menu "Memory Management options"

  config SELECT_MEMORY_MODEL
  	def_bool y

  	depends on ARCH_SELECT_MEMORY_MODEL

  choice
  	prompt "Memory model"

  	depends on SELECT_MEMORY_MODEL
  	default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT

  	default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT

  	default FLATMEM_MANUAL

  config FLATMEM_MANUAL

  	bool "Flat Memory"

  	depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE

  	help
  	  This option allows you to change some of the ways that
  	  Linux manages its memory internally.  Most users will
  	  only have one option here: FLATMEM.  This is normal
  	  and a correct option.

  	  Some users of more advanced features like NUMA and
  	  memory hotplug may have different options here.

  	  DISCONTIGMEM is a more mature, better tested system,

  	  but is incompatible with memory hotplug and may suffer
  	  decreased performance over SPARSEMEM.  If unsure between
  	  "Sparse Memory" and "Discontiguous Memory", choose
  	  "Discontiguous Memory".
  
  	  If unsure, choose this option (Flat Memory) over any other.

  config DISCONTIGMEM_MANUAL

  	bool "Discontiguous Memory"

  	depends on ARCH_DISCONTIGMEM_ENABLE
  	help

  	  This option provides enhanced support for discontiguous
  	  memory systems, over FLATMEM.  These systems have holes
  	  in their physical address spaces, and this option provides
  	  more efficient handling of these holes.  However, the vast
  	  majority of hardware has quite flat address spaces, and

  	  can have degraded performance from the extra overhead that

  	  this option imposes.
  
  	  Many NUMA configurations will have this as the only option.

  	  If unsure, choose "Flat Memory" over this option.

  config SPARSEMEM_MANUAL
  	bool "Sparse Memory"
  	depends on ARCH_SPARSEMEM_ENABLE
  	help
  	  This will be the only option for some systems, including
  	  memory hotplug systems.  This is normal.
  
  	  For many other systems, this will be an alternative to

  	  "Discontiguous Memory".  This option provides some potential

  	  performance benefits, along with decreased code complexity,
  	  but it is newer, and more experimental.
  
  	  If unsure, choose "Discontiguous Memory" or "Flat Memory"
  	  over this option.

  endchoice

  config DISCONTIGMEM
  	def_bool y
  	depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL

  config SPARSEMEM
  	def_bool y

  	depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL

  config FLATMEM
  	def_bool y

  	depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
  
  config FLAT_NODE_MEM_MAP
  	def_bool y
  	depends on !SPARSEMEM

  #
  # Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
  # to represent different areas of memory.  This variable allows
  # those dependencies to exist individually.
  #
  config NEED_MULTIPLE_NODES
  	def_bool y
  	depends on DISCONTIGMEM || NUMA

  
  config HAVE_MEMORY_PRESENT
  	def_bool y

  	depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM

  
  #

  # SPARSEMEM_EXTREME (which is the default) does some bootmem

  # allocations when memory_present() is called.  If this cannot

  # be done on your architecture, select this option.  However,
  # statically allocating the mem_section[] array can potentially
  # consume vast quantities of .bss, so be careful.
  #
  # This option will also potentially produce smaller runtime code
  # with gcc 3.4 and later.
  #
  config SPARSEMEM_STATIC

  	bool

  
  #

  # Architecture platforms which require a two level mem_section in SPARSEMEM

  # must select this option. This is usually for architecture platforms with
  # an extremely sparse physical address space.
  #

  config SPARSEMEM_EXTREME
  	def_bool y
  	depends on SPARSEMEM && !SPARSEMEM_STATIC

  config SPARSEMEM_VMEMMAP_ENABLE

  	bool

  
  config SPARSEMEM_VMEMMAP

  	bool "Sparse Memory virtual memmap"
  	depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
  	default y
  	help
  	 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
  	 pfn_to_page and page_to_pfn operations.  This is the most
  	 efficient option when sufficient kernel resources are available.

  config HAVE_MEMBLOCK

  	bool

  config HAVE_MEMBLOCK_NODE_MAP

  	bool

  config HAVE_MEMBLOCK_PHYS_MAP

  	bool

  config HAVE_GENERIC_GUP

  	bool

  config ARCH_DISCARD_MEMBLOCK

  	bool

  config NO_BOOTMEM

  	bool

  config MEMORY_ISOLATION

  	bool

  #
  # Only be set on architectures that have completely implemented memory hotplug
  # feature. If you are not sure, don't touch it.
  #
  config HAVE_BOOTMEM_INFO_NODE
  	def_bool n

  # eventually, we can have this option just 'select SPARSEMEM'
  config MEMORY_HOTPLUG
  	bool "Allow for memory hot-add"

  	depends on SPARSEMEM || X86_64_ACPI_NUMA

  	depends on ARCH_ENABLE_MEMORY_HOTPLUG

  config MEMORY_HOTPLUG_SPARSE
  	def_bool y
  	depends on SPARSEMEM && MEMORY_HOTPLUG

  config MEMORY_HOTPLUG_DEFAULT_ONLINE
          bool "Online the newly added memory blocks by default"
          default n
          depends on MEMORY_HOTPLUG
          help
  	  This option sets the default policy setting for memory hotplug
  	  onlining policy (/sys/devices/system/memory/auto_online_blocks) which
  	  determines what happens to newly added memory regions. Policy setting
  	  can always be changed at runtime.
  	  See Documentation/memory-hotplug.txt for more information.
  
  	  Say Y here if you want all hot-plugged memory blocks to appear in
  	  'online' state by default.
  	  Say N here if you want the default policy to keep all hot-plugged
  	  memory blocks in 'offline' state.

  config MEMORY_HOTREMOVE
  	bool "Allow for memory hot remove"

  	select MEMORY_ISOLATION

  	select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)

  	depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
  	depends on MIGRATION

  # Heavily threaded applications may benefit from splitting the mm-wide
  # page_table_lock, so that faults on different parts of the user address
  # space can be handled with less contention: split it at this NR_CPUS.
  # Default to 4 for wider testing, though 8 might be more appropriate.
  # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.

  # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.

  # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.

  #
  config SPLIT_PTLOCK_CPUS
  	int

  	default "999999" if !MMU

  	default "999999" if ARM && !CPU_CACHE_VIPT
  	default "999999" if PARISC && !PA20

  	default "4"

  config ARCH_ENABLE_SPLIT_PMD_PTLOCK

  	bool

  #

  # support for memory balloon
  config MEMORY_BALLOON

  	bool

  
  #

  # support for memory balloon compaction
  config BALLOON_COMPACTION
  	bool "Allow for balloon memory compaction/migration"
  	def_bool y

  	depends on COMPACTION && MEMORY_BALLOON

  	help
  	  Memory fragmentation introduced by ballooning might reduce
  	  significantly the number of 2MB contiguous memory blocks that can be
  	  used within a guest, thus imposing performance penalties associated
  	  with the reduced number of transparent huge pages that could be used
  	  by the guest workload. Allowing the compaction & migration for memory
  	  pages enlisted as being part of memory balloon devices avoids the
  	  scenario aforementioned and helps improving memory defragmentation.
  
  #

  # support for memory compaction
  config COMPACTION
  	bool "Allow for memory compaction"

  	def_bool y

  	select MIGRATION

  	depends on MMU

  	help

            Compaction is the only memory management component to form
            high order (larger physically contiguous) memory blocks
            reliably. The page allocator relies on compaction heavily and
            the lack of the feature can lead to unexpected OOM killer
            invocations for high order memory requests. You shouldn't
            disable this option unless there really is a strong reason for
            it and then we would be really interested to hear about that at
            linux-mm@kvack.org.

  
  #

  # support for page migration
  #
  config MIGRATION

  	bool "Page migration"

  	def_bool y

  	depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU

  	help
  	  Allows the migration of the physical location of pages of processes

  	  while the virtual addresses are not changed. This is useful in
  	  two situations. The first is on NUMA systems to put pages nearer
  	  to the processors accessing. The second is when allocating huge
  	  pages as migration can relocate pages to satisfy a huge page
  	  allocation instead of reclaiming.

  config ARCH_ENABLE_HUGEPAGE_MIGRATION

  	bool

  config ARCH_ENABLE_THP_MIGRATION
  	bool

  config PHYS_ADDR_T_64BIT

  	def_bool 64BIT

  config BOUNCE

  	bool "Enable bounce buffers"
  	default y

  	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)

  	help
  	  Enable bounce buffers for devices that cannot access
  	  the full range of memory available to the CPU. Enabled
  	  by default when ZONE_DMA or HIGHMEM is selected, but you
  	  may say n to override this.

  config NR_QUICK
  	int
  	depends on QUICKLIST
  	default "1"

  
  config VIRT_TO_BUS

  	bool
  	help
  	  An architecture should select this if it implements the
  	  deprecated interface virt_to_bus().  All new architectures
  	  should probably not select this.

  
  config MMU_NOTIFIER
  	bool

  	select SRCU

  config KSM
  	bool "Enable KSM for page merging"
  	depends on MMU
  	help
  	  Enable Kernel Samepage Merging: KSM periodically scans those areas
  	  of an application's address space that an app has advised may be
  	  mergeable.  When it finds pages of identical content, it replaces

  	  the many instances by a single page with that content, so

  	  saving memory until one or another app needs to modify the content.
  	  Recommended for use with KVM, or with other duplicative applications.

  	  See Documentation/vm/ksm.rst for more information: KSM is inactive

  	  until a program has madvised that an area is MADV_MERGEABLE, and
  	  root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).

  config DEFAULT_MMAP_MIN_ADDR
          int "Low address space to protect from user allocation"

  	depends on MMU

          default 4096
          help
  	  This is the portion of low virtual memory which should be protected
  	  from userspace allocation.  Keeping a user from writing to low pages
  	  can help reduce the impact of kernel NULL pointer bugs.
  
  	  For most ia64, ppc64 and x86 users with lots of address space
  	  a value of 65536 is reasonable and should cause no problems.
  	  On arm and other archs it should not be higher than 32768.

  	  Programs which use vm86 functionality or have some need to map
  	  this low address space will need CAP_SYS_RAWIO or disable this
  	  protection by setting the value to 0.

  
  	  This value can be changed after boot using the
  	  /proc/sys/vm/mmap_min_addr tunable.

  config ARCH_SUPPORTS_MEMORY_FAILURE
  	bool

  config MEMORY_FAILURE
  	depends on MMU

  	depends on ARCH_SUPPORTS_MEMORY_FAILURE

  	bool "Enable recovery from hardware memory errors"

  	select MEMORY_ISOLATION

  	select RAS

  	help
  	  Enables code to recover from some memory failures on systems
  	  with MCA recovery. This allows a system to continue running
  	  even when some of its memory has uncorrected errors. This requires
  	  special hardware support and typically ECC memory.

  config HWPOISON_INJECT

  	tristate "HWPoison pages injector"

  	depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS

  	select PROC_PAGE_MONITOR

  config NOMMU_INITIAL_TRIM_EXCESS
  	int "Turn on mmap() excess space trimming before booting"
  	depends on !MMU
  	default 1
  	help
  	  The NOMMU mmap() frequently needs to allocate large contiguous chunks
  	  of memory on which to store mappings, but it can only ask the system
  	  allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
  	  more than it requires.  To deal with this, mmap() is able to trim off
  	  the excess and return it to the allocator.
  
  	  If trimming is enabled, the excess is trimmed off and returned to the
  	  system allocator, which can cause extra fragmentation, particularly
  	  if there are a lot of transient processes.
  
  	  If trimming is disabled, the excess is kept, but not used, which for
  	  long-term mappings means that the space is wasted.
  
  	  Trimming can be dynamically controlled through a sysctl option
  	  (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
  	  excess pages there must be before trimming should occur, or zero if
  	  no trimming is to occur.
  
  	  This option specifies the initial value of this option.  The default
  	  of 1 says that all excess pages should be trimmed.
  
  	  See Documentation/nommu-mmap.txt for more information.

  config TRANSPARENT_HUGEPAGE

  	bool "Transparent Hugepage Support"

  	depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE

  	select COMPACTION

  	select RADIX_TREE_MULTIORDER

  	help
  	  Transparent Hugepages allows the kernel to use huge pages and
  	  huge tlb transparently to the applications whenever possible.
  	  This feature can improve computing performance to certain
  	  applications by speeding up page faults during memory
  	  allocation, by reducing the number of tlb misses and by speeding
  	  up the pagetable walking.
  
  	  If memory constrained on embedded, you may want to say N.

  choice
  	prompt "Transparent Hugepage Support sysfs defaults"
  	depends on TRANSPARENT_HUGEPAGE
  	default TRANSPARENT_HUGEPAGE_ALWAYS
  	help
  	  Selects the sysfs defaults for Transparent Hugepage Support.
  
  	config TRANSPARENT_HUGEPAGE_ALWAYS
  		bool "always"
  	help
  	  Enabling Transparent Hugepage always, can increase the
  	  memory footprint of applications without a guaranteed
  	  benefit but it will work automatically for all applications.
  
  	config TRANSPARENT_HUGEPAGE_MADVISE
  		bool "madvise"
  	help
  	  Enabling Transparent Hugepage madvise, will only provide a
  	  performance improvement benefit to the applications using
  	  madvise(MADV_HUGEPAGE) but it won't risk to increase the
  	  memory footprint of applications without a guaranteed
  	  benefit.
  endchoice

  config ARCH_WANTS_THP_SWAP
         def_bool n
  
  config THP_SWAP
  	def_bool y

  	depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP

  	help
  	  Swap transparent huge pages in one piece, without splitting.

  	  XXX: For now, swap cluster backing transparent huge page
  	  will be split after swapout.

  
  	  For selection by architectures with reasonable THP sizes.

  config	TRANSPARENT_HUGE_PAGECACHE
  	def_bool y

  	depends on TRANSPARENT_HUGEPAGE

  
  #

  # UP and nommu archs use km based percpu allocator
  #
  config NEED_PER_CPU_KM
  	depends on !SMP
  	bool
  	default y

  
  config CLEANCACHE
  	bool "Enable cleancache driver to cache clean pages if tmem is present"
  	default n
  	help
  	  Cleancache can be thought of as a page-granularity victim cache
  	  for clean pages that the kernel's pageframe replacement algorithm
  	  (PFRA) would like to keep around, but can't since there isn't enough
  	  memory.  So when the PFRA "evicts" a page, it first attempts to use

  	  cleancache code to put the data contained in that page into

  	  "transcendent memory", memory that is not directly accessible or
  	  addressable by the kernel and is of unknown and possibly
  	  time-varying size.  And when a cleancache-enabled
  	  filesystem wishes to access a page in a file on disk, it first
  	  checks cleancache to see if it already contains it; if it does,
  	  the page is copied into the kernel and a disk access is avoided.
  	  When a transcendent memory driver is available (such as zcache or
  	  Xen transcendent memory), a significant I/O reduction
  	  may be achieved.  When none is available, all cleancache calls
  	  are reduced to a single pointer-compare-against-NULL resulting
  	  in a negligible performance hit.
  
  	  If unsure, say Y to enable cleancache

  
  config FRONTSWAP
  	bool "Enable frontswap to cache swap pages if tmem is present"
  	depends on SWAP
  	default n
  	help
  	  Frontswap is so named because it can be thought of as the opposite
  	  of a "backing" store for a swap device.  The data is stored into
  	  "transcendent memory", memory that is not directly accessible or
  	  addressable by the kernel and is of unknown and possibly
  	  time-varying size.  When space in transcendent memory is available,
  	  a significant swap I/O reduction may be achieved.  When none is
  	  available, all frontswap calls are reduced to a single pointer-
  	  compare-against-NULL resulting in a negligible performance hit
  	  and swap data is stored as normal on the matching swap device.
  
  	  If unsure, say Y to enable frontswap.

  
  config CMA
  	bool "Contiguous Memory Allocator"

  	depends on HAVE_MEMBLOCK && MMU

  	select MIGRATION
  	select MEMORY_ISOLATION
  	help
  	  This enables the Contiguous Memory Allocator which allows other
  	  subsystems to allocate big physically-contiguous blocks of memory.
  	  CMA reserves a region of memory and allows only movable pages to
  	  be allocated from it. This way, the kernel can use the memory for
  	  pagecache and when a subsystem requests for contiguous area, the
  	  allocated pages are migrated away to serve the contiguous request.
  
  	  If unsure, say "n".
  
  config CMA_DEBUG
  	bool "CMA debug messages (DEVELOPMENT)"
  	depends on DEBUG_KERNEL && CMA
  	help
  	  Turns on debug messages in CMA.  This produces KERN_DEBUG
  	  messages for every CMA call as well as various messages while
  	  processing calls such as dma_alloc_from_contiguous().
  	  This option does not affect warning and error messages.

  config CMA_DEBUGFS
  	bool "CMA debugfs interface"
  	depends on CMA && DEBUG_FS
  	help
  	  Turns on the DebugFS interface for CMA.

  config CMA_AREAS
  	int "Maximum count of the CMA areas"
  	depends on CMA
  	default 7
  	help
  	  CMA allows to create CMA areas for particular purpose, mainly,
  	  used as device private area. This parameter sets the maximum
  	  number of CMA area in the system.
  
  	  If unsure, leave the default value "7".

  config MEM_SOFT_DIRTY
  	bool "Track memory changes"
  	depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
  	select PROC_PAGE_MONITOR

  	help

  	  This option enables memory changes tracking by introducing a
  	  soft-dirty bit on pte-s. This bit it set when someone writes
  	  into a page just as regular dirty bit, but unlike the latter
  	  it can be cleared by hands.

  	  See Documentation/admin-guide/mm/soft-dirty.rst for more details.

  config ZSWAP
  	bool "Compressed cache for swap pages (EXPERIMENTAL)"
  	depends on FRONTSWAP && CRYPTO=y
  	select CRYPTO_LZO

  	select ZPOOL

  	default n
  	help
  	  A lightweight compressed cache for swap pages.  It takes
  	  pages that are in the process of being swapped out and attempts to
  	  compress them into a dynamically allocated RAM-based memory pool.
  	  This can result in a significant I/O reduction on swap device and,
  	  in the case where decompressing from RAM is faster that swap device
  	  reads, can also improve workload performance.
  
  	  This is marked experimental because it is a new feature (as of
  	  v3.11) that interacts heavily with memory reclaim.  While these
  	  interactions don't cause any known issues on simple memory setups,
  	  they have not be fully explored on the large set of potential
  	  configurations and workloads that exist.

  config ZPOOL
  	tristate "Common API for compressed memory storage"
  	default n

  	help

  	  Compressed memory storage API.  This allows using either zbud or
  	  zsmalloc.

  config ZBUD

  	tristate "Low (Up to 2x) density storage for compressed pages"

  	default n
  	help
  	  A special purpose allocator for storing compressed pages.
  	  It is designed to store up to two compressed pages per physical
  	  page.  While this design limits storage density, it has simple and
  	  deterministic reclaim properties that make it preferable to a higher
  	  density approach when reclaim will be used.

  config Z3FOLD
  	tristate "Up to 3x density storage for compressed pages"
  	depends on ZPOOL
  	default n
  	help
  	  A special purpose allocator for storing compressed pages.
  	  It is designed to store up to three compressed pages per physical
  	  page. It is a ZBUD derivative so the simplicity and determinism are
  	  still there.

  config ZSMALLOC

  	tristate "Memory allocator for compressed pages"

  	depends on MMU
  	default n
  	help
  	  zsmalloc is a slab-based memory allocator designed to store
  	  compressed RAM pages.  zsmalloc uses virtual memory mapping
  	  in order to reduce fragmentation.  However, this results in a
  	  non-standard allocator interface where a handle, not a pointer, is
  	  returned by an alloc().  This handle must be mapped in order to
  	  access the allocated space.
  
  config PGTABLE_MAPPING
  	bool "Use page table mapping to access object in zsmalloc"
  	depends on ZSMALLOC
  	help
  	  By default, zsmalloc uses a copy-based object mapping method to
  	  access allocations that span two pages. However, if a particular
  	  architecture (ex, ARM) performs VM mapping faster than copying,
  	  then you should select this. This causes zsmalloc to use page table
  	  mapping rather than copying for object mapping.

  	  You can check speed with zsmalloc benchmark:
  	  https://github.com/spartacus06/zsmapbench

  config ZSMALLOC_STAT
  	bool "Export zsmalloc statistics"
  	depends on ZSMALLOC
  	select DEBUG_FS
  	help
  	  This option enables code in the zsmalloc to collect various
  	  statistics about whats happening in zsmalloc and exports that
  	  information to userspace via debugfs.
  	  If unsure, say N.

  config GENERIC_EARLY_IOREMAP
  	bool

  
  config MAX_STACK_SIZE_MB
  	int "Maximum user stack size for 32-bit processes (MB)"
  	default 80

  	range 8 2048
  	depends on STACK_GROWSUP && (!64BIT || COMPAT)
  	help
  	  This is the maximum stack size in Megabytes in the VM layout of 32-bit
  	  user processes when the stack grows upwards (currently only on parisc

  	  arch). The stack will be located at the highest memory address minus
  	  the given value, unless the RLIMIT_STACK hard limit is changed to a
  	  smaller value in which case that is used.

  
  	  A sane initial value is 80 MB.

  config DEFERRED_STRUCT_PAGE_INIT

  	bool "Defer initialisation of struct pages to kthreads"

  	default n

  	depends on NO_BOOTMEM

  	depends on SPARSEMEM

  	depends on !NEED_PER_CPU_KM

  	depends on 64BIT

  	help
  	  Ordinarily all struct pages are initialised during early boot in a
  	  single thread. On very large machines this can take a considerable
  	  amount of time. If this option is set, large machines will bring up
  	  a subset of memmap at boot and then initialise the rest in parallel

  	  by starting one-off "pgdatinitX" kernel thread for each node X. This
  	  has a potential performance impact on processes running early in the
  	  lifetime of the system until these kthreads finish the
  	  initialisation.

  config IDLE_PAGE_TRACKING
  	bool "Enable idle page tracking"
  	depends on SYSFS && MMU
  	select PAGE_EXTENSION if !64BIT
  	help
  	  This feature allows to estimate the amount of user pages that have
  	  not been touched during a given period of time. This information can
  	  be useful to tune memory cgroup limits and/or for job placement
  	  within a compute cluster.

  	  See Documentation/admin-guide/mm/idle_page_tracking.rst for
  	  more details.

  # arch_add_memory() comprehends device memory
  config ARCH_HAS_ZONE_DEVICE
  	bool

  config ZONE_DEVICE

  	bool "Device memory (pmem, HMM, etc...) hotplug support"

  	depends on MEMORY_HOTPLUG
  	depends on MEMORY_HOTREMOVE

  	depends on SPARSEMEM_VMEMMAP

  	depends on ARCH_HAS_ZONE_DEVICE

  	select RADIX_TREE_MULTIORDER

  
  	help
  	  Device memory hotplug support allows for establishing pmem,
  	  or other device driver discovered memory regions, in the
  	  memmap. This allows pfn_to_page() lookups of otherwise
  	  "device-physical" addresses which is needed for using a DAX
  	  mapping in an O_DIRECT operation, among other things.
  
  	  If FS_DAX is enabled, then say Y.

  config ARCH_HAS_HMM
  	bool
  	default y
  	depends on (X86_64 || PPC64)
  	depends on ZONE_DEVICE
  	depends on MMU && 64BIT
  	depends on MEMORY_HOTPLUG
  	depends on MEMORY_HOTREMOVE
  	depends on SPARSEMEM_VMEMMAP

  config MIGRATE_VMA_HELPER
  	bool

  config DEV_PAGEMAP_OPS
  	bool

  config HMM
  	bool

  	select MIGRATE_VMA_HELPER

  config HMM_MIRROR
  	bool "HMM mirror CPU page table into a device page table"
  	depends on ARCH_HAS_HMM
  	select MMU_NOTIFIER
  	select HMM
  	help
  	  Select HMM_MIRROR if you want to mirror range of the CPU page table of a
  	  process into a device page table. Here, mirror means "keep synchronized".
  	  Prerequisites: the device must provide the ability to write-protect its
  	  page tables (at PAGE_SIZE granularity), and must be able to recover from
  	  the resulting potential page faults.

  config DEVICE_PRIVATE
  	bool "Unaddressable device memory (GPU memory, ...)"
  	depends on ARCH_HAS_HMM

  	select HMM

  	select DEV_PAGEMAP_OPS

  
  	help
  	  Allows creation of struct pages to represent unaddressable device
  	  memory; i.e., memory that is only accessible from the device (or
  	  group of devices). You likely also want to select HMM_MIRROR.

  config DEVICE_PUBLIC
  	bool "Addressable device memory (like GPU memory)"
  	depends on ARCH_HAS_HMM
  	select HMM

  	select DEV_PAGEMAP_OPS

  
  	help
  	  Allows creation of struct pages to represent addressable device
  	  memory; i.e., memory that is accessible from both the device and
  	  the CPU

  config FRAME_VECTOR
  	bool

  
  config ARCH_USES_HIGH_VMA_FLAGS
  	bool

  config ARCH_HAS_PKEYS
  	bool

  
  config PERCPU_STATS
  	bool "Collect percpu memory statistics"
  	default n
  	help
  	  This feature collects and exposes statistics via debugfs. The
  	  information includes global and per chunk statistics, which can
  	  be used to help understand percpu memory usage.

  
  config GUP_BENCHMARK
  	bool "Enable infrastructure for get_user_pages_fast() benchmarking"
  	default n
  	help
  	  Provides /sys/kernel/debug/gup_benchmark that helps with testing
  	  performance of get_user_pages_fast().
  
  	  See tools/testing/selftests/vm/gup_benchmark.c

  
  config ARCH_HAS_PTE_SPECIAL
  	bool

  
  endmenu