]> git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blame - mm/Kconfig
vfs: pull btrfs clone API to vfs layer
[mirror_ubuntu-bionic-kernel.git] / mm / Kconfig
CommitLineData
e1785e85
DH
1config SELECT_MEMORY_MODEL
2 def_bool y
a8826eeb 3 depends on ARCH_SELECT_MEMORY_MODEL
e1785e85 4
3a9da765
DH
5choice
6 prompt "Memory model"
e1785e85
DH
7 depends on SELECT_MEMORY_MODEL
8 default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
d41dee36 9 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
e1785e85 10 default FLATMEM_MANUAL
3a9da765 11
e1785e85 12config FLATMEM_MANUAL
3a9da765 13 bool "Flat Memory"
c898ec16 14 depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
3a9da765
DH
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
d41dee36
AW
21 Some users of more advanced features like NUMA and
22 memory hotplug may have different options here.
18f65332 23 DISCONTIGMEM is a more mature, better tested system,
d41dee36
AW
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.
3a9da765 30
e1785e85 31config DISCONTIGMEM_MANUAL
f3519f91 32 bool "Discontiguous Memory"
3a9da765
DH
33 depends on ARCH_DISCONTIGMEM_ENABLE
34 help
785dcd44
DH
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
ad3d0a38 40 can have degraded performance from the extra overhead that
785dcd44
DH
41 this option imposes.
42
43 Many NUMA configurations will have this as the only option.
44
3a9da765
DH
45 If unsure, choose "Flat Memory" over this option.
46
d41dee36
AW
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
f3519f91 55 "Discontiguous Memory". This option provides some potential
d41dee36
AW
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
3a9da765
DH
62endchoice
63
e1785e85
DH
64config DISCONTIGMEM
65 def_bool y
66 depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
67
d41dee36
AW
68config SPARSEMEM
69 def_bool y
1a83e175 70 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
d41dee36 71
e1785e85
DH
72config FLATMEM
73 def_bool y
d41dee36
AW
74 depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
75
76config FLAT_NODE_MEM_MAP
77 def_bool y
78 depends on !SPARSEMEM
e1785e85 79
93b7504e
DH
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
af705362
AW
88
89config HAVE_MEMORY_PRESENT
90 def_bool y
d41dee36 91 depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
802f192e 92
3e347261
BP
93#
94# SPARSEMEM_EXTREME (which is the default) does some bootmem
84eb8d06 95# allocations when memory_present() is called. If this cannot
3e347261
BP
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
9ba16087 104 bool
3e347261 105
802f192e 106#
44c09201 107# Architecture platforms which require a two level mem_section in SPARSEMEM
802f192e
BP
108# must select this option. This is usually for architecture platforms with
109# an extremely sparse physical address space.
110#
3e347261
BP
111config SPARSEMEM_EXTREME
112 def_bool y
113 depends on SPARSEMEM && !SPARSEMEM_STATIC
4c21e2f2 114
29c71111 115config SPARSEMEM_VMEMMAP_ENABLE
9ba16087 116 bool
29c71111 117
9bdac914
YL
118config SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
119 def_bool y
120 depends on SPARSEMEM && X86_64
121
29c71111 122config SPARSEMEM_VMEMMAP
a5ee6daa
GL
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.
29c71111 130
95f72d1e 131config HAVE_MEMBLOCK
6341e62b 132 bool
95f72d1e 133
7c0caeb8 134config HAVE_MEMBLOCK_NODE_MAP
6341e62b 135 bool
7c0caeb8 136
70210ed9 137config HAVE_MEMBLOCK_PHYS_MAP
6341e62b 138 bool
70210ed9 139
2667f50e 140config HAVE_GENERIC_RCU_GUP
6341e62b 141 bool
2667f50e 142
c378ddd5 143config ARCH_DISCARD_MEMBLOCK
6341e62b 144 bool
c378ddd5 145
66616720 146config NO_BOOTMEM
6341e62b 147 bool
66616720 148
ee6f509c 149config MEMORY_ISOLATION
6341e62b 150 bool
ee6f509c 151
20b2f52b 152config MOVABLE_NODE
6341e62b 153 bool "Enable to assign a node which has only movable memory"
20b2f52b
LJ
154 depends on HAVE_MEMBLOCK
155 depends on NO_BOOTMEM
156 depends on X86_64
157 depends on NUMA
c2974058
TC
158 default n
159 help
160 Allow a node to have only movable memory. Pages used by the kernel,
161 such as direct mapping pages cannot be migrated. So the corresponding
c5320926
TC
162 memory device cannot be hotplugged. This option allows the following
163 two things:
164 - When the system is booting, node full of hotpluggable memory can
165 be arranged to have only movable memory so that the whole node can
166 be hot-removed. (need movable_node boot option specified).
167 - After the system is up, the option allows users to online all the
168 memory of a node as movable memory so that the whole node can be
169 hot-removed.
170
171 Users who don't use the memory hotplug feature are fine with this
172 option on since they don't specify movable_node boot option or they
173 don't online memory as movable.
c2974058
TC
174
175 Say Y here if you want to hotplug a whole node.
176 Say N here if you want kernel to use memory on all nodes evenly.
20b2f52b 177
46723bfa
YI
178#
179# Only be set on architectures that have completely implemented memory hotplug
180# feature. If you are not sure, don't touch it.
181#
182config HAVE_BOOTMEM_INFO_NODE
183 def_bool n
184
3947be19
DH
185# eventually, we can have this option just 'select SPARSEMEM'
186config MEMORY_HOTPLUG
187 bool "Allow for memory hot-add"
ec69acbb 188 depends on SPARSEMEM || X86_64_ACPI_NUMA
40b31360 189 depends on ARCH_ENABLE_MEMORY_HOTPLUG
ed84a07a 190 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
3947be19 191
ec69acbb
KM
192config MEMORY_HOTPLUG_SPARSE
193 def_bool y
194 depends on SPARSEMEM && MEMORY_HOTPLUG
195
0c0e6195
KH
196config MEMORY_HOTREMOVE
197 bool "Allow for memory hot remove"
46723bfa 198 select MEMORY_ISOLATION
f7e3334a 199 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
0c0e6195
KH
200 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
201 depends on MIGRATION
202
4c21e2f2
HD
203# Heavily threaded applications may benefit from splitting the mm-wide
204# page_table_lock, so that faults on different parts of the user address
205# space can be handled with less contention: split it at this NR_CPUS.
206# Default to 4 for wider testing, though 8 might be more appropriate.
207# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
7b6ac9df 208# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
a70caa8b 209# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
4c21e2f2
HD
210#
211config SPLIT_PTLOCK_CPUS
212 int
9164550e 213 default "999999" if !MMU
a70caa8b
HD
214 default "999999" if ARM && !CPU_CACHE_VIPT
215 default "999999" if PARISC && !PA20
4c21e2f2 216 default "4"
7cbe34cf 217
e009bb30 218config ARCH_ENABLE_SPLIT_PMD_PTLOCK
6341e62b 219 bool
e009bb30 220
09316c09
KK
221#
222# support for memory balloon
223config MEMORY_BALLOON
6341e62b 224 bool
09316c09 225
18468d93
RA
226#
227# support for memory balloon compaction
228config BALLOON_COMPACTION
229 bool "Allow for balloon memory compaction/migration"
230 def_bool y
09316c09 231 depends on COMPACTION && MEMORY_BALLOON
18468d93
RA
232 help
233 Memory fragmentation introduced by ballooning might reduce
234 significantly the number of 2MB contiguous memory blocks that can be
235 used within a guest, thus imposing performance penalties associated
236 with the reduced number of transparent huge pages that could be used
237 by the guest workload. Allowing the compaction & migration for memory
238 pages enlisted as being part of memory balloon devices avoids the
239 scenario aforementioned and helps improving memory defragmentation.
240
e9e96b39
MG
241#
242# support for memory compaction
243config COMPACTION
244 bool "Allow for memory compaction"
05106e6a 245 def_bool y
e9e96b39 246 select MIGRATION
33a93877 247 depends on MMU
e9e96b39
MG
248 help
249 Allows the compaction of memory for the allocation of huge pages.
250
7cbe34cf
CL
251#
252# support for page migration
253#
254config MIGRATION
b20a3503 255 bool "Page migration"
6c5240ae 256 def_bool y
de32a817 257 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
b20a3503
CL
258 help
259 Allows the migration of the physical location of pages of processes
e9e96b39
MG
260 while the virtual addresses are not changed. This is useful in
261 two situations. The first is on NUMA systems to put pages nearer
262 to the processors accessing. The second is when allocating huge
263 pages as migration can relocate pages to satisfy a huge page
264 allocation instead of reclaiming.
6550e07f 265
c177c81e 266config ARCH_ENABLE_HUGEPAGE_MIGRATION
6341e62b 267 bool
c177c81e 268
600715dc
JF
269config PHYS_ADDR_T_64BIT
270 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
271
4b51d669
CL
272config ZONE_DMA_FLAG
273 int
274 default "0" if !ZONE_DMA
275 default "1"
276
2a7326b5 277config BOUNCE
9ca24e2e
VM
278 bool "Enable bounce buffers"
279 default y
2a7326b5 280 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
9ca24e2e
VM
281 help
282 Enable bounce buffers for devices that cannot access
283 the full range of memory available to the CPU. Enabled
284 by default when ZONE_DMA or HIGHMEM is selected, but you
285 may say n to override this.
2a7326b5 286
ffecfd1a
DW
287# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
288# have more than 4GB of memory, but we don't currently use the IOTLB to present
289# a 32-bit address to OHCI. So we need to use a bounce pool instead.
ffecfd1a
DW
290config NEED_BOUNCE_POOL
291 bool
debeb297 292 default y if TILE && USB_OHCI_HCD
ffecfd1a 293
6225e937
CL
294config NR_QUICK
295 int
296 depends on QUICKLIST
0176bd3d 297 default "2" if AVR32
6225e937 298 default "1"
f057eac0
SR
299
300config VIRT_TO_BUS
4febd95a
SR
301 bool
302 help
303 An architecture should select this if it implements the
304 deprecated interface virt_to_bus(). All new architectures
305 should probably not select this.
306
cddb8a5c
AA
307
308config MMU_NOTIFIER
309 bool
83fe27ea 310 select SRCU
fc4d5c29 311
f8af4da3
HD
312config KSM
313 bool "Enable KSM for page merging"
314 depends on MMU
315 help
316 Enable Kernel Samepage Merging: KSM periodically scans those areas
317 of an application's address space that an app has advised may be
318 mergeable. When it finds pages of identical content, it replaces
d0f209f6 319 the many instances by a single page with that content, so
f8af4da3
HD
320 saving memory until one or another app needs to modify the content.
321 Recommended for use with KVM, or with other duplicative applications.
c73602ad
HD
322 See Documentation/vm/ksm.txt for more information: KSM is inactive
323 until a program has madvised that an area is MADV_MERGEABLE, and
324 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
f8af4da3 325
e0a94c2a
CL
326config DEFAULT_MMAP_MIN_ADDR
327 int "Low address space to protect from user allocation"
6e141546 328 depends on MMU
e0a94c2a
CL
329 default 4096
330 help
331 This is the portion of low virtual memory which should be protected
332 from userspace allocation. Keeping a user from writing to low pages
333 can help reduce the impact of kernel NULL pointer bugs.
334
335 For most ia64, ppc64 and x86 users with lots of address space
336 a value of 65536 is reasonable and should cause no problems.
337 On arm and other archs it should not be higher than 32768.
788084ab
EP
338 Programs which use vm86 functionality or have some need to map
339 this low address space will need CAP_SYS_RAWIO or disable this
340 protection by setting the value to 0.
e0a94c2a
CL
341
342 This value can be changed after boot using the
343 /proc/sys/vm/mmap_min_addr tunable.
344
d949f36f
LT
345config ARCH_SUPPORTS_MEMORY_FAILURE
346 bool
e0a94c2a 347
6a46079c
AK
348config MEMORY_FAILURE
349 depends on MMU
d949f36f 350 depends on ARCH_SUPPORTS_MEMORY_FAILURE
6a46079c 351 bool "Enable recovery from hardware memory errors"
ee6f509c 352 select MEMORY_ISOLATION
97f0b134 353 select RAS
6a46079c
AK
354 help
355 Enables code to recover from some memory failures on systems
356 with MCA recovery. This allows a system to continue running
357 even when some of its memory has uncorrected errors. This requires
358 special hardware support and typically ECC memory.
359
cae681fc 360config HWPOISON_INJECT
413f9efb 361 tristate "HWPoison pages injector"
27df5068 362 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
478c5ffc 363 select PROC_PAGE_MONITOR
cae681fc 364
fc4d5c29
DH
365config NOMMU_INITIAL_TRIM_EXCESS
366 int "Turn on mmap() excess space trimming before booting"
367 depends on !MMU
368 default 1
369 help
370 The NOMMU mmap() frequently needs to allocate large contiguous chunks
371 of memory on which to store mappings, but it can only ask the system
372 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
373 more than it requires. To deal with this, mmap() is able to trim off
374 the excess and return it to the allocator.
375
376 If trimming is enabled, the excess is trimmed off and returned to the
377 system allocator, which can cause extra fragmentation, particularly
378 if there are a lot of transient processes.
379
380 If trimming is disabled, the excess is kept, but not used, which for
381 long-term mappings means that the space is wasted.
382
383 Trimming can be dynamically controlled through a sysctl option
384 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
385 excess pages there must be before trimming should occur, or zero if
386 no trimming is to occur.
387
388 This option specifies the initial value of this option. The default
389 of 1 says that all excess pages should be trimmed.
390
391 See Documentation/nommu-mmap.txt for more information.
bbddff05 392
4c76d9d1 393config TRANSPARENT_HUGEPAGE
13ece886 394 bool "Transparent Hugepage Support"
15626062 395 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
5d689240 396 select COMPACTION
4c76d9d1
AA
397 help
398 Transparent Hugepages allows the kernel to use huge pages and
399 huge tlb transparently to the applications whenever possible.
400 This feature can improve computing performance to certain
401 applications by speeding up page faults during memory
402 allocation, by reducing the number of tlb misses and by speeding
403 up the pagetable walking.
404
405 If memory constrained on embedded, you may want to say N.
406
13ece886
AA
407choice
408 prompt "Transparent Hugepage Support sysfs defaults"
409 depends on TRANSPARENT_HUGEPAGE
410 default TRANSPARENT_HUGEPAGE_ALWAYS
411 help
412 Selects the sysfs defaults for Transparent Hugepage Support.
413
414 config TRANSPARENT_HUGEPAGE_ALWAYS
415 bool "always"
416 help
417 Enabling Transparent Hugepage always, can increase the
418 memory footprint of applications without a guaranteed
419 benefit but it will work automatically for all applications.
420
421 config TRANSPARENT_HUGEPAGE_MADVISE
422 bool "madvise"
423 help
424 Enabling Transparent Hugepage madvise, will only provide a
425 performance improvement benefit to the applications using
426 madvise(MADV_HUGEPAGE) but it won't risk to increase the
427 memory footprint of applications without a guaranteed
428 benefit.
429endchoice
430
bbddff05
TH
431#
432# UP and nommu archs use km based percpu allocator
433#
434config NEED_PER_CPU_KM
435 depends on !SMP
436 bool
437 default y
077b1f83
DM
438
439config CLEANCACHE
440 bool "Enable cleancache driver to cache clean pages if tmem is present"
441 default n
442 help
443 Cleancache can be thought of as a page-granularity victim cache
444 for clean pages that the kernel's pageframe replacement algorithm
445 (PFRA) would like to keep around, but can't since there isn't enough
446 memory. So when the PFRA "evicts" a page, it first attempts to use
140a1ef2 447 cleancache code to put the data contained in that page into
077b1f83
DM
448 "transcendent memory", memory that is not directly accessible or
449 addressable by the kernel and is of unknown and possibly
450 time-varying size. And when a cleancache-enabled
451 filesystem wishes to access a page in a file on disk, it first
452 checks cleancache to see if it already contains it; if it does,
453 the page is copied into the kernel and a disk access is avoided.
454 When a transcendent memory driver is available (such as zcache or
455 Xen transcendent memory), a significant I/O reduction
456 may be achieved. When none is available, all cleancache calls
457 are reduced to a single pointer-compare-against-NULL resulting
458 in a negligible performance hit.
459
460 If unsure, say Y to enable cleancache
27c6aec2
DM
461
462config FRONTSWAP
463 bool "Enable frontswap to cache swap pages if tmem is present"
464 depends on SWAP
465 default n
466 help
467 Frontswap is so named because it can be thought of as the opposite
468 of a "backing" store for a swap device. The data is stored into
469 "transcendent memory", memory that is not directly accessible or
470 addressable by the kernel and is of unknown and possibly
471 time-varying size. When space in transcendent memory is available,
472 a significant swap I/O reduction may be achieved. When none is
473 available, all frontswap calls are reduced to a single pointer-
474 compare-against-NULL resulting in a negligible performance hit
475 and swap data is stored as normal on the matching swap device.
476
477 If unsure, say Y to enable frontswap.
f825c736
AK
478
479config CMA
480 bool "Contiguous Memory Allocator"
de32a817 481 depends on HAVE_MEMBLOCK && MMU
f825c736
AK
482 select MIGRATION
483 select MEMORY_ISOLATION
484 help
485 This enables the Contiguous Memory Allocator which allows other
486 subsystems to allocate big physically-contiguous blocks of memory.
487 CMA reserves a region of memory and allows only movable pages to
488 be allocated from it. This way, the kernel can use the memory for
489 pagecache and when a subsystem requests for contiguous area, the
490 allocated pages are migrated away to serve the contiguous request.
491
492 If unsure, say "n".
493
494config CMA_DEBUG
495 bool "CMA debug messages (DEVELOPMENT)"
496 depends on DEBUG_KERNEL && CMA
497 help
498 Turns on debug messages in CMA. This produces KERN_DEBUG
499 messages for every CMA call as well as various messages while
500 processing calls such as dma_alloc_from_contiguous().
501 This option does not affect warning and error messages.
bf550fc9 502
28b24c1f
SL
503config CMA_DEBUGFS
504 bool "CMA debugfs interface"
505 depends on CMA && DEBUG_FS
506 help
507 Turns on the DebugFS interface for CMA.
508
a254129e
JK
509config CMA_AREAS
510 int "Maximum count of the CMA areas"
511 depends on CMA
512 default 7
513 help
514 CMA allows to create CMA areas for particular purpose, mainly,
515 used as device private area. This parameter sets the maximum
516 number of CMA area in the system.
517
518 If unsure, leave the default value "7".
519
af8d417a
DS
520config MEM_SOFT_DIRTY
521 bool "Track memory changes"
522 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
523 select PROC_PAGE_MONITOR
4e2e2770 524 help
af8d417a
DS
525 This option enables memory changes tracking by introducing a
526 soft-dirty bit on pte-s. This bit it set when someone writes
527 into a page just as regular dirty bit, but unlike the latter
528 it can be cleared by hands.
529
530 See Documentation/vm/soft-dirty.txt for more details.
4e2e2770 531
2b281117
SJ
532config ZSWAP
533 bool "Compressed cache for swap pages (EXPERIMENTAL)"
534 depends on FRONTSWAP && CRYPTO=y
535 select CRYPTO_LZO
12d79d64 536 select ZPOOL
2b281117
SJ
537 default n
538 help
539 A lightweight compressed cache for swap pages. It takes
540 pages that are in the process of being swapped out and attempts to
541 compress them into a dynamically allocated RAM-based memory pool.
542 This can result in a significant I/O reduction on swap device and,
543 in the case where decompressing from RAM is faster that swap device
544 reads, can also improve workload performance.
545
546 This is marked experimental because it is a new feature (as of
547 v3.11) that interacts heavily with memory reclaim. While these
548 interactions don't cause any known issues on simple memory setups,
549 they have not be fully explored on the large set of potential
550 configurations and workloads that exist.
551
af8d417a
DS
552config ZPOOL
553 tristate "Common API for compressed memory storage"
554 default n
0f8975ec 555 help
af8d417a
DS
556 Compressed memory storage API. This allows using either zbud or
557 zsmalloc.
0f8975ec 558
af8d417a
DS
559config ZBUD
560 tristate "Low density storage for compressed pages"
561 default n
562 help
563 A special purpose allocator for storing compressed pages.
564 It is designed to store up to two compressed pages per physical
565 page. While this design limits storage density, it has simple and
566 deterministic reclaim properties that make it preferable to a higher
567 density approach when reclaim will be used.
bcf1647d
MK
568
569config ZSMALLOC
d867f203 570 tristate "Memory allocator for compressed pages"
bcf1647d
MK
571 depends on MMU
572 default n
573 help
574 zsmalloc is a slab-based memory allocator designed to store
575 compressed RAM pages. zsmalloc uses virtual memory mapping
576 in order to reduce fragmentation. However, this results in a
577 non-standard allocator interface where a handle, not a pointer, is
578 returned by an alloc(). This handle must be mapped in order to
579 access the allocated space.
580
581config PGTABLE_MAPPING
582 bool "Use page table mapping to access object in zsmalloc"
583 depends on ZSMALLOC
584 help
585 By default, zsmalloc uses a copy-based object mapping method to
586 access allocations that span two pages. However, if a particular
587 architecture (ex, ARM) performs VM mapping faster than copying,
588 then you should select this. This causes zsmalloc to use page table
589 mapping rather than copying for object mapping.
590
2216ee85
BH
591 You can check speed with zsmalloc benchmark:
592 https://github.com/spartacus06/zsmapbench
9e5c33d7 593
0f050d99
GM
594config ZSMALLOC_STAT
595 bool "Export zsmalloc statistics"
596 depends on ZSMALLOC
597 select DEBUG_FS
598 help
599 This option enables code in the zsmalloc to collect various
600 statistics about whats happening in zsmalloc and exports that
601 information to userspace via debugfs.
602 If unsure, say N.
603
9e5c33d7
MS
604config GENERIC_EARLY_IOREMAP
605 bool
042d27ac
HD
606
607config MAX_STACK_SIZE_MB
608 int "Maximum user stack size for 32-bit processes (MB)"
609 default 80
610 range 8 256 if METAG
611 range 8 2048
612 depends on STACK_GROWSUP && (!64BIT || COMPAT)
613 help
614 This is the maximum stack size in Megabytes in the VM layout of 32-bit
615 user processes when the stack grows upwards (currently only on parisc
616 and metag arch). The stack will be located at the highest memory
617 address minus the given value, unless the RLIMIT_STACK hard limit is
618 changed to a smaller value in which case that is used.
619
620 A sane initial value is 80 MB.
3a80a7fa
MG
621
622# For architectures that support deferred memory initialisation
623config ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
624 bool
625
626config DEFERRED_STRUCT_PAGE_INIT
627 bool "Defer initialisation of struct pages to kswapd"
628 default n
629 depends on ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
630 depends on MEMORY_HOTPLUG
631 help
632 Ordinarily all struct pages are initialised during early boot in a
633 single thread. On very large machines this can take a considerable
634 amount of time. If this option is set, large machines will bring up
635 a subset of memmap at boot and then initialise the rest in parallel
636 when kswapd starts. This has a potential performance impact on
637 processes running early in the lifetime of the systemm until kswapd
638 finishes the initialisation.
033fbae9 639
33c3fc71
VD
640config IDLE_PAGE_TRACKING
641 bool "Enable idle page tracking"
642 depends on SYSFS && MMU
643 select PAGE_EXTENSION if !64BIT
644 help
645 This feature allows to estimate the amount of user pages that have
646 not been touched during a given period of time. This information can
647 be useful to tune memory cgroup limits and/or for job placement
648 within a compute cluster.
649
650 See Documentation/vm/idle_page_tracking.txt for more details.
651
033fbae9
DW
652config ZONE_DEVICE
653 bool "Device memory (pmem, etc...) hotplug support" if EXPERT
654 default !ZONE_DMA
655 depends on !ZONE_DMA
656 depends on MEMORY_HOTPLUG
657 depends on MEMORY_HOTREMOVE
658 depends on X86_64 #arch_add_memory() comprehends device memory
659
660 help
661 Device memory hotplug support allows for establishing pmem,
662 or other device driver discovered memory regions, in the
663 memmap. This allows pfn_to_page() lookups of otherwise
664 "device-physical" addresses which is needed for using a DAX
665 mapping in an O_DIRECT operation, among other things.
666
667 If FS_DAX is enabled, then say Y.
06a660ad 668
8025e5dd
JK
669config FRAME_VECTOR
670 bool