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1# SPDX-License-Identifier: GPL-2.0-only
2
3menu "Memory Management options"
4
5config SELECT_MEMORY_MODEL
6 def_bool y
7 depends on ARCH_SELECT_MEMORY_MODEL
8
9choice
10 prompt "Memory model"
11 depends on SELECT_MEMORY_MODEL
12 default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
13 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
14 default FLATMEM_MANUAL
15 help
16 This option allows you to change some of the ways that
17 Linux manages its memory internally. Most users will
18 only have one option here selected by the architecture
19 configuration. This is normal.
20
21config FLATMEM_MANUAL
22 bool "Flat Memory"
23 depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
24 help
25 This option is best suited for non-NUMA systems with
26 flat address space. The FLATMEM is the most efficient
27 system in terms of performance and resource consumption
28 and it is the best option for smaller systems.
29
30 For systems that have holes in their physical address
31 spaces and for features like NUMA and memory hotplug,
32 choose "Sparse Memory"
33
34 If unsure, choose this option (Flat Memory) over any other.
35
36config DISCONTIGMEM_MANUAL
37 bool "Discontiguous Memory"
38 depends on ARCH_DISCONTIGMEM_ENABLE
39 help
40 This option provides enhanced support for discontiguous
41 memory systems, over FLATMEM. These systems have holes
42 in their physical address spaces, and this option provides
43 more efficient handling of these holes.
44
45 Although "Discontiguous Memory" is still used by several
46 architectures, it is considered deprecated in favor of
47 "Sparse Memory".
48
49 If unsure, choose "Sparse Memory" over this option.
50
51config SPARSEMEM_MANUAL
52 bool "Sparse Memory"
53 depends on ARCH_SPARSEMEM_ENABLE
54 help
55 This will be the only option for some systems, including
56 memory hot-plug systems. This is normal.
57
58 This option provides efficient support for systems with
59 holes is their physical address space and allows memory
60 hot-plug and hot-remove.
61
62 If unsure, choose "Flat Memory" over this option.
63
64endchoice
65
66config DISCONTIGMEM
67 def_bool y
68 depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
69
70config SPARSEMEM
71 def_bool y
72 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
73
74config FLATMEM
75 def_bool y
76 depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
77
78config FLAT_NODE_MEM_MAP
79 def_bool y
80 depends on !SPARSEMEM
81
82#
83# Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
84# to represent different areas of memory. This variable allows
85# those dependencies to exist individually.
86#
87config NEED_MULTIPLE_NODES
88 def_bool y
89 depends on DISCONTIGMEM || NUMA
90
91config HAVE_MEMORY_PRESENT
92 def_bool y
93 depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
94
95#
96# SPARSEMEM_EXTREME (which is the default) does some bootmem
97# allocations when memory_present() is called. If this cannot
98# be done on your architecture, select this option. However,
99# statically allocating the mem_section[] array can potentially
100# consume vast quantities of .bss, so be careful.
101#
102# This option will also potentially produce smaller runtime code
103# with gcc 3.4 and later.
104#
105config SPARSEMEM_STATIC
106 bool
107
108#
109# Architecture platforms which require a two level mem_section in SPARSEMEM
110# must select this option. This is usually for architecture platforms with
111# an extremely sparse physical address space.
112#
113config SPARSEMEM_EXTREME
114 def_bool y
115 depends on SPARSEMEM && !SPARSEMEM_STATIC
116
117config SPARSEMEM_VMEMMAP_ENABLE
118 bool
119
120config SPARSEMEM_VMEMMAP
121 bool "Sparse Memory virtual memmap"
122 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
123 default y
124 help
125 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
126 pfn_to_page and page_to_pfn operations. This is the most
127 efficient option when sufficient kernel resources are available.
128
129config HAVE_MEMBLOCK_NODE_MAP
130 bool
131
132config HAVE_MEMBLOCK_PHYS_MAP
133 bool
134
135config HAVE_FAST_GUP
136 depends on MMU
137 bool
138
139config ARCH_KEEP_MEMBLOCK
140 bool
141
142config MEMORY_ISOLATION
143 bool
144
145#
146# Only be set on architectures that have completely implemented memory hotplug
147# feature. If you are not sure, don't touch it.
148#
149config HAVE_BOOTMEM_INFO_NODE
150 def_bool n
151
152# eventually, we can have this option just 'select SPARSEMEM'
153config MEMORY_HOTPLUG
154 bool "Allow for memory hot-add"
155 depends on SPARSEMEM || X86_64_ACPI_NUMA
156 depends on ARCH_ENABLE_MEMORY_HOTPLUG
157
158config MEMORY_HOTPLUG_SPARSE
159 def_bool y
160 depends on SPARSEMEM && MEMORY_HOTPLUG
161
162config MEMORY_HOTPLUG_DEFAULT_ONLINE
163 bool "Online the newly added memory blocks by default"
164 depends on MEMORY_HOTPLUG
165 help
166 This option sets the default policy setting for memory hotplug
167 onlining policy (/sys/devices/system/memory/auto_online_blocks) which
168 determines what happens to newly added memory regions. Policy setting
169 can always be changed at runtime.
170 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
171
172 Say Y here if you want all hot-plugged memory blocks to appear in
173 'online' state by default.
174 Say N here if you want the default policy to keep all hot-plugged
175 memory blocks in 'offline' state.
176
177config MEMORY_HOTREMOVE
178 bool "Allow for memory hot remove"
179 select MEMORY_ISOLATION
180 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
181 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
182 depends on MIGRATION
183
184# Heavily threaded applications may benefit from splitting the mm-wide
185# page_table_lock, so that faults on different parts of the user address
186# space can be handled with less contention: split it at this NR_CPUS.
187# Default to 4 for wider testing, though 8 might be more appropriate.
188# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
189# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
190# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
191#
192config SPLIT_PTLOCK_CPUS
193 int
194 default "999999" if !MMU
195 default "999999" if ARM && !CPU_CACHE_VIPT
196 default "999999" if PARISC && !PA20
197 default "4"
198
199config ARCH_ENABLE_SPLIT_PMD_PTLOCK
200 bool
201
202#
203# support for memory balloon
204config MEMORY_BALLOON
205 bool
206
207#
208# support for memory balloon compaction
209config BALLOON_COMPACTION
210 bool "Allow for balloon memory compaction/migration"
211 def_bool y
212 depends on COMPACTION && MEMORY_BALLOON
213 help
214 Memory fragmentation introduced by ballooning might reduce
215 significantly the number of 2MB contiguous memory blocks that can be
216 used within a guest, thus imposing performance penalties associated
217 with the reduced number of transparent huge pages that could be used
218 by the guest workload. Allowing the compaction & migration for memory
219 pages enlisted as being part of memory balloon devices avoids the
220 scenario aforementioned and helps improving memory defragmentation.
221
222#
223# support for memory compaction
224config COMPACTION
225 bool "Allow for memory compaction"
226 def_bool y
227 select MIGRATION
228 depends on MMU
229 help
230 Compaction is the only memory management component to form
231 high order (larger physically contiguous) memory blocks
232 reliably. The page allocator relies on compaction heavily and
233 the lack of the feature can lead to unexpected OOM killer
234 invocations for high order memory requests. You shouldn't
235 disable this option unless there really is a strong reason for
236 it and then we would be really interested to hear about that at
237 linux-mm@kvack.org.
238
239#
240# support for page migration
241#
242config MIGRATION
243 bool "Page migration"
244 def_bool y
245 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
246 help
247 Allows the migration of the physical location of pages of processes
248 while the virtual addresses are not changed. This is useful in
249 two situations. The first is on NUMA systems to put pages nearer
250 to the processors accessing. The second is when allocating huge
251 pages as migration can relocate pages to satisfy a huge page
252 allocation instead of reclaiming.
253
254config ARCH_ENABLE_HUGEPAGE_MIGRATION
255 bool
256
257config ARCH_ENABLE_THP_MIGRATION
258 bool
259
260config CONTIG_ALLOC
261 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
262
263config PHYS_ADDR_T_64BIT
264 def_bool 64BIT
265
266config BOUNCE
267 bool "Enable bounce buffers"
268 default y
269 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
270 help
271 Enable bounce buffers for devices that cannot access
272 the full range of memory available to the CPU. Enabled
273 by default when ZONE_DMA or HIGHMEM is selected, but you
274 may say n to override this.
275
276config VIRT_TO_BUS
277 bool
278 help
279 An architecture should select this if it implements the
280 deprecated interface virt_to_bus(). All new architectures
281 should probably not select this.
282
283
284config MMU_NOTIFIER
285 bool
286 select SRCU
287
288config KSM
289 bool "Enable KSM for page merging"
290 depends on MMU
291 select XXHASH
292 help
293 Enable Kernel Samepage Merging: KSM periodically scans those areas
294 of an application's address space that an app has advised may be
295 mergeable. When it finds pages of identical content, it replaces
296 the many instances by a single page with that content, so
297 saving memory until one or another app needs to modify the content.
298 Recommended for use with KVM, or with other duplicative applications.
299 See Documentation/vm/ksm.rst for more information: KSM is inactive
300 until a program has madvised that an area is MADV_MERGEABLE, and
301 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
302
303config DEFAULT_MMAP_MIN_ADDR
304 int "Low address space to protect from user allocation"
305 depends on MMU
306 default 4096
307 help
308 This is the portion of low virtual memory which should be protected
309 from userspace allocation. Keeping a user from writing to low pages
310 can help reduce the impact of kernel NULL pointer bugs.
311
312 For most ia64, ppc64 and x86 users with lots of address space
313 a value of 65536 is reasonable and should cause no problems.
314 On arm and other archs it should not be higher than 32768.
315 Programs which use vm86 functionality or have some need to map
316 this low address space will need CAP_SYS_RAWIO or disable this
317 protection by setting the value to 0.
318
319 This value can be changed after boot using the
320 /proc/sys/vm/mmap_min_addr tunable.
321
322config ARCH_SUPPORTS_MEMORY_FAILURE
323 bool
324
325config MEMORY_FAILURE
326 depends on MMU
327 depends on ARCH_SUPPORTS_MEMORY_FAILURE
328 bool "Enable recovery from hardware memory errors"
329 select MEMORY_ISOLATION
330 select RAS
331 help
332 Enables code to recover from some memory failures on systems
333 with MCA recovery. This allows a system to continue running
334 even when some of its memory has uncorrected errors. This requires
335 special hardware support and typically ECC memory.
336
337config HWPOISON_INJECT
338 tristate "HWPoison pages injector"
339 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
340 select PROC_PAGE_MONITOR
341
342config NOMMU_INITIAL_TRIM_EXCESS
343 int "Turn on mmap() excess space trimming before booting"
344 depends on !MMU
345 default 1
346 help
347 The NOMMU mmap() frequently needs to allocate large contiguous chunks
348 of memory on which to store mappings, but it can only ask the system
349 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
350 more than it requires. To deal with this, mmap() is able to trim off
351 the excess and return it to the allocator.
352
353 If trimming is enabled, the excess is trimmed off and returned to the
354 system allocator, which can cause extra fragmentation, particularly
355 if there are a lot of transient processes.
356
357 If trimming is disabled, the excess is kept, but not used, which for
358 long-term mappings means that the space is wasted.
359
360 Trimming can be dynamically controlled through a sysctl option
361 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
362 excess pages there must be before trimming should occur, or zero if
363 no trimming is to occur.
364
365 This option specifies the initial value of this option. The default
366 of 1 says that all excess pages should be trimmed.
367
368 See Documentation/nommu-mmap.txt for more information.
369
370config TRANSPARENT_HUGEPAGE
371 bool "Transparent Hugepage Support"
372 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
373 select COMPACTION
374 select XARRAY_MULTI
375 help
376 Transparent Hugepages allows the kernel to use huge pages and
377 huge tlb transparently to the applications whenever possible.
378 This feature can improve computing performance to certain
379 applications by speeding up page faults during memory
380 allocation, by reducing the number of tlb misses and by speeding
381 up the pagetable walking.
382
383 If memory constrained on embedded, you may want to say N.
384
385choice
386 prompt "Transparent Hugepage Support sysfs defaults"
387 depends on TRANSPARENT_HUGEPAGE
388 default TRANSPARENT_HUGEPAGE_ALWAYS
389 help
390 Selects the sysfs defaults for Transparent Hugepage Support.
391
392 config TRANSPARENT_HUGEPAGE_ALWAYS
393 bool "always"
394 help
395 Enabling Transparent Hugepage always, can increase the
396 memory footprint of applications without a guaranteed
397 benefit but it will work automatically for all applications.
398
399 config TRANSPARENT_HUGEPAGE_MADVISE
400 bool "madvise"
401 help
402 Enabling Transparent Hugepage madvise, will only provide a
403 performance improvement benefit to the applications using
404 madvise(MADV_HUGEPAGE) but it won't risk to increase the
405 memory footprint of applications without a guaranteed
406 benefit.
407endchoice
408
409config ARCH_WANTS_THP_SWAP
410 def_bool n
411
412config THP_SWAP
413 def_bool y
414 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
415 help
416 Swap transparent huge pages in one piece, without splitting.
417 XXX: For now, swap cluster backing transparent huge page
418 will be split after swapout.
419
420 For selection by architectures with reasonable THP sizes.
421
422config TRANSPARENT_HUGE_PAGECACHE
423 def_bool y
424 depends on TRANSPARENT_HUGEPAGE
425
426#
427# UP and nommu archs use km based percpu allocator
428#
429config NEED_PER_CPU_KM
430 depends on !SMP
431 bool
432 default y
433
434config CLEANCACHE
435 bool "Enable cleancache driver to cache clean pages if tmem is present"
436 help
437 Cleancache can be thought of as a page-granularity victim cache
438 for clean pages that the kernel's pageframe replacement algorithm
439 (PFRA) would like to keep around, but can't since there isn't enough
440 memory. So when the PFRA "evicts" a page, it first attempts to use
441 cleancache code to put the data contained in that page into
442 "transcendent memory", memory that is not directly accessible or
443 addressable by the kernel and is of unknown and possibly
444 time-varying size. And when a cleancache-enabled
445 filesystem wishes to access a page in a file on disk, it first
446 checks cleancache to see if it already contains it; if it does,
447 the page is copied into the kernel and a disk access is avoided.
448 When a transcendent memory driver is available (such as zcache or
449 Xen transcendent memory), a significant I/O reduction
450 may be achieved. When none is available, all cleancache calls
451 are reduced to a single pointer-compare-against-NULL resulting
452 in a negligible performance hit.
453
454 If unsure, say Y to enable cleancache
455
456config FRONTSWAP
457 bool "Enable frontswap to cache swap pages if tmem is present"
458 depends on SWAP
459 help
460 Frontswap is so named because it can be thought of as the opposite
461 of a "backing" store for a swap device. The data is stored into
462 "transcendent memory", memory that is not directly accessible or
463 addressable by the kernel and is of unknown and possibly
464 time-varying size. When space in transcendent memory is available,
465 a significant swap I/O reduction may be achieved. When none is
466 available, all frontswap calls are reduced to a single pointer-
467 compare-against-NULL resulting in a negligible performance hit
468 and swap data is stored as normal on the matching swap device.
469
470 If unsure, say Y to enable frontswap.
471
472config CMA
473 bool "Contiguous Memory Allocator"
474 depends on MMU
475 select MIGRATION
476 select MEMORY_ISOLATION
477 help
478 This enables the Contiguous Memory Allocator which allows other
479 subsystems to allocate big physically-contiguous blocks of memory.
480 CMA reserves a region of memory and allows only movable pages to
481 be allocated from it. This way, the kernel can use the memory for
482 pagecache and when a subsystem requests for contiguous area, the
483 allocated pages are migrated away to serve the contiguous request.
484
485 If unsure, say "n".
486
487config CMA_DEBUG
488 bool "CMA debug messages (DEVELOPMENT)"
489 depends on DEBUG_KERNEL && CMA
490 help
491 Turns on debug messages in CMA. This produces KERN_DEBUG
492 messages for every CMA call as well as various messages while
493 processing calls such as dma_alloc_from_contiguous().
494 This option does not affect warning and error messages.
495
496config CMA_DEBUGFS
497 bool "CMA debugfs interface"
498 depends on CMA && DEBUG_FS
499 help
500 Turns on the DebugFS interface for CMA.
501
502config CMA_AREAS
503 int "Maximum count of the CMA areas"
504 depends on CMA
505 default 7
506 help
507 CMA allows to create CMA areas for particular purpose, mainly,
508 used as device private area. This parameter sets the maximum
509 number of CMA area in the system.
510
511 If unsure, leave the default value "7".
512
513config MEM_SOFT_DIRTY
514 bool "Track memory changes"
515 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
516 select PROC_PAGE_MONITOR
517 help
518 This option enables memory changes tracking by introducing a
519 soft-dirty bit on pte-s. This bit it set when someone writes
520 into a page just as regular dirty bit, but unlike the latter
521 it can be cleared by hands.
522
523 See Documentation/admin-guide/mm/soft-dirty.rst for more details.
524
525config ZSWAP
526 bool "Compressed cache for swap pages (EXPERIMENTAL)"
527 depends on FRONTSWAP && CRYPTO=y
528 select CRYPTO_LZO
529 select ZPOOL
530 help
531 A lightweight compressed cache for swap pages. It takes
532 pages that are in the process of being swapped out and attempts to
533 compress them into a dynamically allocated RAM-based memory pool.
534 This can result in a significant I/O reduction on swap device and,
535 in the case where decompressing from RAM is faster that swap device
536 reads, can also improve workload performance.
537
538 This is marked experimental because it is a new feature (as of
539 v3.11) that interacts heavily with memory reclaim. While these
540 interactions don't cause any known issues on simple memory setups,
541 they have not be fully explored on the large set of potential
542 configurations and workloads that exist.
543
544config ZPOOL
545 tristate "Common API for compressed memory storage"
546 help
547 Compressed memory storage API. This allows using either zbud or
548 zsmalloc.
549
550config ZBUD
551 tristate "Low (Up to 2x) density storage for compressed pages"
552 help
553 A special purpose allocator for storing compressed pages.
554 It is designed to store up to two compressed pages per physical
555 page. While this design limits storage density, it has simple and
556 deterministic reclaim properties that make it preferable to a higher
557 density approach when reclaim will be used.
558
559config Z3FOLD
560 tristate "Up to 3x density storage for compressed pages"
561 depends on ZPOOL
562 help
563 A special purpose allocator for storing compressed pages.
564 It is designed to store up to three compressed pages per physical
565 page. It is a ZBUD derivative so the simplicity and determinism are
566 still there.
567
568config ZSMALLOC
569 tristate "Memory allocator for compressed pages"
570 depends on MMU
571 help
572 zsmalloc is a slab-based memory allocator designed to store
573 compressed RAM pages. zsmalloc uses virtual memory mapping
574 in order to reduce fragmentation. However, this results in a
575 non-standard allocator interface where a handle, not a pointer, is
576 returned by an alloc(). This handle must be mapped in order to
577 access the allocated space.
578
579config PGTABLE_MAPPING
580 bool "Use page table mapping to access object in zsmalloc"
581 depends on ZSMALLOC
582 help
583 By default, zsmalloc uses a copy-based object mapping method to
584 access allocations that span two pages. However, if a particular
585 architecture (ex, ARM) performs VM mapping faster than copying,
586 then you should select this. This causes zsmalloc to use page table
587 mapping rather than copying for object mapping.
588
589 You can check speed with zsmalloc benchmark:
590 https://github.com/spartacus06/zsmapbench
591
592config ZSMALLOC_STAT
593 bool "Export zsmalloc statistics"
594 depends on ZSMALLOC
595 select DEBUG_FS
596 help
597 This option enables code in the zsmalloc to collect various
598 statistics about whats happening in zsmalloc and exports that
599 information to userspace via debugfs.
600 If unsure, say N.
601
602config GENERIC_EARLY_IOREMAP
603 bool
604
605config MAX_STACK_SIZE_MB
606 int "Maximum user stack size for 32-bit processes (MB)"
607 default 80
608 range 8 2048
609 depends on STACK_GROWSUP && (!64BIT || COMPAT)
610 help
611 This is the maximum stack size in Megabytes in the VM layout of 32-bit
612 user processes when the stack grows upwards (currently only on parisc
613 arch). The stack will be located at the highest memory address minus
614 the given value, unless the RLIMIT_STACK hard limit is changed to a
615 smaller value in which case that is used.
616
617 A sane initial value is 80 MB.
618
619config DEFERRED_STRUCT_PAGE_INIT
620 bool "Defer initialisation of struct pages to kthreads"
621 depends on SPARSEMEM
622 depends on !NEED_PER_CPU_KM
623 depends on 64BIT
624 help
625 Ordinarily all struct pages are initialised during early boot in a
626 single thread. On very large machines this can take a considerable
627 amount of time. If this option is set, large machines will bring up
628 a subset of memmap at boot and then initialise the rest in parallel
629 by starting one-off "pgdatinitX" kernel thread for each node X. This
630 has a potential performance impact on processes running early in the
631 lifetime of the system until these kthreads finish the
632 initialisation.
633
634config IDLE_PAGE_TRACKING
635 bool "Enable idle page tracking"
636 depends on SYSFS && MMU
637 select PAGE_EXTENSION if !64BIT
638 help
639 This feature allows to estimate the amount of user pages that have
640 not been touched during a given period of time. This information can
641 be useful to tune memory cgroup limits and/or for job placement
642 within a compute cluster.
643
644 See Documentation/admin-guide/mm/idle_page_tracking.rst for
645 more details.
646
647config ARCH_HAS_PTE_DEVMAP
648 bool
649
650config ZONE_DEVICE
651 bool "Device memory (pmem, HMM, etc...) hotplug support"
652 depends on MEMORY_HOTPLUG
653 depends on MEMORY_HOTREMOVE
654 depends on SPARSEMEM_VMEMMAP
655 depends on ARCH_HAS_PTE_DEVMAP
656 select XARRAY_MULTI
657
658 help
659 Device memory hotplug support allows for establishing pmem,
660 or other device driver discovered memory regions, in the
661 memmap. This allows pfn_to_page() lookups of otherwise
662 "device-physical" addresses which is needed for using a DAX
663 mapping in an O_DIRECT operation, among other things.
664
665 If FS_DAX is enabled, then say Y.
666
667config DEV_PAGEMAP_OPS
668 bool
669
670#
671# Helpers to mirror range of the CPU page tables of a process into device page
672# tables.
673#
674config HMM_MIRROR
675 bool
676 depends on MMU
677 depends on MMU_NOTIFIER
678
679config DEVICE_PRIVATE
680 bool "Unaddressable device memory (GPU memory, ...)"
681 depends on ZONE_DEVICE
682 select DEV_PAGEMAP_OPS
683
684 help
685 Allows creation of struct pages to represent unaddressable device
686 memory; i.e., memory that is only accessible from the device (or
687 group of devices). You likely also want to select HMM_MIRROR.
688
689config FRAME_VECTOR
690 bool
691
692config ARCH_USES_HIGH_VMA_FLAGS
693 bool
694config ARCH_HAS_PKEYS
695 bool
696
697config PERCPU_STATS
698 bool "Collect percpu memory statistics"
699 help
700 This feature collects and exposes statistics via debugfs. The
701 information includes global and per chunk statistics, which can
702 be used to help understand percpu memory usage.
703
704config GUP_BENCHMARK
705 bool "Enable infrastructure for get_user_pages_fast() benchmarking"
706 help
707 Provides /sys/kernel/debug/gup_benchmark that helps with testing
708 performance of get_user_pages_fast().
709
710 See tools/testing/selftests/vm/gup_benchmark.c
711
712config GUP_GET_PTE_LOW_HIGH
713 bool
714
715config READ_ONLY_THP_FOR_FS
716 bool "Read-only THP for filesystems (EXPERIMENTAL)"
717 depends on TRANSPARENT_HUGE_PAGECACHE && SHMEM
718
719 help
720 Allow khugepaged to put read-only file-backed pages in THP.
721
722 This is marked experimental because it is a new feature. Write
723 support of file THPs will be developed in the next few release
724 cycles.
725
726config ARCH_HAS_PTE_SPECIAL
727 bool
728
729#
730# Some architectures require a special hugepage directory format that is
731# required to support multiple hugepage sizes. For example a4fe3ce76
732# "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
733# introduced it on powerpc. This allows for a more flexible hugepage
734# pagetable layouts.
735#
736config ARCH_HAS_HUGEPD
737 bool
738
739endmenu
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