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1config SELECT_MEMORY_MODEL
2 def_bool y
3 depends on ARCH_SELECT_MEMORY_MODEL
4
5choice
6 prompt "Memory model"
7 depends on SELECT_MEMORY_MODEL
8 default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
9 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
10 default FLATMEM_MANUAL
11
12config FLATMEM_MANUAL
13 bool "Flat Memory"
14 depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
15 help
16 This option allows you to change some of the ways that
17 Linux manages its memory internally. Most users will
18 only have one option here: FLATMEM. This is normal
19 and a correct option.
20
21 Some users of more advanced features like NUMA and
22 memory hotplug may have different options here.
23 DISCONTIGMEM is a more mature, better tested system,
24 but is incompatible with memory hotplug and may suffer
25 decreased performance over SPARSEMEM. If unsure between
26 "Sparse Memory" and "Discontiguous Memory", choose
27 "Discontiguous Memory".
28
29 If unsure, choose this option (Flat Memory) over any other.
30
31config DISCONTIGMEM_MANUAL
32 bool "Discontiguous Memory"
33 depends on ARCH_DISCONTIGMEM_ENABLE
34 help
35 This option provides enhanced support for discontiguous
36 memory systems, over FLATMEM. These systems have holes
37 in their physical address spaces, and this option provides
38 more efficient handling of these holes. However, the vast
39 majority of hardware has quite flat address spaces, and
40 can have degraded performance from the extra overhead that
41 this option imposes.
42
43 Many NUMA configurations will have this as the only option.
44
45 If unsure, choose "Flat Memory" over this option.
46
47config SPARSEMEM_MANUAL
48 bool "Sparse Memory"
49 depends on ARCH_SPARSEMEM_ENABLE
50 help
51 This will be the only option for some systems, including
52 memory hotplug systems. This is normal.
53
54 For many other systems, this will be an alternative to
55 "Discontiguous Memory". This option provides some potential
56 performance benefits, along with decreased code complexity,
57 but it is newer, and more experimental.
58
59 If unsure, choose "Discontiguous Memory" or "Flat Memory"
60 over this option.
61
62endchoice
63
64config DISCONTIGMEM
65 def_bool y
66 depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
67
68config SPARSEMEM
69 def_bool y
70 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
71
72config FLATMEM
73 def_bool y
74 depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
75
76config FLAT_NODE_MEM_MAP
77 def_bool y
78 depends on !SPARSEMEM
79
80#
81# Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
82# to represent different areas of memory. This variable allows
83# those dependencies to exist individually.
84#
85config NEED_MULTIPLE_NODES
86 def_bool y
87 depends on DISCONTIGMEM || NUMA
88
89config HAVE_MEMORY_PRESENT
90 def_bool y
91 depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
92
93#
94# SPARSEMEM_EXTREME (which is the default) does some bootmem
95# allocations when memory_present() is called. If this cannot
96# be done on your architecture, select this option. However,
97# statically allocating the mem_section[] array can potentially
98# consume vast quantities of .bss, so be careful.
99#
100# This option will also potentially produce smaller runtime code
101# with gcc 3.4 and later.
102#
103config SPARSEMEM_STATIC
104 bool
105
106#
107# Architecture platforms which require a two level mem_section in SPARSEMEM
108# must select this option. This is usually for architecture platforms with
109# an extremely sparse physical address space.
110#
111config SPARSEMEM_EXTREME
112 def_bool y
113 depends on SPARSEMEM && !SPARSEMEM_STATIC
114
115config SPARSEMEM_VMEMMAP_ENABLE
116 bool
117
118config SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
119 def_bool y
120 depends on SPARSEMEM && X86_64
121
122config SPARSEMEM_VMEMMAP
123 bool "Sparse Memory virtual memmap"
124 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
125 default y
126 help
127 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
128 pfn_to_page and page_to_pfn operations. This is the most
129 efficient option when sufficient kernel resources are available.
130
131config HAVE_MEMBLOCK
132 bool
133
134config HAVE_MEMBLOCK_NODE_MAP
135 bool
136
137config HAVE_MEMBLOCK_PHYS_MAP
138 bool
139
140config HAVE_GENERIC_RCU_GUP
141 bool
142
143config ARCH_DISCARD_MEMBLOCK
144 bool
145
146config NO_BOOTMEM
147 bool
148
149config MEMORY_ISOLATION
150 bool
151
152config MOVABLE_NODE
153 bool "Enable to assign a node which has only movable memory"
154 depends on HAVE_MEMBLOCK
155 depends on NO_BOOTMEM
156 depends on X86_64
157 depends on NUMA
158 default n
159 help
160 Allow a node to have only movable memory. Pages used by the kernel,
161 such as direct mapping pages cannot be migrated. So the corresponding
162 memory device cannot be hotplugged. This option allows the following
163 two things:
164 - When the system is booting, node full of hotpluggable memory can
165 be arranged to have only movable memory so that the whole node can
166 be hot-removed. (need movable_node boot option specified).
167 - After the system is up, the option allows users to online all the
168 memory of a node as movable memory so that the whole node can be
169 hot-removed.
170
171 Users who don't use the memory hotplug feature are fine with this
172 option on since they don't specify movable_node boot option or they
173 don't online memory as movable.
174
175 Say Y here if you want to hotplug a whole node.
176 Say N here if you want kernel to use memory on all nodes evenly.
177
178#
179# Only be set on architectures that have completely implemented memory hotplug
180# feature. If you are not sure, don't touch it.
181#
182config HAVE_BOOTMEM_INFO_NODE
183 def_bool n
184
185# eventually, we can have this option just 'select SPARSEMEM'
186config MEMORY_HOTPLUG
187 bool "Allow for memory hot-add"
188 depends on SPARSEMEM || X86_64_ACPI_NUMA
189 depends on ARCH_ENABLE_MEMORY_HOTPLUG
190
191config MEMORY_HOTPLUG_SPARSE
192 def_bool y
193 depends on SPARSEMEM && MEMORY_HOTPLUG
194
195config MEMORY_HOTREMOVE
196 bool "Allow for memory hot remove"
197 select MEMORY_ISOLATION
198 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
199 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
200 depends on MIGRATION
201
202# Heavily threaded applications may benefit from splitting the mm-wide
203# page_table_lock, so that faults on different parts of the user address
204# space can be handled with less contention: split it at this NR_CPUS.
205# Default to 4 for wider testing, though 8 might be more appropriate.
206# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
207# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
208# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
209#
210config SPLIT_PTLOCK_CPUS
211 int
212 default "999999" if !MMU
213 default "999999" if ARM && !CPU_CACHE_VIPT
214 default "999999" if PARISC && !PA20
215 default "4"
216
217config ARCH_ENABLE_SPLIT_PMD_PTLOCK
218 bool
219
220#
221# support for memory balloon
222config MEMORY_BALLOON
223 bool
224
225#
226# support for memory balloon compaction
227config BALLOON_COMPACTION
228 bool "Allow for balloon memory compaction/migration"
229 def_bool y
230 depends on COMPACTION && MEMORY_BALLOON
231 help
232 Memory fragmentation introduced by ballooning might reduce
233 significantly the number of 2MB contiguous memory blocks that can be
234 used within a guest, thus imposing performance penalties associated
235 with the reduced number of transparent huge pages that could be used
236 by the guest workload. Allowing the compaction & migration for memory
237 pages enlisted as being part of memory balloon devices avoids the
238 scenario aforementioned and helps improving memory defragmentation.
239
240#
241# support for memory compaction
242config COMPACTION
243 bool "Allow for memory compaction"
244 def_bool y
245 select MIGRATION
246 depends on MMU
247 help
248 Allows the compaction of memory for the allocation of huge pages.
249
250#
251# support for page migration
252#
253config MIGRATION
254 bool "Page migration"
255 def_bool y
256 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
257 help
258 Allows the migration of the physical location of pages of processes
259 while the virtual addresses are not changed. This is useful in
260 two situations. The first is on NUMA systems to put pages nearer
261 to the processors accessing. The second is when allocating huge
262 pages as migration can relocate pages to satisfy a huge page
263 allocation instead of reclaiming.
264
265config ARCH_ENABLE_HUGEPAGE_MIGRATION
266 bool
267
268config PHYS_ADDR_T_64BIT
269 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
270
271config ZONE_DMA_FLAG
272 int
273 default "0" if !ZONE_DMA
274 default "1"
275
276config BOUNCE
277 bool "Enable bounce buffers"
278 default y
279 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
280 help
281 Enable bounce buffers for devices that cannot access
282 the full range of memory available to the CPU. Enabled
283 by default when ZONE_DMA or HIGHMEM is selected, but you
284 may say n to override this.
285
286# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
287# have more than 4GB of memory, but we don't currently use the IOTLB to present
288# a 32-bit address to OHCI. So we need to use a bounce pool instead.
289config NEED_BOUNCE_POOL
290 bool
291 default y if TILE && USB_OHCI_HCD
292
293config NR_QUICK
294 int
295 depends on QUICKLIST
296 default "2" if AVR32
297 default "1"
298
299config VIRT_TO_BUS
300 bool
301 help
302 An architecture should select this if it implements the
303 deprecated interface virt_to_bus(). All new architectures
304 should probably not select this.
305
306
307config MMU_NOTIFIER
308 bool
309 select SRCU
310
311config KSM
312 bool "Enable KSM for page merging"
313 depends on MMU
314 help
315 Enable Kernel Samepage Merging: KSM periodically scans those areas
316 of an application's address space that an app has advised may be
317 mergeable. When it finds pages of identical content, it replaces
318 the many instances by a single page with that content, so
319 saving memory until one or another app needs to modify the content.
320 Recommended for use with KVM, or with other duplicative applications.
321 See Documentation/vm/ksm.txt for more information: KSM is inactive
322 until a program has madvised that an area is MADV_MERGEABLE, and
323 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
324
325config DEFAULT_MMAP_MIN_ADDR
326 int "Low address space to protect from user allocation"
327 depends on MMU
328 default 4096
329 help
330 This is the portion of low virtual memory which should be protected
331 from userspace allocation. Keeping a user from writing to low pages
332 can help reduce the impact of kernel NULL pointer bugs.
333
334 For most ia64, ppc64 and x86 users with lots of address space
335 a value of 65536 is reasonable and should cause no problems.
336 On arm and other archs it should not be higher than 32768.
337 Programs which use vm86 functionality or have some need to map
338 this low address space will need CAP_SYS_RAWIO or disable this
339 protection by setting the value to 0.
340
341 This value can be changed after boot using the
342 /proc/sys/vm/mmap_min_addr tunable.
343
344config ARCH_SUPPORTS_MEMORY_FAILURE
345 bool
346
347config MEMORY_FAILURE
348 depends on MMU
349 depends on ARCH_SUPPORTS_MEMORY_FAILURE
350 bool "Enable recovery from hardware memory errors"
351 select MEMORY_ISOLATION
352 select RAS
353 help
354 Enables code to recover from some memory failures on systems
355 with MCA recovery. This allows a system to continue running
356 even when some of its memory has uncorrected errors. This requires
357 special hardware support and typically ECC memory.
358
359config HWPOISON_INJECT
360 tristate "HWPoison pages injector"
361 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
362 select PROC_PAGE_MONITOR
363
364config NOMMU_INITIAL_TRIM_EXCESS
365 int "Turn on mmap() excess space trimming before booting"
366 depends on !MMU
367 default 1
368 help
369 The NOMMU mmap() frequently needs to allocate large contiguous chunks
370 of memory on which to store mappings, but it can only ask the system
371 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
372 more than it requires. To deal with this, mmap() is able to trim off
373 the excess and return it to the allocator.
374
375 If trimming is enabled, the excess is trimmed off and returned to the
376 system allocator, which can cause extra fragmentation, particularly
377 if there are a lot of transient processes.
378
379 If trimming is disabled, the excess is kept, but not used, which for
380 long-term mappings means that the space is wasted.
381
382 Trimming can be dynamically controlled through a sysctl option
383 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
384 excess pages there must be before trimming should occur, or zero if
385 no trimming is to occur.
386
387 This option specifies the initial value of this option. The default
388 of 1 says that all excess pages should be trimmed.
389
390 See Documentation/nommu-mmap.txt for more information.
391
392config TRANSPARENT_HUGEPAGE
393 bool "Transparent Hugepage Support"
394 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
395 select COMPACTION
396 help
397 Transparent Hugepages allows the kernel to use huge pages and
398 huge tlb transparently to the applications whenever possible.
399 This feature can improve computing performance to certain
400 applications by speeding up page faults during memory
401 allocation, by reducing the number of tlb misses and by speeding
402 up the pagetable walking.
403
404 If memory constrained on embedded, you may want to say N.
405
406choice
407 prompt "Transparent Hugepage Support sysfs defaults"
408 depends on TRANSPARENT_HUGEPAGE
409 default TRANSPARENT_HUGEPAGE_ALWAYS
410 help
411 Selects the sysfs defaults for Transparent Hugepage Support.
412
413 config TRANSPARENT_HUGEPAGE_ALWAYS
414 bool "always"
415 help
416 Enabling Transparent Hugepage always, can increase the
417 memory footprint of applications without a guaranteed
418 benefit but it will work automatically for all applications.
419
420 config TRANSPARENT_HUGEPAGE_MADVISE
421 bool "madvise"
422 help
423 Enabling Transparent Hugepage madvise, will only provide a
424 performance improvement benefit to the applications using
425 madvise(MADV_HUGEPAGE) but it won't risk to increase the
426 memory footprint of applications without a guaranteed
427 benefit.
428endchoice
429
430#
431# UP and nommu archs use km based percpu allocator
432#
433config NEED_PER_CPU_KM
434 depends on !SMP
435 bool
436 default y
437
438config CLEANCACHE
439 bool "Enable cleancache driver to cache clean pages if tmem is present"
440 default n
441 help
442 Cleancache can be thought of as a page-granularity victim cache
443 for clean pages that the kernel's pageframe replacement algorithm
444 (PFRA) would like to keep around, but can't since there isn't enough
445 memory. So when the PFRA "evicts" a page, it first attempts to use
446 cleancache code to put the data contained in that page into
447 "transcendent memory", memory that is not directly accessible or
448 addressable by the kernel and is of unknown and possibly
449 time-varying size. And when a cleancache-enabled
450 filesystem wishes to access a page in a file on disk, it first
451 checks cleancache to see if it already contains it; if it does,
452 the page is copied into the kernel and a disk access is avoided.
453 When a transcendent memory driver is available (such as zcache or
454 Xen transcendent memory), a significant I/O reduction
455 may be achieved. When none is available, all cleancache calls
456 are reduced to a single pointer-compare-against-NULL resulting
457 in a negligible performance hit.
458
459 If unsure, say Y to enable cleancache
460
461config FRONTSWAP
462 bool "Enable frontswap to cache swap pages if tmem is present"
463 depends on SWAP
464 default n
465 help
466 Frontswap is so named because it can be thought of as the opposite
467 of a "backing" store for a swap device. The data is stored into
468 "transcendent memory", memory that is not directly accessible or
469 addressable by the kernel and is of unknown and possibly
470 time-varying size. When space in transcendent memory is available,
471 a significant swap I/O reduction may be achieved. When none is
472 available, all frontswap calls are reduced to a single pointer-
473 compare-against-NULL resulting in a negligible performance hit
474 and swap data is stored as normal on the matching swap device.
475
476 If unsure, say Y to enable frontswap.
477
478config CMA
479 bool "Contiguous Memory Allocator"
480 depends on HAVE_MEMBLOCK && MMU
481 select MIGRATION
482 select MEMORY_ISOLATION
483 help
484 This enables the Contiguous Memory Allocator which allows other
485 subsystems to allocate big physically-contiguous blocks of memory.
486 CMA reserves a region of memory and allows only movable pages to
487 be allocated from it. This way, the kernel can use the memory for
488 pagecache and when a subsystem requests for contiguous area, the
489 allocated pages are migrated away to serve the contiguous request.
490
491 If unsure, say "n".
492
493config CMA_DEBUG
494 bool "CMA debug messages (DEVELOPMENT)"
495 depends on DEBUG_KERNEL && CMA
496 help
497 Turns on debug messages in CMA. This produces KERN_DEBUG
498 messages for every CMA call as well as various messages while
499 processing calls such as dma_alloc_from_contiguous().
500 This option does not affect warning and error messages.
501
502config CMA_DEBUGFS
503 bool "CMA debugfs interface"
504 depends on CMA && DEBUG_FS
505 help
506 Turns on the DebugFS interface for CMA.
507
508config CMA_AREAS
509 int "Maximum count of the CMA areas"
510 depends on CMA
511 default 7
512 help
513 CMA allows to create CMA areas for particular purpose, mainly,
514 used as device private area. This parameter sets the maximum
515 number of CMA area in the system.
516
517 If unsure, leave the default value "7".
518
519config MEM_SOFT_DIRTY
520 bool "Track memory changes"
521 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
522 select PROC_PAGE_MONITOR
523 help
524 This option enables memory changes tracking by introducing a
525 soft-dirty bit on pte-s. This bit it set when someone writes
526 into a page just as regular dirty bit, but unlike the latter
527 it can be cleared by hands.
528
529 See Documentation/vm/soft-dirty.txt for more details.
530
531config ZSWAP
532 bool "Compressed cache for swap pages (EXPERIMENTAL)"
533 depends on FRONTSWAP && CRYPTO=y
534 select CRYPTO_LZO
535 select ZPOOL
536 default n
537 help
538 A lightweight compressed cache for swap pages. It takes
539 pages that are in the process of being swapped out and attempts to
540 compress them into a dynamically allocated RAM-based memory pool.
541 This can result in a significant I/O reduction on swap device and,
542 in the case where decompressing from RAM is faster that swap device
543 reads, can also improve workload performance.
544
545 This is marked experimental because it is a new feature (as of
546 v3.11) that interacts heavily with memory reclaim. While these
547 interactions don't cause any known issues on simple memory setups,
548 they have not be fully explored on the large set of potential
549 configurations and workloads that exist.
550
551config ZPOOL
552 tristate "Common API for compressed memory storage"
553 default n
554 help
555 Compressed memory storage API. This allows using either zbud or
556 zsmalloc.
557
558config ZBUD
559 tristate "Low density storage for compressed pages"
560 default n
561 help
562 A special purpose allocator for storing compressed pages.
563 It is designed to store up to two compressed pages per physical
564 page. While this design limits storage density, it has simple and
565 deterministic reclaim properties that make it preferable to a higher
566 density approach when reclaim will be used.
567
568config ZSMALLOC
569 tristate "Memory allocator for compressed pages"
570 depends on MMU
571 default n
572 help
573 zsmalloc is a slab-based memory allocator designed to store
574 compressed RAM pages. zsmalloc uses virtual memory mapping
575 in order to reduce fragmentation. However, this results in a
576 non-standard allocator interface where a handle, not a pointer, is
577 returned by an alloc(). This handle must be mapped in order to
578 access the allocated space.
579
580config PGTABLE_MAPPING
581 bool "Use page table mapping to access object in zsmalloc"
582 depends on ZSMALLOC
583 help
584 By default, zsmalloc uses a copy-based object mapping method to
585 access allocations that span two pages. However, if a particular
586 architecture (ex, ARM) performs VM mapping faster than copying,
587 then you should select this. This causes zsmalloc to use page table
588 mapping rather than copying for object mapping.
589
590 You can check speed with zsmalloc benchmark:
591 https://github.com/spartacus06/zsmapbench
592
593config ZSMALLOC_STAT
594 bool "Export zsmalloc statistics"
595 depends on ZSMALLOC
596 select DEBUG_FS
597 help
598 This option enables code in the zsmalloc to collect various
599 statistics about whats happening in zsmalloc and exports that
600 information to userspace via debugfs.
601 If unsure, say N.
602
603config GENERIC_EARLY_IOREMAP
604 bool
605
606config MAX_STACK_SIZE_MB
607 int "Maximum user stack size for 32-bit processes (MB)"
608 default 80
609 range 8 256 if METAG
610 range 8 2048
611 depends on STACK_GROWSUP && (!64BIT || COMPAT)
612 help
613 This is the maximum stack size in Megabytes in the VM layout of 32-bit
614 user processes when the stack grows upwards (currently only on parisc
615 and metag arch). The stack will be located at the highest memory
616 address minus the given value, unless the RLIMIT_STACK hard limit is
617 changed to a smaller value in which case that is used.
618
619 A sane initial value is 80 MB.
620
621# For architectures that support deferred memory initialisation
622config ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
623 bool
624
625config DEFERRED_STRUCT_PAGE_INIT
626 bool "Defer initialisation of struct pages to kthreads"
627 default n
628 depends on ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
629 depends on MEMORY_HOTPLUG
630 help
631 Ordinarily all struct pages are initialised during early boot in a
632 single thread. On very large machines this can take a considerable
633 amount of time. If this option is set, large machines will bring up
634 a subset of memmap at boot and then initialise the rest in parallel
635 by starting one-off "pgdatinitX" kernel thread for each node X. This
636 has a potential performance impact on processes running early in the
637 lifetime of the system until these kthreads finish the
638 initialisation.
639
640config IDLE_PAGE_TRACKING
641 bool "Enable idle page tracking"
642 depends on SYSFS && MMU
643 select PAGE_EXTENSION if !64BIT
644 help
645 This feature allows to estimate the amount of user pages that have
646 not been touched during a given period of time. This information can
647 be useful to tune memory cgroup limits and/or for job placement
648 within a compute cluster.
649
650 See Documentation/vm/idle_page_tracking.txt for more details.
651
652config ZONE_DEVICE
653 bool "Device memory (pmem, etc...) hotplug support" if EXPERT
654 depends on MEMORY_HOTPLUG
655 depends on MEMORY_HOTREMOVE
656 depends on SPARSEMEM_VMEMMAP
657 depends on X86_64 #arch_add_memory() comprehends device memory
658
659 help
660 Device memory hotplug support allows for establishing pmem,
661 or other device driver discovered memory regions, in the
662 memmap. This allows pfn_to_page() lookups of otherwise
663 "device-physical" addresses which is needed for using a DAX
664 mapping in an O_DIRECT operation, among other things.
665
666 If FS_DAX is enabled, then say Y.
667
668config FRAME_VECTOR
669 bool
670
671config ARCH_USES_HIGH_VMA_FLAGS
672 bool
673config ARCH_HAS_PKEYS
674 bool
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 boolean
133
134config HAVE_MEMBLOCK_NODE_MAP
135 boolean
136
137config ARCH_DISCARD_MEMBLOCK
138 boolean
139
140config NO_BOOTMEM
141 boolean
142
143config MEMORY_ISOLATION
144 boolean
145
146config MOVABLE_NODE
147 boolean "Enable to assign a node which has only movable memory"
148 depends on HAVE_MEMBLOCK
149 depends on NO_BOOTMEM
150 depends on X86_64
151 depends on NUMA
152 default n
153 help
154 Allow a node to have only movable memory. Pages used by the kernel,
155 such as direct mapping pages cannot be migrated. So the corresponding
156 memory device cannot be hotplugged. This option allows the following
157 two things:
158 - When the system is booting, node full of hotpluggable memory can
159 be arranged to have only movable memory so that the whole node can
160 be hot-removed. (need movable_node boot option specified).
161 - After the system is up, the option allows users to online all the
162 memory of a node as movable memory so that the whole node can be
163 hot-removed.
164
165 Users who don't use the memory hotplug feature are fine with this
166 option on since they don't specify movable_node boot option or they
167 don't online memory as movable.
168
169 Say Y here if you want to hotplug a whole node.
170 Say N here if you want kernel to use memory on all nodes evenly.
171
172#
173# Only be set on architectures that have completely implemented memory hotplug
174# feature. If you are not sure, don't touch it.
175#
176config HAVE_BOOTMEM_INFO_NODE
177 def_bool n
178
179# eventually, we can have this option just 'select SPARSEMEM'
180config MEMORY_HOTPLUG
181 bool "Allow for memory hot-add"
182 depends on SPARSEMEM || X86_64_ACPI_NUMA
183 depends on ARCH_ENABLE_MEMORY_HOTPLUG
184 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
185
186config MEMORY_HOTPLUG_SPARSE
187 def_bool y
188 depends on SPARSEMEM && MEMORY_HOTPLUG
189
190config MEMORY_HOTREMOVE
191 bool "Allow for memory hot remove"
192 select MEMORY_ISOLATION
193 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
194 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
195 depends on MIGRATION
196
197#
198# If we have space for more page flags then we can enable additional
199# optimizations and functionality.
200#
201# Regular Sparsemem takes page flag bits for the sectionid if it does not
202# use a virtual memmap. Disable extended page flags for 32 bit platforms
203# that require the use of a sectionid in the page flags.
204#
205config PAGEFLAGS_EXTENDED
206 def_bool y
207 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
208
209# Heavily threaded applications may benefit from splitting the mm-wide
210# page_table_lock, so that faults on different parts of the user address
211# space can be handled with less contention: split it at this NR_CPUS.
212# Default to 4 for wider testing, though 8 might be more appropriate.
213# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
214# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
215# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
216#
217config SPLIT_PTLOCK_CPUS
218 int
219 default "999999" if !MMU
220 default "999999" if ARM && !CPU_CACHE_VIPT
221 default "999999" if PARISC && !PA20
222 default "4"
223
224config ARCH_ENABLE_SPLIT_PMD_PTLOCK
225 boolean
226
227#
228# support for memory balloon compaction
229config BALLOON_COMPACTION
230 bool "Allow for balloon memory compaction/migration"
231 def_bool y
232 depends on COMPACTION && VIRTIO_BALLOON
233 help
234 Memory fragmentation introduced by ballooning might reduce
235 significantly the number of 2MB contiguous memory blocks that can be
236 used within a guest, thus imposing performance penalties associated
237 with the reduced number of transparent huge pages that could be used
238 by the guest workload. Allowing the compaction & migration for memory
239 pages enlisted as being part of memory balloon devices avoids the
240 scenario aforementioned and helps improving memory defragmentation.
241
242#
243# support for memory compaction
244config COMPACTION
245 bool "Allow for memory compaction"
246 def_bool y
247 select MIGRATION
248 depends on MMU
249 help
250 Allows the compaction of memory for the allocation of huge pages.
251
252#
253# support for page migration
254#
255config MIGRATION
256 bool "Page migration"
257 def_bool y
258 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
259 help
260 Allows the migration of the physical location of pages of processes
261 while the virtual addresses are not changed. This is useful in
262 two situations. The first is on NUMA systems to put pages nearer
263 to the processors accessing. The second is when allocating huge
264 pages as migration can relocate pages to satisfy a huge page
265 allocation instead of reclaiming.
266
267config PHYS_ADDR_T_64BIT
268 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
269
270config ZONE_DMA_FLAG
271 int
272 default "0" if !ZONE_DMA
273 default "1"
274
275config BOUNCE
276 bool "Enable bounce buffers"
277 default y
278 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
279 help
280 Enable bounce buffers for devices that cannot access
281 the full range of memory available to the CPU. Enabled
282 by default when ZONE_DMA or HIGHMEM is selected, but you
283 may say n to override this.
284
285# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
286# have more than 4GB of memory, but we don't currently use the IOTLB to present
287# a 32-bit address to OHCI. So we need to use a bounce pool instead.
288#
289# We also use the bounce pool to provide stable page writes for jbd. jbd
290# initiates buffer writeback without locking the page or setting PG_writeback,
291# and fixing that behavior (a second time; jbd2 doesn't have this problem) is
292# a major rework effort. Instead, use the bounce buffer to snapshot pages
293# (until jbd goes away). The only jbd user is ext3.
294config NEED_BOUNCE_POOL
295 bool
296 default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD)
297
298config NR_QUICK
299 int
300 depends on QUICKLIST
301 default "2" if AVR32
302 default "1"
303
304config VIRT_TO_BUS
305 bool
306 help
307 An architecture should select this if it implements the
308 deprecated interface virt_to_bus(). All new architectures
309 should probably not select this.
310
311
312config MMU_NOTIFIER
313 bool
314
315config KSM
316 bool "Enable KSM for page merging"
317 depends on MMU
318 help
319 Enable Kernel Samepage Merging: KSM periodically scans those areas
320 of an application's address space that an app has advised may be
321 mergeable. When it finds pages of identical content, it replaces
322 the many instances by a single page with that content, so
323 saving memory until one or another app needs to modify the content.
324 Recommended for use with KVM, or with other duplicative applications.
325 See Documentation/vm/ksm.txt for more information: KSM is inactive
326 until a program has madvised that an area is MADV_MERGEABLE, and
327 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
328
329config DEFAULT_MMAP_MIN_ADDR
330 int "Low address space to protect from user allocation"
331 depends on MMU
332 default 4096
333 help
334 This is the portion of low virtual memory which should be protected
335 from userspace allocation. Keeping a user from writing to low pages
336 can help reduce the impact of kernel NULL pointer bugs.
337
338 For most ia64, ppc64 and x86 users with lots of address space
339 a value of 65536 is reasonable and should cause no problems.
340 On arm and other archs it should not be higher than 32768.
341 Programs which use vm86 functionality or have some need to map
342 this low address space will need CAP_SYS_RAWIO or disable this
343 protection by setting the value to 0.
344
345 This value can be changed after boot using the
346 /proc/sys/vm/mmap_min_addr tunable.
347
348config ARCH_SUPPORTS_MEMORY_FAILURE
349 bool
350
351config MEMORY_FAILURE
352 depends on MMU
353 depends on ARCH_SUPPORTS_MEMORY_FAILURE
354 bool "Enable recovery from hardware memory errors"
355 select MEMORY_ISOLATION
356 help
357 Enables code to recover from some memory failures on systems
358 with MCA recovery. This allows a system to continue running
359 even when some of its memory has uncorrected errors. This requires
360 special hardware support and typically ECC memory.
361
362config HWPOISON_INJECT
363 tristate "HWPoison pages injector"
364 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
365 select PROC_PAGE_MONITOR
366
367config NOMMU_INITIAL_TRIM_EXCESS
368 int "Turn on mmap() excess space trimming before booting"
369 depends on !MMU
370 default 1
371 help
372 The NOMMU mmap() frequently needs to allocate large contiguous chunks
373 of memory on which to store mappings, but it can only ask the system
374 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
375 more than it requires. To deal with this, mmap() is able to trim off
376 the excess and return it to the allocator.
377
378 If trimming is enabled, the excess is trimmed off and returned to the
379 system allocator, which can cause extra fragmentation, particularly
380 if there are a lot of transient processes.
381
382 If trimming is disabled, the excess is kept, but not used, which for
383 long-term mappings means that the space is wasted.
384
385 Trimming can be dynamically controlled through a sysctl option
386 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
387 excess pages there must be before trimming should occur, or zero if
388 no trimming is to occur.
389
390 This option specifies the initial value of this option. The default
391 of 1 says that all excess pages should be trimmed.
392
393 See Documentation/nommu-mmap.txt for more information.
394
395config TRANSPARENT_HUGEPAGE
396 bool "Transparent Hugepage Support"
397 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
398 select COMPACTION
399 help
400 Transparent Hugepages allows the kernel to use huge pages and
401 huge tlb transparently to the applications whenever possible.
402 This feature can improve computing performance to certain
403 applications by speeding up page faults during memory
404 allocation, by reducing the number of tlb misses and by speeding
405 up the pagetable walking.
406
407 If memory constrained on embedded, you may want to say N.
408
409choice
410 prompt "Transparent Hugepage Support sysfs defaults"
411 depends on TRANSPARENT_HUGEPAGE
412 default TRANSPARENT_HUGEPAGE_ALWAYS
413 help
414 Selects the sysfs defaults for Transparent Hugepage Support.
415
416 config TRANSPARENT_HUGEPAGE_ALWAYS
417 bool "always"
418 help
419 Enabling Transparent Hugepage always, can increase the
420 memory footprint of applications without a guaranteed
421 benefit but it will work automatically for all applications.
422
423 config TRANSPARENT_HUGEPAGE_MADVISE
424 bool "madvise"
425 help
426 Enabling Transparent Hugepage madvise, will only provide a
427 performance improvement benefit to the applications using
428 madvise(MADV_HUGEPAGE) but it won't risk to increase the
429 memory footprint of applications without a guaranteed
430 benefit.
431endchoice
432
433config CROSS_MEMORY_ATTACH
434 bool "Cross Memory Support"
435 depends on MMU
436 default y
437 help
438 Enabling this option adds the system calls process_vm_readv and
439 process_vm_writev which allow a process with the correct privileges
440 to directly read from or write to to another process's address space.
441 See the man page for more details.
442
443#
444# UP and nommu archs use km based percpu allocator
445#
446config NEED_PER_CPU_KM
447 depends on !SMP
448 bool
449 default y
450
451config CLEANCACHE
452 bool "Enable cleancache driver to cache clean pages if tmem is present"
453 default n
454 help
455 Cleancache can be thought of as a page-granularity victim cache
456 for clean pages that the kernel's pageframe replacement algorithm
457 (PFRA) would like to keep around, but can't since there isn't enough
458 memory. So when the PFRA "evicts" a page, it first attempts to use
459 cleancache code to put the data contained in that page into
460 "transcendent memory", memory that is not directly accessible or
461 addressable by the kernel and is of unknown and possibly
462 time-varying size. And when a cleancache-enabled
463 filesystem wishes to access a page in a file on disk, it first
464 checks cleancache to see if it already contains it; if it does,
465 the page is copied into the kernel and a disk access is avoided.
466 When a transcendent memory driver is available (such as zcache or
467 Xen transcendent memory), a significant I/O reduction
468 may be achieved. When none is available, all cleancache calls
469 are reduced to a single pointer-compare-against-NULL resulting
470 in a negligible performance hit.
471
472 If unsure, say Y to enable cleancache
473
474config FRONTSWAP
475 bool "Enable frontswap to cache swap pages if tmem is present"
476 depends on SWAP
477 default n
478 help
479 Frontswap is so named because it can be thought of as the opposite
480 of a "backing" store for a swap device. The data is stored into
481 "transcendent memory", memory that is not directly accessible or
482 addressable by the kernel and is of unknown and possibly
483 time-varying size. When space in transcendent memory is available,
484 a significant swap I/O reduction may be achieved. When none is
485 available, all frontswap calls are reduced to a single pointer-
486 compare-against-NULL resulting in a negligible performance hit
487 and swap data is stored as normal on the matching swap device.
488
489 If unsure, say Y to enable frontswap.
490
491config CMA
492 bool "Contiguous Memory Allocator"
493 depends on HAVE_MEMBLOCK && MMU
494 select MIGRATION
495 select MEMORY_ISOLATION
496 help
497 This enables the Contiguous Memory Allocator which allows other
498 subsystems to allocate big physically-contiguous blocks of memory.
499 CMA reserves a region of memory and allows only movable pages to
500 be allocated from it. This way, the kernel can use the memory for
501 pagecache and when a subsystem requests for contiguous area, the
502 allocated pages are migrated away to serve the contiguous request.
503
504 If unsure, say "n".
505
506config CMA_DEBUG
507 bool "CMA debug messages (DEVELOPMENT)"
508 depends on DEBUG_KERNEL && CMA
509 help
510 Turns on debug messages in CMA. This produces KERN_DEBUG
511 messages for every CMA call as well as various messages while
512 processing calls such as dma_alloc_from_contiguous().
513 This option does not affect warning and error messages.
514
515config ZBUD
516 tristate
517 default n
518 help
519 A special purpose allocator for storing compressed pages.
520 It is designed to store up to two compressed pages per physical
521 page. While this design limits storage density, it has simple and
522 deterministic reclaim properties that make it preferable to a higher
523 density approach when reclaim will be used.
524
525config ZSWAP
526 bool "Compressed cache for swap pages (EXPERIMENTAL)"
527 depends on FRONTSWAP && CRYPTO=y
528 select CRYPTO_LZO
529 select ZBUD
530 default n
531 help
532 A lightweight compressed cache for swap pages. It takes
533 pages that are in the process of being swapped out and attempts to
534 compress them into a dynamically allocated RAM-based memory pool.
535 This can result in a significant I/O reduction on swap device and,
536 in the case where decompressing from RAM is faster that swap device
537 reads, can also improve workload performance.
538
539 This is marked experimental because it is a new feature (as of
540 v3.11) that interacts heavily with memory reclaim. While these
541 interactions don't cause any known issues on simple memory setups,
542 they have not be fully explored on the large set of potential
543 configurations and workloads that exist.
544
545config MEM_SOFT_DIRTY
546 bool "Track memory changes"
547 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
548 select PROC_PAGE_MONITOR
549 help
550 This option enables memory changes tracking by introducing a
551 soft-dirty bit on pte-s. This bit it set when someone writes
552 into a page just as regular dirty bit, but unlike the latter
553 it can be cleared by hands.
554
555 See Documentation/vm/soft-dirty.txt for more details.
556
557config ZSMALLOC
558 bool "Memory allocator for compressed pages"
559 depends on MMU
560 default n
561 help
562 zsmalloc is a slab-based memory allocator designed to store
563 compressed RAM pages. zsmalloc uses virtual memory mapping
564 in order to reduce fragmentation. However, this results in a
565 non-standard allocator interface where a handle, not a pointer, is
566 returned by an alloc(). This handle must be mapped in order to
567 access the allocated space.
568
569config PGTABLE_MAPPING
570 bool "Use page table mapping to access object in zsmalloc"
571 depends on ZSMALLOC
572 help
573 By default, zsmalloc uses a copy-based object mapping method to
574 access allocations that span two pages. However, if a particular
575 architecture (ex, ARM) performs VM mapping faster than copying,
576 then you should select this. This causes zsmalloc to use page table
577 mapping rather than copying for object mapping.
578
579 You can check speed with zsmalloc benchmark:
580 https://github.com/spartacus06/zsmapbench
581
582config GENERIC_EARLY_IOREMAP
583 bool
584
585config MAX_STACK_SIZE_MB
586 int "Maximum user stack size for 32-bit processes (MB)"
587 default 80
588 range 8 256 if METAG
589 range 8 2048
590 depends on STACK_GROWSUP && (!64BIT || COMPAT)
591 help
592 This is the maximum stack size in Megabytes in the VM layout of 32-bit
593 user processes when the stack grows upwards (currently only on parisc
594 and metag arch). The stack will be located at the highest memory
595 address minus the given value, unless the RLIMIT_STACK hard limit is
596 changed to a smaller value in which case that is used.
597
598 A sane initial value is 80 MB.