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1# SPDX-License-Identifier: GPL-2.0-only
2
3menu "Memory Management options"
4
5#
6# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
7# add proper SWAP support to them, in which case this can be remove.
8#
9config ARCH_NO_SWAP
10 bool
11
12config ZPOOL
13 bool
14
15menuconfig SWAP
16 bool "Support for paging of anonymous memory (swap)"
17 depends on MMU && BLOCK && !ARCH_NO_SWAP
18 default y
19 help
20 This option allows you to choose whether you want to have support
21 for so called swap devices or swap files in your kernel that are
22 used to provide more virtual memory than the actual RAM present
23 in your computer. If unsure say Y.
24
25config ZSWAP
26 bool "Compressed cache for swap pages"
27 depends on SWAP
28 select CRYPTO
29 select ZPOOL
30 help
31 A lightweight compressed cache for swap pages. It takes
32 pages that are in the process of being swapped out and attempts to
33 compress them into a dynamically allocated RAM-based memory pool.
34 This can result in a significant I/O reduction on swap device and,
35 in the case where decompressing from RAM is faster than swap device
36 reads, can also improve workload performance.
37
38config ZSWAP_DEFAULT_ON
39 bool "Enable the compressed cache for swap pages by default"
40 depends on ZSWAP
41 help
42 If selected, the compressed cache for swap pages will be enabled
43 at boot, otherwise it will be disabled.
44
45 The selection made here can be overridden by using the kernel
46 command line 'zswap.enabled=' option.
47
48config ZSWAP_EXCLUSIVE_LOADS_DEFAULT_ON
49 bool "Invalidate zswap entries when pages are loaded"
50 depends on ZSWAP
51 help
52 If selected, exclusive loads for zswap will be enabled at boot,
53 otherwise it will be disabled.
54
55 If exclusive loads are enabled, when a page is loaded from zswap,
56 the zswap entry is invalidated at once, as opposed to leaving it
57 in zswap until the swap entry is freed.
58
59 This avoids having two copies of the same page in memory
60 (compressed and uncompressed) after faulting in a page from zswap.
61 The cost is that if the page was never dirtied and needs to be
62 swapped out again, it will be re-compressed.
63
64config ZSWAP_SHRINKER_DEFAULT_ON
65 bool "Shrink the zswap pool on memory pressure"
66 depends on ZSWAP
67 default n
68 help
69 If selected, the zswap shrinker will be enabled, and the pages
70 stored in the zswap pool will become available for reclaim (i.e
71 written back to the backing swap device) on memory pressure.
72
73 This means that zswap writeback could happen even if the pool is
74 not yet full, or the cgroup zswap limit has not been reached,
75 reducing the chance that cold pages will reside in the zswap pool
76 and consume memory indefinitely.
77
78choice
79 prompt "Default compressor"
80 depends on ZSWAP
81 default ZSWAP_COMPRESSOR_DEFAULT_LZO
82 help
83 Selects the default compression algorithm for the compressed cache
84 for swap pages.
85
86 For an overview what kind of performance can be expected from
87 a particular compression algorithm please refer to the benchmarks
88 available at the following LWN page:
89 https://lwn.net/Articles/751795/
90
91 If in doubt, select 'LZO'.
92
93 The selection made here can be overridden by using the kernel
94 command line 'zswap.compressor=' option.
95
96config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
97 bool "Deflate"
98 select CRYPTO_DEFLATE
99 help
100 Use the Deflate algorithm as the default compression algorithm.
101
102config ZSWAP_COMPRESSOR_DEFAULT_LZO
103 bool "LZO"
104 select CRYPTO_LZO
105 help
106 Use the LZO algorithm as the default compression algorithm.
107
108config ZSWAP_COMPRESSOR_DEFAULT_842
109 bool "842"
110 select CRYPTO_842
111 help
112 Use the 842 algorithm as the default compression algorithm.
113
114config ZSWAP_COMPRESSOR_DEFAULT_LZ4
115 bool "LZ4"
116 select CRYPTO_LZ4
117 help
118 Use the LZ4 algorithm as the default compression algorithm.
119
120config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
121 bool "LZ4HC"
122 select CRYPTO_LZ4HC
123 help
124 Use the LZ4HC algorithm as the default compression algorithm.
125
126config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
127 bool "zstd"
128 select CRYPTO_ZSTD
129 help
130 Use the zstd algorithm as the default compression algorithm.
131endchoice
132
133config ZSWAP_COMPRESSOR_DEFAULT
134 string
135 depends on ZSWAP
136 default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
137 default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
138 default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
139 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
140 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
141 default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
142 default ""
143
144choice
145 prompt "Default allocator"
146 depends on ZSWAP
147 default ZSWAP_ZPOOL_DEFAULT_ZSMALLOC if MMU
148 default ZSWAP_ZPOOL_DEFAULT_ZBUD
149 help
150 Selects the default allocator for the compressed cache for
151 swap pages.
152 The default is 'zbud' for compatibility, however please do
153 read the description of each of the allocators below before
154 making a right choice.
155
156 The selection made here can be overridden by using the kernel
157 command line 'zswap.zpool=' option.
158
159config ZSWAP_ZPOOL_DEFAULT_ZBUD
160 bool "zbud"
161 select ZBUD
162 help
163 Use the zbud allocator as the default allocator.
164
165config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
166 bool "z3fold"
167 select Z3FOLD
168 help
169 Use the z3fold allocator as the default allocator.
170
171config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
172 bool "zsmalloc"
173 select ZSMALLOC
174 help
175 Use the zsmalloc allocator as the default allocator.
176endchoice
177
178config ZSWAP_ZPOOL_DEFAULT
179 string
180 depends on ZSWAP
181 default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
182 default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
183 default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
184 default ""
185
186config ZBUD
187 tristate "2:1 compression allocator (zbud)"
188 depends on ZSWAP
189 help
190 A special purpose allocator for storing compressed pages.
191 It is designed to store up to two compressed pages per physical
192 page. While this design limits storage density, it has simple and
193 deterministic reclaim properties that make it preferable to a higher
194 density approach when reclaim will be used.
195
196config Z3FOLD
197 tristate "3:1 compression allocator (z3fold)"
198 depends on ZSWAP
199 help
200 A special purpose allocator for storing compressed pages.
201 It is designed to store up to three compressed pages per physical
202 page. It is a ZBUD derivative so the simplicity and determinism are
203 still there.
204
205config ZSMALLOC
206 tristate
207 prompt "N:1 compression allocator (zsmalloc)" if ZSWAP
208 depends on MMU
209 help
210 zsmalloc is a slab-based memory allocator designed to store
211 pages of various compression levels efficiently. It achieves
212 the highest storage density with the least amount of fragmentation.
213
214config ZSMALLOC_STAT
215 bool "Export zsmalloc statistics"
216 depends on ZSMALLOC
217 select DEBUG_FS
218 help
219 This option enables code in the zsmalloc to collect various
220 statistics about what's happening in zsmalloc and exports that
221 information to userspace via debugfs.
222 If unsure, say N.
223
224config ZSMALLOC_CHAIN_SIZE
225 int "Maximum number of physical pages per-zspage"
226 default 8
227 range 4 16
228 depends on ZSMALLOC
229 help
230 This option sets the upper limit on the number of physical pages
231 that a zmalloc page (zspage) can consist of. The optimal zspage
232 chain size is calculated for each size class during the
233 initialization of the pool.
234
235 Changing this option can alter the characteristics of size classes,
236 such as the number of pages per zspage and the number of objects
237 per zspage. This can also result in different configurations of
238 the pool, as zsmalloc merges size classes with similar
239 characteristics.
240
241 For more information, see zsmalloc documentation.
242
243menu "Slab allocator options"
244
245config SLUB
246 def_bool y
247
248config SLUB_TINY
249 bool "Configure for minimal memory footprint"
250 depends on EXPERT
251 select SLAB_MERGE_DEFAULT
252 help
253 Configures the slab allocator in a way to achieve minimal memory
254 footprint, sacrificing scalability, debugging and other features.
255 This is intended only for the smallest system that had used the
256 SLOB allocator and is not recommended for systems with more than
257 16MB RAM.
258
259 If unsure, say N.
260
261config SLAB_MERGE_DEFAULT
262 bool "Allow slab caches to be merged"
263 default y
264 help
265 For reduced kernel memory fragmentation, slab caches can be
266 merged when they share the same size and other characteristics.
267 This carries a risk of kernel heap overflows being able to
268 overwrite objects from merged caches (and more easily control
269 cache layout), which makes such heap attacks easier to exploit
270 by attackers. By keeping caches unmerged, these kinds of exploits
271 can usually only damage objects in the same cache. To disable
272 merging at runtime, "slab_nomerge" can be passed on the kernel
273 command line.
274
275config SLAB_FREELIST_RANDOM
276 bool "Randomize slab freelist"
277 depends on !SLUB_TINY
278 help
279 Randomizes the freelist order used on creating new pages. This
280 security feature reduces the predictability of the kernel slab
281 allocator against heap overflows.
282
283config SLAB_FREELIST_HARDENED
284 bool "Harden slab freelist metadata"
285 depends on !SLUB_TINY
286 help
287 Many kernel heap attacks try to target slab cache metadata and
288 other infrastructure. This options makes minor performance
289 sacrifices to harden the kernel slab allocator against common
290 freelist exploit methods.
291
292config SLUB_STATS
293 default n
294 bool "Enable performance statistics"
295 depends on SYSFS && !SLUB_TINY
296 help
297 The statistics are useful to debug slab allocation behavior in
298 order find ways to optimize the allocator. This should never be
299 enabled for production use since keeping statistics slows down
300 the allocator by a few percentage points. The slabinfo command
301 supports the determination of the most active slabs to figure
302 out which slabs are relevant to a particular load.
303 Try running: slabinfo -DA
304
305config SLUB_CPU_PARTIAL
306 default y
307 depends on SMP && !SLUB_TINY
308 bool "Enable per cpu partial caches"
309 help
310 Per cpu partial caches accelerate objects allocation and freeing
311 that is local to a processor at the price of more indeterminism
312 in the latency of the free. On overflow these caches will be cleared
313 which requires the taking of locks that may cause latency spikes.
314 Typically one would choose no for a realtime system.
315
316config RANDOM_KMALLOC_CACHES
317 default n
318 depends on !SLUB_TINY
319 bool "Randomize slab caches for normal kmalloc"
320 help
321 A hardening feature that creates multiple copies of slab caches for
322 normal kmalloc allocation and makes kmalloc randomly pick one based
323 on code address, which makes the attackers more difficult to spray
324 vulnerable memory objects on the heap for the purpose of exploiting
325 memory vulnerabilities.
326
327 Currently the number of copies is set to 16, a reasonably large value
328 that effectively diverges the memory objects allocated for different
329 subsystems or modules into different caches, at the expense of a
330 limited degree of memory and CPU overhead that relates to hardware and
331 system workload.
332
333endmenu # Slab allocator options
334
335config SHUFFLE_PAGE_ALLOCATOR
336 bool "Page allocator randomization"
337 default SLAB_FREELIST_RANDOM && ACPI_NUMA
338 help
339 Randomization of the page allocator improves the average
340 utilization of a direct-mapped memory-side-cache. See section
341 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
342 6.2a specification for an example of how a platform advertises
343 the presence of a memory-side-cache. There are also incidental
344 security benefits as it reduces the predictability of page
345 allocations to compliment SLAB_FREELIST_RANDOM, but the
346 default granularity of shuffling on the MAX_PAGE_ORDER i.e, 10th
347 order of pages is selected based on cache utilization benefits
348 on x86.
349
350 While the randomization improves cache utilization it may
351 negatively impact workloads on platforms without a cache. For
352 this reason, by default, the randomization is enabled only
353 after runtime detection of a direct-mapped memory-side-cache.
354 Otherwise, the randomization may be force enabled with the
355 'page_alloc.shuffle' kernel command line parameter.
356
357 Say Y if unsure.
358
359config COMPAT_BRK
360 bool "Disable heap randomization"
361 default y
362 help
363 Randomizing heap placement makes heap exploits harder, but it
364 also breaks ancient binaries (including anything libc5 based).
365 This option changes the bootup default to heap randomization
366 disabled, and can be overridden at runtime by setting
367 /proc/sys/kernel/randomize_va_space to 2.
368
369 On non-ancient distros (post-2000 ones) N is usually a safe choice.
370
371config MMAP_ALLOW_UNINITIALIZED
372 bool "Allow mmapped anonymous memory to be uninitialized"
373 depends on EXPERT && !MMU
374 default n
375 help
376 Normally, and according to the Linux spec, anonymous memory obtained
377 from mmap() has its contents cleared before it is passed to
378 userspace. Enabling this config option allows you to request that
379 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
380 providing a huge performance boost. If this option is not enabled,
381 then the flag will be ignored.
382
383 This is taken advantage of by uClibc's malloc(), and also by
384 ELF-FDPIC binfmt's brk and stack allocator.
385
386 Because of the obvious security issues, this option should only be
387 enabled on embedded devices where you control what is run in
388 userspace. Since that isn't generally a problem on no-MMU systems,
389 it is normally safe to say Y here.
390
391 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
392
393config SELECT_MEMORY_MODEL
394 def_bool y
395 depends on ARCH_SELECT_MEMORY_MODEL
396
397choice
398 prompt "Memory model"
399 depends on SELECT_MEMORY_MODEL
400 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
401 default FLATMEM_MANUAL
402 help
403 This option allows you to change some of the ways that
404 Linux manages its memory internally. Most users will
405 only have one option here selected by the architecture
406 configuration. This is normal.
407
408config FLATMEM_MANUAL
409 bool "Flat Memory"
410 depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE
411 help
412 This option is best suited for non-NUMA systems with
413 flat address space. The FLATMEM is the most efficient
414 system in terms of performance and resource consumption
415 and it is the best option for smaller systems.
416
417 For systems that have holes in their physical address
418 spaces and for features like NUMA and memory hotplug,
419 choose "Sparse Memory".
420
421 If unsure, choose this option (Flat Memory) over any other.
422
423config SPARSEMEM_MANUAL
424 bool "Sparse Memory"
425 depends on ARCH_SPARSEMEM_ENABLE
426 help
427 This will be the only option for some systems, including
428 memory hot-plug systems. This is normal.
429
430 This option provides efficient support for systems with
431 holes is their physical address space and allows memory
432 hot-plug and hot-remove.
433
434 If unsure, choose "Flat Memory" over this option.
435
436endchoice
437
438config SPARSEMEM
439 def_bool y
440 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
441
442config FLATMEM
443 def_bool y
444 depends on !SPARSEMEM || FLATMEM_MANUAL
445
446#
447# SPARSEMEM_EXTREME (which is the default) does some bootmem
448# allocations when sparse_init() is called. If this cannot
449# be done on your architecture, select this option. However,
450# statically allocating the mem_section[] array can potentially
451# consume vast quantities of .bss, so be careful.
452#
453# This option will also potentially produce smaller runtime code
454# with gcc 3.4 and later.
455#
456config SPARSEMEM_STATIC
457 bool
458
459#
460# Architecture platforms which require a two level mem_section in SPARSEMEM
461# must select this option. This is usually for architecture platforms with
462# an extremely sparse physical address space.
463#
464config SPARSEMEM_EXTREME
465 def_bool y
466 depends on SPARSEMEM && !SPARSEMEM_STATIC
467
468config SPARSEMEM_VMEMMAP_ENABLE
469 bool
470
471config SPARSEMEM_VMEMMAP
472 bool "Sparse Memory virtual memmap"
473 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
474 default y
475 help
476 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
477 pfn_to_page and page_to_pfn operations. This is the most
478 efficient option when sufficient kernel resources are available.
479#
480# Select this config option from the architecture Kconfig, if it is preferred
481# to enable the feature of HugeTLB/dev_dax vmemmap optimization.
482#
483config ARCH_WANT_OPTIMIZE_DAX_VMEMMAP
484 bool
485
486config ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP
487 bool
488
489config HAVE_MEMBLOCK_PHYS_MAP
490 bool
491
492config HAVE_FAST_GUP
493 depends on MMU
494 bool
495
496# Don't discard allocated memory used to track "memory" and "reserved" memblocks
497# after early boot, so it can still be used to test for validity of memory.
498# Also, memblocks are updated with memory hot(un)plug.
499config ARCH_KEEP_MEMBLOCK
500 bool
501
502# Keep arch NUMA mapping infrastructure post-init.
503config NUMA_KEEP_MEMINFO
504 bool
505
506config MEMORY_ISOLATION
507 bool
508
509# IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked
510# IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via
511# /dev/mem.
512config EXCLUSIVE_SYSTEM_RAM
513 def_bool y
514 depends on !DEVMEM || STRICT_DEVMEM
515
516#
517# Only be set on architectures that have completely implemented memory hotplug
518# feature. If you are not sure, don't touch it.
519#
520config HAVE_BOOTMEM_INFO_NODE
521 def_bool n
522
523config ARCH_ENABLE_MEMORY_HOTPLUG
524 bool
525
526config ARCH_ENABLE_MEMORY_HOTREMOVE
527 bool
528
529# eventually, we can have this option just 'select SPARSEMEM'
530menuconfig MEMORY_HOTPLUG
531 bool "Memory hotplug"
532 select MEMORY_ISOLATION
533 depends on SPARSEMEM
534 depends on ARCH_ENABLE_MEMORY_HOTPLUG
535 depends on 64BIT
536 select NUMA_KEEP_MEMINFO if NUMA
537
538if MEMORY_HOTPLUG
539
540config MEMORY_HOTPLUG_DEFAULT_ONLINE
541 bool "Online the newly added memory blocks by default"
542 depends on MEMORY_HOTPLUG
543 help
544 This option sets the default policy setting for memory hotplug
545 onlining policy (/sys/devices/system/memory/auto_online_blocks) which
546 determines what happens to newly added memory regions. Policy setting
547 can always be changed at runtime.
548 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
549
550 Say Y here if you want all hot-plugged memory blocks to appear in
551 'online' state by default.
552 Say N here if you want the default policy to keep all hot-plugged
553 memory blocks in 'offline' state.
554
555config MEMORY_HOTREMOVE
556 bool "Allow for memory hot remove"
557 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
558 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
559 depends on MIGRATION
560
561config MHP_MEMMAP_ON_MEMORY
562 def_bool y
563 depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
564 depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
565
566endif # MEMORY_HOTPLUG
567
568config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
569 bool
570
571# Heavily threaded applications may benefit from splitting the mm-wide
572# page_table_lock, so that faults on different parts of the user address
573# space can be handled with less contention: split it at this NR_CPUS.
574# Default to 4 for wider testing, though 8 might be more appropriate.
575# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
576# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
577# SPARC32 allocates multiple pte tables within a single page, and therefore
578# a per-page lock leads to problems when multiple tables need to be locked
579# at the same time (e.g. copy_page_range()).
580# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
581#
582config SPLIT_PTLOCK_CPUS
583 int
584 default "999999" if !MMU
585 default "999999" if ARM && !CPU_CACHE_VIPT
586 default "999999" if PARISC && !PA20
587 default "999999" if SPARC32
588 default "4"
589
590config ARCH_ENABLE_SPLIT_PMD_PTLOCK
591 bool
592
593#
594# support for memory balloon
595config MEMORY_BALLOON
596 bool
597
598#
599# support for memory balloon compaction
600config BALLOON_COMPACTION
601 bool "Allow for balloon memory compaction/migration"
602 def_bool y
603 depends on COMPACTION && MEMORY_BALLOON
604 help
605 Memory fragmentation introduced by ballooning might reduce
606 significantly the number of 2MB contiguous memory blocks that can be
607 used within a guest, thus imposing performance penalties associated
608 with the reduced number of transparent huge pages that could be used
609 by the guest workload. Allowing the compaction & migration for memory
610 pages enlisted as being part of memory balloon devices avoids the
611 scenario aforementioned and helps improving memory defragmentation.
612
613#
614# support for memory compaction
615config COMPACTION
616 bool "Allow for memory compaction"
617 def_bool y
618 select MIGRATION
619 depends on MMU
620 help
621 Compaction is the only memory management component to form
622 high order (larger physically contiguous) memory blocks
623 reliably. The page allocator relies on compaction heavily and
624 the lack of the feature can lead to unexpected OOM killer
625 invocations for high order memory requests. You shouldn't
626 disable this option unless there really is a strong reason for
627 it and then we would be really interested to hear about that at
628 linux-mm@kvack.org.
629
630config COMPACT_UNEVICTABLE_DEFAULT
631 int
632 depends on COMPACTION
633 default 0 if PREEMPT_RT
634 default 1
635
636#
637# support for free page reporting
638config PAGE_REPORTING
639 bool "Free page reporting"
640 def_bool n
641 help
642 Free page reporting allows for the incremental acquisition of
643 free pages from the buddy allocator for the purpose of reporting
644 those pages to another entity, such as a hypervisor, so that the
645 memory can be freed within the host for other uses.
646
647#
648# support for page migration
649#
650config MIGRATION
651 bool "Page migration"
652 def_bool y
653 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
654 help
655 Allows the migration of the physical location of pages of processes
656 while the virtual addresses are not changed. This is useful in
657 two situations. The first is on NUMA systems to put pages nearer
658 to the processors accessing. The second is when allocating huge
659 pages as migration can relocate pages to satisfy a huge page
660 allocation instead of reclaiming.
661
662config DEVICE_MIGRATION
663 def_bool MIGRATION && ZONE_DEVICE
664
665config ARCH_ENABLE_HUGEPAGE_MIGRATION
666 bool
667
668config ARCH_ENABLE_THP_MIGRATION
669 bool
670
671config HUGETLB_PAGE_SIZE_VARIABLE
672 def_bool n
673 help
674 Allows the pageblock_order value to be dynamic instead of just standard
675 HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available
676 on a platform.
677
678 Note that the pageblock_order cannot exceed MAX_PAGE_ORDER and will be
679 clamped down to MAX_PAGE_ORDER.
680
681config CONTIG_ALLOC
682 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
683
684config PCP_BATCH_SCALE_MAX
685 int "Maximum scale factor of PCP (Per-CPU pageset) batch allocate/free"
686 default 5
687 range 0 6
688 help
689 In page allocator, PCP (Per-CPU pageset) is refilled and drained in
690 batches. The batch number is scaled automatically to improve page
691 allocation/free throughput. But too large scale factor may hurt
692 latency. This option sets the upper limit of scale factor to limit
693 the maximum latency.
694
695config PHYS_ADDR_T_64BIT
696 def_bool 64BIT
697
698config BOUNCE
699 bool "Enable bounce buffers"
700 default y
701 depends on BLOCK && MMU && HIGHMEM
702 help
703 Enable bounce buffers for devices that cannot access the full range of
704 memory available to the CPU. Enabled by default when HIGHMEM is
705 selected, but you may say n to override this.
706
707config MMU_NOTIFIER
708 bool
709 select INTERVAL_TREE
710
711config KSM
712 bool "Enable KSM for page merging"
713 depends on MMU
714 select XXHASH
715 help
716 Enable Kernel Samepage Merging: KSM periodically scans those areas
717 of an application's address space that an app has advised may be
718 mergeable. When it finds pages of identical content, it replaces
719 the many instances by a single page with that content, so
720 saving memory until one or another app needs to modify the content.
721 Recommended for use with KVM, or with other duplicative applications.
722 See Documentation/mm/ksm.rst for more information: KSM is inactive
723 until a program has madvised that an area is MADV_MERGEABLE, and
724 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
725
726config DEFAULT_MMAP_MIN_ADDR
727 int "Low address space to protect from user allocation"
728 depends on MMU
729 default 4096
730 help
731 This is the portion of low virtual memory which should be protected
732 from userspace allocation. Keeping a user from writing to low pages
733 can help reduce the impact of kernel NULL pointer bugs.
734
735 For most ppc64 and x86 users with lots of address space
736 a value of 65536 is reasonable and should cause no problems.
737 On arm and other archs it should not be higher than 32768.
738 Programs which use vm86 functionality or have some need to map
739 this low address space will need CAP_SYS_RAWIO or disable this
740 protection by setting the value to 0.
741
742 This value can be changed after boot using the
743 /proc/sys/vm/mmap_min_addr tunable.
744
745config ARCH_SUPPORTS_MEMORY_FAILURE
746 bool
747
748config MEMORY_FAILURE
749 depends on MMU
750 depends on ARCH_SUPPORTS_MEMORY_FAILURE
751 bool "Enable recovery from hardware memory errors"
752 select MEMORY_ISOLATION
753 select RAS
754 help
755 Enables code to recover from some memory failures on systems
756 with MCA recovery. This allows a system to continue running
757 even when some of its memory has uncorrected errors. This requires
758 special hardware support and typically ECC memory.
759
760config HWPOISON_INJECT
761 tristate "HWPoison pages injector"
762 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
763 select PROC_PAGE_MONITOR
764
765config NOMMU_INITIAL_TRIM_EXCESS
766 int "Turn on mmap() excess space trimming before booting"
767 depends on !MMU
768 default 1
769 help
770 The NOMMU mmap() frequently needs to allocate large contiguous chunks
771 of memory on which to store mappings, but it can only ask the system
772 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
773 more than it requires. To deal with this, mmap() is able to trim off
774 the excess and return it to the allocator.
775
776 If trimming is enabled, the excess is trimmed off and returned to the
777 system allocator, which can cause extra fragmentation, particularly
778 if there are a lot of transient processes.
779
780 If trimming is disabled, the excess is kept, but not used, which for
781 long-term mappings means that the space is wasted.
782
783 Trimming can be dynamically controlled through a sysctl option
784 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
785 excess pages there must be before trimming should occur, or zero if
786 no trimming is to occur.
787
788 This option specifies the initial value of this option. The default
789 of 1 says that all excess pages should be trimmed.
790
791 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
792
793config ARCH_WANT_GENERAL_HUGETLB
794 bool
795
796config ARCH_WANTS_THP_SWAP
797 def_bool n
798
799menuconfig TRANSPARENT_HUGEPAGE
800 bool "Transparent Hugepage Support"
801 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT
802 select COMPACTION
803 select XARRAY_MULTI
804 help
805 Transparent Hugepages allows the kernel to use huge pages and
806 huge tlb transparently to the applications whenever possible.
807 This feature can improve computing performance to certain
808 applications by speeding up page faults during memory
809 allocation, by reducing the number of tlb misses and by speeding
810 up the pagetable walking.
811
812 If memory constrained on embedded, you may want to say N.
813
814if TRANSPARENT_HUGEPAGE
815
816choice
817 prompt "Transparent Hugepage Support sysfs defaults"
818 depends on TRANSPARENT_HUGEPAGE
819 default TRANSPARENT_HUGEPAGE_ALWAYS
820 help
821 Selects the sysfs defaults for Transparent Hugepage Support.
822
823 config TRANSPARENT_HUGEPAGE_ALWAYS
824 bool "always"
825 help
826 Enabling Transparent Hugepage always, can increase the
827 memory footprint of applications without a guaranteed
828 benefit but it will work automatically for all applications.
829
830 config TRANSPARENT_HUGEPAGE_MADVISE
831 bool "madvise"
832 help
833 Enabling Transparent Hugepage madvise, will only provide a
834 performance improvement benefit to the applications using
835 madvise(MADV_HUGEPAGE) but it won't risk to increase the
836 memory footprint of applications without a guaranteed
837 benefit.
838
839 config TRANSPARENT_HUGEPAGE_NEVER
840 bool "never"
841 help
842 Disable Transparent Hugepage by default. It can still be
843 enabled at runtime via sysfs.
844endchoice
845
846config THP_SWAP
847 def_bool y
848 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT
849 help
850 Swap transparent huge pages in one piece, without splitting.
851 XXX: For now, swap cluster backing transparent huge page
852 will be split after swapout.
853
854 For selection by architectures with reasonable THP sizes.
855
856config READ_ONLY_THP_FOR_FS
857 bool "Read-only THP for filesystems (EXPERIMENTAL)"
858 depends on TRANSPARENT_HUGEPAGE && SHMEM
859
860 help
861 Allow khugepaged to put read-only file-backed pages in THP.
862
863 This is marked experimental because it is a new feature. Write
864 support of file THPs will be developed in the next few release
865 cycles.
866
867endif # TRANSPARENT_HUGEPAGE
868
869#
870# UP and nommu archs use km based percpu allocator
871#
872config NEED_PER_CPU_KM
873 depends on !SMP || !MMU
874 bool
875 default y
876
877config NEED_PER_CPU_EMBED_FIRST_CHUNK
878 bool
879
880config NEED_PER_CPU_PAGE_FIRST_CHUNK
881 bool
882
883config USE_PERCPU_NUMA_NODE_ID
884 bool
885
886config HAVE_SETUP_PER_CPU_AREA
887 bool
888
889config CMA
890 bool "Contiguous Memory Allocator"
891 depends on MMU
892 select MIGRATION
893 select MEMORY_ISOLATION
894 help
895 This enables the Contiguous Memory Allocator which allows other
896 subsystems to allocate big physically-contiguous blocks of memory.
897 CMA reserves a region of memory and allows only movable pages to
898 be allocated from it. This way, the kernel can use the memory for
899 pagecache and when a subsystem requests for contiguous area, the
900 allocated pages are migrated away to serve the contiguous request.
901
902 If unsure, say "n".
903
904config CMA_DEBUG
905 bool "CMA debug messages (DEVELOPMENT)"
906 depends on DEBUG_KERNEL && CMA
907 help
908 Turns on debug messages in CMA. This produces KERN_DEBUG
909 messages for every CMA call as well as various messages while
910 processing calls such as dma_alloc_from_contiguous().
911 This option does not affect warning and error messages.
912
913config CMA_DEBUGFS
914 bool "CMA debugfs interface"
915 depends on CMA && DEBUG_FS
916 help
917 Turns on the DebugFS interface for CMA.
918
919config CMA_SYSFS
920 bool "CMA information through sysfs interface"
921 depends on CMA && SYSFS
922 help
923 This option exposes some sysfs attributes to get information
924 from CMA.
925
926config CMA_AREAS
927 int "Maximum count of the CMA areas"
928 depends on CMA
929 default 19 if NUMA
930 default 7
931 help
932 CMA allows to create CMA areas for particular purpose, mainly,
933 used as device private area. This parameter sets the maximum
934 number of CMA area in the system.
935
936 If unsure, leave the default value "7" in UMA and "19" in NUMA.
937
938config MEM_SOFT_DIRTY
939 bool "Track memory changes"
940 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
941 select PROC_PAGE_MONITOR
942 help
943 This option enables memory changes tracking by introducing a
944 soft-dirty bit on pte-s. This bit it set when someone writes
945 into a page just as regular dirty bit, but unlike the latter
946 it can be cleared by hands.
947
948 See Documentation/admin-guide/mm/soft-dirty.rst for more details.
949
950config GENERIC_EARLY_IOREMAP
951 bool
952
953config STACK_MAX_DEFAULT_SIZE_MB
954 int "Default maximum user stack size for 32-bit processes (MB)"
955 default 100
956 range 8 2048
957 depends on STACK_GROWSUP && (!64BIT || COMPAT)
958 help
959 This is the maximum stack size in Megabytes in the VM layout of 32-bit
960 user processes when the stack grows upwards (currently only on parisc
961 arch) when the RLIMIT_STACK hard limit is unlimited.
962
963 A sane initial value is 100 MB.
964
965config DEFERRED_STRUCT_PAGE_INIT
966 bool "Defer initialisation of struct pages to kthreads"
967 depends on SPARSEMEM
968 depends on !NEED_PER_CPU_KM
969 depends on 64BIT
970 select PADATA
971 help
972 Ordinarily all struct pages are initialised during early boot in a
973 single thread. On very large machines this can take a considerable
974 amount of time. If this option is set, large machines will bring up
975 a subset of memmap at boot and then initialise the rest in parallel.
976 This has a potential performance impact on tasks running early in the
977 lifetime of the system until these kthreads finish the
978 initialisation.
979
980config PAGE_IDLE_FLAG
981 bool
982 select PAGE_EXTENSION if !64BIT
983 help
984 This adds PG_idle and PG_young flags to 'struct page'. PTE Accessed
985 bit writers can set the state of the bit in the flags so that PTE
986 Accessed bit readers may avoid disturbance.
987
988config IDLE_PAGE_TRACKING
989 bool "Enable idle page tracking"
990 depends on SYSFS && MMU
991 select PAGE_IDLE_FLAG
992 help
993 This feature allows to estimate the amount of user pages that have
994 not been touched during a given period of time. This information can
995 be useful to tune memory cgroup limits and/or for job placement
996 within a compute cluster.
997
998 See Documentation/admin-guide/mm/idle_page_tracking.rst for
999 more details.
1000
1001config ARCH_HAS_CACHE_LINE_SIZE
1002 bool
1003
1004config ARCH_HAS_CURRENT_STACK_POINTER
1005 bool
1006 help
1007 In support of HARDENED_USERCOPY performing stack variable lifetime
1008 checking, an architecture-agnostic way to find the stack pointer
1009 is needed. Once an architecture defines an unsigned long global
1010 register alias named "current_stack_pointer", this config can be
1011 selected.
1012
1013config ARCH_HAS_PTE_DEVMAP
1014 bool
1015
1016config ARCH_HAS_ZONE_DMA_SET
1017 bool
1018
1019config ZONE_DMA
1020 bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET
1021 default y if ARM64 || X86
1022
1023config ZONE_DMA32
1024 bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET
1025 depends on !X86_32
1026 default y if ARM64
1027
1028config ZONE_DEVICE
1029 bool "Device memory (pmem, HMM, etc...) hotplug support"
1030 depends on MEMORY_HOTPLUG
1031 depends on MEMORY_HOTREMOVE
1032 depends on SPARSEMEM_VMEMMAP
1033 depends on ARCH_HAS_PTE_DEVMAP
1034 select XARRAY_MULTI
1035
1036 help
1037 Device memory hotplug support allows for establishing pmem,
1038 or other device driver discovered memory regions, in the
1039 memmap. This allows pfn_to_page() lookups of otherwise
1040 "device-physical" addresses which is needed for using a DAX
1041 mapping in an O_DIRECT operation, among other things.
1042
1043 If FS_DAX is enabled, then say Y.
1044
1045#
1046# Helpers to mirror range of the CPU page tables of a process into device page
1047# tables.
1048#
1049config HMM_MIRROR
1050 bool
1051 depends on MMU
1052
1053config GET_FREE_REGION
1054 depends on SPARSEMEM
1055 bool
1056
1057config DEVICE_PRIVATE
1058 bool "Unaddressable device memory (GPU memory, ...)"
1059 depends on ZONE_DEVICE
1060 select GET_FREE_REGION
1061
1062 help
1063 Allows creation of struct pages to represent unaddressable device
1064 memory; i.e., memory that is only accessible from the device (or
1065 group of devices). You likely also want to select HMM_MIRROR.
1066
1067config VMAP_PFN
1068 bool
1069
1070config ARCH_USES_HIGH_VMA_FLAGS
1071 bool
1072config ARCH_HAS_PKEYS
1073 bool
1074
1075config ARCH_USES_PG_ARCH_X
1076 bool
1077 help
1078 Enable the definition of PG_arch_x page flags with x > 1. Only
1079 suitable for 64-bit architectures with CONFIG_FLATMEM or
1080 CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be
1081 enough room for additional bits in page->flags.
1082
1083config VM_EVENT_COUNTERS
1084 default y
1085 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1086 help
1087 VM event counters are needed for event counts to be shown.
1088 This option allows the disabling of the VM event counters
1089 on EXPERT systems. /proc/vmstat will only show page counts
1090 if VM event counters are disabled.
1091
1092config PERCPU_STATS
1093 bool "Collect percpu memory statistics"
1094 help
1095 This feature collects and exposes statistics via debugfs. The
1096 information includes global and per chunk statistics, which can
1097 be used to help understand percpu memory usage.
1098
1099config GUP_TEST
1100 bool "Enable infrastructure for get_user_pages()-related unit tests"
1101 depends on DEBUG_FS
1102 help
1103 Provides /sys/kernel/debug/gup_test, which in turn provides a way
1104 to make ioctl calls that can launch kernel-based unit tests for
1105 the get_user_pages*() and pin_user_pages*() family of API calls.
1106
1107 These tests include benchmark testing of the _fast variants of
1108 get_user_pages*() and pin_user_pages*(), as well as smoke tests of
1109 the non-_fast variants.
1110
1111 There is also a sub-test that allows running dump_page() on any
1112 of up to eight pages (selected by command line args) within the
1113 range of user-space addresses. These pages are either pinned via
1114 pin_user_pages*(), or pinned via get_user_pages*(), as specified
1115 by other command line arguments.
1116
1117 See tools/testing/selftests/mm/gup_test.c
1118
1119comment "GUP_TEST needs to have DEBUG_FS enabled"
1120 depends on !GUP_TEST && !DEBUG_FS
1121
1122config GUP_GET_PXX_LOW_HIGH
1123 bool
1124
1125config DMAPOOL_TEST
1126 tristate "Enable a module to run time tests on dma_pool"
1127 depends on HAS_DMA
1128 help
1129 Provides a test module that will allocate and free many blocks of
1130 various sizes and report how long it takes. This is intended to
1131 provide a consistent way to measure how changes to the
1132 dma_pool_alloc/free routines affect performance.
1133
1134config ARCH_HAS_PTE_SPECIAL
1135 bool
1136
1137#
1138# Some architectures require a special hugepage directory format that is
1139# required to support multiple hugepage sizes. For example a4fe3ce76
1140# "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
1141# introduced it on powerpc. This allows for a more flexible hugepage
1142# pagetable layouts.
1143#
1144config ARCH_HAS_HUGEPD
1145 bool
1146
1147config MAPPING_DIRTY_HELPERS
1148 bool
1149
1150config KMAP_LOCAL
1151 bool
1152
1153config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY
1154 bool
1155
1156# struct io_mapping based helper. Selected by drivers that need them
1157config IO_MAPPING
1158 bool
1159
1160config MEMFD_CREATE
1161 bool "Enable memfd_create() system call" if EXPERT
1162
1163config SECRETMEM
1164 default y
1165 bool "Enable memfd_secret() system call" if EXPERT
1166 depends on ARCH_HAS_SET_DIRECT_MAP
1167 help
1168 Enable the memfd_secret() system call with the ability to create
1169 memory areas visible only in the context of the owning process and
1170 not mapped to other processes and other kernel page tables.
1171
1172config ANON_VMA_NAME
1173 bool "Anonymous VMA name support"
1174 depends on PROC_FS && ADVISE_SYSCALLS && MMU
1175
1176 help
1177 Allow naming anonymous virtual memory areas.
1178
1179 This feature allows assigning names to virtual memory areas. Assigned
1180 names can be later retrieved from /proc/pid/maps and /proc/pid/smaps
1181 and help identifying individual anonymous memory areas.
1182 Assigning a name to anonymous virtual memory area might prevent that
1183 area from being merged with adjacent virtual memory areas due to the
1184 difference in their name.
1185
1186config HAVE_ARCH_USERFAULTFD_WP
1187 bool
1188 help
1189 Arch has userfaultfd write protection support
1190
1191config HAVE_ARCH_USERFAULTFD_MINOR
1192 bool
1193 help
1194 Arch has userfaultfd minor fault support
1195
1196menuconfig USERFAULTFD
1197 bool "Enable userfaultfd() system call"
1198 depends on MMU
1199 help
1200 Enable the userfaultfd() system call that allows to intercept and
1201 handle page faults in userland.
1202
1203if USERFAULTFD
1204config PTE_MARKER_UFFD_WP
1205 bool "Userfaultfd write protection support for shmem/hugetlbfs"
1206 default y
1207 depends on HAVE_ARCH_USERFAULTFD_WP
1208
1209 help
1210 Allows to create marker PTEs for userfaultfd write protection
1211 purposes. It is required to enable userfaultfd write protection on
1212 file-backed memory types like shmem and hugetlbfs.
1213endif # USERFAULTFD
1214
1215# multi-gen LRU {
1216config LRU_GEN
1217 bool "Multi-Gen LRU"
1218 depends on MMU
1219 # make sure folio->flags has enough spare bits
1220 depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP
1221 help
1222 A high performance LRU implementation to overcommit memory. See
1223 Documentation/admin-guide/mm/multigen_lru.rst for details.
1224
1225config LRU_GEN_ENABLED
1226 bool "Enable by default"
1227 depends on LRU_GEN
1228 help
1229 This option enables the multi-gen LRU by default.
1230
1231config LRU_GEN_STATS
1232 bool "Full stats for debugging"
1233 depends on LRU_GEN
1234 help
1235 Do not enable this option unless you plan to look at historical stats
1236 from evicted generations for debugging purpose.
1237
1238 This option has a per-memcg and per-node memory overhead.
1239
1240config LRU_GEN_WALKS_MMU
1241 def_bool y
1242 depends on LRU_GEN && ARCH_HAS_HW_PTE_YOUNG
1243# }
1244
1245config ARCH_SUPPORTS_PER_VMA_LOCK
1246 def_bool n
1247
1248config PER_VMA_LOCK
1249 def_bool y
1250 depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP
1251 help
1252 Allow per-vma locking during page fault handling.
1253
1254 This feature allows locking each virtual memory area separately when
1255 handling page faults instead of taking mmap_lock.
1256
1257config LOCK_MM_AND_FIND_VMA
1258 bool
1259 depends on !STACK_GROWSUP
1260
1261config IOMMU_MM_DATA
1262 bool
1263
1264source "mm/damon/Kconfig"
1265
1266endmenu
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.