1 # SPDX-License-Identifier: GPL-2.0-only
3 menu "Memory Management options"
5 config SELECT_MEMORY_MODEL
7 depends on ARCH_SELECT_MEMORY_MODEL
11 depends on SELECT_MEMORY_MODEL
12 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
13 default FLATMEM_MANUAL
15 This option allows you to change some of the ways that
16 Linux manages its memory internally. Most users will
17 only have one option here selected by the architecture
18 configuration. This is normal.
22 depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
24 This option is best suited for non-NUMA systems with
25 flat address space. The FLATMEM is the most efficient
26 system in terms of performance and resource consumption
27 and it is the best option for smaller systems.
29 For systems that have holes in their physical address
30 spaces and for features like NUMA and memory hotplug,
31 choose "Sparse Memory".
33 If unsure, choose this option (Flat Memory) over any other.
35 config DISCONTIGMEM_MANUAL
36 bool "Discontiguous Memory"
37 depends on ARCH_DISCONTIGMEM_ENABLE
39 This option provides enhanced support for discontiguous
40 memory systems, over FLATMEM. These systems have holes
41 in their physical address spaces, and this option provides
42 more efficient handling of these holes.
44 Although "Discontiguous Memory" is still used by several
45 architectures, it is considered deprecated in favor of
48 If unsure, choose "Sparse Memory" over this option.
50 config SPARSEMEM_MANUAL
52 depends on ARCH_SPARSEMEM_ENABLE
54 This will be the only option for some systems, including
55 memory hot-plug systems. This is normal.
57 This option provides efficient support for systems with
58 holes is their physical address space and allows memory
59 hot-plug and hot-remove.
61 If unsure, choose "Flat Memory" over this option.
67 depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
71 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
75 depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
77 config FLAT_NODE_MEM_MAP
82 # Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
83 # to represent different areas of memory. This variable allows
84 # those dependencies to exist individually.
86 config NEED_MULTIPLE_NODES
88 depends on DISCONTIGMEM || NUMA
91 # SPARSEMEM_EXTREME (which is the default) does some bootmem
92 # allocations when sparse_init() is called. If this cannot
93 # be done on your architecture, select this option. However,
94 # statically allocating the mem_section[] array can potentially
95 # consume vast quantities of .bss, so be careful.
97 # This option will also potentially produce smaller runtime code
98 # with gcc 3.4 and later.
100 config SPARSEMEM_STATIC
104 # Architecture platforms which require a two level mem_section in SPARSEMEM
105 # must select this option. This is usually for architecture platforms with
106 # an extremely sparse physical address space.
108 config SPARSEMEM_EXTREME
110 depends on SPARSEMEM && !SPARSEMEM_STATIC
112 config SPARSEMEM_VMEMMAP_ENABLE
115 config SPARSEMEM_VMEMMAP
116 bool "Sparse Memory virtual memmap"
117 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
120 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
121 pfn_to_page and page_to_pfn operations. This is the most
122 efficient option when sufficient kernel resources are available.
124 config HAVE_MEMBLOCK_PHYS_MAP
131 # Don't discard allocated memory used to track "memory" and "reserved" memblocks
132 # after early boot, so it can still be used to test for validity of memory.
133 # Also, memblocks are updated with memory hot(un)plug.
134 config ARCH_KEEP_MEMBLOCK
137 # Keep arch NUMA mapping infrastructure post-init.
138 config NUMA_KEEP_MEMINFO
141 config MEMORY_ISOLATION
145 # Only be set on architectures that have completely implemented memory hotplug
146 # feature. If you are not sure, don't touch it.
148 config HAVE_BOOTMEM_INFO_NODE
151 config ARCH_ENABLE_MEMORY_HOTPLUG
154 # eventually, we can have this option just 'select SPARSEMEM'
155 config MEMORY_HOTPLUG
156 bool "Allow for memory hot-add"
157 select MEMORY_ISOLATION
158 depends on SPARSEMEM || X86_64_ACPI_NUMA
159 depends on ARCH_ENABLE_MEMORY_HOTPLUG
160 depends on 64BIT || BROKEN
161 select NUMA_KEEP_MEMINFO if NUMA
163 config MEMORY_HOTPLUG_SPARSE
165 depends on SPARSEMEM && MEMORY_HOTPLUG
167 config MEMORY_HOTPLUG_DEFAULT_ONLINE
168 bool "Online the newly added memory blocks by default"
169 depends on MEMORY_HOTPLUG
171 This option sets the default policy setting for memory hotplug
172 onlining policy (/sys/devices/system/memory/auto_online_blocks) which
173 determines what happens to newly added memory regions. Policy setting
174 can always be changed at runtime.
175 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
177 Say Y here if you want all hot-plugged memory blocks to appear in
178 'online' state by default.
179 Say N here if you want the default policy to keep all hot-plugged
180 memory blocks in 'offline' state.
182 config ARCH_ENABLE_MEMORY_HOTREMOVE
185 config MEMORY_HOTREMOVE
186 bool "Allow for memory hot remove"
187 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
188 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
191 # Heavily threaded applications may benefit from splitting the mm-wide
192 # page_table_lock, so that faults on different parts of the user address
193 # space can be handled with less contention: split it at this NR_CPUS.
194 # Default to 4 for wider testing, though 8 might be more appropriate.
195 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
196 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
197 # SPARC32 allocates multiple pte tables within a single page, and therefore
198 # a per-page lock leads to problems when multiple tables need to be locked
199 # at the same time (e.g. copy_page_range()).
200 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
202 config SPLIT_PTLOCK_CPUS
204 default "999999" if !MMU
205 default "999999" if ARM && !CPU_CACHE_VIPT
206 default "999999" if PARISC && !PA20
207 default "999999" if SPARC32
210 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
214 # support for memory balloon
215 config MEMORY_BALLOON
219 # support for memory balloon compaction
220 config BALLOON_COMPACTION
221 bool "Allow for balloon memory compaction/migration"
223 depends on COMPACTION && MEMORY_BALLOON
225 Memory fragmentation introduced by ballooning might reduce
226 significantly the number of 2MB contiguous memory blocks that can be
227 used within a guest, thus imposing performance penalties associated
228 with the reduced number of transparent huge pages that could be used
229 by the guest workload. Allowing the compaction & migration for memory
230 pages enlisted as being part of memory balloon devices avoids the
231 scenario aforementioned and helps improving memory defragmentation.
234 # support for memory compaction
236 bool "Allow for memory compaction"
241 Compaction is the only memory management component to form
242 high order (larger physically contiguous) memory blocks
243 reliably. The page allocator relies on compaction heavily and
244 the lack of the feature can lead to unexpected OOM killer
245 invocations for high order memory requests. You shouldn't
246 disable this option unless there really is a strong reason for
247 it and then we would be really interested to hear about that at
251 # support for free page reporting
252 config PAGE_REPORTING
253 bool "Free page reporting"
256 Free page reporting allows for the incremental acquisition of
257 free pages from the buddy allocator for the purpose of reporting
258 those pages to another entity, such as a hypervisor, so that the
259 memory can be freed within the host for other uses.
262 # support for page migration
265 bool "Page migration"
267 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
269 Allows the migration of the physical location of pages of processes
270 while the virtual addresses are not changed. This is useful in
271 two situations. The first is on NUMA systems to put pages nearer
272 to the processors accessing. The second is when allocating huge
273 pages as migration can relocate pages to satisfy a huge page
274 allocation instead of reclaiming.
276 config ARCH_ENABLE_HUGEPAGE_MIGRATION
279 config ARCH_ENABLE_THP_MIGRATION
282 config HUGETLB_PAGE_SIZE_VARIABLE
285 Allows the pageblock_order value to be dynamic instead of just standard
286 HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available
290 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
292 config PHYS_ADDR_T_64BIT
296 bool "Enable bounce buffers"
298 depends on BLOCK && MMU && HIGHMEM
300 Enable bounce buffers for devices that cannot access the full range of
301 memory available to the CPU. Enabled by default when HIGHMEM is
302 selected, but you may say n to override this.
307 An architecture should select this if it implements the
308 deprecated interface virt_to_bus(). All new architectures
309 should probably not select this.
318 bool "Enable KSM for page merging"
322 Enable Kernel Samepage Merging: KSM periodically scans those areas
323 of an application's address space that an app has advised may be
324 mergeable. When it finds pages of identical content, it replaces
325 the many instances by a single page with that content, so
326 saving memory until one or another app needs to modify the content.
327 Recommended for use with KVM, or with other duplicative applications.
328 See Documentation/vm/ksm.rst for more information: KSM is inactive
329 until a program has madvised that an area is MADV_MERGEABLE, and
330 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
332 config DEFAULT_MMAP_MIN_ADDR
333 int "Low address space to protect from user allocation"
337 This is the portion of low virtual memory which should be protected
338 from userspace allocation. Keeping a user from writing to low pages
339 can help reduce the impact of kernel NULL pointer bugs.
341 For most ia64, ppc64 and x86 users with lots of address space
342 a value of 65536 is reasonable and should cause no problems.
343 On arm and other archs it should not be higher than 32768.
344 Programs which use vm86 functionality or have some need to map
345 this low address space will need CAP_SYS_RAWIO or disable this
346 protection by setting the value to 0.
348 This value can be changed after boot using the
349 /proc/sys/vm/mmap_min_addr tunable.
351 config ARCH_SUPPORTS_MEMORY_FAILURE
354 config MEMORY_FAILURE
356 depends on ARCH_SUPPORTS_MEMORY_FAILURE
357 bool "Enable recovery from hardware memory errors"
358 select MEMORY_ISOLATION
361 Enables code to recover from some memory failures on systems
362 with MCA recovery. This allows a system to continue running
363 even when some of its memory has uncorrected errors. This requires
364 special hardware support and typically ECC memory.
366 config HWPOISON_INJECT
367 tristate "HWPoison pages injector"
368 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
369 select PROC_PAGE_MONITOR
371 config NOMMU_INITIAL_TRIM_EXCESS
372 int "Turn on mmap() excess space trimming before booting"
376 The NOMMU mmap() frequently needs to allocate large contiguous chunks
377 of memory on which to store mappings, but it can only ask the system
378 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
379 more than it requires. To deal with this, mmap() is able to trim off
380 the excess and return it to the allocator.
382 If trimming is enabled, the excess is trimmed off and returned to the
383 system allocator, which can cause extra fragmentation, particularly
384 if there are a lot of transient processes.
386 If trimming is disabled, the excess is kept, but not used, which for
387 long-term mappings means that the space is wasted.
389 Trimming can be dynamically controlled through a sysctl option
390 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
391 excess pages there must be before trimming should occur, or zero if
392 no trimming is to occur.
394 This option specifies the initial value of this option. The default
395 of 1 says that all excess pages should be trimmed.
397 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
399 config TRANSPARENT_HUGEPAGE
400 bool "Transparent Hugepage Support"
401 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
405 Transparent Hugepages allows the kernel to use huge pages and
406 huge tlb transparently to the applications whenever possible.
407 This feature can improve computing performance to certain
408 applications by speeding up page faults during memory
409 allocation, by reducing the number of tlb misses and by speeding
410 up the pagetable walking.
412 If memory constrained on embedded, you may want to say N.
415 prompt "Transparent Hugepage Support sysfs defaults"
416 depends on TRANSPARENT_HUGEPAGE
417 default TRANSPARENT_HUGEPAGE_ALWAYS
419 Selects the sysfs defaults for Transparent Hugepage Support.
421 config TRANSPARENT_HUGEPAGE_ALWAYS
424 Enabling Transparent Hugepage always, can increase the
425 memory footprint of applications without a guaranteed
426 benefit but it will work automatically for all applications.
428 config TRANSPARENT_HUGEPAGE_MADVISE
431 Enabling Transparent Hugepage madvise, will only provide a
432 performance improvement benefit to the applications using
433 madvise(MADV_HUGEPAGE) but it won't risk to increase the
434 memory footprint of applications without a guaranteed
438 config ARCH_WANTS_THP_SWAP
443 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
445 Swap transparent huge pages in one piece, without splitting.
446 XXX: For now, swap cluster backing transparent huge page
447 will be split after swapout.
449 For selection by architectures with reasonable THP sizes.
452 # UP and nommu archs use km based percpu allocator
454 config NEED_PER_CPU_KM
460 bool "Enable cleancache driver to cache clean pages if tmem is present"
462 Cleancache can be thought of as a page-granularity victim cache
463 for clean pages that the kernel's pageframe replacement algorithm
464 (PFRA) would like to keep around, but can't since there isn't enough
465 memory. So when the PFRA "evicts" a page, it first attempts to use
466 cleancache code to put the data contained in that page into
467 "transcendent memory", memory that is not directly accessible or
468 addressable by the kernel and is of unknown and possibly
469 time-varying size. And when a cleancache-enabled
470 filesystem wishes to access a page in a file on disk, it first
471 checks cleancache to see if it already contains it; if it does,
472 the page is copied into the kernel and a disk access is avoided.
473 When a transcendent memory driver is available (such as zcache or
474 Xen transcendent memory), a significant I/O reduction
475 may be achieved. When none is available, all cleancache calls
476 are reduced to a single pointer-compare-against-NULL resulting
477 in a negligible performance hit.
479 If unsure, say Y to enable cleancache
482 bool "Enable frontswap to cache swap pages if tmem is present"
485 Frontswap is so named because it can be thought of as the opposite
486 of a "backing" store for a swap device. The data is stored into
487 "transcendent memory", memory that is not directly accessible or
488 addressable by the kernel and is of unknown and possibly
489 time-varying size. When space in transcendent memory is available,
490 a significant swap I/O reduction may be achieved. When none is
491 available, all frontswap calls are reduced to a single pointer-
492 compare-against-NULL resulting in a negligible performance hit
493 and swap data is stored as normal on the matching swap device.
495 If unsure, say Y to enable frontswap.
498 bool "Contiguous Memory Allocator"
501 select MEMORY_ISOLATION
503 This enables the Contiguous Memory Allocator which allows other
504 subsystems to allocate big physically-contiguous blocks of memory.
505 CMA reserves a region of memory and allows only movable pages to
506 be allocated from it. This way, the kernel can use the memory for
507 pagecache and when a subsystem requests for contiguous area, the
508 allocated pages are migrated away to serve the contiguous request.
513 bool "CMA debug messages (DEVELOPMENT)"
514 depends on DEBUG_KERNEL && CMA
516 Turns on debug messages in CMA. This produces KERN_DEBUG
517 messages for every CMA call as well as various messages while
518 processing calls such as dma_alloc_from_contiguous().
519 This option does not affect warning and error messages.
522 bool "CMA debugfs interface"
523 depends on CMA && DEBUG_FS
525 Turns on the DebugFS interface for CMA.
528 bool "CMA information through sysfs interface"
529 depends on CMA && SYSFS
531 This option exposes some sysfs attributes to get information
535 int "Maximum count of the CMA areas"
540 CMA allows to create CMA areas for particular purpose, mainly,
541 used as device private area. This parameter sets the maximum
542 number of CMA area in the system.
544 If unsure, leave the default value "7" in UMA and "19" in NUMA.
546 config MEM_SOFT_DIRTY
547 bool "Track memory changes"
548 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
549 select PROC_PAGE_MONITOR
551 This option enables memory changes tracking by introducing a
552 soft-dirty bit on pte-s. This bit it set when someone writes
553 into a page just as regular dirty bit, but unlike the latter
554 it can be cleared by hands.
556 See Documentation/admin-guide/mm/soft-dirty.rst for more details.
559 bool "Compressed cache for swap pages (EXPERIMENTAL)"
560 depends on FRONTSWAP && CRYPTO=y
563 A lightweight compressed cache for swap pages. It takes
564 pages that are in the process of being swapped out and attempts to
565 compress them into a dynamically allocated RAM-based memory pool.
566 This can result in a significant I/O reduction on swap device and,
567 in the case where decompressing from RAM is faster that swap device
568 reads, can also improve workload performance.
570 This is marked experimental because it is a new feature (as of
571 v3.11) that interacts heavily with memory reclaim. While these
572 interactions don't cause any known issues on simple memory setups,
573 they have not be fully explored on the large set of potential
574 configurations and workloads that exist.
577 prompt "Compressed cache for swap pages default compressor"
579 default ZSWAP_COMPRESSOR_DEFAULT_LZO
581 Selects the default compression algorithm for the compressed cache
584 For an overview what kind of performance can be expected from
585 a particular compression algorithm please refer to the benchmarks
586 available at the following LWN page:
587 https://lwn.net/Articles/751795/
589 If in doubt, select 'LZO'.
591 The selection made here can be overridden by using the kernel
592 command line 'zswap.compressor=' option.
594 config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
596 select CRYPTO_DEFLATE
598 Use the Deflate algorithm as the default compression algorithm.
600 config ZSWAP_COMPRESSOR_DEFAULT_LZO
604 Use the LZO algorithm as the default compression algorithm.
606 config ZSWAP_COMPRESSOR_DEFAULT_842
610 Use the 842 algorithm as the default compression algorithm.
612 config ZSWAP_COMPRESSOR_DEFAULT_LZ4
616 Use the LZ4 algorithm as the default compression algorithm.
618 config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
622 Use the LZ4HC algorithm as the default compression algorithm.
624 config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
628 Use the zstd algorithm as the default compression algorithm.
631 config ZSWAP_COMPRESSOR_DEFAULT
634 default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
635 default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
636 default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
637 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
638 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
639 default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
643 prompt "Compressed cache for swap pages default allocator"
645 default ZSWAP_ZPOOL_DEFAULT_ZBUD
647 Selects the default allocator for the compressed cache for
649 The default is 'zbud' for compatibility, however please do
650 read the description of each of the allocators below before
651 making a right choice.
653 The selection made here can be overridden by using the kernel
654 command line 'zswap.zpool=' option.
656 config ZSWAP_ZPOOL_DEFAULT_ZBUD
660 Use the zbud allocator as the default allocator.
662 config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
666 Use the z3fold allocator as the default allocator.
668 config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
672 Use the zsmalloc allocator as the default allocator.
675 config ZSWAP_ZPOOL_DEFAULT
678 default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
679 default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
680 default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
683 config ZSWAP_DEFAULT_ON
684 bool "Enable the compressed cache for swap pages by default"
687 If selected, the compressed cache for swap pages will be enabled
688 at boot, otherwise it will be disabled.
690 The selection made here can be overridden by using the kernel
691 command line 'zswap.enabled=' option.
694 tristate "Common API for compressed memory storage"
696 Compressed memory storage API. This allows using either zbud or
700 tristate "Low (Up to 2x) density storage for compressed pages"
702 A special purpose allocator for storing compressed pages.
703 It is designed to store up to two compressed pages per physical
704 page. While this design limits storage density, it has simple and
705 deterministic reclaim properties that make it preferable to a higher
706 density approach when reclaim will be used.
709 tristate "Up to 3x density storage for compressed pages"
712 A special purpose allocator for storing compressed pages.
713 It is designed to store up to three compressed pages per physical
714 page. It is a ZBUD derivative so the simplicity and determinism are
718 tristate "Memory allocator for compressed pages"
721 zsmalloc is a slab-based memory allocator designed to store
722 compressed RAM pages. zsmalloc uses virtual memory mapping
723 in order to reduce fragmentation. However, this results in a
724 non-standard allocator interface where a handle, not a pointer, is
725 returned by an alloc(). This handle must be mapped in order to
726 access the allocated space.
729 bool "Export zsmalloc statistics"
733 This option enables code in the zsmalloc to collect various
734 statistics about what's happening in zsmalloc and exports that
735 information to userspace via debugfs.
738 config GENERIC_EARLY_IOREMAP
741 config STACK_MAX_DEFAULT_SIZE_MB
742 int "Default maximum user stack size for 32-bit processes (MB)"
745 depends on STACK_GROWSUP && (!64BIT || COMPAT)
747 This is the maximum stack size in Megabytes in the VM layout of 32-bit
748 user processes when the stack grows upwards (currently only on parisc
749 arch) when the RLIMIT_STACK hard limit is unlimited.
751 A sane initial value is 100 MB.
753 config DEFERRED_STRUCT_PAGE_INIT
754 bool "Defer initialisation of struct pages to kthreads"
756 depends on !NEED_PER_CPU_KM
760 Ordinarily all struct pages are initialised during early boot in a
761 single thread. On very large machines this can take a considerable
762 amount of time. If this option is set, large machines will bring up
763 a subset of memmap at boot and then initialise the rest in parallel.
764 This has a potential performance impact on tasks running early in the
765 lifetime of the system until these kthreads finish the
768 config IDLE_PAGE_TRACKING
769 bool "Enable idle page tracking"
770 depends on SYSFS && MMU
771 select PAGE_EXTENSION if !64BIT
773 This feature allows to estimate the amount of user pages that have
774 not been touched during a given period of time. This information can
775 be useful to tune memory cgroup limits and/or for job placement
776 within a compute cluster.
778 See Documentation/admin-guide/mm/idle_page_tracking.rst for
781 config ARCH_HAS_CACHE_LINE_SIZE
784 config ARCH_HAS_PTE_DEVMAP
788 bool "Device memory (pmem, HMM, etc...) hotplug support"
789 depends on MEMORY_HOTPLUG
790 depends on MEMORY_HOTREMOVE
791 depends on SPARSEMEM_VMEMMAP
792 depends on ARCH_HAS_PTE_DEVMAP
796 Device memory hotplug support allows for establishing pmem,
797 or other device driver discovered memory regions, in the
798 memmap. This allows pfn_to_page() lookups of otherwise
799 "device-physical" addresses which is needed for using a DAX
800 mapping in an O_DIRECT operation, among other things.
802 If FS_DAX is enabled, then say Y.
804 config DEV_PAGEMAP_OPS
808 # Helpers to mirror range of the CPU page tables of a process into device page
815 config DEVICE_PRIVATE
816 bool "Unaddressable device memory (GPU memory, ...)"
817 depends on ZONE_DEVICE
818 select DEV_PAGEMAP_OPS
821 Allows creation of struct pages to represent unaddressable device
822 memory; i.e., memory that is only accessible from the device (or
823 group of devices). You likely also want to select HMM_MIRROR.
828 config ARCH_USES_HIGH_VMA_FLAGS
830 config ARCH_HAS_PKEYS
834 bool "Collect percpu memory statistics"
836 This feature collects and exposes statistics via debugfs. The
837 information includes global and per chunk statistics, which can
838 be used to help understand percpu memory usage.
841 bool "Enable infrastructure for get_user_pages()-related unit tests"
844 Provides /sys/kernel/debug/gup_test, which in turn provides a way
845 to make ioctl calls that can launch kernel-based unit tests for
846 the get_user_pages*() and pin_user_pages*() family of API calls.
848 These tests include benchmark testing of the _fast variants of
849 get_user_pages*() and pin_user_pages*(), as well as smoke tests of
850 the non-_fast variants.
852 There is also a sub-test that allows running dump_page() on any
853 of up to eight pages (selected by command line args) within the
854 range of user-space addresses. These pages are either pinned via
855 pin_user_pages*(), or pinned via get_user_pages*(), as specified
856 by other command line arguments.
858 See tools/testing/selftests/vm/gup_test.c
860 comment "GUP_TEST needs to have DEBUG_FS enabled"
861 depends on !GUP_TEST && !DEBUG_FS
863 config GUP_GET_PTE_LOW_HIGH
866 config READ_ONLY_THP_FOR_FS
867 bool "Read-only THP for filesystems (EXPERIMENTAL)"
868 depends on TRANSPARENT_HUGEPAGE && SHMEM
871 Allow khugepaged to put read-only file-backed pages in THP.
873 This is marked experimental because it is a new feature. Write
874 support of file THPs will be developed in the next few release
877 config ARCH_HAS_PTE_SPECIAL
881 # Some architectures require a special hugepage directory format that is
882 # required to support multiple hugepage sizes. For example a4fe3ce76
883 # "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
884 # introduced it on powerpc. This allows for a more flexible hugepage
887 config ARCH_HAS_HUGEPD
890 config MAPPING_DIRTY_HELPERS
896 # struct io_mapping based helper. Selected by drivers that need them