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v5.9
  1# SPDX-License-Identifier: GPL-2.0-only
  2
  3menu "Memory Management options"
  4
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  5config SELECT_MEMORY_MODEL
  6	def_bool y
  7	depends on ARCH_SELECT_MEMORY_MODEL
  8
  9choice
 10	prompt "Memory model"
 11	depends on SELECT_MEMORY_MODEL
 12	default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
 13	default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
 14	default FLATMEM_MANUAL
 15	help
 16	  This option allows you to change some of the ways that
 17	  Linux manages its memory internally. Most users will
 18	  only have one option here selected by the architecture
 19	  configuration. This is normal.
 20
 21config FLATMEM_MANUAL
 22	bool "Flat Memory"
 23	depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
 24	help
 25	  This option is best suited for non-NUMA systems with
 26	  flat address space. The FLATMEM is the most efficient
 27	  system in terms of performance and resource consumption
 28	  and it is the best option for smaller systems.
 29
 30	  For systems that have holes in their physical address
 31	  spaces and for features like NUMA and memory hotplug,
 32	  choose "Sparse Memory".
 33
 34	  If unsure, choose this option (Flat Memory) over any other.
 35
 36config DISCONTIGMEM_MANUAL
 37	bool "Discontiguous Memory"
 38	depends on ARCH_DISCONTIGMEM_ENABLE
 39	help
 40	  This option provides enhanced support for discontiguous
 41	  memory systems, over FLATMEM.  These systems have holes
 42	  in their physical address spaces, and this option provides
 43	  more efficient handling of these holes.
 44
 45	  Although "Discontiguous Memory" is still used by several
 46	  architectures, it is considered deprecated in favor of
 47	  "Sparse Memory".
 48
 49	  If unsure, choose "Sparse Memory" over this option.
 50
 51config SPARSEMEM_MANUAL
 52	bool "Sparse Memory"
 53	depends on ARCH_SPARSEMEM_ENABLE
 54	help
 55	  This will be the only option for some systems, including
 56	  memory hot-plug systems.  This is normal.
 57
 58	  This option provides efficient support for systems with
 59	  holes is their physical address space and allows memory
 60	  hot-plug and hot-remove.
 61
 62	  If unsure, choose "Flat Memory" over this option.
 63
 64endchoice
 65
 66config DISCONTIGMEM
 67	def_bool y
 68	depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
 69
 70config SPARSEMEM
 71	def_bool y
 72	depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
 73
 74config FLATMEM
 75	def_bool y
 76	depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
 77
 78config FLAT_NODE_MEM_MAP
 79	def_bool y
 80	depends on !SPARSEMEM
 81
 82#
 83# Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
 84# to represent different areas of memory.  This variable allows
 85# those dependencies to exist individually.
 86#
 87config NEED_MULTIPLE_NODES
 88	def_bool y
 89	depends on DISCONTIGMEM || NUMA
 90
 91#
 92# SPARSEMEM_EXTREME (which is the default) does some bootmem
 93# allocations when sparse_init() is called.  If this cannot
 94# be done on your architecture, select this option.  However,
 95# statically allocating the mem_section[] array can potentially
 96# consume vast quantities of .bss, so be careful.
 97#
 98# This option will also potentially produce smaller runtime code
 99# with gcc 3.4 and later.
100#
101config SPARSEMEM_STATIC
102	bool
103
104#
105# Architecture platforms which require a two level mem_section in SPARSEMEM
106# must select this option. This is usually for architecture platforms with
107# an extremely sparse physical address space.
108#
109config SPARSEMEM_EXTREME
110	def_bool y
111	depends on SPARSEMEM && !SPARSEMEM_STATIC
112
113config SPARSEMEM_VMEMMAP_ENABLE
114	bool
115
116config SPARSEMEM_VMEMMAP
117	bool "Sparse Memory virtual memmap"
118	depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
119	default y
120	help
121	  SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
122	  pfn_to_page and page_to_pfn operations.  This is the most
123	  efficient option when sufficient kernel resources are available.
124
125config HAVE_MEMBLOCK_PHYS_MAP
126	bool
127
128config HAVE_FAST_GUP
129	depends on MMU
130	bool
131
132# Don't discard allocated memory used to track "memory" and "reserved" memblocks
133# after early boot, so it can still be used to test for validity of memory.
134# Also, memblocks are updated with memory hot(un)plug.
135config ARCH_KEEP_MEMBLOCK
136	bool
137
138# Keep arch NUMA mapping infrastructure post-init.
139config NUMA_KEEP_MEMINFO
140	bool
141
142config MEMORY_ISOLATION
143	bool
144
 
 
 
 
 
 
 
145#
146# Only be set on architectures that have completely implemented memory hotplug
147# feature. If you are not sure, don't touch it.
148#
149config HAVE_BOOTMEM_INFO_NODE
150	def_bool n
151
 
 
 
 
 
 
152# eventually, we can have this option just 'select SPARSEMEM'
153config MEMORY_HOTPLUG
154	bool "Allow for memory hot-add"
155	depends on SPARSEMEM || X86_64_ACPI_NUMA
 
156	depends on ARCH_ENABLE_MEMORY_HOTPLUG
157	depends on 64BIT || BROKEN
158	select NUMA_KEEP_MEMINFO if NUMA
159
160config MEMORY_HOTPLUG_SPARSE
161	def_bool y
162	depends on SPARSEMEM && MEMORY_HOTPLUG
163
164config MEMORY_HOTPLUG_DEFAULT_ONLINE
165	bool "Online the newly added memory blocks by default"
166	depends on MEMORY_HOTPLUG
167	help
168	  This option sets the default policy setting for memory hotplug
169	  onlining policy (/sys/devices/system/memory/auto_online_blocks) which
170	  determines what happens to newly added memory regions. Policy setting
171	  can always be changed at runtime.
172	  See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
173
174	  Say Y here if you want all hot-plugged memory blocks to appear in
175	  'online' state by default.
176	  Say N here if you want the default policy to keep all hot-plugged
177	  memory blocks in 'offline' state.
178
179config MEMORY_HOTREMOVE
180	bool "Allow for memory hot remove"
181	select MEMORY_ISOLATION
182	select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
183	depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
184	depends on MIGRATION
185
 
 
 
 
 
 
 
186# Heavily threaded applications may benefit from splitting the mm-wide
187# page_table_lock, so that faults on different parts of the user address
188# space can be handled with less contention: split it at this NR_CPUS.
189# Default to 4 for wider testing, though 8 might be more appropriate.
190# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
191# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
192# SPARC32 allocates multiple pte tables within a single page, and therefore
193# a per-page lock leads to problems when multiple tables need to be locked
194# at the same time (e.g. copy_page_range()).
195# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
196#
197config SPLIT_PTLOCK_CPUS
198	int
199	default "999999" if !MMU
200	default "999999" if ARM && !CPU_CACHE_VIPT
201	default "999999" if PARISC && !PA20
202	default "999999" if SPARC32
203	default "4"
204
205config ARCH_ENABLE_SPLIT_PMD_PTLOCK
206	bool
207
208#
209# support for memory balloon
210config MEMORY_BALLOON
211	bool
212
213#
214# support for memory balloon compaction
215config BALLOON_COMPACTION
216	bool "Allow for balloon memory compaction/migration"
217	def_bool y
218	depends on COMPACTION && MEMORY_BALLOON
219	help
220	  Memory fragmentation introduced by ballooning might reduce
221	  significantly the number of 2MB contiguous memory blocks that can be
222	  used within a guest, thus imposing performance penalties associated
223	  with the reduced number of transparent huge pages that could be used
224	  by the guest workload. Allowing the compaction & migration for memory
225	  pages enlisted as being part of memory balloon devices avoids the
226	  scenario aforementioned and helps improving memory defragmentation.
227
228#
229# support for memory compaction
230config COMPACTION
231	bool "Allow for memory compaction"
232	def_bool y
233	select MIGRATION
234	depends on MMU
235	help
236	  Compaction is the only memory management component to form
237	  high order (larger physically contiguous) memory blocks
238	  reliably. The page allocator relies on compaction heavily and
239	  the lack of the feature can lead to unexpected OOM killer
240	  invocations for high order memory requests. You shouldn't
241	  disable this option unless there really is a strong reason for
242	  it and then we would be really interested to hear about that at
243	  linux-mm@kvack.org.
244
 
 
 
 
 
 
245#
246# support for free page reporting
247config PAGE_REPORTING
248	bool "Free page reporting"
249	def_bool n
250	help
251	  Free page reporting allows for the incremental acquisition of
252	  free pages from the buddy allocator for the purpose of reporting
253	  those pages to another entity, such as a hypervisor, so that the
254	  memory can be freed within the host for other uses.
255
256#
257# support for page migration
258#
259config MIGRATION
260	bool "Page migration"
261	def_bool y
262	depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
263	help
264	  Allows the migration of the physical location of pages of processes
265	  while the virtual addresses are not changed. This is useful in
266	  two situations. The first is on NUMA systems to put pages nearer
267	  to the processors accessing. The second is when allocating huge
268	  pages as migration can relocate pages to satisfy a huge page
269	  allocation instead of reclaiming.
270
 
 
 
271config ARCH_ENABLE_HUGEPAGE_MIGRATION
272	bool
273
274config ARCH_ENABLE_THP_MIGRATION
275	bool
276
 
 
 
 
 
 
 
 
 
 
277config CONTIG_ALLOC
278	def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
279
280config PHYS_ADDR_T_64BIT
281	def_bool 64BIT
282
283config BOUNCE
284	bool "Enable bounce buffers"
285	default y
286	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
287	help
288	  Enable bounce buffers for devices that cannot access
289	  the full range of memory available to the CPU. Enabled
290	  by default when ZONE_DMA or HIGHMEM is selected, but you
291	  may say n to override this.
292
293config VIRT_TO_BUS
294	bool
295	help
296	  An architecture should select this if it implements the
297	  deprecated interface virt_to_bus().  All new architectures
298	  should probably not select this.
299
300
301config MMU_NOTIFIER
302	bool
303	select SRCU
304	select INTERVAL_TREE
305
306config KSM
307	bool "Enable KSM for page merging"
308	depends on MMU
309	select XXHASH
310	help
311	  Enable Kernel Samepage Merging: KSM periodically scans those areas
312	  of an application's address space that an app has advised may be
313	  mergeable.  When it finds pages of identical content, it replaces
314	  the many instances by a single page with that content, so
315	  saving memory until one or another app needs to modify the content.
316	  Recommended for use with KVM, or with other duplicative applications.
317	  See Documentation/vm/ksm.rst for more information: KSM is inactive
318	  until a program has madvised that an area is MADV_MERGEABLE, and
319	  root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
320
321config DEFAULT_MMAP_MIN_ADDR
322	int "Low address space to protect from user allocation"
323	depends on MMU
324	default 4096
325	help
326	  This is the portion of low virtual memory which should be protected
327	  from userspace allocation.  Keeping a user from writing to low pages
328	  can help reduce the impact of kernel NULL pointer bugs.
329
330	  For most ia64, ppc64 and x86 users with lots of address space
331	  a value of 65536 is reasonable and should cause no problems.
332	  On arm and other archs it should not be higher than 32768.
333	  Programs which use vm86 functionality or have some need to map
334	  this low address space will need CAP_SYS_RAWIO or disable this
335	  protection by setting the value to 0.
336
337	  This value can be changed after boot using the
338	  /proc/sys/vm/mmap_min_addr tunable.
339
340config ARCH_SUPPORTS_MEMORY_FAILURE
341	bool
342
343config MEMORY_FAILURE
344	depends on MMU
345	depends on ARCH_SUPPORTS_MEMORY_FAILURE
346	bool "Enable recovery from hardware memory errors"
347	select MEMORY_ISOLATION
348	select RAS
349	help
350	  Enables code to recover from some memory failures on systems
351	  with MCA recovery. This allows a system to continue running
352	  even when some of its memory has uncorrected errors. This requires
353	  special hardware support and typically ECC memory.
354
355config HWPOISON_INJECT
356	tristate "HWPoison pages injector"
357	depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
358	select PROC_PAGE_MONITOR
359
360config NOMMU_INITIAL_TRIM_EXCESS
361	int "Turn on mmap() excess space trimming before booting"
362	depends on !MMU
363	default 1
364	help
365	  The NOMMU mmap() frequently needs to allocate large contiguous chunks
366	  of memory on which to store mappings, but it can only ask the system
367	  allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
368	  more than it requires.  To deal with this, mmap() is able to trim off
369	  the excess and return it to the allocator.
370
371	  If trimming is enabled, the excess is trimmed off and returned to the
372	  system allocator, which can cause extra fragmentation, particularly
373	  if there are a lot of transient processes.
374
375	  If trimming is disabled, the excess is kept, but not used, which for
376	  long-term mappings means that the space is wasted.
377
378	  Trimming can be dynamically controlled through a sysctl option
379	  (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
380	  excess pages there must be before trimming should occur, or zero if
381	  no trimming is to occur.
382
383	  This option specifies the initial value of this option.  The default
384	  of 1 says that all excess pages should be trimmed.
385
386	  See Documentation/mm/nommu-mmap.rst for more information.
 
 
 
 
 
 
387
388config TRANSPARENT_HUGEPAGE
389	bool "Transparent Hugepage Support"
390	depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
391	select COMPACTION
392	select XARRAY_MULTI
393	help
394	  Transparent Hugepages allows the kernel to use huge pages and
395	  huge tlb transparently to the applications whenever possible.
396	  This feature can improve computing performance to certain
397	  applications by speeding up page faults during memory
398	  allocation, by reducing the number of tlb misses and by speeding
399	  up the pagetable walking.
400
401	  If memory constrained on embedded, you may want to say N.
402
 
 
403choice
404	prompt "Transparent Hugepage Support sysfs defaults"
405	depends on TRANSPARENT_HUGEPAGE
406	default TRANSPARENT_HUGEPAGE_ALWAYS
407	help
408	  Selects the sysfs defaults for Transparent Hugepage Support.
409
410	config TRANSPARENT_HUGEPAGE_ALWAYS
411		bool "always"
412	help
413	  Enabling Transparent Hugepage always, can increase the
414	  memory footprint of applications without a guaranteed
415	  benefit but it will work automatically for all applications.
416
417	config TRANSPARENT_HUGEPAGE_MADVISE
418		bool "madvise"
419	help
420	  Enabling Transparent Hugepage madvise, will only provide a
421	  performance improvement benefit to the applications using
422	  madvise(MADV_HUGEPAGE) but it won't risk to increase the
423	  memory footprint of applications without a guaranteed
424	  benefit.
425endchoice
426
427config ARCH_WANTS_THP_SWAP
428	def_bool n
429
430config THP_SWAP
431	def_bool y
432	depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
433	help
434	  Swap transparent huge pages in one piece, without splitting.
435	  XXX: For now, swap cluster backing transparent huge page
436	  will be split after swapout.
437
438	  For selection by architectures with reasonable THP sizes.
439
 
 
 
 
 
 
 
 
 
 
 
 
 
440#
441# UP and nommu archs use km based percpu allocator
442#
443config NEED_PER_CPU_KM
444	depends on !SMP
445	bool
446	default y
447
448config CLEANCACHE
449	bool "Enable cleancache driver to cache clean pages if tmem is present"
450	help
451	  Cleancache can be thought of as a page-granularity victim cache
452	  for clean pages that the kernel's pageframe replacement algorithm
453	  (PFRA) would like to keep around, but can't since there isn't enough
454	  memory.  So when the PFRA "evicts" a page, it first attempts to use
455	  cleancache code to put the data contained in that page into
456	  "transcendent memory", memory that is not directly accessible or
457	  addressable by the kernel and is of unknown and possibly
458	  time-varying size.  And when a cleancache-enabled
459	  filesystem wishes to access a page in a file on disk, it first
460	  checks cleancache to see if it already contains it; if it does,
461	  the page is copied into the kernel and a disk access is avoided.
462	  When a transcendent memory driver is available (such as zcache or
463	  Xen transcendent memory), a significant I/O reduction
464	  may be achieved.  When none is available, all cleancache calls
465	  are reduced to a single pointer-compare-against-NULL resulting
466	  in a negligible performance hit.
467
468	  If unsure, say Y to enable cleancache
 
469
470config FRONTSWAP
471	bool "Enable frontswap to cache swap pages if tmem is present"
472	depends on SWAP
473	help
474	  Frontswap is so named because it can be thought of as the opposite
475	  of a "backing" store for a swap device.  The data is stored into
476	  "transcendent memory", memory that is not directly accessible or
477	  addressable by the kernel and is of unknown and possibly
478	  time-varying size.  When space in transcendent memory is available,
479	  a significant swap I/O reduction may be achieved.  When none is
480	  available, all frontswap calls are reduced to a single pointer-
481	  compare-against-NULL resulting in a negligible performance hit
482	  and swap data is stored as normal on the matching swap device.
483
484	  If unsure, say Y to enable frontswap.
 
 
 
 
485
486config CMA
487	bool "Contiguous Memory Allocator"
488	depends on MMU
489	select MIGRATION
490	select MEMORY_ISOLATION
491	help
492	  This enables the Contiguous Memory Allocator which allows other
493	  subsystems to allocate big physically-contiguous blocks of memory.
494	  CMA reserves a region of memory and allows only movable pages to
495	  be allocated from it. This way, the kernel can use the memory for
496	  pagecache and when a subsystem requests for contiguous area, the
497	  allocated pages are migrated away to serve the contiguous request.
498
499	  If unsure, say "n".
500
501config CMA_DEBUG
502	bool "CMA debug messages (DEVELOPMENT)"
503	depends on DEBUG_KERNEL && CMA
504	help
505	  Turns on debug messages in CMA.  This produces KERN_DEBUG
506	  messages for every CMA call as well as various messages while
507	  processing calls such as dma_alloc_from_contiguous().
508	  This option does not affect warning and error messages.
509
510config CMA_DEBUGFS
511	bool "CMA debugfs interface"
512	depends on CMA && DEBUG_FS
513	help
514	  Turns on the DebugFS interface for CMA.
515
 
 
 
 
 
 
 
516config CMA_AREAS
517	int "Maximum count of the CMA areas"
518	depends on CMA
 
519	default 7
520	help
521	  CMA allows to create CMA areas for particular purpose, mainly,
522	  used as device private area. This parameter sets the maximum
523	  number of CMA area in the system.
524
525	  If unsure, leave the default value "7".
526
527config MEM_SOFT_DIRTY
528	bool "Track memory changes"
529	depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
530	select PROC_PAGE_MONITOR
531	help
532	  This option enables memory changes tracking by introducing a
533	  soft-dirty bit on pte-s. This bit it set when someone writes
534	  into a page just as regular dirty bit, but unlike the latter
535	  it can be cleared by hands.
536
537	  See Documentation/admin-guide/mm/soft-dirty.rst for more details.
538
539config ZSWAP
540	bool "Compressed cache for swap pages (EXPERIMENTAL)"
541	depends on FRONTSWAP && CRYPTO=y
542	select ZPOOL
543	help
544	  A lightweight compressed cache for swap pages.  It takes
545	  pages that are in the process of being swapped out and attempts to
546	  compress them into a dynamically allocated RAM-based memory pool.
547	  This can result in a significant I/O reduction on swap device and,
548	  in the case where decompressing from RAM is faster that swap device
549	  reads, can also improve workload performance.
550
551	  This is marked experimental because it is a new feature (as of
552	  v3.11) that interacts heavily with memory reclaim.  While these
553	  interactions don't cause any known issues on simple memory setups,
554	  they have not be fully explored on the large set of potential
555	  configurations and workloads that exist.
556
557choice
558	prompt "Compressed cache for swap pages default compressor"
559	depends on ZSWAP
560	default ZSWAP_COMPRESSOR_DEFAULT_LZO
561	help
562	  Selects the default compression algorithm for the compressed cache
563	  for swap pages.
564
565	  For an overview what kind of performance can be expected from
566	  a particular compression algorithm please refer to the benchmarks
567	  available at the following LWN page:
568	  https://lwn.net/Articles/751795/
569
570	  If in doubt, select 'LZO'.
571
572	  The selection made here can be overridden by using the kernel
573	  command line 'zswap.compressor=' option.
574
575config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
576	bool "Deflate"
577	select CRYPTO_DEFLATE
578	help
579	  Use the Deflate algorithm as the default compression algorithm.
580
581config ZSWAP_COMPRESSOR_DEFAULT_LZO
582	bool "LZO"
583	select CRYPTO_LZO
584	help
585	  Use the LZO algorithm as the default compression algorithm.
586
587config ZSWAP_COMPRESSOR_DEFAULT_842
588	bool "842"
589	select CRYPTO_842
590	help
591	  Use the 842 algorithm as the default compression algorithm.
592
593config ZSWAP_COMPRESSOR_DEFAULT_LZ4
594	bool "LZ4"
595	select CRYPTO_LZ4
596	help
597	  Use the LZ4 algorithm as the default compression algorithm.
598
599config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
600	bool "LZ4HC"
601	select CRYPTO_LZ4HC
602	help
603	  Use the LZ4HC algorithm as the default compression algorithm.
604
605config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
606	bool "zstd"
607	select CRYPTO_ZSTD
608	help
609	  Use the zstd algorithm as the default compression algorithm.
610endchoice
611
612config ZSWAP_COMPRESSOR_DEFAULT
613       string
614       depends on ZSWAP
615       default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
616       default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
617       default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
618       default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
619       default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
620       default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
621       default ""
622
623choice
624	prompt "Compressed cache for swap pages default allocator"
625	depends on ZSWAP
626	default ZSWAP_ZPOOL_DEFAULT_ZBUD
627	help
628	  Selects the default allocator for the compressed cache for
629	  swap pages.
630	  The default is 'zbud' for compatibility, however please do
631	  read the description of each of the allocators below before
632	  making a right choice.
633
634	  The selection made here can be overridden by using the kernel
635	  command line 'zswap.zpool=' option.
636
637config ZSWAP_ZPOOL_DEFAULT_ZBUD
638	bool "zbud"
639	select ZBUD
640	help
641	  Use the zbud allocator as the default allocator.
642
643config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
644	bool "z3fold"
645	select Z3FOLD
646	help
647	  Use the z3fold allocator as the default allocator.
648
649config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
650	bool "zsmalloc"
651	select ZSMALLOC
652	help
653	  Use the zsmalloc allocator as the default allocator.
654endchoice
655
656config ZSWAP_ZPOOL_DEFAULT
657       string
658       depends on ZSWAP
659       default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
660       default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
661       default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
662       default ""
663
664config ZSWAP_DEFAULT_ON
665	bool "Enable the compressed cache for swap pages by default"
666	depends on ZSWAP
667	help
668	  If selected, the compressed cache for swap pages will be enabled
669	  at boot, otherwise it will be disabled.
670
671	  The selection made here can be overridden by using the kernel
672	  command line 'zswap.enabled=' option.
673
674config ZPOOL
675	tristate "Common API for compressed memory storage"
676	help
677	  Compressed memory storage API.  This allows using either zbud or
678	  zsmalloc.
679
680config ZBUD
681	tristate "Low (Up to 2x) density storage for compressed pages"
682	help
683	  A special purpose allocator for storing compressed pages.
684	  It is designed to store up to two compressed pages per physical
685	  page.  While this design limits storage density, it has simple and
686	  deterministic reclaim properties that make it preferable to a higher
687	  density approach when reclaim will be used.
688
689config Z3FOLD
690	tristate "Up to 3x density storage for compressed pages"
691	depends on ZPOOL
692	help
693	  A special purpose allocator for storing compressed pages.
694	  It is designed to store up to three compressed pages per physical
695	  page. It is a ZBUD derivative so the simplicity and determinism are
696	  still there.
697
698config ZSMALLOC
699	tristate "Memory allocator for compressed pages"
700	depends on MMU
701	help
702	  zsmalloc is a slab-based memory allocator designed to store
703	  compressed RAM pages.  zsmalloc uses virtual memory mapping
704	  in order to reduce fragmentation.  However, this results in a
705	  non-standard allocator interface where a handle, not a pointer, is
706	  returned by an alloc().  This handle must be mapped in order to
707	  access the allocated space.
708
709config ZSMALLOC_PGTABLE_MAPPING
710	bool "Use page table mapping to access object in zsmalloc"
711	depends on ZSMALLOC=y
712	help
713	  By default, zsmalloc uses a copy-based object mapping method to
714	  access allocations that span two pages. However, if a particular
715	  architecture (ex, ARM) performs VM mapping faster than copying,
716	  then you should select this. This causes zsmalloc to use page table
717	  mapping rather than copying for object mapping.
718
719	  You can check speed with zsmalloc benchmark:
720	  https://github.com/spartacus06/zsmapbench
721
722config ZSMALLOC_STAT
723	bool "Export zsmalloc statistics"
724	depends on ZSMALLOC
725	select DEBUG_FS
726	help
727	  This option enables code in the zsmalloc to collect various
728	  statistics about whats happening in zsmalloc and exports that
729	  information to userspace via debugfs.
730	  If unsure, say N.
731
732config GENERIC_EARLY_IOREMAP
733	bool
734
735config MAX_STACK_SIZE_MB
736	int "Maximum user stack size for 32-bit processes (MB)"
737	default 80
738	range 8 2048
739	depends on STACK_GROWSUP && (!64BIT || COMPAT)
740	help
741	  This is the maximum stack size in Megabytes in the VM layout of 32-bit
742	  user processes when the stack grows upwards (currently only on parisc
743	  arch). The stack will be located at the highest memory address minus
744	  the given value, unless the RLIMIT_STACK hard limit is changed to a
745	  smaller value in which case that is used.
746
747	  A sane initial value is 80 MB.
748
749config DEFERRED_STRUCT_PAGE_INIT
750	bool "Defer initialisation of struct pages to kthreads"
751	depends on SPARSEMEM
752	depends on !NEED_PER_CPU_KM
753	depends on 64BIT
754	select PADATA
755	help
756	  Ordinarily all struct pages are initialised during early boot in a
757	  single thread. On very large machines this can take a considerable
758	  amount of time. If this option is set, large machines will bring up
759	  a subset of memmap at boot and then initialise the rest in parallel.
760	  This has a potential performance impact on tasks running early in the
761	  lifetime of the system until these kthreads finish the
762	  initialisation.
763
 
 
 
 
 
 
 
 
764config IDLE_PAGE_TRACKING
765	bool "Enable idle page tracking"
766	depends on SYSFS && MMU
767	select PAGE_EXTENSION if !64BIT
768	help
769	  This feature allows to estimate the amount of user pages that have
770	  not been touched during a given period of time. This information can
771	  be useful to tune memory cgroup limits and/or for job placement
772	  within a compute cluster.
773
774	  See Documentation/admin-guide/mm/idle_page_tracking.rst for
775	  more details.
776
 
 
 
 
 
 
 
 
 
 
 
 
777config ARCH_HAS_PTE_DEVMAP
778	bool
779
 
 
 
 
 
 
 
 
 
 
 
 
780config ZONE_DEVICE
781	bool "Device memory (pmem, HMM, etc...) hotplug support"
782	depends on MEMORY_HOTPLUG
783	depends on MEMORY_HOTREMOVE
784	depends on SPARSEMEM_VMEMMAP
785	depends on ARCH_HAS_PTE_DEVMAP
786	select XARRAY_MULTI
787
788	help
789	  Device memory hotplug support allows for establishing pmem,
790	  or other device driver discovered memory regions, in the
791	  memmap. This allows pfn_to_page() lookups of otherwise
792	  "device-physical" addresses which is needed for using a DAX
793	  mapping in an O_DIRECT operation, among other things.
794
795	  If FS_DAX is enabled, then say Y.
796
797config DEV_PAGEMAP_OPS
798	bool
799
800#
801# Helpers to mirror range of the CPU page tables of a process into device page
802# tables.
803#
804config HMM_MIRROR
805	bool
806	depends on MMU
807
 
 
 
 
808config DEVICE_PRIVATE
809	bool "Unaddressable device memory (GPU memory, ...)"
810	depends on ZONE_DEVICE
811	select DEV_PAGEMAP_OPS
812
813	help
814	  Allows creation of struct pages to represent unaddressable device
815	  memory; i.e., memory that is only accessible from the device (or
816	  group of devices). You likely also want to select HMM_MIRROR.
817
818config FRAME_VECTOR
819	bool
820
821config ARCH_USES_HIGH_VMA_FLAGS
822	bool
823config ARCH_HAS_PKEYS
824	bool
825
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
826config PERCPU_STATS
827	bool "Collect percpu memory statistics"
828	help
829	  This feature collects and exposes statistics via debugfs. The
830	  information includes global and per chunk statistics, which can
831	  be used to help understand percpu memory usage.
832
833config GUP_BENCHMARK
834	bool "Enable infrastructure for get_user_pages_fast() benchmarking"
835	help
836	  Provides /sys/kernel/debug/gup_benchmark that helps with testing
837	  performance of get_user_pages_fast().
 
 
 
 
 
 
 
 
 
 
 
 
838
839	  See tools/testing/selftests/vm/gup_benchmark.c
840
841config GUP_GET_PTE_LOW_HIGH
842	bool
843
844config READ_ONLY_THP_FOR_FS
845	bool "Read-only THP for filesystems (EXPERIMENTAL)"
846	depends on TRANSPARENT_HUGEPAGE && SHMEM
847
848	help
849	  Allow khugepaged to put read-only file-backed pages in THP.
850
851	  This is marked experimental because it is a new feature. Write
852	  support of file THPs will be developed in the next few release
853	  cycles.
854
855config ARCH_HAS_PTE_SPECIAL
856	bool
857
858#
859# Some architectures require a special hugepage directory format that is
860# required to support multiple hugepage sizes. For example a4fe3ce76
861# "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
862# introduced it on powerpc.  This allows for a more flexible hugepage
863# pagetable layouts.
864#
865config ARCH_HAS_HUGEPD
866	bool
867
868config MAPPING_DIRTY_HELPERS
869        bool
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
870
871endmenu
v6.2
   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 FRONTSWAP
  29	select CRYPTO
  30	select ZPOOL
  31	help
  32	  A lightweight compressed cache for swap pages.  It takes
  33	  pages that are in the process of being swapped out and attempts to
  34	  compress them into a dynamically allocated RAM-based memory pool.
  35	  This can result in a significant I/O reduction on swap device and,
  36	  in the case where decompressing from RAM is faster than swap device
  37	  reads, can also improve workload performance.
  38
  39config ZSWAP_DEFAULT_ON
  40	bool "Enable the compressed cache for swap pages by default"
  41	depends on ZSWAP
  42	help
  43	  If selected, the compressed cache for swap pages will be enabled
  44	  at boot, otherwise it will be disabled.
  45
  46	  The selection made here can be overridden by using the kernel
  47	  command line 'zswap.enabled=' option.
  48
  49choice
  50	prompt "Default compressor"
  51	depends on ZSWAP
  52	default ZSWAP_COMPRESSOR_DEFAULT_LZO
  53	help
  54	  Selects the default compression algorithm for the compressed cache
  55	  for swap pages.
  56
  57	  For an overview what kind of performance can be expected from
  58	  a particular compression algorithm please refer to the benchmarks
  59	  available at the following LWN page:
  60	  https://lwn.net/Articles/751795/
  61
  62	  If in doubt, select 'LZO'.
  63
  64	  The selection made here can be overridden by using the kernel
  65	  command line 'zswap.compressor=' option.
  66
  67config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
  68	bool "Deflate"
  69	select CRYPTO_DEFLATE
  70	help
  71	  Use the Deflate algorithm as the default compression algorithm.
  72
  73config ZSWAP_COMPRESSOR_DEFAULT_LZO
  74	bool "LZO"
  75	select CRYPTO_LZO
  76	help
  77	  Use the LZO algorithm as the default compression algorithm.
  78
  79config ZSWAP_COMPRESSOR_DEFAULT_842
  80	bool "842"
  81	select CRYPTO_842
  82	help
  83	  Use the 842 algorithm as the default compression algorithm.
  84
  85config ZSWAP_COMPRESSOR_DEFAULT_LZ4
  86	bool "LZ4"
  87	select CRYPTO_LZ4
  88	help
  89	  Use the LZ4 algorithm as the default compression algorithm.
  90
  91config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
  92	bool "LZ4HC"
  93	select CRYPTO_LZ4HC
  94	help
  95	  Use the LZ4HC algorithm as the default compression algorithm.
  96
  97config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
  98	bool "zstd"
  99	select CRYPTO_ZSTD
 100	help
 101	  Use the zstd algorithm as the default compression algorithm.
 102endchoice
 103
 104config ZSWAP_COMPRESSOR_DEFAULT
 105       string
 106       depends on ZSWAP
 107       default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
 108       default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
 109       default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
 110       default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
 111       default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
 112       default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
 113       default ""
 114
 115choice
 116	prompt "Default allocator"
 117	depends on ZSWAP
 118	default ZSWAP_ZPOOL_DEFAULT_ZBUD
 119	help
 120	  Selects the default allocator for the compressed cache for
 121	  swap pages.
 122	  The default is 'zbud' for compatibility, however please do
 123	  read the description of each of the allocators below before
 124	  making a right choice.
 125
 126	  The selection made here can be overridden by using the kernel
 127	  command line 'zswap.zpool=' option.
 128
 129config ZSWAP_ZPOOL_DEFAULT_ZBUD
 130	bool "zbud"
 131	select ZBUD
 132	help
 133	  Use the zbud allocator as the default allocator.
 134
 135config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
 136	bool "z3fold"
 137	select Z3FOLD
 138	help
 139	  Use the z3fold allocator as the default allocator.
 140
 141config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
 142	bool "zsmalloc"
 143	select ZSMALLOC
 144	help
 145	  Use the zsmalloc allocator as the default allocator.
 146endchoice
 147
 148config ZSWAP_ZPOOL_DEFAULT
 149       string
 150       depends on ZSWAP
 151       default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
 152       default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
 153       default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
 154       default ""
 155
 156config ZBUD
 157	tristate "2:1 compression allocator (zbud)"
 158	depends on ZSWAP
 159	help
 160	  A special purpose allocator for storing compressed pages.
 161	  It is designed to store up to two compressed pages per physical
 162	  page.  While this design limits storage density, it has simple and
 163	  deterministic reclaim properties that make it preferable to a higher
 164	  density approach when reclaim will be used.
 165
 166config Z3FOLD
 167	tristate "3:1 compression allocator (z3fold)"
 168	depends on ZSWAP
 169	help
 170	  A special purpose allocator for storing compressed pages.
 171	  It is designed to store up to three compressed pages per physical
 172	  page. It is a ZBUD derivative so the simplicity and determinism are
 173	  still there.
 174
 175config ZSMALLOC
 176	tristate
 177	prompt "N:1 compression allocator (zsmalloc)" if ZSWAP
 178	depends on MMU
 179	help
 180	  zsmalloc is a slab-based memory allocator designed to store
 181	  pages of various compression levels efficiently. It achieves
 182	  the highest storage density with the least amount of fragmentation.
 183
 184config ZSMALLOC_STAT
 185	bool "Export zsmalloc statistics"
 186	depends on ZSMALLOC
 187	select DEBUG_FS
 188	help
 189	  This option enables code in the zsmalloc to collect various
 190	  statistics about what's happening in zsmalloc and exports that
 191	  information to userspace via debugfs.
 192	  If unsure, say N.
 193
 194menu "SLAB allocator options"
 195
 196choice
 197	prompt "Choose SLAB allocator"
 198	default SLUB
 199	help
 200	   This option allows to select a slab allocator.
 201
 202config SLAB
 203	bool "SLAB"
 204	depends on !PREEMPT_RT
 205	select HAVE_HARDENED_USERCOPY_ALLOCATOR
 206	help
 207	  The regular slab allocator that is established and known to work
 208	  well in all environments. It organizes cache hot objects in
 209	  per cpu and per node queues.
 210
 211config SLUB
 212	bool "SLUB (Unqueued Allocator)"
 213	select HAVE_HARDENED_USERCOPY_ALLOCATOR
 214	help
 215	   SLUB is a slab allocator that minimizes cache line usage
 216	   instead of managing queues of cached objects (SLAB approach).
 217	   Per cpu caching is realized using slabs of objects instead
 218	   of queues of objects. SLUB can use memory efficiently
 219	   and has enhanced diagnostics. SLUB is the default choice for
 220	   a slab allocator.
 221
 222config SLOB_DEPRECATED
 223	depends on EXPERT
 224	bool "SLOB (Simple Allocator - DEPRECATED)"
 225	depends on !PREEMPT_RT
 226	help
 227	   Deprecated and scheduled for removal in a few cycles. SLUB
 228	   recommended as replacement. CONFIG_SLUB_TINY can be considered
 229	   on systems with 16MB or less RAM.
 230
 231	   If you need SLOB to stay, please contact linux-mm@kvack.org and
 232	   people listed in the SLAB ALLOCATOR section of MAINTAINERS file,
 233	   with your use case.
 234
 235	   SLOB replaces the stock allocator with a drastically simpler
 236	   allocator. SLOB is generally more space efficient but
 237	   does not perform as well on large systems.
 238
 239endchoice
 240
 241config SLOB
 242	bool
 243	default y
 244	depends on SLOB_DEPRECATED
 245
 246config SLUB_TINY
 247	bool "Configure SLUB for minimal memory footprint"
 248	depends on SLUB && EXPERT
 249	select SLAB_MERGE_DEFAULT
 250	help
 251	   Configures the SLUB allocator in a way to achieve minimal memory
 252	   footprint, sacrificing scalability, debugging and other features.
 253	   This is intended only for the smallest system that had used the
 254	   SLOB allocator and is not recommended for systems with more than
 255	   16MB RAM.
 256
 257	   If unsure, say N.
 258
 259config SLAB_MERGE_DEFAULT
 260	bool "Allow slab caches to be merged"
 261	default y
 262	depends on SLAB || SLUB
 263	help
 264	  For reduced kernel memory fragmentation, slab caches can be
 265	  merged when they share the same size and other characteristics.
 266	  This carries a risk of kernel heap overflows being able to
 267	  overwrite objects from merged caches (and more easily control
 268	  cache layout), which makes such heap attacks easier to exploit
 269	  by attackers. By keeping caches unmerged, these kinds of exploits
 270	  can usually only damage objects in the same cache. To disable
 271	  merging at runtime, "slab_nomerge" can be passed on the kernel
 272	  command line.
 273
 274config SLAB_FREELIST_RANDOM
 275	bool "Randomize slab freelist"
 276	depends on SLAB || (SLUB && !SLUB_TINY)
 277	help
 278	  Randomizes the freelist order used on creating new pages. This
 279	  security feature reduces the predictability of the kernel slab
 280	  allocator against heap overflows.
 281
 282config SLAB_FREELIST_HARDENED
 283	bool "Harden slab freelist metadata"
 284	depends on SLAB || (SLUB && !SLUB_TINY)
 285	help
 286	  Many kernel heap attacks try to target slab cache metadata and
 287	  other infrastructure. This options makes minor performance
 288	  sacrifices to harden the kernel slab allocator against common
 289	  freelist exploit methods. Some slab implementations have more
 290	  sanity-checking than others. This option is most effective with
 291	  CONFIG_SLUB.
 292
 293config SLUB_STATS
 294	default n
 295	bool "Enable SLUB performance statistics"
 296	depends on SLUB && SYSFS && !SLUB_TINY
 297	help
 298	  SLUB statistics are useful to debug SLUBs allocation behavior in
 299	  order find ways to optimize the allocator. This should never be
 300	  enabled for production use since keeping statistics slows down
 301	  the allocator by a few percentage points. The slabinfo command
 302	  supports the determination of the most active slabs to figure
 303	  out which slabs are relevant to a particular load.
 304	  Try running: slabinfo -DA
 305
 306config SLUB_CPU_PARTIAL
 307	default y
 308	depends on SLUB && SMP && !SLUB_TINY
 309	bool "SLUB per cpu partial cache"
 310	help
 311	  Per cpu partial caches accelerate objects allocation and freeing
 312	  that is local to a processor at the price of more indeterminism
 313	  in the latency of the free. On overflow these caches will be cleared
 314	  which requires the taking of locks that may cause latency spikes.
 315	  Typically one would choose no for a realtime system.
 316
 317endmenu # SLAB allocator options
 318
 319config SHUFFLE_PAGE_ALLOCATOR
 320	bool "Page allocator randomization"
 321	default SLAB_FREELIST_RANDOM && ACPI_NUMA
 322	help
 323	  Randomization of the page allocator improves the average
 324	  utilization of a direct-mapped memory-side-cache. See section
 325	  5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
 326	  6.2a specification for an example of how a platform advertises
 327	  the presence of a memory-side-cache. There are also incidental
 328	  security benefits as it reduces the predictability of page
 329	  allocations to compliment SLAB_FREELIST_RANDOM, but the
 330	  default granularity of shuffling on the "MAX_ORDER - 1" i.e,
 331	  10th order of pages is selected based on cache utilization
 332	  benefits on x86.
 333
 334	  While the randomization improves cache utilization it may
 335	  negatively impact workloads on platforms without a cache. For
 336	  this reason, by default, the randomization is enabled only
 337	  after runtime detection of a direct-mapped memory-side-cache.
 338	  Otherwise, the randomization may be force enabled with the
 339	  'page_alloc.shuffle' kernel command line parameter.
 340
 341	  Say Y if unsure.
 342
 343config COMPAT_BRK
 344	bool "Disable heap randomization"
 345	default y
 346	help
 347	  Randomizing heap placement makes heap exploits harder, but it
 348	  also breaks ancient binaries (including anything libc5 based).
 349	  This option changes the bootup default to heap randomization
 350	  disabled, and can be overridden at runtime by setting
 351	  /proc/sys/kernel/randomize_va_space to 2.
 352
 353	  On non-ancient distros (post-2000 ones) N is usually a safe choice.
 354
 355config MMAP_ALLOW_UNINITIALIZED
 356	bool "Allow mmapped anonymous memory to be uninitialized"
 357	depends on EXPERT && !MMU
 358	default n
 359	help
 360	  Normally, and according to the Linux spec, anonymous memory obtained
 361	  from mmap() has its contents cleared before it is passed to
 362	  userspace.  Enabling this config option allows you to request that
 363	  mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
 364	  providing a huge performance boost.  If this option is not enabled,
 365	  then the flag will be ignored.
 366
 367	  This is taken advantage of by uClibc's malloc(), and also by
 368	  ELF-FDPIC binfmt's brk and stack allocator.
 369
 370	  Because of the obvious security issues, this option should only be
 371	  enabled on embedded devices where you control what is run in
 372	  userspace.  Since that isn't generally a problem on no-MMU systems,
 373	  it is normally safe to say Y here.
 374
 375	  See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
 376
 377config SELECT_MEMORY_MODEL
 378	def_bool y
 379	depends on ARCH_SELECT_MEMORY_MODEL
 380
 381choice
 382	prompt "Memory model"
 383	depends on SELECT_MEMORY_MODEL
 
 384	default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
 385	default FLATMEM_MANUAL
 386	help
 387	  This option allows you to change some of the ways that
 388	  Linux manages its memory internally. Most users will
 389	  only have one option here selected by the architecture
 390	  configuration. This is normal.
 391
 392config FLATMEM_MANUAL
 393	bool "Flat Memory"
 394	depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE
 395	help
 396	  This option is best suited for non-NUMA systems with
 397	  flat address space. The FLATMEM is the most efficient
 398	  system in terms of performance and resource consumption
 399	  and it is the best option for smaller systems.
 400
 401	  For systems that have holes in their physical address
 402	  spaces and for features like NUMA and memory hotplug,
 403	  choose "Sparse Memory".
 404
 405	  If unsure, choose this option (Flat Memory) over any other.
 406
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 407config SPARSEMEM_MANUAL
 408	bool "Sparse Memory"
 409	depends on ARCH_SPARSEMEM_ENABLE
 410	help
 411	  This will be the only option for some systems, including
 412	  memory hot-plug systems.  This is normal.
 413
 414	  This option provides efficient support for systems with
 415	  holes is their physical address space and allows memory
 416	  hot-plug and hot-remove.
 417
 418	  If unsure, choose "Flat Memory" over this option.
 419
 420endchoice
 421
 
 
 
 
 422config SPARSEMEM
 423	def_bool y
 424	depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
 425
 426config FLATMEM
 427	def_bool y
 428	depends on !SPARSEMEM || FLATMEM_MANUAL
 
 
 
 
 
 
 
 
 
 
 
 
 
 429
 430#
 431# SPARSEMEM_EXTREME (which is the default) does some bootmem
 432# allocations when sparse_init() is called.  If this cannot
 433# be done on your architecture, select this option.  However,
 434# statically allocating the mem_section[] array can potentially
 435# consume vast quantities of .bss, so be careful.
 436#
 437# This option will also potentially produce smaller runtime code
 438# with gcc 3.4 and later.
 439#
 440config SPARSEMEM_STATIC
 441	bool
 442
 443#
 444# Architecture platforms which require a two level mem_section in SPARSEMEM
 445# must select this option. This is usually for architecture platforms with
 446# an extremely sparse physical address space.
 447#
 448config SPARSEMEM_EXTREME
 449	def_bool y
 450	depends on SPARSEMEM && !SPARSEMEM_STATIC
 451
 452config SPARSEMEM_VMEMMAP_ENABLE
 453	bool
 454
 455config SPARSEMEM_VMEMMAP
 456	bool "Sparse Memory virtual memmap"
 457	depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
 458	default y
 459	help
 460	  SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
 461	  pfn_to_page and page_to_pfn operations.  This is the most
 462	  efficient option when sufficient kernel resources are available.
 463
 464config HAVE_MEMBLOCK_PHYS_MAP
 465	bool
 466
 467config HAVE_FAST_GUP
 468	depends on MMU
 469	bool
 470
 471# Don't discard allocated memory used to track "memory" and "reserved" memblocks
 472# after early boot, so it can still be used to test for validity of memory.
 473# Also, memblocks are updated with memory hot(un)plug.
 474config ARCH_KEEP_MEMBLOCK
 475	bool
 476
 477# Keep arch NUMA mapping infrastructure post-init.
 478config NUMA_KEEP_MEMINFO
 479	bool
 480
 481config MEMORY_ISOLATION
 482	bool
 483
 484# IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked
 485# IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via
 486# /dev/mem.
 487config EXCLUSIVE_SYSTEM_RAM
 488	def_bool y
 489	depends on !DEVMEM || STRICT_DEVMEM
 490
 491#
 492# Only be set on architectures that have completely implemented memory hotplug
 493# feature. If you are not sure, don't touch it.
 494#
 495config HAVE_BOOTMEM_INFO_NODE
 496	def_bool n
 497
 498config ARCH_ENABLE_MEMORY_HOTPLUG
 499	bool
 500
 501config ARCH_ENABLE_MEMORY_HOTREMOVE
 502	bool
 503
 504# eventually, we can have this option just 'select SPARSEMEM'
 505menuconfig MEMORY_HOTPLUG
 506	bool "Memory hotplug"
 507	select MEMORY_ISOLATION
 508	depends on SPARSEMEM
 509	depends on ARCH_ENABLE_MEMORY_HOTPLUG
 510	depends on 64BIT
 511	select NUMA_KEEP_MEMINFO if NUMA
 512
 513if MEMORY_HOTPLUG
 
 
 514
 515config MEMORY_HOTPLUG_DEFAULT_ONLINE
 516	bool "Online the newly added memory blocks by default"
 517	depends on MEMORY_HOTPLUG
 518	help
 519	  This option sets the default policy setting for memory hotplug
 520	  onlining policy (/sys/devices/system/memory/auto_online_blocks) which
 521	  determines what happens to newly added memory regions. Policy setting
 522	  can always be changed at runtime.
 523	  See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
 524
 525	  Say Y here if you want all hot-plugged memory blocks to appear in
 526	  'online' state by default.
 527	  Say N here if you want the default policy to keep all hot-plugged
 528	  memory blocks in 'offline' state.
 529
 530config MEMORY_HOTREMOVE
 531	bool "Allow for memory hot remove"
 
 532	select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
 533	depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 534	depends on MIGRATION
 535
 536config MHP_MEMMAP_ON_MEMORY
 537	def_bool y
 538	depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
 539	depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
 540
 541endif # MEMORY_HOTPLUG
 542
 543# Heavily threaded applications may benefit from splitting the mm-wide
 544# page_table_lock, so that faults on different parts of the user address
 545# space can be handled with less contention: split it at this NR_CPUS.
 546# Default to 4 for wider testing, though 8 might be more appropriate.
 547# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 548# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 549# SPARC32 allocates multiple pte tables within a single page, and therefore
 550# a per-page lock leads to problems when multiple tables need to be locked
 551# at the same time (e.g. copy_page_range()).
 552# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
 553#
 554config SPLIT_PTLOCK_CPUS
 555	int
 556	default "999999" if !MMU
 557	default "999999" if ARM && !CPU_CACHE_VIPT
 558	default "999999" if PARISC && !PA20
 559	default "999999" if SPARC32
 560	default "4"
 561
 562config ARCH_ENABLE_SPLIT_PMD_PTLOCK
 563	bool
 564
 565#
 566# support for memory balloon
 567config MEMORY_BALLOON
 568	bool
 569
 570#
 571# support for memory balloon compaction
 572config BALLOON_COMPACTION
 573	bool "Allow for balloon memory compaction/migration"
 574	def_bool y
 575	depends on COMPACTION && MEMORY_BALLOON
 576	help
 577	  Memory fragmentation introduced by ballooning might reduce
 578	  significantly the number of 2MB contiguous memory blocks that can be
 579	  used within a guest, thus imposing performance penalties associated
 580	  with the reduced number of transparent huge pages that could be used
 581	  by the guest workload. Allowing the compaction & migration for memory
 582	  pages enlisted as being part of memory balloon devices avoids the
 583	  scenario aforementioned and helps improving memory defragmentation.
 584
 585#
 586# support for memory compaction
 587config COMPACTION
 588	bool "Allow for memory compaction"
 589	def_bool y
 590	select MIGRATION
 591	depends on MMU
 592	help
 593	  Compaction is the only memory management component to form
 594	  high order (larger physically contiguous) memory blocks
 595	  reliably. The page allocator relies on compaction heavily and
 596	  the lack of the feature can lead to unexpected OOM killer
 597	  invocations for high order memory requests. You shouldn't
 598	  disable this option unless there really is a strong reason for
 599	  it and then we would be really interested to hear about that at
 600	  linux-mm@kvack.org.
 601
 602config COMPACT_UNEVICTABLE_DEFAULT
 603	int
 604	depends on COMPACTION
 605	default 0 if PREEMPT_RT
 606	default 1
 607
 608#
 609# support for free page reporting
 610config PAGE_REPORTING
 611	bool "Free page reporting"
 612	def_bool n
 613	help
 614	  Free page reporting allows for the incremental acquisition of
 615	  free pages from the buddy allocator for the purpose of reporting
 616	  those pages to another entity, such as a hypervisor, so that the
 617	  memory can be freed within the host for other uses.
 618
 619#
 620# support for page migration
 621#
 622config MIGRATION
 623	bool "Page migration"
 624	def_bool y
 625	depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
 626	help
 627	  Allows the migration of the physical location of pages of processes
 628	  while the virtual addresses are not changed. This is useful in
 629	  two situations. The first is on NUMA systems to put pages nearer
 630	  to the processors accessing. The second is when allocating huge
 631	  pages as migration can relocate pages to satisfy a huge page
 632	  allocation instead of reclaiming.
 633
 634config DEVICE_MIGRATION
 635	def_bool MIGRATION && ZONE_DEVICE
 636
 637config ARCH_ENABLE_HUGEPAGE_MIGRATION
 638	bool
 639
 640config ARCH_ENABLE_THP_MIGRATION
 641	bool
 642
 643config HUGETLB_PAGE_SIZE_VARIABLE
 644	def_bool n
 645	help
 646	  Allows the pageblock_order value to be dynamic instead of just standard
 647	  HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available
 648	  on a platform.
 649
 650	  Note that the pageblock_order cannot exceed MAX_ORDER - 1 and will be
 651	  clamped down to MAX_ORDER - 1.
 652
 653config CONTIG_ALLOC
 654	def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
 655
 656config PHYS_ADDR_T_64BIT
 657	def_bool 64BIT
 658
 659config BOUNCE
 660	bool "Enable bounce buffers"
 661	default y
 662	depends on BLOCK && MMU && HIGHMEM
 663	help
 664	  Enable bounce buffers for devices that cannot access the full range of
 665	  memory available to the CPU. Enabled by default when HIGHMEM is
 666	  selected, but you may say n to override this.
 
 
 
 
 
 
 
 
 
 667
 668config MMU_NOTIFIER
 669	bool
 670	select SRCU
 671	select INTERVAL_TREE
 672
 673config KSM
 674	bool "Enable KSM for page merging"
 675	depends on MMU
 676	select XXHASH
 677	help
 678	  Enable Kernel Samepage Merging: KSM periodically scans those areas
 679	  of an application's address space that an app has advised may be
 680	  mergeable.  When it finds pages of identical content, it replaces
 681	  the many instances by a single page with that content, so
 682	  saving memory until one or another app needs to modify the content.
 683	  Recommended for use with KVM, or with other duplicative applications.
 684	  See Documentation/mm/ksm.rst for more information: KSM is inactive
 685	  until a program has madvised that an area is MADV_MERGEABLE, and
 686	  root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 687
 688config DEFAULT_MMAP_MIN_ADDR
 689	int "Low address space to protect from user allocation"
 690	depends on MMU
 691	default 4096
 692	help
 693	  This is the portion of low virtual memory which should be protected
 694	  from userspace allocation.  Keeping a user from writing to low pages
 695	  can help reduce the impact of kernel NULL pointer bugs.
 696
 697	  For most ia64, ppc64 and x86 users with lots of address space
 698	  a value of 65536 is reasonable and should cause no problems.
 699	  On arm and other archs it should not be higher than 32768.
 700	  Programs which use vm86 functionality or have some need to map
 701	  this low address space will need CAP_SYS_RAWIO or disable this
 702	  protection by setting the value to 0.
 703
 704	  This value can be changed after boot using the
 705	  /proc/sys/vm/mmap_min_addr tunable.
 706
 707config ARCH_SUPPORTS_MEMORY_FAILURE
 708	bool
 709
 710config MEMORY_FAILURE
 711	depends on MMU
 712	depends on ARCH_SUPPORTS_MEMORY_FAILURE
 713	bool "Enable recovery from hardware memory errors"
 714	select MEMORY_ISOLATION
 715	select RAS
 716	help
 717	  Enables code to recover from some memory failures on systems
 718	  with MCA recovery. This allows a system to continue running
 719	  even when some of its memory has uncorrected errors. This requires
 720	  special hardware support and typically ECC memory.
 721
 722config HWPOISON_INJECT
 723	tristate "HWPoison pages injector"
 724	depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 725	select PROC_PAGE_MONITOR
 726
 727config NOMMU_INITIAL_TRIM_EXCESS
 728	int "Turn on mmap() excess space trimming before booting"
 729	depends on !MMU
 730	default 1
 731	help
 732	  The NOMMU mmap() frequently needs to allocate large contiguous chunks
 733	  of memory on which to store mappings, but it can only ask the system
 734	  allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 735	  more than it requires.  To deal with this, mmap() is able to trim off
 736	  the excess and return it to the allocator.
 737
 738	  If trimming is enabled, the excess is trimmed off and returned to the
 739	  system allocator, which can cause extra fragmentation, particularly
 740	  if there are a lot of transient processes.
 741
 742	  If trimming is disabled, the excess is kept, but not used, which for
 743	  long-term mappings means that the space is wasted.
 744
 745	  Trimming can be dynamically controlled through a sysctl option
 746	  (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 747	  excess pages there must be before trimming should occur, or zero if
 748	  no trimming is to occur.
 749
 750	  This option specifies the initial value of this option.  The default
 751	  of 1 says that all excess pages should be trimmed.
 752
 753	  See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
 754
 755config ARCH_WANT_GENERAL_HUGETLB
 756	bool
 757
 758config ARCH_WANTS_THP_SWAP
 759	def_bool n
 760
 761menuconfig TRANSPARENT_HUGEPAGE
 762	bool "Transparent Hugepage Support"
 763	depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT
 764	select COMPACTION
 765	select XARRAY_MULTI
 766	help
 767	  Transparent Hugepages allows the kernel to use huge pages and
 768	  huge tlb transparently to the applications whenever possible.
 769	  This feature can improve computing performance to certain
 770	  applications by speeding up page faults during memory
 771	  allocation, by reducing the number of tlb misses and by speeding
 772	  up the pagetable walking.
 773
 774	  If memory constrained on embedded, you may want to say N.
 775
 776if TRANSPARENT_HUGEPAGE
 777
 778choice
 779	prompt "Transparent Hugepage Support sysfs defaults"
 780	depends on TRANSPARENT_HUGEPAGE
 781	default TRANSPARENT_HUGEPAGE_ALWAYS
 782	help
 783	  Selects the sysfs defaults for Transparent Hugepage Support.
 784
 785	config TRANSPARENT_HUGEPAGE_ALWAYS
 786		bool "always"
 787	help
 788	  Enabling Transparent Hugepage always, can increase the
 789	  memory footprint of applications without a guaranteed
 790	  benefit but it will work automatically for all applications.
 791
 792	config TRANSPARENT_HUGEPAGE_MADVISE
 793		bool "madvise"
 794	help
 795	  Enabling Transparent Hugepage madvise, will only provide a
 796	  performance improvement benefit to the applications using
 797	  madvise(MADV_HUGEPAGE) but it won't risk to increase the
 798	  memory footprint of applications without a guaranteed
 799	  benefit.
 800endchoice
 801
 
 
 
 802config THP_SWAP
 803	def_bool y
 804	depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT
 805	help
 806	  Swap transparent huge pages in one piece, without splitting.
 807	  XXX: For now, swap cluster backing transparent huge page
 808	  will be split after swapout.
 809
 810	  For selection by architectures with reasonable THP sizes.
 811
 812config READ_ONLY_THP_FOR_FS
 813	bool "Read-only THP for filesystems (EXPERIMENTAL)"
 814	depends on TRANSPARENT_HUGEPAGE && SHMEM
 815
 816	help
 817	  Allow khugepaged to put read-only file-backed pages in THP.
 818
 819	  This is marked experimental because it is a new feature. Write
 820	  support of file THPs will be developed in the next few release
 821	  cycles.
 822
 823endif # TRANSPARENT_HUGEPAGE
 824
 825#
 826# UP and nommu archs use km based percpu allocator
 827#
 828config NEED_PER_CPU_KM
 829	depends on !SMP || !MMU
 830	bool
 831	default y
 832
 833config NEED_PER_CPU_EMBED_FIRST_CHUNK
 834	bool
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 835
 836config NEED_PER_CPU_PAGE_FIRST_CHUNK
 837	bool
 838
 839config USE_PERCPU_NUMA_NODE_ID
 840	bool
 
 
 
 
 
 
 
 
 
 
 
 841
 842config HAVE_SETUP_PER_CPU_AREA
 843	bool
 844
 845config FRONTSWAP
 846	bool
 847
 848config CMA
 849	bool "Contiguous Memory Allocator"
 850	depends on MMU
 851	select MIGRATION
 852	select MEMORY_ISOLATION
 853	help
 854	  This enables the Contiguous Memory Allocator which allows other
 855	  subsystems to allocate big physically-contiguous blocks of memory.
 856	  CMA reserves a region of memory and allows only movable pages to
 857	  be allocated from it. This way, the kernel can use the memory for
 858	  pagecache and when a subsystem requests for contiguous area, the
 859	  allocated pages are migrated away to serve the contiguous request.
 860
 861	  If unsure, say "n".
 862
 863config CMA_DEBUG
 864	bool "CMA debug messages (DEVELOPMENT)"
 865	depends on DEBUG_KERNEL && CMA
 866	help
 867	  Turns on debug messages in CMA.  This produces KERN_DEBUG
 868	  messages for every CMA call as well as various messages while
 869	  processing calls such as dma_alloc_from_contiguous().
 870	  This option does not affect warning and error messages.
 871
 872config CMA_DEBUGFS
 873	bool "CMA debugfs interface"
 874	depends on CMA && DEBUG_FS
 875	help
 876	  Turns on the DebugFS interface for CMA.
 877
 878config CMA_SYSFS
 879	bool "CMA information through sysfs interface"
 880	depends on CMA && SYSFS
 881	help
 882	  This option exposes some sysfs attributes to get information
 883	  from CMA.
 884
 885config CMA_AREAS
 886	int "Maximum count of the CMA areas"
 887	depends on CMA
 888	default 19 if NUMA
 889	default 7
 890	help
 891	  CMA allows to create CMA areas for particular purpose, mainly,
 892	  used as device private area. This parameter sets the maximum
 893	  number of CMA area in the system.
 894
 895	  If unsure, leave the default value "7" in UMA and "19" in NUMA.
 896
 897config MEM_SOFT_DIRTY
 898	bool "Track memory changes"
 899	depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
 900	select PROC_PAGE_MONITOR
 901	help
 902	  This option enables memory changes tracking by introducing a
 903	  soft-dirty bit on pte-s. This bit it set when someone writes
 904	  into a page just as regular dirty bit, but unlike the latter
 905	  it can be cleared by hands.
 906
 907	  See Documentation/admin-guide/mm/soft-dirty.rst for more details.
 908
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 909config GENERIC_EARLY_IOREMAP
 910	bool
 911
 912config STACK_MAX_DEFAULT_SIZE_MB
 913	int "Default maximum user stack size for 32-bit processes (MB)"
 914	default 100
 915	range 8 2048
 916	depends on STACK_GROWSUP && (!64BIT || COMPAT)
 917	help
 918	  This is the maximum stack size in Megabytes in the VM layout of 32-bit
 919	  user processes when the stack grows upwards (currently only on parisc
 920	  arch) when the RLIMIT_STACK hard limit is unlimited.
 
 
 921
 922	  A sane initial value is 100 MB.
 923
 924config DEFERRED_STRUCT_PAGE_INIT
 925	bool "Defer initialisation of struct pages to kthreads"
 926	depends on SPARSEMEM
 927	depends on !NEED_PER_CPU_KM
 928	depends on 64BIT
 929	select PADATA
 930	help
 931	  Ordinarily all struct pages are initialised during early boot in a
 932	  single thread. On very large machines this can take a considerable
 933	  amount of time. If this option is set, large machines will bring up
 934	  a subset of memmap at boot and then initialise the rest in parallel.
 935	  This has a potential performance impact on tasks running early in the
 936	  lifetime of the system until these kthreads finish the
 937	  initialisation.
 938
 939config PAGE_IDLE_FLAG
 940	bool
 941	select PAGE_EXTENSION if !64BIT
 942	help
 943	  This adds PG_idle and PG_young flags to 'struct page'.  PTE Accessed
 944	  bit writers can set the state of the bit in the flags so that PTE
 945	  Accessed bit readers may avoid disturbance.
 946
 947config IDLE_PAGE_TRACKING
 948	bool "Enable idle page tracking"
 949	depends on SYSFS && MMU
 950	select PAGE_IDLE_FLAG
 951	help
 952	  This feature allows to estimate the amount of user pages that have
 953	  not been touched during a given period of time. This information can
 954	  be useful to tune memory cgroup limits and/or for job placement
 955	  within a compute cluster.
 956
 957	  See Documentation/admin-guide/mm/idle_page_tracking.rst for
 958	  more details.
 959
 960config ARCH_HAS_CACHE_LINE_SIZE
 961	bool
 962
 963config ARCH_HAS_CURRENT_STACK_POINTER
 964	bool
 965	help
 966	  In support of HARDENED_USERCOPY performing stack variable lifetime
 967	  checking, an architecture-agnostic way to find the stack pointer
 968	  is needed. Once an architecture defines an unsigned long global
 969	  register alias named "current_stack_pointer", this config can be
 970	  selected.
 971
 972config ARCH_HAS_PTE_DEVMAP
 973	bool
 974
 975config ARCH_HAS_ZONE_DMA_SET
 976	bool
 977
 978config ZONE_DMA
 979	bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET
 980	default y if ARM64 || X86
 981
 982config ZONE_DMA32
 983	bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET
 984	depends on !X86_32
 985	default y if ARM64
 986
 987config ZONE_DEVICE
 988	bool "Device memory (pmem, HMM, etc...) hotplug support"
 989	depends on MEMORY_HOTPLUG
 990	depends on MEMORY_HOTREMOVE
 991	depends on SPARSEMEM_VMEMMAP
 992	depends on ARCH_HAS_PTE_DEVMAP
 993	select XARRAY_MULTI
 994
 995	help
 996	  Device memory hotplug support allows for establishing pmem,
 997	  or other device driver discovered memory regions, in the
 998	  memmap. This allows pfn_to_page() lookups of otherwise
 999	  "device-physical" addresses which is needed for using a DAX
1000	  mapping in an O_DIRECT operation, among other things.
1001
1002	  If FS_DAX is enabled, then say Y.
1003
 
 
 
1004#
1005# Helpers to mirror range of the CPU page tables of a process into device page
1006# tables.
1007#
1008config HMM_MIRROR
1009	bool
1010	depends on MMU
1011
1012config GET_FREE_REGION
1013	depends on SPARSEMEM
1014	bool
1015
1016config DEVICE_PRIVATE
1017	bool "Unaddressable device memory (GPU memory, ...)"
1018	depends on ZONE_DEVICE
1019	select GET_FREE_REGION
1020
1021	help
1022	  Allows creation of struct pages to represent unaddressable device
1023	  memory; i.e., memory that is only accessible from the device (or
1024	  group of devices). You likely also want to select HMM_MIRROR.
1025
1026config VMAP_PFN
1027	bool
1028
1029config ARCH_USES_HIGH_VMA_FLAGS
1030	bool
1031config ARCH_HAS_PKEYS
1032	bool
1033
1034config ARCH_USES_PG_ARCH_X
1035	bool
1036	help
1037	  Enable the definition of PG_arch_x page flags with x > 1. Only
1038	  suitable for 64-bit architectures with CONFIG_FLATMEM or
1039	  CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be
1040	  enough room for additional bits in page->flags.
1041
1042config VM_EVENT_COUNTERS
1043	default y
1044	bool "Enable VM event counters for /proc/vmstat" if EXPERT
1045	help
1046	  VM event counters are needed for event counts to be shown.
1047	  This option allows the disabling of the VM event counters
1048	  on EXPERT systems.  /proc/vmstat will only show page counts
1049	  if VM event counters are disabled.
1050
1051config PERCPU_STATS
1052	bool "Collect percpu memory statistics"
1053	help
1054	  This feature collects and exposes statistics via debugfs. The
1055	  information includes global and per chunk statistics, which can
1056	  be used to help understand percpu memory usage.
1057
1058config GUP_TEST
1059	bool "Enable infrastructure for get_user_pages()-related unit tests"
1060	depends on DEBUG_FS
1061	help
1062	  Provides /sys/kernel/debug/gup_test, which in turn provides a way
1063	  to make ioctl calls that can launch kernel-based unit tests for
1064	  the get_user_pages*() and pin_user_pages*() family of API calls.
1065
1066	  These tests include benchmark testing of the _fast variants of
1067	  get_user_pages*() and pin_user_pages*(), as well as smoke tests of
1068	  the non-_fast variants.
1069
1070	  There is also a sub-test that allows running dump_page() on any
1071	  of up to eight pages (selected by command line args) within the
1072	  range of user-space addresses. These pages are either pinned via
1073	  pin_user_pages*(), or pinned via get_user_pages*(), as specified
1074	  by other command line arguments.
1075
1076	  See tools/testing/selftests/vm/gup_test.c
1077
1078comment "GUP_TEST needs to have DEBUG_FS enabled"
1079	depends on !GUP_TEST && !DEBUG_FS
1080
1081config GUP_GET_PXX_LOW_HIGH
1082	bool
 
 
 
 
 
 
 
 
1083
1084config ARCH_HAS_PTE_SPECIAL
1085	bool
1086
1087#
1088# Some architectures require a special hugepage directory format that is
1089# required to support multiple hugepage sizes. For example a4fe3ce76
1090# "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
1091# introduced it on powerpc.  This allows for a more flexible hugepage
1092# pagetable layouts.
1093#
1094config ARCH_HAS_HUGEPD
1095	bool
1096
1097config MAPPING_DIRTY_HELPERS
1098        bool
1099
1100config KMAP_LOCAL
1101	bool
1102
1103config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY
1104	bool
1105
1106# struct io_mapping based helper.  Selected by drivers that need them
1107config IO_MAPPING
1108	bool
1109
1110config SECRETMEM
1111	default y
1112	bool "Enable memfd_secret() system call" if EXPERT
1113	depends on ARCH_HAS_SET_DIRECT_MAP
1114	help
1115	  Enable the memfd_secret() system call with the ability to create
1116	  memory areas visible only in the context of the owning process and
1117	  not mapped to other processes and other kernel page tables.
1118
1119config ANON_VMA_NAME
1120	bool "Anonymous VMA name support"
1121	depends on PROC_FS && ADVISE_SYSCALLS && MMU
1122
1123	help
1124	  Allow naming anonymous virtual memory areas.
1125
1126	  This feature allows assigning names to virtual memory areas. Assigned
1127	  names can be later retrieved from /proc/pid/maps and /proc/pid/smaps
1128	  and help identifying individual anonymous memory areas.
1129	  Assigning a name to anonymous virtual memory area might prevent that
1130	  area from being merged with adjacent virtual memory areas due to the
1131	  difference in their name.
1132
1133config USERFAULTFD
1134	bool "Enable userfaultfd() system call"
1135	depends on MMU
1136	help
1137	  Enable the userfaultfd() system call that allows to intercept and
1138	  handle page faults in userland.
1139
1140config HAVE_ARCH_USERFAULTFD_WP
1141	bool
1142	help
1143	  Arch has userfaultfd write protection support
1144
1145config HAVE_ARCH_USERFAULTFD_MINOR
1146	bool
1147	help
1148	  Arch has userfaultfd minor fault support
1149
1150config PTE_MARKER_UFFD_WP
1151	bool "Userfaultfd write protection support for shmem/hugetlbfs"
1152	default y
1153	depends on HAVE_ARCH_USERFAULTFD_WP
1154
1155	help
1156	  Allows to create marker PTEs for userfaultfd write protection
1157	  purposes.  It is required to enable userfaultfd write protection on
1158	  file-backed memory types like shmem and hugetlbfs.
1159
1160# multi-gen LRU {
1161config LRU_GEN
1162	bool "Multi-Gen LRU"
1163	depends on MMU
1164	# make sure folio->flags has enough spare bits
1165	depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP
1166	help
1167	  A high performance LRU implementation to overcommit memory. See
1168	  Documentation/admin-guide/mm/multigen_lru.rst for details.
1169
1170config LRU_GEN_ENABLED
1171	bool "Enable by default"
1172	depends on LRU_GEN
1173	help
1174	  This option enables the multi-gen LRU by default.
1175
1176config LRU_GEN_STATS
1177	bool "Full stats for debugging"
1178	depends on LRU_GEN
1179	help
1180	  Do not enable this option unless you plan to look at historical stats
1181	  from evicted generations for debugging purpose.
1182
1183	  This option has a per-memcg and per-node memory overhead.
1184# }
1185
1186source "mm/damon/Kconfig"
1187
1188endmenu