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 a 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 "4"
 222
 223 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
 224         boolean
 225
 226 #
 227 # support for memory balloon compaction
 228 config BALLOON_COMPACTION
 229         bool "Allow for balloon memory compaction/migration"
 230         def_bool y
 231         depends on COMPACTION && VIRTIO_BALLOON
 232         help
 233           Memory fragmentation introduced by ballooning might reduce
 234           significantly the number of 2MB contiguous memory blocks that can be
 235           used within a guest, thus imposing performance penalties associated
 236           with the reduced number of transparent huge pages that could be used
 237           by the guest workload. Allowing the compaction & migration for memory
 238           pages enlisted as being part of memory balloon devices avoids the
 239           scenario aforementioned and helps improving memory defragmentation.
 240
 241 #
 242 # support for memory compaction
 243 config COMPACTION
 244         bool "Allow for memory compaction"
 245         def_bool y
 246         select MIGRATION
 247         depends on MMU
 248         help
 249           Allows the compaction of memory for the allocation of huge pages.
 250
 251 #
 252 # support for page migration
 253 #
 254 config MIGRATION
 255         bool "Page migration"
 256         def_bool y
 257         depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
 258         help
 259           Allows the migration of the physical location of pages of processes
 260           while the virtual addresses are not changed. This is useful in
 261           two situations. The first is on NUMA systems to put pages nearer
 262           to the processors accessing. The second is when allocating huge
 263           pages as migration can relocate pages to satisfy a huge page
 264           allocation instead of reclaiming.
 265
 266 config PHYS_ADDR_T_64BIT
 267         def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
 268
 269 config ZONE_DMA_FLAG
 270         int
 271         default "0" if !ZONE_DMA
 272         default "1"
 273
 274 config BOUNCE
 275         bool "Enable bounce buffers"
 276         default y
 277         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 278         help
 279           Enable bounce buffers for devices that cannot access
 280           the full range of memory available to the CPU. Enabled
 281           by default when ZONE_DMA or HIGHMEM is selected, but you
 282           may say n to override this.
 283
 284 # On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
 285 # have more than 4GB of memory, but we don't currently use the IOTLB to present
 286 # a 32-bit address to OHCI.  So we need to use a bounce pool instead.
 287 #
 288 # We also use the bounce pool to provide stable page writes for jbd.  jbd
 289 # initiates buffer writeback without locking the page or setting PG_writeback,
 290 # and fixing that behavior (a second time; jbd2 doesn't have this problem) is
 291 # a major rework effort.  Instead, use the bounce buffer to snapshot pages
 292 # (until jbd goes away).  The only jbd user is ext3.
 293 config NEED_BOUNCE_POOL
 294         bool
 295         default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD)
 296
 297 config NR_QUICK
 298         int
 299         depends on QUICKLIST
 300         default "2" if AVR32
 301         default "1"
 302
 303 config VIRT_TO_BUS
 304         bool
 305         help
 306           An architecture should select this if it implements the
 307           deprecated interface virt_to_bus().  All new architectures
 308           should probably not select this.
 309
 310
 311 config MMU_NOTIFIER
 312         bool
 313
 314 config KSM
 315         bool "Enable KSM for page merging"
 316         depends on MMU
 317         help
 318           Enable Kernel Samepage Merging: KSM periodically scans those areas
 319           of an application's address space that an app has advised may be
 320           mergeable.  When it finds pages of identical content, it replaces
 321           the many instances by a single page with that content, so
 322           saving memory until one or another app needs to modify the content.
 323           Recommended for use with KVM, or with other duplicative applications.
 324           See Documentation/vm/ksm.txt for more information: KSM is inactive
 325           until a program has madvised that an area is MADV_MERGEABLE, and
 326           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 327
 328 config DEFAULT_MMAP_MIN_ADDR
 329         int "Low address space to protect from user allocation"
 330         depends on MMU
 331         default 4096
 332         help
 333           This is the portion of low virtual memory which should be protected
 334           from userspace allocation.  Keeping a user from writing to low pages
 335           can help reduce the impact of kernel NULL pointer bugs.
 336
 337           For most ia64, ppc64 and x86 users with lots of address space
 338           a value of 65536 is reasonable and should cause no problems.
 339           On arm and other archs it should not be higher than 32768.
 340           Programs which use vm86 functionality or have some need to map
 341           this low address space will need CAP_SYS_RAWIO or disable this
 342           protection by setting the value to 0.
 343
 344           This value can be changed after boot using the
 345           /proc/sys/vm/mmap_min_addr tunable.
 346
 347 config ARCH_SUPPORTS_MEMORY_FAILURE
 348         bool
 349
 350 config MEMORY_FAILURE
 351         depends on MMU
 352         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 353         bool "Enable recovery from hardware memory errors"
 354         select MEMORY_ISOLATION
 355         help
 356           Enables code to recover from some memory failures on systems
 357           with MCA recovery. This allows a system to continue running
 358           even when some of its memory has uncorrected errors. This requires
 359           special hardware support and typically ECC memory.
 360
 361 config HWPOISON_INJECT
 362         tristate "HWPoison pages injector"
 363         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 364         select PROC_PAGE_MONITOR
 365
 366 config NOMMU_INITIAL_TRIM_EXCESS
 367         int "Turn on mmap() excess space trimming before booting"
 368         depends on !MMU
 369         default 1
 370         help
 371           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 372           of memory on which to store mappings, but it can only ask the system
 373           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 374           more than it requires.  To deal with this, mmap() is able to trim off
 375           the excess and return it to the allocator.
 376
 377           If trimming is enabled, the excess is trimmed off and returned to the
 378           system allocator, which can cause extra fragmentation, particularly
 379           if there are a lot of transient processes.
 380
 381           If trimming is disabled, the excess is kept, but not used, which for
 382           long-term mappings means that the space is wasted.
 383
 384           Trimming can be dynamically controlled through a sysctl option
 385           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 386           excess pages there must be before trimming should occur, or zero if
 387           no trimming is to occur.
 388
 389           This option specifies the initial value of this option.  The default
 390           of 1 says that all excess pages should be trimmed.
 391
 392           See Documentation/nommu-mmap.txt for more information.
 393
 394 config TRANSPARENT_HUGEPAGE
 395         bool "Transparent Hugepage Support"
 396         depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
 397         select COMPACTION
 398         help
 399           Transparent Hugepages allows the kernel to use huge pages and
 400           huge tlb transparently to the applications whenever possible.
 401           This feature can improve computing performance to certain
 402           applications by speeding up page faults during memory
 403           allocation, by reducing the number of tlb misses and by speeding
 404           up the pagetable walking.
 405
 406           If memory constrained on embedded, you may want to say N.
 407
 408 choice
 409         prompt "Transparent Hugepage Support sysfs defaults"
 410         depends on TRANSPARENT_HUGEPAGE
 411         default TRANSPARENT_HUGEPAGE_ALWAYS
 412         help
 413           Selects the sysfs defaults for Transparent Hugepage Support.
 414
 415         config TRANSPARENT_HUGEPAGE_ALWAYS
 416                 bool "always"
 417         help
 418           Enabling Transparent Hugepage always, can increase the
 419           memory footprint of applications without a guaranteed
 420           benefit but it will work automatically for all applications.
 421
 422         config TRANSPARENT_HUGEPAGE_MADVISE
 423                 bool "madvise"
 424         help
 425           Enabling Transparent Hugepage madvise, will only provide a
 426           performance improvement benefit to the applications using
 427           madvise(MADV_HUGEPAGE) but it won't risk to increase the
 428           memory footprint of applications without a guaranteed
 429           benefit.
 430 endchoice
 431
 432 config CROSS_MEMORY_ATTACH
 433         bool "Cross Memory Support"
 434         depends on MMU
 435         default y
 436         help
 437           Enabling this option adds the system calls process_vm_readv and
 438           process_vm_writev which allow a process with the correct privileges
 439           to directly read from or write to to another process's address space.
 440           See the man page for more details.
 441
 442 #
 443 # UP and nommu archs use km based percpu allocator
 444 #
 445 config NEED_PER_CPU_KM
 446         depends on !SMP
 447         bool
 448         default y
 449
 450 config CLEANCACHE
 451         bool "Enable cleancache driver to cache clean pages if tmem is present"
 452         default n
 453         help
 454           Cleancache can be thought of as a page-granularity victim cache
 455           for clean pages that the kernel's pageframe replacement algorithm
 456           (PFRA) would like to keep around, but can't since there isn't enough
 457           memory.  So when the PFRA "evicts" a page, it first attempts to use
 458           cleancache code to put the data contained in that page into
 459           "transcendent memory", memory that is not directly accessible or
 460           addressable by the kernel and is of unknown and possibly
 461           time-varying size.  And when a cleancache-enabled
 462           filesystem wishes to access a page in a file on disk, it first
 463           checks cleancache to see if it already contains it; if it does,
 464           the page is copied into the kernel and a disk access is avoided.
 465           When a transcendent memory driver is available (such as zcache or
 466           Xen transcendent memory), a significant I/O reduction
 467           may be achieved.  When none is available, all cleancache calls
 468           are reduced to a single pointer-compare-against-NULL resulting
 469           in a negligible performance hit.
 470
 471           If unsure, say Y to enable cleancache
 472
 473 config FRONTSWAP
 474         bool "Enable frontswap to cache swap pages if tmem is present"
 475         depends on SWAP
 476         default n
 477         help
 478           Frontswap is so named because it can be thought of as the opposite
 479           of a "backing" store for a swap device.  The data is stored into
 480           "transcendent memory", memory that is not directly accessible or
 481           addressable by the kernel and is of unknown and possibly
 482           time-varying size.  When space in transcendent memory is available,
 483           a significant swap I/O reduction may be achieved.  When none is
 484           available, all frontswap calls are reduced to a single pointer-
 485           compare-against-NULL resulting in a negligible performance hit
 486           and swap data is stored as normal on the matching swap device.
 487
 488           If unsure, say Y to enable frontswap.
 489
 490 config CMA
 491         bool "Contiguous Memory Allocator"
 492         depends on HAVE_MEMBLOCK && MMU
 493         select MIGRATION
 494         select MEMORY_ISOLATION
 495         help
 496           This enables the Contiguous Memory Allocator which allows other
 497           subsystems to allocate big physically-contiguous blocks of memory.
 498           CMA reserves a region of memory and allows only movable pages to
 499           be allocated from it. This way, the kernel can use the memory for
 500           pagecache and when a subsystem requests for contiguous area, the
 501           allocated pages are migrated away to serve the contiguous request.
 502
 503           If unsure, say "n".
 504
 505 config CMA_DEBUG
 506         bool "CMA debug messages (DEVELOPMENT)"
 507         depends on DEBUG_KERNEL && CMA
 508         help
 509           Turns on debug messages in CMA.  This produces KERN_DEBUG
 510           messages for every CMA call as well as various messages while
 511           processing calls such as dma_alloc_from_contiguous().
 512           This option does not affect warning and error messages.
 513
 514 config ZBUD
 515         tristate
 516         default n
 517         help
 518           A special purpose allocator for storing compressed pages.
 519           It is designed to store up to two compressed pages per physical
 520           page.  While this design limits storage density, it has simple and
 521           deterministic reclaim properties that make it preferable to a higher
 522           density approach when reclaim will be used.
 523
 524 config ZSWAP
 525         bool "Compressed cache for swap pages (EXPERIMENTAL)"
 526         depends on FRONTSWAP && CRYPTO=y
 527         select CRYPTO_LZO
 528         select ZBUD
 529         default n
 530         help
 531           A lightweight compressed cache for swap pages.  It takes
 532           pages that are in the process of being swapped out and attempts to
 533           compress them into a dynamically allocated RAM-based memory pool.
 534           This can result in a significant I/O reduction on swap device and,
 535           in the case where decompressing from RAM is faster that swap device
 536           reads, can also improve workload performance.
 537
 538           This is marked experimental because it is a new feature (as of
 539           v3.11) that interacts heavily with memory reclaim.  While these
 540           interactions don't cause any known issues on simple memory setups,
 541           they have not be fully explored on the large set of potential
 542           configurations and workloads that exist.
 543
 544 config MEM_SOFT_DIRTY
 545         bool "Track memory changes"
 546         depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
 547         select PROC_PAGE_MONITOR
 548         help
 549           This option enables memory changes tracking by introducing a
 550           soft-dirty bit on pte-s. This bit it set when someone writes
 551           into a page just as regular dirty bit, but unlike the latter
 552           it can be cleared by hands.
 553
 554           See Documentation/vm/soft-dirty.txt for more details.