mm/Kconfig

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