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1config SELECT_MEMORY_MODEL
2 def_bool y
3 depends on 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 a 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 bool
133
134config HAVE_MEMBLOCK_NODE_MAP
135 bool
136
137config HAVE_MEMBLOCK_PHYS_MAP
138 bool
139
140config HAVE_GENERIC_RCU_GUP
141 bool
142
143config ARCH_DISCARD_MEMBLOCK
144 bool
145
146config NO_BOOTMEM
147 bool
148
149config MEMORY_ISOLATION
150 bool
151
152config MOVABLE_NODE
153 bool "Enable to assign a node which has only movable memory"
154 depends on HAVE_MEMBLOCK
155 depends on NO_BOOTMEM
156 depends on X86_64
157 depends on NUMA
158 default n
159 help
160 Allow a node to have only movable memory. Pages used by the kernel,
161 such as direct mapping pages cannot be migrated. So the corresponding
162 memory device cannot be hotplugged. This option allows the following
163 two things:
164 - When the system is booting, node full of hotpluggable memory can
165 be arranged to have only movable memory so that the whole node can
166 be hot-removed. (need movable_node boot option specified).
167 - After the system is up, the option allows users to online all the
168 memory of a node as movable memory so that the whole node can be
169 hot-removed.
170
171 Users who don't use the memory hotplug feature are fine with this
172 option on since they don't specify movable_node boot option or they
173 don't online memory as movable.
174
175 Say Y here if you want to hotplug a whole node.
176 Say N here if you want kernel to use memory on all nodes evenly.
177
178#
179# Only be set on architectures that have completely implemented memory hotplug
180# feature. If you are not sure, don't touch it.
181#
182config HAVE_BOOTMEM_INFO_NODE
183 def_bool n
184
185# eventually, we can have this option just 'select SPARSEMEM'
186config MEMORY_HOTPLUG
187 bool "Allow for memory hot-add"
188 depends on SPARSEMEM || X86_64_ACPI_NUMA
189 depends on ARCH_ENABLE_MEMORY_HOTPLUG
190
191config MEMORY_HOTPLUG_SPARSE
192 def_bool y
193 depends on SPARSEMEM && MEMORY_HOTPLUG
194
195config MEMORY_HOTREMOVE
196 bool "Allow for memory hot remove"
197 select MEMORY_ISOLATION
198 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
199 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
200 depends on MIGRATION
201
202# Heavily threaded applications may benefit from splitting the mm-wide
203# page_table_lock, so that faults on different parts of the user address
204# space can be handled with less contention: split it at this NR_CPUS.
205# Default to 4 for wider testing, though 8 might be more appropriate.
206# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
207# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
208# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
209#
210config SPLIT_PTLOCK_CPUS
211 int
212 default "999999" if !MMU
213 default "999999" if ARM && !CPU_CACHE_VIPT
214 default "999999" if PARISC && !PA20
215 default "4"
216
217config ARCH_ENABLE_SPLIT_PMD_PTLOCK
218 bool
219
220#
221# support for memory balloon
222config MEMORY_BALLOON
223 bool
224
225#
226# support for memory balloon compaction
227config BALLOON_COMPACTION
228 bool "Allow for balloon memory compaction/migration"
229 def_bool y
230 depends on COMPACTION && MEMORY_BALLOON
231 help
232 Memory fragmentation introduced by ballooning might reduce
233 significantly the number of 2MB contiguous memory blocks that can be
234 used within a guest, thus imposing performance penalties associated
235 with the reduced number of transparent huge pages that could be used
236 by the guest workload. Allowing the compaction & migration for memory
237 pages enlisted as being part of memory balloon devices avoids the
238 scenario aforementioned and helps improving memory defragmentation.
239
240#
241# support for memory compaction
242config COMPACTION
243 bool "Allow for memory compaction"
244 def_bool y
245 select MIGRATION
246 depends on MMU
247 help
248 Allows the compaction of memory for the allocation of huge pages.
249
250#
251# support for page migration
252#
253config MIGRATION
254 bool "Page migration"
255 def_bool y
256 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
257 help
258 Allows the migration of the physical location of pages of processes
259 while the virtual addresses are not changed. This is useful in
260 two situations. The first is on NUMA systems to put pages nearer
261 to the processors accessing. The second is when allocating huge
262 pages as migration can relocate pages to satisfy a huge page
263 allocation instead of reclaiming.
264
265config ARCH_ENABLE_HUGEPAGE_MIGRATION
266 bool
267
268config PHYS_ADDR_T_64BIT
269 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
270
271config ZONE_DMA_FLAG
272 int
273 default "0" if !ZONE_DMA
274 default "1"
275
276config BOUNCE
277 bool "Enable bounce buffers"
278 default y
279 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
280 help
281 Enable bounce buffers for devices that cannot access
282 the full range of memory available to the CPU. Enabled
283 by default when ZONE_DMA or HIGHMEM is selected, but you
284 may say n to override this.
285
286# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
287# have more than 4GB of memory, but we don't currently use the IOTLB to present
288# a 32-bit address to OHCI. So we need to use a bounce pool instead.
289config NEED_BOUNCE_POOL
290 bool
291 default y if TILE && USB_OHCI_HCD
292
293config NR_QUICK
294 int
295 depends on QUICKLIST
296 default "2" if AVR32
297 default "1"
298
299config VIRT_TO_BUS
300 bool
301 help
302 An architecture should select this if it implements the
303 deprecated interface virt_to_bus(). All new architectures
304 should probably not select this.
305
306
307config MMU_NOTIFIER
308 bool
309 select SRCU
310
311config KSM
312 bool "Enable KSM for page merging"
313 depends on MMU
314 help
315 Enable Kernel Samepage Merging: KSM periodically scans those areas
316 of an application's address space that an app has advised may be
317 mergeable. When it finds pages of identical content, it replaces
318 the many instances by a single page with that content, so
319 saving memory until one or another app needs to modify the content.
320 Recommended for use with KVM, or with other duplicative applications.
321 See Documentation/vm/ksm.txt for more information: KSM is inactive
322 until a program has madvised that an area is MADV_MERGEABLE, and
323 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
324
325config DEFAULT_MMAP_MIN_ADDR
326 int "Low address space to protect from user allocation"
327 depends on MMU
328 default 4096
329 help
330 This is the portion of low virtual memory which should be protected
331 from userspace allocation. Keeping a user from writing to low pages
332 can help reduce the impact of kernel NULL pointer bugs.
333
334 For most ia64, ppc64 and x86 users with lots of address space
335 a value of 65536 is reasonable and should cause no problems.
336 On arm and other archs it should not be higher than 32768.
337 Programs which use vm86 functionality or have some need to map
338 this low address space will need CAP_SYS_RAWIO or disable this
339 protection by setting the value to 0.
340
341 This value can be changed after boot using the
342 /proc/sys/vm/mmap_min_addr tunable.
343
344config ARCH_SUPPORTS_MEMORY_FAILURE
345 bool
346
347config MEMORY_FAILURE
348 depends on MMU
349 depends on ARCH_SUPPORTS_MEMORY_FAILURE
350 bool "Enable recovery from hardware memory errors"
351 select MEMORY_ISOLATION
352 select RAS
353 help
354 Enables code to recover from some memory failures on systems
355 with MCA recovery. This allows a system to continue running
356 even when some of its memory has uncorrected errors. This requires
357 special hardware support and typically ECC memory.
358
359config HWPOISON_INJECT
360 tristate "HWPoison pages injector"
361 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
362 select PROC_PAGE_MONITOR
363
364config NOMMU_INITIAL_TRIM_EXCESS
365 int "Turn on mmap() excess space trimming before booting"
366 depends on !MMU
367 default 1
368 help
369 The NOMMU mmap() frequently needs to allocate large contiguous chunks
370 of memory on which to store mappings, but it can only ask the system
371 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
372 more than it requires. To deal with this, mmap() is able to trim off
373 the excess and return it to the allocator.
374
375 If trimming is enabled, the excess is trimmed off and returned to the
376 system allocator, which can cause extra fragmentation, particularly
377 if there are a lot of transient processes.
378
379 If trimming is disabled, the excess is kept, but not used, which for
380 long-term mappings means that the space is wasted.
381
382 Trimming can be dynamically controlled through a sysctl option
383 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
384 excess pages there must be before trimming should occur, or zero if
385 no trimming is to occur.
386
387 This option specifies the initial value of this option. The default
388 of 1 says that all excess pages should be trimmed.
389
390 See Documentation/nommu-mmap.txt for more information.
391
392config TRANSPARENT_HUGEPAGE
393 bool "Transparent Hugepage Support"
394 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
395 select COMPACTION
396 help
397 Transparent Hugepages allows the kernel to use huge pages and
398 huge tlb transparently to the applications whenever possible.
399 This feature can improve computing performance to certain
400 applications by speeding up page faults during memory
401 allocation, by reducing the number of tlb misses and by speeding
402 up the pagetable walking.
403
404 If memory constrained on embedded, you may want to say N.
405
406choice
407 prompt "Transparent Hugepage Support sysfs defaults"
408 depends on TRANSPARENT_HUGEPAGE
409 default TRANSPARENT_HUGEPAGE_ALWAYS
410 help
411 Selects the sysfs defaults for Transparent Hugepage Support.
412
413 config TRANSPARENT_HUGEPAGE_ALWAYS
414 bool "always"
415 help
416 Enabling Transparent Hugepage always, can increase the
417 memory footprint of applications without a guaranteed
418 benefit but it will work automatically for all applications.
419
420 config TRANSPARENT_HUGEPAGE_MADVISE
421 bool "madvise"
422 help
423 Enabling Transparent Hugepage madvise, will only provide a
424 performance improvement benefit to the applications using
425 madvise(MADV_HUGEPAGE) but it won't risk to increase the
426 memory footprint of applications without a guaranteed
427 benefit.
428endchoice
429
430#
431# UP and nommu archs use km based percpu allocator
432#
433config NEED_PER_CPU_KM
434 depends on !SMP
435 bool
436 default y
437
438config CLEANCACHE
439 bool "Enable cleancache driver to cache clean pages if tmem is present"
440 default n
441 help
442 Cleancache can be thought of as a page-granularity victim cache
443 for clean pages that the kernel's pageframe replacement algorithm
444 (PFRA) would like to keep around, but can't since there isn't enough
445 memory. So when the PFRA "evicts" a page, it first attempts to use
446 cleancache code to put the data contained in that page into
447 "transcendent memory", memory that is not directly accessible or
448 addressable by the kernel and is of unknown and possibly
449 time-varying size. And when a cleancache-enabled
450 filesystem wishes to access a page in a file on disk, it first
451 checks cleancache to see if it already contains it; if it does,
452 the page is copied into the kernel and a disk access is avoided.
453 When a transcendent memory driver is available (such as zcache or
454 Xen transcendent memory), a significant I/O reduction
455 may be achieved. When none is available, all cleancache calls
456 are reduced to a single pointer-compare-against-NULL resulting
457 in a negligible performance hit.
458
459 If unsure, say Y to enable cleancache
460
461config FRONTSWAP
462 bool "Enable frontswap to cache swap pages if tmem is present"
463 depends on SWAP
464 default n
465 help
466 Frontswap is so named because it can be thought of as the opposite
467 of a "backing" store for a swap device. The data is stored into
468 "transcendent memory", memory that is not directly accessible or
469 addressable by the kernel and is of unknown and possibly
470 time-varying size. When space in transcendent memory is available,
471 a significant swap I/O reduction may be achieved. When none is
472 available, all frontswap calls are reduced to a single pointer-
473 compare-against-NULL resulting in a negligible performance hit
474 and swap data is stored as normal on the matching swap device.
475
476 If unsure, say Y to enable frontswap.
477
478config CMA
479 bool "Contiguous Memory Allocator"
480 depends on HAVE_MEMBLOCK && MMU
481 select MIGRATION
482 select MEMORY_ISOLATION
483 help
484 This enables the Contiguous Memory Allocator which allows other
485 subsystems to allocate big physically-contiguous blocks of memory.
486 CMA reserves a region of memory and allows only movable pages to
487 be allocated from it. This way, the kernel can use the memory for
488 pagecache and when a subsystem requests for contiguous area, the
489 allocated pages are migrated away to serve the contiguous request.
490
491 If unsure, say "n".
492
493config CMA_DEBUG
494 bool "CMA debug messages (DEVELOPMENT)"
495 depends on DEBUG_KERNEL && CMA
496 help
497 Turns on debug messages in CMA. This produces KERN_DEBUG
498 messages for every CMA call as well as various messages while
499 processing calls such as dma_alloc_from_contiguous().
500 This option does not affect warning and error messages.
501
502config CMA_DEBUGFS
503 bool "CMA debugfs interface"
504 depends on CMA && DEBUG_FS
505 help
506 Turns on the DebugFS interface for CMA.
507
508config CMA_AREAS
509 int "Maximum count of the CMA areas"
510 depends on CMA
511 default 7
512 help
513 CMA allows to create CMA areas for particular purpose, mainly,
514 used as device private area. This parameter sets the maximum
515 number of CMA area in the system.
516
517 If unsure, leave the default value "7".
518
519config MEM_SOFT_DIRTY
520 bool "Track memory changes"
521 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
522 select PROC_PAGE_MONITOR
523 help
524 This option enables memory changes tracking by introducing a
525 soft-dirty bit on pte-s. This bit it set when someone writes
526 into a page just as regular dirty bit, but unlike the latter
527 it can be cleared by hands.
528
529 See Documentation/vm/soft-dirty.txt for more details.
530
531config ZSWAP
532 bool "Compressed cache for swap pages (EXPERIMENTAL)"
533 depends on FRONTSWAP && CRYPTO=y
534 select CRYPTO_LZO
535 select ZPOOL
536 default n
537 help
538 A lightweight compressed cache for swap pages. It takes
539 pages that are in the process of being swapped out and attempts to
540 compress them into a dynamically allocated RAM-based memory pool.
541 This can result in a significant I/O reduction on swap device and,
542 in the case where decompressing from RAM is faster that swap device
543 reads, can also improve workload performance.
544
545 This is marked experimental because it is a new feature (as of
546 v3.11) that interacts heavily with memory reclaim. While these
547 interactions don't cause any known issues on simple memory setups,
548 they have not be fully explored on the large set of potential
549 configurations and workloads that exist.
550
551config ZPOOL
552 tristate "Common API for compressed memory storage"
553 default n
554 help
555 Compressed memory storage API. This allows using either zbud or
556 zsmalloc.
557
558config ZBUD
559 tristate "Low density storage for compressed pages"
560 default n
561 help
562 A special purpose allocator for storing compressed pages.
563 It is designed to store up to two compressed pages per physical
564 page. While this design limits storage density, it has simple and
565 deterministic reclaim properties that make it preferable to a higher
566 density approach when reclaim will be used.
567
568config ZSMALLOC
569 tristate "Memory allocator for compressed pages"
570 depends on MMU
571 default n
572 help
573 zsmalloc is a slab-based memory allocator designed to store
574 compressed RAM pages. zsmalloc uses virtual memory mapping
575 in order to reduce fragmentation. However, this results in a
576 non-standard allocator interface where a handle, not a pointer, is
577 returned by an alloc(). This handle must be mapped in order to
578 access the allocated space.
579
580config PGTABLE_MAPPING
581 bool "Use page table mapping to access object in zsmalloc"
582 depends on ZSMALLOC
583 help
584 By default, zsmalloc uses a copy-based object mapping method to
585 access allocations that span two pages. However, if a particular
586 architecture (ex, ARM) performs VM mapping faster than copying,
587 then you should select this. This causes zsmalloc to use page table
588 mapping rather than copying for object mapping.
589
590 You can check speed with zsmalloc benchmark:
591 https://github.com/spartacus06/zsmapbench
592
593config ZSMALLOC_STAT
594 bool "Export zsmalloc statistics"
595 depends on ZSMALLOC
596 select DEBUG_FS
597 help
598 This option enables code in the zsmalloc to collect various
599 statistics about whats happening in zsmalloc and exports that
600 information to userspace via debugfs.
601 If unsure, say N.
602
603config GENERIC_EARLY_IOREMAP
604 bool
605
606config MAX_STACK_SIZE_MB
607 int "Maximum user stack size for 32-bit processes (MB)"
608 default 80
609 range 8 256 if METAG
610 range 8 2048
611 depends on STACK_GROWSUP && (!64BIT || COMPAT)
612 help
613 This is the maximum stack size in Megabytes in the VM layout of 32-bit
614 user processes when the stack grows upwards (currently only on parisc
615 and metag arch). The stack will be located at the highest memory
616 address minus the given value, unless the RLIMIT_STACK hard limit is
617 changed to a smaller value in which case that is used.
618
619 A sane initial value is 80 MB.
620
621# For architectures that support deferred memory initialisation
622config ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
623 bool
624
625config DEFERRED_STRUCT_PAGE_INIT
626 bool "Defer initialisation of struct pages to kthreads"
627 default n
628 depends on ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
629 depends on MEMORY_HOTPLUG
630 help
631 Ordinarily all struct pages are initialised during early boot in a
632 single thread. On very large machines this can take a considerable
633 amount of time. If this option is set, large machines will bring up
634 a subset of memmap at boot and then initialise the rest in parallel
635 by starting one-off "pgdatinitX" kernel thread for each node X. This
636 has a potential performance impact on processes running early in the
637 lifetime of the system until these kthreads finish the
638 initialisation.
639
640config IDLE_PAGE_TRACKING
641 bool "Enable idle page tracking"
642 depends on SYSFS && MMU
643 select PAGE_EXTENSION if !64BIT
644 help
645 This feature allows to estimate the amount of user pages that have
646 not been touched during a given period of time. This information can
647 be useful to tune memory cgroup limits and/or for job placement
648 within a compute cluster.
649
650 See Documentation/vm/idle_page_tracking.txt for more details.
651
652config ZONE_DEVICE
653 bool "Device memory (pmem, etc...) hotplug support" if EXPERT
654 depends on MEMORY_HOTPLUG
655 depends on MEMORY_HOTREMOVE
656 depends on SPARSEMEM_VMEMMAP
657 depends on X86_64 #arch_add_memory() comprehends device memory
658
659 help
660 Device memory hotplug support allows for establishing pmem,
661 or other device driver discovered memory regions, in the
662 memmap. This allows pfn_to_page() lookups of otherwise
663 "device-physical" addresses which is needed for using a DAX
664 mapping in an O_DIRECT operation, among other things.
665
666 If FS_DAX is enabled, then say Y.
667
668config FRAME_VECTOR
669 bool
670
671config ARCH_USES_HIGH_VMA_FLAGS
672 bool
673config ARCH_HAS_PKEYS
674 bool
1# SPDX-License-Identifier: GPL-2.0-only
2
3menu "Memory Management options"
4
5#
6# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
7# add proper SWAP support to them, in which case this can be remove.
8#
9config ARCH_NO_SWAP
10 bool
11
12config ZPOOL
13 bool
14
15menuconfig SWAP
16 bool "Support for paging of anonymous memory (swap)"
17 depends on MMU && BLOCK && !ARCH_NO_SWAP
18 default y
19 help
20 This option allows you to choose whether you want to have support
21 for so called swap devices or swap files in your kernel that are
22 used to provide more virtual memory than the actual RAM present
23 in your computer. If unsure say Y.
24
25config ZSWAP
26 bool "Compressed cache for swap pages"
27 depends on SWAP
28 select CRYPTO
29 select ZPOOL
30 help
31 A lightweight compressed cache for swap pages. It takes
32 pages that are in the process of being swapped out and attempts to
33 compress them into a dynamically allocated RAM-based memory pool.
34 This can result in a significant I/O reduction on swap device and,
35 in the case where decompressing from RAM is faster than swap device
36 reads, can also improve workload performance.
37
38config ZSWAP_DEFAULT_ON
39 bool "Enable the compressed cache for swap pages by default"
40 depends on ZSWAP
41 help
42 If selected, the compressed cache for swap pages will be enabled
43 at boot, otherwise it will be disabled.
44
45 The selection made here can be overridden by using the kernel
46 command line 'zswap.enabled=' option.
47
48config ZSWAP_SHRINKER_DEFAULT_ON
49 bool "Shrink the zswap pool on memory pressure"
50 depends on ZSWAP
51 default n
52 help
53 If selected, the zswap shrinker will be enabled, and the pages
54 stored in the zswap pool will become available for reclaim (i.e
55 written back to the backing swap device) on memory pressure.
56
57 This means that zswap writeback could happen even if the pool is
58 not yet full, or the cgroup zswap limit has not been reached,
59 reducing the chance that cold pages will reside in the zswap pool
60 and consume memory indefinitely.
61
62choice
63 prompt "Default compressor"
64 depends on ZSWAP
65 default ZSWAP_COMPRESSOR_DEFAULT_LZO
66 help
67 Selects the default compression algorithm for the compressed cache
68 for swap pages.
69
70 For an overview what kind of performance can be expected from
71 a particular compression algorithm please refer to the benchmarks
72 available at the following LWN page:
73 https://lwn.net/Articles/751795/
74
75 If in doubt, select 'LZO'.
76
77 The selection made here can be overridden by using the kernel
78 command line 'zswap.compressor=' option.
79
80config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
81 bool "Deflate"
82 select CRYPTO_DEFLATE
83 help
84 Use the Deflate algorithm as the default compression algorithm.
85
86config ZSWAP_COMPRESSOR_DEFAULT_LZO
87 bool "LZO"
88 select CRYPTO_LZO
89 help
90 Use the LZO algorithm as the default compression algorithm.
91
92config ZSWAP_COMPRESSOR_DEFAULT_842
93 bool "842"
94 select CRYPTO_842
95 help
96 Use the 842 algorithm as the default compression algorithm.
97
98config ZSWAP_COMPRESSOR_DEFAULT_LZ4
99 bool "LZ4"
100 select CRYPTO_LZ4
101 help
102 Use the LZ4 algorithm as the default compression algorithm.
103
104config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
105 bool "LZ4HC"
106 select CRYPTO_LZ4HC
107 help
108 Use the LZ4HC algorithm as the default compression algorithm.
109
110config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
111 bool "zstd"
112 select CRYPTO_ZSTD
113 help
114 Use the zstd algorithm as the default compression algorithm.
115endchoice
116
117config ZSWAP_COMPRESSOR_DEFAULT
118 string
119 depends on ZSWAP
120 default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
121 default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
122 default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
123 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
124 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
125 default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
126 default ""
127
128choice
129 prompt "Default allocator"
130 depends on ZSWAP
131 default ZSWAP_ZPOOL_DEFAULT_ZSMALLOC if MMU
132 default ZSWAP_ZPOOL_DEFAULT_ZBUD
133 help
134 Selects the default allocator for the compressed cache for
135 swap pages.
136 The default is 'zbud' for compatibility, however please do
137 read the description of each of the allocators below before
138 making a right choice.
139
140 The selection made here can be overridden by using the kernel
141 command line 'zswap.zpool=' option.
142
143config ZSWAP_ZPOOL_DEFAULT_ZBUD
144 bool "zbud"
145 select ZBUD
146 help
147 Use the zbud allocator as the default allocator.
148
149config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
150 bool "z3fold"
151 select Z3FOLD
152 help
153 Use the z3fold allocator as the default allocator.
154
155config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
156 bool "zsmalloc"
157 select ZSMALLOC
158 help
159 Use the zsmalloc allocator as the default allocator.
160endchoice
161
162config ZSWAP_ZPOOL_DEFAULT
163 string
164 depends on ZSWAP
165 default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
166 default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
167 default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
168 default ""
169
170config ZBUD
171 tristate "2:1 compression allocator (zbud)"
172 depends on ZSWAP
173 help
174 A special purpose allocator for storing compressed pages.
175 It is designed to store up to two compressed pages per physical
176 page. While this design limits storage density, it has simple and
177 deterministic reclaim properties that make it preferable to a higher
178 density approach when reclaim will be used.
179
180config Z3FOLD
181 tristate "3:1 compression allocator (z3fold)"
182 depends on ZSWAP
183 help
184 A special purpose allocator for storing compressed pages.
185 It is designed to store up to three compressed pages per physical
186 page. It is a ZBUD derivative so the simplicity and determinism are
187 still there.
188
189config ZSMALLOC
190 tristate
191 prompt "N:1 compression allocator (zsmalloc)" if ZSWAP
192 depends on MMU
193 help
194 zsmalloc is a slab-based memory allocator designed to store
195 pages of various compression levels efficiently. It achieves
196 the highest storage density with the least amount of fragmentation.
197
198config ZSMALLOC_STAT
199 bool "Export zsmalloc statistics"
200 depends on ZSMALLOC
201 select DEBUG_FS
202 help
203 This option enables code in the zsmalloc to collect various
204 statistics about what's happening in zsmalloc and exports that
205 information to userspace via debugfs.
206 If unsure, say N.
207
208config ZSMALLOC_CHAIN_SIZE
209 int "Maximum number of physical pages per-zspage"
210 default 8
211 range 4 16
212 depends on ZSMALLOC
213 help
214 This option sets the upper limit on the number of physical pages
215 that a zmalloc page (zspage) can consist of. The optimal zspage
216 chain size is calculated for each size class during the
217 initialization of the pool.
218
219 Changing this option can alter the characteristics of size classes,
220 such as the number of pages per zspage and the number of objects
221 per zspage. This can also result in different configurations of
222 the pool, as zsmalloc merges size classes with similar
223 characteristics.
224
225 For more information, see zsmalloc documentation.
226
227menu "Slab allocator options"
228
229config SLUB
230 def_bool y
231
232config SLUB_TINY
233 bool "Configure for minimal memory footprint"
234 depends on EXPERT
235 select SLAB_MERGE_DEFAULT
236 help
237 Configures the slab allocator in a way to achieve minimal memory
238 footprint, sacrificing scalability, debugging and other features.
239 This is intended only for the smallest system that had used the
240 SLOB allocator and is not recommended for systems with more than
241 16MB RAM.
242
243 If unsure, say N.
244
245config SLAB_MERGE_DEFAULT
246 bool "Allow slab caches to be merged"
247 default y
248 help
249 For reduced kernel memory fragmentation, slab caches can be
250 merged when they share the same size and other characteristics.
251 This carries a risk of kernel heap overflows being able to
252 overwrite objects from merged caches (and more easily control
253 cache layout), which makes such heap attacks easier to exploit
254 by attackers. By keeping caches unmerged, these kinds of exploits
255 can usually only damage objects in the same cache. To disable
256 merging at runtime, "slab_nomerge" can be passed on the kernel
257 command line.
258
259config SLAB_FREELIST_RANDOM
260 bool "Randomize slab freelist"
261 depends on !SLUB_TINY
262 help
263 Randomizes the freelist order used on creating new pages. This
264 security feature reduces the predictability of the kernel slab
265 allocator against heap overflows.
266
267config SLAB_FREELIST_HARDENED
268 bool "Harden slab freelist metadata"
269 depends on !SLUB_TINY
270 help
271 Many kernel heap attacks try to target slab cache metadata and
272 other infrastructure. This options makes minor performance
273 sacrifices to harden the kernel slab allocator against common
274 freelist exploit methods.
275
276config SLUB_STATS
277 default n
278 bool "Enable performance statistics"
279 depends on SYSFS && !SLUB_TINY
280 help
281 The statistics are useful to debug slab allocation behavior in
282 order find ways to optimize the allocator. This should never be
283 enabled for production use since keeping statistics slows down
284 the allocator by a few percentage points. The slabinfo command
285 supports the determination of the most active slabs to figure
286 out which slabs are relevant to a particular load.
287 Try running: slabinfo -DA
288
289config SLUB_CPU_PARTIAL
290 default y
291 depends on SMP && !SLUB_TINY
292 bool "Enable per cpu partial caches"
293 help
294 Per cpu partial caches accelerate objects allocation and freeing
295 that is local to a processor at the price of more indeterminism
296 in the latency of the free. On overflow these caches will be cleared
297 which requires the taking of locks that may cause latency spikes.
298 Typically one would choose no for a realtime system.
299
300config RANDOM_KMALLOC_CACHES
301 default n
302 depends on !SLUB_TINY
303 bool "Randomize slab caches for normal kmalloc"
304 help
305 A hardening feature that creates multiple copies of slab caches for
306 normal kmalloc allocation and makes kmalloc randomly pick one based
307 on code address, which makes the attackers more difficult to spray
308 vulnerable memory objects on the heap for the purpose of exploiting
309 memory vulnerabilities.
310
311 Currently the number of copies is set to 16, a reasonably large value
312 that effectively diverges the memory objects allocated for different
313 subsystems or modules into different caches, at the expense of a
314 limited degree of memory and CPU overhead that relates to hardware and
315 system workload.
316
317endmenu # Slab allocator options
318
319config SHUFFLE_PAGE_ALLOCATOR
320 bool "Page allocator randomization"
321 default SLAB_FREELIST_RANDOM && ACPI_NUMA
322 help
323 Randomization of the page allocator improves the average
324 utilization of a direct-mapped memory-side-cache. See section
325 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
326 6.2a specification for an example of how a platform advertises
327 the presence of a memory-side-cache. There are also incidental
328 security benefits as it reduces the predictability of page
329 allocations to compliment SLAB_FREELIST_RANDOM, but the
330 default granularity of shuffling on the MAX_PAGE_ORDER i.e, 10th
331 order of pages is selected based on cache utilization benefits
332 on x86.
333
334 While the randomization improves cache utilization it may
335 negatively impact workloads on platforms without a cache. For
336 this reason, by default, the randomization is enabled only
337 after runtime detection of a direct-mapped memory-side-cache.
338 Otherwise, the randomization may be force enabled with the
339 'page_alloc.shuffle' kernel command line parameter.
340
341 Say Y if unsure.
342
343config COMPAT_BRK
344 bool "Disable heap randomization"
345 default y
346 help
347 Randomizing heap placement makes heap exploits harder, but it
348 also breaks ancient binaries (including anything libc5 based).
349 This option changes the bootup default to heap randomization
350 disabled, and can be overridden at runtime by setting
351 /proc/sys/kernel/randomize_va_space to 2.
352
353 On non-ancient distros (post-2000 ones) N is usually a safe choice.
354
355config MMAP_ALLOW_UNINITIALIZED
356 bool "Allow mmapped anonymous memory to be uninitialized"
357 depends on EXPERT && !MMU
358 default n
359 help
360 Normally, and according to the Linux spec, anonymous memory obtained
361 from mmap() has its contents cleared before it is passed to
362 userspace. Enabling this config option allows you to request that
363 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
364 providing a huge performance boost. If this option is not enabled,
365 then the flag will be ignored.
366
367 This is taken advantage of by uClibc's malloc(), and also by
368 ELF-FDPIC binfmt's brk and stack allocator.
369
370 Because of the obvious security issues, this option should only be
371 enabled on embedded devices where you control what is run in
372 userspace. Since that isn't generally a problem on no-MMU systems,
373 it is normally safe to say Y here.
374
375 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
376
377config SELECT_MEMORY_MODEL
378 def_bool y
379 depends on ARCH_SELECT_MEMORY_MODEL
380
381choice
382 prompt "Memory model"
383 depends on SELECT_MEMORY_MODEL
384 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
385 default FLATMEM_MANUAL
386 help
387 This option allows you to change some of the ways that
388 Linux manages its memory internally. Most users will
389 only have one option here selected by the architecture
390 configuration. This is normal.
391
392config FLATMEM_MANUAL
393 bool "Flat Memory"
394 depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE
395 help
396 This option is best suited for non-NUMA systems with
397 flat address space. The FLATMEM is the most efficient
398 system in terms of performance and resource consumption
399 and it is the best option for smaller systems.
400
401 For systems that have holes in their physical address
402 spaces and for features like NUMA and memory hotplug,
403 choose "Sparse Memory".
404
405 If unsure, choose this option (Flat Memory) over any other.
406
407config SPARSEMEM_MANUAL
408 bool "Sparse Memory"
409 depends on ARCH_SPARSEMEM_ENABLE
410 help
411 This will be the only option for some systems, including
412 memory hot-plug systems. This is normal.
413
414 This option provides efficient support for systems with
415 holes is their physical address space and allows memory
416 hot-plug and hot-remove.
417
418 If unsure, choose "Flat Memory" over this option.
419
420endchoice
421
422config SPARSEMEM
423 def_bool y
424 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
425
426config FLATMEM
427 def_bool y
428 depends on !SPARSEMEM || FLATMEM_MANUAL
429
430#
431# SPARSEMEM_EXTREME (which is the default) does some bootmem
432# allocations when sparse_init() is called. If this cannot
433# be done on your architecture, select this option. However,
434# statically allocating the mem_section[] array can potentially
435# consume vast quantities of .bss, so be careful.
436#
437# This option will also potentially produce smaller runtime code
438# with gcc 3.4 and later.
439#
440config SPARSEMEM_STATIC
441 bool
442
443#
444# Architecture platforms which require a two level mem_section in SPARSEMEM
445# must select this option. This is usually for architecture platforms with
446# an extremely sparse physical address space.
447#
448config SPARSEMEM_EXTREME
449 def_bool y
450 depends on SPARSEMEM && !SPARSEMEM_STATIC
451
452config SPARSEMEM_VMEMMAP_ENABLE
453 bool
454
455config SPARSEMEM_VMEMMAP
456 bool "Sparse Memory virtual memmap"
457 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
458 default y
459 help
460 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
461 pfn_to_page and page_to_pfn operations. This is the most
462 efficient option when sufficient kernel resources are available.
463#
464# Select this config option from the architecture Kconfig, if it is preferred
465# to enable the feature of HugeTLB/dev_dax vmemmap optimization.
466#
467config ARCH_WANT_OPTIMIZE_DAX_VMEMMAP
468 bool
469
470config ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP
471 bool
472
473config HAVE_MEMBLOCK_PHYS_MAP
474 bool
475
476config HAVE_FAST_GUP
477 depends on MMU
478 bool
479
480# Don't discard allocated memory used to track "memory" and "reserved" memblocks
481# after early boot, so it can still be used to test for validity of memory.
482# Also, memblocks are updated with memory hot(un)plug.
483config ARCH_KEEP_MEMBLOCK
484 bool
485
486# Keep arch NUMA mapping infrastructure post-init.
487config NUMA_KEEP_MEMINFO
488 bool
489
490config MEMORY_ISOLATION
491 bool
492
493# IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked
494# IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via
495# /dev/mem.
496config EXCLUSIVE_SYSTEM_RAM
497 def_bool y
498 depends on !DEVMEM || STRICT_DEVMEM
499
500#
501# Only be set on architectures that have completely implemented memory hotplug
502# feature. If you are not sure, don't touch it.
503#
504config HAVE_BOOTMEM_INFO_NODE
505 def_bool n
506
507config ARCH_ENABLE_MEMORY_HOTPLUG
508 bool
509
510config ARCH_ENABLE_MEMORY_HOTREMOVE
511 bool
512
513# eventually, we can have this option just 'select SPARSEMEM'
514menuconfig MEMORY_HOTPLUG
515 bool "Memory hotplug"
516 select MEMORY_ISOLATION
517 depends on SPARSEMEM
518 depends on ARCH_ENABLE_MEMORY_HOTPLUG
519 depends on 64BIT
520 select NUMA_KEEP_MEMINFO if NUMA
521
522if MEMORY_HOTPLUG
523
524config MEMORY_HOTPLUG_DEFAULT_ONLINE
525 bool "Online the newly added memory blocks by default"
526 depends on MEMORY_HOTPLUG
527 help
528 This option sets the default policy setting for memory hotplug
529 onlining policy (/sys/devices/system/memory/auto_online_blocks) which
530 determines what happens to newly added memory regions. Policy setting
531 can always be changed at runtime.
532 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
533
534 Say Y here if you want all hot-plugged memory blocks to appear in
535 'online' state by default.
536 Say N here if you want the default policy to keep all hot-plugged
537 memory blocks in 'offline' state.
538
539config MEMORY_HOTREMOVE
540 bool "Allow for memory hot remove"
541 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
542 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
543 depends on MIGRATION
544
545config MHP_MEMMAP_ON_MEMORY
546 def_bool y
547 depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
548 depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
549
550endif # MEMORY_HOTPLUG
551
552config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
553 bool
554
555# Heavily threaded applications may benefit from splitting the mm-wide
556# page_table_lock, so that faults on different parts of the user address
557# space can be handled with less contention: split it at this NR_CPUS.
558# Default to 4 for wider testing, though 8 might be more appropriate.
559# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
560# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
561# SPARC32 allocates multiple pte tables within a single page, and therefore
562# a per-page lock leads to problems when multiple tables need to be locked
563# at the same time (e.g. copy_page_range()).
564# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
565#
566config SPLIT_PTLOCK_CPUS
567 int
568 default "999999" if !MMU
569 default "999999" if ARM && !CPU_CACHE_VIPT
570 default "999999" if PARISC && !PA20
571 default "999999" if SPARC32
572 default "4"
573
574config ARCH_ENABLE_SPLIT_PMD_PTLOCK
575 bool
576
577#
578# support for memory balloon
579config MEMORY_BALLOON
580 bool
581
582#
583# support for memory balloon compaction
584config BALLOON_COMPACTION
585 bool "Allow for balloon memory compaction/migration"
586 default y
587 depends on COMPACTION && MEMORY_BALLOON
588 help
589 Memory fragmentation introduced by ballooning might reduce
590 significantly the number of 2MB contiguous memory blocks that can be
591 used within a guest, thus imposing performance penalties associated
592 with the reduced number of transparent huge pages that could be used
593 by the guest workload. Allowing the compaction & migration for memory
594 pages enlisted as being part of memory balloon devices avoids the
595 scenario aforementioned and helps improving memory defragmentation.
596
597#
598# support for memory compaction
599config COMPACTION
600 bool "Allow for memory compaction"
601 default y
602 select MIGRATION
603 depends on MMU
604 help
605 Compaction is the only memory management component to form
606 high order (larger physically contiguous) memory blocks
607 reliably. The page allocator relies on compaction heavily and
608 the lack of the feature can lead to unexpected OOM killer
609 invocations for high order memory requests. You shouldn't
610 disable this option unless there really is a strong reason for
611 it and then we would be really interested to hear about that at
612 linux-mm@kvack.org.
613
614config COMPACT_UNEVICTABLE_DEFAULT
615 int
616 depends on COMPACTION
617 default 0 if PREEMPT_RT
618 default 1
619
620#
621# support for free page reporting
622config PAGE_REPORTING
623 bool "Free page reporting"
624 help
625 Free page reporting allows for the incremental acquisition of
626 free pages from the buddy allocator for the purpose of reporting
627 those pages to another entity, such as a hypervisor, so that the
628 memory can be freed within the host for other uses.
629
630#
631# support for page migration
632#
633config MIGRATION
634 bool "Page migration"
635 default y
636 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
637 help
638 Allows the migration of the physical location of pages of processes
639 while the virtual addresses are not changed. This is useful in
640 two situations. The first is on NUMA systems to put pages nearer
641 to the processors accessing. The second is when allocating huge
642 pages as migration can relocate pages to satisfy a huge page
643 allocation instead of reclaiming.
644
645config DEVICE_MIGRATION
646 def_bool MIGRATION && ZONE_DEVICE
647
648config ARCH_ENABLE_HUGEPAGE_MIGRATION
649 bool
650
651config ARCH_ENABLE_THP_MIGRATION
652 bool
653
654config HUGETLB_PAGE_SIZE_VARIABLE
655 def_bool n
656 help
657 Allows the pageblock_order value to be dynamic instead of just standard
658 HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available
659 on a platform.
660
661 Note that the pageblock_order cannot exceed MAX_PAGE_ORDER and will be
662 clamped down to MAX_PAGE_ORDER.
663
664config CONTIG_ALLOC
665 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
666
667config PCP_BATCH_SCALE_MAX
668 int "Maximum scale factor of PCP (Per-CPU pageset) batch allocate/free"
669 default 5
670 range 0 6
671 help
672 In page allocator, PCP (Per-CPU pageset) is refilled and drained in
673 batches. The batch number is scaled automatically to improve page
674 allocation/free throughput. But too large scale factor may hurt
675 latency. This option sets the upper limit of scale factor to limit
676 the maximum latency.
677
678config PHYS_ADDR_T_64BIT
679 def_bool 64BIT
680
681config BOUNCE
682 bool "Enable bounce buffers"
683 default y
684 depends on BLOCK && MMU && HIGHMEM
685 help
686 Enable bounce buffers for devices that cannot access the full range of
687 memory available to the CPU. Enabled by default when HIGHMEM is
688 selected, but you may say n to override this.
689
690config MMU_NOTIFIER
691 bool
692 select INTERVAL_TREE
693
694config KSM
695 bool "Enable KSM for page merging"
696 depends on MMU
697 select XXHASH
698 help
699 Enable Kernel Samepage Merging: KSM periodically scans those areas
700 of an application's address space that an app has advised may be
701 mergeable. When it finds pages of identical content, it replaces
702 the many instances by a single page with that content, so
703 saving memory until one or another app needs to modify the content.
704 Recommended for use with KVM, or with other duplicative applications.
705 See Documentation/mm/ksm.rst for more information: KSM is inactive
706 until a program has madvised that an area is MADV_MERGEABLE, and
707 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
708
709config DEFAULT_MMAP_MIN_ADDR
710 int "Low address space to protect from user allocation"
711 depends on MMU
712 default 4096
713 help
714 This is the portion of low virtual memory which should be protected
715 from userspace allocation. Keeping a user from writing to low pages
716 can help reduce the impact of kernel NULL pointer bugs.
717
718 For most ppc64 and x86 users with lots of address space
719 a value of 65536 is reasonable and should cause no problems.
720 On arm and other archs it should not be higher than 32768.
721 Programs which use vm86 functionality or have some need to map
722 this low address space will need CAP_SYS_RAWIO or disable this
723 protection by setting the value to 0.
724
725 This value can be changed after boot using the
726 /proc/sys/vm/mmap_min_addr tunable.
727
728config ARCH_SUPPORTS_MEMORY_FAILURE
729 bool
730
731config MEMORY_FAILURE
732 depends on MMU
733 depends on ARCH_SUPPORTS_MEMORY_FAILURE
734 bool "Enable recovery from hardware memory errors"
735 select MEMORY_ISOLATION
736 select RAS
737 help
738 Enables code to recover from some memory failures on systems
739 with MCA recovery. This allows a system to continue running
740 even when some of its memory has uncorrected errors. This requires
741 special hardware support and typically ECC memory.
742
743config HWPOISON_INJECT
744 tristate "HWPoison pages injector"
745 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
746 select PROC_PAGE_MONITOR
747
748config NOMMU_INITIAL_TRIM_EXCESS
749 int "Turn on mmap() excess space trimming before booting"
750 depends on !MMU
751 default 1
752 help
753 The NOMMU mmap() frequently needs to allocate large contiguous chunks
754 of memory on which to store mappings, but it can only ask the system
755 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
756 more than it requires. To deal with this, mmap() is able to trim off
757 the excess and return it to the allocator.
758
759 If trimming is enabled, the excess is trimmed off and returned to the
760 system allocator, which can cause extra fragmentation, particularly
761 if there are a lot of transient processes.
762
763 If trimming is disabled, the excess is kept, but not used, which for
764 long-term mappings means that the space is wasted.
765
766 Trimming can be dynamically controlled through a sysctl option
767 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
768 excess pages there must be before trimming should occur, or zero if
769 no trimming is to occur.
770
771 This option specifies the initial value of this option. The default
772 of 1 says that all excess pages should be trimmed.
773
774 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
775
776config ARCH_WANT_GENERAL_HUGETLB
777 bool
778
779config ARCH_WANTS_THP_SWAP
780 def_bool n
781
782menuconfig TRANSPARENT_HUGEPAGE
783 bool "Transparent Hugepage Support"
784 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT
785 select COMPACTION
786 select XARRAY_MULTI
787 help
788 Transparent Hugepages allows the kernel to use huge pages and
789 huge tlb transparently to the applications whenever possible.
790 This feature can improve computing performance to certain
791 applications by speeding up page faults during memory
792 allocation, by reducing the number of tlb misses and by speeding
793 up the pagetable walking.
794
795 If memory constrained on embedded, you may want to say N.
796
797if TRANSPARENT_HUGEPAGE
798
799choice
800 prompt "Transparent Hugepage Support sysfs defaults"
801 depends on TRANSPARENT_HUGEPAGE
802 default TRANSPARENT_HUGEPAGE_ALWAYS
803 help
804 Selects the sysfs defaults for Transparent Hugepage Support.
805
806 config TRANSPARENT_HUGEPAGE_ALWAYS
807 bool "always"
808 help
809 Enabling Transparent Hugepage always, can increase the
810 memory footprint of applications without a guaranteed
811 benefit but it will work automatically for all applications.
812
813 config TRANSPARENT_HUGEPAGE_MADVISE
814 bool "madvise"
815 help
816 Enabling Transparent Hugepage madvise, will only provide a
817 performance improvement benefit to the applications using
818 madvise(MADV_HUGEPAGE) but it won't risk to increase the
819 memory footprint of applications without a guaranteed
820 benefit.
821
822 config TRANSPARENT_HUGEPAGE_NEVER
823 bool "never"
824 help
825 Disable Transparent Hugepage by default. It can still be
826 enabled at runtime via sysfs.
827endchoice
828
829config THP_SWAP
830 def_bool y
831 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT
832 help
833 Swap transparent huge pages in one piece, without splitting.
834 XXX: For now, swap cluster backing transparent huge page
835 will be split after swapout.
836
837 For selection by architectures with reasonable THP sizes.
838
839config READ_ONLY_THP_FOR_FS
840 bool "Read-only THP for filesystems (EXPERIMENTAL)"
841 depends on TRANSPARENT_HUGEPAGE && SHMEM
842
843 help
844 Allow khugepaged to put read-only file-backed pages in THP.
845
846 This is marked experimental because it is a new feature. Write
847 support of file THPs will be developed in the next few release
848 cycles.
849
850endif # TRANSPARENT_HUGEPAGE
851
852#
853# UP and nommu archs use km based percpu allocator
854#
855config NEED_PER_CPU_KM
856 depends on !SMP || !MMU
857 bool
858 default y
859
860config NEED_PER_CPU_EMBED_FIRST_CHUNK
861 bool
862
863config NEED_PER_CPU_PAGE_FIRST_CHUNK
864 bool
865
866config USE_PERCPU_NUMA_NODE_ID
867 bool
868
869config HAVE_SETUP_PER_CPU_AREA
870 bool
871
872config CMA
873 bool "Contiguous Memory Allocator"
874 depends on MMU
875 select MIGRATION
876 select MEMORY_ISOLATION
877 help
878 This enables the Contiguous Memory Allocator which allows other
879 subsystems to allocate big physically-contiguous blocks of memory.
880 CMA reserves a region of memory and allows only movable pages to
881 be allocated from it. This way, the kernel can use the memory for
882 pagecache and when a subsystem requests for contiguous area, the
883 allocated pages are migrated away to serve the contiguous request.
884
885 If unsure, say "n".
886
887config CMA_DEBUGFS
888 bool "CMA debugfs interface"
889 depends on CMA && DEBUG_FS
890 help
891 Turns on the DebugFS interface for CMA.
892
893config CMA_SYSFS
894 bool "CMA information through sysfs interface"
895 depends on CMA && SYSFS
896 help
897 This option exposes some sysfs attributes to get information
898 from CMA.
899
900config CMA_AREAS
901 int "Maximum count of the CMA areas"
902 depends on CMA
903 default 20 if NUMA
904 default 8
905 help
906 CMA allows to create CMA areas for particular purpose, mainly,
907 used as device private area. This parameter sets the maximum
908 number of CMA area in the system.
909
910 If unsure, leave the default value "8" in UMA and "20" in NUMA.
911
912config MEM_SOFT_DIRTY
913 bool "Track memory changes"
914 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
915 select PROC_PAGE_MONITOR
916 help
917 This option enables memory changes tracking by introducing a
918 soft-dirty bit on pte-s. This bit it set when someone writes
919 into a page just as regular dirty bit, but unlike the latter
920 it can be cleared by hands.
921
922 See Documentation/admin-guide/mm/soft-dirty.rst for more details.
923
924config GENERIC_EARLY_IOREMAP
925 bool
926
927config STACK_MAX_DEFAULT_SIZE_MB
928 int "Default maximum user stack size for 32-bit processes (MB)"
929 default 100
930 range 8 2048
931 depends on STACK_GROWSUP && (!64BIT || COMPAT)
932 help
933 This is the maximum stack size in Megabytes in the VM layout of 32-bit
934 user processes when the stack grows upwards (currently only on parisc
935 arch) when the RLIMIT_STACK hard limit is unlimited.
936
937 A sane initial value is 100 MB.
938
939config DEFERRED_STRUCT_PAGE_INIT
940 bool "Defer initialisation of struct pages to kthreads"
941 depends on SPARSEMEM
942 depends on !NEED_PER_CPU_KM
943 depends on 64BIT
944 select PADATA
945 help
946 Ordinarily all struct pages are initialised during early boot in a
947 single thread. On very large machines this can take a considerable
948 amount of time. If this option is set, large machines will bring up
949 a subset of memmap at boot and then initialise the rest in parallel.
950 This has a potential performance impact on tasks running early in the
951 lifetime of the system until these kthreads finish the
952 initialisation.
953
954config PAGE_IDLE_FLAG
955 bool
956 select PAGE_EXTENSION if !64BIT
957 help
958 This adds PG_idle and PG_young flags to 'struct page'. PTE Accessed
959 bit writers can set the state of the bit in the flags so that PTE
960 Accessed bit readers may avoid disturbance.
961
962config IDLE_PAGE_TRACKING
963 bool "Enable idle page tracking"
964 depends on SYSFS && MMU
965 select PAGE_IDLE_FLAG
966 help
967 This feature allows to estimate the amount of user pages that have
968 not been touched during a given period of time. This information can
969 be useful to tune memory cgroup limits and/or for job placement
970 within a compute cluster.
971
972 See Documentation/admin-guide/mm/idle_page_tracking.rst for
973 more details.
974
975# Architectures which implement cpu_dcache_is_aliasing() to query
976# whether the data caches are aliased (VIVT or VIPT with dcache
977# aliasing) need to select this.
978config ARCH_HAS_CPU_CACHE_ALIASING
979 bool
980
981config ARCH_HAS_CACHE_LINE_SIZE
982 bool
983
984config ARCH_HAS_CURRENT_STACK_POINTER
985 bool
986 help
987 In support of HARDENED_USERCOPY performing stack variable lifetime
988 checking, an architecture-agnostic way to find the stack pointer
989 is needed. Once an architecture defines an unsigned long global
990 register alias named "current_stack_pointer", this config can be
991 selected.
992
993config ARCH_HAS_PTE_DEVMAP
994 bool
995
996config ARCH_HAS_ZONE_DMA_SET
997 bool
998
999config ZONE_DMA
1000 bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET
1001 default y if ARM64 || X86
1002
1003config ZONE_DMA32
1004 bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET
1005 depends on !X86_32
1006 default y if ARM64
1007
1008config ZONE_DEVICE
1009 bool "Device memory (pmem, HMM, etc...) hotplug support"
1010 depends on MEMORY_HOTPLUG
1011 depends on MEMORY_HOTREMOVE
1012 depends on SPARSEMEM_VMEMMAP
1013 depends on ARCH_HAS_PTE_DEVMAP
1014 select XARRAY_MULTI
1015
1016 help
1017 Device memory hotplug support allows for establishing pmem,
1018 or other device driver discovered memory regions, in the
1019 memmap. This allows pfn_to_page() lookups of otherwise
1020 "device-physical" addresses which is needed for using a DAX
1021 mapping in an O_DIRECT operation, among other things.
1022
1023 If FS_DAX is enabled, then say Y.
1024
1025#
1026# Helpers to mirror range of the CPU page tables of a process into device page
1027# tables.
1028#
1029config HMM_MIRROR
1030 bool
1031 depends on MMU
1032
1033config GET_FREE_REGION
1034 depends on SPARSEMEM
1035 bool
1036
1037config DEVICE_PRIVATE
1038 bool "Unaddressable device memory (GPU memory, ...)"
1039 depends on ZONE_DEVICE
1040 select GET_FREE_REGION
1041
1042 help
1043 Allows creation of struct pages to represent unaddressable device
1044 memory; i.e., memory that is only accessible from the device (or
1045 group of devices). You likely also want to select HMM_MIRROR.
1046
1047config VMAP_PFN
1048 bool
1049
1050config ARCH_USES_HIGH_VMA_FLAGS
1051 bool
1052config ARCH_HAS_PKEYS
1053 bool
1054
1055config ARCH_USES_PG_ARCH_X
1056 bool
1057 help
1058 Enable the definition of PG_arch_x page flags with x > 1. Only
1059 suitable for 64-bit architectures with CONFIG_FLATMEM or
1060 CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be
1061 enough room for additional bits in page->flags.
1062
1063config VM_EVENT_COUNTERS
1064 default y
1065 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1066 help
1067 VM event counters are needed for event counts to be shown.
1068 This option allows the disabling of the VM event counters
1069 on EXPERT systems. /proc/vmstat will only show page counts
1070 if VM event counters are disabled.
1071
1072config PERCPU_STATS
1073 bool "Collect percpu memory statistics"
1074 help
1075 This feature collects and exposes statistics via debugfs. The
1076 information includes global and per chunk statistics, which can
1077 be used to help understand percpu memory usage.
1078
1079config GUP_TEST
1080 bool "Enable infrastructure for get_user_pages()-related unit tests"
1081 depends on DEBUG_FS
1082 help
1083 Provides /sys/kernel/debug/gup_test, which in turn provides a way
1084 to make ioctl calls that can launch kernel-based unit tests for
1085 the get_user_pages*() and pin_user_pages*() family of API calls.
1086
1087 These tests include benchmark testing of the _fast variants of
1088 get_user_pages*() and pin_user_pages*(), as well as smoke tests of
1089 the non-_fast variants.
1090
1091 There is also a sub-test that allows running dump_page() on any
1092 of up to eight pages (selected by command line args) within the
1093 range of user-space addresses. These pages are either pinned via
1094 pin_user_pages*(), or pinned via get_user_pages*(), as specified
1095 by other command line arguments.
1096
1097 See tools/testing/selftests/mm/gup_test.c
1098
1099comment "GUP_TEST needs to have DEBUG_FS enabled"
1100 depends on !GUP_TEST && !DEBUG_FS
1101
1102config GUP_GET_PXX_LOW_HIGH
1103 bool
1104
1105config DMAPOOL_TEST
1106 tristate "Enable a module to run time tests on dma_pool"
1107 depends on HAS_DMA
1108 help
1109 Provides a test module that will allocate and free many blocks of
1110 various sizes and report how long it takes. This is intended to
1111 provide a consistent way to measure how changes to the
1112 dma_pool_alloc/free routines affect performance.
1113
1114config ARCH_HAS_PTE_SPECIAL
1115 bool
1116
1117#
1118# Some architectures require a special hugepage directory format that is
1119# required to support multiple hugepage sizes. For example a4fe3ce76
1120# "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
1121# introduced it on powerpc. This allows for a more flexible hugepage
1122# pagetable layouts.
1123#
1124config ARCH_HAS_HUGEPD
1125 bool
1126
1127config MAPPING_DIRTY_HELPERS
1128 bool
1129
1130config KMAP_LOCAL
1131 bool
1132
1133config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY
1134 bool
1135
1136# struct io_mapping based helper. Selected by drivers that need them
1137config IO_MAPPING
1138 bool
1139
1140config MEMFD_CREATE
1141 bool "Enable memfd_create() system call" if EXPERT
1142
1143config SECRETMEM
1144 default y
1145 bool "Enable memfd_secret() system call" if EXPERT
1146 depends on ARCH_HAS_SET_DIRECT_MAP
1147 help
1148 Enable the memfd_secret() system call with the ability to create
1149 memory areas visible only in the context of the owning process and
1150 not mapped to other processes and other kernel page tables.
1151
1152config ANON_VMA_NAME
1153 bool "Anonymous VMA name support"
1154 depends on PROC_FS && ADVISE_SYSCALLS && MMU
1155
1156 help
1157 Allow naming anonymous virtual memory areas.
1158
1159 This feature allows assigning names to virtual memory areas. Assigned
1160 names can be later retrieved from /proc/pid/maps and /proc/pid/smaps
1161 and help identifying individual anonymous memory areas.
1162 Assigning a name to anonymous virtual memory area might prevent that
1163 area from being merged with adjacent virtual memory areas due to the
1164 difference in their name.
1165
1166config HAVE_ARCH_USERFAULTFD_WP
1167 bool
1168 help
1169 Arch has userfaultfd write protection support
1170
1171config HAVE_ARCH_USERFAULTFD_MINOR
1172 bool
1173 help
1174 Arch has userfaultfd minor fault support
1175
1176menuconfig USERFAULTFD
1177 bool "Enable userfaultfd() system call"
1178 depends on MMU
1179 help
1180 Enable the userfaultfd() system call that allows to intercept and
1181 handle page faults in userland.
1182
1183if USERFAULTFD
1184config PTE_MARKER_UFFD_WP
1185 bool "Userfaultfd write protection support for shmem/hugetlbfs"
1186 default y
1187 depends on HAVE_ARCH_USERFAULTFD_WP
1188
1189 help
1190 Allows to create marker PTEs for userfaultfd write protection
1191 purposes. It is required to enable userfaultfd write protection on
1192 file-backed memory types like shmem and hugetlbfs.
1193endif # USERFAULTFD
1194
1195# multi-gen LRU {
1196config LRU_GEN
1197 bool "Multi-Gen LRU"
1198 depends on MMU
1199 # make sure folio->flags has enough spare bits
1200 depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP
1201 help
1202 A high performance LRU implementation to overcommit memory. See
1203 Documentation/admin-guide/mm/multigen_lru.rst for details.
1204
1205config LRU_GEN_ENABLED
1206 bool "Enable by default"
1207 depends on LRU_GEN
1208 help
1209 This option enables the multi-gen LRU by default.
1210
1211config LRU_GEN_STATS
1212 bool "Full stats for debugging"
1213 depends on LRU_GEN
1214 help
1215 Do not enable this option unless you plan to look at historical stats
1216 from evicted generations for debugging purpose.
1217
1218 This option has a per-memcg and per-node memory overhead.
1219
1220config LRU_GEN_WALKS_MMU
1221 def_bool y
1222 depends on LRU_GEN && ARCH_HAS_HW_PTE_YOUNG
1223# }
1224
1225config ARCH_SUPPORTS_PER_VMA_LOCK
1226 def_bool n
1227
1228config PER_VMA_LOCK
1229 def_bool y
1230 depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP
1231 help
1232 Allow per-vma locking during page fault handling.
1233
1234 This feature allows locking each virtual memory area separately when
1235 handling page faults instead of taking mmap_lock.
1236
1237config LOCK_MM_AND_FIND_VMA
1238 bool
1239 depends on !STACK_GROWSUP
1240
1241config IOMMU_MM_DATA
1242 bool
1243
1244source "mm/damon/Kconfig"
1245
1246endmenu