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 # eventually, we can have this option just 'select SPARSEMEM'
 147 config MEMORY_HOTPLUG
 148         bool "Allow for memory hot-add"
 149         select MEMORY_ISOLATION
 150         depends on SPARSEMEM || X86_64_ACPI_NUMA
 151         depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG
 152         depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
 153
 154 config MEMORY_HOTPLUG_SPARSE
 155         def_bool y
 156         depends on SPARSEMEM && MEMORY_HOTPLUG
 157
 158 config MEMORY_HOTREMOVE
 159         bool "Allow for memory hot remove"
 160         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 161         depends on MIGRATION
 162
 163 #
 164 # If we have space for more page flags then we can enable additional
 165 # optimizations and functionality.
 166 #
 167 # Regular Sparsemem takes page flag bits for the sectionid if it does not
 168 # use a virtual memmap. Disable extended page flags for 32 bit platforms
 169 # that require the use of a sectionid in the page flags.
 170 #
 171 config PAGEFLAGS_EXTENDED
 172         def_bool y
 173         depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
 174
 175 # Heavily threaded applications may benefit from splitting the mm-wide
 176 # page_table_lock, so that faults on different parts of the user address
 177 # space can be handled with less contention: split it at this NR_CPUS.
 178 # Default to 4 for wider testing, though 8 might be more appropriate.
 179 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 180 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 181 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
 182 #
 183 config SPLIT_PTLOCK_CPUS
 184         int
 185         default "999999" if ARM && !CPU_CACHE_VIPT
 186         default "999999" if PARISC && !PA20
 187         default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
 188         default "4"
 189
 190 #
 191 # support for memory compaction
 192 config COMPACTION
 193         bool "Allow for memory compaction"
 194         select MIGRATION
 195         depends on MMU
 196         help
 197           Allows the compaction of memory for the allocation of huge pages.
 198
 199 #
 200 # support for page migration
 201 #
 202 config MIGRATION
 203         bool "Page migration"
 204         def_bool y
 205         depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA
 206         help
 207           Allows the migration of the physical location of pages of processes
 208           while the virtual addresses are not changed. This is useful in
 209           two situations. The first is on NUMA systems to put pages nearer
 210           to the processors accessing. The second is when allocating huge
 211           pages as migration can relocate pages to satisfy a huge page
 212           allocation instead of reclaiming.
 213
 214 config PHYS_ADDR_T_64BIT
 215         def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
 216
 217 config ZONE_DMA_FLAG
 218         int
 219         default "0" if !ZONE_DMA
 220         default "1"
 221
 222 config BOUNCE
 223         def_bool y
 224         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 225
 226 config NR_QUICK
 227         int
 228         depends on QUICKLIST
 229         default "2" if AVR32
 230         default "1"
 231
 232 config VIRT_TO_BUS
 233         def_bool y
 234         depends on !ARCH_NO_VIRT_TO_BUS
 235
 236 config MMU_NOTIFIER
 237         bool
 238
 239 config KSM
 240         bool "Enable KSM for page merging"
 241         depends on MMU
 242         help
 243           Enable Kernel Samepage Merging: KSM periodically scans those areas
 244           of an application's address space that an app has advised may be
 245           mergeable.  When it finds pages of identical content, it replaces
 246           the many instances by a single page with that content, so
 247           saving memory until one or another app needs to modify the content.
 248           Recommended for use with KVM, or with other duplicative applications.
 249           See Documentation/vm/ksm.txt for more information: KSM is inactive
 250           until a program has madvised that an area is MADV_MERGEABLE, and
 251           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 252
 253 config DEFAULT_MMAP_MIN_ADDR
 254         int "Low address space to protect from user allocation"
 255         depends on MMU
 256         default 4096
 257         help
 258           This is the portion of low virtual memory which should be protected
 259           from userspace allocation.  Keeping a user from writing to low pages
 260           can help reduce the impact of kernel NULL pointer bugs.
 261
 262           For most ia64, ppc64 and x86 users with lots of address space
 263           a value of 65536 is reasonable and should cause no problems.
 264           On arm and other archs it should not be higher than 32768.
 265           Programs which use vm86 functionality or have some need to map
 266           this low address space will need CAP_SYS_RAWIO or disable this
 267           protection by setting the value to 0.
 268
 269           This value can be changed after boot using the
 270           /proc/sys/vm/mmap_min_addr tunable.
 271
 272 config ARCH_SUPPORTS_MEMORY_FAILURE
 273         bool
 274
 275 config MEMORY_FAILURE
 276         depends on MMU
 277         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 278         bool "Enable recovery from hardware memory errors"
 279         select MEMORY_ISOLATION
 280         help
 281           Enables code to recover from some memory failures on systems
 282           with MCA recovery. This allows a system to continue running
 283           even when some of its memory has uncorrected errors. This requires
 284           special hardware support and typically ECC memory.
 285
 286 config HWPOISON_INJECT
 287         tristate "HWPoison pages injector"
 288         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 289         select PROC_PAGE_MONITOR
 290
 291 config NOMMU_INITIAL_TRIM_EXCESS
 292         int "Turn on mmap() excess space trimming before booting"
 293         depends on !MMU
 294         default 1
 295         help
 296           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 297           of memory on which to store mappings, but it can only ask the system
 298           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 299           more than it requires.  To deal with this, mmap() is able to trim off
 300           the excess and return it to the allocator.
 301
 302           If trimming is enabled, the excess is trimmed off and returned to the
 303           system allocator, which can cause extra fragmentation, particularly
 304           if there are a lot of transient processes.
 305
 306           If trimming is disabled, the excess is kept, but not used, which for
 307           long-term mappings means that the space is wasted.
 308
 309           Trimming can be dynamically controlled through a sysctl option
 310           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 311           excess pages there must be before trimming should occur, or zero if
 312           no trimming is to occur.
 313
 314           This option specifies the initial value of this option.  The default
 315           of 1 says that all excess pages should be trimmed.
 316
 317           See Documentation/nommu-mmap.txt for more information.
 318
 319 config TRANSPARENT_HUGEPAGE
 320         bool "Transparent Hugepage Support"
 321         depends on X86 && MMU
 322         select COMPACTION
 323         help
 324           Transparent Hugepages allows the kernel to use huge pages and
 325           huge tlb transparently to the applications whenever possible.
 326           This feature can improve computing performance to certain
 327           applications by speeding up page faults during memory
 328           allocation, by reducing the number of tlb misses and by speeding
 329           up the pagetable walking.
 330
 331           If memory constrained on embedded, you may want to say N.
 332
 333 choice
 334         prompt "Transparent Hugepage Support sysfs defaults"
 335         depends on TRANSPARENT_HUGEPAGE
 336         default TRANSPARENT_HUGEPAGE_ALWAYS
 337         help
 338           Selects the sysfs defaults for Transparent Hugepage Support.
 339
 340         config TRANSPARENT_HUGEPAGE_ALWAYS
 341                 bool "always"
 342         help
 343           Enabling Transparent Hugepage always, can increase the
 344           memory footprint of applications without a guaranteed
 345           benefit but it will work automatically for all applications.
 346
 347         config TRANSPARENT_HUGEPAGE_MADVISE
 348                 bool "madvise"
 349         help
 350           Enabling Transparent Hugepage madvise, will only provide a
 351           performance improvement benefit to the applications using
 352           madvise(MADV_HUGEPAGE) but it won't risk to increase the
 353           memory footprint of applications without a guaranteed
 354           benefit.
 355 endchoice
 356
 357 config CROSS_MEMORY_ATTACH
 358         bool "Cross Memory Support"
 359         depends on MMU
 360         default y
 361         help
 362           Enabling this option adds the system calls process_vm_readv and
 363           process_vm_writev which allow a process with the correct privileges
 364           to directly read from or write to to another process's address space.
 365           See the man page for more details.
 366
 367 #
 368 # UP and nommu archs use km based percpu allocator
 369 #
 370 config NEED_PER_CPU_KM
 371         depends on !SMP
 372         bool
 373         default y
 374
 375 config CLEANCACHE
 376         bool "Enable cleancache driver to cache clean pages if tmem is present"
 377         default n
 378         help
 379           Cleancache can be thought of as a page-granularity victim cache
 380           for clean pages that the kernel's pageframe replacement algorithm
 381           (PFRA) would like to keep around, but can't since there isn't enough
 382           memory.  So when the PFRA "evicts" a page, it first attempts to use
 383           cleancache code to put the data contained in that page into
 384           "transcendent memory", memory that is not directly accessible or
 385           addressable by the kernel and is of unknown and possibly
 386           time-varying size.  And when a cleancache-enabled
 387           filesystem wishes to access a page in a file on disk, it first
 388           checks cleancache to see if it already contains it; if it does,
 389           the page is copied into the kernel and a disk access is avoided.
 390           When a transcendent memory driver is available (such as zcache or
 391           Xen transcendent memory), a significant I/O reduction
 392           may be achieved.  When none is available, all cleancache calls
 393           are reduced to a single pointer-compare-against-NULL resulting
 394           in a negligible performance hit.
 395
 396           If unsure, say Y to enable cleancache
 397
 398 config FRONTSWAP
 399         bool "Enable frontswap to cache swap pages if tmem is present"
 400         depends on SWAP
 401         default n
 402         help
 403           Frontswap is so named because it can be thought of as the opposite
 404           of a "backing" store for a swap device.  The data is stored into
 405           "transcendent memory", memory that is not directly accessible or
 406           addressable by the kernel and is of unknown and possibly
 407           time-varying size.  When space in transcendent memory is available,
 408           a significant swap I/O reduction may be achieved.  When none is
 409           available, all frontswap calls are reduced to a single pointer-
 410           compare-against-NULL resulting in a negligible performance hit
 411           and swap data is stored as normal on the matching swap device.
 412
 413           If unsure, say Y to enable frontswap.