linux-imx/mm/Kconfig

SPDX-License-Identifier: GPL-2.0-only

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 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 selected by the architecture configuration. This is normal.

config FLATMEM_MANUAL bool "Flat Memory" depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE help This option is best suited for non-NUMA systems with flat address space. The FLATMEM is the most efficient system in terms of performance and resource consumption and it is the best option for smaller systems.

  For systems that have holes in their physical address
  spaces and for features like NUMA and memory hotplug,
  choose "Sparse 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.

  Although "Discontiguous Memory" is still used by several
  architectures, it is considered deprecated in favor of
  "Sparse Memory".

  If unsure, choose "Sparse 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 hot-plug systems. This is normal.

  This option provides efficient support for systems with
  holes is their physical address space and allows memory
  hot-plug and hot-remove.

  If unsure, choose "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_NODE_MAP bool

config HAVE_MEMBLOCK_PHYS_MAP bool

config HAVE_FAST_GUP depends on MMU bool

config ARCH_KEEP_MEMBLOCK bool

Keep arch NUMA mapping infrastructure post-init.

config NUMA_KEEP_MEMINFO 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 select NUMA_KEEP_MEMINFO if NUMA

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" 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/admin-guide/mm/memory-hotplug.rst 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 free page reporting

config PAGE_REPORTING bool "Free page reporting" def_bool n help Free page reporting allows for the incremental acquisition of free pages from the buddy allocator for the purpose of reporting those pages to another entity, such as a hypervisor, so that the memory can be freed within the host for other uses.

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 CONTIG_ALLOC def_bool (MEMORY_ISOLATION && COMPACTION) || CMA

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 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 select INTERVAL_TREE

config KSM bool "Enable KSM for page merging" depends on MMU select XXHASH 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 XARRAY_MULTI 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.

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" 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 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 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 ZPOOL 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.

choice prompt "Compressed cache for swap pages default compressor" depends on ZSWAP default ZSWAP_COMPRESSOR_DEFAULT_LZO help Selects the default compression algorithm for the compressed cache for swap pages.

  For an overview what kind of performance can be expected from
  a particular compression algorithm please refer to the benchmarks
  available at the following LWN page:
  https://lwn.net/Articles/751795/

  If in doubt, select 'LZO'.

  The selection made here can be overridden by using the kernel
  command line 'zswap.compressor=' option.

config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE bool "Deflate" select CRYPTO_DEFLATE help Use the Deflate algorithm as the default compression algorithm.

config ZSWAP_COMPRESSOR_DEFAULT_LZO bool "LZO" select CRYPTO_LZO help Use the LZO algorithm as the default compression algorithm.

config ZSWAP_COMPRESSOR_DEFAULT_842 bool "842" select CRYPTO_842 help Use the 842 algorithm as the default compression algorithm.

config ZSWAP_COMPRESSOR_DEFAULT_LZ4 bool "LZ4" select CRYPTO_LZ4 help Use the LZ4 algorithm as the default compression algorithm.

config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC bool "LZ4HC" select CRYPTO_LZ4HC help Use the LZ4HC algorithm as the default compression algorithm.

config ZSWAP_COMPRESSOR_DEFAULT_ZSTD bool "zstd" select CRYPTO_ZSTD help Use the zstd algorithm as the default compression algorithm. endchoice

config ZSWAP_COMPRESSOR_DEFAULT string depends on ZSWAP default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO default "842" if ZSWAP_COMPRESSOR_DEFAULT_842 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD default ""

choice prompt "Compressed cache for swap pages default allocator" depends on ZSWAP default ZSWAP_ZPOOL_DEFAULT_ZBUD help Selects the default allocator for the compressed cache for swap pages. The default is 'zbud' for compatibility, however please do read the description of each of the allocators below before making a right choice.

  The selection made here can be overridden by using the kernel
  command line 'zswap.zpool=' option.

config ZSWAP_ZPOOL_DEFAULT_ZBUD bool "zbud" select ZBUD help Use the zbud allocator as the default allocator.

config ZSWAP_ZPOOL_DEFAULT_Z3FOLD bool "z3fold" select Z3FOLD help Use the z3fold allocator as the default allocator.

config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC bool "zsmalloc" select ZSMALLOC help Use the zsmalloc allocator as the default allocator. endchoice

config ZSWAP_ZPOOL_DEFAULT string depends on ZSWAP default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC default ""

config ZSWAP_DEFAULT_ON bool "Enable the compressed cache for swap pages by default" depends on ZSWAP help If selected, the compressed cache for swap pages will be enabled at boot, otherwise it will be disabled.

  The selection made here can be overridden by using the kernel
  command line 'zswap.enabled=' option.

config ZPOOL tristate "Common API for compressed memory storage" help Compressed memory storage API. This allows using either zbud or zsmalloc.

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

config ARCH_HAS_PTE_DEVMAP 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_PTE_DEVMAP select XARRAY_MULTI

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 DEV_PAGEMAP_OPS bool

Helpers to mirror range of the CPU page tables of a process into device page

tables.

config HMM_MIRROR bool depends on MMU

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

config ARCH_USES_HIGH_VMA_FLAGS bool config ARCH_HAS_PKEYS bool

config PERCPU_STATS bool "Collect percpu memory statistics" 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" 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 GUP_GET_PTE_LOW_HIGH bool

config READ_ONLY_THP_FOR_FS bool "Read-only THP for filesystems (EXPERIMENTAL)" depends on TRANSPARENT_HUGEPAGE && SHMEM

help
  Allow khugepaged to put read-only file-backed pages in THP.

  This is marked experimental because it is a new feature. Write
  support of file THPs will be developed in the next few release
  cycles.

config ARCH_HAS_PTE_SPECIAL bool

Some architectures require a special hugepage directory format that is

required to support multiple hugepage sizes. For example a4fe3ce76

"powerpc/mm: Allow more flexible layouts for hugepage pagetables"

introduced it on powerpc. This allows for a more flexible hugepage

pagetable layouts.

config ARCH_HAS_HUGEPD bool

config MAPPING_DIRTY_HELPERS bool

endmenu