM && !CPU_CACHE_VIPT
 220         default "999999" if PARISC && !PA20
 221         default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
 222         default "4"
 223
 224 #
 225 # support for memory balloon compaction
 226 config BALLOON_COMPACTION
 227         bool "Allow for balloon memory compaction/migration"
 228         def_bool y
 229         depends on COMPACTION && VIRTIO_BALLOON
 230         help
 231           Memory fragmentation introduced by ballooning might reduce
 232           significantly the number of 2MB contiguous memory blocks that can be
 233           used within a guest, thus imposing performance penalties associated
 234           with the reduced number of transparent huge pages that could be used
 235           by the guest workload. Allowing the compaction & migration for memory
 236           pages enlisted as being part of memory balloon devices avoids the
 237           scenario aforementioned and helps improving memory defragmentation.
 238
 239 #
 240 # support for memory compaction
 241 config COMPACTION
 242         bool "Allow for memory compaction"
 243         def_bool y
 244         select MIGRATION
 245         depends on MMU
 246         help
 247           Allows the compaction of memory for the allocation of huge pages.
 248
 249 #
 250 # support for page migration
 251 #
 252 config MIGRATION
 253         bool "Page migration"
 254         def_bool y
 255         depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
 256         help
 257           Allows the migration of the physical location of pages of processes
 258           while the virtual addresses are not changed. This is useful in
 259           two situations. The first is on NUMA systems to put pages nearer
 260           to the processors accessing. The second is when allocating huge
 261           pages as migration can relocate pages to satisfy a huge page
 262           allocation instead of reclaiming.
 263
 264 config PHYS_ADDR_T_64BIT
 265         def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
 266
 267 config ZONE_DMA_FLAG
 268         int
 269         default "0" if !ZONE_DMA
 270         default "1"
 271
 272 config BOUNCE
 273         bool "Enable bounce buffers"
 274         default y
 275         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 276         help
 277           Enable bounce buffers for devices that cannot access
 278           the full range of memory available to the CPU. Enabled
 279           by default when ZONE_DMA or HIGHMEM is selected, but you
 280           may say n to override this.
 281
 282 # On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
 283 # have more than 4GB of memory, but we don't currently use the IOTLB to present
 284 # a 32-bit address to OHCI.  So we need to use a bounce pool instead.
 285 #
 286 # We also use the bounce pool to provide stable page writes for jbd.  jbd
 287 # initiates buffer writeback without locking the page or setting PG_writeback,
 288 # and fixing that behavior (a second time; jbd2 doesn't have this problem) is
 289 # a major rework effort.  Instead, use the bounce buffer to snapshot pages
 290 # (until jbd goes away).  The only jbd user is ext3.
 291 config NEED_BOUNCE_POOL
 292         bool
 293         default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD)
 294
 295 config NR_QUICK
 296         int
 297         depends on QUICKLIST
 298         default "2" if AVR32
 299         default "1"
 300
 301 config VIRT_TO_BUS
 302         bool
 303         help
 304           An architecture should select this if it implements the
 305           deprecated interface virt_to_bus().  All new architectures
 306           should probably not select this.
 307
 308
 309 config MMU_NOTIFIER
 310         bool
 311
 312 config KSM
 313         bool "Enable KSM for page merging"
 314         depends on MMU
 315         help
 316           Enable Kernel Samepage Merging: KSM periodically scans those areas
 317           of an application's address space that an app has advised may be
 318           mergeable.  When it finds pages of identical content, it replaces
 319           the many instances by a single page with that content, so
 320           saving memory until one or another app needs to modify the content.
 321           Recommended for use with KVM, or with other duplicative applications.
 322           See Documentation/vm/ksm.txt for more information: KSM is inactive
 323           until a program has madvised that an area is MADV_MERGEABLE, and
 324           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 325
 326 config DEFAULT_MMAP_MIN_ADDR
 327         int "Low address space to protect from user allocation"
 328         depends on MMU
 329         default 4096
 330         help
 331           This is the portion of low virtual memory which should be protected
 332           from userspace allocation.  Keeping a user from writing to low pages
 333           can help reduce the impact of kernel NULL pointer bugs.
 334
 335           For most ia64, ppc64 and x86 users with lots of address space
 336           a value of 65536 is reasonable and should cause no problems.
 337           On arm and other archs it should not be higher than 32768.
 338           Programs which use vm86 functionality or have some need to map
 339           this low address space will need CAP_SYS_RAWIO or disable this
 340           protection by setting the value to 0.
 341
 342           This value can be changed after boot using the
 343           /proc/sys/vm/mmap_min_addr tunable.
 344
 345 config ARCH_SUPPORTS_MEMORY_FAILURE
 346         bool
 347
 348 config MEMORY_FAILURE
 349         depends on MMU
 350         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 351         bool "Enable recovery from hardware memory errors"
 352         select MEMORY_ISOLATION
 353         help
 354           Enables code to recover from some memory failures on systems
 355           with MCA recovery. This allows a system to continue running
 356           even when some of its memory has uncorrected errors. This requires
 357           special hardware support and typically ECC memory.
 358
 359 config HWPOISON_INJECT
 360         tristate "HWPoison pages injector"
 361         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 362         select PROC_PAGE_MONITOR
 363
 364 config NOMMU_INITIAL_TRIM_EXCESS
 365         int "Turn on mmap() excess space trimming before booting"
 366         depends on !MMU
 367         default 1
 368         help
 369           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 370           of memory on which to store mappings, but it can only ask the system
 371           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 372           more than it requires.  To deal with this, mmap() is able to trim off
 373           the excess and return it to the allocator.
 374
 375           If trimming is enabled, the excess is trimmed off and returned to the
 376           system allocator, which can cause extra fragmentation, particularly
 377           if there are a lot of transient processes.
 378
 379           If trimming is disabled, the excess is kept, but not used, which for
 380           long-term mappings means that the space is wasted.
 381
 382           Trimming can be dynamically controlled through a sysctl option
 383           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 384           excess pages there must be before trimming should occur, or zero if
 385           no trimming is to occur.
 386
 387           This option specifies the initial value of this option.  The default
 388           of 1 says that all excess pages should be trimmed.
 389
 390           See Documentation/nommu-mmap.txt for more information.
 391
 392 config TRANSPARENT_HUGEPAGE
 393         bool "Transparent Hugepage Support"
 394         depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
 395         select COMPACTION
 396         help
 397           Transparent Hugepages allows the kernel to use huge pages and
 398           huge tlb transparently to the applications whenever possible.
 399           This feature can improve computing performance to certain
 400           applications by speeding up page faults during memory
 401           allocation, by reducing the number of tlb misses and by speeding
 402           up the pagetable walking.
 403
 404           If memory constrained on embedded, you may want to say N.
 405
 406 choice
 407         prompt "Transparent Hugepage Support sysfs defaults"
 408         depends on TRANSPARENT_HUGEPAGE
 409         default TRANSPARENT_HUGEPAGE_ALWAYS
 410         help
 411           Selects the sysfs defaults for Transparent Hugepage Support.
 412
 413         config TRANSPARENT_HUGEPAGE_ALWAYS
 414                 bool "always"
 415         help
 416           Enabling Transparent Hugepage always, can increase the
 417           memory footprint of applications without a guaranteed
 418           benefit but it will work automatically for all applications.
 419
 420         config TRANSPARENT_HUGEPAGE_MADVISE
 421                 bool "madvise"
 422         help
 423           Enabling Transparent Hugepage madvise, will only provide a
 424           performance improvement benefit to the applications using
 425           madvise(MADV_HUGEPAGE) but it won't risk to increase the
 426           memory footprint of applications without a guaranteed
 427           benefit.
 428 endchoice
 429
 430 config CROSS_MEMORY_ATTACH
 431         bool "Cross Memory Support"
 432         depends on MMU
 433         default y
 434         help
 435           Enabling this option adds the system calls process_vm_readv and
 436           process_vm_writev which allow a process with the correct privileges
 437           to directly read from or write to to another process's address space.
 438           See the man page for more details.
 439
 440 #
 441 # UP and nommu archs use km based percpu allocator
 442 #
 443 config NEED_PER_CPU_KM
 444         depends on !SMP
 445         bool
 446         default y
 447
 448 config CLEANCACHE
 449         bool "Enable cleancache driver to cache clean pages if tmem is present"
 450         default n
 451         help
 452           Cleancache can be thought of as a page-granularity victim cache
 453           for clean pages that the kernel's pageframe replacement algorithm
 454           (PFRA) would like to keep around, but can't since there isn't enough
 455           memory.  So when the PFRA "evicts" a page, it first attempts to use
 456           cleancache code to put the data contained in that page into
 457           "transcendent memory", memory that is not directly accessible or
 458           addressable by the kernel and is of unknown and possibly
 459           time-varying size.  And when a cleancache-enabled
 460           filesystem wishes to access a page in a file on disk, it first
 461           checks cleancache to see if it already contains it; if it does,
 462           the page is copied into the kernel and a disk access is avoided.
 463           When a transcendent memory driver is available (such as zcache or
 464           Xen transcendent memory), a significant I/O reduction
 465           may be achieved.  When none is available, all cleancache calls
 466           are reduced to a single pointer-compare-against-NULL resulting
 467           in a negligible performance hit.
 468
 469           If unsure, say Y to enable cleancache
 470
 471 config FRONTSWAP
 472         bool "Enable frontswap to cache swap pages if tmem is present"
 473         depends on SWAP
 474         default n
 475         help
 476           Frontswap is so named because it can be thought of as the opposite
 477           of a "backing" store for a swap device.  The data is stored into
 478           "transcendent memory", memory that is not directly accessible or
 479           addressable by the kernel and is of unknown and possibly
 480           time-varying size.  When space in transcendent memory is available,
 481           a significant swap I/O reduction may be achieved.  When none is
 482           available, all frontswap calls are reduced to a single pointer-
 483           compare-against-NULL resulting in a negligible performance hit
 484           and swap data is stored as normal on the matching swap device.
 485
 486           If unsure, say Y to enable frontswap.
 487
 488 config CMA
 489         bool "Contiguous Memory Allocator"
 490         depends on HAVE_MEMBLOCK && MMU
 491         select MIGRATION
 492         select MEMORY_ISOLATION
 493         help
 494           This enables the Contiguous Memory Allocator which allows other
 495           subsystems to allocate big physically-contiguous blocks of memory.
 496           CMA reserves a region of memory and allows only movable pages to
 497           be allocated from it. This way, the kernel can use the memory for
 498           pagecache and when a subsystem requests for contiguous area, the
 499           allocated pages are migrated away to serve the contiguous request.
 500
 501           If unsure, say "n".
 502
 503 config CMA_DEBUG
 504         bool "CMA debug messages (DEVELOPMENT)"
 505         depends on DEBUG_KERNEL && CMA
 506         help
 507           Turns on debug messages in CMA.  This produces KERN_DEBUG
 508           messages for every CMA call as well as various messages while
 509           processing calls such as dma_alloc_from_contiguous().
 510           This option does not affect warning and error messages.
 511
 512 config ZBUD
 513         tristate
 514         default n
 515         help
 516           A special purpose allocator for storing compressed pages.
 517           It is designed to store up to two compressed pages per physical
 518           page.  While this design limits storage density, it has simple and
 519           deterministic reclaim properties that make it preferable to a higher
 520           density approach when reclaim will be used.
 521
 522 config ZSWAP
 523         bool "Compressed cache for swap pages (EXPERIMENTAL)"
 524         depends on FRONTSWAP && CRYPTO=y
 525         select CRYPTO_LZO
 526         select ZBUD
 527         default n
 528         help
 529           A lightweight compressed cache for swap pages.  It takes
 530           pages that are in the process of being swapped out and attempts to
 531           compress them into a dynamically allocated RAM-based memory pool.
 532           This can result in a significant I/O reduction on swap device and,
 533           in the case where decompressing from RAM is faster that swap device
 534           reads, can also improve workload performance.
 535
 536           This is marked experimental because it is a new feature (as of
 537           v3.11) that interacts heavily with memory reclaim.  While these
 538           interactions don't cause any known issues on simple memory setups,
 539           they have not be fully explored on the large set of potential
 540           configurations and workloads that exist.
 541
 542 config MEM_SOFT_DIRTY
 543         bool "Track memory changes"
 544         depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY
 545         select PROC_PAGE_MONITOR
 546         help
 547           This option enables memory changes tracking by introducing a
 548           soft-dirty bit on pte-s. This bit it set when someone writes
 549           into a page just as regular dirty bit, but unlike the latter
 550           it can be cleared by hands.
 551
 552           See Documentation/vm/soft-dirty.txt for more details.