xref: /openbmc/linux/mm/Kconfig (revision 021ed9f5)
1# SPDX-License-Identifier: GPL-2.0-only
2
3menu "Memory Management options"
4
5config SELECT_MEMORY_MODEL
6	def_bool y
7	depends on ARCH_SELECT_MEMORY_MODEL
8
9choice
10	prompt "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
15	help
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.
20
21config FLATMEM_MANUAL
22	bool "Flat Memory"
23	depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
24	help
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.
29
30	  For systems that have holes in their physical address
31	  spaces and for features like NUMA and memory hotplug,
32	  choose "Sparse Memory".
33
34	  If unsure, choose this option (Flat Memory) over any other.
35
36config DISCONTIGMEM_MANUAL
37	bool "Discontiguous Memory"
38	depends on ARCH_DISCONTIGMEM_ENABLE
39	help
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.
44
45	  Although "Discontiguous Memory" is still used by several
46	  architectures, it is considered deprecated in favor of
47	  "Sparse Memory".
48
49	  If unsure, choose "Sparse Memory" over this option.
50
51config SPARSEMEM_MANUAL
52	bool "Sparse Memory"
53	depends on ARCH_SPARSEMEM_ENABLE
54	help
55	  This will be the only option for some systems, including
56	  memory hot-plug systems.  This is normal.
57
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.
61
62	  If unsure, choose "Flat Memory" over this option.
63
64endchoice
65
66config DISCONTIGMEM
67	def_bool y
68	depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
69
70config SPARSEMEM
71	def_bool y
72	depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
73
74config FLATMEM
75	def_bool y
76	depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
77
78config FLAT_NODE_MEM_MAP
79	def_bool y
80	depends on !SPARSEMEM
81
82#
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.
86#
87config NEED_MULTIPLE_NODES
88	def_bool y
89	depends on DISCONTIGMEM || NUMA
90
91config HAVE_MEMORY_PRESENT
92	def_bool y
93	depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
94
95#
96# SPARSEMEM_EXTREME (which is the default) does some bootmem
97# allocations when memory_present() is called.  If this cannot
98# be done on your architecture, select this option.  However,
99# statically allocating the mem_section[] array can potentially
100# consume vast quantities of .bss, so be careful.
101#
102# This option will also potentially produce smaller runtime code
103# with gcc 3.4 and later.
104#
105config SPARSEMEM_STATIC
106	bool
107
108#
109# Architecture platforms which require a two level mem_section in SPARSEMEM
110# must select this option. This is usually for architecture platforms with
111# an extremely sparse physical address space.
112#
113config SPARSEMEM_EXTREME
114	def_bool y
115	depends on SPARSEMEM && !SPARSEMEM_STATIC
116
117config SPARSEMEM_VMEMMAP_ENABLE
118	bool
119
120config SPARSEMEM_VMEMMAP
121	bool "Sparse Memory virtual memmap"
122	depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
123	default y
124	help
125	  SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
126	  pfn_to_page and page_to_pfn operations.  This is the most
127	  efficient option when sufficient kernel resources are available.
128
129config HAVE_MEMBLOCK_NODE_MAP
130	bool
131
132config HAVE_MEMBLOCK_PHYS_MAP
133	bool
134
135config HAVE_FAST_GUP
136	depends on MMU
137	bool
138
139config ARCH_KEEP_MEMBLOCK
140	bool
141
142config MEMORY_ISOLATION
143	bool
144
145#
146# Only be set on architectures that have completely implemented memory hotplug
147# feature. If you are not sure, don't touch it.
148#
149config HAVE_BOOTMEM_INFO_NODE
150	def_bool n
151
152# eventually, we can have this option just 'select SPARSEMEM'
153config MEMORY_HOTPLUG
154	bool "Allow for memory hot-add"
155	depends on SPARSEMEM || X86_64_ACPI_NUMA
156	depends on ARCH_ENABLE_MEMORY_HOTPLUG
157
158config MEMORY_HOTPLUG_SPARSE
159	def_bool y
160	depends on SPARSEMEM && MEMORY_HOTPLUG
161
162config MEMORY_HOTPLUG_DEFAULT_ONLINE
163	bool "Online the newly added memory blocks by default"
164	depends on MEMORY_HOTPLUG
165	help
166	  This option sets the default policy setting for memory hotplug
167	  onlining policy (/sys/devices/system/memory/auto_online_blocks) which
168	  determines what happens to newly added memory regions. Policy setting
169	  can always be changed at runtime.
170	  See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
171
172	  Say Y here if you want all hot-plugged memory blocks to appear in
173	  'online' state by default.
174	  Say N here if you want the default policy to keep all hot-plugged
175	  memory blocks in 'offline' state.
176
177config MEMORY_HOTREMOVE
178	bool "Allow for memory hot remove"
179	select MEMORY_ISOLATION
180	select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
181	depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
182	depends on MIGRATION
183
184# Heavily threaded applications may benefit from splitting the mm-wide
185# page_table_lock, so that faults on different parts of the user address
186# space can be handled with less contention: split it at this NR_CPUS.
187# Default to 4 for wider testing, though 8 might be more appropriate.
188# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
189# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
190# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
191#
192config SPLIT_PTLOCK_CPUS
193	int
194	default "999999" if !MMU
195	default "999999" if ARM && !CPU_CACHE_VIPT
196	default "999999" if PARISC && !PA20
197	default "4"
198
199config ARCH_ENABLE_SPLIT_PMD_PTLOCK
200	bool
201
202#
203# support for memory balloon
204config MEMORY_BALLOON
205	bool
206
207#
208# support for memory balloon compaction
209config BALLOON_COMPACTION
210	bool "Allow for balloon memory compaction/migration"
211	def_bool y
212	depends on COMPACTION && MEMORY_BALLOON
213	help
214	  Memory fragmentation introduced by ballooning might reduce
215	  significantly the number of 2MB contiguous memory blocks that can be
216	  used within a guest, thus imposing performance penalties associated
217	  with the reduced number of transparent huge pages that could be used
218	  by the guest workload. Allowing the compaction & migration for memory
219	  pages enlisted as being part of memory balloon devices avoids the
220	  scenario aforementioned and helps improving memory defragmentation.
221
222#
223# support for memory compaction
224config COMPACTION
225	bool "Allow for memory compaction"
226	def_bool y
227	select MIGRATION
228	depends on MMU
229	help
230	  Compaction is the only memory management component to form
231	  high order (larger physically contiguous) memory blocks
232	  reliably. The page allocator relies on compaction heavily and
233	  the lack of the feature can lead to unexpected OOM killer
234	  invocations for high order memory requests. You shouldn't
235	  disable this option unless there really is a strong reason for
236	  it and then we would be really interested to hear about that at
237	  linux-mm@kvack.org.
238
239#
240# support for page migration
241#
242config MIGRATION
243	bool "Page migration"
244	def_bool y
245	depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
246	help
247	  Allows the migration of the physical location of pages of processes
248	  while the virtual addresses are not changed. This is useful in
249	  two situations. The first is on NUMA systems to put pages nearer
250	  to the processors accessing. The second is when allocating huge
251	  pages as migration can relocate pages to satisfy a huge page
252	  allocation instead of reclaiming.
253
254config ARCH_ENABLE_HUGEPAGE_MIGRATION
255	bool
256
257config ARCH_ENABLE_THP_MIGRATION
258	bool
259
260config CONTIG_ALLOC
261	def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
262
263config PHYS_ADDR_T_64BIT
264	def_bool 64BIT
265
266config BOUNCE
267	bool "Enable bounce buffers"
268	default y
269	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
270	help
271	  Enable bounce buffers for devices that cannot access
272	  the full range of memory available to the CPU. Enabled
273	  by default when ZONE_DMA or HIGHMEM is selected, but you
274	  may say n to override this.
275
276config VIRT_TO_BUS
277	bool
278	help
279	  An architecture should select this if it implements the
280	  deprecated interface virt_to_bus().  All new architectures
281	  should probably not select this.
282
283
284config MMU_NOTIFIER
285	bool
286	select SRCU
287	select INTERVAL_TREE
288
289config KSM
290	bool "Enable KSM for page merging"
291	depends on MMU
292	select XXHASH
293	help
294	  Enable Kernel Samepage Merging: KSM periodically scans those areas
295	  of an application's address space that an app has advised may be
296	  mergeable.  When it finds pages of identical content, it replaces
297	  the many instances by a single page with that content, so
298	  saving memory until one or another app needs to modify the content.
299	  Recommended for use with KVM, or with other duplicative applications.
300	  See Documentation/vm/ksm.rst for more information: KSM is inactive
301	  until a program has madvised that an area is MADV_MERGEABLE, and
302	  root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
303
304config DEFAULT_MMAP_MIN_ADDR
305	int "Low address space to protect from user allocation"
306	depends on MMU
307	default 4096
308	help
309	  This is the portion of low virtual memory which should be protected
310	  from userspace allocation.  Keeping a user from writing to low pages
311	  can help reduce the impact of kernel NULL pointer bugs.
312
313	  For most ia64, ppc64 and x86 users with lots of address space
314	  a value of 65536 is reasonable and should cause no problems.
315	  On arm and other archs it should not be higher than 32768.
316	  Programs which use vm86 functionality or have some need to map
317	  this low address space will need CAP_SYS_RAWIO or disable this
318	  protection by setting the value to 0.
319
320	  This value can be changed after boot using the
321	  /proc/sys/vm/mmap_min_addr tunable.
322
323config ARCH_SUPPORTS_MEMORY_FAILURE
324	bool
325
326config MEMORY_FAILURE
327	depends on MMU
328	depends on ARCH_SUPPORTS_MEMORY_FAILURE
329	bool "Enable recovery from hardware memory errors"
330	select MEMORY_ISOLATION
331	select RAS
332	help
333	  Enables code to recover from some memory failures on systems
334	  with MCA recovery. This allows a system to continue running
335	  even when some of its memory has uncorrected errors. This requires
336	  special hardware support and typically ECC memory.
337
338config HWPOISON_INJECT
339	tristate "HWPoison pages injector"
340	depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
341	select PROC_PAGE_MONITOR
342
343config NOMMU_INITIAL_TRIM_EXCESS
344	int "Turn on mmap() excess space trimming before booting"
345	depends on !MMU
346	default 1
347	help
348	  The NOMMU mmap() frequently needs to allocate large contiguous chunks
349	  of memory on which to store mappings, but it can only ask the system
350	  allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
351	  more than it requires.  To deal with this, mmap() is able to trim off
352	  the excess and return it to the allocator.
353
354	  If trimming is enabled, the excess is trimmed off and returned to the
355	  system allocator, which can cause extra fragmentation, particularly
356	  if there are a lot of transient processes.
357
358	  If trimming is disabled, the excess is kept, but not used, which for
359	  long-term mappings means that the space is wasted.
360
361	  Trimming can be dynamically controlled through a sysctl option
362	  (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
363	  excess pages there must be before trimming should occur, or zero if
364	  no trimming is to occur.
365
366	  This option specifies the initial value of this option.  The default
367	  of 1 says that all excess pages should be trimmed.
368
369	  See Documentation/nommu-mmap.txt for more information.
370
371config TRANSPARENT_HUGEPAGE
372	bool "Transparent Hugepage Support"
373	depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
374	select COMPACTION
375	select XARRAY_MULTI
376	help
377	  Transparent Hugepages allows the kernel to use huge pages and
378	  huge tlb transparently to the applications whenever possible.
379	  This feature can improve computing performance to certain
380	  applications by speeding up page faults during memory
381	  allocation, by reducing the number of tlb misses and by speeding
382	  up the pagetable walking.
383
384	  If memory constrained on embedded, you may want to say N.
385
386choice
387	prompt "Transparent Hugepage Support sysfs defaults"
388	depends on TRANSPARENT_HUGEPAGE
389	default TRANSPARENT_HUGEPAGE_ALWAYS
390	help
391	  Selects the sysfs defaults for Transparent Hugepage Support.
392
393	config TRANSPARENT_HUGEPAGE_ALWAYS
394		bool "always"
395	help
396	  Enabling Transparent Hugepage always, can increase the
397	  memory footprint of applications without a guaranteed
398	  benefit but it will work automatically for all applications.
399
400	config TRANSPARENT_HUGEPAGE_MADVISE
401		bool "madvise"
402	help
403	  Enabling Transparent Hugepage madvise, will only provide a
404	  performance improvement benefit to the applications using
405	  madvise(MADV_HUGEPAGE) but it won't risk to increase the
406	  memory footprint of applications without a guaranteed
407	  benefit.
408endchoice
409
410config ARCH_WANTS_THP_SWAP
411	def_bool n
412
413config THP_SWAP
414	def_bool y
415	depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
416	help
417	  Swap transparent huge pages in one piece, without splitting.
418	  XXX: For now, swap cluster backing transparent huge page
419	  will be split after swapout.
420
421	  For selection by architectures with reasonable THP sizes.
422
423config	TRANSPARENT_HUGE_PAGECACHE
424	def_bool y
425	depends on TRANSPARENT_HUGEPAGE
426
427#
428# UP and nommu archs use km based percpu allocator
429#
430config NEED_PER_CPU_KM
431	depends on !SMP
432	bool
433	default y
434
435config CLEANCACHE
436	bool "Enable cleancache driver to cache clean pages if tmem is present"
437	help
438	  Cleancache can be thought of as a page-granularity victim cache
439	  for clean pages that the kernel's pageframe replacement algorithm
440	  (PFRA) would like to keep around, but can't since there isn't enough
441	  memory.  So when the PFRA "evicts" a page, it first attempts to use
442	  cleancache code to put the data contained in that page into
443	  "transcendent memory", memory that is not directly accessible or
444	  addressable by the kernel and is of unknown and possibly
445	  time-varying size.  And when a cleancache-enabled
446	  filesystem wishes to access a page in a file on disk, it first
447	  checks cleancache to see if it already contains it; if it does,
448	  the page is copied into the kernel and a disk access is avoided.
449	  When a transcendent memory driver is available (such as zcache or
450	  Xen transcendent memory), a significant I/O reduction
451	  may be achieved.  When none is available, all cleancache calls
452	  are reduced to a single pointer-compare-against-NULL resulting
453	  in a negligible performance hit.
454
455	  If unsure, say Y to enable cleancache
456
457config FRONTSWAP
458	bool "Enable frontswap to cache swap pages if tmem is present"
459	depends on SWAP
460	help
461	  Frontswap is so named because it can be thought of as the opposite
462	  of a "backing" store for a swap device.  The data is stored into
463	  "transcendent memory", memory that is not directly accessible or
464	  addressable by the kernel and is of unknown and possibly
465	  time-varying size.  When space in transcendent memory is available,
466	  a significant swap I/O reduction may be achieved.  When none is
467	  available, all frontswap calls are reduced to a single pointer-
468	  compare-against-NULL resulting in a negligible performance hit
469	  and swap data is stored as normal on the matching swap device.
470
471	  If unsure, say Y to enable frontswap.
472
473config CMA
474	bool "Contiguous Memory Allocator"
475	depends on MMU
476	select MIGRATION
477	select MEMORY_ISOLATION
478	help
479	  This enables the Contiguous Memory Allocator which allows other
480	  subsystems to allocate big physically-contiguous blocks of memory.
481	  CMA reserves a region of memory and allows only movable pages to
482	  be allocated from it. This way, the kernel can use the memory for
483	  pagecache and when a subsystem requests for contiguous area, the
484	  allocated pages are migrated away to serve the contiguous request.
485
486	  If unsure, say "n".
487
488config CMA_DEBUG
489	bool "CMA debug messages (DEVELOPMENT)"
490	depends on DEBUG_KERNEL && CMA
491	help
492	  Turns on debug messages in CMA.  This produces KERN_DEBUG
493	  messages for every CMA call as well as various messages while
494	  processing calls such as dma_alloc_from_contiguous().
495	  This option does not affect warning and error messages.
496
497config CMA_DEBUGFS
498	bool "CMA debugfs interface"
499	depends on CMA && DEBUG_FS
500	help
501	  Turns on the DebugFS interface for CMA.
502
503config CMA_AREAS
504	int "Maximum count of the CMA areas"
505	depends on CMA
506	default 7
507	help
508	  CMA allows to create CMA areas for particular purpose, mainly,
509	  used as device private area. This parameter sets the maximum
510	  number of CMA area in the system.
511
512	  If unsure, leave the default value "7".
513
514config MEM_SOFT_DIRTY
515	bool "Track memory changes"
516	depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
517	select PROC_PAGE_MONITOR
518	help
519	  This option enables memory changes tracking by introducing a
520	  soft-dirty bit on pte-s. This bit it set when someone writes
521	  into a page just as regular dirty bit, but unlike the latter
522	  it can be cleared by hands.
523
524	  See Documentation/admin-guide/mm/soft-dirty.rst for more details.
525
526config ZSWAP
527	bool "Compressed cache for swap pages (EXPERIMENTAL)"
528	depends on FRONTSWAP && CRYPTO=y
529	select CRYPTO_LZO
530	select ZPOOL
531	help
532	  A lightweight compressed cache for swap pages.  It takes
533	  pages that are in the process of being swapped out and attempts to
534	  compress them into a dynamically allocated RAM-based memory pool.
535	  This can result in a significant I/O reduction on swap device and,
536	  in the case where decompressing from RAM is faster that swap device
537	  reads, can also improve workload performance.
538
539	  This is marked experimental because it is a new feature (as of
540	  v3.11) that interacts heavily with memory reclaim.  While these
541	  interactions don't cause any known issues on simple memory setups,
542	  they have not be fully explored on the large set of potential
543	  configurations and workloads that exist.
544
545config ZPOOL
546	tristate "Common API for compressed memory storage"
547	help
548	  Compressed memory storage API.  This allows using either zbud or
549	  zsmalloc.
550
551config ZBUD
552	tristate "Low (Up to 2x) density storage for compressed pages"
553	help
554	  A special purpose allocator for storing compressed pages.
555	  It is designed to store up to two compressed pages per physical
556	  page.  While this design limits storage density, it has simple and
557	  deterministic reclaim properties that make it preferable to a higher
558	  density approach when reclaim will be used.
559
560config Z3FOLD
561	tristate "Up to 3x density storage for compressed pages"
562	depends on ZPOOL
563	help
564	  A special purpose allocator for storing compressed pages.
565	  It is designed to store up to three compressed pages per physical
566	  page. It is a ZBUD derivative so the simplicity and determinism are
567	  still there.
568
569config ZSMALLOC
570	tristate "Memory allocator for compressed pages"
571	depends on MMU
572	help
573	  zsmalloc is a slab-based memory allocator designed to store
574	  compressed RAM pages.  zsmalloc uses virtual memory mapping
575	  in order to reduce fragmentation.  However, this results in a
576	  non-standard allocator interface where a handle, not a pointer, is
577	  returned by an alloc().  This handle must be mapped in order to
578	  access the allocated space.
579
580config PGTABLE_MAPPING
581	bool "Use page table mapping to access object in zsmalloc"
582	depends on ZSMALLOC
583	help
584	  By default, zsmalloc uses a copy-based object mapping method to
585	  access allocations that span two pages. However, if a particular
586	  architecture (ex, ARM) performs VM mapping faster than copying,
587	  then you should select this. This causes zsmalloc to use page table
588	  mapping rather than copying for object mapping.
589
590	  You can check speed with zsmalloc benchmark:
591	  https://github.com/spartacus06/zsmapbench
592
593config ZSMALLOC_STAT
594	bool "Export zsmalloc statistics"
595	depends on ZSMALLOC
596	select DEBUG_FS
597	help
598	  This option enables code in the zsmalloc to collect various
599	  statistics about whats happening in zsmalloc and exports that
600	  information to userspace via debugfs.
601	  If unsure, say N.
602
603config GENERIC_EARLY_IOREMAP
604	bool
605
606config MAX_STACK_SIZE_MB
607	int "Maximum user stack size for 32-bit processes (MB)"
608	default 80
609	range 8 2048
610	depends on STACK_GROWSUP && (!64BIT || COMPAT)
611	help
612	  This is the maximum stack size in Megabytes in the VM layout of 32-bit
613	  user processes when the stack grows upwards (currently only on parisc
614	  arch). The stack will be located at the highest memory address minus
615	  the given value, unless the RLIMIT_STACK hard limit is changed to a
616	  smaller value in which case that is used.
617
618	  A sane initial value is 80 MB.
619
620config DEFERRED_STRUCT_PAGE_INIT
621	bool "Defer initialisation of struct pages to kthreads"
622	depends on SPARSEMEM
623	depends on !NEED_PER_CPU_KM
624	depends on 64BIT
625	help
626	  Ordinarily all struct pages are initialised during early boot in a
627	  single thread. On very large machines this can take a considerable
628	  amount of time. If this option is set, large machines will bring up
629	  a subset of memmap at boot and then initialise the rest in parallel
630	  by starting one-off "pgdatinitX" kernel thread for each node X. This
631	  has a potential performance impact on processes running early in the
632	  lifetime of the system until these kthreads finish the
633	  initialisation.
634
635config IDLE_PAGE_TRACKING
636	bool "Enable idle page tracking"
637	depends on SYSFS && MMU
638	select PAGE_EXTENSION if !64BIT
639	help
640	  This feature allows to estimate the amount of user pages that have
641	  not been touched during a given period of time. This information can
642	  be useful to tune memory cgroup limits and/or for job placement
643	  within a compute cluster.
644
645	  See Documentation/admin-guide/mm/idle_page_tracking.rst for
646	  more details.
647
648config ARCH_HAS_PTE_DEVMAP
649	bool
650
651config ZONE_DEVICE
652	bool "Device memory (pmem, HMM, etc...) hotplug support"
653	depends on MEMORY_HOTPLUG
654	depends on MEMORY_HOTREMOVE
655	depends on SPARSEMEM_VMEMMAP
656	depends on ARCH_HAS_PTE_DEVMAP
657	select XARRAY_MULTI
658
659	help
660	  Device memory hotplug support allows for establishing pmem,
661	  or other device driver discovered memory regions, in the
662	  memmap. This allows pfn_to_page() lookups of otherwise
663	  "device-physical" addresses which is needed for using a DAX
664	  mapping in an O_DIRECT operation, among other things.
665
666	  If FS_DAX is enabled, then say Y.
667
668config DEV_PAGEMAP_OPS
669	bool
670
671#
672# Helpers to mirror range of the CPU page tables of a process into device page
673# tables.
674#
675config HMM_MIRROR
676	bool
677	depends on MMU
678
679config DEVICE_PRIVATE
680	bool "Unaddressable device memory (GPU memory, ...)"
681	depends on ZONE_DEVICE
682	select DEV_PAGEMAP_OPS
683
684	help
685	  Allows creation of struct pages to represent unaddressable device
686	  memory; i.e., memory that is only accessible from the device (or
687	  group of devices). You likely also want to select HMM_MIRROR.
688
689config FRAME_VECTOR
690	bool
691
692config ARCH_USES_HIGH_VMA_FLAGS
693	bool
694config ARCH_HAS_PKEYS
695	bool
696
697config PERCPU_STATS
698	bool "Collect percpu memory statistics"
699	help
700	  This feature collects and exposes statistics via debugfs. The
701	  information includes global and per chunk statistics, which can
702	  be used to help understand percpu memory usage.
703
704config GUP_BENCHMARK
705	bool "Enable infrastructure for get_user_pages_fast() benchmarking"
706	help
707	  Provides /sys/kernel/debug/gup_benchmark that helps with testing
708	  performance of get_user_pages_fast().
709
710	  See tools/testing/selftests/vm/gup_benchmark.c
711
712config GUP_GET_PTE_LOW_HIGH
713	bool
714
715config READ_ONLY_THP_FOR_FS
716	bool "Read-only THP for filesystems (EXPERIMENTAL)"
717	depends on TRANSPARENT_HUGE_PAGECACHE && SHMEM
718
719	help
720	  Allow khugepaged to put read-only file-backed pages in THP.
721
722	  This is marked experimental because it is a new feature. Write
723	  support of file THPs will be developed in the next few release
724	  cycles.
725
726config ARCH_HAS_PTE_SPECIAL
727	bool
728
729#
730# Some architectures require a special hugepage directory format that is
731# required to support multiple hugepage sizes. For example a4fe3ce76
732# "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
733# introduced it on powerpc.  This allows for a more flexible hugepage
734# pagetable layouts.
735#
736config ARCH_HAS_HUGEPD
737	bool
738
739config MAPPING_DIRTY_HELPERS
740        bool
741
742endmenu
743