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