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 users to
 157           online all the memory of a node as movable memory so that the whole
 158           node can be hotplugged.  Users who don't use the memory hotplug
 159           feature are fine with this option on since they don't online memory
 160           as movable.
 161
 162           Say Y here if you want to hotplug a whole node.
 163           Say N here if you want kernel to use memory on all nodes evenly.
 164
 165 #
 166 # Only be set on architectures that have completely implemented memory hotplug
 167 # feature. If you are not sure, don't touch it.
 168 #
 169 config HAVE_BOOTMEM_INFO_NODE
 170         def_bool n
 171
 172 # eventually, we can have this option just 'select SPARSEMEM'
 173 config MEMORY_HOTPLUG
 174         bool "Allow for memory hot-add"
 175         depends on SPARSEMEM || X86_64_ACPI_NUMA
 176         depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG
 177         depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
 178
 179 config MEMORY_HOTPLUG_SPARSE
 180         def_bool y
 181         depends on SPARSEMEM && MEMORY_HOTPLUG
 182
 183 config MEMORY_HOTREMOVE
 184         bool "Allow for memory hot remove"
 185         select MEMORY_ISOLATION
 186         select HAVE_BOOTMEM_INFO_NODE if X86_64
 187         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 188         depends on MIGRATION
 189
 190 #
 191 # If we have space for more page flags then we can enable additional
 192 # optimizations and functionality.
 193 #
 194 # Regular Sparsemem takes page flag bits for the sectionid if it does not
 195 # use a virtual memmap. Disable extended page flags for 32 bit platforms
 196 # that require the use of a sectionid in the page flags.
 197 #
 198 config PAGEFLAGS_EXTENDED
 199         def_bool y
 200         depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
 201
 202 # Heavily threaded applications may benefit from splitting the mm-wide
 203 # page_table_lock, so that faults on different parts of the user address
 204 # space can be handled with less contention: split it at this NR_CPUS.
 205 # Default to 4 for wider testing, though 8 might be more appropriate.
 206 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 207 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 208 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
 209 #
 210 config SPLIT_PTLOCK_CPUS
 211         int
 212         default "999999" if ARM && !CPU_CACHE_VIPT
 213         default "999999" if PARISC && !PA20
 214         default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
 215         default "4"
 216
 217 #
 218 # support for memory balloon compaction
 219 config BALLOON_COMPACTION
 220         bool "Allow for balloon memory compaction/migration"
 221         def_bool y
 222         depends on COMPACTION && VIRTIO_BALLOON
 223         help
 224           Memory fragmentation introduced by ballooning might reduce
 225           significantly the number of 2MB contiguous memory blocks that can be
 226           used within a guest, thus imposing performance penalties associated
 227           with the reduced number of transparent huge pages that could be used
 228           by the guest workload. Allowing the compaction & migration for memory
 229           pages enlisted as being part of memory balloon devices avoids the
 230           scenario aforementioned and helps improving memory defragmentation.
 231
 232 #
 233 # support for memory compaction
 234 config COMPACTION
 235         bool "Allow for memory compaction"
 236         def_bool y
 237         select MIGRATION
 238         depends on MMU
 239         help
 240           Allows the compaction of memory for the allocation of huge pages.
 241
 242 #
 243 # support for page migration
 244 #
 245 config MIGRATION
 246         bool "Page migration"
 247         def_bool y
 248         depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA
 249         help
 250           Allows the migration of the physical location of pages of processes
 251           while the virtual addresses are not changed. This is useful in
 252           two situations. The first is on NUMA systems to put pages nearer
 253           to the processors accessing. The second is when allocating huge
 254           pages as migration can relocate pages to satisfy a huge page
 255           allocation instead of reclaiming.
 256
 257 config PHYS_ADDR_T_64BIT
 258         def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
 259
 260 config ZONE_DMA_FLAG
 261         int
 262         default "0" if !ZONE_DMA
 263         default "1"
 264
 265 config BOUNCE
 266         bool "Enable bounce buffers"
 267         default y
 268         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 269         help
 270           Enable bounce buffers for devices that cannot access
 271           the full range of memory available to the CPU. Enabled
 272           by default when ZONE_DMA or HIGHMEM is selected, but you
 273           may say n to override this.
 274
 275 # On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
 276 # have more than 4GB of memory, but we don't currently use the IOTLB to present
 277 # a 32-bit address to OHCI.  So we need to use a bounce pool instead.
 278 #
 279 # We also use the bounce pool to provide stable page writes for jbd.  jbd
 280 # initiates buffer writeback without locking the page or setting PG_writeback,
 281 # and fixing that behavior (a second time; jbd2 doesn't have this problem) is
 282 # a major rework effort.  Instead, use the bounce buffer to snapshot pages
 283 # (until jbd goes away).  The only jbd user is ext3.
 284 config NEED_BOUNCE_POOL
 285         bool
 286         default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD)
 287
 288 config NR_QUICK
 289         int
 290         depends on QUICKLIST
 291         default "2" if AVR32
 292         default "1"
 293
 294 config VIRT_TO_BUS
 295         bool
 296         help
 297           An architecture should select this if it implements the
 298           deprecated interface virt_to_bus().  All new architectures
 299           should probably not select this.
 300
 301
 302 config MMU_NOTIFIER
 303         bool
 304
 305 config KSM
 306         bool "Enable KSM for page merging"
 307         depends on MMU
 308         help
 309           Enable Kernel Samepage Merging: KSM periodically scans those areas
 310           of an application's address space that an app has advised may be
 311           mergeable.  When it finds pages of identical content, it replaces
 312           the many instances by a single page with that content, so
 313           saving memory until one or another app needs to modify the content.
 314           Recommended for use with KVM, or with other duplicative applications.
 315           See Documentation/vm/ksm.txt for more information: KSM is inactive
 316           until a program has madvised that an area is MADV_MERGEABLE, and
 317           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 318
 319 config DEFAULT_MMAP_MIN_ADDR
 320         int "Low address space to protect from user allocation"
 321         depends on MMU
 322         default 4096
 323         help
 324           This is the portion of low virtual memory which should be protected
 325           from userspace allocation.  Keeping a user from writing to low pages
 326           can help reduce the impact of kernel NULL pointer bugs.
 327
 328           For most ia64, ppc64 and x86 users with lots of address space
 329           a value of 65536 is reasonable and should cause no problems.
 330           On arm and other archs it should not be higher than 32768.
 331           Programs which use vm86 functionality or have some need to map
 332           this low address space will need CAP_SYS_RAWIO or disable this
 333           protection by setting the value to 0.
 334
 335           This value can be changed after boot using the
 336           /proc/sys/vm/mmap_min_addr tunable.
 337
 338 config ARCH_SUPPORTS_MEMORY_FAILURE
 339         bool
 340
 341 config MEMORY_FAILURE
 342         depends on MMU
 343         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 344         bool "Enable recovery from hardware memory errors"
 345         select MEMORY_ISOLATION
 346         help
 347           Enables code to recover from some memory failures on systems
 348           with MCA recovery. This allows a system to continue running
 349           even when some of its memory has uncorrected errors. This requires
 350           special hardware support and typically ECC memory.
 351
 352 config HWPOISON_INJECT
 353         tristate "HWPoison pages injector"
 354         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 355         select PROC_PAGE_MONITOR
 356
 357 config NOMMU_INITIAL_TRIM_EXCESS
 358         int "Turn on mmap() excess space trimming before booting"
 359         depends on !MMU
 360         default 1
 361         help
 362           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 363           of memory on which to store mappings, but it can only ask the system
 364           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 365           more than it requires.  To deal with this, mmap() is able to trim off
 366           the excess and return it to the allocator.
 367
 368           If trimming is enabled, the excess is trimmed off and returned to the
 369           system allocator, which can cause extra fragmentation, particularly
 370           if there are a lot of transient processes.
 371
 372           If trimming is disabled, the excess is kept, but not used, which for
 373           long-term mappings means that the space is wasted.
 374
 375           Trimming can be dynamically controlled through a sysctl option
 376           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 377           excess pages there must be before trimming should occur, or zero if
 378           no trimming is to occur.
 379
 380           This option specifies the initial value of this option.  The default
 381           of 1 says that all excess pages should be trimmed.
 382
 383           See Documentation/nommu-mmap.txt for more information.
 384
 385 config TRANSPARENT_HUGEPAGE
 386         bool "Transparent Hugepage Support"
 387         depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
 388         select COMPACTION
 389         help
 390           Transparent Hugepages allows the kernel to use huge pages and
 391           huge tlb transparently to the applications whenever possible.
 392           This feature can improve computing performance to certain
 393           applications by speeding up page faults during memory
 394           allocation, by reducing the number of tlb misses and by speeding
 395           up the pagetable walking.
 396
 397           If memory constrained on embedded, you may want to say N.
 398
 399 choice
 400         prompt "Transparent Hugepage Support sysfs defaults"
 401         depends on TRANSPARENT_HUGEPAGE
 402         default TRANSPARENT_HUGEPAGE_ALWAYS
 403         help
 404           Selects the sysfs defaults for Transparent Hugepage Support.
 405
 406         config TRANSPARENT_HUGEPAGE_ALWAYS
 407                 bool "always"
 408         help
 409           Enabling Transparent Hugepage always, can increase the
 410           memory footprint of applications without a guaranteed
 411           benefit but it will work automatically for all applications.
 412
 413         config TRANSPARENT_HUGEPAGE_MADVISE
 414                 bool "madvise"
 415         help
 416           Enabling Transparent Hugepage madvise, will only provide a
 417           performance improvement benefit to the applications using
 418           madvise(MADV_HUGEPAGE) but it won't risk to increase the
 419           memory footprint of applications without a guaranteed
 420           benefit.
 421 endchoice
 422
 423 config CROSS_MEMORY_ATTACH
 424         bool "Cross Memory Support"
 425         depends on MMU
 426         default y
 427         help
 428           Enabling this option adds the system calls process_vm_readv and
 429           process_vm_writev which allow a process with the correct privileges
 430           to directly read from or write to to another process's address space.
 431           See the man page for more details.
 432
 433 #
 434 # UP and nommu archs use km based percpu allocator
 435 #
 436 config NEED_PER_CPU_KM
 437         depends on !SMP
 438         bool
 439         default y
 440
 441 config CLEANCACHE
 442         bool "Enable cleancache driver to cache clean pages if tmem is present"
 443         default n
 444         help
 445           Cleancache can be thought of as a page-granularity victim cache
 446           for clean pages that the kernel's pageframe replacement algorithm
 447           (PFRA) would like to keep around, but can't since there isn't enough
 448           memory.  So when the PFRA "evicts" a page, it first attempts to use
 449           cleancache code to put the data contained in that page into
 450           "transcendent memory", memory that is not directly accessible or
 451           addressable by the kernel and is of unknown and possibly
 452           time-varying size.  And when a cleancache-enabled
 453           filesystem wishes to access a page in a file on disk, it first
 454           checks cleancache to see if it already contains it; if it does,
 455           the page is copied into the kernel and a disk access is avoided.
 456           When a transcendent memory driver is available (such as zcache or
 457           Xen transcendent memory), a significant I/O reduction
 458           may be achieved.  When none is available, all cleancache calls
 459           are reduced to a single pointer-compare-against-NULL resulting
 460           in a negligible performance hit.
 461
 462           If unsure, say Y to enable cleancache
 463
 464 config FRONTSWAP
 465         bool "Enable frontswap to cache swap pages if tmem is present"
 466         depends on SWAP
 467         default n
 468         help
 469           Frontswap is so named because it can be thought of as the opposite
 470           of a "backing" store for a swap device.  The data is stored into
 471           "transcendent memory", memory that is not directly accessible or
 472           addressable by the kernel and is of unknown and possibly
 473           time-varying size.  When space in transcendent memory is available,
 474           a significant swap I/O reduction may be achieved.  When none is
 475           available, all frontswap calls are reduced to a single pointer-
 476           compare-against-NULL resulting in a negligible performance hit
 477           and swap data is stored as normal on the matching swap device.
 478
 479           If unsure, say Y to enable frontswap.