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Linux/mm/Kconfig

  1 config SELECT_MEMORY_MODEL
  2         def_bool y
  3         depends on ARCH_SELECT_MEMORY_MODEL
  4 
  5 choice
  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 
 12 config 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 
 31 config 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 
 47 config 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 
 62 endchoice
 63 
 64 config DISCONTIGMEM
 65         def_bool y
 66         depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
 67 
 68 config SPARSEMEM
 69         def_bool y
 70         depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
 71 
 72 config FLATMEM
 73         def_bool y
 74         depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
 75 
 76 config 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 #
 85 config NEED_MULTIPLE_NODES
 86         def_bool y
 87         depends on DISCONTIGMEM || NUMA
 88 
 89 config 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 #
103 config 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 #
111 config SPARSEMEM_EXTREME
112         def_bool y
113         depends on SPARSEMEM && !SPARSEMEM_STATIC
114 
115 config SPARSEMEM_VMEMMAP_ENABLE
116         bool
117 
118 config SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
119         def_bool y
120         depends on SPARSEMEM && X86_64
121 
122 config 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 
131 config HAVE_MEMBLOCK
132         bool
133 
134 config HAVE_MEMBLOCK_NODE_MAP
135         bool
136 
137 config HAVE_MEMBLOCK_PHYS_MAP
138         bool
139 
140 config HAVE_GENERIC_RCU_GUP
141         bool
142 
143 config ARCH_DISCARD_MEMBLOCK
144         bool
145 
146 config NO_BOOTMEM
147         bool
148 
149 config MEMORY_ISOLATION
150         bool
151 
152 config 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 #
182 config HAVE_BOOTMEM_INFO_NODE
183         def_bool n
184 
185 # eventually, we can have this option just 'select SPARSEMEM'
186 config 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 
191 config MEMORY_HOTPLUG_SPARSE
192         def_bool y
193         depends on SPARSEMEM && MEMORY_HOTPLUG
194 
195 config MEMORY_HOTPLUG_DEFAULT_ONLINE
196         bool "Online the newly added memory blocks by default"
197         default n
198         depends on MEMORY_HOTPLUG
199         help
200           This option sets the default policy setting for memory hotplug
201           onlining policy (/sys/devices/system/memory/auto_online_blocks) which
202           determines what happens to newly added memory regions. Policy setting
203           can always be changed at runtime.
204           See Documentation/memory-hotplug.txt for more information.
205 
206           Say Y here if you want all hot-plugged memory blocks to appear in
207           'online' state by default.
208           Say N here if you want the default policy to keep all hot-plugged
209           memory blocks in 'offline' state.
210 
211 config MEMORY_HOTREMOVE
212         bool "Allow for memory hot remove"
213         select MEMORY_ISOLATION
214         select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
215         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
216         depends on MIGRATION
217 
218 # Heavily threaded applications may benefit from splitting the mm-wide
219 # page_table_lock, so that faults on different parts of the user address
220 # space can be handled with less contention: split it at this NR_CPUS.
221 # Default to 4 for wider testing, though 8 might be more appropriate.
222 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
223 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
224 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
225 #
226 config SPLIT_PTLOCK_CPUS
227         int
228         default "999999" if !MMU
229         default "999999" if ARM && !CPU_CACHE_VIPT
230         default "999999" if PARISC && !PA20
231         default "4"
232 
233 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
234         bool
235 
236 #
237 # support for memory balloon
238 config MEMORY_BALLOON
239         bool
240 
241 #
242 # support for memory balloon compaction
243 config BALLOON_COMPACTION
244         bool "Allow for balloon memory compaction/migration"
245         def_bool y
246         depends on COMPACTION && MEMORY_BALLOON
247         help
248           Memory fragmentation introduced by ballooning might reduce
249           significantly the number of 2MB contiguous memory blocks that can be
250           used within a guest, thus imposing performance penalties associated
251           with the reduced number of transparent huge pages that could be used
252           by the guest workload. Allowing the compaction & migration for memory
253           pages enlisted as being part of memory balloon devices avoids the
254           scenario aforementioned and helps improving memory defragmentation.
255 
256 #
257 # support for memory compaction
258 config COMPACTION
259         bool "Allow for memory compaction"
260         def_bool y
261         select MIGRATION
262         depends on MMU
263         help
264           Allows the compaction of memory for the allocation of huge pages.
265 
266 #
267 # support for page migration
268 #
269 config MIGRATION
270         bool "Page migration"
271         def_bool y
272         depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
273         help
274           Allows the migration of the physical location of pages of processes
275           while the virtual addresses are not changed. This is useful in
276           two situations. The first is on NUMA systems to put pages nearer
277           to the processors accessing. The second is when allocating huge
278           pages as migration can relocate pages to satisfy a huge page
279           allocation instead of reclaiming.
280 
281 config ARCH_ENABLE_HUGEPAGE_MIGRATION
282         bool
283 
284 config PHYS_ADDR_T_64BIT
285         def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
286 
287 config BOUNCE
288         bool "Enable bounce buffers"
289         default y
290         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
291         help
292           Enable bounce buffers for devices that cannot access
293           the full range of memory available to the CPU. Enabled
294           by default when ZONE_DMA or HIGHMEM is selected, but you
295           may say n to override this.
296 
297 # On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
298 # have more than 4GB of memory, but we don't currently use the IOTLB to present
299 # a 32-bit address to OHCI.  So we need to use a bounce pool instead.
300 config NEED_BOUNCE_POOL
301         bool
302         default y if TILE && USB_OHCI_HCD
303 
304 config NR_QUICK
305         int
306         depends on QUICKLIST
307         default "2" if AVR32
308         default "1"
309 
310 config VIRT_TO_BUS
311         bool
312         help
313           An architecture should select this if it implements the
314           deprecated interface virt_to_bus().  All new architectures
315           should probably not select this.
316 
317 
318 config MMU_NOTIFIER
319         bool
320         select SRCU
321 
322 config KSM
323         bool "Enable KSM for page merging"
324         depends on MMU
325         help
326           Enable Kernel Samepage Merging: KSM periodically scans those areas
327           of an application's address space that an app has advised may be
328           mergeable.  When it finds pages of identical content, it replaces
329           the many instances by a single page with that content, so
330           saving memory until one or another app needs to modify the content.
331           Recommended for use with KVM, or with other duplicative applications.
332           See Documentation/vm/ksm.txt for more information: KSM is inactive
333           until a program has madvised that an area is MADV_MERGEABLE, and
334           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
335 
336 config DEFAULT_MMAP_MIN_ADDR
337         int "Low address space to protect from user allocation"
338         depends on MMU
339         default 4096
340         help
341           This is the portion of low virtual memory which should be protected
342           from userspace allocation.  Keeping a user from writing to low pages
343           can help reduce the impact of kernel NULL pointer bugs.
344 
345           For most ia64, ppc64 and x86 users with lots of address space
346           a value of 65536 is reasonable and should cause no problems.
347           On arm and other archs it should not be higher than 32768.
348           Programs which use vm86 functionality or have some need to map
349           this low address space will need CAP_SYS_RAWIO or disable this
350           protection by setting the value to 0.
351 
352           This value can be changed after boot using the
353           /proc/sys/vm/mmap_min_addr tunable.
354 
355 config ARCH_SUPPORTS_MEMORY_FAILURE
356         bool
357 
358 config MEMORY_FAILURE
359         depends on MMU
360         depends on ARCH_SUPPORTS_MEMORY_FAILURE
361         bool "Enable recovery from hardware memory errors"
362         select MEMORY_ISOLATION
363         select RAS
364         help
365           Enables code to recover from some memory failures on systems
366           with MCA recovery. This allows a system to continue running
367           even when some of its memory has uncorrected errors. This requires
368           special hardware support and typically ECC memory.
369 
370 config HWPOISON_INJECT
371         tristate "HWPoison pages injector"
372         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
373         select PROC_PAGE_MONITOR
374 
375 config NOMMU_INITIAL_TRIM_EXCESS
376         int "Turn on mmap() excess space trimming before booting"
377         depends on !MMU
378         default 1
379         help
380           The NOMMU mmap() frequently needs to allocate large contiguous chunks
381           of memory on which to store mappings, but it can only ask the system
382           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
383           more than it requires.  To deal with this, mmap() is able to trim off
384           the excess and return it to the allocator.
385 
386           If trimming is enabled, the excess is trimmed off and returned to the
387           system allocator, which can cause extra fragmentation, particularly
388           if there are a lot of transient processes.
389 
390           If trimming is disabled, the excess is kept, but not used, which for
391           long-term mappings means that the space is wasted.
392 
393           Trimming can be dynamically controlled through a sysctl option
394           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
395           excess pages there must be before trimming should occur, or zero if
396           no trimming is to occur.
397 
398           This option specifies the initial value of this option.  The default
399           of 1 says that all excess pages should be trimmed.
400 
401           See Documentation/nommu-mmap.txt for more information.
402 
403 config TRANSPARENT_HUGEPAGE
404         bool "Transparent Hugepage Support"
405         depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
406         select COMPACTION
407         select RADIX_TREE_MULTIORDER
408         help
409           Transparent Hugepages allows the kernel to use huge pages and
410           huge tlb transparently to the applications whenever possible.
411           This feature can improve computing performance to certain
412           applications by speeding up page faults during memory
413           allocation, by reducing the number of tlb misses and by speeding
414           up the pagetable walking.
415 
416           If memory constrained on embedded, you may want to say N.
417 
418 choice
419         prompt "Transparent Hugepage Support sysfs defaults"
420         depends on TRANSPARENT_HUGEPAGE
421         default TRANSPARENT_HUGEPAGE_ALWAYS
422         help
423           Selects the sysfs defaults for Transparent Hugepage Support.
424 
425         config TRANSPARENT_HUGEPAGE_ALWAYS
426                 bool "always"
427         help
428           Enabling Transparent Hugepage always, can increase the
429           memory footprint of applications without a guaranteed
430           benefit but it will work automatically for all applications.
431 
432         config TRANSPARENT_HUGEPAGE_MADVISE
433                 bool "madvise"
434         help
435           Enabling Transparent Hugepage madvise, will only provide a
436           performance improvement benefit to the applications using
437           madvise(MADV_HUGEPAGE) but it won't risk to increase the
438           memory footprint of applications without a guaranteed
439           benefit.
440 endchoice
441 
442 #
443 # UP and nommu archs use km based percpu allocator
444 #
445 config NEED_PER_CPU_KM
446         depends on !SMP
447         bool
448         default y
449 
450 config CLEANCACHE
451         bool "Enable cleancache driver to cache clean pages if tmem is present"
452         default n
453         help
454           Cleancache can be thought of as a page-granularity victim cache
455           for clean pages that the kernel's pageframe replacement algorithm
456           (PFRA) would like to keep around, but can't since there isn't enough
457           memory.  So when the PFRA "evicts" a page, it first attempts to use
458           cleancache code to put the data contained in that page into
459           "transcendent memory", memory that is not directly accessible or
460           addressable by the kernel and is of unknown and possibly
461           time-varying size.  And when a cleancache-enabled
462           filesystem wishes to access a page in a file on disk, it first
463           checks cleancache to see if it already contains it; if it does,
464           the page is copied into the kernel and a disk access is avoided.
465           When a transcendent memory driver is available (such as zcache or
466           Xen transcendent memory), a significant I/O reduction
467           may be achieved.  When none is available, all cleancache calls
468           are reduced to a single pointer-compare-against-NULL resulting
469           in a negligible performance hit.
470 
471           If unsure, say Y to enable cleancache
472 
473 config FRONTSWAP
474         bool "Enable frontswap to cache swap pages if tmem is present"
475         depends on SWAP
476         default n
477         help
478           Frontswap is so named because it can be thought of as the opposite
479           of a "backing" store for a swap device.  The data is stored into
480           "transcendent memory", memory that is not directly accessible or
481           addressable by the kernel and is of unknown and possibly
482           time-varying size.  When space in transcendent memory is available,
483           a significant swap I/O reduction may be achieved.  When none is
484           available, all frontswap calls are reduced to a single pointer-
485           compare-against-NULL resulting in a negligible performance hit
486           and swap data is stored as normal on the matching swap device.
487 
488           If unsure, say Y to enable frontswap.
489 
490 config CMA
491         bool "Contiguous Memory Allocator"
492         depends on HAVE_MEMBLOCK && MMU
493         select MIGRATION
494         select MEMORY_ISOLATION
495         help
496           This enables the Contiguous Memory Allocator which allows other
497           subsystems to allocate big physically-contiguous blocks of memory.
498           CMA reserves a region of memory and allows only movable pages to
499           be allocated from it. This way, the kernel can use the memory for
500           pagecache and when a subsystem requests for contiguous area, the
501           allocated pages are migrated away to serve the contiguous request.
502 
503           If unsure, say "n".
504 
505 config CMA_DEBUG
506         bool "CMA debug messages (DEVELOPMENT)"
507         depends on DEBUG_KERNEL && CMA
508         help
509           Turns on debug messages in CMA.  This produces KERN_DEBUG
510           messages for every CMA call as well as various messages while
511           processing calls such as dma_alloc_from_contiguous().
512           This option does not affect warning and error messages.
513 
514 config CMA_DEBUGFS
515         bool "CMA debugfs interface"
516         depends on CMA && DEBUG_FS
517         help
518           Turns on the DebugFS interface for CMA.
519 
520 config CMA_AREAS
521         int "Maximum count of the CMA areas"
522         depends on CMA
523         default 7
524         help
525           CMA allows to create CMA areas for particular purpose, mainly,
526           used as device private area. This parameter sets the maximum
527           number of CMA area in the system.
528 
529           If unsure, leave the default value "7".
530 
531 config MEM_SOFT_DIRTY
532         bool "Track memory changes"
533         depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
534         select PROC_PAGE_MONITOR
535         help
536           This option enables memory changes tracking by introducing a
537           soft-dirty bit on pte-s. This bit it set when someone writes
538           into a page just as regular dirty bit, but unlike the latter
539           it can be cleared by hands.
540 
541           See Documentation/vm/soft-dirty.txt for more details.
542 
543 config ZSWAP
544         bool "Compressed cache for swap pages (EXPERIMENTAL)"
545         depends on FRONTSWAP && CRYPTO=y
546         select CRYPTO_LZO
547         select ZPOOL
548         default n
549         help
550           A lightweight compressed cache for swap pages.  It takes
551           pages that are in the process of being swapped out and attempts to
552           compress them into a dynamically allocated RAM-based memory pool.
553           This can result in a significant I/O reduction on swap device and,
554           in the case where decompressing from RAM is faster that swap device
555           reads, can also improve workload performance.
556 
557           This is marked experimental because it is a new feature (as of
558           v3.11) that interacts heavily with memory reclaim.  While these
559           interactions don't cause any known issues on simple memory setups,
560           they have not be fully explored on the large set of potential
561           configurations and workloads that exist.
562 
563 config ZPOOL
564         tristate "Common API for compressed memory storage"
565         default n
566         help
567           Compressed memory storage API.  This allows using either zbud or
568           zsmalloc.
569 
570 config ZBUD
571         tristate "Low (Up to 2x) density storage for compressed pages"
572         default n
573         help
574           A special purpose allocator for storing compressed pages.
575           It is designed to store up to two compressed pages per physical
576           page.  While this design limits storage density, it has simple and
577           deterministic reclaim properties that make it preferable to a higher
578           density approach when reclaim will be used.
579 
580 config Z3FOLD
581         tristate "Up to 3x density storage for compressed pages"
582         depends on ZPOOL
583         default n
584         help
585           A special purpose allocator for storing compressed pages.
586           It is designed to store up to three compressed pages per physical
587           page. It is a ZBUD derivative so the simplicity and determinism are
588           still there.
589 
590 config ZSMALLOC
591         tristate "Memory allocator for compressed pages"
592         depends on MMU
593         default n
594         help
595           zsmalloc is a slab-based memory allocator designed to store
596           compressed RAM pages.  zsmalloc uses virtual memory mapping
597           in order to reduce fragmentation.  However, this results in a
598           non-standard allocator interface where a handle, not a pointer, is
599           returned by an alloc().  This handle must be mapped in order to
600           access the allocated space.
601 
602 config PGTABLE_MAPPING
603         bool "Use page table mapping to access object in zsmalloc"
604         depends on ZSMALLOC
605         help
606           By default, zsmalloc uses a copy-based object mapping method to
607           access allocations that span two pages. However, if a particular
608           architecture (ex, ARM) performs VM mapping faster than copying,
609           then you should select this. This causes zsmalloc to use page table
610           mapping rather than copying for object mapping.
611 
612           You can check speed with zsmalloc benchmark:
613           https://github.com/spartacus06/zsmapbench
614 
615 config ZSMALLOC_STAT
616         bool "Export zsmalloc statistics"
617         depends on ZSMALLOC
618         select DEBUG_FS
619         help
620           This option enables code in the zsmalloc to collect various
621           statistics about whats happening in zsmalloc and exports that
622           information to userspace via debugfs.
623           If unsure, say N.
624 
625 config GENERIC_EARLY_IOREMAP
626         bool
627 
628 config MAX_STACK_SIZE_MB
629         int "Maximum user stack size for 32-bit processes (MB)"
630         default 80
631         range 8 256 if METAG
632         range 8 2048
633         depends on STACK_GROWSUP && (!64BIT || COMPAT)
634         help
635           This is the maximum stack size in Megabytes in the VM layout of 32-bit
636           user processes when the stack grows upwards (currently only on parisc
637           and metag arch). The stack will be located at the highest memory
638           address minus the given value, unless the RLIMIT_STACK hard limit is
639           changed to a smaller value in which case that is used.
640 
641           A sane initial value is 80 MB.
642 
643 # For architectures that support deferred memory initialisation
644 config ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
645         bool
646 
647 config DEFERRED_STRUCT_PAGE_INIT
648         bool "Defer initialisation of struct pages to kthreads"
649         default n
650         depends on ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
651         depends on NO_BOOTMEM && MEMORY_HOTPLUG
652         depends on !FLATMEM
653         help
654           Ordinarily all struct pages are initialised during early boot in a
655           single thread. On very large machines this can take a considerable
656           amount of time. If this option is set, large machines will bring up
657           a subset of memmap at boot and then initialise the rest in parallel
658           by starting one-off "pgdatinitX" kernel thread for each node X. This
659           has a potential performance impact on processes running early in the
660           lifetime of the system until these kthreads finish the
661           initialisation.
662 
663 config IDLE_PAGE_TRACKING
664         bool "Enable idle page tracking"
665         depends on SYSFS && MMU
666         select PAGE_EXTENSION if !64BIT
667         help
668           This feature allows to estimate the amount of user pages that have
669           not been touched during a given period of time. This information can
670           be useful to tune memory cgroup limits and/or for job placement
671           within a compute cluster.
672 
673           See Documentation/vm/idle_page_tracking.txt for more details.
674 
675 config ZONE_DEVICE
676         bool "Device memory (pmem, etc...) hotplug support" if EXPERT
677         depends on MEMORY_HOTPLUG
678         depends on MEMORY_HOTREMOVE
679         depends on SPARSEMEM_VMEMMAP
680         depends on X86_64 #arch_add_memory() comprehends device memory
681 
682         help
683           Device memory hotplug support allows for establishing pmem,
684           or other device driver discovered memory regions, in the
685           memmap. This allows pfn_to_page() lookups of otherwise
686           "device-physical" addresses which is needed for using a DAX
687           mapping in an O_DIRECT operation, among other things.
688 
689           If FS_DAX is enabled, then say Y.
690 
691 config FRAME_VECTOR
692         bool
693 
694 config ARCH_USES_HIGH_VMA_FLAGS
695         bool
696 config ARCH_HAS_PKEYS
697         bool

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