xref: /openbmc/linux/mm/Kconfig (revision 56bbd862)
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 || OF_EARLY_FLATTREE || MEMORY_HOTPLUG
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	depends on COMPILE_TEST || !KASAN
191
192config MEMORY_HOTPLUG_SPARSE
193	def_bool y
194	depends on SPARSEMEM && MEMORY_HOTPLUG
195
196config MEMORY_HOTPLUG_DEFAULT_ONLINE
197        bool "Online the newly added memory blocks by default"
198        default n
199        depends on MEMORY_HOTPLUG
200        help
201	  This option sets the default policy setting for memory hotplug
202	  onlining policy (/sys/devices/system/memory/auto_online_blocks) which
203	  determines what happens to newly added memory regions. Policy setting
204	  can always be changed at runtime.
205	  See Documentation/memory-hotplug.txt for more information.
206
207	  Say Y here if you want all hot-plugged memory blocks to appear in
208	  'online' state by default.
209	  Say N here if you want the default policy to keep all hot-plugged
210	  memory blocks in 'offline' state.
211
212config MEMORY_HOTREMOVE
213	bool "Allow for memory hot remove"
214	select MEMORY_ISOLATION
215	select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
216	depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
217	depends on MIGRATION
218
219# Heavily threaded applications may benefit from splitting the mm-wide
220# page_table_lock, so that faults on different parts of the user address
221# space can be handled with less contention: split it at this NR_CPUS.
222# Default to 4 for wider testing, though 8 might be more appropriate.
223# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
224# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
225# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
226#
227config SPLIT_PTLOCK_CPUS
228	int
229	default "999999" if !MMU
230	default "999999" if ARM && !CPU_CACHE_VIPT
231	default "999999" if PARISC && !PA20
232	default "4"
233
234config ARCH_ENABLE_SPLIT_PMD_PTLOCK
235	bool
236
237#
238# support for memory balloon
239config MEMORY_BALLOON
240	bool
241
242#
243# support for memory balloon compaction
244config BALLOON_COMPACTION
245	bool "Allow for balloon memory compaction/migration"
246	def_bool y
247	depends on COMPACTION && MEMORY_BALLOON
248	help
249	  Memory fragmentation introduced by ballooning might reduce
250	  significantly the number of 2MB contiguous memory blocks that can be
251	  used within a guest, thus imposing performance penalties associated
252	  with the reduced number of transparent huge pages that could be used
253	  by the guest workload. Allowing the compaction & migration for memory
254	  pages enlisted as being part of memory balloon devices avoids the
255	  scenario aforementioned and helps improving memory defragmentation.
256
257#
258# support for memory compaction
259config COMPACTION
260	bool "Allow for memory compaction"
261	def_bool y
262	select MIGRATION
263	depends on MMU
264	help
265          Compaction is the only memory management component to form
266          high order (larger physically contiguous) memory blocks
267          reliably. The page allocator relies on compaction heavily and
268          the lack of the feature can lead to unexpected OOM killer
269          invocations for high order memory requests. You shouldn't
270          disable this option unless there really is a strong reason for
271          it and then we would be really interested to hear about that at
272          linux-mm@kvack.org.
273
274#
275# support for page migration
276#
277config MIGRATION
278	bool "Page migration"
279	def_bool y
280	depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
281	help
282	  Allows the migration of the physical location of pages of processes
283	  while the virtual addresses are not changed. This is useful in
284	  two situations. The first is on NUMA systems to put pages nearer
285	  to the processors accessing. The second is when allocating huge
286	  pages as migration can relocate pages to satisfy a huge page
287	  allocation instead of reclaiming.
288
289config ARCH_ENABLE_HUGEPAGE_MIGRATION
290	bool
291
292config PHYS_ADDR_T_64BIT
293	def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
294
295config BOUNCE
296	bool "Enable bounce buffers"
297	default y
298	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
299	help
300	  Enable bounce buffers for devices that cannot access
301	  the full range of memory available to the CPU. Enabled
302	  by default when ZONE_DMA or HIGHMEM is selected, but you
303	  may say n to override this.
304
305# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
306# have more than 4GB of memory, but we don't currently use the IOTLB to present
307# a 32-bit address to OHCI.  So we need to use a bounce pool instead.
308config NEED_BOUNCE_POOL
309	bool
310	default y if TILE && USB_OHCI_HCD
311
312config NR_QUICK
313	int
314	depends on QUICKLIST
315	default "2" if AVR32
316	default "1"
317
318config VIRT_TO_BUS
319	bool
320	help
321	  An architecture should select this if it implements the
322	  deprecated interface virt_to_bus().  All new architectures
323	  should probably not select this.
324
325
326config MMU_NOTIFIER
327	bool
328	select SRCU
329
330config KSM
331	bool "Enable KSM for page merging"
332	depends on MMU
333	help
334	  Enable Kernel Samepage Merging: KSM periodically scans those areas
335	  of an application's address space that an app has advised may be
336	  mergeable.  When it finds pages of identical content, it replaces
337	  the many instances by a single page with that content, so
338	  saving memory until one or another app needs to modify the content.
339	  Recommended for use with KVM, or with other duplicative applications.
340	  See Documentation/vm/ksm.txt for more information: KSM is inactive
341	  until a program has madvised that an area is MADV_MERGEABLE, and
342	  root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
343
344config DEFAULT_MMAP_MIN_ADDR
345        int "Low address space to protect from user allocation"
346	depends on MMU
347        default 4096
348        help
349	  This is the portion of low virtual memory which should be protected
350	  from userspace allocation.  Keeping a user from writing to low pages
351	  can help reduce the impact of kernel NULL pointer bugs.
352
353	  For most ia64, ppc64 and x86 users with lots of address space
354	  a value of 65536 is reasonable and should cause no problems.
355	  On arm and other archs it should not be higher than 32768.
356	  Programs which use vm86 functionality or have some need to map
357	  this low address space will need CAP_SYS_RAWIO or disable this
358	  protection by setting the value to 0.
359
360	  This value can be changed after boot using the
361	  /proc/sys/vm/mmap_min_addr tunable.
362
363config ARCH_SUPPORTS_MEMORY_FAILURE
364	bool
365
366config MEMORY_FAILURE
367	depends on MMU
368	depends on ARCH_SUPPORTS_MEMORY_FAILURE
369	bool "Enable recovery from hardware memory errors"
370	select MEMORY_ISOLATION
371	select RAS
372	help
373	  Enables code to recover from some memory failures on systems
374	  with MCA recovery. This allows a system to continue running
375	  even when some of its memory has uncorrected errors. This requires
376	  special hardware support and typically ECC memory.
377
378config HWPOISON_INJECT
379	tristate "HWPoison pages injector"
380	depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
381	select PROC_PAGE_MONITOR
382
383config NOMMU_INITIAL_TRIM_EXCESS
384	int "Turn on mmap() excess space trimming before booting"
385	depends on !MMU
386	default 1
387	help
388	  The NOMMU mmap() frequently needs to allocate large contiguous chunks
389	  of memory on which to store mappings, but it can only ask the system
390	  allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
391	  more than it requires.  To deal with this, mmap() is able to trim off
392	  the excess and return it to the allocator.
393
394	  If trimming is enabled, the excess is trimmed off and returned to the
395	  system allocator, which can cause extra fragmentation, particularly
396	  if there are a lot of transient processes.
397
398	  If trimming is disabled, the excess is kept, but not used, which for
399	  long-term mappings means that the space is wasted.
400
401	  Trimming can be dynamically controlled through a sysctl option
402	  (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
403	  excess pages there must be before trimming should occur, or zero if
404	  no trimming is to occur.
405
406	  This option specifies the initial value of this option.  The default
407	  of 1 says that all excess pages should be trimmed.
408
409	  See Documentation/nommu-mmap.txt for more information.
410
411config TRANSPARENT_HUGEPAGE
412	bool "Transparent Hugepage Support"
413	depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
414	select COMPACTION
415	select RADIX_TREE_MULTIORDER
416	help
417	  Transparent Hugepages allows the kernel to use huge pages and
418	  huge tlb transparently to the applications whenever possible.
419	  This feature can improve computing performance to certain
420	  applications by speeding up page faults during memory
421	  allocation, by reducing the number of tlb misses and by speeding
422	  up the pagetable walking.
423
424	  If memory constrained on embedded, you may want to say N.
425
426choice
427	prompt "Transparent Hugepage Support sysfs defaults"
428	depends on TRANSPARENT_HUGEPAGE
429	default TRANSPARENT_HUGEPAGE_ALWAYS
430	help
431	  Selects the sysfs defaults for Transparent Hugepage Support.
432
433	config TRANSPARENT_HUGEPAGE_ALWAYS
434		bool "always"
435	help
436	  Enabling Transparent Hugepage always, can increase the
437	  memory footprint of applications without a guaranteed
438	  benefit but it will work automatically for all applications.
439
440	config TRANSPARENT_HUGEPAGE_MADVISE
441		bool "madvise"
442	help
443	  Enabling Transparent Hugepage madvise, will only provide a
444	  performance improvement benefit to the applications using
445	  madvise(MADV_HUGEPAGE) but it won't risk to increase the
446	  memory footprint of applications without a guaranteed
447	  benefit.
448endchoice
449
450config	TRANSPARENT_HUGE_PAGECACHE
451	def_bool y
452	depends on TRANSPARENT_HUGEPAGE
453
454#
455# UP and nommu archs use km based percpu allocator
456#
457config NEED_PER_CPU_KM
458	depends on !SMP
459	bool
460	default y
461
462config CLEANCACHE
463	bool "Enable cleancache driver to cache clean pages if tmem is present"
464	default n
465	help
466	  Cleancache can be thought of as a page-granularity victim cache
467	  for clean pages that the kernel's pageframe replacement algorithm
468	  (PFRA) would like to keep around, but can't since there isn't enough
469	  memory.  So when the PFRA "evicts" a page, it first attempts to use
470	  cleancache code to put the data contained in that page into
471	  "transcendent memory", memory that is not directly accessible or
472	  addressable by the kernel and is of unknown and possibly
473	  time-varying size.  And when a cleancache-enabled
474	  filesystem wishes to access a page in a file on disk, it first
475	  checks cleancache to see if it already contains it; if it does,
476	  the page is copied into the kernel and a disk access is avoided.
477	  When a transcendent memory driver is available (such as zcache or
478	  Xen transcendent memory), a significant I/O reduction
479	  may be achieved.  When none is available, all cleancache calls
480	  are reduced to a single pointer-compare-against-NULL resulting
481	  in a negligible performance hit.
482
483	  If unsure, say Y to enable cleancache
484
485config FRONTSWAP
486	bool "Enable frontswap to cache swap pages if tmem is present"
487	depends on SWAP
488	default n
489	help
490	  Frontswap is so named because it can be thought of as the opposite
491	  of a "backing" store for a swap device.  The data is stored into
492	  "transcendent memory", memory that is not directly accessible or
493	  addressable by the kernel and is of unknown and possibly
494	  time-varying size.  When space in transcendent memory is available,
495	  a significant swap I/O reduction may be achieved.  When none is
496	  available, all frontswap calls are reduced to a single pointer-
497	  compare-against-NULL resulting in a negligible performance hit
498	  and swap data is stored as normal on the matching swap device.
499
500	  If unsure, say Y to enable frontswap.
501
502config CMA
503	bool "Contiguous Memory Allocator"
504	depends on HAVE_MEMBLOCK && MMU
505	select MIGRATION
506	select MEMORY_ISOLATION
507	help
508	  This enables the Contiguous Memory Allocator which allows other
509	  subsystems to allocate big physically-contiguous blocks of memory.
510	  CMA reserves a region of memory and allows only movable pages to
511	  be allocated from it. This way, the kernel can use the memory for
512	  pagecache and when a subsystem requests for contiguous area, the
513	  allocated pages are migrated away to serve the contiguous request.
514
515	  If unsure, say "n".
516
517config CMA_DEBUG
518	bool "CMA debug messages (DEVELOPMENT)"
519	depends on DEBUG_KERNEL && CMA
520	help
521	  Turns on debug messages in CMA.  This produces KERN_DEBUG
522	  messages for every CMA call as well as various messages while
523	  processing calls such as dma_alloc_from_contiguous().
524	  This option does not affect warning and error messages.
525
526config CMA_DEBUGFS
527	bool "CMA debugfs interface"
528	depends on CMA && DEBUG_FS
529	help
530	  Turns on the DebugFS interface for CMA.
531
532config CMA_AREAS
533	int "Maximum count of the CMA areas"
534	depends on CMA
535	default 7
536	help
537	  CMA allows to create CMA areas for particular purpose, mainly,
538	  used as device private area. This parameter sets the maximum
539	  number of CMA area in the system.
540
541	  If unsure, leave the default value "7".
542
543config MEM_SOFT_DIRTY
544	bool "Track memory changes"
545	depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
546	select PROC_PAGE_MONITOR
547	help
548	  This option enables memory changes tracking by introducing a
549	  soft-dirty bit on pte-s. This bit it set when someone writes
550	  into a page just as regular dirty bit, but unlike the latter
551	  it can be cleared by hands.
552
553	  See Documentation/vm/soft-dirty.txt for more details.
554
555config ZSWAP
556	bool "Compressed cache for swap pages (EXPERIMENTAL)"
557	depends on FRONTSWAP && CRYPTO=y
558	select CRYPTO_LZO
559	select ZPOOL
560	default n
561	help
562	  A lightweight compressed cache for swap pages.  It takes
563	  pages that are in the process of being swapped out and attempts to
564	  compress them into a dynamically allocated RAM-based memory pool.
565	  This can result in a significant I/O reduction on swap device and,
566	  in the case where decompressing from RAM is faster that swap device
567	  reads, can also improve workload performance.
568
569	  This is marked experimental because it is a new feature (as of
570	  v3.11) that interacts heavily with memory reclaim.  While these
571	  interactions don't cause any known issues on simple memory setups,
572	  they have not be fully explored on the large set of potential
573	  configurations and workloads that exist.
574
575config ZPOOL
576	tristate "Common API for compressed memory storage"
577	default n
578	help
579	  Compressed memory storage API.  This allows using either zbud or
580	  zsmalloc.
581
582config ZBUD
583	tristate "Low (Up to 2x) density storage for compressed pages"
584	default n
585	help
586	  A special purpose allocator for storing compressed pages.
587	  It is designed to store up to two compressed pages per physical
588	  page.  While this design limits storage density, it has simple and
589	  deterministic reclaim properties that make it preferable to a higher
590	  density approach when reclaim will be used.
591
592config Z3FOLD
593	tristate "Up to 3x density storage for compressed pages"
594	depends on ZPOOL
595	default n
596	help
597	  A special purpose allocator for storing compressed pages.
598	  It is designed to store up to three compressed pages per physical
599	  page. It is a ZBUD derivative so the simplicity and determinism are
600	  still there.
601
602config ZSMALLOC
603	tristate "Memory allocator for compressed pages"
604	depends on MMU
605	default n
606	help
607	  zsmalloc is a slab-based memory allocator designed to store
608	  compressed RAM pages.  zsmalloc uses virtual memory mapping
609	  in order to reduce fragmentation.  However, this results in a
610	  non-standard allocator interface where a handle, not a pointer, is
611	  returned by an alloc().  This handle must be mapped in order to
612	  access the allocated space.
613
614config PGTABLE_MAPPING
615	bool "Use page table mapping to access object in zsmalloc"
616	depends on ZSMALLOC
617	help
618	  By default, zsmalloc uses a copy-based object mapping method to
619	  access allocations that span two pages. However, if a particular
620	  architecture (ex, ARM) performs VM mapping faster than copying,
621	  then you should select this. This causes zsmalloc to use page table
622	  mapping rather than copying for object mapping.
623
624	  You can check speed with zsmalloc benchmark:
625	  https://github.com/spartacus06/zsmapbench
626
627config ZSMALLOC_STAT
628	bool "Export zsmalloc statistics"
629	depends on ZSMALLOC
630	select DEBUG_FS
631	help
632	  This option enables code in the zsmalloc to collect various
633	  statistics about whats happening in zsmalloc and exports that
634	  information to userspace via debugfs.
635	  If unsure, say N.
636
637config GENERIC_EARLY_IOREMAP
638	bool
639
640config MAX_STACK_SIZE_MB
641	int "Maximum user stack size for 32-bit processes (MB)"
642	default 80
643	range 8 256 if METAG
644	range 8 2048
645	depends on STACK_GROWSUP && (!64BIT || COMPAT)
646	help
647	  This is the maximum stack size in Megabytes in the VM layout of 32-bit
648	  user processes when the stack grows upwards (currently only on parisc
649	  and metag arch). The stack will be located at the highest memory
650	  address minus the given value, unless the RLIMIT_STACK hard limit is
651	  changed to a smaller value in which case that is used.
652
653	  A sane initial value is 80 MB.
654
655# For architectures that support deferred memory initialisation
656config ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
657	bool
658
659config DEFERRED_STRUCT_PAGE_INIT
660	bool "Defer initialisation of struct pages to kthreads"
661	default n
662	depends on ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
663	depends on NO_BOOTMEM && MEMORY_HOTPLUG
664	depends on !FLATMEM
665	help
666	  Ordinarily all struct pages are initialised during early boot in a
667	  single thread. On very large machines this can take a considerable
668	  amount of time. If this option is set, large machines will bring up
669	  a subset of memmap at boot and then initialise the rest in parallel
670	  by starting one-off "pgdatinitX" kernel thread for each node X. This
671	  has a potential performance impact on processes running early in the
672	  lifetime of the system until these kthreads finish the
673	  initialisation.
674
675config IDLE_PAGE_TRACKING
676	bool "Enable idle page tracking"
677	depends on SYSFS && MMU
678	select PAGE_EXTENSION if !64BIT
679	help
680	  This feature allows to estimate the amount of user pages that have
681	  not been touched during a given period of time. This information can
682	  be useful to tune memory cgroup limits and/or for job placement
683	  within a compute cluster.
684
685	  See Documentation/vm/idle_page_tracking.txt for more details.
686
687config ZONE_DEVICE
688	bool "Device memory (pmem, etc...) hotplug support"
689	depends on MEMORY_HOTPLUG
690	depends on MEMORY_HOTREMOVE
691	depends on SPARSEMEM_VMEMMAP
692	depends on X86_64 #arch_add_memory() comprehends device memory
693
694	help
695	  Device memory hotplug support allows for establishing pmem,
696	  or other device driver discovered memory regions, in the
697	  memmap. This allows pfn_to_page() lookups of otherwise
698	  "device-physical" addresses which is needed for using a DAX
699	  mapping in an O_DIRECT operation, among other things.
700
701	  If FS_DAX is enabled, then say Y.
702
703config FRAME_VECTOR
704	bool
705
706config ARCH_USES_HIGH_VMA_FLAGS
707	bool
708config ARCH_HAS_PKEYS
709	bool
710