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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_GUP
141 bool
142
143config ARCH_DISCARD_MEMBLOCK
144 bool
145
146config NO_BOOTMEM
147 bool
148
149config MEMORY_ISOLATION
150 bool
151
152#
153# Only be set on architectures that have completely implemented memory hotplug
154# feature. If you are not sure, don't touch it.
155#
156config HAVE_BOOTMEM_INFO_NODE
157 def_bool n
158
159# eventually, we can have this option just 'select SPARSEMEM'
160config MEMORY_HOTPLUG
161 bool "Allow for memory hot-add"
162 depends on SPARSEMEM || X86_64_ACPI_NUMA
163 depends on ARCH_ENABLE_MEMORY_HOTPLUG
164
165config MEMORY_HOTPLUG_SPARSE
166 def_bool y
167 depends on SPARSEMEM && MEMORY_HOTPLUG
168
169config MEMORY_HOTPLUG_DEFAULT_ONLINE
170 bool "Online the newly added memory blocks by default"
171 default n
172 depends on MEMORY_HOTPLUG
173 help
174 This option sets the default policy setting for memory hotplug
175 onlining policy (/sys/devices/system/memory/auto_online_blocks) which
176 determines what happens to newly added memory regions. Policy setting
177 can always be changed at runtime.
178 See Documentation/memory-hotplug.txt for more information.
179
180 Say Y here if you want all hot-plugged memory blocks to appear in
181 'online' state by default.
182 Say N here if you want the default policy to keep all hot-plugged
183 memory blocks in 'offline' state.
184
185config MEMORY_HOTREMOVE
186 bool "Allow for memory hot remove"
187 select MEMORY_ISOLATION
188 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
189 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
190 depends on MIGRATION
191
192# Heavily threaded applications may benefit from splitting the mm-wide
193# page_table_lock, so that faults on different parts of the user address
194# space can be handled with less contention: split it at this NR_CPUS.
195# Default to 4 for wider testing, though 8 might be more appropriate.
196# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
197# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
198# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
199#
200config SPLIT_PTLOCK_CPUS
201 int
202 default "999999" if !MMU
203 default "999999" if ARM && !CPU_CACHE_VIPT
204 default "999999" if PARISC && !PA20
205 default "4"
206
207config ARCH_ENABLE_SPLIT_PMD_PTLOCK
208 bool
209
210#
211# support for memory balloon
212config MEMORY_BALLOON
213 bool
214
215#
216# support for memory balloon compaction
217config BALLOON_COMPACTION
218 bool "Allow for balloon memory compaction/migration"
219 def_bool y
220 depends on COMPACTION && MEMORY_BALLOON
221 help
222 Memory fragmentation introduced by ballooning might reduce
223 significantly the number of 2MB contiguous memory blocks that can be
224 used within a guest, thus imposing performance penalties associated
225 with the reduced number of transparent huge pages that could be used
226 by the guest workload. Allowing the compaction & migration for memory
227 pages enlisted as being part of memory balloon devices avoids the
228 scenario aforementioned and helps improving memory defragmentation.
229
230#
231# support for memory compaction
232config COMPACTION
233 bool "Allow for memory compaction"
234 def_bool y
235 select MIGRATION
236 depends on MMU
237 help
238 Compaction is the only memory management component to form
239 high order (larger physically contiguous) memory blocks
240 reliably. The page allocator relies on compaction heavily and
241 the lack of the feature can lead to unexpected OOM killer
242 invocations for high order memory requests. You shouldn't
243 disable this option unless there really is a strong reason for
244 it and then we would be really interested to hear about that at
245 linux-mm@kvack.org.
246
247#
248# support for page migration
249#
250config MIGRATION
251 bool "Page migration"
252 def_bool y
253 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
254 help
255 Allows the migration of the physical location of pages of processes
256 while the virtual addresses are not changed. This is useful in
257 two situations. The first is on NUMA systems to put pages nearer
258 to the processors accessing. The second is when allocating huge
259 pages as migration can relocate pages to satisfy a huge page
260 allocation instead of reclaiming.
261
262config ARCH_ENABLE_HUGEPAGE_MIGRATION
263 bool
264
265config ARCH_ENABLE_THP_MIGRATION
266 bool
267
268config PHYS_ADDR_T_64BIT
269 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
270
271config BOUNCE
272 bool "Enable bounce buffers"
273 default y
274 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
275 help
276 Enable bounce buffers for devices that cannot access
277 the full range of memory available to the CPU. Enabled
278 by default when ZONE_DMA or HIGHMEM is selected, but you
279 may say n to override this.
280
281config NR_QUICK
282 int
283 depends on QUICKLIST
284 default "1"
285
286config VIRT_TO_BUS
287 bool
288 help
289 An architecture should select this if it implements the
290 deprecated interface virt_to_bus(). All new architectures
291 should probably not select this.
292
293
294config MMU_NOTIFIER
295 bool
296 select SRCU
297
298config KSM
299 bool "Enable KSM for page merging"
300 depends on MMU
301 help
302 Enable Kernel Samepage Merging: KSM periodically scans those areas
303 of an application's address space that an app has advised may be
304 mergeable. When it finds pages of identical content, it replaces
305 the many instances by a single page with that content, so
306 saving memory until one or another app needs to modify the content.
307 Recommended for use with KVM, or with other duplicative applications.
308 See Documentation/vm/ksm.txt for more information: KSM is inactive
309 until a program has madvised that an area is MADV_MERGEABLE, and
310 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
311
312config DEFAULT_MMAP_MIN_ADDR
313 int "Low address space to protect from user allocation"
314 depends on MMU
315 default 4096
316 help
317 This is the portion of low virtual memory which should be protected
318 from userspace allocation. Keeping a user from writing to low pages
319 can help reduce the impact of kernel NULL pointer bugs.
320
321 For most ia64, ppc64 and x86 users with lots of address space
322 a value of 65536 is reasonable and should cause no problems.
323 On arm and other archs it should not be higher than 32768.
324 Programs which use vm86 functionality or have some need to map
325 this low address space will need CAP_SYS_RAWIO or disable this
326 protection by setting the value to 0.
327
328 This value can be changed after boot using the
329 /proc/sys/vm/mmap_min_addr tunable.
330
331config ARCH_SUPPORTS_MEMORY_FAILURE
332 bool
333
334config MEMORY_FAILURE
335 depends on MMU
336 depends on ARCH_SUPPORTS_MEMORY_FAILURE
337 bool "Enable recovery from hardware memory errors"
338 select MEMORY_ISOLATION
339 select RAS
340 help
341 Enables code to recover from some memory failures on systems
342 with MCA recovery. This allows a system to continue running
343 even when some of its memory has uncorrected errors. This requires
344 special hardware support and typically ECC memory.
345
346config HWPOISON_INJECT
347 tristate "HWPoison pages injector"
348 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
349 select PROC_PAGE_MONITOR
350
351config NOMMU_INITIAL_TRIM_EXCESS
352 int "Turn on mmap() excess space trimming before booting"
353 depends on !MMU
354 default 1
355 help
356 The NOMMU mmap() frequently needs to allocate large contiguous chunks
357 of memory on which to store mappings, but it can only ask the system
358 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
359 more than it requires. To deal with this, mmap() is able to trim off
360 the excess and return it to the allocator.
361
362 If trimming is enabled, the excess is trimmed off and returned to the
363 system allocator, which can cause extra fragmentation, particularly
364 if there are a lot of transient processes.
365
366 If trimming is disabled, the excess is kept, but not used, which for
367 long-term mappings means that the space is wasted.
368
369 Trimming can be dynamically controlled through a sysctl option
370 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
371 excess pages there must be before trimming should occur, or zero if
372 no trimming is to occur.
373
374 This option specifies the initial value of this option. The default
375 of 1 says that all excess pages should be trimmed.
376
377 See Documentation/nommu-mmap.txt for more information.
378
379config TRANSPARENT_HUGEPAGE
380 bool "Transparent Hugepage Support"
381 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
382 select COMPACTION
383 select RADIX_TREE_MULTIORDER
384 help
385 Transparent Hugepages allows the kernel to use huge pages and
386 huge tlb transparently to the applications whenever possible.
387 This feature can improve computing performance to certain
388 applications by speeding up page faults during memory
389 allocation, by reducing the number of tlb misses and by speeding
390 up the pagetable walking.
391
392 If memory constrained on embedded, you may want to say N.
393
394choice
395 prompt "Transparent Hugepage Support sysfs defaults"
396 depends on TRANSPARENT_HUGEPAGE
397 default TRANSPARENT_HUGEPAGE_ALWAYS
398 help
399 Selects the sysfs defaults for Transparent Hugepage Support.
400
401 config TRANSPARENT_HUGEPAGE_ALWAYS
402 bool "always"
403 help
404 Enabling Transparent Hugepage always, can increase the
405 memory footprint of applications without a guaranteed
406 benefit but it will work automatically for all applications.
407
408 config TRANSPARENT_HUGEPAGE_MADVISE
409 bool "madvise"
410 help
411 Enabling Transparent Hugepage madvise, will only provide a
412 performance improvement benefit to the applications using
413 madvise(MADV_HUGEPAGE) but it won't risk to increase the
414 memory footprint of applications without a guaranteed
415 benefit.
416endchoice
417
418config ARCH_WANTS_THP_SWAP
419 def_bool n
420
421config THP_SWAP
422 def_bool y
423 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP
424 help
425 Swap transparent huge pages in one piece, without splitting.
426 XXX: For now this only does clustered swap space allocation.
427
428 For selection by architectures with reasonable THP sizes.
429
430config TRANSPARENT_HUGE_PAGECACHE
431 def_bool y
432 depends on TRANSPARENT_HUGEPAGE
433
434#
435# UP and nommu archs use km based percpu allocator
436#
437config NEED_PER_CPU_KM
438 depends on !SMP
439 bool
440 default y
441
442config CLEANCACHE
443 bool "Enable cleancache driver to cache clean pages if tmem is present"
444 default n
445 help
446 Cleancache can be thought of as a page-granularity victim cache
447 for clean pages that the kernel's pageframe replacement algorithm
448 (PFRA) would like to keep around, but can't since there isn't enough
449 memory. So when the PFRA "evicts" a page, it first attempts to use
450 cleancache code to put the data contained in that page into
451 "transcendent memory", memory that is not directly accessible or
452 addressable by the kernel and is of unknown and possibly
453 time-varying size. And when a cleancache-enabled
454 filesystem wishes to access a page in a file on disk, it first
455 checks cleancache to see if it already contains it; if it does,
456 the page is copied into the kernel and a disk access is avoided.
457 When a transcendent memory driver is available (such as zcache or
458 Xen transcendent memory), a significant I/O reduction
459 may be achieved. When none is available, all cleancache calls
460 are reduced to a single pointer-compare-against-NULL resulting
461 in a negligible performance hit.
462
463 If unsure, say Y to enable cleancache
464
465config FRONTSWAP
466 bool "Enable frontswap to cache swap pages if tmem is present"
467 depends on SWAP
468 default n
469 help
470 Frontswap is so named because it can be thought of as the opposite
471 of a "backing" store for a swap device. The data is stored into
472 "transcendent memory", memory that is not directly accessible or
473 addressable by the kernel and is of unknown and possibly
474 time-varying size. When space in transcendent memory is available,
475 a significant swap I/O reduction may be achieved. When none is
476 available, all frontswap calls are reduced to a single pointer-
477 compare-against-NULL resulting in a negligible performance hit
478 and swap data is stored as normal on the matching swap device.
479
480 If unsure, say Y to enable frontswap.
481
482config CMA
483 bool "Contiguous Memory Allocator"
484 depends on HAVE_MEMBLOCK && MMU
485 select MIGRATION
486 select MEMORY_ISOLATION
487 help
488 This enables the Contiguous Memory Allocator which allows other
489 subsystems to allocate big physically-contiguous blocks of memory.
490 CMA reserves a region of memory and allows only movable pages to
491 be allocated from it. This way, the kernel can use the memory for
492 pagecache and when a subsystem requests for contiguous area, the
493 allocated pages are migrated away to serve the contiguous request.
494
495 If unsure, say "n".
496
497config CMA_DEBUG
498 bool "CMA debug messages (DEVELOPMENT)"
499 depends on DEBUG_KERNEL && CMA
500 help
501 Turns on debug messages in CMA. This produces KERN_DEBUG
502 messages for every CMA call as well as various messages while
503 processing calls such as dma_alloc_from_contiguous().
504 This option does not affect warning and error messages.
505
506config CMA_DEBUGFS
507 bool "CMA debugfs interface"
508 depends on CMA && DEBUG_FS
509 help
510 Turns on the DebugFS interface for CMA.
511
512config CMA_AREAS
513 int "Maximum count of the CMA areas"
514 depends on CMA
515 default 7
516 help
517 CMA allows to create CMA areas for particular purpose, mainly,
518 used as device private area. This parameter sets the maximum
519 number of CMA area in the system.
520
521 If unsure, leave the default value "7".
522
523config MEM_SOFT_DIRTY
524 bool "Track memory changes"
525 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
526 select PROC_PAGE_MONITOR
527 help
528 This option enables memory changes tracking by introducing a
529 soft-dirty bit on pte-s. This bit it set when someone writes
530 into a page just as regular dirty bit, but unlike the latter
531 it can be cleared by hands.
532
533 See Documentation/vm/soft-dirty.txt for more details.
534
535config ZSWAP
536 bool "Compressed cache for swap pages (EXPERIMENTAL)"
537 depends on FRONTSWAP && CRYPTO=y
538 select CRYPTO_LZO
539 select ZPOOL
540 default n
541 help
542 A lightweight compressed cache for swap pages. It takes
543 pages that are in the process of being swapped out and attempts to
544 compress them into a dynamically allocated RAM-based memory pool.
545 This can result in a significant I/O reduction on swap device and,
546 in the case where decompressing from RAM is faster that swap device
547 reads, can also improve workload performance.
548
549 This is marked experimental because it is a new feature (as of
550 v3.11) that interacts heavily with memory reclaim. While these
551 interactions don't cause any known issues on simple memory setups,
552 they have not be fully explored on the large set of potential
553 configurations and workloads that exist.
554
555config ZPOOL
556 tristate "Common API for compressed memory storage"
557 default n
558 help
559 Compressed memory storage API. This allows using either zbud or
560 zsmalloc.
561
562config ZBUD
563 tristate "Low (Up to 2x) density storage for compressed pages"
564 default n
565 help
566 A special purpose allocator for storing compressed pages.
567 It is designed to store up to two compressed pages per physical
568 page. While this design limits storage density, it has simple and
569 deterministic reclaim properties that make it preferable to a higher
570 density approach when reclaim will be used.
571
572config Z3FOLD
573 tristate "Up to 3x density storage for compressed pages"
574 depends on ZPOOL
575 default n
576 help
577 A special purpose allocator for storing compressed pages.
578 It is designed to store up to three compressed pages per physical
579 page. It is a ZBUD derivative so the simplicity and determinism are
580 still there.
581
582config ZSMALLOC
583 tristate "Memory allocator for compressed pages"
584 depends on MMU
585 default n
586 help
587 zsmalloc is a slab-based memory allocator designed to store
588 compressed RAM pages. zsmalloc uses virtual memory mapping
589 in order to reduce fragmentation. However, this results in a
590 non-standard allocator interface where a handle, not a pointer, is
591 returned by an alloc(). This handle must be mapped in order to
592 access the allocated space.
593
594config PGTABLE_MAPPING
595 bool "Use page table mapping to access object in zsmalloc"
596 depends on ZSMALLOC
597 help
598 By default, zsmalloc uses a copy-based object mapping method to
599 access allocations that span two pages. However, if a particular
600 architecture (ex, ARM) performs VM mapping faster than copying,
601 then you should select this. This causes zsmalloc to use page table
602 mapping rather than copying for object mapping.
603
604 You can check speed with zsmalloc benchmark:
605 https://github.com/spartacus06/zsmapbench
606
607config ZSMALLOC_STAT
608 bool "Export zsmalloc statistics"
609 depends on ZSMALLOC
610 select DEBUG_FS
611 help
612 This option enables code in the zsmalloc to collect various
613 statistics about whats happening in zsmalloc and exports that
614 information to userspace via debugfs.
615 If unsure, say N.
616
617config GENERIC_EARLY_IOREMAP
618 bool
619
620config MAX_STACK_SIZE_MB
621 int "Maximum user stack size for 32-bit processes (MB)"
622 default 80
623 range 8 2048
624 depends on STACK_GROWSUP && (!64BIT || COMPAT)
625 help
626 This is the maximum stack size in Megabytes in the VM layout of 32-bit
627 user processes when the stack grows upwards (currently only on parisc
628 arch). The stack will be located at the highest memory address minus
629 the given value, unless the RLIMIT_STACK hard limit is changed to a
630 smaller value in which case that is used.
631
632 A sane initial value is 80 MB.
633
634config DEFERRED_STRUCT_PAGE_INIT
635 bool "Defer initialisation of struct pages to kthreads"
636 default n
637 depends on NO_BOOTMEM
638 depends on !FLATMEM
639 depends on !NEED_PER_CPU_KM
640 help
641 Ordinarily all struct pages are initialised during early boot in a
642 single thread. On very large machines this can take a considerable
643 amount of time. If this option is set, large machines will bring up
644 a subset of memmap at boot and then initialise the rest in parallel
645 by starting one-off "pgdatinitX" kernel thread for each node X. This
646 has a potential performance impact on processes running early in the
647 lifetime of the system until these kthreads finish the
648 initialisation.
649
650config IDLE_PAGE_TRACKING
651 bool "Enable idle page tracking"
652 depends on SYSFS && MMU
653 select PAGE_EXTENSION if !64BIT
654 help
655 This feature allows to estimate the amount of user pages that have
656 not been touched during a given period of time. This information can
657 be useful to tune memory cgroup limits and/or for job placement
658 within a compute cluster.
659
660 See Documentation/vm/idle_page_tracking.txt for more details.
661
662# arch_add_memory() comprehends device memory
663config ARCH_HAS_ZONE_DEVICE
664 bool
665
666config ZONE_DEVICE
667 bool "Device memory (pmem, HMM, etc...) hotplug support"
668 depends on MEMORY_HOTPLUG
669 depends on MEMORY_HOTREMOVE
670 depends on SPARSEMEM_VMEMMAP
671 depends on ARCH_HAS_ZONE_DEVICE
672 select RADIX_TREE_MULTIORDER
673
674 help
675 Device memory hotplug support allows for establishing pmem,
676 or other device driver discovered memory regions, in the
677 memmap. This allows pfn_to_page() lookups of otherwise
678 "device-physical" addresses which is needed for using a DAX
679 mapping in an O_DIRECT operation, among other things.
680
681 If FS_DAX is enabled, then say Y.
682
683config ARCH_HAS_HMM
684 bool
685 default y
686 depends on (X86_64 || PPC64)
687 depends on ZONE_DEVICE
688 depends on MMU && 64BIT
689 depends on MEMORY_HOTPLUG
690 depends on MEMORY_HOTREMOVE
691 depends on SPARSEMEM_VMEMMAP
692
693config MIGRATE_VMA_HELPER
694 bool
695
696config HMM
697 bool
698 select MIGRATE_VMA_HELPER
699
700config HMM_MIRROR
701 bool "HMM mirror CPU page table into a device page table"
702 depends on ARCH_HAS_HMM
703 select MMU_NOTIFIER
704 select HMM
705 help
706 Select HMM_MIRROR if you want to mirror range of the CPU page table of a
707 process into a device page table. Here, mirror means "keep synchronized".
708 Prerequisites: the device must provide the ability to write-protect its
709 page tables (at PAGE_SIZE granularity), and must be able to recover from
710 the resulting potential page faults.
711
712config DEVICE_PRIVATE
713 bool "Unaddressable device memory (GPU memory, ...)"
714 depends on ARCH_HAS_HMM
715 select HMM
716
717 help
718 Allows creation of struct pages to represent unaddressable device
719 memory; i.e., memory that is only accessible from the device (or
720 group of devices). You likely also want to select HMM_MIRROR.
721
722config DEVICE_PUBLIC
723 bool "Addressable device memory (like GPU memory)"
724 depends on ARCH_HAS_HMM
725 select HMM
726
727 help
728 Allows creation of struct pages to represent addressable device
729 memory; i.e., memory that is accessible from both the device and
730 the CPU
731
732config FRAME_VECTOR
733 bool
734
735config ARCH_USES_HIGH_VMA_FLAGS
736 bool
737config ARCH_HAS_PKEYS
738 bool
739
740config PERCPU_STATS
741 bool "Collect percpu memory statistics"
742 default n
743 help
744 This feature collects and exposes statistics via debugfs. The
745 information includes global and per chunk statistics, which can
746 be used to help understand percpu memory usage.
747
748config GUP_BENCHMARK
749 bool "Enable infrastructure for get_user_pages_fast() benchmarking"
750 default n
751 help
752 Provides /sys/kernel/debug/gup_benchmark that helps with testing
753 performance of get_user_pages_fast().
754
755 See tools/testing/selftests/vm/gup_benchmark.c