1 # SPDX-License-Identifier: GPL-2.0-only 2 3 menu "Memory Management options" 4 5 config SELECT_MEMORY_MODEL 6 def_bool y 7 depends on ARCH_SELECT_MEMORY_MODEL 8 9 choice 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 21 config 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 36 config 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 51 config 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 64 endchoice 65 66 config DISCONTIGMEM 67 def_bool y 68 depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL 69 70 config SPARSEMEM 71 def_bool y 72 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL 73 74 config FLATMEM 75 def_bool y 76 depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL 77 78 config 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 # 87 config 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 # 101 config 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 # 109 config SPARSEMEM_EXTREME 110 def_bool y 111 depends on SPARSEMEM && !SPARSEMEM_STATIC 112 113 config SPARSEMEM_VMEMMAP_ENABLE 114 bool 115 116 config 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. 124 125 config HAVE_MEMBLOCK_PHYS_MAP 126 bool 127 128 config 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. 135 config ARCH_KEEP_MEMBLOCK 136 bool 137 138 # Keep arch NUMA mapping infrastructure post-init. 139 config NUMA_KEEP_MEMINFO 140 bool 141 142 config 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 # 149 config HAVE_BOOTMEM_INFO_NODE 150 def_bool n 151 152 # eventually, we can have this option just 'select SPARSEMEM' 153 config MEMORY_HOTPLUG 154 bool "Allow for memory hot-add" 155 select MEMORY_ISOLATION 156 depends on SPARSEMEM || X86_64_ACPI_NUMA 157 depends on ARCH_ENABLE_MEMORY_HOTPLUG 158 depends on 64BIT || BROKEN 159 select NUMA_KEEP_MEMINFO if NUMA 160 161 config MEMORY_HOTPLUG_SPARSE 162 def_bool y 163 depends on SPARSEMEM && MEMORY_HOTPLUG 164 165 config MEMORY_HOTPLUG_DEFAULT_ONLINE 166 bool "Online the newly added memory blocks by default" 167 depends on MEMORY_HOTPLUG 168 help 169 This option sets the default policy setting for memory hotplug 170 onlining policy (/sys/devices/system/memory/auto_online_blocks) which 171 determines what happens to newly added memory regions. Policy setting 172 can always be changed at runtime. 173 See Documentation/admin-guide/mm/memory-hotplug.rst for more information. 174 175 Say Y here if you want all hot-plugged memory blocks to appear in 176 'online' state by default. 177 Say N here if you want the default policy to keep all hot-plugged 178 memory blocks in 'offline' state. 179 180 config MEMORY_HOTREMOVE 181 bool "Allow for memory hot remove" 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 # 197 config 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" 204 205 config ARCH_ENABLE_SPLIT_PMD_PTLOCK 206 bool 207 208 # 209 # support for memory balloon 210 config MEMORY_BALLOON 211 bool 212 213 # 214 # support for memory balloon compaction 215 config 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 230 config 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 247 config 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 # 259 config 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. 270 271 config ARCH_ENABLE_HUGEPAGE_MIGRATION 272 bool 273 274 config ARCH_ENABLE_THP_MIGRATION 275 bool 276 277 config CONTIG_ALLOC 278 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA 279 280 config PHYS_ADDR_T_64BIT 281 def_bool 64BIT 282 283 config 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. 292 293 config 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. 299 300 301 config MMU_NOTIFIER 302 bool 303 select SRCU 304 select INTERVAL_TREE 305 306 config 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). 320 321 config 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. 339 340 config ARCH_SUPPORTS_MEMORY_FAILURE 341 bool 342 343 config 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. 354 355 config HWPOISON_INJECT 356 tristate "HWPoison pages injector" 357 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 358 select PROC_PAGE_MONITOR 359 360 config 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/admin-guide/mm/nommu-mmap.rst for more information. 387 388 config 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. 402 403 choice 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. 425 endchoice 426 427 config ARCH_WANTS_THP_SWAP 428 def_bool n 429 430 config 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 # 443 config NEED_PER_CPU_KM 444 depends on !SMP 445 bool 446 default y 447 448 config 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 469 470 config 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. 485 486 config 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". 500 501 config 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. 509 510 config CMA_DEBUGFS 511 bool "CMA debugfs interface" 512 depends on CMA && DEBUG_FS 513 help 514 Turns on the DebugFS interface for CMA. 515 516 config CMA_AREAS 517 int "Maximum count of the CMA areas" 518 depends on CMA 519 default 19 if NUMA 520 default 7 521 help 522 CMA allows to create CMA areas for particular purpose, mainly, 523 used as device private area. This parameter sets the maximum 524 number of CMA area in the system. 525 526 If unsure, leave the default value "7" in UMA and "19" in NUMA. 527 528 config MEM_SOFT_DIRTY 529 bool "Track memory changes" 530 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 531 select PROC_PAGE_MONITOR 532 help 533 This option enables memory changes tracking by introducing a 534 soft-dirty bit on pte-s. This bit it set when someone writes 535 into a page just as regular dirty bit, but unlike the latter 536 it can be cleared by hands. 537 538 See Documentation/admin-guide/mm/soft-dirty.rst for more details. 539 540 config ZSWAP 541 bool "Compressed cache for swap pages (EXPERIMENTAL)" 542 depends on FRONTSWAP && CRYPTO=y 543 select ZPOOL 544 help 545 A lightweight compressed cache for swap pages. It takes 546 pages that are in the process of being swapped out and attempts to 547 compress them into a dynamically allocated RAM-based memory pool. 548 This can result in a significant I/O reduction on swap device and, 549 in the case where decompressing from RAM is faster that swap device 550 reads, can also improve workload performance. 551 552 This is marked experimental because it is a new feature (as of 553 v3.11) that interacts heavily with memory reclaim. While these 554 interactions don't cause any known issues on simple memory setups, 555 they have not be fully explored on the large set of potential 556 configurations and workloads that exist. 557 558 choice 559 prompt "Compressed cache for swap pages default compressor" 560 depends on ZSWAP 561 default ZSWAP_COMPRESSOR_DEFAULT_LZO 562 help 563 Selects the default compression algorithm for the compressed cache 564 for swap pages. 565 566 For an overview what kind of performance can be expected from 567 a particular compression algorithm please refer to the benchmarks 568 available at the following LWN page: 569 https://lwn.net/Articles/751795/ 570 571 If in doubt, select 'LZO'. 572 573 The selection made here can be overridden by using the kernel 574 command line 'zswap.compressor=' option. 575 576 config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE 577 bool "Deflate" 578 select CRYPTO_DEFLATE 579 help 580 Use the Deflate algorithm as the default compression algorithm. 581 582 config ZSWAP_COMPRESSOR_DEFAULT_LZO 583 bool "LZO" 584 select CRYPTO_LZO 585 help 586 Use the LZO algorithm as the default compression algorithm. 587 588 config ZSWAP_COMPRESSOR_DEFAULT_842 589 bool "842" 590 select CRYPTO_842 591 help 592 Use the 842 algorithm as the default compression algorithm. 593 594 config ZSWAP_COMPRESSOR_DEFAULT_LZ4 595 bool "LZ4" 596 select CRYPTO_LZ4 597 help 598 Use the LZ4 algorithm as the default compression algorithm. 599 600 config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC 601 bool "LZ4HC" 602 select CRYPTO_LZ4HC 603 help 604 Use the LZ4HC algorithm as the default compression algorithm. 605 606 config ZSWAP_COMPRESSOR_DEFAULT_ZSTD 607 bool "zstd" 608 select CRYPTO_ZSTD 609 help 610 Use the zstd algorithm as the default compression algorithm. 611 endchoice 612 613 config ZSWAP_COMPRESSOR_DEFAULT 614 string 615 depends on ZSWAP 616 default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE 617 default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO 618 default "842" if ZSWAP_COMPRESSOR_DEFAULT_842 619 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4 620 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC 621 default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD 622 default "" 623 624 choice 625 prompt "Compressed cache for swap pages default allocator" 626 depends on ZSWAP 627 default ZSWAP_ZPOOL_DEFAULT_ZBUD 628 help 629 Selects the default allocator for the compressed cache for 630 swap pages. 631 The default is 'zbud' for compatibility, however please do 632 read the description of each of the allocators below before 633 making a right choice. 634 635 The selection made here can be overridden by using the kernel 636 command line 'zswap.zpool=' option. 637 638 config ZSWAP_ZPOOL_DEFAULT_ZBUD 639 bool "zbud" 640 select ZBUD 641 help 642 Use the zbud allocator as the default allocator. 643 644 config ZSWAP_ZPOOL_DEFAULT_Z3FOLD 645 bool "z3fold" 646 select Z3FOLD 647 help 648 Use the z3fold allocator as the default allocator. 649 650 config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC 651 bool "zsmalloc" 652 select ZSMALLOC 653 help 654 Use the zsmalloc allocator as the default allocator. 655 endchoice 656 657 config ZSWAP_ZPOOL_DEFAULT 658 string 659 depends on ZSWAP 660 default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD 661 default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD 662 default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC 663 default "" 664 665 config ZSWAP_DEFAULT_ON 666 bool "Enable the compressed cache for swap pages by default" 667 depends on ZSWAP 668 help 669 If selected, the compressed cache for swap pages will be enabled 670 at boot, otherwise it will be disabled. 671 672 The selection made here can be overridden by using the kernel 673 command line 'zswap.enabled=' option. 674 675 config ZPOOL 676 tristate "Common API for compressed memory storage" 677 help 678 Compressed memory storage API. This allows using either zbud or 679 zsmalloc. 680 681 config ZBUD 682 tristate "Low (Up to 2x) density storage for compressed pages" 683 help 684 A special purpose allocator for storing compressed pages. 685 It is designed to store up to two compressed pages per physical 686 page. While this design limits storage density, it has simple and 687 deterministic reclaim properties that make it preferable to a higher 688 density approach when reclaim will be used. 689 690 config Z3FOLD 691 tristate "Up to 3x density storage for compressed pages" 692 depends on ZPOOL 693 help 694 A special purpose allocator for storing compressed pages. 695 It is designed to store up to three compressed pages per physical 696 page. It is a ZBUD derivative so the simplicity and determinism are 697 still there. 698 699 config ZSMALLOC 700 tristate "Memory allocator for compressed pages" 701 depends on MMU 702 help 703 zsmalloc is a slab-based memory allocator designed to store 704 compressed RAM pages. zsmalloc uses virtual memory mapping 705 in order to reduce fragmentation. However, this results in a 706 non-standard allocator interface where a handle, not a pointer, is 707 returned by an alloc(). This handle must be mapped in order to 708 access the allocated space. 709 710 config ZSMALLOC_PGTABLE_MAPPING 711 bool "Use page table mapping to access object in zsmalloc" 712 depends on ZSMALLOC=y 713 help 714 By default, zsmalloc uses a copy-based object mapping method to 715 access allocations that span two pages. However, if a particular 716 architecture (ex, ARM) performs VM mapping faster than copying, 717 then you should select this. This causes zsmalloc to use page table 718 mapping rather than copying for object mapping. 719 720 You can check speed with zsmalloc benchmark: 721 https://github.com/spartacus06/zsmapbench 722 723 config ZSMALLOC_STAT 724 bool "Export zsmalloc statistics" 725 depends on ZSMALLOC 726 select DEBUG_FS 727 help 728 This option enables code in the zsmalloc to collect various 729 statistics about whats happening in zsmalloc and exports that 730 information to userspace via debugfs. 731 If unsure, say N. 732 733 config GENERIC_EARLY_IOREMAP 734 bool 735 736 config MAX_STACK_SIZE_MB 737 int "Maximum user stack size for 32-bit processes (MB)" 738 default 80 739 range 8 2048 740 depends on STACK_GROWSUP && (!64BIT || COMPAT) 741 help 742 This is the maximum stack size in Megabytes in the VM layout of 32-bit 743 user processes when the stack grows upwards (currently only on parisc 744 arch). The stack will be located at the highest memory address minus 745 the given value, unless the RLIMIT_STACK hard limit is changed to a 746 smaller value in which case that is used. 747 748 A sane initial value is 80 MB. 749 750 config DEFERRED_STRUCT_PAGE_INIT 751 bool "Defer initialisation of struct pages to kthreads" 752 depends on SPARSEMEM 753 depends on !NEED_PER_CPU_KM 754 depends on 64BIT 755 select PADATA 756 help 757 Ordinarily all struct pages are initialised during early boot in a 758 single thread. On very large machines this can take a considerable 759 amount of time. If this option is set, large machines will bring up 760 a subset of memmap at boot and then initialise the rest in parallel. 761 This has a potential performance impact on tasks running early in the 762 lifetime of the system until these kthreads finish the 763 initialisation. 764 765 config IDLE_PAGE_TRACKING 766 bool "Enable idle page tracking" 767 depends on SYSFS && MMU 768 select PAGE_EXTENSION if !64BIT 769 help 770 This feature allows to estimate the amount of user pages that have 771 not been touched during a given period of time. This information can 772 be useful to tune memory cgroup limits and/or for job placement 773 within a compute cluster. 774 775 See Documentation/admin-guide/mm/idle_page_tracking.rst for 776 more details. 777 778 config ARCH_HAS_PTE_DEVMAP 779 bool 780 781 config ZONE_DEVICE 782 bool "Device memory (pmem, HMM, etc...) hotplug support" 783 depends on MEMORY_HOTPLUG 784 depends on MEMORY_HOTREMOVE 785 depends on SPARSEMEM_VMEMMAP 786 depends on ARCH_HAS_PTE_DEVMAP 787 select XARRAY_MULTI 788 789 help 790 Device memory hotplug support allows for establishing pmem, 791 or other device driver discovered memory regions, in the 792 memmap. This allows pfn_to_page() lookups of otherwise 793 "device-physical" addresses which is needed for using a DAX 794 mapping in an O_DIRECT operation, among other things. 795 796 If FS_DAX is enabled, then say Y. 797 798 config DEV_PAGEMAP_OPS 799 bool 800 801 # 802 # Helpers to mirror range of the CPU page tables of a process into device page 803 # tables. 804 # 805 config HMM_MIRROR 806 bool 807 depends on MMU 808 809 config DEVICE_PRIVATE 810 bool "Unaddressable device memory (GPU memory, ...)" 811 depends on ZONE_DEVICE 812 select DEV_PAGEMAP_OPS 813 814 help 815 Allows creation of struct pages to represent unaddressable device 816 memory; i.e., memory that is only accessible from the device (or 817 group of devices). You likely also want to select HMM_MIRROR. 818 819 config VMAP_PFN 820 bool 821 822 config FRAME_VECTOR 823 bool 824 825 config ARCH_USES_HIGH_VMA_FLAGS 826 bool 827 config ARCH_HAS_PKEYS 828 bool 829 830 config PERCPU_STATS 831 bool "Collect percpu memory statistics" 832 help 833 This feature collects and exposes statistics via debugfs. The 834 information includes global and per chunk statistics, which can 835 be used to help understand percpu memory usage. 836 837 config GUP_BENCHMARK 838 bool "Enable infrastructure for get_user_pages() and related calls benchmarking" 839 help 840 Provides /sys/kernel/debug/gup_benchmark that helps with testing 841 performance of get_user_pages() and related calls. 842 843 See tools/testing/selftests/vm/gup_benchmark.c 844 845 config GUP_GET_PTE_LOW_HIGH 846 bool 847 848 config READ_ONLY_THP_FOR_FS 849 bool "Read-only THP for filesystems (EXPERIMENTAL)" 850 depends on TRANSPARENT_HUGEPAGE && SHMEM 851 852 help 853 Allow khugepaged to put read-only file-backed pages in THP. 854 855 This is marked experimental because it is a new feature. Write 856 support of file THPs will be developed in the next few release 857 cycles. 858 859 config ARCH_HAS_PTE_SPECIAL 860 bool 861 862 # 863 # Some architectures require a special hugepage directory format that is 864 # required to support multiple hugepage sizes. For example a4fe3ce76 865 # "powerpc/mm: Allow more flexible layouts for hugepage pagetables" 866 # introduced it on powerpc. This allows for a more flexible hugepage 867 # pagetable layouts. 868 # 869 config ARCH_HAS_HUGEPD 870 bool 871 872 config MAPPING_DIRTY_HELPERS 873 bool 874 875 endmenu 876