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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
194menu "SLAB allocator options"
195
196choice
197 prompt "Choose SLAB allocator"
198 default SLUB
199 help
200 This option allows to select a slab allocator.
201
202config SLAB
203 bool "SLAB"
204 depends on !PREEMPT_RT
205 select HAVE_HARDENED_USERCOPY_ALLOCATOR
206 help
207 The regular slab allocator that is established and known to work
208 well in all environments. It organizes cache hot objects in
209 per cpu and per node queues.
210
211config SLUB
212 bool "SLUB (Unqueued Allocator)"
213 select HAVE_HARDENED_USERCOPY_ALLOCATOR
214 help
215 SLUB is a slab allocator that minimizes cache line usage
216 instead of managing queues of cached objects (SLAB approach).
217 Per cpu caching is realized using slabs of objects instead
218 of queues of objects. SLUB can use memory efficiently
219 and has enhanced diagnostics. SLUB is the default choice for
220 a slab allocator.
221
222config SLOB_DEPRECATED
223 depends on EXPERT
224 bool "SLOB (Simple Allocator - DEPRECATED)"
225 depends on !PREEMPT_RT
226 help
227 Deprecated and scheduled for removal in a few cycles. SLUB
228 recommended as replacement. CONFIG_SLUB_TINY can be considered
229 on systems with 16MB or less RAM.
230
231 If you need SLOB to stay, please contact linux-mm@kvack.org and
232 people listed in the SLAB ALLOCATOR section of MAINTAINERS file,
233 with your use case.
234
235 SLOB replaces the stock allocator with a drastically simpler
236 allocator. SLOB is generally more space efficient but
237 does not perform as well on large systems.
238
239endchoice
240
241config SLOB
242 bool
243 default y
244 depends on SLOB_DEPRECATED
245
246config SLUB_TINY
247 bool "Configure SLUB for minimal memory footprint"
248 depends on SLUB && EXPERT
249 select SLAB_MERGE_DEFAULT
250 help
251 Configures the SLUB allocator in a way to achieve minimal memory
252 footprint, sacrificing scalability, debugging and other features.
253 This is intended only for the smallest system that had used the
254 SLOB allocator and is not recommended for systems with more than
255 16MB RAM.
256
257 If unsure, say N.
258
259config SLAB_MERGE_DEFAULT
260 bool "Allow slab caches to be merged"
261 default y
262 depends on SLAB || SLUB
263 help
264 For reduced kernel memory fragmentation, slab caches can be
265 merged when they share the same size and other characteristics.
266 This carries a risk of kernel heap overflows being able to
267 overwrite objects from merged caches (and more easily control
268 cache layout), which makes such heap attacks easier to exploit
269 by attackers. By keeping caches unmerged, these kinds of exploits
270 can usually only damage objects in the same cache. To disable
271 merging at runtime, "slab_nomerge" can be passed on the kernel
272 command line.
273
274config SLAB_FREELIST_RANDOM
275 bool "Randomize slab freelist"
276 depends on SLAB || (SLUB && !SLUB_TINY)
277 help
278 Randomizes the freelist order used on creating new pages. This
279 security feature reduces the predictability of the kernel slab
280 allocator against heap overflows.
281
282config SLAB_FREELIST_HARDENED
283 bool "Harden slab freelist metadata"
284 depends on SLAB || (SLUB && !SLUB_TINY)
285 help
286 Many kernel heap attacks try to target slab cache metadata and
287 other infrastructure. This options makes minor performance
288 sacrifices to harden the kernel slab allocator against common
289 freelist exploit methods. Some slab implementations have more
290 sanity-checking than others. This option is most effective with
291 CONFIG_SLUB.
292
293config SLUB_STATS
294 default n
295 bool "Enable SLUB performance statistics"
296 depends on SLUB && SYSFS && !SLUB_TINY
297 help
298 SLUB statistics are useful to debug SLUBs allocation behavior in
299 order find ways to optimize the allocator. This should never be
300 enabled for production use since keeping statistics slows down
301 the allocator by a few percentage points. The slabinfo command
302 supports the determination of the most active slabs to figure
303 out which slabs are relevant to a particular load.
304 Try running: slabinfo -DA
305
306config SLUB_CPU_PARTIAL
307 default y
308 depends on SLUB && SMP && !SLUB_TINY
309 bool "SLUB per cpu partial cache"
310 help
311 Per cpu partial caches accelerate objects allocation and freeing
312 that is local to a processor at the price of more indeterminism
313 in the latency of the free. On overflow these caches will be cleared
314 which requires the taking of locks that may cause latency spikes.
315 Typically one would choose no for a realtime system.
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_ORDER - 1" i.e,
331 10th order of pages is selected based on cache utilization
332 benefits 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
464config HAVE_MEMBLOCK_PHYS_MAP
465 bool
466
467config HAVE_FAST_GUP
468 depends on MMU
469 bool
470
471# Don't discard allocated memory used to track "memory" and "reserved" memblocks
472# after early boot, so it can still be used to test for validity of memory.
473# Also, memblocks are updated with memory hot(un)plug.
474config ARCH_KEEP_MEMBLOCK
475 bool
476
477# Keep arch NUMA mapping infrastructure post-init.
478config NUMA_KEEP_MEMINFO
479 bool
480
481config MEMORY_ISOLATION
482 bool
483
484# IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked
485# IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via
486# /dev/mem.
487config EXCLUSIVE_SYSTEM_RAM
488 def_bool y
489 depends on !DEVMEM || STRICT_DEVMEM
490
491#
492# Only be set on architectures that have completely implemented memory hotplug
493# feature. If you are not sure, don't touch it.
494#
495config HAVE_BOOTMEM_INFO_NODE
496 def_bool n
497
498config ARCH_ENABLE_MEMORY_HOTPLUG
499 bool
500
501config ARCH_ENABLE_MEMORY_HOTREMOVE
502 bool
503
504# eventually, we can have this option just 'select SPARSEMEM'
505menuconfig MEMORY_HOTPLUG
506 bool "Memory hotplug"
507 select MEMORY_ISOLATION
508 depends on SPARSEMEM
509 depends on ARCH_ENABLE_MEMORY_HOTPLUG
510 depends on 64BIT
511 select NUMA_KEEP_MEMINFO if NUMA
512
513if MEMORY_HOTPLUG
514
515config MEMORY_HOTPLUG_DEFAULT_ONLINE
516 bool "Online the newly added memory blocks by default"
517 depends on MEMORY_HOTPLUG
518 help
519 This option sets the default policy setting for memory hotplug
520 onlining policy (/sys/devices/system/memory/auto_online_blocks) which
521 determines what happens to newly added memory regions. Policy setting
522 can always be changed at runtime.
523 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
524
525 Say Y here if you want all hot-plugged memory blocks to appear in
526 'online' state by default.
527 Say N here if you want the default policy to keep all hot-plugged
528 memory blocks in 'offline' state.
529
530config MEMORY_HOTREMOVE
531 bool "Allow for memory hot remove"
532 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
533 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
534 depends on MIGRATION
535
536config MHP_MEMMAP_ON_MEMORY
537 def_bool y
538 depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
539 depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
540
541endif # MEMORY_HOTPLUG
542
543# Heavily threaded applications may benefit from splitting the mm-wide
544# page_table_lock, so that faults on different parts of the user address
545# space can be handled with less contention: split it at this NR_CPUS.
546# Default to 4 for wider testing, though 8 might be more appropriate.
547# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
548# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
549# SPARC32 allocates multiple pte tables within a single page, and therefore
550# a per-page lock leads to problems when multiple tables need to be locked
551# at the same time (e.g. copy_page_range()).
552# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
553#
554config SPLIT_PTLOCK_CPUS
555 int
556 default "999999" if !MMU
557 default "999999" if ARM && !CPU_CACHE_VIPT
558 default "999999" if PARISC && !PA20
559 default "999999" if SPARC32
560 default "4"
561
562config ARCH_ENABLE_SPLIT_PMD_PTLOCK
563 bool
564
565#
566# support for memory balloon
567config MEMORY_BALLOON
568 bool
569
570#
571# support for memory balloon compaction
572config BALLOON_COMPACTION
573 bool "Allow for balloon memory compaction/migration"
574 def_bool y
575 depends on COMPACTION && MEMORY_BALLOON
576 help
577 Memory fragmentation introduced by ballooning might reduce
578 significantly the number of 2MB contiguous memory blocks that can be
579 used within a guest, thus imposing performance penalties associated
580 with the reduced number of transparent huge pages that could be used
581 by the guest workload. Allowing the compaction & migration for memory
582 pages enlisted as being part of memory balloon devices avoids the
583 scenario aforementioned and helps improving memory defragmentation.
584
585#
586# support for memory compaction
587config COMPACTION
588 bool "Allow for memory compaction"
589 def_bool y
590 select MIGRATION
591 depends on MMU
592 help
593 Compaction is the only memory management component to form
594 high order (larger physically contiguous) memory blocks
595 reliably. The page allocator relies on compaction heavily and
596 the lack of the feature can lead to unexpected OOM killer
597 invocations for high order memory requests. You shouldn't
598 disable this option unless there really is a strong reason for
599 it and then we would be really interested to hear about that at
600 linux-mm@kvack.org.
601
602config COMPACT_UNEVICTABLE_DEFAULT
603 int
604 depends on COMPACTION
605 default 0 if PREEMPT_RT
606 default 1
607
608#
609# support for free page reporting
610config PAGE_REPORTING
611 bool "Free page reporting"
612 def_bool n
613 help
614 Free page reporting allows for the incremental acquisition of
615 free pages from the buddy allocator for the purpose of reporting
616 those pages to another entity, such as a hypervisor, so that the
617 memory can be freed within the host for other uses.
618
619#
620# support for page migration
621#
622config MIGRATION
623 bool "Page migration"
624 def_bool y
625 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
626 help
627 Allows the migration of the physical location of pages of processes
628 while the virtual addresses are not changed. This is useful in
629 two situations. The first is on NUMA systems to put pages nearer
630 to the processors accessing. The second is when allocating huge
631 pages as migration can relocate pages to satisfy a huge page
632 allocation instead of reclaiming.
633
634config DEVICE_MIGRATION
635 def_bool MIGRATION && ZONE_DEVICE
636
637config ARCH_ENABLE_HUGEPAGE_MIGRATION
638 bool
639
640config ARCH_ENABLE_THP_MIGRATION
641 bool
642
643config HUGETLB_PAGE_SIZE_VARIABLE
644 def_bool n
645 help
646 Allows the pageblock_order value to be dynamic instead of just standard
647 HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available
648 on a platform.
649
650 Note that the pageblock_order cannot exceed MAX_ORDER - 1 and will be
651 clamped down to MAX_ORDER - 1.
652
653config CONTIG_ALLOC
654 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
655
656config PHYS_ADDR_T_64BIT
657 def_bool 64BIT
658
659config BOUNCE
660 bool "Enable bounce buffers"
661 default y
662 depends on BLOCK && MMU && HIGHMEM
663 help
664 Enable bounce buffers for devices that cannot access the full range of
665 memory available to the CPU. Enabled by default when HIGHMEM is
666 selected, but you may say n to override this.
667
668config MMU_NOTIFIER
669 bool
670 select SRCU
671 select INTERVAL_TREE
672
673config KSM
674 bool "Enable KSM for page merging"
675 depends on MMU
676 select XXHASH
677 help
678 Enable Kernel Samepage Merging: KSM periodically scans those areas
679 of an application's address space that an app has advised may be
680 mergeable. When it finds pages of identical content, it replaces
681 the many instances by a single page with that content, so
682 saving memory until one or another app needs to modify the content.
683 Recommended for use with KVM, or with other duplicative applications.
684 See Documentation/mm/ksm.rst for more information: KSM is inactive
685 until a program has madvised that an area is MADV_MERGEABLE, and
686 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
687
688config DEFAULT_MMAP_MIN_ADDR
689 int "Low address space to protect from user allocation"
690 depends on MMU
691 default 4096
692 help
693 This is the portion of low virtual memory which should be protected
694 from userspace allocation. Keeping a user from writing to low pages
695 can help reduce the impact of kernel NULL pointer bugs.
696
697 For most ia64, ppc64 and x86 users with lots of address space
698 a value of 65536 is reasonable and should cause no problems.
699 On arm and other archs it should not be higher than 32768.
700 Programs which use vm86 functionality or have some need to map
701 this low address space will need CAP_SYS_RAWIO or disable this
702 protection by setting the value to 0.
703
704 This value can be changed after boot using the
705 /proc/sys/vm/mmap_min_addr tunable.
706
707config ARCH_SUPPORTS_MEMORY_FAILURE
708 bool
709
710config MEMORY_FAILURE
711 depends on MMU
712 depends on ARCH_SUPPORTS_MEMORY_FAILURE
713 bool "Enable recovery from hardware memory errors"
714 select MEMORY_ISOLATION
715 select RAS
716 help
717 Enables code to recover from some memory failures on systems
718 with MCA recovery. This allows a system to continue running
719 even when some of its memory has uncorrected errors. This requires
720 special hardware support and typically ECC memory.
721
722config HWPOISON_INJECT
723 tristate "HWPoison pages injector"
724 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
725 select PROC_PAGE_MONITOR
726
727config NOMMU_INITIAL_TRIM_EXCESS
728 int "Turn on mmap() excess space trimming before booting"
729 depends on !MMU
730 default 1
731 help
732 The NOMMU mmap() frequently needs to allocate large contiguous chunks
733 of memory on which to store mappings, but it can only ask the system
734 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
735 more than it requires. To deal with this, mmap() is able to trim off
736 the excess and return it to the allocator.
737
738 If trimming is enabled, the excess is trimmed off and returned to the
739 system allocator, which can cause extra fragmentation, particularly
740 if there are a lot of transient processes.
741
742 If trimming is disabled, the excess is kept, but not used, which for
743 long-term mappings means that the space is wasted.
744
745 Trimming can be dynamically controlled through a sysctl option
746 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
747 excess pages there must be before trimming should occur, or zero if
748 no trimming is to occur.
749
750 This option specifies the initial value of this option. The default
751 of 1 says that all excess pages should be trimmed.
752
753 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
754
755config ARCH_WANT_GENERAL_HUGETLB
756 bool
757
758config ARCH_WANTS_THP_SWAP
759 def_bool n
760
761menuconfig TRANSPARENT_HUGEPAGE
762 bool "Transparent Hugepage Support"
763 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT
764 select COMPACTION
765 select XARRAY_MULTI
766 help
767 Transparent Hugepages allows the kernel to use huge pages and
768 huge tlb transparently to the applications whenever possible.
769 This feature can improve computing performance to certain
770 applications by speeding up page faults during memory
771 allocation, by reducing the number of tlb misses and by speeding
772 up the pagetable walking.
773
774 If memory constrained on embedded, you may want to say N.
775
776if TRANSPARENT_HUGEPAGE
777
778choice
779 prompt "Transparent Hugepage Support sysfs defaults"
780 depends on TRANSPARENT_HUGEPAGE
781 default TRANSPARENT_HUGEPAGE_ALWAYS
782 help
783 Selects the sysfs defaults for Transparent Hugepage Support.
784
785 config TRANSPARENT_HUGEPAGE_ALWAYS
786 bool "always"
787 help
788 Enabling Transparent Hugepage always, can increase the
789 memory footprint of applications without a guaranteed
790 benefit but it will work automatically for all applications.
791
792 config TRANSPARENT_HUGEPAGE_MADVISE
793 bool "madvise"
794 help
795 Enabling Transparent Hugepage madvise, will only provide a
796 performance improvement benefit to the applications using
797 madvise(MADV_HUGEPAGE) but it won't risk to increase the
798 memory footprint of applications without a guaranteed
799 benefit.
800endchoice
801
802config THP_SWAP
803 def_bool y
804 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT
805 help
806 Swap transparent huge pages in one piece, without splitting.
807 XXX: For now, swap cluster backing transparent huge page
808 will be split after swapout.
809
810 For selection by architectures with reasonable THP sizes.
811
812config READ_ONLY_THP_FOR_FS
813 bool "Read-only THP for filesystems (EXPERIMENTAL)"
814 depends on TRANSPARENT_HUGEPAGE && SHMEM
815
816 help
817 Allow khugepaged to put read-only file-backed pages in THP.
818
819 This is marked experimental because it is a new feature. Write
820 support of file THPs will be developed in the next few release
821 cycles.
822
823endif # TRANSPARENT_HUGEPAGE
824
825#
826# UP and nommu archs use km based percpu allocator
827#
828config NEED_PER_CPU_KM
829 depends on !SMP || !MMU
830 bool
831 default y
832
833config NEED_PER_CPU_EMBED_FIRST_CHUNK
834 bool
835
836config NEED_PER_CPU_PAGE_FIRST_CHUNK
837 bool
838
839config USE_PERCPU_NUMA_NODE_ID
840 bool
841
842config HAVE_SETUP_PER_CPU_AREA
843 bool
844
845config FRONTSWAP
846 bool
847
848config CMA
849 bool "Contiguous Memory Allocator"
850 depends on MMU
851 select MIGRATION
852 select MEMORY_ISOLATION
853 help
854 This enables the Contiguous Memory Allocator which allows other
855 subsystems to allocate big physically-contiguous blocks of memory.
856 CMA reserves a region of memory and allows only movable pages to
857 be allocated from it. This way, the kernel can use the memory for
858 pagecache and when a subsystem requests for contiguous area, the
859 allocated pages are migrated away to serve the contiguous request.
860
861 If unsure, say "n".
862
863config CMA_DEBUG
864 bool "CMA debug messages (DEVELOPMENT)"
865 depends on DEBUG_KERNEL && CMA
866 help
867 Turns on debug messages in CMA. This produces KERN_DEBUG
868 messages for every CMA call as well as various messages while
869 processing calls such as dma_alloc_from_contiguous().
870 This option does not affect warning and error messages.
871
872config CMA_DEBUGFS
873 bool "CMA debugfs interface"
874 depends on CMA && DEBUG_FS
875 help
876 Turns on the DebugFS interface for CMA.
877
878config CMA_SYSFS
879 bool "CMA information through sysfs interface"
880 depends on CMA && SYSFS
881 help
882 This option exposes some sysfs attributes to get information
883 from CMA.
884
885config CMA_AREAS
886 int "Maximum count of the CMA areas"
887 depends on CMA
888 default 19 if NUMA
889 default 7
890 help
891 CMA allows to create CMA areas for particular purpose, mainly,
892 used as device private area. This parameter sets the maximum
893 number of CMA area in the system.
894
895 If unsure, leave the default value "7" in UMA and "19" in NUMA.
896
897config MEM_SOFT_DIRTY
898 bool "Track memory changes"
899 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
900 select PROC_PAGE_MONITOR
901 help
902 This option enables memory changes tracking by introducing a
903 soft-dirty bit on pte-s. This bit it set when someone writes
904 into a page just as regular dirty bit, but unlike the latter
905 it can be cleared by hands.
906
907 See Documentation/admin-guide/mm/soft-dirty.rst for more details.
908
909config GENERIC_EARLY_IOREMAP
910 bool
911
912config STACK_MAX_DEFAULT_SIZE_MB
913 int "Default maximum user stack size for 32-bit processes (MB)"
914 default 100
915 range 8 2048
916 depends on STACK_GROWSUP && (!64BIT || COMPAT)
917 help
918 This is the maximum stack size in Megabytes in the VM layout of 32-bit
919 user processes when the stack grows upwards (currently only on parisc
920 arch) when the RLIMIT_STACK hard limit is unlimited.
921
922 A sane initial value is 100 MB.
923
924config DEFERRED_STRUCT_PAGE_INIT
925 bool "Defer initialisation of struct pages to kthreads"
926 depends on SPARSEMEM
927 depends on !NEED_PER_CPU_KM
928 depends on 64BIT
929 select PADATA
930 help
931 Ordinarily all struct pages are initialised during early boot in a
932 single thread. On very large machines this can take a considerable
933 amount of time. If this option is set, large machines will bring up
934 a subset of memmap at boot and then initialise the rest in parallel.
935 This has a potential performance impact on tasks running early in the
936 lifetime of the system until these kthreads finish the
937 initialisation.
938
939config PAGE_IDLE_FLAG
940 bool
941 select PAGE_EXTENSION if !64BIT
942 help
943 This adds PG_idle and PG_young flags to 'struct page'. PTE Accessed
944 bit writers can set the state of the bit in the flags so that PTE
945 Accessed bit readers may avoid disturbance.
946
947config IDLE_PAGE_TRACKING
948 bool "Enable idle page tracking"
949 depends on SYSFS && MMU
950 select PAGE_IDLE_FLAG
951 help
952 This feature allows to estimate the amount of user pages that have
953 not been touched during a given period of time. This information can
954 be useful to tune memory cgroup limits and/or for job placement
955 within a compute cluster.
956
957 See Documentation/admin-guide/mm/idle_page_tracking.rst for
958 more details.
959
960config ARCH_HAS_CACHE_LINE_SIZE
961 bool
962
963config ARCH_HAS_CURRENT_STACK_POINTER
964 bool
965 help
966 In support of HARDENED_USERCOPY performing stack variable lifetime
967 checking, an architecture-agnostic way to find the stack pointer
968 is needed. Once an architecture defines an unsigned long global
969 register alias named "current_stack_pointer", this config can be
970 selected.
971
972config ARCH_HAS_PTE_DEVMAP
973 bool
974
975config ARCH_HAS_ZONE_DMA_SET
976 bool
977
978config ZONE_DMA
979 bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET
980 default y if ARM64 || X86
981
982config ZONE_DMA32
983 bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET
984 depends on !X86_32
985 default y if ARM64
986
987config ZONE_DEVICE
988 bool "Device memory (pmem, HMM, etc...) hotplug support"
989 depends on MEMORY_HOTPLUG
990 depends on MEMORY_HOTREMOVE
991 depends on SPARSEMEM_VMEMMAP
992 depends on ARCH_HAS_PTE_DEVMAP
993 select XARRAY_MULTI
994
995 help
996 Device memory hotplug support allows for establishing pmem,
997 or other device driver discovered memory regions, in the
998 memmap. This allows pfn_to_page() lookups of otherwise
999 "device-physical" addresses which is needed for using a DAX
1000 mapping in an O_DIRECT operation, among other things.
1001
1002 If FS_DAX is enabled, then say Y.
1003
1004#
1005# Helpers to mirror range of the CPU page tables of a process into device page
1006# tables.
1007#
1008config HMM_MIRROR
1009 bool
1010 depends on MMU
1011
1012config GET_FREE_REGION
1013 depends on SPARSEMEM
1014 bool
1015
1016config DEVICE_PRIVATE
1017 bool "Unaddressable device memory (GPU memory, ...)"
1018 depends on ZONE_DEVICE
1019 select GET_FREE_REGION
1020
1021 help
1022 Allows creation of struct pages to represent unaddressable device
1023 memory; i.e., memory that is only accessible from the device (or
1024 group of devices). You likely also want to select HMM_MIRROR.
1025
1026config VMAP_PFN
1027 bool
1028
1029config ARCH_USES_HIGH_VMA_FLAGS
1030 bool
1031config ARCH_HAS_PKEYS
1032 bool
1033
1034config ARCH_USES_PG_ARCH_X
1035 bool
1036 help
1037 Enable the definition of PG_arch_x page flags with x > 1. Only
1038 suitable for 64-bit architectures with CONFIG_FLATMEM or
1039 CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be
1040 enough room for additional bits in page->flags.
1041
1042config VM_EVENT_COUNTERS
1043 default y
1044 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1045 help
1046 VM event counters are needed for event counts to be shown.
1047 This option allows the disabling of the VM event counters
1048 on EXPERT systems. /proc/vmstat will only show page counts
1049 if VM event counters are disabled.
1050
1051config PERCPU_STATS
1052 bool "Collect percpu memory statistics"
1053 help
1054 This feature collects and exposes statistics via debugfs. The
1055 information includes global and per chunk statistics, which can
1056 be used to help understand percpu memory usage.
1057
1058config GUP_TEST
1059 bool "Enable infrastructure for get_user_pages()-related unit tests"
1060 depends on DEBUG_FS
1061 help
1062 Provides /sys/kernel/debug/gup_test, which in turn provides a way
1063 to make ioctl calls that can launch kernel-based unit tests for
1064 the get_user_pages*() and pin_user_pages*() family of API calls.
1065
1066 These tests include benchmark testing of the _fast variants of
1067 get_user_pages*() and pin_user_pages*(), as well as smoke tests of
1068 the non-_fast variants.
1069
1070 There is also a sub-test that allows running dump_page() on any
1071 of up to eight pages (selected by command line args) within the
1072 range of user-space addresses. These pages are either pinned via
1073 pin_user_pages*(), or pinned via get_user_pages*(), as specified
1074 by other command line arguments.
1075
1076 See tools/testing/selftests/vm/gup_test.c
1077
1078comment "GUP_TEST needs to have DEBUG_FS enabled"
1079 depends on !GUP_TEST && !DEBUG_FS
1080
1081config GUP_GET_PXX_LOW_HIGH
1082 bool
1083
1084config ARCH_HAS_PTE_SPECIAL
1085 bool
1086
1087#
1088# Some architectures require a special hugepage directory format that is
1089# required to support multiple hugepage sizes. For example a4fe3ce76
1090# "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
1091# introduced it on powerpc. This allows for a more flexible hugepage
1092# pagetable layouts.
1093#
1094config ARCH_HAS_HUGEPD
1095 bool
1096
1097config MAPPING_DIRTY_HELPERS
1098 bool
1099
1100config KMAP_LOCAL
1101 bool
1102
1103config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY
1104 bool
1105
1106# struct io_mapping based helper. Selected by drivers that need them
1107config IO_MAPPING
1108 bool
1109
1110config SECRETMEM
1111 default y
1112 bool "Enable memfd_secret() system call" if EXPERT
1113 depends on ARCH_HAS_SET_DIRECT_MAP
1114 help
1115 Enable the memfd_secret() system call with the ability to create
1116 memory areas visible only in the context of the owning process and
1117 not mapped to other processes and other kernel page tables.
1118
1119config ANON_VMA_NAME
1120 bool "Anonymous VMA name support"
1121 depends on PROC_FS && ADVISE_SYSCALLS && MMU
1122
1123 help
1124 Allow naming anonymous virtual memory areas.
1125
1126 This feature allows assigning names to virtual memory areas. Assigned
1127 names can be later retrieved from /proc/pid/maps and /proc/pid/smaps
1128 and help identifying individual anonymous memory areas.
1129 Assigning a name to anonymous virtual memory area might prevent that
1130 area from being merged with adjacent virtual memory areas due to the
1131 difference in their name.
1132
1133config USERFAULTFD
1134 bool "Enable userfaultfd() system call"
1135 depends on MMU
1136 help
1137 Enable the userfaultfd() system call that allows to intercept and
1138 handle page faults in userland.
1139
1140config HAVE_ARCH_USERFAULTFD_WP
1141 bool
1142 help
1143 Arch has userfaultfd write protection support
1144
1145config HAVE_ARCH_USERFAULTFD_MINOR
1146 bool
1147 help
1148 Arch has userfaultfd minor fault support
1149
1150config PTE_MARKER_UFFD_WP
1151 bool "Userfaultfd write protection support for shmem/hugetlbfs"
1152 default y
1153 depends on HAVE_ARCH_USERFAULTFD_WP
1154
1155 help
1156 Allows to create marker PTEs for userfaultfd write protection
1157 purposes. It is required to enable userfaultfd write protection on
1158 file-backed memory types like shmem and hugetlbfs.
1159
1160# multi-gen LRU {
1161config LRU_GEN
1162 bool "Multi-Gen LRU"
1163 depends on MMU
1164 # make sure folio->flags has enough spare bits
1165 depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP
1166 help
1167 A high performance LRU implementation to overcommit memory. See
1168 Documentation/admin-guide/mm/multigen_lru.rst for details.
1169
1170config LRU_GEN_ENABLED
1171 bool "Enable by default"
1172 depends on LRU_GEN
1173 help
1174 This option enables the multi-gen LRU by default.
1175
1176config LRU_GEN_STATS
1177 bool "Full stats for debugging"
1178 depends on LRU_GEN
1179 help
1180 Do not enable this option unless you plan to look at historical stats
1181 from evicted generations for debugging purpose.
1182
1183 This option has a per-memcg and per-node memory overhead.
1184# }
1185
1186source "mm/damon/Kconfig"
1187
1188endmenu
1config SELECT_MEMORY_MODEL
2 def_bool y
3 depends on EXPERIMENTAL || ARCH_SELECT_MEMORY_MODEL
4
5choice
6 prompt "Memory model"
7 depends on SELECT_MEMORY_MODEL
8 default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
9 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
10 default FLATMEM_MANUAL
11
12config FLATMEM_MANUAL
13 bool "Flat Memory"
14 depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
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: FLATMEM. This is normal
19 and a correct option.
20
21 Some users of more advanced features like NUMA and
22 memory hotplug may have different options here.
23 DISCONTIGMEM is an more mature, better tested system,
24 but is incompatible with memory hotplug and may suffer
25 decreased performance over SPARSEMEM. If unsure between
26 "Sparse Memory" and "Discontiguous Memory", choose
27 "Discontiguous Memory".
28
29 If unsure, choose this option (Flat Memory) over any other.
30
31config DISCONTIGMEM_MANUAL
32 bool "Discontiguous Memory"
33 depends on ARCH_DISCONTIGMEM_ENABLE
34 help
35 This option provides enhanced support for discontiguous
36 memory systems, over FLATMEM. These systems have holes
37 in their physical address spaces, and this option provides
38 more efficient handling of these holes. However, the vast
39 majority of hardware has quite flat address spaces, and
40 can have degraded performance from the extra overhead that
41 this option imposes.
42
43 Many NUMA configurations will have this as the only option.
44
45 If unsure, choose "Flat Memory" over this option.
46
47config SPARSEMEM_MANUAL
48 bool "Sparse Memory"
49 depends on ARCH_SPARSEMEM_ENABLE
50 help
51 This will be the only option for some systems, including
52 memory hotplug systems. This is normal.
53
54 For many other systems, this will be an alternative to
55 "Discontiguous Memory". This option provides some potential
56 performance benefits, along with decreased code complexity,
57 but it is newer, and more experimental.
58
59 If unsure, choose "Discontiguous Memory" or "Flat Memory"
60 over this option.
61
62endchoice
63
64config DISCONTIGMEM
65 def_bool y
66 depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
67
68config SPARSEMEM
69 def_bool y
70 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
71
72config FLATMEM
73 def_bool y
74 depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
75
76config FLAT_NODE_MEM_MAP
77 def_bool y
78 depends on !SPARSEMEM
79
80#
81# Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
82# to represent different areas of memory. This variable allows
83# those dependencies to exist individually.
84#
85config NEED_MULTIPLE_NODES
86 def_bool y
87 depends on DISCONTIGMEM || NUMA
88
89config HAVE_MEMORY_PRESENT
90 def_bool y
91 depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
92
93#
94# SPARSEMEM_EXTREME (which is the default) does some bootmem
95# allocations when memory_present() is called. If this cannot
96# be done on your architecture, select this option. However,
97# statically allocating the mem_section[] array can potentially
98# consume vast quantities of .bss, so be careful.
99#
100# This option will also potentially produce smaller runtime code
101# with gcc 3.4 and later.
102#
103config SPARSEMEM_STATIC
104 bool
105
106#
107# Architecture platforms which require a two level mem_section in SPARSEMEM
108# must select this option. This is usually for architecture platforms with
109# an extremely sparse physical address space.
110#
111config SPARSEMEM_EXTREME
112 def_bool y
113 depends on SPARSEMEM && !SPARSEMEM_STATIC
114
115config SPARSEMEM_VMEMMAP_ENABLE
116 bool
117
118config SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
119 def_bool y
120 depends on SPARSEMEM && X86_64
121
122config SPARSEMEM_VMEMMAP
123 bool "Sparse Memory virtual memmap"
124 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
125 default y
126 help
127 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
128 pfn_to_page and page_to_pfn operations. This is the most
129 efficient option when sufficient kernel resources are available.
130
131config HAVE_MEMBLOCK
132 boolean
133
134# eventually, we can have this option just 'select SPARSEMEM'
135config MEMORY_HOTPLUG
136 bool "Allow for memory hot-add"
137 depends on SPARSEMEM || X86_64_ACPI_NUMA
138 depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG
139 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
140
141config MEMORY_HOTPLUG_SPARSE
142 def_bool y
143 depends on SPARSEMEM && MEMORY_HOTPLUG
144
145config MEMORY_HOTREMOVE
146 bool "Allow for memory hot remove"
147 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
148 depends on MIGRATION
149
150#
151# If we have space for more page flags then we can enable additional
152# optimizations and functionality.
153#
154# Regular Sparsemem takes page flag bits for the sectionid if it does not
155# use a virtual memmap. Disable extended page flags for 32 bit platforms
156# that require the use of a sectionid in the page flags.
157#
158config PAGEFLAGS_EXTENDED
159 def_bool y
160 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
161
162# Heavily threaded applications may benefit from splitting the mm-wide
163# page_table_lock, so that faults on different parts of the user address
164# space can be handled with less contention: split it at this NR_CPUS.
165# Default to 4 for wider testing, though 8 might be more appropriate.
166# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
167# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
168# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
169#
170config SPLIT_PTLOCK_CPUS
171 int
172 default "999999" if ARM && !CPU_CACHE_VIPT
173 default "999999" if PARISC && !PA20
174 default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
175 default "4"
176
177#
178# support for memory compaction
179config COMPACTION
180 bool "Allow for memory compaction"
181 select MIGRATION
182 depends on MMU
183 help
184 Allows the compaction of memory for the allocation of huge pages.
185
186#
187# support for page migration
188#
189config MIGRATION
190 bool "Page migration"
191 def_bool y
192 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION
193 help
194 Allows the migration of the physical location of pages of processes
195 while the virtual addresses are not changed. This is useful in
196 two situations. The first is on NUMA systems to put pages nearer
197 to the processors accessing. The second is when allocating huge
198 pages as migration can relocate pages to satisfy a huge page
199 allocation instead of reclaiming.
200
201config PHYS_ADDR_T_64BIT
202 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
203
204config ZONE_DMA_FLAG
205 int
206 default "0" if !ZONE_DMA
207 default "1"
208
209config BOUNCE
210 def_bool y
211 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
212
213config NR_QUICK
214 int
215 depends on QUICKLIST
216 default "2" if AVR32
217 default "1"
218
219config VIRT_TO_BUS
220 def_bool y
221 depends on !ARCH_NO_VIRT_TO_BUS
222
223config MMU_NOTIFIER
224 bool
225
226config KSM
227 bool "Enable KSM for page merging"
228 depends on MMU
229 help
230 Enable Kernel Samepage Merging: KSM periodically scans those areas
231 of an application's address space that an app has advised may be
232 mergeable. When it finds pages of identical content, it replaces
233 the many instances by a single page with that content, so
234 saving memory until one or another app needs to modify the content.
235 Recommended for use with KVM, or with other duplicative applications.
236 See Documentation/vm/ksm.txt for more information: KSM is inactive
237 until a program has madvised that an area is MADV_MERGEABLE, and
238 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
239
240config DEFAULT_MMAP_MIN_ADDR
241 int "Low address space to protect from user allocation"
242 depends on MMU
243 default 4096
244 help
245 This is the portion of low virtual memory which should be protected
246 from userspace allocation. Keeping a user from writing to low pages
247 can help reduce the impact of kernel NULL pointer bugs.
248
249 For most ia64, ppc64 and x86 users with lots of address space
250 a value of 65536 is reasonable and should cause no problems.
251 On arm and other archs it should not be higher than 32768.
252 Programs which use vm86 functionality or have some need to map
253 this low address space will need CAP_SYS_RAWIO or disable this
254 protection by setting the value to 0.
255
256 This value can be changed after boot using the
257 /proc/sys/vm/mmap_min_addr tunable.
258
259config ARCH_SUPPORTS_MEMORY_FAILURE
260 bool
261
262config MEMORY_FAILURE
263 depends on MMU
264 depends on ARCH_SUPPORTS_MEMORY_FAILURE
265 bool "Enable recovery from hardware memory errors"
266 help
267 Enables code to recover from some memory failures on systems
268 with MCA recovery. This allows a system to continue running
269 even when some of its memory has uncorrected errors. This requires
270 special hardware support and typically ECC memory.
271
272config HWPOISON_INJECT
273 tristate "HWPoison pages injector"
274 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
275 select PROC_PAGE_MONITOR
276
277config NOMMU_INITIAL_TRIM_EXCESS
278 int "Turn on mmap() excess space trimming before booting"
279 depends on !MMU
280 default 1
281 help
282 The NOMMU mmap() frequently needs to allocate large contiguous chunks
283 of memory on which to store mappings, but it can only ask the system
284 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
285 more than it requires. To deal with this, mmap() is able to trim off
286 the excess and return it to the allocator.
287
288 If trimming is enabled, the excess is trimmed off and returned to the
289 system allocator, which can cause extra fragmentation, particularly
290 if there are a lot of transient processes.
291
292 If trimming is disabled, the excess is kept, but not used, which for
293 long-term mappings means that the space is wasted.
294
295 Trimming can be dynamically controlled through a sysctl option
296 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
297 excess pages there must be before trimming should occur, or zero if
298 no trimming is to occur.
299
300 This option specifies the initial value of this option. The default
301 of 1 says that all excess pages should be trimmed.
302
303 See Documentation/nommu-mmap.txt for more information.
304
305config TRANSPARENT_HUGEPAGE
306 bool "Transparent Hugepage Support"
307 depends on X86 && MMU
308 select COMPACTION
309 help
310 Transparent Hugepages allows the kernel to use huge pages and
311 huge tlb transparently to the applications whenever possible.
312 This feature can improve computing performance to certain
313 applications by speeding up page faults during memory
314 allocation, by reducing the number of tlb misses and by speeding
315 up the pagetable walking.
316
317 If memory constrained on embedded, you may want to say N.
318
319choice
320 prompt "Transparent Hugepage Support sysfs defaults"
321 depends on TRANSPARENT_HUGEPAGE
322 default TRANSPARENT_HUGEPAGE_ALWAYS
323 help
324 Selects the sysfs defaults for Transparent Hugepage Support.
325
326 config TRANSPARENT_HUGEPAGE_ALWAYS
327 bool "always"
328 help
329 Enabling Transparent Hugepage always, can increase the
330 memory footprint of applications without a guaranteed
331 benefit but it will work automatically for all applications.
332
333 config TRANSPARENT_HUGEPAGE_MADVISE
334 bool "madvise"
335 help
336 Enabling Transparent Hugepage madvise, will only provide a
337 performance improvement benefit to the applications using
338 madvise(MADV_HUGEPAGE) but it won't risk to increase the
339 memory footprint of applications without a guaranteed
340 benefit.
341endchoice
342
343#
344# UP and nommu archs use km based percpu allocator
345#
346config NEED_PER_CPU_KM
347 depends on !SMP
348 bool
349 default y
350
351config CLEANCACHE
352 bool "Enable cleancache driver to cache clean pages if tmem is present"
353 default n
354 help
355 Cleancache can be thought of as a page-granularity victim cache
356 for clean pages that the kernel's pageframe replacement algorithm
357 (PFRA) would like to keep around, but can't since there isn't enough
358 memory. So when the PFRA "evicts" a page, it first attempts to use
359 cleancache code to put the data contained in that page into
360 "transcendent memory", memory that is not directly accessible or
361 addressable by the kernel and is of unknown and possibly
362 time-varying size. And when a cleancache-enabled
363 filesystem wishes to access a page in a file on disk, it first
364 checks cleancache to see if it already contains it; if it does,
365 the page is copied into the kernel and a disk access is avoided.
366 When a transcendent memory driver is available (such as zcache or
367 Xen transcendent memory), a significant I/O reduction
368 may be achieved. When none is available, all cleancache calls
369 are reduced to a single pointer-compare-against-NULL resulting
370 in a negligible performance hit.
371
372 If unsure, say Y to enable cleancache