1# SPDX-License-Identifier: GPL-2.0-only
2
3menu "Memory Management options"
4
5#
6# For some reason microblaze and nios2 hard code SWAP=n.  Hopefully we can
7# add proper SWAP support to them, in which case this can be remove.
8#
9config ARCH_NO_SWAP
10	bool
11
12config ZPOOL
13	bool
14
15menuconfig SWAP
16	bool "Support for paging of anonymous memory (swap)"
17	depends on MMU && BLOCK && !ARCH_NO_SWAP
18	default y
19	help
20	  This option allows you to choose whether you want to have support
21	  for so called swap devices or swap files in your kernel that are
22	  used to provide more virtual memory than the actual RAM present
23	  in your computer.  If unsure say Y.
24
25config ZSWAP
26	bool "Compressed cache for swap pages"
27	depends on SWAP
28	select CRYPTO
29	select ZPOOL
30	help
31	  A lightweight compressed cache for swap pages.  It takes
32	  pages that are in the process of being swapped out and attempts to
33	  compress them into a dynamically allocated RAM-based memory pool.
34	  This can result in a significant I/O reduction on swap device and,
35	  in the case where decompressing from RAM is faster than swap device
36	  reads, can also improve workload performance.
37
38config ZSWAP_DEFAULT_ON
39	bool "Enable the compressed cache for swap pages by default"
40	depends on ZSWAP
41	help
42	  If selected, the compressed cache for swap pages will be enabled
43	  at boot, otherwise it will be disabled.
44
45	  The selection made here can be overridden by using the kernel
46	  command line 'zswap.enabled=' option.
47
48config ZSWAP_EXCLUSIVE_LOADS_DEFAULT_ON
49	bool "Invalidate zswap entries when pages are loaded"
50	depends on ZSWAP
51	help
52	  If selected, exclusive loads for zswap will be enabled at boot,
53	  otherwise it will be disabled.
54
55	  If exclusive loads are enabled, when a page is loaded from zswap,
56	  the zswap entry is invalidated at once, as opposed to leaving it
57	  in zswap until the swap entry is freed.
58
59	  This avoids having two copies of the same page in memory
60	  (compressed and uncompressed) after faulting in a page from zswap.
61	  The cost is that if the page was never dirtied and needs to be
62	  swapped out again, it will be re-compressed.
63
64choice
65	prompt "Default compressor"
66	depends on ZSWAP
67	default ZSWAP_COMPRESSOR_DEFAULT_LZO
68	help
69	  Selects the default compression algorithm for the compressed cache
70	  for swap pages.
71
72	  For an overview what kind of performance can be expected from
73	  a particular compression algorithm please refer to the benchmarks
74	  available at the following LWN page:
75	  https://lwn.net/Articles/751795/
76
77	  If in doubt, select 'LZO'.
78
79	  The selection made here can be overridden by using the kernel
80	  command line 'zswap.compressor=' option.
81
82config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
83	bool "Deflate"
84	select CRYPTO_DEFLATE
85	help
86	  Use the Deflate algorithm as the default compression algorithm.
87
88config ZSWAP_COMPRESSOR_DEFAULT_LZO
89	bool "LZO"
90	select CRYPTO_LZO
91	help
92	  Use the LZO algorithm as the default compression algorithm.
93
94config ZSWAP_COMPRESSOR_DEFAULT_842
95	bool "842"
96	select CRYPTO_842
97	help
98	  Use the 842 algorithm as the default compression algorithm.
99
100config ZSWAP_COMPRESSOR_DEFAULT_LZ4
101	bool "LZ4"
102	select CRYPTO_LZ4
103	help
104	  Use the LZ4 algorithm as the default compression algorithm.
105
106config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
107	bool "LZ4HC"
108	select CRYPTO_LZ4HC
109	help
110	  Use the LZ4HC algorithm as the default compression algorithm.
111
112config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
113	bool "zstd"
114	select CRYPTO_ZSTD
115	help
116	  Use the zstd algorithm as the default compression algorithm.
117endchoice
118
119config ZSWAP_COMPRESSOR_DEFAULT
120       string
121       depends on ZSWAP
122       default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
123       default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
124       default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
125       default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
126       default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
127       default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
128       default ""
129
130choice
131	prompt "Default allocator"
132	depends on ZSWAP
133	default ZSWAP_ZPOOL_DEFAULT_ZBUD
134	help
135	  Selects the default allocator for the compressed cache for
136	  swap pages.
137	  The default is 'zbud' for compatibility, however please do
138	  read the description of each of the allocators below before
139	  making a right choice.
140
141	  The selection made here can be overridden by using the kernel
142	  command line 'zswap.zpool=' option.
143
144config ZSWAP_ZPOOL_DEFAULT_ZBUD
145	bool "zbud"
146	select ZBUD
147	help
148	  Use the zbud allocator as the default allocator.
149
150config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
151	bool "z3fold"
152	select Z3FOLD
153	help
154	  Use the z3fold allocator as the default allocator.
155
156config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
157	bool "zsmalloc"
158	select ZSMALLOC
159	help
160	  Use the zsmalloc allocator as the default allocator.
161endchoice
162
163config ZSWAP_ZPOOL_DEFAULT
164       string
165       depends on ZSWAP
166       default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
167       default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
168       default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
169       default ""
170
171config ZBUD
172	tristate "2:1 compression allocator (zbud)"
173	depends on ZSWAP
174	help
175	  A special purpose allocator for storing compressed pages.
176	  It is designed to store up to two compressed pages per physical
177	  page.  While this design limits storage density, it has simple and
178	  deterministic reclaim properties that make it preferable to a higher
179	  density approach when reclaim will be used.
180
181config Z3FOLD
182	tristate "3:1 compression allocator (z3fold)"
183	depends on ZSWAP
184	help
185	  A special purpose allocator for storing compressed pages.
186	  It is designed to store up to three compressed pages per physical
187	  page. It is a ZBUD derivative so the simplicity and determinism are
188	  still there.
189
190config ZSMALLOC
191	tristate
192	prompt "N:1 compression allocator (zsmalloc)" if ZSWAP
193	depends on MMU
194	help
195	  zsmalloc is a slab-based memory allocator designed to store
196	  pages of various compression levels efficiently. It achieves
197	  the highest storage density with the least amount of fragmentation.
198
199config ZSMALLOC_STAT
200	bool "Export zsmalloc statistics"
201	depends on ZSMALLOC
202	select DEBUG_FS
203	help
204	  This option enables code in the zsmalloc to collect various
205	  statistics about what's happening in zsmalloc and exports that
206	  information to userspace via debugfs.
207	  If unsure, say N.
208
209config ZSMALLOC_CHAIN_SIZE
210	int "Maximum number of physical pages per-zspage"
211	default 8
212	range 4 16
213	depends on ZSMALLOC
214	help
215	  This option sets the upper limit on the number of physical pages
216	  that a zmalloc page (zspage) can consist of. The optimal zspage
217	  chain size is calculated for each size class during the
218	  initialization of the pool.
219
220	  Changing this option can alter the characteristics of size classes,
221	  such as the number of pages per zspage and the number of objects
222	  per zspage. This can also result in different configurations of
223	  the pool, as zsmalloc merges size classes with similar
224	  characteristics.
225
226	  For more information, see zsmalloc documentation.
227
228menu "SLAB allocator options"
229
230choice
231	prompt "Choose SLAB allocator"
232	default SLUB
233	help
234	   This option allows to select a slab allocator.
235
236config SLAB_DEPRECATED
237	bool "SLAB (DEPRECATED)"
238	depends on !PREEMPT_RT
239	help
240	  Deprecated and scheduled for removal in a few cycles. Replaced by
241	  SLUB.
242
243	  If you cannot migrate to SLUB, please contact linux-mm@kvack.org
244	  and the people listed in the SLAB ALLOCATOR section of MAINTAINERS
245	  file, explaining why.
246
247	  The regular slab allocator that is established and known to work
248	  well in all environments. It organizes cache hot objects in
249	  per cpu and per node queues.
250
251config SLUB
252	bool "SLUB (Unqueued Allocator)"
253	help
254	   SLUB is a slab allocator that minimizes cache line usage
255	   instead of managing queues of cached objects (SLAB approach).
256	   Per cpu caching is realized using slabs of objects instead
257	   of queues of objects. SLUB can use memory efficiently
258	   and has enhanced diagnostics. SLUB is the default choice for
259	   a slab allocator.
260
261endchoice
262
263config SLAB
264	bool
265	default y
266	depends on SLAB_DEPRECATED
267
268config SLUB_TINY
269	bool "Configure SLUB for minimal memory footprint"
270	depends on SLUB && EXPERT
271	select SLAB_MERGE_DEFAULT
272	help
273	   Configures the SLUB allocator in a way to achieve minimal memory
274	   footprint, sacrificing scalability, debugging and other features.
275	   This is intended only for the smallest system that had used the
276	   SLOB allocator and is not recommended for systems with more than
277	   16MB RAM.
278
279	   If unsure, say N.
280
281config SLAB_MERGE_DEFAULT
282	bool "Allow slab caches to be merged"
283	default y
284	depends on SLAB || SLUB
285	help
286	  For reduced kernel memory fragmentation, slab caches can be
287	  merged when they share the same size and other characteristics.
288	  This carries a risk of kernel heap overflows being able to
289	  overwrite objects from merged caches (and more easily control
290	  cache layout), which makes such heap attacks easier to exploit
291	  by attackers. By keeping caches unmerged, these kinds of exploits
292	  can usually only damage objects in the same cache. To disable
293	  merging at runtime, "slab_nomerge" can be passed on the kernel
294	  command line.
295
296config SLAB_FREELIST_RANDOM
297	bool "Randomize slab freelist"
298	depends on SLAB || (SLUB && !SLUB_TINY)
299	help
300	  Randomizes the freelist order used on creating new pages. This
301	  security feature reduces the predictability of the kernel slab
302	  allocator against heap overflows.
303
304config SLAB_FREELIST_HARDENED
305	bool "Harden slab freelist metadata"
306	depends on SLAB || (SLUB && !SLUB_TINY)
307	help
308	  Many kernel heap attacks try to target slab cache metadata and
309	  other infrastructure. This options makes minor performance
310	  sacrifices to harden the kernel slab allocator against common
311	  freelist exploit methods. Some slab implementations have more
312	  sanity-checking than others. This option is most effective with
313	  CONFIG_SLUB.
314
315config SLUB_STATS
316	default n
317	bool "Enable SLUB performance statistics"
318	depends on SLUB && SYSFS && !SLUB_TINY
319	help
320	  SLUB statistics are useful to debug SLUBs allocation behavior in
321	  order find ways to optimize the allocator. This should never be
322	  enabled for production use since keeping statistics slows down
323	  the allocator by a few percentage points. The slabinfo command
324	  supports the determination of the most active slabs to figure
325	  out which slabs are relevant to a particular load.
326	  Try running: slabinfo -DA
327
328config SLUB_CPU_PARTIAL
329	default y
330	depends on SLUB && SMP && !SLUB_TINY
331	bool "SLUB per cpu partial cache"
332	help
333	  Per cpu partial caches accelerate objects allocation and freeing
334	  that is local to a processor at the price of more indeterminism
335	  in the latency of the free. On overflow these caches will be cleared
336	  which requires the taking of locks that may cause latency spikes.
337	  Typically one would choose no for a realtime system.
338
339config RANDOM_KMALLOC_CACHES
340	default n
341	depends on SLUB && !SLUB_TINY
342	bool "Randomize slab caches for normal kmalloc"
343	help
344	  A hardening feature that creates multiple copies of slab caches for
345	  normal kmalloc allocation and makes kmalloc randomly pick one based
346	  on code address, which makes the attackers more difficult to spray
347	  vulnerable memory objects on the heap for the purpose of exploiting
348	  memory vulnerabilities.
349
350	  Currently the number of copies is set to 16, a reasonably large value
351	  that effectively diverges the memory objects allocated for different
352	  subsystems or modules into different caches, at the expense of a
353	  limited degree of memory and CPU overhead that relates to hardware and
354	  system workload.
355
356endmenu # SLAB allocator options
357
358config SHUFFLE_PAGE_ALLOCATOR
359	bool "Page allocator randomization"
360	default SLAB_FREELIST_RANDOM && ACPI_NUMA
361	help
362	  Randomization of the page allocator improves the average
363	  utilization of a direct-mapped memory-side-cache. See section
364	  5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
365	  6.2a specification for an example of how a platform advertises
366	  the presence of a memory-side-cache. There are also incidental
367	  security benefits as it reduces the predictability of page
368	  allocations to compliment SLAB_FREELIST_RANDOM, but the
369	  default granularity of shuffling on the MAX_ORDER i.e, 10th
370	  order of pages is selected based on cache utilization benefits
371	  on x86.
372
373	  While the randomization improves cache utilization it may
374	  negatively impact workloads on platforms without a cache. For
375	  this reason, by default, the randomization is enabled only
376	  after runtime detection of a direct-mapped memory-side-cache.
377	  Otherwise, the randomization may be force enabled with the
378	  'page_alloc.shuffle' kernel command line parameter.
379
380	  Say Y if unsure.
381
382config COMPAT_BRK
383	bool "Disable heap randomization"
384	default y
385	help
386	  Randomizing heap placement makes heap exploits harder, but it
387	  also breaks ancient binaries (including anything libc5 based).
388	  This option changes the bootup default to heap randomization
389	  disabled, and can be overridden at runtime by setting
390	  /proc/sys/kernel/randomize_va_space to 2.
391
392	  On non-ancient distros (post-2000 ones) N is usually a safe choice.
393
394config MMAP_ALLOW_UNINITIALIZED
395	bool "Allow mmapped anonymous memory to be uninitialized"
396	depends on EXPERT && !MMU
397	default n
398	help
399	  Normally, and according to the Linux spec, anonymous memory obtained
400	  from mmap() has its contents cleared before it is passed to
401	  userspace.  Enabling this config option allows you to request that
402	  mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
403	  providing a huge performance boost.  If this option is not enabled,
404	  then the flag will be ignored.
405
406	  This is taken advantage of by uClibc's malloc(), and also by
407	  ELF-FDPIC binfmt's brk and stack allocator.
408
409	  Because of the obvious security issues, this option should only be
410	  enabled on embedded devices where you control what is run in
411	  userspace.  Since that isn't generally a problem on no-MMU systems,
412	  it is normally safe to say Y here.
413
414	  See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
415
416config SELECT_MEMORY_MODEL
417	def_bool y
418	depends on ARCH_SELECT_MEMORY_MODEL
419
420choice
421	prompt "Memory model"
422	depends on SELECT_MEMORY_MODEL
423	default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
424	default FLATMEM_MANUAL
425	help
426	  This option allows you to change some of the ways that
427	  Linux manages its memory internally. Most users will
428	  only have one option here selected by the architecture
429	  configuration. This is normal.
430
431config FLATMEM_MANUAL
432	bool "Flat Memory"
433	depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE
434	help
435	  This option is best suited for non-NUMA systems with
436	  flat address space. The FLATMEM is the most efficient
437	  system in terms of performance and resource consumption
438	  and it is the best option for smaller systems.
439
440	  For systems that have holes in their physical address
441	  spaces and for features like NUMA and memory hotplug,
442	  choose "Sparse Memory".
443
444	  If unsure, choose this option (Flat Memory) over any other.
445
446config SPARSEMEM_MANUAL
447	bool "Sparse Memory"
448	depends on ARCH_SPARSEMEM_ENABLE
449	help
450	  This will be the only option for some systems, including
451	  memory hot-plug systems.  This is normal.
452
453	  This option provides efficient support for systems with
454	  holes is their physical address space and allows memory
455	  hot-plug and hot-remove.
456
457	  If unsure, choose "Flat Memory" over this option.
458
459endchoice
460
461config SPARSEMEM
462	def_bool y
463	depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
464
465config FLATMEM
466	def_bool y
467	depends on !SPARSEMEM || FLATMEM_MANUAL
468
469#
470# SPARSEMEM_EXTREME (which is the default) does some bootmem
471# allocations when sparse_init() is called.  If this cannot
472# be done on your architecture, select this option.  However,
473# statically allocating the mem_section[] array can potentially
474# consume vast quantities of .bss, so be careful.
475#
476# This option will also potentially produce smaller runtime code
477# with gcc 3.4 and later.
478#
479config SPARSEMEM_STATIC
480	bool
481
482#
483# Architecture platforms which require a two level mem_section in SPARSEMEM
484# must select this option. This is usually for architecture platforms with
485# an extremely sparse physical address space.
486#
487config SPARSEMEM_EXTREME
488	def_bool y
489	depends on SPARSEMEM && !SPARSEMEM_STATIC
490
491config SPARSEMEM_VMEMMAP_ENABLE
492	bool
493
494config SPARSEMEM_VMEMMAP
495	bool "Sparse Memory virtual memmap"
496	depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
497	default y
498	help
499	  SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
500	  pfn_to_page and page_to_pfn operations.  This is the most
501	  efficient option when sufficient kernel resources are available.
502#
503# Select this config option from the architecture Kconfig, if it is preferred
504# to enable the feature of HugeTLB/dev_dax vmemmap optimization.
505#
506config ARCH_WANT_OPTIMIZE_DAX_VMEMMAP
507	bool
508
509config ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP
510	bool
511
512config HAVE_MEMBLOCK_PHYS_MAP
513	bool
514
515config HAVE_FAST_GUP
516	depends on MMU
517	bool
518
519# Don't discard allocated memory used to track "memory" and "reserved" memblocks
520# after early boot, so it can still be used to test for validity of memory.
521# Also, memblocks are updated with memory hot(un)plug.
522config ARCH_KEEP_MEMBLOCK
523	bool
524
525# Keep arch NUMA mapping infrastructure post-init.
526config NUMA_KEEP_MEMINFO
527	bool
528
529config MEMORY_ISOLATION
530	bool
531
532# IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked
533# IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via
534# /dev/mem.
535config EXCLUSIVE_SYSTEM_RAM
536	def_bool y
537	depends on !DEVMEM || STRICT_DEVMEM
538
539#
540# Only be set on architectures that have completely implemented memory hotplug
541# feature. If you are not sure, don't touch it.
542#
543config HAVE_BOOTMEM_INFO_NODE
544	def_bool n
545
546config ARCH_ENABLE_MEMORY_HOTPLUG
547	bool
548
549config ARCH_ENABLE_MEMORY_HOTREMOVE
550	bool
551
552# eventually, we can have this option just 'select SPARSEMEM'
553menuconfig MEMORY_HOTPLUG
554	bool "Memory hotplug"
555	select MEMORY_ISOLATION
556	depends on SPARSEMEM
557	depends on ARCH_ENABLE_MEMORY_HOTPLUG
558	depends on 64BIT
559	select NUMA_KEEP_MEMINFO if NUMA
560
561if MEMORY_HOTPLUG
562
563config MEMORY_HOTPLUG_DEFAULT_ONLINE
564	bool "Online the newly added memory blocks by default"
565	depends on MEMORY_HOTPLUG
566	help
567	  This option sets the default policy setting for memory hotplug
568	  onlining policy (/sys/devices/system/memory/auto_online_blocks) which
569	  determines what happens to newly added memory regions. Policy setting
570	  can always be changed at runtime.
571	  See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
572
573	  Say Y here if you want all hot-plugged memory blocks to appear in
574	  'online' state by default.
575	  Say N here if you want the default policy to keep all hot-plugged
576	  memory blocks in 'offline' state.
577
578config MEMORY_HOTREMOVE
579	bool "Allow for memory hot remove"
580	select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
581	depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
582	depends on MIGRATION
583
584config MHP_MEMMAP_ON_MEMORY
585	def_bool y
586	depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
587	depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
588
589endif # MEMORY_HOTPLUG
590
591config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
592       bool
593
594# Heavily threaded applications may benefit from splitting the mm-wide
595# page_table_lock, so that faults on different parts of the user address
596# space can be handled with less contention: split it at this NR_CPUS.
597# Default to 4 for wider testing, though 8 might be more appropriate.
598# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
599# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
600# SPARC32 allocates multiple pte tables within a single page, and therefore
601# a per-page lock leads to problems when multiple tables need to be locked
602# at the same time (e.g. copy_page_range()).
603# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
604#
605config SPLIT_PTLOCK_CPUS
606	int
607	default "999999" if !MMU
608	default "999999" if ARM && !CPU_CACHE_VIPT
609	default "999999" if PARISC && !PA20
610	default "999999" if SPARC32
611	default "4"
612
613config ARCH_ENABLE_SPLIT_PMD_PTLOCK
614	bool
615
616#
617# support for memory balloon
618config MEMORY_BALLOON
619	bool
620
621#
622# support for memory balloon compaction
623config BALLOON_COMPACTION
624	bool "Allow for balloon memory compaction/migration"
625	def_bool y
626	depends on COMPACTION && MEMORY_BALLOON
627	help
628	  Memory fragmentation introduced by ballooning might reduce
629	  significantly the number of 2MB contiguous memory blocks that can be
630	  used within a guest, thus imposing performance penalties associated
631	  with the reduced number of transparent huge pages that could be used
632	  by the guest workload. Allowing the compaction & migration for memory
633	  pages enlisted as being part of memory balloon devices avoids the
634	  scenario aforementioned and helps improving memory defragmentation.
635
636#
637# support for memory compaction
638config COMPACTION
639	bool "Allow for memory compaction"
640	def_bool y
641	select MIGRATION
642	depends on MMU
643	help
644	  Compaction is the only memory management component to form
645	  high order (larger physically contiguous) memory blocks
646	  reliably. The page allocator relies on compaction heavily and
647	  the lack of the feature can lead to unexpected OOM killer
648	  invocations for high order memory requests. You shouldn't
649	  disable this option unless there really is a strong reason for
650	  it and then we would be really interested to hear about that at
651	  linux-mm@kvack.org.
652
653config COMPACT_UNEVICTABLE_DEFAULT
654	int
655	depends on COMPACTION
656	default 0 if PREEMPT_RT
657	default 1
658
659#
660# support for free page reporting
661config PAGE_REPORTING
662	bool "Free page reporting"
663	def_bool n
664	help
665	  Free page reporting allows for the incremental acquisition of
666	  free pages from the buddy allocator for the purpose of reporting
667	  those pages to another entity, such as a hypervisor, so that the
668	  memory can be freed within the host for other uses.
669
670#
671# support for page migration
672#
673config MIGRATION
674	bool "Page migration"
675	def_bool y
676	depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
677	help
678	  Allows the migration of the physical location of pages of processes
679	  while the virtual addresses are not changed. This is useful in
680	  two situations. The first is on NUMA systems to put pages nearer
681	  to the processors accessing. The second is when allocating huge
682	  pages as migration can relocate pages to satisfy a huge page
683	  allocation instead of reclaiming.
684
685config DEVICE_MIGRATION
686	def_bool MIGRATION && ZONE_DEVICE
687
688config ARCH_ENABLE_HUGEPAGE_MIGRATION
689	bool
690
691config ARCH_ENABLE_THP_MIGRATION
692	bool
693
694config HUGETLB_PAGE_SIZE_VARIABLE
695	def_bool n
696	help
697	  Allows the pageblock_order value to be dynamic instead of just standard
698	  HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available
699	  on a platform.
700
701	  Note that the pageblock_order cannot exceed MAX_ORDER and will be
702	  clamped down to MAX_ORDER.
703
704config CONTIG_ALLOC
705	def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
706
707config PHYS_ADDR_T_64BIT
708	def_bool 64BIT
709
710config BOUNCE
711	bool "Enable bounce buffers"
712	default y
713	depends on BLOCK && MMU && HIGHMEM
714	help
715	  Enable bounce buffers for devices that cannot access the full range of
716	  memory available to the CPU. Enabled by default when HIGHMEM is
717	  selected, but you may say n to override this.
718
719config MMU_NOTIFIER
720	bool
721	select INTERVAL_TREE
722
723config KSM
724	bool "Enable KSM for page merging"
725	depends on MMU
726	select XXHASH
727	help
728	  Enable Kernel Samepage Merging: KSM periodically scans those areas
729	  of an application's address space that an app has advised may be
730	  mergeable.  When it finds pages of identical content, it replaces
731	  the many instances by a single page with that content, so
732	  saving memory until one or another app needs to modify the content.
733	  Recommended for use with KVM, or with other duplicative applications.
734	  See Documentation/mm/ksm.rst for more information: KSM is inactive
735	  until a program has madvised that an area is MADV_MERGEABLE, and
736	  root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
737
738config DEFAULT_MMAP_MIN_ADDR
739	int "Low address space to protect from user allocation"
740	depends on MMU
741	default 4096
742	help
743	  This is the portion of low virtual memory which should be protected
744	  from userspace allocation.  Keeping a user from writing to low pages
745	  can help reduce the impact of kernel NULL pointer bugs.
746
747	  For most ia64, ppc64 and x86 users with lots of address space
748	  a value of 65536 is reasonable and should cause no problems.
749	  On arm and other archs it should not be higher than 32768.
750	  Programs which use vm86 functionality or have some need to map
751	  this low address space will need CAP_SYS_RAWIO or disable this
752	  protection by setting the value to 0.
753
754	  This value can be changed after boot using the
755	  /proc/sys/vm/mmap_min_addr tunable.
756
757config ARCH_SUPPORTS_MEMORY_FAILURE
758	bool
759
760config MEMORY_FAILURE
761	depends on MMU
762	depends on ARCH_SUPPORTS_MEMORY_FAILURE
763	bool "Enable recovery from hardware memory errors"
764	select MEMORY_ISOLATION
765	select RAS
766	help
767	  Enables code to recover from some memory failures on systems
768	  with MCA recovery. This allows a system to continue running
769	  even when some of its memory has uncorrected errors. This requires
770	  special hardware support and typically ECC memory.
771
772config HWPOISON_INJECT
773	tristate "HWPoison pages injector"
774	depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
775	select PROC_PAGE_MONITOR
776
777config NOMMU_INITIAL_TRIM_EXCESS
778	int "Turn on mmap() excess space trimming before booting"
779	depends on !MMU
780	default 1
781	help
782	  The NOMMU mmap() frequently needs to allocate large contiguous chunks
783	  of memory on which to store mappings, but it can only ask the system
784	  allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
785	  more than it requires.  To deal with this, mmap() is able to trim off
786	  the excess and return it to the allocator.
787
788	  If trimming is enabled, the excess is trimmed off and returned to the
789	  system allocator, which can cause extra fragmentation, particularly
790	  if there are a lot of transient processes.
791
792	  If trimming is disabled, the excess is kept, but not used, which for
793	  long-term mappings means that the space is wasted.
794
795	  Trimming can be dynamically controlled through a sysctl option
796	  (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
797	  excess pages there must be before trimming should occur, or zero if
798	  no trimming is to occur.
799
800	  This option specifies the initial value of this option.  The default
801	  of 1 says that all excess pages should be trimmed.
802
803	  See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
804
805config ARCH_WANT_GENERAL_HUGETLB
806	bool
807
808config ARCH_WANTS_THP_SWAP
809	def_bool n
810
811menuconfig TRANSPARENT_HUGEPAGE
812	bool "Transparent Hugepage Support"
813	depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT
814	select COMPACTION
815	select XARRAY_MULTI
816	help
817	  Transparent Hugepages allows the kernel to use huge pages and
818	  huge tlb transparently to the applications whenever possible.
819	  This feature can improve computing performance to certain
820	  applications by speeding up page faults during memory
821	  allocation, by reducing the number of tlb misses and by speeding
822	  up the pagetable walking.
823
824	  If memory constrained on embedded, you may want to say N.
825
826if TRANSPARENT_HUGEPAGE
827
828choice
829	prompt "Transparent Hugepage Support sysfs defaults"
830	depends on TRANSPARENT_HUGEPAGE
831	default TRANSPARENT_HUGEPAGE_ALWAYS
832	help
833	  Selects the sysfs defaults for Transparent Hugepage Support.
834
835	config TRANSPARENT_HUGEPAGE_ALWAYS
836		bool "always"
837	help
838	  Enabling Transparent Hugepage always, can increase the
839	  memory footprint of applications without a guaranteed
840	  benefit but it will work automatically for all applications.
841
842	config TRANSPARENT_HUGEPAGE_MADVISE
843		bool "madvise"
844	help
845	  Enabling Transparent Hugepage madvise, will only provide a
846	  performance improvement benefit to the applications using
847	  madvise(MADV_HUGEPAGE) but it won't risk to increase the
848	  memory footprint of applications without a guaranteed
849	  benefit.
850endchoice
851
852config THP_SWAP
853	def_bool y
854	depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT
855	help
856	  Swap transparent huge pages in one piece, without splitting.
857	  XXX: For now, swap cluster backing transparent huge page
858	  will be split after swapout.
859
860	  For selection by architectures with reasonable THP sizes.
861
862config READ_ONLY_THP_FOR_FS
863	bool "Read-only THP for filesystems (EXPERIMENTAL)"
864	depends on TRANSPARENT_HUGEPAGE && SHMEM
865
866	help
867	  Allow khugepaged to put read-only file-backed pages in THP.
868
869	  This is marked experimental because it is a new feature. Write
870	  support of file THPs will be developed in the next few release
871	  cycles.
872
873endif # TRANSPARENT_HUGEPAGE
874
875#
876# UP and nommu archs use km based percpu allocator
877#
878config NEED_PER_CPU_KM
879	depends on !SMP || !MMU
880	bool
881	default y
882
883config NEED_PER_CPU_EMBED_FIRST_CHUNK
884	bool
885
886config NEED_PER_CPU_PAGE_FIRST_CHUNK
887	bool
888
889config USE_PERCPU_NUMA_NODE_ID
890	bool
891
892config HAVE_SETUP_PER_CPU_AREA
893	bool
894
895config CMA
896	bool "Contiguous Memory Allocator"
897	depends on MMU
898	select MIGRATION
899	select MEMORY_ISOLATION
900	help
901	  This enables the Contiguous Memory Allocator which allows other
902	  subsystems to allocate big physically-contiguous blocks of memory.
903	  CMA reserves a region of memory and allows only movable pages to
904	  be allocated from it. This way, the kernel can use the memory for
905	  pagecache and when a subsystem requests for contiguous area, the
906	  allocated pages are migrated away to serve the contiguous request.
907
908	  If unsure, say "n".
909
910config CMA_DEBUG
911	bool "CMA debug messages (DEVELOPMENT)"
912	depends on DEBUG_KERNEL && CMA
913	help
914	  Turns on debug messages in CMA.  This produces KERN_DEBUG
915	  messages for every CMA call as well as various messages while
916	  processing calls such as dma_alloc_from_contiguous().
917	  This option does not affect warning and error messages.
918
919config CMA_DEBUGFS
920	bool "CMA debugfs interface"
921	depends on CMA && DEBUG_FS
922	help
923	  Turns on the DebugFS interface for CMA.
924
925config CMA_SYSFS
926	bool "CMA information through sysfs interface"
927	depends on CMA && SYSFS
928	help
929	  This option exposes some sysfs attributes to get information
930	  from CMA.
931
932config CMA_AREAS
933	int "Maximum count of the CMA areas"
934	depends on CMA
935	default 19 if NUMA
936	default 7
937	help
938	  CMA allows to create CMA areas for particular purpose, mainly,
939	  used as device private area. This parameter sets the maximum
940	  number of CMA area in the system.
941
942	  If unsure, leave the default value "7" in UMA and "19" in NUMA.
943
944config MEM_SOFT_DIRTY
945	bool "Track memory changes"
946	depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
947	select PROC_PAGE_MONITOR
948	help
949	  This option enables memory changes tracking by introducing a
950	  soft-dirty bit on pte-s. This bit it set when someone writes
951	  into a page just as regular dirty bit, but unlike the latter
952	  it can be cleared by hands.
953
954	  See Documentation/admin-guide/mm/soft-dirty.rst for more details.
955
956config GENERIC_EARLY_IOREMAP
957	bool
958
959config STACK_MAX_DEFAULT_SIZE_MB
960	int "Default maximum user stack size for 32-bit processes (MB)"
961	default 100
962	range 8 2048
963	depends on STACK_GROWSUP && (!64BIT || COMPAT)
964	help
965	  This is the maximum stack size in Megabytes in the VM layout of 32-bit
966	  user processes when the stack grows upwards (currently only on parisc
967	  arch) when the RLIMIT_STACK hard limit is unlimited.
968
969	  A sane initial value is 100 MB.
970
971config DEFERRED_STRUCT_PAGE_INIT
972	bool "Defer initialisation of struct pages to kthreads"
973	depends on SPARSEMEM
974	depends on !NEED_PER_CPU_KM
975	depends on 64BIT
976	select PADATA
977	help
978	  Ordinarily all struct pages are initialised during early boot in a
979	  single thread. On very large machines this can take a considerable
980	  amount of time. If this option is set, large machines will bring up
981	  a subset of memmap at boot and then initialise the rest in parallel.
982	  This has a potential performance impact on tasks running early in the
983	  lifetime of the system until these kthreads finish the
984	  initialisation.
985
986config PAGE_IDLE_FLAG
987	bool
988	select PAGE_EXTENSION if !64BIT
989	help
990	  This adds PG_idle and PG_young flags to 'struct page'.  PTE Accessed
991	  bit writers can set the state of the bit in the flags so that PTE
992	  Accessed bit readers may avoid disturbance.
993
994config IDLE_PAGE_TRACKING
995	bool "Enable idle page tracking"
996	depends on SYSFS && MMU
997	select PAGE_IDLE_FLAG
998	help
999	  This feature allows to estimate the amount of user pages that have
1000	  not been touched during a given period of time. This information can
1001	  be useful to tune memory cgroup limits and/or for job placement
1002	  within a compute cluster.
1003
1004	  See Documentation/admin-guide/mm/idle_page_tracking.rst for
1005	  more details.
1006
1007config ARCH_HAS_CACHE_LINE_SIZE
1008	bool
1009
1010config ARCH_HAS_CURRENT_STACK_POINTER
1011	bool
1012	help
1013	  In support of HARDENED_USERCOPY performing stack variable lifetime
1014	  checking, an architecture-agnostic way to find the stack pointer
1015	  is needed. Once an architecture defines an unsigned long global
1016	  register alias named "current_stack_pointer", this config can be
1017	  selected.
1018
1019config ARCH_HAS_PTE_DEVMAP
1020	bool
1021
1022config ARCH_HAS_ZONE_DMA_SET
1023	bool
1024
1025config ZONE_DMA
1026	bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET
1027	default y if ARM64 || X86
1028
1029config ZONE_DMA32
1030	bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET
1031	depends on !X86_32
1032	default y if ARM64
1033
1034config ZONE_DEVICE
1035	bool "Device memory (pmem, HMM, etc...) hotplug support"
1036	depends on MEMORY_HOTPLUG
1037	depends on MEMORY_HOTREMOVE
1038	depends on SPARSEMEM_VMEMMAP
1039	depends on ARCH_HAS_PTE_DEVMAP
1040	select XARRAY_MULTI
1041
1042	help
1043	  Device memory hotplug support allows for establishing pmem,
1044	  or other device driver discovered memory regions, in the
1045	  memmap. This allows pfn_to_page() lookups of otherwise
1046	  "device-physical" addresses which is needed for using a DAX
1047	  mapping in an O_DIRECT operation, among other things.
1048
1049	  If FS_DAX is enabled, then say Y.
1050
1051#
1052# Helpers to mirror range of the CPU page tables of a process into device page
1053# tables.
1054#
1055config HMM_MIRROR
1056	bool
1057	depends on MMU
1058
1059config GET_FREE_REGION
1060	depends on SPARSEMEM
1061	bool
1062
1063config DEVICE_PRIVATE
1064	bool "Unaddressable device memory (GPU memory, ...)"
1065	depends on ZONE_DEVICE
1066	select GET_FREE_REGION
1067
1068	help
1069	  Allows creation of struct pages to represent unaddressable device
1070	  memory; i.e., memory that is only accessible from the device (or
1071	  group of devices). You likely also want to select HMM_MIRROR.
1072
1073config VMAP_PFN
1074	bool
1075
1076config ARCH_USES_HIGH_VMA_FLAGS
1077	bool
1078config ARCH_HAS_PKEYS
1079	bool
1080
1081config ARCH_USES_PG_ARCH_X
1082	bool
1083	help
1084	  Enable the definition of PG_arch_x page flags with x > 1. Only
1085	  suitable for 64-bit architectures with CONFIG_FLATMEM or
1086	  CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be
1087	  enough room for additional bits in page->flags.
1088
1089config VM_EVENT_COUNTERS
1090	default y
1091	bool "Enable VM event counters for /proc/vmstat" if EXPERT
1092	help
1093	  VM event counters are needed for event counts to be shown.
1094	  This option allows the disabling of the VM event counters
1095	  on EXPERT systems.  /proc/vmstat will only show page counts
1096	  if VM event counters are disabled.
1097
1098config PERCPU_STATS
1099	bool "Collect percpu memory statistics"
1100	help
1101	  This feature collects and exposes statistics via debugfs. The
1102	  information includes global and per chunk statistics, which can
1103	  be used to help understand percpu memory usage.
1104
1105config GUP_TEST
1106	bool "Enable infrastructure for get_user_pages()-related unit tests"
1107	depends on DEBUG_FS
1108	help
1109	  Provides /sys/kernel/debug/gup_test, which in turn provides a way
1110	  to make ioctl calls that can launch kernel-based unit tests for
1111	  the get_user_pages*() and pin_user_pages*() family of API calls.
1112
1113	  These tests include benchmark testing of the _fast variants of
1114	  get_user_pages*() and pin_user_pages*(), as well as smoke tests of
1115	  the non-_fast variants.
1116
1117	  There is also a sub-test that allows running dump_page() on any
1118	  of up to eight pages (selected by command line args) within the
1119	  range of user-space addresses. These pages are either pinned via
1120	  pin_user_pages*(), or pinned via get_user_pages*(), as specified
1121	  by other command line arguments.
1122
1123	  See tools/testing/selftests/mm/gup_test.c
1124
1125comment "GUP_TEST needs to have DEBUG_FS enabled"
1126	depends on !GUP_TEST && !DEBUG_FS
1127
1128config GUP_GET_PXX_LOW_HIGH
1129	bool
1130
1131config DMAPOOL_TEST
1132	tristate "Enable a module to run time tests on dma_pool"
1133	depends on HAS_DMA
1134	help
1135	  Provides a test module that will allocate and free many blocks of
1136	  various sizes and report how long it takes. This is intended to
1137	  provide a consistent way to measure how changes to the
1138	  dma_pool_alloc/free routines affect performance.
1139
1140config ARCH_HAS_PTE_SPECIAL
1141	bool
1142
1143#
1144# Some architectures require a special hugepage directory format that is
1145# required to support multiple hugepage sizes. For example a4fe3ce76
1146# "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
1147# introduced it on powerpc.  This allows for a more flexible hugepage
1148# pagetable layouts.
1149#
1150config ARCH_HAS_HUGEPD
1151	bool
1152
1153config MAPPING_DIRTY_HELPERS
1154        bool
1155
1156config KMAP_LOCAL
1157	bool
1158
1159config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY
1160	bool
1161
1162# struct io_mapping based helper.  Selected by drivers that need them
1163config IO_MAPPING
1164	bool
1165
1166config MEMFD_CREATE
1167	bool "Enable memfd_create() system call" if EXPERT
1168
1169config SECRETMEM
1170	default y
1171	bool "Enable memfd_secret() system call" if EXPERT
1172	depends on ARCH_HAS_SET_DIRECT_MAP
1173	help
1174	  Enable the memfd_secret() system call with the ability to create
1175	  memory areas visible only in the context of the owning process and
1176	  not mapped to other processes and other kernel page tables.
1177
1178config ANON_VMA_NAME
1179	bool "Anonymous VMA name support"
1180	depends on PROC_FS && ADVISE_SYSCALLS && MMU
1181
1182	help
1183	  Allow naming anonymous virtual memory areas.
1184
1185	  This feature allows assigning names to virtual memory areas. Assigned
1186	  names can be later retrieved from /proc/pid/maps and /proc/pid/smaps
1187	  and help identifying individual anonymous memory areas.
1188	  Assigning a name to anonymous virtual memory area might prevent that
1189	  area from being merged with adjacent virtual memory areas due to the
1190	  difference in their name.
1191
1192config USERFAULTFD
1193	bool "Enable userfaultfd() system call"
1194	depends on MMU
1195	help
1196	  Enable the userfaultfd() system call that allows to intercept and
1197	  handle page faults in userland.
1198
1199config HAVE_ARCH_USERFAULTFD_WP
1200	bool
1201	help
1202	  Arch has userfaultfd write protection support
1203
1204config HAVE_ARCH_USERFAULTFD_MINOR
1205	bool
1206	help
1207	  Arch has userfaultfd minor fault support
1208
1209config PTE_MARKER_UFFD_WP
1210	bool "Userfaultfd write protection support for shmem/hugetlbfs"
1211	default y
1212	depends on HAVE_ARCH_USERFAULTFD_WP
1213
1214	help
1215	  Allows to create marker PTEs for userfaultfd write protection
1216	  purposes.  It is required to enable userfaultfd write protection on
1217	  file-backed memory types like shmem and hugetlbfs.
1218
1219# multi-gen LRU {
1220config LRU_GEN
1221	bool "Multi-Gen LRU"
1222	depends on MMU
1223	# make sure folio->flags has enough spare bits
1224	depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP
1225	help
1226	  A high performance LRU implementation to overcommit memory. See
1227	  Documentation/admin-guide/mm/multigen_lru.rst for details.
1228
1229config LRU_GEN_ENABLED
1230	bool "Enable by default"
1231	depends on LRU_GEN
1232	help
1233	  This option enables the multi-gen LRU by default.
1234
1235config LRU_GEN_STATS
1236	bool "Full stats for debugging"
1237	depends on LRU_GEN
1238	help
1239	  Do not enable this option unless you plan to look at historical stats
1240	  from evicted generations for debugging purpose.
1241
1242	  This option has a per-memcg and per-node memory overhead.
1243# }
1244
1245config ARCH_SUPPORTS_PER_VMA_LOCK
1246       def_bool n
1247
1248config PER_VMA_LOCK
1249	def_bool y
1250	depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP
1251	help
1252	  Allow per-vma locking during page fault handling.
1253
1254	  This feature allows locking each virtual memory area separately when
1255	  handling page faults instead of taking mmap_lock.
1256
1257config LOCK_MM_AND_FIND_VMA
1258	bool
1259	depends on !STACK_GROWSUP
1260
1261source "mm/damon/Kconfig"
1262
1263endmenu
1264