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 DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
13 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
14 default FLATMEM_MANUAL
16 This option allows you to change some of the ways that
17 Linux manages its memory internally. Most users will
18 only have one option here selected by the architecture
19 configuration. This is normal.
23 depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
25 This option is best suited for non-NUMA systems with
26 flat address space. The FLATMEM is the most efficient
27 system in terms of performance and resource consumption
28 and it is the best option for smaller systems.
30 For systems that have holes in their physical address
31 spaces and for features like NUMA and memory hotplug,
32 choose "Sparse Memory".
34 If unsure, choose this option (Flat Memory) over any other.
36 config DISCONTIGMEM_MANUAL
37 bool "Discontiguous Memory"
38 depends on ARCH_DISCONTIGMEM_ENABLE
40 This option provides enhanced support for discontiguous
41 memory systems, over FLATMEM. These systems have holes
42 in their physical address spaces, and this option provides
43 more efficient handling of these holes.
45 Although "Discontiguous Memory" is still used by several
46 architectures, it is considered deprecated in favor of
49 If unsure, choose "Sparse Memory" over this option.
51 config SPARSEMEM_MANUAL
53 depends on ARCH_SPARSEMEM_ENABLE
55 This will be the only option for some systems, including
56 memory hot-plug systems. This is normal.
58 This option provides efficient support for systems with
59 holes is their physical address space and allows memory
60 hot-plug and hot-remove.
62 If unsure, choose "Flat Memory" over this option.
68 depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
72 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
76 depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
78 config FLAT_NODE_MEM_MAP
83 # Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
84 # to represent different areas of memory. This variable allows
85 # those dependencies to exist individually.
87 config NEED_MULTIPLE_NODES
89 depends on DISCONTIGMEM || NUMA
92 # SPARSEMEM_EXTREME (which is the default) does some bootmem
93 # allocations when sparse_init() is called. If this cannot
94 # be done on your architecture, select this option. However,
95 # statically allocating the mem_section[] array can potentially
96 # consume vast quantities of .bss, so be careful.
98 # This option will also potentially produce smaller runtime code
99 # with gcc 3.4 and later.
101 config SPARSEMEM_STATIC
105 # Architecture platforms which require a two level mem_section in SPARSEMEM
106 # must select this option. This is usually for architecture platforms with
107 # an extremely sparse physical address space.
109 config SPARSEMEM_EXTREME
111 depends on SPARSEMEM && !SPARSEMEM_STATIC
113 config SPARSEMEM_VMEMMAP_ENABLE
116 config SPARSEMEM_VMEMMAP
117 bool "Sparse Memory virtual memmap"
118 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
121 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
122 pfn_to_page and page_to_pfn operations. This is the most
123 efficient option when sufficient kernel resources are available.
125 config HAVE_MEMBLOCK_PHYS_MAP
132 # Don't discard allocated memory used to track "memory" and "reserved" memblocks
133 # after early boot, so it can still be used to test for validity of memory.
134 # Also, memblocks are updated with memory hot(un)plug.
135 config ARCH_KEEP_MEMBLOCK
138 # Keep arch NUMA mapping infrastructure post-init.
139 config NUMA_KEEP_MEMINFO
142 config MEMORY_ISOLATION
146 # Only be set on architectures that have completely implemented memory hotplug
147 # feature. If you are not sure, don't touch it.
149 config HAVE_BOOTMEM_INFO_NODE
152 # eventually, we can have this option just 'select SPARSEMEM'
153 config MEMORY_HOTPLUG
154 bool "Allow for memory hot-add"
155 select MEMORY_ISOLATION
156 depends on SPARSEMEM || X86_64_ACPI_NUMA
157 depends on ARCH_ENABLE_MEMORY_HOTPLUG
158 depends on 64BIT || BROKEN
159 select NUMA_KEEP_MEMINFO if NUMA
161 config MEMORY_HOTPLUG_SPARSE
163 depends on SPARSEMEM && MEMORY_HOTPLUG
165 config MEMORY_HOTPLUG_DEFAULT_ONLINE
166 bool "Online the newly added memory blocks by default"
167 depends on MEMORY_HOTPLUG
169 This option sets the default policy setting for memory hotplug
170 onlining policy (/sys/devices/system/memory/auto_online_blocks) which
171 determines what happens to newly added memory regions. Policy setting
172 can always be changed at runtime.
173 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
175 Say Y here if you want all hot-plugged memory blocks to appear in
176 'online' state by default.
177 Say N here if you want the default policy to keep all hot-plugged
178 memory blocks in 'offline' state.
180 config MEMORY_HOTREMOVE
181 bool "Allow for memory hot remove"
182 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
183 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
186 # Heavily threaded applications may benefit from splitting the mm-wide
187 # page_table_lock, so that faults on different parts of the user address
188 # space can be handled with less contention: split it at this NR_CPUS.
189 # Default to 4 for wider testing, though 8 might be more appropriate.
190 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
191 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
192 # SPARC32 allocates multiple pte tables within a single page, and therefore
193 # a per-page lock leads to problems when multiple tables need to be locked
194 # at the same time (e.g. copy_page_range()).
195 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
197 config SPLIT_PTLOCK_CPUS
199 default "999999" if !MMU
200 default "999999" if ARM && !CPU_CACHE_VIPT
201 default "999999" if PARISC && !PA20
202 default "999999" if SPARC32
205 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
209 # support for memory balloon
210 config MEMORY_BALLOON
214 # support for memory balloon compaction
215 config BALLOON_COMPACTION
216 bool "Allow for balloon memory compaction/migration"
218 depends on COMPACTION && MEMORY_BALLOON
220 Memory fragmentation introduced by ballooning might reduce
221 significantly the number of 2MB contiguous memory blocks that can be
222 used within a guest, thus imposing performance penalties associated
223 with the reduced number of transparent huge pages that could be used
224 by the guest workload. Allowing the compaction & migration for memory
225 pages enlisted as being part of memory balloon devices avoids the
226 scenario aforementioned and helps improving memory defragmentation.
229 # support for memory compaction
231 bool "Allow for memory compaction"
236 Compaction is the only memory management component to form
237 high order (larger physically contiguous) memory blocks
238 reliably. The page allocator relies on compaction heavily and
239 the lack of the feature can lead to unexpected OOM killer
240 invocations for high order memory requests. You shouldn't
241 disable this option unless there really is a strong reason for
242 it and then we would be really interested to hear about that at
246 # support for free page reporting
247 config PAGE_REPORTING
248 bool "Free page reporting"
251 Free page reporting allows for the incremental acquisition of
252 free pages from the buddy allocator for the purpose of reporting
253 those pages to another entity, such as a hypervisor, so that the
254 memory can be freed within the host for other uses.
257 # support for page migration
260 bool "Page migration"
262 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
264 Allows the migration of the physical location of pages of processes
265 while the virtual addresses are not changed. This is useful in
266 two situations. The first is on NUMA systems to put pages nearer
267 to the processors accessing. The second is when allocating huge
268 pages as migration can relocate pages to satisfy a huge page
269 allocation instead of reclaiming.
271 config ARCH_ENABLE_HUGEPAGE_MIGRATION
274 config ARCH_ENABLE_THP_MIGRATION
278 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
280 config PHYS_ADDR_T_64BIT
284 bool "Enable bounce buffers"
286 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
288 Enable bounce buffers for devices that cannot access
289 the full range of memory available to the CPU. Enabled
290 by default when ZONE_DMA or HIGHMEM is selected, but you
291 may say n to override this.
296 An architecture should select this if it implements the
297 deprecated interface virt_to_bus(). All new architectures
298 should probably not select this.
307 bool "Enable KSM for page merging"
311 Enable Kernel Samepage Merging: KSM periodically scans those areas
312 of an application's address space that an app has advised may be
313 mergeable. When it finds pages of identical content, it replaces
314 the many instances by a single page with that content, so
315 saving memory until one or another app needs to modify the content.
316 Recommended for use with KVM, or with other duplicative applications.
317 See Documentation/vm/ksm.rst for more information: KSM is inactive
318 until a program has madvised that an area is MADV_MERGEABLE, and
319 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
322 bool "Enable lightweight KSM"
326 LKSM is intended to mitigate energy cost of KSM. LKSM sleeps and
327 waits for incoming events, such as freeze of tasks and user-level
330 Then, LKSM performs one of two memory deduplication strategies, such as
331 partial deduplication and full deduplication.
332 As names of them implying, partial deduplication only scans a subset of
333 processes, thus it provides a lightweight way. Full deduplication scans
334 whole processes joined in the KSM scanning list, thus it is same to
335 original KSM. Due to the level of the incurred event, LKSM performs
336 a proper deduplication strategy.
339 bool "Enable LKSM filtering feature"
342 LKSM_FILTER is intended to reduce necessary scans. LKSM records merged
343 addresses and then used it to filter out unmergeable pages.
344 It improves energy-efficiency at the expense of somewhat sharing chances.
346 config DEFAULT_MMAP_MIN_ADDR
347 int "Low address space to protect from user allocation"
351 This is the portion of low virtual memory which should be protected
352 from userspace allocation. Keeping a user from writing to low pages
353 can help reduce the impact of kernel NULL pointer bugs.
355 For most ia64, ppc64 and x86 users with lots of address space
356 a value of 65536 is reasonable and should cause no problems.
357 On arm and other archs it should not be higher than 32768.
358 Programs which use vm86 functionality or have some need to map
359 this low address space will need CAP_SYS_RAWIO or disable this
360 protection by setting the value to 0.
362 This value can be changed after boot using the
363 /proc/sys/vm/mmap_min_addr tunable.
365 config ARCH_SUPPORTS_MEMORY_FAILURE
368 config MEMORY_FAILURE
370 depends on ARCH_SUPPORTS_MEMORY_FAILURE
371 bool "Enable recovery from hardware memory errors"
372 select MEMORY_ISOLATION
375 Enables code to recover from some memory failures on systems
376 with MCA recovery. This allows a system to continue running
377 even when some of its memory has uncorrected errors. This requires
378 special hardware support and typically ECC memory.
380 config HWPOISON_INJECT
381 tristate "HWPoison pages injector"
382 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
383 select PROC_PAGE_MONITOR
385 config NOMMU_INITIAL_TRIM_EXCESS
386 int "Turn on mmap() excess space trimming before booting"
390 The NOMMU mmap() frequently needs to allocate large contiguous chunks
391 of memory on which to store mappings, but it can only ask the system
392 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
393 more than it requires. To deal with this, mmap() is able to trim off
394 the excess and return it to the allocator.
396 If trimming is enabled, the excess is trimmed off and returned to the
397 system allocator, which can cause extra fragmentation, particularly
398 if there are a lot of transient processes.
400 If trimming is disabled, the excess is kept, but not used, which for
401 long-term mappings means that the space is wasted.
403 Trimming can be dynamically controlled through a sysctl option
404 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
405 excess pages there must be before trimming should occur, or zero if
406 no trimming is to occur.
408 This option specifies the initial value of this option. The default
409 of 1 says that all excess pages should be trimmed.
411 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
413 config TRANSPARENT_HUGEPAGE
414 bool "Transparent Hugepage Support"
415 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT
419 Transparent Hugepages allows the kernel to use huge pages and
420 huge tlb transparently to the applications whenever possible.
421 This feature can improve computing performance to certain
422 applications by speeding up page faults during memory
423 allocation, by reducing the number of tlb misses and by speeding
424 up the pagetable walking.
426 If memory constrained on embedded, you may want to say N.
429 prompt "Transparent Hugepage Support sysfs defaults"
430 depends on TRANSPARENT_HUGEPAGE
431 default TRANSPARENT_HUGEPAGE_ALWAYS
433 Selects the sysfs defaults for Transparent Hugepage Support.
435 config TRANSPARENT_HUGEPAGE_ALWAYS
438 Enabling Transparent Hugepage always, can increase the
439 memory footprint of applications without a guaranteed
440 benefit but it will work automatically for all applications.
442 config TRANSPARENT_HUGEPAGE_MADVISE
445 Enabling Transparent Hugepage madvise, will only provide a
446 performance improvement benefit to the applications using
447 madvise(MADV_HUGEPAGE) but it won't risk to increase the
448 memory footprint of applications without a guaranteed
452 config ARCH_WANTS_THP_SWAP
457 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
459 Swap transparent huge pages in one piece, without splitting.
460 XXX: For now, swap cluster backing transparent huge page
461 will be split after swapout.
463 For selection by architectures with reasonable THP sizes.
466 # UP and nommu archs use km based percpu allocator
468 config NEED_PER_CPU_KM
474 bool "Enable cleancache driver to cache clean pages if tmem is present"
476 Cleancache can be thought of as a page-granularity victim cache
477 for clean pages that the kernel's pageframe replacement algorithm
478 (PFRA) would like to keep around, but can't since there isn't enough
479 memory. So when the PFRA "evicts" a page, it first attempts to use
480 cleancache code to put the data contained in that page into
481 "transcendent memory", memory that is not directly accessible or
482 addressable by the kernel and is of unknown and possibly
483 time-varying size. And when a cleancache-enabled
484 filesystem wishes to access a page in a file on disk, it first
485 checks cleancache to see if it already contains it; if it does,
486 the page is copied into the kernel and a disk access is avoided.
487 When a transcendent memory driver is available (such as zcache or
488 Xen transcendent memory), a significant I/O reduction
489 may be achieved. When none is available, all cleancache calls
490 are reduced to a single pointer-compare-against-NULL resulting
491 in a negligible performance hit.
493 If unsure, say Y to enable cleancache
496 bool "Enable frontswap to cache swap pages if tmem is present"
499 Frontswap is so named because it can be thought of as the opposite
500 of a "backing" store for a swap device. The data is stored into
501 "transcendent memory", memory that is not directly accessible or
502 addressable by the kernel and is of unknown and possibly
503 time-varying size. When space in transcendent memory is available,
504 a significant swap I/O reduction may be achieved. When none is
505 available, all frontswap calls are reduced to a single pointer-
506 compare-against-NULL resulting in a negligible performance hit
507 and swap data is stored as normal on the matching swap device.
509 If unsure, say Y to enable frontswap.
512 bool "Contiguous Memory Allocator"
515 select MEMORY_ISOLATION
517 This enables the Contiguous Memory Allocator which allows other
518 subsystems to allocate big physically-contiguous blocks of memory.
519 CMA reserves a region of memory and allows only movable pages to
520 be allocated from it. This way, the kernel can use the memory for
521 pagecache and when a subsystem requests for contiguous area, the
522 allocated pages are migrated away to serve the contiguous request.
527 bool "CMA debug messages (DEVELOPMENT)"
528 depends on DEBUG_KERNEL && CMA
530 Turns on debug messages in CMA. This produces KERN_DEBUG
531 messages for every CMA call as well as various messages while
532 processing calls such as dma_alloc_from_contiguous().
533 This option does not affect warning and error messages.
536 bool "CMA debugfs interface"
537 depends on CMA && DEBUG_FS
539 Turns on the DebugFS interface for CMA.
542 bool "CMA information through sysfs interface"
543 depends on CMA && SYSFS
545 This option exposes some sysfs attributes to get information
549 int "Maximum count of the CMA areas"
554 CMA allows to create CMA areas for particular purpose, mainly,
555 used as device private area. This parameter sets the maximum
556 number of CMA area in the system.
558 If unsure, leave the default value "7" in UMA and "19" in NUMA.
560 config MEM_SOFT_DIRTY
561 bool "Track memory changes"
562 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
563 select PROC_PAGE_MONITOR
565 This option enables memory changes tracking by introducing a
566 soft-dirty bit on pte-s. This bit it set when someone writes
567 into a page just as regular dirty bit, but unlike the latter
568 it can be cleared by hands.
570 See Documentation/admin-guide/mm/soft-dirty.rst for more details.
573 bool "Compressed cache for swap pages (EXPERIMENTAL)"
574 depends on FRONTSWAP && CRYPTO=y
577 A lightweight compressed cache for swap pages. It takes
578 pages that are in the process of being swapped out and attempts to
579 compress them into a dynamically allocated RAM-based memory pool.
580 This can result in a significant I/O reduction on swap device and,
581 in the case where decompressing from RAM is faster that swap device
582 reads, can also improve workload performance.
584 This is marked experimental because it is a new feature (as of
585 v3.11) that interacts heavily with memory reclaim. While these
586 interactions don't cause any known issues on simple memory setups,
587 they have not be fully explored on the large set of potential
588 configurations and workloads that exist.
591 prompt "Compressed cache for swap pages default compressor"
593 default ZSWAP_COMPRESSOR_DEFAULT_LZO
595 Selects the default compression algorithm for the compressed cache
598 For an overview what kind of performance can be expected from
599 a particular compression algorithm please refer to the benchmarks
600 available at the following LWN page:
601 https://lwn.net/Articles/751795/
603 If in doubt, select 'LZO'.
605 The selection made here can be overridden by using the kernel
606 command line 'zswap.compressor=' option.
608 config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
610 select CRYPTO_DEFLATE
612 Use the Deflate algorithm as the default compression algorithm.
614 config ZSWAP_COMPRESSOR_DEFAULT_LZO
618 Use the LZO algorithm as the default compression algorithm.
620 config ZSWAP_COMPRESSOR_DEFAULT_842
624 Use the 842 algorithm as the default compression algorithm.
626 config ZSWAP_COMPRESSOR_DEFAULT_LZ4
630 Use the LZ4 algorithm as the default compression algorithm.
632 config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
636 Use the LZ4HC algorithm as the default compression algorithm.
638 config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
642 Use the zstd algorithm as the default compression algorithm.
645 config ZSWAP_COMPRESSOR_DEFAULT
648 default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
649 default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
650 default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
651 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
652 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
653 default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
657 prompt "Compressed cache for swap pages default allocator"
659 default ZSWAP_ZPOOL_DEFAULT_ZBUD
661 Selects the default allocator for the compressed cache for
663 The default is 'zbud' for compatibility, however please do
664 read the description of each of the allocators below before
665 making a right choice.
667 The selection made here can be overridden by using the kernel
668 command line 'zswap.zpool=' option.
670 config ZSWAP_ZPOOL_DEFAULT_ZBUD
674 Use the zbud allocator as the default allocator.
676 config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
680 Use the z3fold allocator as the default allocator.
682 config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
686 Use the zsmalloc allocator as the default allocator.
689 config ZSWAP_ZPOOL_DEFAULT
692 default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
693 default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
694 default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
697 config ZSWAP_DEFAULT_ON
698 bool "Enable the compressed cache for swap pages by default"
701 If selected, the compressed cache for swap pages will be enabled
702 at boot, otherwise it will be disabled.
704 The selection made here can be overridden by using the kernel
705 command line 'zswap.enabled=' option.
708 tristate "Common API for compressed memory storage"
710 Compressed memory storage API. This allows using either zbud or
714 tristate "Low (Up to 2x) density storage for compressed pages"
716 A special purpose allocator for storing compressed pages.
717 It is designed to store up to two compressed pages per physical
718 page. While this design limits storage density, it has simple and
719 deterministic reclaim properties that make it preferable to a higher
720 density approach when reclaim will be used.
723 tristate "Up to 3x density storage for compressed pages"
726 A special purpose allocator for storing compressed pages.
727 It is designed to store up to three compressed pages per physical
728 page. It is a ZBUD derivative so the simplicity and determinism are
732 tristate "Memory allocator for compressed pages"
735 zsmalloc is a slab-based memory allocator designed to store
736 compressed RAM pages. zsmalloc uses virtual memory mapping
737 in order to reduce fragmentation. However, this results in a
738 non-standard allocator interface where a handle, not a pointer, is
739 returned by an alloc(). This handle must be mapped in order to
740 access the allocated space.
743 bool "Export zsmalloc statistics"
747 This option enables code in the zsmalloc to collect various
748 statistics about whats happening in zsmalloc and exports that
749 information to userspace via debugfs.
752 config GENERIC_EARLY_IOREMAP
755 config MAX_STACK_SIZE_MB
756 int "Maximum user stack size for 32-bit processes (MB)"
759 depends on STACK_GROWSUP && (!64BIT || COMPAT)
761 This is the maximum stack size in Megabytes in the VM layout of 32-bit
762 user processes when the stack grows upwards (currently only on parisc
763 arch). The stack will be located at the highest memory address minus
764 the given value, unless the RLIMIT_STACK hard limit is changed to a
765 smaller value in which case that is used.
767 A sane initial value is 80 MB.
769 config DEFERRED_STRUCT_PAGE_INIT
770 bool "Defer initialisation of struct pages to kthreads"
772 depends on !NEED_PER_CPU_KM
776 Ordinarily all struct pages are initialised during early boot in a
777 single thread. On very large machines this can take a considerable
778 amount of time. If this option is set, large machines will bring up
779 a subset of memmap at boot and then initialise the rest in parallel.
780 This has a potential performance impact on tasks running early in the
781 lifetime of the system until these kthreads finish the
784 config IDLE_PAGE_TRACKING
785 bool "Enable idle page tracking"
786 depends on SYSFS && MMU
787 select PAGE_EXTENSION if !64BIT
789 This feature allows to estimate the amount of user pages that have
790 not been touched during a given period of time. This information can
791 be useful to tune memory cgroup limits and/or for job placement
792 within a compute cluster.
794 See Documentation/admin-guide/mm/idle_page_tracking.rst for
797 config ARCH_HAS_PTE_DEVMAP
801 bool "Device memory (pmem, HMM, etc...) hotplug support"
802 depends on MEMORY_HOTPLUG
803 depends on MEMORY_HOTREMOVE
804 depends on SPARSEMEM_VMEMMAP
805 depends on ARCH_HAS_PTE_DEVMAP
809 Device memory hotplug support allows for establishing pmem,
810 or other device driver discovered memory regions, in the
811 memmap. This allows pfn_to_page() lookups of otherwise
812 "device-physical" addresses which is needed for using a DAX
813 mapping in an O_DIRECT operation, among other things.
815 If FS_DAX is enabled, then say Y.
817 config DEV_PAGEMAP_OPS
821 # Helpers to mirror range of the CPU page tables of a process into device page
828 config DEVICE_PRIVATE
829 bool "Unaddressable device memory (GPU memory, ...)"
830 depends on ZONE_DEVICE
831 select DEV_PAGEMAP_OPS
834 Allows creation of struct pages to represent unaddressable device
835 memory; i.e., memory that is only accessible from the device (or
836 group of devices). You likely also want to select HMM_MIRROR.
844 config ARCH_USES_HIGH_VMA_FLAGS
846 config ARCH_HAS_PKEYS
850 bool "Collect percpu memory statistics"
852 This feature collects and exposes statistics via debugfs. The
853 information includes global and per chunk statistics, which can
854 be used to help understand percpu memory usage.
857 bool "Enable infrastructure for get_user_pages() and related calls benchmarking"
859 Provides /sys/kernel/debug/gup_benchmark that helps with testing
860 performance of get_user_pages() and related calls.
862 See tools/testing/selftests/vm/gup_benchmark.c
864 config GUP_GET_PTE_LOW_HIGH
867 config READ_ONLY_THP_FOR_FS
868 bool "Read-only THP for filesystems (EXPERIMENTAL)"
869 depends on TRANSPARENT_HUGEPAGE && SHMEM
872 Allow khugepaged to put read-only file-backed pages in THP.
874 This is marked experimental because it is a new feature. Write
875 support of file THPs will be developed in the next few release
878 config FINEGRAINED_THP
879 bool "Fine-grained THP support (EXPERIMENTAL)"
880 depends on TRANSPARENT_HUGEPAGE
883 Allow khugepaged to create 64KB hugepages and 64KB hugepage
884 allocation on page faults.
886 It is only supported by ARM64 architecture for now.
888 config THP_CONSERVATIVE
889 bool "A conservative policy for fTHP (EXPERIMENTAL)"
890 depends on FINEGRAINED_THP
893 In the conservative policy, only khugepaged can make hugepages
895 config ARCH_HAS_PTE_SPECIAL
899 # Some architectures require a special hugepage directory format that is
900 # required to support multiple hugepage sizes. For example a4fe3ce76
901 # "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
902 # introduced it on powerpc. This allows for a more flexible hugepage
905 config ARCH_HAS_HUGEPD
908 config MAPPING_DIRTY_HELPERS