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