Merge tag 'trace-printf-v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/trace...

[drm/drm-misc.git] / mm / Kconfig

# SPDX-License-Identifier: GPL-2.0-only

menu "Memory Management options"

#
# For some reason microblaze and nios2 hard code SWAP=n.  Hopefully we can
# add proper SWAP support to them, in which case this can be remove.
#
config ARCH_NO_SWAP
        bool

config ZPOOL
        bool

menuconfig SWAP
        bool "Support for paging of anonymous memory (swap)"
        depends on MMU && BLOCK && !ARCH_NO_SWAP
        default y
        help
          This option allows you to choose whether you want to have support
          for so called swap devices or swap files in your kernel that are
          used to provide more virtual memory than the actual RAM present
          in your computer.  If unsure say Y.

config ZSWAP
        bool "Compressed cache for swap pages"
        depends on SWAP
        select CRYPTO
        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 than swap device
          reads, can also improve workload performance.

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 ZSWAP_SHRINKER_DEFAULT_ON
        bool "Shrink the zswap pool on memory pressure"
        depends on ZSWAP
        default n
        help
          If selected, the zswap shrinker will be enabled, and the pages
          stored in the zswap pool will become available for reclaim (i.e
          written back to the backing swap device) on memory pressure.

          This means that zswap writeback could happen even if the pool is
          not yet full, or the cgroup zswap limit has not been reached,
          reducing the chance that cold pages will reside in the zswap pool
          and consume memory indefinitely.

choice
        prompt "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 "Default allocator"
        depends on ZSWAP
        default ZSWAP_ZPOOL_DEFAULT_ZSMALLOC if MMU
        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_DEPRECATED
        bool "z3foldi (DEPRECATED)"
        select Z3FOLD_DEPRECATED
        help
          Use the z3fold allocator as the default allocator.

          Deprecated and scheduled for removal in a few cycles,
          see CONFIG_Z3FOLD_DEPRECATED.

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_DEPRECATED
       default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
       default ""

config ZBUD
        tristate "2:1 compression allocator (zbud)"
        depends on ZSWAP
        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_DEPRECATED
        tristate "3:1 compression allocator (z3fold) (DEPRECATED)"
        depends on ZSWAP
        help
          Deprecated and scheduled for removal in a few cycles. If you have
          a good reason for using Z3FOLD over ZSMALLOC, please contact
          linux-mm@kvack.org and the zswap maintainers.

          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 Z3FOLD
        tristate
        default y if Z3FOLD_DEPRECATED=y
        default m if Z3FOLD_DEPRECATED=m
        depends on Z3FOLD_DEPRECATED

config ZSMALLOC
        tristate
        prompt "N:1 compression allocator (zsmalloc)" if (ZSWAP || ZRAM)
        depends on MMU
        help
          zsmalloc is a slab-based memory allocator designed to store
          pages of various compression levels efficiently. It achieves
          the highest storage density with the least amount of fragmentation.

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 what's happening in zsmalloc and exports that
          information to userspace via debugfs.
          If unsure, say N.

config ZSMALLOC_CHAIN_SIZE
        int "Maximum number of physical pages per-zspage"
        default 8
        range 4 16
        depends on ZSMALLOC
        help
          This option sets the upper limit on the number of physical pages
          that a zmalloc page (zspage) can consist of. The optimal zspage
          chain size is calculated for each size class during the
          initialization of the pool.

          Changing this option can alter the characteristics of size classes,
          such as the number of pages per zspage and the number of objects
          per zspage. This can also result in different configurations of
          the pool, as zsmalloc merges size classes with similar
          characteristics.

          For more information, see zsmalloc documentation.

menu "Slab allocator options"

config SLUB
        def_bool y

config SLUB_TINY
        bool "Configure for minimal memory footprint"
        depends on EXPERT
        select SLAB_MERGE_DEFAULT
        help
           Configures the slab allocator in a way to achieve minimal memory
           footprint, sacrificing scalability, debugging and other features.
           This is intended only for the smallest system that had used the
           SLOB allocator and is not recommended for systems with more than
           16MB RAM.

           If unsure, say N.

config SLAB_MERGE_DEFAULT
        bool "Allow slab caches to be merged"
        default y
        help
          For reduced kernel memory fragmentation, slab caches can be
          merged when they share the same size and other characteristics.
          This carries a risk of kernel heap overflows being able to
          overwrite objects from merged caches (and more easily control
          cache layout), which makes such heap attacks easier to exploit
          by attackers. By keeping caches unmerged, these kinds of exploits
          can usually only damage objects in the same cache. To disable
          merging at runtime, "slab_nomerge" can be passed on the kernel
          command line.

config SLAB_FREELIST_RANDOM
        bool "Randomize slab freelist"
        depends on !SLUB_TINY
        help
          Randomizes the freelist order used on creating new pages. This
          security feature reduces the predictability of the kernel slab
          allocator against heap overflows.

config SLAB_FREELIST_HARDENED
        bool "Harden slab freelist metadata"
        depends on !SLUB_TINY
        help
          Many kernel heap attacks try to target slab cache metadata and
          other infrastructure. This options makes minor performance
          sacrifices to harden the kernel slab allocator against common
          freelist exploit methods.

config SLAB_BUCKETS
        bool "Support allocation from separate kmalloc buckets"
        depends on !SLUB_TINY
        default SLAB_FREELIST_HARDENED
        help
          Kernel heap attacks frequently depend on being able to create
          specifically-sized allocations with user-controlled contents
          that will be allocated into the same kmalloc bucket as a
          target object. To avoid sharing these allocation buckets,
          provide an explicitly separated set of buckets to be used for
          user-controlled allocations. This may very slightly increase
          memory fragmentation, though in practice it's only a handful
          of extra pages since the bulk of user-controlled allocations
          are relatively long-lived.

          If unsure, say Y.

config SLUB_STATS
        default n
        bool "Enable performance statistics"
        depends on SYSFS && !SLUB_TINY
        help
          The statistics are useful to debug slab allocation behavior in
          order find ways to optimize the allocator. This should never be
          enabled for production use since keeping statistics slows down
          the allocator by a few percentage points. The slabinfo command
          supports the determination of the most active slabs to figure
          out which slabs are relevant to a particular load.
          Try running: slabinfo -DA

config SLUB_CPU_PARTIAL
        default y
        depends on SMP && !SLUB_TINY
        bool "Enable per cpu partial caches"
        help
          Per cpu partial caches accelerate objects allocation and freeing
          that is local to a processor at the price of more indeterminism
          in the latency of the free. On overflow these caches will be cleared
          which requires the taking of locks that may cause latency spikes.
          Typically one would choose no for a realtime system.

config RANDOM_KMALLOC_CACHES
        default n
        depends on !SLUB_TINY
        bool "Randomize slab caches for normal kmalloc"
        help
          A hardening feature that creates multiple copies of slab caches for
          normal kmalloc allocation and makes kmalloc randomly pick one based
          on code address, which makes the attackers more difficult to spray
          vulnerable memory objects on the heap for the purpose of exploiting
          memory vulnerabilities.

          Currently the number of copies is set to 16, a reasonably large value
          that effectively diverges the memory objects allocated for different
          subsystems or modules into different caches, at the expense of a
          limited degree of memory and CPU overhead that relates to hardware and
          system workload.

endmenu # Slab allocator options

config SHUFFLE_PAGE_ALLOCATOR
        bool "Page allocator randomization"
        default SLAB_FREELIST_RANDOM && ACPI_NUMA
        help
          Randomization of the page allocator improves the average
          utilization of a direct-mapped memory-side-cache. See section
          5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
          6.2a specification for an example of how a platform advertises
          the presence of a memory-side-cache. There are also incidental
          security benefits as it reduces the predictability of page
          allocations to compliment SLAB_FREELIST_RANDOM, but the
          default granularity of shuffling on the MAX_PAGE_ORDER i.e, 10th
          order of pages is selected based on cache utilization benefits
          on x86.

          While the randomization improves cache utilization it may
          negatively impact workloads on platforms without a cache. For
          this reason, by default, the randomization is not enabled even
          if SHUFFLE_PAGE_ALLOCATOR=y. The randomization may be force enabled
          with the 'page_alloc.shuffle' kernel command line parameter.

          Say Y if unsure.

config COMPAT_BRK
        bool "Disable heap randomization"
        default y
        help
          Randomizing heap placement makes heap exploits harder, but it
          also breaks ancient binaries (including anything libc5 based).
          This option changes the bootup default to heap randomization
          disabled, and can be overridden at runtime by setting
          /proc/sys/kernel/randomize_va_space to 2.

          On non-ancient distros (post-2000 ones) N is usually a safe choice.

config MMAP_ALLOW_UNINITIALIZED
        bool "Allow mmapped anonymous memory to be uninitialized"
        depends on EXPERT && !MMU
        default n
        help
          Normally, and according to the Linux spec, anonymous memory obtained
          from mmap() has its contents cleared before it is passed to
          userspace.  Enabling this config option allows you to request that
          mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
          providing a huge performance boost.  If this option is not enabled,
          then the flag will be ignored.

          This is taken advantage of by uClibc's malloc(), and also by
          ELF-FDPIC binfmt's brk and stack allocator.

          Because of the obvious security issues, this option should only be
          enabled on embedded devices where you control what is run in
          userspace.  Since that isn't generally a problem on no-MMU systems,
          it is normally safe to say Y here.

          See Documentation/admin-guide/mm/nommu-mmap.rst for more information.

config SELECT_MEMORY_MODEL
        def_bool y
        depends on ARCH_SELECT_MEMORY_MODEL

choice
        prompt "Memory model"
        depends on SELECT_MEMORY_MODEL
        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_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 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 SPARSEMEM
        def_bool y
        depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL

config FLATMEM
        def_bool y
        depends on !SPARSEMEM || FLATMEM_MANUAL

#
# SPARSEMEM_EXTREME (which is the default) does some bootmem
# allocations when sparse_init() 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.
#
# Select this config option from the architecture Kconfig, if it is preferred
# to enable the feature of HugeTLB/dev_dax vmemmap optimization.
#
config ARCH_WANT_OPTIMIZE_DAX_VMEMMAP
        bool

config ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP
        bool

config HAVE_MEMBLOCK_PHYS_MAP
        bool

config HAVE_GUP_FAST
        depends on MMU
        bool

# Don't discard allocated memory used to track "memory" and "reserved" memblocks
# after early boot, so it can still be used to test for validity of memory.
# Also, memblocks are updated with memory hot(un)plug.
config ARCH_KEEP_MEMBLOCK
        bool

# Keep arch NUMA mapping infrastructure post-init.
config NUMA_KEEP_MEMINFO
        bool

config MEMORY_ISOLATION
        bool

# IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked
# IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via
# /dev/mem.
config EXCLUSIVE_SYSTEM_RAM
        def_bool y
        depends on !DEVMEM || STRICT_DEVMEM

#
# 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

config ARCH_ENABLE_MEMORY_HOTPLUG
        bool

config ARCH_ENABLE_MEMORY_HOTREMOVE
        bool

# eventually, we can have this option just 'select SPARSEMEM'
menuconfig MEMORY_HOTPLUG
        bool "Memory hotplug"
        select MEMORY_ISOLATION
        depends on SPARSEMEM
        depends on ARCH_ENABLE_MEMORY_HOTPLUG
        depends on 64BIT
        select NUMA_KEEP_MEMINFO if NUMA

if 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 HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
        depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
        depends on MIGRATION

config MHP_MEMMAP_ON_MEMORY
        def_bool y
        depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
        depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE

endif # MEMORY_HOTPLUG

config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
       bool

# 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.
# SPARC32 allocates multiple pte tables within a single page, and therefore
# a per-page lock leads to problems when multiple tables need to be locked
# at the same time (e.g. copy_page_range()).
# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
#
config SPLIT_PTE_PTLOCKS
        def_bool y
        depends on MMU
        depends on SMP
        depends on NR_CPUS >= 4
        depends on !ARM || CPU_CACHE_VIPT
        depends on !PARISC || PA20
        depends on !SPARC32

config ARCH_ENABLE_SPLIT_PMD_PTLOCK
        bool

config SPLIT_PMD_PTLOCKS
        def_bool y
        depends on SPLIT_PTE_PTLOCKS && ARCH_ENABLE_SPLIT_PMD_PTLOCK

#
# support for memory balloon
config MEMORY_BALLOON
        bool

#
# support for memory balloon compaction
config BALLOON_COMPACTION
        bool "Allow for balloon memory compaction/migration"
        default 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"
        default 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.

config COMPACT_UNEVICTABLE_DEFAULT
        int
        depends on COMPACTION
        default 0 if PREEMPT_RT
        default 1

#
# support for free page reporting
config PAGE_REPORTING
        bool "Free page reporting"
        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"
        default 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 DEVICE_MIGRATION
        def_bool MIGRATION && ZONE_DEVICE

config ARCH_ENABLE_HUGEPAGE_MIGRATION
        bool

config ARCH_ENABLE_THP_MIGRATION
        bool

config HUGETLB_PAGE_SIZE_VARIABLE
        def_bool n
        help
          Allows the pageblock_order value to be dynamic instead of just standard
          HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available
          on a platform.

          Note that the pageblock_order cannot exceed MAX_PAGE_ORDER and will be
          clamped down to MAX_PAGE_ORDER.

config CONTIG_ALLOC
        def_bool (MEMORY_ISOLATION && COMPACTION) || CMA

config PCP_BATCH_SCALE_MAX
        int "Maximum scale factor of PCP (Per-CPU pageset) batch allocate/free"
        default 5
        range 0 6
        help
          In page allocator, PCP (Per-CPU pageset) is refilled and drained in
          batches.  The batch number is scaled automatically to improve page
          allocation/free throughput.  But too large scale factor may hurt
          latency.  This option sets the upper limit of scale factor to limit
          the maximum latency.

config PHYS_ADDR_T_64BIT
        def_bool 64BIT

config BOUNCE
        bool "Enable bounce buffers"
        default y
        depends on BLOCK && MMU && HIGHMEM
        help
          Enable bounce buffers for devices that cannot access the full range of
          memory available to the CPU. Enabled by default when HIGHMEM is
          selected, but you may say n to override this.

config MMU_NOTIFIER
        bool
        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/mm/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 arm64, 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/admin-guide/mm/nommu-mmap.rst for more information.

config ARCH_WANT_GENERAL_HUGETLB
        bool

config ARCH_WANTS_THP_SWAP
        def_bool n

menuconfig TRANSPARENT_HUGEPAGE
        bool "Transparent Hugepage Support"
        depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT
        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.

if TRANSPARENT_HUGEPAGE

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.

        config TRANSPARENT_HUGEPAGE_NEVER
                bool "never"
        help
          Disable Transparent Hugepage by default. It can still be
          enabled at runtime via sysfs.
endchoice

config THP_SWAP
        def_bool y
        depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT
        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 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.

endif # TRANSPARENT_HUGEPAGE

#
# The architecture supports pgtable leaves that is larger than PAGE_SIZE
#
config PGTABLE_HAS_HUGE_LEAVES
        def_bool TRANSPARENT_HUGEPAGE || HUGETLB_PAGE

# TODO: Allow to be enabled without THP
config ARCH_SUPPORTS_HUGE_PFNMAP
        def_bool n
        depends on TRANSPARENT_HUGEPAGE

config ARCH_SUPPORTS_PMD_PFNMAP
        def_bool y
        depends on ARCH_SUPPORTS_HUGE_PFNMAP && HAVE_ARCH_TRANSPARENT_HUGEPAGE

config ARCH_SUPPORTS_PUD_PFNMAP
        def_bool y
        depends on ARCH_SUPPORTS_HUGE_PFNMAP && HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD

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

config NEED_PER_CPU_EMBED_FIRST_CHUNK
        bool

config NEED_PER_CPU_PAGE_FIRST_CHUNK
        bool

config USE_PERCPU_NUMA_NODE_ID
        bool

config HAVE_SETUP_PER_CPU_AREA
        bool

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

config CMA_SYSFS
        bool "CMA information through sysfs interface"
        depends on CMA && SYSFS
        help
          This option exposes some sysfs attributes to get information
          from CMA.

config CMA_AREAS
        int "Maximum count of the CMA areas"
        depends on CMA
        default 20 if NUMA
        default 8
        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 "8" in UMA and "20" in NUMA.

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 GENERIC_EARLY_IOREMAP
        bool

config STACK_MAX_DEFAULT_SIZE_MB
        int "Default maximum user stack size for 32-bit processes (MB)"
        default 100
        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) when the RLIMIT_STACK hard limit is unlimited.

          A sane initial value is 100 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
        depends on !KMSAN
        select PADATA
        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.
          This has a potential performance impact on tasks running early in the
          lifetime of the system until these kthreads finish the
          initialisation.

config PAGE_IDLE_FLAG
        bool
        select PAGE_EXTENSION if !64BIT
        help
          This adds PG_idle and PG_young flags to 'struct page'.  PTE Accessed
          bit writers can set the state of the bit in the flags so that PTE
          Accessed bit readers may avoid disturbance.

config IDLE_PAGE_TRACKING
        bool "Enable idle page tracking"
        depends on SYSFS && MMU
        select PAGE_IDLE_FLAG
        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.

# Architectures which implement cpu_dcache_is_aliasing() to query
# whether the data caches are aliased (VIVT or VIPT with dcache
# aliasing) need to select this.
config ARCH_HAS_CPU_CACHE_ALIASING
        bool

config ARCH_HAS_CACHE_LINE_SIZE
        bool

config ARCH_HAS_CURRENT_STACK_POINTER
        bool
        help
          In support of HARDENED_USERCOPY performing stack variable lifetime
          checking, an architecture-agnostic way to find the stack pointer
          is needed. Once an architecture defines an unsigned long global
          register alias named "current_stack_pointer", this config can be
          selected.

config ARCH_HAS_PTE_DEVMAP
        bool

config ARCH_HAS_ZONE_DMA_SET
        bool

config ZONE_DMA
        bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET
        default y if ARM64 || X86

config ZONE_DMA32
        bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET
        depends on !X86_32
        default y if ARM64

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.

#
# Helpers to mirror range of the CPU page tables of a process into device page
# tables.
#
config HMM_MIRROR
        bool
        depends on MMU

config GET_FREE_REGION
        bool

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

        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 VMAP_PFN
        bool

config ARCH_USES_HIGH_VMA_FLAGS
        bool
config ARCH_HAS_PKEYS
        bool

config ARCH_USES_PG_ARCH_2
        bool
config ARCH_USES_PG_ARCH_3
        bool

config VM_EVENT_COUNTERS
        default y
        bool "Enable VM event counters for /proc/vmstat" if EXPERT
        help
          VM event counters are needed for event counts to be shown.
          This option allows the disabling of the VM event counters
          on EXPERT systems.  /proc/vmstat will only show page counts
          if VM event counters are disabled.

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_TEST
        bool "Enable infrastructure for get_user_pages()-related unit tests"
        depends on DEBUG_FS
        help
          Provides /sys/kernel/debug/gup_test, which in turn provides a way
          to make ioctl calls that can launch kernel-based unit tests for
          the get_user_pages*() and pin_user_pages*() family of API calls.

          These tests include benchmark testing of the _fast variants of
          get_user_pages*() and pin_user_pages*(), as well as smoke tests of
          the non-_fast variants.

          There is also a sub-test that allows running dump_page() on any
          of up to eight pages (selected by command line args) within the
          range of user-space addresses. These pages are either pinned via
          pin_user_pages*(), or pinned via get_user_pages*(), as specified
          by other command line arguments.

          See tools/testing/selftests/mm/gup_test.c

comment "GUP_TEST needs to have DEBUG_FS enabled"
        depends on !GUP_TEST && !DEBUG_FS

config GUP_GET_PXX_LOW_HIGH
        bool

config DMAPOOL_TEST
        tristate "Enable a module to run time tests on dma_pool"
        depends on HAS_DMA
        help
          Provides a test module that will allocate and free many blocks of
          various sizes and report how long it takes. This is intended to
          provide a consistent way to measure how changes to the
          dma_pool_alloc/free routines affect performance.

config ARCH_HAS_PTE_SPECIAL
        bool

config MAPPING_DIRTY_HELPERS
        bool

config KMAP_LOCAL
        bool

config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY
        bool

# struct io_mapping based helper.  Selected by drivers that need them
config IO_MAPPING
        bool

config MEMFD_CREATE
        bool "Enable memfd_create() system call" if EXPERT

config SECRETMEM
        default y
        bool "Enable memfd_secret() system call" if EXPERT
        depends on ARCH_HAS_SET_DIRECT_MAP
        help
          Enable the memfd_secret() system call with the ability to create
          memory areas visible only in the context of the owning process and
          not mapped to other processes and other kernel page tables.

config ANON_VMA_NAME
        bool "Anonymous VMA name support"
        depends on PROC_FS && ADVISE_SYSCALLS && MMU

        help
          Allow naming anonymous virtual memory areas.

          This feature allows assigning names to virtual memory areas. Assigned
          names can be later retrieved from /proc/pid/maps and /proc/pid/smaps
          and help identifying individual anonymous memory areas.
          Assigning a name to anonymous virtual memory area might prevent that
          area from being merged with adjacent virtual memory areas due to the
          difference in their name.

config HAVE_ARCH_USERFAULTFD_WP
        bool
        help
          Arch has userfaultfd write protection support

config HAVE_ARCH_USERFAULTFD_MINOR
        bool
        help
          Arch has userfaultfd minor fault support

menuconfig USERFAULTFD
        bool "Enable userfaultfd() system call"
        depends on MMU
        help
          Enable the userfaultfd() system call that allows to intercept and
          handle page faults in userland.

if USERFAULTFD
config PTE_MARKER_UFFD_WP
        bool "Userfaultfd write protection support for shmem/hugetlbfs"
        default y
        depends on HAVE_ARCH_USERFAULTFD_WP

        help
          Allows to create marker PTEs for userfaultfd write protection
          purposes.  It is required to enable userfaultfd write protection on
          file-backed memory types like shmem and hugetlbfs.
endif # USERFAULTFD

# multi-gen LRU {
config LRU_GEN
        bool "Multi-Gen LRU"
        depends on MMU
        # make sure folio->flags has enough spare bits
        depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP
        help
          A high performance LRU implementation to overcommit memory. See
          Documentation/admin-guide/mm/multigen_lru.rst for details.

config LRU_GEN_ENABLED
        bool "Enable by default"
        depends on LRU_GEN
        help
          This option enables the multi-gen LRU by default.

config LRU_GEN_STATS
        bool "Full stats for debugging"
        depends on LRU_GEN
        help
          Do not enable this option unless you plan to look at historical stats
          from evicted generations for debugging purpose.

          This option has a per-memcg and per-node memory overhead.

config LRU_GEN_WALKS_MMU
        def_bool y
        depends on LRU_GEN && ARCH_HAS_HW_PTE_YOUNG
# }

config ARCH_SUPPORTS_PER_VMA_LOCK
       def_bool n

config PER_VMA_LOCK
        def_bool y
        depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP
        help
          Allow per-vma locking during page fault handling.

          This feature allows locking each virtual memory area separately when
          handling page faults instead of taking mmap_lock.

config LOCK_MM_AND_FIND_VMA
        bool
        depends on !STACK_GROWSUP

config IOMMU_MM_DATA
        bool

config EXECMEM
        bool

config NUMA_MEMBLKS
        bool

config NUMA_EMU
        bool "NUMA emulation"
        depends on NUMA_MEMBLKS
        help
          Enable NUMA emulation. A flat machine will be split
          into virtual nodes when booted with "numa=fake=N", where N is the
          number of nodes. This is only useful for debugging.

config ARCH_HAS_USER_SHADOW_STACK
        bool
        help
          The architecture has hardware support for userspace shadow call
          stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss).

source "mm/damon/Kconfig"

endmenu