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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
91#
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.
97#
98# This option will also potentially produce smaller runtime code
99# with gcc 3.4 and later.
100#
101config SPARSEMEM_STATIC
102 bool
103
104#
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.
108#
109config SPARSEMEM_EXTREME
110 def_bool y
111 depends on SPARSEMEM && !SPARSEMEM_STATIC
112
113config SPARSEMEM_VMEMMAP_ENABLE
114 bool
115
116config SPARSEMEM_VMEMMAP
117 bool "Sparse Memory virtual memmap"
118 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
119 default y
120 help
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.
124
125config HAVE_MEMBLOCK_PHYS_MAP
126 bool
127
128config HAVE_FAST_GUP
129 depends on MMU
130 bool
131
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.
135config ARCH_KEEP_MEMBLOCK
136 bool
137
138# Keep arch NUMA mapping infrastructure post-init.
139config NUMA_KEEP_MEMINFO
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 depends on 64BIT || BROKEN
158 select NUMA_KEEP_MEMINFO if NUMA
159
160config MEMORY_HOTPLUG_SPARSE
161 def_bool y
162 depends on SPARSEMEM && MEMORY_HOTPLUG
163
164config MEMORY_HOTPLUG_DEFAULT_ONLINE
165 bool "Online the newly added memory blocks by default"
166 depends on MEMORY_HOTPLUG
167 help
168 This option sets the default policy setting for memory hotplug
169 onlining policy (/sys/devices/system/memory/auto_online_blocks) which
170 determines what happens to newly added memory regions. Policy setting
171 can always be changed at runtime.
172 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
173
174 Say Y here if you want all hot-plugged memory blocks to appear in
175 'online' state by default.
176 Say N here if you want the default policy to keep all hot-plugged
177 memory blocks in 'offline' state.
178
179config MEMORY_HOTREMOVE
180 bool "Allow for memory hot remove"
181 select MEMORY_ISOLATION
182 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
183 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
184 depends on MIGRATION
185
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.
196#
197config SPLIT_PTLOCK_CPUS
198 int
199 default "999999" if !MMU
200 default "999999" if ARM && !CPU_CACHE_VIPT
201 default "999999" if PARISC && !PA20
202 default "999999" if SPARC32
203 default "4"
204
205config ARCH_ENABLE_SPLIT_PMD_PTLOCK
206 bool
207
208#
209# support for memory balloon
210config MEMORY_BALLOON
211 bool
212
213#
214# support for memory balloon compaction
215config BALLOON_COMPACTION
216 bool "Allow for balloon memory compaction/migration"
217 def_bool y
218 depends on COMPACTION && MEMORY_BALLOON
219 help
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.
227
228#
229# support for memory compaction
230config COMPACTION
231 bool "Allow for memory compaction"
232 def_bool y
233 select MIGRATION
234 depends on MMU
235 help
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
243 linux-mm@kvack.org.
244
245#
246# support for free page reporting
247config PAGE_REPORTING
248 bool "Free page reporting"
249 def_bool n
250 help
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.
255
256#
257# support for page migration
258#
259config MIGRATION
260 bool "Page migration"
261 def_bool y
262 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
263 help
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.
270
271config ARCH_ENABLE_HUGEPAGE_MIGRATION
272 bool
273
274config ARCH_ENABLE_THP_MIGRATION
275 bool
276
277config CONTIG_ALLOC
278 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
279
280config PHYS_ADDR_T_64BIT
281 def_bool 64BIT
282
283config BOUNCE
284 bool "Enable bounce buffers"
285 default y
286 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
287 help
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.
292
293config VIRT_TO_BUS
294 bool
295 help
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.
299
300
301config MMU_NOTIFIER
302 bool
303 select SRCU
304 select INTERVAL_TREE
305
306config KSM
307 bool "Enable KSM for page merging"
308 depends on MMU
309 select XXHASH
310 help
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).
320
321config DEFAULT_MMAP_MIN_ADDR
322 int "Low address space to protect from user allocation"
323 depends on MMU
324 default 4096
325 help
326 This is the portion of low virtual memory which should be protected
327 from userspace allocation. Keeping a user from writing to low pages
328 can help reduce the impact of kernel NULL pointer bugs.
329
330 For most ia64, ppc64 and x86 users with lots of address space
331 a value of 65536 is reasonable and should cause no problems.
332 On arm and other archs it should not be higher than 32768.
333 Programs which use vm86 functionality or have some need to map
334 this low address space will need CAP_SYS_RAWIO or disable this
335 protection by setting the value to 0.
336
337 This value can be changed after boot using the
338 /proc/sys/vm/mmap_min_addr tunable.
339
340config ARCH_SUPPORTS_MEMORY_FAILURE
341 bool
342
343config MEMORY_FAILURE
344 depends on MMU
345 depends on ARCH_SUPPORTS_MEMORY_FAILURE
346 bool "Enable recovery from hardware memory errors"
347 select MEMORY_ISOLATION
348 select RAS
349 help
350 Enables code to recover from some memory failures on systems
351 with MCA recovery. This allows a system to continue running
352 even when some of its memory has uncorrected errors. This requires
353 special hardware support and typically ECC memory.
354
355config HWPOISON_INJECT
356 tristate "HWPoison pages injector"
357 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
358 select PROC_PAGE_MONITOR
359
360config NOMMU_INITIAL_TRIM_EXCESS
361 int "Turn on mmap() excess space trimming before booting"
362 depends on !MMU
363 default 1
364 help
365 The NOMMU mmap() frequently needs to allocate large contiguous chunks
366 of memory on which to store mappings, but it can only ask the system
367 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
368 more than it requires. To deal with this, mmap() is able to trim off
369 the excess and return it to the allocator.
370
371 If trimming is enabled, the excess is trimmed off and returned to the
372 system allocator, which can cause extra fragmentation, particularly
373 if there are a lot of transient processes.
374
375 If trimming is disabled, the excess is kept, but not used, which for
376 long-term mappings means that the space is wasted.
377
378 Trimming can be dynamically controlled through a sysctl option
379 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
380 excess pages there must be before trimming should occur, or zero if
381 no trimming is to occur.
382
383 This option specifies the initial value of this option. The default
384 of 1 says that all excess pages should be trimmed.
385
386 See Documentation/mm/nommu-mmap.rst for more information.
387
388config TRANSPARENT_HUGEPAGE
389 bool "Transparent Hugepage Support"
390 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
391 select COMPACTION
392 select XARRAY_MULTI
393 help
394 Transparent Hugepages allows the kernel to use huge pages and
395 huge tlb transparently to the applications whenever possible.
396 This feature can improve computing performance to certain
397 applications by speeding up page faults during memory
398 allocation, by reducing the number of tlb misses and by speeding
399 up the pagetable walking.
400
401 If memory constrained on embedded, you may want to say N.
402
403choice
404 prompt "Transparent Hugepage Support sysfs defaults"
405 depends on TRANSPARENT_HUGEPAGE
406 default TRANSPARENT_HUGEPAGE_ALWAYS
407 help
408 Selects the sysfs defaults for Transparent Hugepage Support.
409
410 config TRANSPARENT_HUGEPAGE_ALWAYS
411 bool "always"
412 help
413 Enabling Transparent Hugepage always, can increase the
414 memory footprint of applications without a guaranteed
415 benefit but it will work automatically for all applications.
416
417 config TRANSPARENT_HUGEPAGE_MADVISE
418 bool "madvise"
419 help
420 Enabling Transparent Hugepage madvise, will only provide a
421 performance improvement benefit to the applications using
422 madvise(MADV_HUGEPAGE) but it won't risk to increase the
423 memory footprint of applications without a guaranteed
424 benefit.
425endchoice
426
427config ARCH_WANTS_THP_SWAP
428 def_bool n
429
430config THP_SWAP
431 def_bool y
432 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
433 help
434 Swap transparent huge pages in one piece, without splitting.
435 XXX: For now, swap cluster backing transparent huge page
436 will be split after swapout.
437
438 For selection by architectures with reasonable THP sizes.
439
440#
441# UP and nommu archs use km based percpu allocator
442#
443config NEED_PER_CPU_KM
444 depends on !SMP
445 bool
446 default y
447
448config CLEANCACHE
449 bool "Enable cleancache driver to cache clean pages if tmem is present"
450 help
451 Cleancache can be thought of as a page-granularity victim cache
452 for clean pages that the kernel's pageframe replacement algorithm
453 (PFRA) would like to keep around, but can't since there isn't enough
454 memory. So when the PFRA "evicts" a page, it first attempts to use
455 cleancache code to put the data contained in that page into
456 "transcendent memory", memory that is not directly accessible or
457 addressable by the kernel and is of unknown and possibly
458 time-varying size. And when a cleancache-enabled
459 filesystem wishes to access a page in a file on disk, it first
460 checks cleancache to see if it already contains it; if it does,
461 the page is copied into the kernel and a disk access is avoided.
462 When a transcendent memory driver is available (such as zcache or
463 Xen transcendent memory), a significant I/O reduction
464 may be achieved. When none is available, all cleancache calls
465 are reduced to a single pointer-compare-against-NULL resulting
466 in a negligible performance hit.
467
468 If unsure, say Y to enable cleancache
469
470config FRONTSWAP
471 bool "Enable frontswap to cache swap pages if tmem is present"
472 depends on SWAP
473 help
474 Frontswap is so named because it can be thought of as the opposite
475 of a "backing" store for a swap device. The data is stored into
476 "transcendent memory", memory that is not directly accessible or
477 addressable by the kernel and is of unknown and possibly
478 time-varying size. When space in transcendent memory is available,
479 a significant swap I/O reduction may be achieved. When none is
480 available, all frontswap calls are reduced to a single pointer-
481 compare-against-NULL resulting in a negligible performance hit
482 and swap data is stored as normal on the matching swap device.
483
484 If unsure, say Y to enable frontswap.
485
486config CMA
487 bool "Contiguous Memory Allocator"
488 depends on MMU
489 select MIGRATION
490 select MEMORY_ISOLATION
491 help
492 This enables the Contiguous Memory Allocator which allows other
493 subsystems to allocate big physically-contiguous blocks of memory.
494 CMA reserves a region of memory and allows only movable pages to
495 be allocated from it. This way, the kernel can use the memory for
496 pagecache and when a subsystem requests for contiguous area, the
497 allocated pages are migrated away to serve the contiguous request.
498
499 If unsure, say "n".
500
501config CMA_DEBUG
502 bool "CMA debug messages (DEVELOPMENT)"
503 depends on DEBUG_KERNEL && CMA
504 help
505 Turns on debug messages in CMA. This produces KERN_DEBUG
506 messages for every CMA call as well as various messages while
507 processing calls such as dma_alloc_from_contiguous().
508 This option does not affect warning and error messages.
509
510config CMA_DEBUGFS
511 bool "CMA debugfs interface"
512 depends on CMA && DEBUG_FS
513 help
514 Turns on the DebugFS interface for CMA.
515
516config CMA_AREAS
517 int "Maximum count of the CMA areas"
518 depends on CMA
519 default 7
520 help
521 CMA allows to create CMA areas for particular purpose, mainly,
522 used as device private area. This parameter sets the maximum
523 number of CMA area in the system.
524
525 If unsure, leave the default value "7".
526
527config MEM_SOFT_DIRTY
528 bool "Track memory changes"
529 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
530 select PROC_PAGE_MONITOR
531 help
532 This option enables memory changes tracking by introducing a
533 soft-dirty bit on pte-s. This bit it set when someone writes
534 into a page just as regular dirty bit, but unlike the latter
535 it can be cleared by hands.
536
537 See Documentation/admin-guide/mm/soft-dirty.rst for more details.
538
539config ZSWAP
540 bool "Compressed cache for swap pages (EXPERIMENTAL)"
541 depends on FRONTSWAP && CRYPTO=y
542 select ZPOOL
543 help
544 A lightweight compressed cache for swap pages. It takes
545 pages that are in the process of being swapped out and attempts to
546 compress them into a dynamically allocated RAM-based memory pool.
547 This can result in a significant I/O reduction on swap device and,
548 in the case where decompressing from RAM is faster that swap device
549 reads, can also improve workload performance.
550
551 This is marked experimental because it is a new feature (as of
552 v3.11) that interacts heavily with memory reclaim. While these
553 interactions don't cause any known issues on simple memory setups,
554 they have not be fully explored on the large set of potential
555 configurations and workloads that exist.
556
557choice
558 prompt "Compressed cache for swap pages default compressor"
559 depends on ZSWAP
560 default ZSWAP_COMPRESSOR_DEFAULT_LZO
561 help
562 Selects the default compression algorithm for the compressed cache
563 for swap pages.
564
565 For an overview what kind of performance can be expected from
566 a particular compression algorithm please refer to the benchmarks
567 available at the following LWN page:
568 https://lwn.net/Articles/751795/
569
570 If in doubt, select 'LZO'.
571
572 The selection made here can be overridden by using the kernel
573 command line 'zswap.compressor=' option.
574
575config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
576 bool "Deflate"
577 select CRYPTO_DEFLATE
578 help
579 Use the Deflate algorithm as the default compression algorithm.
580
581config ZSWAP_COMPRESSOR_DEFAULT_LZO
582 bool "LZO"
583 select CRYPTO_LZO
584 help
585 Use the LZO algorithm as the default compression algorithm.
586
587config ZSWAP_COMPRESSOR_DEFAULT_842
588 bool "842"
589 select CRYPTO_842
590 help
591 Use the 842 algorithm as the default compression algorithm.
592
593config ZSWAP_COMPRESSOR_DEFAULT_LZ4
594 bool "LZ4"
595 select CRYPTO_LZ4
596 help
597 Use the LZ4 algorithm as the default compression algorithm.
598
599config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
600 bool "LZ4HC"
601 select CRYPTO_LZ4HC
602 help
603 Use the LZ4HC algorithm as the default compression algorithm.
604
605config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
606 bool "zstd"
607 select CRYPTO_ZSTD
608 help
609 Use the zstd algorithm as the default compression algorithm.
610endchoice
611
612config ZSWAP_COMPRESSOR_DEFAULT
613 string
614 depends on ZSWAP
615 default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
616 default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
617 default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
618 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
619 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
620 default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
621 default ""
622
623choice
624 prompt "Compressed cache for swap pages default allocator"
625 depends on ZSWAP
626 default ZSWAP_ZPOOL_DEFAULT_ZBUD
627 help
628 Selects the default allocator for the compressed cache for
629 swap pages.
630 The default is 'zbud' for compatibility, however please do
631 read the description of each of the allocators below before
632 making a right choice.
633
634 The selection made here can be overridden by using the kernel
635 command line 'zswap.zpool=' option.
636
637config ZSWAP_ZPOOL_DEFAULT_ZBUD
638 bool "zbud"
639 select ZBUD
640 help
641 Use the zbud allocator as the default allocator.
642
643config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
644 bool "z3fold"
645 select Z3FOLD
646 help
647 Use the z3fold allocator as the default allocator.
648
649config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
650 bool "zsmalloc"
651 select ZSMALLOC
652 help
653 Use the zsmalloc allocator as the default allocator.
654endchoice
655
656config ZSWAP_ZPOOL_DEFAULT
657 string
658 depends on ZSWAP
659 default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
660 default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
661 default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
662 default ""
663
664config ZSWAP_DEFAULT_ON
665 bool "Enable the compressed cache for swap pages by default"
666 depends on ZSWAP
667 help
668 If selected, the compressed cache for swap pages will be enabled
669 at boot, otherwise it will be disabled.
670
671 The selection made here can be overridden by using the kernel
672 command line 'zswap.enabled=' option.
673
674config ZPOOL
675 tristate "Common API for compressed memory storage"
676 help
677 Compressed memory storage API. This allows using either zbud or
678 zsmalloc.
679
680config ZBUD
681 tristate "Low (Up to 2x) density storage for compressed pages"
682 help
683 A special purpose allocator for storing compressed pages.
684 It is designed to store up to two compressed pages per physical
685 page. While this design limits storage density, it has simple and
686 deterministic reclaim properties that make it preferable to a higher
687 density approach when reclaim will be used.
688
689config Z3FOLD
690 tristate "Up to 3x density storage for compressed pages"
691 depends on ZPOOL
692 help
693 A special purpose allocator for storing compressed pages.
694 It is designed to store up to three compressed pages per physical
695 page. It is a ZBUD derivative so the simplicity and determinism are
696 still there.
697
698config ZSMALLOC
699 tristate "Memory allocator for compressed pages"
700 depends on MMU
701 help
702 zsmalloc is a slab-based memory allocator designed to store
703 compressed RAM pages. zsmalloc uses virtual memory mapping
704 in order to reduce fragmentation. However, this results in a
705 non-standard allocator interface where a handle, not a pointer, is
706 returned by an alloc(). This handle must be mapped in order to
707 access the allocated space.
708
709config ZSMALLOC_PGTABLE_MAPPING
710 bool "Use page table mapping to access object in zsmalloc"
711 depends on ZSMALLOC=y
712 help
713 By default, zsmalloc uses a copy-based object mapping method to
714 access allocations that span two pages. However, if a particular
715 architecture (ex, ARM) performs VM mapping faster than copying,
716 then you should select this. This causes zsmalloc to use page table
717 mapping rather than copying for object mapping.
718
719 You can check speed with zsmalloc benchmark:
720 https://github.com/spartacus06/zsmapbench
721
722config ZSMALLOC_STAT
723 bool "Export zsmalloc statistics"
724 depends on ZSMALLOC
725 select DEBUG_FS
726 help
727 This option enables code in the zsmalloc to collect various
728 statistics about whats happening in zsmalloc and exports that
729 information to userspace via debugfs.
730 If unsure, say N.
731
732config GENERIC_EARLY_IOREMAP
733 bool
734
735config MAX_STACK_SIZE_MB
736 int "Maximum user stack size for 32-bit processes (MB)"
737 default 80
738 range 8 2048
739 depends on STACK_GROWSUP && (!64BIT || COMPAT)
740 help
741 This is the maximum stack size in Megabytes in the VM layout of 32-bit
742 user processes when the stack grows upwards (currently only on parisc
743 arch). The stack will be located at the highest memory address minus
744 the given value, unless the RLIMIT_STACK hard limit is changed to a
745 smaller value in which case that is used.
746
747 A sane initial value is 80 MB.
748
749config DEFERRED_STRUCT_PAGE_INIT
750 bool "Defer initialisation of struct pages to kthreads"
751 depends on SPARSEMEM
752 depends on !NEED_PER_CPU_KM
753 depends on 64BIT
754 select PADATA
755 help
756 Ordinarily all struct pages are initialised during early boot in a
757 single thread. On very large machines this can take a considerable
758 amount of time. If this option is set, large machines will bring up
759 a subset of memmap at boot and then initialise the rest in parallel.
760 This has a potential performance impact on tasks running early in the
761 lifetime of the system until these kthreads finish the
762 initialisation.
763
764config IDLE_PAGE_TRACKING
765 bool "Enable idle page tracking"
766 depends on SYSFS && MMU
767 select PAGE_EXTENSION if !64BIT
768 help
769 This feature allows to estimate the amount of user pages that have
770 not been touched during a given period of time. This information can
771 be useful to tune memory cgroup limits and/or for job placement
772 within a compute cluster.
773
774 See Documentation/admin-guide/mm/idle_page_tracking.rst for
775 more details.
776
777config ARCH_HAS_PTE_DEVMAP
778 bool
779
780config ZONE_DEVICE
781 bool "Device memory (pmem, HMM, etc...) hotplug support"
782 depends on MEMORY_HOTPLUG
783 depends on MEMORY_HOTREMOVE
784 depends on SPARSEMEM_VMEMMAP
785 depends on ARCH_HAS_PTE_DEVMAP
786 select XARRAY_MULTI
787
788 help
789 Device memory hotplug support allows for establishing pmem,
790 or other device driver discovered memory regions, in the
791 memmap. This allows pfn_to_page() lookups of otherwise
792 "device-physical" addresses which is needed for using a DAX
793 mapping in an O_DIRECT operation, among other things.
794
795 If FS_DAX is enabled, then say Y.
796
797config DEV_PAGEMAP_OPS
798 bool
799
800#
801# Helpers to mirror range of the CPU page tables of a process into device page
802# tables.
803#
804config HMM_MIRROR
805 bool
806 depends on MMU
807
808config DEVICE_PRIVATE
809 bool "Unaddressable device memory (GPU memory, ...)"
810 depends on ZONE_DEVICE
811 select DEV_PAGEMAP_OPS
812
813 help
814 Allows creation of struct pages to represent unaddressable device
815 memory; i.e., memory that is only accessible from the device (or
816 group of devices). You likely also want to select HMM_MIRROR.
817
818config FRAME_VECTOR
819 bool
820
821config ARCH_USES_HIGH_VMA_FLAGS
822 bool
823config ARCH_HAS_PKEYS
824 bool
825
826config PERCPU_STATS
827 bool "Collect percpu memory statistics"
828 help
829 This feature collects and exposes statistics via debugfs. The
830 information includes global and per chunk statistics, which can
831 be used to help understand percpu memory usage.
832
833config GUP_BENCHMARK
834 bool "Enable infrastructure for get_user_pages_fast() benchmarking"
835 help
836 Provides /sys/kernel/debug/gup_benchmark that helps with testing
837 performance of get_user_pages_fast().
838
839 See tools/testing/selftests/vm/gup_benchmark.c
840
841config GUP_GET_PTE_LOW_HIGH
842 bool
843
844config READ_ONLY_THP_FOR_FS
845 bool "Read-only THP for filesystems (EXPERIMENTAL)"
846 depends on TRANSPARENT_HUGEPAGE && SHMEM
847
848 help
849 Allow khugepaged to put read-only file-backed pages in THP.
850
851 This is marked experimental because it is a new feature. Write
852 support of file THPs will be developed in the next few release
853 cycles.
854
855config ARCH_HAS_PTE_SPECIAL
856 bool
857
858#
859# Some architectures require a special hugepage directory format that is
860# required to support multiple hugepage sizes. For example a4fe3ce76
861# "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
862# introduced it on powerpc. This allows for a more flexible hugepage
863# pagetable layouts.
864#
865config ARCH_HAS_HUGEPD
866 bool
867
868config MAPPING_DIRTY_HELPERS
869 bool
870
871endmenu
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_SHRINKER_DEFAULT_ON
49 bool "Shrink the zswap pool on memory pressure"
50 depends on ZSWAP
51 default n
52 help
53 If selected, the zswap shrinker will be enabled, and the pages
54 stored in the zswap pool will become available for reclaim (i.e
55 written back to the backing swap device) on memory pressure.
56
57 This means that zswap writeback could happen even if the pool is
58 not yet full, or the cgroup zswap limit has not been reached,
59 reducing the chance that cold pages will reside in the zswap pool
60 and consume memory indefinitely.
61
62choice
63 prompt "Default compressor"
64 depends on ZSWAP
65 default ZSWAP_COMPRESSOR_DEFAULT_LZO
66 help
67 Selects the default compression algorithm for the compressed cache
68 for swap pages.
69
70 For an overview what kind of performance can be expected from
71 a particular compression algorithm please refer to the benchmarks
72 available at the following LWN page:
73 https://lwn.net/Articles/751795/
74
75 If in doubt, select 'LZO'.
76
77 The selection made here can be overridden by using the kernel
78 command line 'zswap.compressor=' option.
79
80config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
81 bool "Deflate"
82 select CRYPTO_DEFLATE
83 help
84 Use the Deflate algorithm as the default compression algorithm.
85
86config ZSWAP_COMPRESSOR_DEFAULT_LZO
87 bool "LZO"
88 select CRYPTO_LZO
89 help
90 Use the LZO algorithm as the default compression algorithm.
91
92config ZSWAP_COMPRESSOR_DEFAULT_842
93 bool "842"
94 select CRYPTO_842
95 help
96 Use the 842 algorithm as the default compression algorithm.
97
98config ZSWAP_COMPRESSOR_DEFAULT_LZ4
99 bool "LZ4"
100 select CRYPTO_LZ4
101 help
102 Use the LZ4 algorithm as the default compression algorithm.
103
104config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
105 bool "LZ4HC"
106 select CRYPTO_LZ4HC
107 help
108 Use the LZ4HC algorithm as the default compression algorithm.
109
110config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
111 bool "zstd"
112 select CRYPTO_ZSTD
113 help
114 Use the zstd algorithm as the default compression algorithm.
115endchoice
116
117config ZSWAP_COMPRESSOR_DEFAULT
118 string
119 depends on ZSWAP
120 default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
121 default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
122 default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
123 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
124 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
125 default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
126 default ""
127
128choice
129 prompt "Default allocator"
130 depends on ZSWAP
131 default ZSWAP_ZPOOL_DEFAULT_ZSMALLOC if MMU
132 default ZSWAP_ZPOOL_DEFAULT_ZBUD
133 help
134 Selects the default allocator for the compressed cache for
135 swap pages.
136 The default is 'zbud' for compatibility, however please do
137 read the description of each of the allocators below before
138 making a right choice.
139
140 The selection made here can be overridden by using the kernel
141 command line 'zswap.zpool=' option.
142
143config ZSWAP_ZPOOL_DEFAULT_ZBUD
144 bool "zbud"
145 select ZBUD
146 help
147 Use the zbud allocator as the default allocator.
148
149config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
150 bool "z3fold"
151 select Z3FOLD
152 help
153 Use the z3fold allocator as the default allocator.
154
155config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
156 bool "zsmalloc"
157 select ZSMALLOC
158 help
159 Use the zsmalloc allocator as the default allocator.
160endchoice
161
162config ZSWAP_ZPOOL_DEFAULT
163 string
164 depends on ZSWAP
165 default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
166 default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
167 default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
168 default ""
169
170config ZBUD
171 tristate "2:1 compression allocator (zbud)"
172 depends on ZSWAP
173 help
174 A special purpose allocator for storing compressed pages.
175 It is designed to store up to two compressed pages per physical
176 page. While this design limits storage density, it has simple and
177 deterministic reclaim properties that make it preferable to a higher
178 density approach when reclaim will be used.
179
180config Z3FOLD
181 tristate "3:1 compression allocator (z3fold)"
182 depends on ZSWAP
183 help
184 A special purpose allocator for storing compressed pages.
185 It is designed to store up to three compressed pages per physical
186 page. It is a ZBUD derivative so the simplicity and determinism are
187 still there.
188
189config ZSMALLOC
190 tristate
191 prompt "N:1 compression allocator (zsmalloc)" if ZSWAP
192 depends on MMU
193 help
194 zsmalloc is a slab-based memory allocator designed to store
195 pages of various compression levels efficiently. It achieves
196 the highest storage density with the least amount of fragmentation.
197
198config ZSMALLOC_STAT
199 bool "Export zsmalloc statistics"
200 depends on ZSMALLOC
201 select DEBUG_FS
202 help
203 This option enables code in the zsmalloc to collect various
204 statistics about what's happening in zsmalloc and exports that
205 information to userspace via debugfs.
206 If unsure, say N.
207
208config ZSMALLOC_CHAIN_SIZE
209 int "Maximum number of physical pages per-zspage"
210 default 8
211 range 4 16
212 depends on ZSMALLOC
213 help
214 This option sets the upper limit on the number of physical pages
215 that a zmalloc page (zspage) can consist of. The optimal zspage
216 chain size is calculated for each size class during the
217 initialization of the pool.
218
219 Changing this option can alter the characteristics of size classes,
220 such as the number of pages per zspage and the number of objects
221 per zspage. This can also result in different configurations of
222 the pool, as zsmalloc merges size classes with similar
223 characteristics.
224
225 For more information, see zsmalloc documentation.
226
227menu "Slab allocator options"
228
229config SLUB
230 def_bool y
231
232config SLUB_TINY
233 bool "Configure for minimal memory footprint"
234 depends on EXPERT
235 select SLAB_MERGE_DEFAULT
236 help
237 Configures the slab allocator in a way to achieve minimal memory
238 footprint, sacrificing scalability, debugging and other features.
239 This is intended only for the smallest system that had used the
240 SLOB allocator and is not recommended for systems with more than
241 16MB RAM.
242
243 If unsure, say N.
244
245config SLAB_MERGE_DEFAULT
246 bool "Allow slab caches to be merged"
247 default y
248 help
249 For reduced kernel memory fragmentation, slab caches can be
250 merged when they share the same size and other characteristics.
251 This carries a risk of kernel heap overflows being able to
252 overwrite objects from merged caches (and more easily control
253 cache layout), which makes such heap attacks easier to exploit
254 by attackers. By keeping caches unmerged, these kinds of exploits
255 can usually only damage objects in the same cache. To disable
256 merging at runtime, "slab_nomerge" can be passed on the kernel
257 command line.
258
259config SLAB_FREELIST_RANDOM
260 bool "Randomize slab freelist"
261 depends on !SLUB_TINY
262 help
263 Randomizes the freelist order used on creating new pages. This
264 security feature reduces the predictability of the kernel slab
265 allocator against heap overflows.
266
267config SLAB_FREELIST_HARDENED
268 bool "Harden slab freelist metadata"
269 depends on !SLUB_TINY
270 help
271 Many kernel heap attacks try to target slab cache metadata and
272 other infrastructure. This options makes minor performance
273 sacrifices to harden the kernel slab allocator against common
274 freelist exploit methods.
275
276config SLUB_STATS
277 default n
278 bool "Enable performance statistics"
279 depends on SYSFS && !SLUB_TINY
280 help
281 The statistics are useful to debug slab allocation behavior in
282 order find ways to optimize the allocator. This should never be
283 enabled for production use since keeping statistics slows down
284 the allocator by a few percentage points. The slabinfo command
285 supports the determination of the most active slabs to figure
286 out which slabs are relevant to a particular load.
287 Try running: slabinfo -DA
288
289config SLUB_CPU_PARTIAL
290 default y
291 depends on SMP && !SLUB_TINY
292 bool "Enable per cpu partial caches"
293 help
294 Per cpu partial caches accelerate objects allocation and freeing
295 that is local to a processor at the price of more indeterminism
296 in the latency of the free. On overflow these caches will be cleared
297 which requires the taking of locks that may cause latency spikes.
298 Typically one would choose no for a realtime system.
299
300config RANDOM_KMALLOC_CACHES
301 default n
302 depends on !SLUB_TINY
303 bool "Randomize slab caches for normal kmalloc"
304 help
305 A hardening feature that creates multiple copies of slab caches for
306 normal kmalloc allocation and makes kmalloc randomly pick one based
307 on code address, which makes the attackers more difficult to spray
308 vulnerable memory objects on the heap for the purpose of exploiting
309 memory vulnerabilities.
310
311 Currently the number of copies is set to 16, a reasonably large value
312 that effectively diverges the memory objects allocated for different
313 subsystems or modules into different caches, at the expense of a
314 limited degree of memory and CPU overhead that relates to hardware and
315 system workload.
316
317endmenu # Slab allocator options
318
319config SHUFFLE_PAGE_ALLOCATOR
320 bool "Page allocator randomization"
321 default SLAB_FREELIST_RANDOM && ACPI_NUMA
322 help
323 Randomization of the page allocator improves the average
324 utilization of a direct-mapped memory-side-cache. See section
325 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
326 6.2a specification for an example of how a platform advertises
327 the presence of a memory-side-cache. There are also incidental
328 security benefits as it reduces the predictability of page
329 allocations to compliment SLAB_FREELIST_RANDOM, but the
330 default granularity of shuffling on the MAX_PAGE_ORDER i.e, 10th
331 order of pages is selected based on cache utilization benefits
332 on x86.
333
334 While the randomization improves cache utilization it may
335 negatively impact workloads on platforms without a cache. For
336 this reason, by default, the randomization is enabled only
337 after runtime detection of a direct-mapped memory-side-cache.
338 Otherwise, the randomization may be force enabled with the
339 'page_alloc.shuffle' kernel command line parameter.
340
341 Say Y if unsure.
342
343config COMPAT_BRK
344 bool "Disable heap randomization"
345 default y
346 help
347 Randomizing heap placement makes heap exploits harder, but it
348 also breaks ancient binaries (including anything libc5 based).
349 This option changes the bootup default to heap randomization
350 disabled, and can be overridden at runtime by setting
351 /proc/sys/kernel/randomize_va_space to 2.
352
353 On non-ancient distros (post-2000 ones) N is usually a safe choice.
354
355config MMAP_ALLOW_UNINITIALIZED
356 bool "Allow mmapped anonymous memory to be uninitialized"
357 depends on EXPERT && !MMU
358 default n
359 help
360 Normally, and according to the Linux spec, anonymous memory obtained
361 from mmap() has its contents cleared before it is passed to
362 userspace. Enabling this config option allows you to request that
363 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
364 providing a huge performance boost. If this option is not enabled,
365 then the flag will be ignored.
366
367 This is taken advantage of by uClibc's malloc(), and also by
368 ELF-FDPIC binfmt's brk and stack allocator.
369
370 Because of the obvious security issues, this option should only be
371 enabled on embedded devices where you control what is run in
372 userspace. Since that isn't generally a problem on no-MMU systems,
373 it is normally safe to say Y here.
374
375 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
376
377config SELECT_MEMORY_MODEL
378 def_bool y
379 depends on ARCH_SELECT_MEMORY_MODEL
380
381choice
382 prompt "Memory model"
383 depends on SELECT_MEMORY_MODEL
384 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
385 default FLATMEM_MANUAL
386 help
387 This option allows you to change some of the ways that
388 Linux manages its memory internally. Most users will
389 only have one option here selected by the architecture
390 configuration. This is normal.
391
392config FLATMEM_MANUAL
393 bool "Flat Memory"
394 depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE
395 help
396 This option is best suited for non-NUMA systems with
397 flat address space. The FLATMEM is the most efficient
398 system in terms of performance and resource consumption
399 and it is the best option for smaller systems.
400
401 For systems that have holes in their physical address
402 spaces and for features like NUMA and memory hotplug,
403 choose "Sparse Memory".
404
405 If unsure, choose this option (Flat Memory) over any other.
406
407config SPARSEMEM_MANUAL
408 bool "Sparse Memory"
409 depends on ARCH_SPARSEMEM_ENABLE
410 help
411 This will be the only option for some systems, including
412 memory hot-plug systems. This is normal.
413
414 This option provides efficient support for systems with
415 holes is their physical address space and allows memory
416 hot-plug and hot-remove.
417
418 If unsure, choose "Flat Memory" over this option.
419
420endchoice
421
422config SPARSEMEM
423 def_bool y
424 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
425
426config FLATMEM
427 def_bool y
428 depends on !SPARSEMEM || FLATMEM_MANUAL
429
430#
431# SPARSEMEM_EXTREME (which is the default) does some bootmem
432# allocations when sparse_init() is called. If this cannot
433# be done on your architecture, select this option. However,
434# statically allocating the mem_section[] array can potentially
435# consume vast quantities of .bss, so be careful.
436#
437# This option will also potentially produce smaller runtime code
438# with gcc 3.4 and later.
439#
440config SPARSEMEM_STATIC
441 bool
442
443#
444# Architecture platforms which require a two level mem_section in SPARSEMEM
445# must select this option. This is usually for architecture platforms with
446# an extremely sparse physical address space.
447#
448config SPARSEMEM_EXTREME
449 def_bool y
450 depends on SPARSEMEM && !SPARSEMEM_STATIC
451
452config SPARSEMEM_VMEMMAP_ENABLE
453 bool
454
455config SPARSEMEM_VMEMMAP
456 bool "Sparse Memory virtual memmap"
457 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
458 default y
459 help
460 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
461 pfn_to_page and page_to_pfn operations. This is the most
462 efficient option when sufficient kernel resources are available.
463#
464# Select this config option from the architecture Kconfig, if it is preferred
465# to enable the feature of HugeTLB/dev_dax vmemmap optimization.
466#
467config ARCH_WANT_OPTIMIZE_DAX_VMEMMAP
468 bool
469
470config ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP
471 bool
472
473config HAVE_MEMBLOCK_PHYS_MAP
474 bool
475
476config HAVE_FAST_GUP
477 depends on MMU
478 bool
479
480# Don't discard allocated memory used to track "memory" and "reserved" memblocks
481# after early boot, so it can still be used to test for validity of memory.
482# Also, memblocks are updated with memory hot(un)plug.
483config ARCH_KEEP_MEMBLOCK
484 bool
485
486# Keep arch NUMA mapping infrastructure post-init.
487config NUMA_KEEP_MEMINFO
488 bool
489
490config MEMORY_ISOLATION
491 bool
492
493# IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked
494# IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via
495# /dev/mem.
496config EXCLUSIVE_SYSTEM_RAM
497 def_bool y
498 depends on !DEVMEM || STRICT_DEVMEM
499
500#
501# Only be set on architectures that have completely implemented memory hotplug
502# feature. If you are not sure, don't touch it.
503#
504config HAVE_BOOTMEM_INFO_NODE
505 def_bool n
506
507config ARCH_ENABLE_MEMORY_HOTPLUG
508 bool
509
510config ARCH_ENABLE_MEMORY_HOTREMOVE
511 bool
512
513# eventually, we can have this option just 'select SPARSEMEM'
514menuconfig MEMORY_HOTPLUG
515 bool "Memory hotplug"
516 select MEMORY_ISOLATION
517 depends on SPARSEMEM
518 depends on ARCH_ENABLE_MEMORY_HOTPLUG
519 depends on 64BIT
520 select NUMA_KEEP_MEMINFO if NUMA
521
522if MEMORY_HOTPLUG
523
524config MEMORY_HOTPLUG_DEFAULT_ONLINE
525 bool "Online the newly added memory blocks by default"
526 depends on MEMORY_HOTPLUG
527 help
528 This option sets the default policy setting for memory hotplug
529 onlining policy (/sys/devices/system/memory/auto_online_blocks) which
530 determines what happens to newly added memory regions. Policy setting
531 can always be changed at runtime.
532 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
533
534 Say Y here if you want all hot-plugged memory blocks to appear in
535 'online' state by default.
536 Say N here if you want the default policy to keep all hot-plugged
537 memory blocks in 'offline' state.
538
539config MEMORY_HOTREMOVE
540 bool "Allow for memory hot remove"
541 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
542 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
543 depends on MIGRATION
544
545config MHP_MEMMAP_ON_MEMORY
546 def_bool y
547 depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
548 depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
549
550endif # MEMORY_HOTPLUG
551
552config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
553 bool
554
555# Heavily threaded applications may benefit from splitting the mm-wide
556# page_table_lock, so that faults on different parts of the user address
557# space can be handled with less contention: split it at this NR_CPUS.
558# Default to 4 for wider testing, though 8 might be more appropriate.
559# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
560# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
561# SPARC32 allocates multiple pte tables within a single page, and therefore
562# a per-page lock leads to problems when multiple tables need to be locked
563# at the same time (e.g. copy_page_range()).
564# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
565#
566config SPLIT_PTLOCK_CPUS
567 int
568 default "999999" if !MMU
569 default "999999" if ARM && !CPU_CACHE_VIPT
570 default "999999" if PARISC && !PA20
571 default "999999" if SPARC32
572 default "4"
573
574config ARCH_ENABLE_SPLIT_PMD_PTLOCK
575 bool
576
577#
578# support for memory balloon
579config MEMORY_BALLOON
580 bool
581
582#
583# support for memory balloon compaction
584config BALLOON_COMPACTION
585 bool "Allow for balloon memory compaction/migration"
586 default y
587 depends on COMPACTION && MEMORY_BALLOON
588 help
589 Memory fragmentation introduced by ballooning might reduce
590 significantly the number of 2MB contiguous memory blocks that can be
591 used within a guest, thus imposing performance penalties associated
592 with the reduced number of transparent huge pages that could be used
593 by the guest workload. Allowing the compaction & migration for memory
594 pages enlisted as being part of memory balloon devices avoids the
595 scenario aforementioned and helps improving memory defragmentation.
596
597#
598# support for memory compaction
599config COMPACTION
600 bool "Allow for memory compaction"
601 default y
602 select MIGRATION
603 depends on MMU
604 help
605 Compaction is the only memory management component to form
606 high order (larger physically contiguous) memory blocks
607 reliably. The page allocator relies on compaction heavily and
608 the lack of the feature can lead to unexpected OOM killer
609 invocations for high order memory requests. You shouldn't
610 disable this option unless there really is a strong reason for
611 it and then we would be really interested to hear about that at
612 linux-mm@kvack.org.
613
614config COMPACT_UNEVICTABLE_DEFAULT
615 int
616 depends on COMPACTION
617 default 0 if PREEMPT_RT
618 default 1
619
620#
621# support for free page reporting
622config PAGE_REPORTING
623 bool "Free page reporting"
624 help
625 Free page reporting allows for the incremental acquisition of
626 free pages from the buddy allocator for the purpose of reporting
627 those pages to another entity, such as a hypervisor, so that the
628 memory can be freed within the host for other uses.
629
630#
631# support for page migration
632#
633config MIGRATION
634 bool "Page migration"
635 default y
636 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
637 help
638 Allows the migration of the physical location of pages of processes
639 while the virtual addresses are not changed. This is useful in
640 two situations. The first is on NUMA systems to put pages nearer
641 to the processors accessing. The second is when allocating huge
642 pages as migration can relocate pages to satisfy a huge page
643 allocation instead of reclaiming.
644
645config DEVICE_MIGRATION
646 def_bool MIGRATION && ZONE_DEVICE
647
648config ARCH_ENABLE_HUGEPAGE_MIGRATION
649 bool
650
651config ARCH_ENABLE_THP_MIGRATION
652 bool
653
654config HUGETLB_PAGE_SIZE_VARIABLE
655 def_bool n
656 help
657 Allows the pageblock_order value to be dynamic instead of just standard
658 HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available
659 on a platform.
660
661 Note that the pageblock_order cannot exceed MAX_PAGE_ORDER and will be
662 clamped down to MAX_PAGE_ORDER.
663
664config CONTIG_ALLOC
665 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
666
667config PCP_BATCH_SCALE_MAX
668 int "Maximum scale factor of PCP (Per-CPU pageset) batch allocate/free"
669 default 5
670 range 0 6
671 help
672 In page allocator, PCP (Per-CPU pageset) is refilled and drained in
673 batches. The batch number is scaled automatically to improve page
674 allocation/free throughput. But too large scale factor may hurt
675 latency. This option sets the upper limit of scale factor to limit
676 the maximum latency.
677
678config PHYS_ADDR_T_64BIT
679 def_bool 64BIT
680
681config BOUNCE
682 bool "Enable bounce buffers"
683 default y
684 depends on BLOCK && MMU && HIGHMEM
685 help
686 Enable bounce buffers for devices that cannot access the full range of
687 memory available to the CPU. Enabled by default when HIGHMEM is
688 selected, but you may say n to override this.
689
690config MMU_NOTIFIER
691 bool
692 select INTERVAL_TREE
693
694config KSM
695 bool "Enable KSM for page merging"
696 depends on MMU
697 select XXHASH
698 help
699 Enable Kernel Samepage Merging: KSM periodically scans those areas
700 of an application's address space that an app has advised may be
701 mergeable. When it finds pages of identical content, it replaces
702 the many instances by a single page with that content, so
703 saving memory until one or another app needs to modify the content.
704 Recommended for use with KVM, or with other duplicative applications.
705 See Documentation/mm/ksm.rst for more information: KSM is inactive
706 until a program has madvised that an area is MADV_MERGEABLE, and
707 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
708
709config DEFAULT_MMAP_MIN_ADDR
710 int "Low address space to protect from user allocation"
711 depends on MMU
712 default 4096
713 help
714 This is the portion of low virtual memory which should be protected
715 from userspace allocation. Keeping a user from writing to low pages
716 can help reduce the impact of kernel NULL pointer bugs.
717
718 For most ppc64 and x86 users with lots of address space
719 a value of 65536 is reasonable and should cause no problems.
720 On arm and other archs it should not be higher than 32768.
721 Programs which use vm86 functionality or have some need to map
722 this low address space will need CAP_SYS_RAWIO or disable this
723 protection by setting the value to 0.
724
725 This value can be changed after boot using the
726 /proc/sys/vm/mmap_min_addr tunable.
727
728config ARCH_SUPPORTS_MEMORY_FAILURE
729 bool
730
731config MEMORY_FAILURE
732 depends on MMU
733 depends on ARCH_SUPPORTS_MEMORY_FAILURE
734 bool "Enable recovery from hardware memory errors"
735 select MEMORY_ISOLATION
736 select RAS
737 help
738 Enables code to recover from some memory failures on systems
739 with MCA recovery. This allows a system to continue running
740 even when some of its memory has uncorrected errors. This requires
741 special hardware support and typically ECC memory.
742
743config HWPOISON_INJECT
744 tristate "HWPoison pages injector"
745 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
746 select PROC_PAGE_MONITOR
747
748config NOMMU_INITIAL_TRIM_EXCESS
749 int "Turn on mmap() excess space trimming before booting"
750 depends on !MMU
751 default 1
752 help
753 The NOMMU mmap() frequently needs to allocate large contiguous chunks
754 of memory on which to store mappings, but it can only ask the system
755 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
756 more than it requires. To deal with this, mmap() is able to trim off
757 the excess and return it to the allocator.
758
759 If trimming is enabled, the excess is trimmed off and returned to the
760 system allocator, which can cause extra fragmentation, particularly
761 if there are a lot of transient processes.
762
763 If trimming is disabled, the excess is kept, but not used, which for
764 long-term mappings means that the space is wasted.
765
766 Trimming can be dynamically controlled through a sysctl option
767 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
768 excess pages there must be before trimming should occur, or zero if
769 no trimming is to occur.
770
771 This option specifies the initial value of this option. The default
772 of 1 says that all excess pages should be trimmed.
773
774 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
775
776config ARCH_WANT_GENERAL_HUGETLB
777 bool
778
779config ARCH_WANTS_THP_SWAP
780 def_bool n
781
782menuconfig TRANSPARENT_HUGEPAGE
783 bool "Transparent Hugepage Support"
784 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT
785 select COMPACTION
786 select XARRAY_MULTI
787 help
788 Transparent Hugepages allows the kernel to use huge pages and
789 huge tlb transparently to the applications whenever possible.
790 This feature can improve computing performance to certain
791 applications by speeding up page faults during memory
792 allocation, by reducing the number of tlb misses and by speeding
793 up the pagetable walking.
794
795 If memory constrained on embedded, you may want to say N.
796
797if TRANSPARENT_HUGEPAGE
798
799choice
800 prompt "Transparent Hugepage Support sysfs defaults"
801 depends on TRANSPARENT_HUGEPAGE
802 default TRANSPARENT_HUGEPAGE_ALWAYS
803 help
804 Selects the sysfs defaults for Transparent Hugepage Support.
805
806 config TRANSPARENT_HUGEPAGE_ALWAYS
807 bool "always"
808 help
809 Enabling Transparent Hugepage always, can increase the
810 memory footprint of applications without a guaranteed
811 benefit but it will work automatically for all applications.
812
813 config TRANSPARENT_HUGEPAGE_MADVISE
814 bool "madvise"
815 help
816 Enabling Transparent Hugepage madvise, will only provide a
817 performance improvement benefit to the applications using
818 madvise(MADV_HUGEPAGE) but it won't risk to increase the
819 memory footprint of applications without a guaranteed
820 benefit.
821
822 config TRANSPARENT_HUGEPAGE_NEVER
823 bool "never"
824 help
825 Disable Transparent Hugepage by default. It can still be
826 enabled at runtime via sysfs.
827endchoice
828
829config THP_SWAP
830 def_bool y
831 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT
832 help
833 Swap transparent huge pages in one piece, without splitting.
834 XXX: For now, swap cluster backing transparent huge page
835 will be split after swapout.
836
837 For selection by architectures with reasonable THP sizes.
838
839config READ_ONLY_THP_FOR_FS
840 bool "Read-only THP for filesystems (EXPERIMENTAL)"
841 depends on TRANSPARENT_HUGEPAGE && SHMEM
842
843 help
844 Allow khugepaged to put read-only file-backed pages in THP.
845
846 This is marked experimental because it is a new feature. Write
847 support of file THPs will be developed in the next few release
848 cycles.
849
850endif # TRANSPARENT_HUGEPAGE
851
852#
853# UP and nommu archs use km based percpu allocator
854#
855config NEED_PER_CPU_KM
856 depends on !SMP || !MMU
857 bool
858 default y
859
860config NEED_PER_CPU_EMBED_FIRST_CHUNK
861 bool
862
863config NEED_PER_CPU_PAGE_FIRST_CHUNK
864 bool
865
866config USE_PERCPU_NUMA_NODE_ID
867 bool
868
869config HAVE_SETUP_PER_CPU_AREA
870 bool
871
872config CMA
873 bool "Contiguous Memory Allocator"
874 depends on MMU
875 select MIGRATION
876 select MEMORY_ISOLATION
877 help
878 This enables the Contiguous Memory Allocator which allows other
879 subsystems to allocate big physically-contiguous blocks of memory.
880 CMA reserves a region of memory and allows only movable pages to
881 be allocated from it. This way, the kernel can use the memory for
882 pagecache and when a subsystem requests for contiguous area, the
883 allocated pages are migrated away to serve the contiguous request.
884
885 If unsure, say "n".
886
887config CMA_DEBUGFS
888 bool "CMA debugfs interface"
889 depends on CMA && DEBUG_FS
890 help
891 Turns on the DebugFS interface for CMA.
892
893config CMA_SYSFS
894 bool "CMA information through sysfs interface"
895 depends on CMA && SYSFS
896 help
897 This option exposes some sysfs attributes to get information
898 from CMA.
899
900config CMA_AREAS
901 int "Maximum count of the CMA areas"
902 depends on CMA
903 default 20 if NUMA
904 default 8
905 help
906 CMA allows to create CMA areas for particular purpose, mainly,
907 used as device private area. This parameter sets the maximum
908 number of CMA area in the system.
909
910 If unsure, leave the default value "8" in UMA and "20" in NUMA.
911
912config MEM_SOFT_DIRTY
913 bool "Track memory changes"
914 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
915 select PROC_PAGE_MONITOR
916 help
917 This option enables memory changes tracking by introducing a
918 soft-dirty bit on pte-s. This bit it set when someone writes
919 into a page just as regular dirty bit, but unlike the latter
920 it can be cleared by hands.
921
922 See Documentation/admin-guide/mm/soft-dirty.rst for more details.
923
924config GENERIC_EARLY_IOREMAP
925 bool
926
927config STACK_MAX_DEFAULT_SIZE_MB
928 int "Default maximum user stack size for 32-bit processes (MB)"
929 default 100
930 range 8 2048
931 depends on STACK_GROWSUP && (!64BIT || COMPAT)
932 help
933 This is the maximum stack size in Megabytes in the VM layout of 32-bit
934 user processes when the stack grows upwards (currently only on parisc
935 arch) when the RLIMIT_STACK hard limit is unlimited.
936
937 A sane initial value is 100 MB.
938
939config DEFERRED_STRUCT_PAGE_INIT
940 bool "Defer initialisation of struct pages to kthreads"
941 depends on SPARSEMEM
942 depends on !NEED_PER_CPU_KM
943 depends on 64BIT
944 select PADATA
945 help
946 Ordinarily all struct pages are initialised during early boot in a
947 single thread. On very large machines this can take a considerable
948 amount of time. If this option is set, large machines will bring up
949 a subset of memmap at boot and then initialise the rest in parallel.
950 This has a potential performance impact on tasks running early in the
951 lifetime of the system until these kthreads finish the
952 initialisation.
953
954config PAGE_IDLE_FLAG
955 bool
956 select PAGE_EXTENSION if !64BIT
957 help
958 This adds PG_idle and PG_young flags to 'struct page'. PTE Accessed
959 bit writers can set the state of the bit in the flags so that PTE
960 Accessed bit readers may avoid disturbance.
961
962config IDLE_PAGE_TRACKING
963 bool "Enable idle page tracking"
964 depends on SYSFS && MMU
965 select PAGE_IDLE_FLAG
966 help
967 This feature allows to estimate the amount of user pages that have
968 not been touched during a given period of time. This information can
969 be useful to tune memory cgroup limits and/or for job placement
970 within a compute cluster.
971
972 See Documentation/admin-guide/mm/idle_page_tracking.rst for
973 more details.
974
975# Architectures which implement cpu_dcache_is_aliasing() to query
976# whether the data caches are aliased (VIVT or VIPT with dcache
977# aliasing) need to select this.
978config ARCH_HAS_CPU_CACHE_ALIASING
979 bool
980
981config ARCH_HAS_CACHE_LINE_SIZE
982 bool
983
984config ARCH_HAS_CURRENT_STACK_POINTER
985 bool
986 help
987 In support of HARDENED_USERCOPY performing stack variable lifetime
988 checking, an architecture-agnostic way to find the stack pointer
989 is needed. Once an architecture defines an unsigned long global
990 register alias named "current_stack_pointer", this config can be
991 selected.
992
993config ARCH_HAS_PTE_DEVMAP
994 bool
995
996config ARCH_HAS_ZONE_DMA_SET
997 bool
998
999config ZONE_DMA
1000 bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET
1001 default y if ARM64 || X86
1002
1003config ZONE_DMA32
1004 bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET
1005 depends on !X86_32
1006 default y if ARM64
1007
1008config ZONE_DEVICE
1009 bool "Device memory (pmem, HMM, etc...) hotplug support"
1010 depends on MEMORY_HOTPLUG
1011 depends on MEMORY_HOTREMOVE
1012 depends on SPARSEMEM_VMEMMAP
1013 depends on ARCH_HAS_PTE_DEVMAP
1014 select XARRAY_MULTI
1015
1016 help
1017 Device memory hotplug support allows for establishing pmem,
1018 or other device driver discovered memory regions, in the
1019 memmap. This allows pfn_to_page() lookups of otherwise
1020 "device-physical" addresses which is needed for using a DAX
1021 mapping in an O_DIRECT operation, among other things.
1022
1023 If FS_DAX is enabled, then say Y.
1024
1025#
1026# Helpers to mirror range of the CPU page tables of a process into device page
1027# tables.
1028#
1029config HMM_MIRROR
1030 bool
1031 depends on MMU
1032
1033config GET_FREE_REGION
1034 depends on SPARSEMEM
1035 bool
1036
1037config DEVICE_PRIVATE
1038 bool "Unaddressable device memory (GPU memory, ...)"
1039 depends on ZONE_DEVICE
1040 select GET_FREE_REGION
1041
1042 help
1043 Allows creation of struct pages to represent unaddressable device
1044 memory; i.e., memory that is only accessible from the device (or
1045 group of devices). You likely also want to select HMM_MIRROR.
1046
1047config VMAP_PFN
1048 bool
1049
1050config ARCH_USES_HIGH_VMA_FLAGS
1051 bool
1052config ARCH_HAS_PKEYS
1053 bool
1054
1055config ARCH_USES_PG_ARCH_X
1056 bool
1057 help
1058 Enable the definition of PG_arch_x page flags with x > 1. Only
1059 suitable for 64-bit architectures with CONFIG_FLATMEM or
1060 CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be
1061 enough room for additional bits in page->flags.
1062
1063config VM_EVENT_COUNTERS
1064 default y
1065 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1066 help
1067 VM event counters are needed for event counts to be shown.
1068 This option allows the disabling of the VM event counters
1069 on EXPERT systems. /proc/vmstat will only show page counts
1070 if VM event counters are disabled.
1071
1072config PERCPU_STATS
1073 bool "Collect percpu memory statistics"
1074 help
1075 This feature collects and exposes statistics via debugfs. The
1076 information includes global and per chunk statistics, which can
1077 be used to help understand percpu memory usage.
1078
1079config GUP_TEST
1080 bool "Enable infrastructure for get_user_pages()-related unit tests"
1081 depends on DEBUG_FS
1082 help
1083 Provides /sys/kernel/debug/gup_test, which in turn provides a way
1084 to make ioctl calls that can launch kernel-based unit tests for
1085 the get_user_pages*() and pin_user_pages*() family of API calls.
1086
1087 These tests include benchmark testing of the _fast variants of
1088 get_user_pages*() and pin_user_pages*(), as well as smoke tests of
1089 the non-_fast variants.
1090
1091 There is also a sub-test that allows running dump_page() on any
1092 of up to eight pages (selected by command line args) within the
1093 range of user-space addresses. These pages are either pinned via
1094 pin_user_pages*(), or pinned via get_user_pages*(), as specified
1095 by other command line arguments.
1096
1097 See tools/testing/selftests/mm/gup_test.c
1098
1099comment "GUP_TEST needs to have DEBUG_FS enabled"
1100 depends on !GUP_TEST && !DEBUG_FS
1101
1102config GUP_GET_PXX_LOW_HIGH
1103 bool
1104
1105config DMAPOOL_TEST
1106 tristate "Enable a module to run time tests on dma_pool"
1107 depends on HAS_DMA
1108 help
1109 Provides a test module that will allocate and free many blocks of
1110 various sizes and report how long it takes. This is intended to
1111 provide a consistent way to measure how changes to the
1112 dma_pool_alloc/free routines affect performance.
1113
1114config ARCH_HAS_PTE_SPECIAL
1115 bool
1116
1117#
1118# Some architectures require a special hugepage directory format that is
1119# required to support multiple hugepage sizes. For example a4fe3ce76
1120# "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
1121# introduced it on powerpc. This allows for a more flexible hugepage
1122# pagetable layouts.
1123#
1124config ARCH_HAS_HUGEPD
1125 bool
1126
1127config MAPPING_DIRTY_HELPERS
1128 bool
1129
1130config KMAP_LOCAL
1131 bool
1132
1133config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY
1134 bool
1135
1136# struct io_mapping based helper. Selected by drivers that need them
1137config IO_MAPPING
1138 bool
1139
1140config MEMFD_CREATE
1141 bool "Enable memfd_create() system call" if EXPERT
1142
1143config SECRETMEM
1144 default y
1145 bool "Enable memfd_secret() system call" if EXPERT
1146 depends on ARCH_HAS_SET_DIRECT_MAP
1147 help
1148 Enable the memfd_secret() system call with the ability to create
1149 memory areas visible only in the context of the owning process and
1150 not mapped to other processes and other kernel page tables.
1151
1152config ANON_VMA_NAME
1153 bool "Anonymous VMA name support"
1154 depends on PROC_FS && ADVISE_SYSCALLS && MMU
1155
1156 help
1157 Allow naming anonymous virtual memory areas.
1158
1159 This feature allows assigning names to virtual memory areas. Assigned
1160 names can be later retrieved from /proc/pid/maps and /proc/pid/smaps
1161 and help identifying individual anonymous memory areas.
1162 Assigning a name to anonymous virtual memory area might prevent that
1163 area from being merged with adjacent virtual memory areas due to the
1164 difference in their name.
1165
1166config HAVE_ARCH_USERFAULTFD_WP
1167 bool
1168 help
1169 Arch has userfaultfd write protection support
1170
1171config HAVE_ARCH_USERFAULTFD_MINOR
1172 bool
1173 help
1174 Arch has userfaultfd minor fault support
1175
1176menuconfig USERFAULTFD
1177 bool "Enable userfaultfd() system call"
1178 depends on MMU
1179 help
1180 Enable the userfaultfd() system call that allows to intercept and
1181 handle page faults in userland.
1182
1183if USERFAULTFD
1184config PTE_MARKER_UFFD_WP
1185 bool "Userfaultfd write protection support for shmem/hugetlbfs"
1186 default y
1187 depends on HAVE_ARCH_USERFAULTFD_WP
1188
1189 help
1190 Allows to create marker PTEs for userfaultfd write protection
1191 purposes. It is required to enable userfaultfd write protection on
1192 file-backed memory types like shmem and hugetlbfs.
1193endif # USERFAULTFD
1194
1195# multi-gen LRU {
1196config LRU_GEN
1197 bool "Multi-Gen LRU"
1198 depends on MMU
1199 # make sure folio->flags has enough spare bits
1200 depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP
1201 help
1202 A high performance LRU implementation to overcommit memory. See
1203 Documentation/admin-guide/mm/multigen_lru.rst for details.
1204
1205config LRU_GEN_ENABLED
1206 bool "Enable by default"
1207 depends on LRU_GEN
1208 help
1209 This option enables the multi-gen LRU by default.
1210
1211config LRU_GEN_STATS
1212 bool "Full stats for debugging"
1213 depends on LRU_GEN
1214 help
1215 Do not enable this option unless you plan to look at historical stats
1216 from evicted generations for debugging purpose.
1217
1218 This option has a per-memcg and per-node memory overhead.
1219
1220config LRU_GEN_WALKS_MMU
1221 def_bool y
1222 depends on LRU_GEN && ARCH_HAS_HW_PTE_YOUNG
1223# }
1224
1225config ARCH_SUPPORTS_PER_VMA_LOCK
1226 def_bool n
1227
1228config PER_VMA_LOCK
1229 def_bool y
1230 depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP
1231 help
1232 Allow per-vma locking during page fault handling.
1233
1234 This feature allows locking each virtual memory area separately when
1235 handling page faults instead of taking mmap_lock.
1236
1237config LOCK_MM_AND_FIND_VMA
1238 bool
1239 depends on !STACK_GROWSUP
1240
1241config IOMMU_MM_DATA
1242 bool
1243
1244source "mm/damon/Kconfig"
1245
1246endmenu