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_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 SPARSEMEM_MANUAL
37 depends on ARCH_SPARSEMEM_ENABLE
39 This will be the only option for some systems, including
40 memory hot-plug systems. This is normal.
42 This option provides efficient support for systems with
43 holes is their physical address space and allows memory
44 hot-plug and hot-remove.
46 If unsure, choose "Flat Memory" over this option.
52 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
56 depends on !SPARSEMEM || FLATMEM_MANUAL
58 config FLAT_NODE_MEM_MAP
63 # SPARSEMEM_EXTREME (which is the default) does some bootmem
64 # allocations when sparse_init() is called. If this cannot
65 # be done on your architecture, select this option. However,
66 # statically allocating the mem_section[] array can potentially
67 # consume vast quantities of .bss, so be careful.
69 # This option will also potentially produce smaller runtime code
70 # with gcc 3.4 and later.
72 config SPARSEMEM_STATIC
76 # Architecture platforms which require a two level mem_section in SPARSEMEM
77 # must select this option. This is usually for architecture platforms with
78 # an extremely sparse physical address space.
80 config SPARSEMEM_EXTREME
82 depends on SPARSEMEM && !SPARSEMEM_STATIC
84 config SPARSEMEM_VMEMMAP_ENABLE
87 config SPARSEMEM_VMEMMAP
88 bool "Sparse Memory virtual memmap"
89 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
92 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
93 pfn_to_page and page_to_pfn operations. This is the most
94 efficient option when sufficient kernel resources are available.
96 config HAVE_MEMBLOCK_PHYS_MAP
103 # Don't discard allocated memory used to track "memory" and "reserved" memblocks
104 # after early boot, so it can still be used to test for validity of memory.
105 # Also, memblocks are updated with memory hot(un)plug.
106 config ARCH_KEEP_MEMBLOCK
109 # Keep arch NUMA mapping infrastructure post-init.
110 config NUMA_KEEP_MEMINFO
113 config MEMORY_ISOLATION
117 # Only be set on architectures that have completely implemented memory hotplug
118 # feature. If you are not sure, don't touch it.
120 config HAVE_BOOTMEM_INFO_NODE
123 config ARCH_ENABLE_MEMORY_HOTPLUG
126 # eventually, we can have this option just 'select SPARSEMEM'
127 config MEMORY_HOTPLUG
128 bool "Allow for memory hot-add"
129 select MEMORY_ISOLATION
130 depends on SPARSEMEM || X86_64_ACPI_NUMA
131 depends on ARCH_ENABLE_MEMORY_HOTPLUG
132 depends on 64BIT || BROKEN
133 select NUMA_KEEP_MEMINFO if NUMA
135 config MEMORY_HOTPLUG_SPARSE
137 depends on SPARSEMEM && MEMORY_HOTPLUG
139 config MEMORY_HOTPLUG_DEFAULT_ONLINE
140 bool "Online the newly added memory blocks by default"
141 depends on MEMORY_HOTPLUG
143 This option sets the default policy setting for memory hotplug
144 onlining policy (/sys/devices/system/memory/auto_online_blocks) which
145 determines what happens to newly added memory regions. Policy setting
146 can always be changed at runtime.
147 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
149 Say Y here if you want all hot-plugged memory blocks to appear in
150 'online' state by default.
151 Say N here if you want the default policy to keep all hot-plugged
152 memory blocks in 'offline' state.
154 config ARCH_ENABLE_MEMORY_HOTREMOVE
157 config MEMORY_HOTREMOVE
158 bool "Allow for memory hot remove"
159 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
160 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
163 config MHP_MEMMAP_ON_MEMORY
165 depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
166 depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
168 # Heavily threaded applications may benefit from splitting the mm-wide
169 # page_table_lock, so that faults on different parts of the user address
170 # space can be handled with less contention: split it at this NR_CPUS.
171 # Default to 4 for wider testing, though 8 might be more appropriate.
172 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
173 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
174 # SPARC32 allocates multiple pte tables within a single page, and therefore
175 # a per-page lock leads to problems when multiple tables need to be locked
176 # at the same time (e.g. copy_page_range()).
177 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
179 config SPLIT_PTLOCK_CPUS
181 default "999999" if !MMU
182 default "999999" if ARM && !CPU_CACHE_VIPT
183 default "999999" if PARISC && !PA20
184 default "999999" if SPARC32
187 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
191 # support for memory balloon
192 config MEMORY_BALLOON
196 # support for memory balloon compaction
197 config BALLOON_COMPACTION
198 bool "Allow for balloon memory compaction/migration"
200 depends on COMPACTION && MEMORY_BALLOON
202 Memory fragmentation introduced by ballooning might reduce
203 significantly the number of 2MB contiguous memory blocks that can be
204 used within a guest, thus imposing performance penalties associated
205 with the reduced number of transparent huge pages that could be used
206 by the guest workload. Allowing the compaction & migration for memory
207 pages enlisted as being part of memory balloon devices avoids the
208 scenario aforementioned and helps improving memory defragmentation.
211 # support for memory compaction
213 bool "Allow for memory compaction"
218 Compaction is the only memory management component to form
219 high order (larger physically contiguous) memory blocks
220 reliably. The page allocator relies on compaction heavily and
221 the lack of the feature can lead to unexpected OOM killer
222 invocations for high order memory requests. You shouldn't
223 disable this option unless there really is a strong reason for
224 it and then we would be really interested to hear about that at
228 # support for free page reporting
229 config PAGE_REPORTING
230 bool "Free page reporting"
233 Free page reporting allows for the incremental acquisition of
234 free pages from the buddy allocator for the purpose of reporting
235 those pages to another entity, such as a hypervisor, so that the
236 memory can be freed within the host for other uses.
239 # support for page migration
242 bool "Page migration"
244 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
246 Allows the migration of the physical location of pages of processes
247 while the virtual addresses are not changed. This is useful in
248 two situations. The first is on NUMA systems to put pages nearer
249 to the processors accessing. The second is when allocating huge
250 pages as migration can relocate pages to satisfy a huge page
251 allocation instead of reclaiming.
253 config ARCH_ENABLE_HUGEPAGE_MIGRATION
256 config ARCH_ENABLE_THP_MIGRATION
259 config HUGETLB_PAGE_SIZE_VARIABLE
262 Allows the pageblock_order value to be dynamic instead of just standard
263 HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available
267 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
269 config PHYS_ADDR_T_64BIT
273 bool "Enable bounce buffers"
275 depends on BLOCK && MMU && HIGHMEM
277 Enable bounce buffers for devices that cannot access the full range of
278 memory available to the CPU. Enabled by default when HIGHMEM is
279 selected, but you may say n to override this.
284 An architecture should select this if it implements the
285 deprecated interface virt_to_bus(). All new architectures
286 should probably not select this.
295 bool "Enable KSM for page merging"
299 Enable Kernel Samepage Merging: KSM periodically scans those areas
300 of an application's address space that an app has advised may be
301 mergeable. When it finds pages of identical content, it replaces
302 the many instances by a single page with that content, so
303 saving memory until one or another app needs to modify the content.
304 Recommended for use with KVM, or with other duplicative applications.
305 See Documentation/vm/ksm.rst for more information: KSM is inactive
306 until a program has madvised that an area is MADV_MERGEABLE, and
307 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
309 config DEFAULT_MMAP_MIN_ADDR
310 int "Low address space to protect from user allocation"
314 This is the portion of low virtual memory which should be protected
315 from userspace allocation. Keeping a user from writing to low pages
316 can help reduce the impact of kernel NULL pointer bugs.
318 For most ia64, ppc64 and x86 users with lots of address space
319 a value of 65536 is reasonable and should cause no problems.
320 On arm and other archs it should not be higher than 32768.
321 Programs which use vm86 functionality or have some need to map
322 this low address space will need CAP_SYS_RAWIO or disable this
323 protection by setting the value to 0.
325 This value can be changed after boot using the
326 /proc/sys/vm/mmap_min_addr tunable.
328 config ARCH_SUPPORTS_MEMORY_FAILURE
331 config MEMORY_FAILURE
333 depends on ARCH_SUPPORTS_MEMORY_FAILURE
334 bool "Enable recovery from hardware memory errors"
335 select MEMORY_ISOLATION
338 Enables code to recover from some memory failures on systems
339 with MCA recovery. This allows a system to continue running
340 even when some of its memory has uncorrected errors. This requires
341 special hardware support and typically ECC memory.
343 config HWPOISON_INJECT
344 tristate "HWPoison pages injector"
345 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
346 select PROC_PAGE_MONITOR
348 config NOMMU_INITIAL_TRIM_EXCESS
349 int "Turn on mmap() excess space trimming before booting"
353 The NOMMU mmap() frequently needs to allocate large contiguous chunks
354 of memory on which to store mappings, but it can only ask the system
355 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
356 more than it requires. To deal with this, mmap() is able to trim off
357 the excess and return it to the allocator.
359 If trimming is enabled, the excess is trimmed off and returned to the
360 system allocator, which can cause extra fragmentation, particularly
361 if there are a lot of transient processes.
363 If trimming is disabled, the excess is kept, but not used, which for
364 long-term mappings means that the space is wasted.
366 Trimming can be dynamically controlled through a sysctl option
367 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
368 excess pages there must be before trimming should occur, or zero if
369 no trimming is to occur.
371 This option specifies the initial value of this option. The default
372 of 1 says that all excess pages should be trimmed.
374 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
376 config TRANSPARENT_HUGEPAGE
377 bool "Transparent Hugepage Support"
378 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
382 Transparent Hugepages allows the kernel to use huge pages and
383 huge tlb transparently to the applications whenever possible.
384 This feature can improve computing performance to certain
385 applications by speeding up page faults during memory
386 allocation, by reducing the number of tlb misses and by speeding
387 up the pagetable walking.
389 If memory constrained on embedded, you may want to say N.
392 prompt "Transparent Hugepage Support sysfs defaults"
393 depends on TRANSPARENT_HUGEPAGE
394 default TRANSPARENT_HUGEPAGE_ALWAYS
396 Selects the sysfs defaults for Transparent Hugepage Support.
398 config TRANSPARENT_HUGEPAGE_ALWAYS
401 Enabling Transparent Hugepage always, can increase the
402 memory footprint of applications without a guaranteed
403 benefit but it will work automatically for all applications.
405 config TRANSPARENT_HUGEPAGE_MADVISE
408 Enabling Transparent Hugepage madvise, will only provide a
409 performance improvement benefit to the applications using
410 madvise(MADV_HUGEPAGE) but it won't risk to increase the
411 memory footprint of applications without a guaranteed
415 config ARCH_WANTS_THP_SWAP
420 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
422 Swap transparent huge pages in one piece, without splitting.
423 XXX: For now, swap cluster backing transparent huge page
424 will be split after swapout.
426 For selection by architectures with reasonable THP sizes.
429 # UP and nommu archs use km based percpu allocator
431 config NEED_PER_CPU_KM
437 bool "Enable cleancache driver to cache clean pages if tmem is present"
439 Cleancache can be thought of as a page-granularity victim cache
440 for clean pages that the kernel's pageframe replacement algorithm
441 (PFRA) would like to keep around, but can't since there isn't enough
442 memory. So when the PFRA "evicts" a page, it first attempts to use
443 cleancache code to put the data contained in that page into
444 "transcendent memory", memory that is not directly accessible or
445 addressable by the kernel and is of unknown and possibly
446 time-varying size. And when a cleancache-enabled
447 filesystem wishes to access a page in a file on disk, it first
448 checks cleancache to see if it already contains it; if it does,
449 the page is copied into the kernel and a disk access is avoided.
450 When a transcendent memory driver is available (such as zcache or
451 Xen transcendent memory), a significant I/O reduction
452 may be achieved. When none is available, all cleancache calls
453 are reduced to a single pointer-compare-against-NULL resulting
454 in a negligible performance hit.
456 If unsure, say Y to enable cleancache
459 bool "Enable frontswap to cache swap pages if tmem is present"
462 Frontswap is so named because it can be thought of as the opposite
463 of a "backing" store for a swap device. The data is stored into
464 "transcendent memory", memory that is not directly accessible or
465 addressable by the kernel and is of unknown and possibly
466 time-varying size. When space in transcendent memory is available,
467 a significant swap I/O reduction may be achieved. When none is
468 available, all frontswap calls are reduced to a single pointer-
469 compare-against-NULL resulting in a negligible performance hit
470 and swap data is stored as normal on the matching swap device.
472 If unsure, say Y to enable frontswap.
475 bool "Contiguous Memory Allocator"
478 select MEMORY_ISOLATION
480 This enables the Contiguous Memory Allocator which allows other
481 subsystems to allocate big physically-contiguous blocks of memory.
482 CMA reserves a region of memory and allows only movable pages to
483 be allocated from it. This way, the kernel can use the memory for
484 pagecache and when a subsystem requests for contiguous area, the
485 allocated pages are migrated away to serve the contiguous request.
490 bool "CMA debug messages (DEVELOPMENT)"
491 depends on DEBUG_KERNEL && CMA
493 Turns on debug messages in CMA. This produces KERN_DEBUG
494 messages for every CMA call as well as various messages while
495 processing calls such as dma_alloc_from_contiguous().
496 This option does not affect warning and error messages.
499 bool "CMA debugfs interface"
500 depends on CMA && DEBUG_FS
502 Turns on the DebugFS interface for CMA.
505 bool "CMA information through sysfs interface"
506 depends on CMA && SYSFS
508 This option exposes some sysfs attributes to get information
512 int "Maximum count of the CMA areas"
517 CMA allows to create CMA areas for particular purpose, mainly,
518 used as device private area. This parameter sets the maximum
519 number of CMA area in the system.
521 If unsure, leave the default value "7" in UMA and "19" in NUMA.
523 config MEM_SOFT_DIRTY
524 bool "Track memory changes"
525 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
526 select PROC_PAGE_MONITOR
528 This option enables memory changes tracking by introducing a
529 soft-dirty bit on pte-s. This bit it set when someone writes
530 into a page just as regular dirty bit, but unlike the latter
531 it can be cleared by hands.
533 See Documentation/admin-guide/mm/soft-dirty.rst for more details.
536 bool "Compressed cache for swap pages (EXPERIMENTAL)"
537 depends on FRONTSWAP && CRYPTO=y
540 A lightweight compressed cache for swap pages. It takes
541 pages that are in the process of being swapped out and attempts to
542 compress them into a dynamically allocated RAM-based memory pool.
543 This can result in a significant I/O reduction on swap device and,
544 in the case where decompressing from RAM is faster that swap device
545 reads, can also improve workload performance.
547 This is marked experimental because it is a new feature (as of
548 v3.11) that interacts heavily with memory reclaim. While these
549 interactions don't cause any known issues on simple memory setups,
550 they have not be fully explored on the large set of potential
551 configurations and workloads that exist.
554 prompt "Compressed cache for swap pages default compressor"
556 default ZSWAP_COMPRESSOR_DEFAULT_LZO
558 Selects the default compression algorithm for the compressed cache
561 For an overview what kind of performance can be expected from
562 a particular compression algorithm please refer to the benchmarks
563 available at the following LWN page:
564 https://lwn.net/Articles/751795/
566 If in doubt, select 'LZO'.
568 The selection made here can be overridden by using the kernel
569 command line 'zswap.compressor=' option.
571 config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
573 select CRYPTO_DEFLATE
575 Use the Deflate algorithm as the default compression algorithm.
577 config ZSWAP_COMPRESSOR_DEFAULT_LZO
581 Use the LZO algorithm as the default compression algorithm.
583 config ZSWAP_COMPRESSOR_DEFAULT_842
587 Use the 842 algorithm as the default compression algorithm.
589 config ZSWAP_COMPRESSOR_DEFAULT_LZ4
593 Use the LZ4 algorithm as the default compression algorithm.
595 config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
599 Use the LZ4HC algorithm as the default compression algorithm.
601 config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
605 Use the zstd algorithm as the default compression algorithm.
608 config ZSWAP_COMPRESSOR_DEFAULT
611 default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
612 default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
613 default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
614 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
615 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
616 default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
620 prompt "Compressed cache for swap pages default allocator"
622 default ZSWAP_ZPOOL_DEFAULT_ZBUD
624 Selects the default allocator for the compressed cache for
626 The default is 'zbud' for compatibility, however please do
627 read the description of each of the allocators below before
628 making a right choice.
630 The selection made here can be overridden by using the kernel
631 command line 'zswap.zpool=' option.
633 config ZSWAP_ZPOOL_DEFAULT_ZBUD
637 Use the zbud allocator as the default allocator.
639 config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
643 Use the z3fold allocator as the default allocator.
645 config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
649 Use the zsmalloc allocator as the default allocator.
652 config ZSWAP_ZPOOL_DEFAULT
655 default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
656 default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
657 default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
660 config ZSWAP_DEFAULT_ON
661 bool "Enable the compressed cache for swap pages by default"
664 If selected, the compressed cache for swap pages will be enabled
665 at boot, otherwise it will be disabled.
667 The selection made here can be overridden by using the kernel
668 command line 'zswap.enabled=' option.
671 tristate "Common API for compressed memory storage"
673 Compressed memory storage API. This allows using either zbud or
677 tristate "Low (Up to 2x) density storage for compressed pages"
679 A special purpose allocator for storing compressed pages.
680 It is designed to store up to two compressed pages per physical
681 page. While this design limits storage density, it has simple and
682 deterministic reclaim properties that make it preferable to a higher
683 density approach when reclaim will be used.
686 tristate "Up to 3x density storage for compressed pages"
689 A special purpose allocator for storing compressed pages.
690 It is designed to store up to three compressed pages per physical
691 page. It is a ZBUD derivative so the simplicity and determinism are
695 tristate "Memory allocator for compressed pages"
698 zsmalloc is a slab-based memory allocator designed to store
699 compressed RAM pages. zsmalloc uses virtual memory mapping
700 in order to reduce fragmentation. However, this results in a
701 non-standard allocator interface where a handle, not a pointer, is
702 returned by an alloc(). This handle must be mapped in order to
703 access the allocated space.
706 bool "Export zsmalloc statistics"
710 This option enables code in the zsmalloc to collect various
711 statistics about what's happening in zsmalloc and exports that
712 information to userspace via debugfs.
715 config GENERIC_EARLY_IOREMAP
718 config STACK_MAX_DEFAULT_SIZE_MB
719 int "Default maximum user stack size for 32-bit processes (MB)"
722 depends on STACK_GROWSUP && (!64BIT || COMPAT)
724 This is the maximum stack size in Megabytes in the VM layout of 32-bit
725 user processes when the stack grows upwards (currently only on parisc
726 arch) when the RLIMIT_STACK hard limit is unlimited.
728 A sane initial value is 100 MB.
730 config DEFERRED_STRUCT_PAGE_INIT
731 bool "Defer initialisation of struct pages to kthreads"
733 depends on !NEED_PER_CPU_KM
737 Ordinarily all struct pages are initialised during early boot in a
738 single thread. On very large machines this can take a considerable
739 amount of time. If this option is set, large machines will bring up
740 a subset of memmap at boot and then initialise the rest in parallel.
741 This has a potential performance impact on tasks running early in the
742 lifetime of the system until these kthreads finish the
745 config IDLE_PAGE_TRACKING
746 bool "Enable idle page tracking"
747 depends on SYSFS && MMU
748 select PAGE_EXTENSION if !64BIT
750 This feature allows to estimate the amount of user pages that have
751 not been touched during a given period of time. This information can
752 be useful to tune memory cgroup limits and/or for job placement
753 within a compute cluster.
755 See Documentation/admin-guide/mm/idle_page_tracking.rst for
758 config ARCH_HAS_CACHE_LINE_SIZE
761 config ARCH_HAS_PTE_DEVMAP
765 bool "Device memory (pmem, HMM, etc...) hotplug support"
766 depends on MEMORY_HOTPLUG
767 depends on MEMORY_HOTREMOVE
768 depends on SPARSEMEM_VMEMMAP
769 depends on ARCH_HAS_PTE_DEVMAP
773 Device memory hotplug support allows for establishing pmem,
774 or other device driver discovered memory regions, in the
775 memmap. This allows pfn_to_page() lookups of otherwise
776 "device-physical" addresses which is needed for using a DAX
777 mapping in an O_DIRECT operation, among other things.
779 If FS_DAX is enabled, then say Y.
781 config DEV_PAGEMAP_OPS
785 # Helpers to mirror range of the CPU page tables of a process into device page
792 config DEVICE_PRIVATE
793 bool "Unaddressable device memory (GPU memory, ...)"
794 depends on ZONE_DEVICE
795 select DEV_PAGEMAP_OPS
798 Allows creation of struct pages to represent unaddressable device
799 memory; i.e., memory that is only accessible from the device (or
800 group of devices). You likely also want to select HMM_MIRROR.
805 config ARCH_USES_HIGH_VMA_FLAGS
807 config ARCH_HAS_PKEYS
811 bool "Collect percpu memory statistics"
813 This feature collects and exposes statistics via debugfs. The
814 information includes global and per chunk statistics, which can
815 be used to help understand percpu memory usage.
818 bool "Enable infrastructure for get_user_pages()-related unit tests"
821 Provides /sys/kernel/debug/gup_test, which in turn provides a way
822 to make ioctl calls that can launch kernel-based unit tests for
823 the get_user_pages*() and pin_user_pages*() family of API calls.
825 These tests include benchmark testing of the _fast variants of
826 get_user_pages*() and pin_user_pages*(), as well as smoke tests of
827 the non-_fast variants.
829 There is also a sub-test that allows running dump_page() on any
830 of up to eight pages (selected by command line args) within the
831 range of user-space addresses. These pages are either pinned via
832 pin_user_pages*(), or pinned via get_user_pages*(), as specified
833 by other command line arguments.
835 See tools/testing/selftests/vm/gup_test.c
837 comment "GUP_TEST needs to have DEBUG_FS enabled"
838 depends on !GUP_TEST && !DEBUG_FS
840 config GUP_GET_PTE_LOW_HIGH
843 config READ_ONLY_THP_FOR_FS
844 bool "Read-only THP for filesystems (EXPERIMENTAL)"
845 depends on TRANSPARENT_HUGEPAGE && SHMEM
848 Allow khugepaged to put read-only file-backed pages in THP.
850 This is marked experimental because it is a new feature. Write
851 support of file THPs will be developed in the next few release
854 config ARCH_HAS_PTE_SPECIAL
858 # Some architectures require a special hugepage directory format that is
859 # required to support multiple hugepage sizes. For example a4fe3ce76
860 # "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
861 # introduced it on powerpc. This allows for a more flexible hugepage
864 config ARCH_HAS_HUGEPD
867 config MAPPING_DIRTY_HELPERS
873 # struct io_mapping based helper. Selected by drivers that need them