1config SELECT_MEMORY_MODEL 2 def_bool y 3 depends on ARCH_SELECT_MEMORY_MODEL 4 5choice 6 prompt "Memory model" 7 depends on SELECT_MEMORY_MODEL 8 default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT 9 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT 10 default FLATMEM_MANUAL 11 12config FLATMEM_MANUAL 13 bool "Flat Memory" 14 depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE 15 help 16 This option allows you to change some of the ways that 17 Linux manages its memory internally. Most users will 18 only have one option here: FLATMEM. This is normal 19 and a correct option. 20 21 Some users of more advanced features like NUMA and 22 memory hotplug may have different options here. 23 DISCONTIGMEM is an more mature, better tested system, 24 but is incompatible with memory hotplug and may suffer 25 decreased performance over SPARSEMEM. If unsure between 26 "Sparse Memory" and "Discontiguous Memory", choose 27 "Discontiguous Memory". 28 29 If unsure, choose this option (Flat Memory) over any other. 30 31config DISCONTIGMEM_MANUAL 32 bool "Discontiguous Memory" 33 depends on ARCH_DISCONTIGMEM_ENABLE 34 help 35 This option provides enhanced support for discontiguous 36 memory systems, over FLATMEM. These systems have holes 37 in their physical address spaces, and this option provides 38 more efficient handling of these holes. However, the vast 39 majority of hardware has quite flat address spaces, and 40 can have degraded performance from the extra overhead that 41 this option imposes. 42 43 Many NUMA configurations will have this as the only option. 44 45 If unsure, choose "Flat Memory" over this option. 46 47config SPARSEMEM_MANUAL 48 bool "Sparse Memory" 49 depends on ARCH_SPARSEMEM_ENABLE 50 help 51 This will be the only option for some systems, including 52 memory hotplug systems. This is normal. 53 54 For many other systems, this will be an alternative to 55 "Discontiguous Memory". This option provides some potential 56 performance benefits, along with decreased code complexity, 57 but it is newer, and more experimental. 58 59 If unsure, choose "Discontiguous Memory" or "Flat Memory" 60 over this option. 61 62endchoice 63 64config DISCONTIGMEM 65 def_bool y 66 depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL 67 68config SPARSEMEM 69 def_bool y 70 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL 71 72config FLATMEM 73 def_bool y 74 depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL 75 76config FLAT_NODE_MEM_MAP 77 def_bool y 78 depends on !SPARSEMEM 79 80# 81# Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's 82# to represent different areas of memory. This variable allows 83# those dependencies to exist individually. 84# 85config NEED_MULTIPLE_NODES 86 def_bool y 87 depends on DISCONTIGMEM || NUMA 88 89config HAVE_MEMORY_PRESENT 90 def_bool y 91 depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM 92 93# 94# SPARSEMEM_EXTREME (which is the default) does some bootmem 95# allocations when memory_present() is called. If this cannot 96# be done on your architecture, select this option. However, 97# statically allocating the mem_section[] array can potentially 98# consume vast quantities of .bss, so be careful. 99# 100# This option will also potentially produce smaller runtime code 101# with gcc 3.4 and later. 102# 103config SPARSEMEM_STATIC 104 bool 105 106# 107# Architecture platforms which require a two level mem_section in SPARSEMEM 108# must select this option. This is usually for architecture platforms with 109# an extremely sparse physical address space. 110# 111config SPARSEMEM_EXTREME 112 def_bool y 113 depends on SPARSEMEM && !SPARSEMEM_STATIC 114 115config SPARSEMEM_VMEMMAP_ENABLE 116 bool 117 118config SPARSEMEM_ALLOC_MEM_MAP_TOGETHER 119 def_bool y 120 depends on SPARSEMEM && X86_64 121 122config SPARSEMEM_VMEMMAP 123 bool "Sparse Memory virtual memmap" 124 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE 125 default y 126 help 127 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise 128 pfn_to_page and page_to_pfn operations. This is the most 129 efficient option when sufficient kernel resources are available. 130 131config HAVE_MEMBLOCK 132 boolean 133 134config HAVE_MEMBLOCK_NODE_MAP 135 boolean 136 137config ARCH_DISCARD_MEMBLOCK 138 boolean 139 140config NO_BOOTMEM 141 boolean 142 143config MEMORY_ISOLATION 144 boolean 145 146config MOVABLE_NODE 147 boolean "Enable to assign a node which has only movable memory" 148 depends on HAVE_MEMBLOCK 149 depends on NO_BOOTMEM 150 depends on X86_64 151 depends on NUMA 152 default n 153 help 154 Allow a node to have only movable memory. Pages used by the kernel, 155 such as direct mapping pages cannot be migrated. So the corresponding 156 memory device cannot be hotplugged. This option allows users to 157 online all the memory of a node as movable memory so that the whole 158 node can be hotplugged. Users who don't use the memory hotplug 159 feature are fine with this option on since they don't online memory 160 as movable. 161 162 Say Y here if you want to hotplug a whole node. 163 Say N here if you want kernel to use memory on all nodes evenly. 164 165# 166# Only be set on architectures that have completely implemented memory hotplug 167# feature. If you are not sure, don't touch it. 168# 169config HAVE_BOOTMEM_INFO_NODE 170 def_bool n 171 172# eventually, we can have this option just 'select SPARSEMEM' 173config MEMORY_HOTPLUG 174 bool "Allow for memory hot-add" 175 depends on SPARSEMEM || X86_64_ACPI_NUMA 176 depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG 177 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390) 178 179config MEMORY_HOTPLUG_SPARSE 180 def_bool y 181 depends on SPARSEMEM && MEMORY_HOTPLUG 182 183config MEMORY_HOTREMOVE 184 bool "Allow for memory hot remove" 185 select MEMORY_ISOLATION 186 select HAVE_BOOTMEM_INFO_NODE if X86_64 187 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 188 depends on MIGRATION 189 190# 191# If we have space for more page flags then we can enable additional 192# optimizations and functionality. 193# 194# Regular Sparsemem takes page flag bits for the sectionid if it does not 195# use a virtual memmap. Disable extended page flags for 32 bit platforms 196# that require the use of a sectionid in the page flags. 197# 198config PAGEFLAGS_EXTENDED 199 def_bool y 200 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM 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# 210config SPLIT_PTLOCK_CPUS 211 int 212 default "999999" if ARM && !CPU_CACHE_VIPT 213 default "999999" if PARISC && !PA20 214 default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC 215 default "4" 216 217# 218# support for memory balloon compaction 219config BALLOON_COMPACTION 220 bool "Allow for balloon memory compaction/migration" 221 def_bool y 222 depends on COMPACTION && VIRTIO_BALLOON 223 help 224 Memory fragmentation introduced by ballooning might reduce 225 significantly the number of 2MB contiguous memory blocks that can be 226 used within a guest, thus imposing performance penalties associated 227 with the reduced number of transparent huge pages that could be used 228 by the guest workload. Allowing the compaction & migration for memory 229 pages enlisted as being part of memory balloon devices avoids the 230 scenario aforementioned and helps improving memory defragmentation. 231 232# 233# support for memory compaction 234config COMPACTION 235 bool "Allow for memory compaction" 236 def_bool y 237 select MIGRATION 238 depends on MMU 239 help 240 Allows the compaction of memory for the allocation of huge pages. 241 242# 243# support for page migration 244# 245config MIGRATION 246 bool "Page migration" 247 def_bool y 248 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA 249 help 250 Allows the migration of the physical location of pages of processes 251 while the virtual addresses are not changed. This is useful in 252 two situations. The first is on NUMA systems to put pages nearer 253 to the processors accessing. The second is when allocating huge 254 pages as migration can relocate pages to satisfy a huge page 255 allocation instead of reclaiming. 256 257config PHYS_ADDR_T_64BIT 258 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 259 260config ZONE_DMA_FLAG 261 int 262 default "0" if !ZONE_DMA 263 default "1" 264 265config BOUNCE 266 def_bool y 267 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 268 269# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often 270# have more than 4GB of memory, but we don't currently use the IOTLB to present 271# a 32-bit address to OHCI. So we need to use a bounce pool instead. 272# 273# We also use the bounce pool to provide stable page writes for jbd. jbd 274# initiates buffer writeback without locking the page or setting PG_writeback, 275# and fixing that behavior (a second time; jbd2 doesn't have this problem) is 276# a major rework effort. Instead, use the bounce buffer to snapshot pages 277# (until jbd goes away). The only jbd user is ext3. 278config NEED_BOUNCE_POOL 279 bool 280 default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD) 281 282config NR_QUICK 283 int 284 depends on QUICKLIST 285 default "2" if AVR32 286 default "1" 287 288config VIRT_TO_BUS 289 bool 290 help 291 An architecture should select this if it implements the 292 deprecated interface virt_to_bus(). All new architectures 293 should probably not select this. 294 295 296config MMU_NOTIFIER 297 bool 298 299config KSM 300 bool "Enable KSM for page merging" 301 depends on MMU 302 help 303 Enable Kernel Samepage Merging: KSM periodically scans those areas 304 of an application's address space that an app has advised may be 305 mergeable. When it finds pages of identical content, it replaces 306 the many instances by a single page with that content, so 307 saving memory until one or another app needs to modify the content. 308 Recommended for use with KVM, or with other duplicative applications. 309 See Documentation/vm/ksm.txt for more information: KSM is inactive 310 until a program has madvised that an area is MADV_MERGEABLE, and 311 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 312 313config DEFAULT_MMAP_MIN_ADDR 314 int "Low address space to protect from user allocation" 315 depends on MMU 316 default 4096 317 help 318 This is the portion of low virtual memory which should be protected 319 from userspace allocation. Keeping a user from writing to low pages 320 can help reduce the impact of kernel NULL pointer bugs. 321 322 For most ia64, ppc64 and x86 users with lots of address space 323 a value of 65536 is reasonable and should cause no problems. 324 On arm and other archs it should not be higher than 32768. 325 Programs which use vm86 functionality or have some need to map 326 this low address space will need CAP_SYS_RAWIO or disable this 327 protection by setting the value to 0. 328 329 This value can be changed after boot using the 330 /proc/sys/vm/mmap_min_addr tunable. 331 332config ARCH_SUPPORTS_MEMORY_FAILURE 333 bool 334 335config MEMORY_FAILURE 336 depends on MMU 337 depends on ARCH_SUPPORTS_MEMORY_FAILURE 338 bool "Enable recovery from hardware memory errors" 339 select MEMORY_ISOLATION 340 help 341 Enables code to recover from some memory failures on systems 342 with MCA recovery. This allows a system to continue running 343 even when some of its memory has uncorrected errors. This requires 344 special hardware support and typically ECC memory. 345 346config HWPOISON_INJECT 347 tristate "HWPoison pages injector" 348 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 349 select PROC_PAGE_MONITOR 350 351config NOMMU_INITIAL_TRIM_EXCESS 352 int "Turn on mmap() excess space trimming before booting" 353 depends on !MMU 354 default 1 355 help 356 The NOMMU mmap() frequently needs to allocate large contiguous chunks 357 of memory on which to store mappings, but it can only ask the system 358 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 359 more than it requires. To deal with this, mmap() is able to trim off 360 the excess and return it to the allocator. 361 362 If trimming is enabled, the excess is trimmed off and returned to the 363 system allocator, which can cause extra fragmentation, particularly 364 if there are a lot of transient processes. 365 366 If trimming is disabled, the excess is kept, but not used, which for 367 long-term mappings means that the space is wasted. 368 369 Trimming can be dynamically controlled through a sysctl option 370 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 371 excess pages there must be before trimming should occur, or zero if 372 no trimming is to occur. 373 374 This option specifies the initial value of this option. The default 375 of 1 says that all excess pages should be trimmed. 376 377 See Documentation/nommu-mmap.txt for more information. 378 379config TRANSPARENT_HUGEPAGE 380 bool "Transparent Hugepage Support" 381 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 382 select COMPACTION 383 help 384 Transparent Hugepages allows the kernel to use huge pages and 385 huge tlb transparently to the applications whenever possible. 386 This feature can improve computing performance to certain 387 applications by speeding up page faults during memory 388 allocation, by reducing the number of tlb misses and by speeding 389 up the pagetable walking. 390 391 If memory constrained on embedded, you may want to say N. 392 393choice 394 prompt "Transparent Hugepage Support sysfs defaults" 395 depends on TRANSPARENT_HUGEPAGE 396 default TRANSPARENT_HUGEPAGE_ALWAYS 397 help 398 Selects the sysfs defaults for Transparent Hugepage Support. 399 400 config TRANSPARENT_HUGEPAGE_ALWAYS 401 bool "always" 402 help 403 Enabling Transparent Hugepage always, can increase the 404 memory footprint of applications without a guaranteed 405 benefit but it will work automatically for all applications. 406 407 config TRANSPARENT_HUGEPAGE_MADVISE 408 bool "madvise" 409 help 410 Enabling Transparent Hugepage madvise, will only provide a 411 performance improvement benefit to the applications using 412 madvise(MADV_HUGEPAGE) but it won't risk to increase the 413 memory footprint of applications without a guaranteed 414 benefit. 415endchoice 416 417config CROSS_MEMORY_ATTACH 418 bool "Cross Memory Support" 419 depends on MMU 420 default y 421 help 422 Enabling this option adds the system calls process_vm_readv and 423 process_vm_writev which allow a process with the correct privileges 424 to directly read from or write to to another process's address space. 425 See the man page for more details. 426 427# 428# UP and nommu archs use km based percpu allocator 429# 430config NEED_PER_CPU_KM 431 depends on !SMP 432 bool 433 default y 434 435config CLEANCACHE 436 bool "Enable cleancache driver to cache clean pages if tmem is present" 437 default n 438 help 439 Cleancache can be thought of as a page-granularity victim cache 440 for clean pages that the kernel's pageframe replacement algorithm 441 (PFRA) would like to keep around, but can't since there isn't enough 442 memory. So when the PFRA "evicts" a page, it first attempts to use 443 cleancache code to put the data contained in that page into 444 "transcendent memory", memory that is not directly accessible or 445 addressable by the kernel and is of unknown and possibly 446 time-varying size. And when a cleancache-enabled 447 filesystem wishes to access a page in a file on disk, it first 448 checks cleancache to see if it already contains it; if it does, 449 the page is copied into the kernel and a disk access is avoided. 450 When a transcendent memory driver is available (such as zcache or 451 Xen transcendent memory), a significant I/O reduction 452 may be achieved. When none is available, all cleancache calls 453 are reduced to a single pointer-compare-against-NULL resulting 454 in a negligible performance hit. 455 456 If unsure, say Y to enable cleancache 457 458config FRONTSWAP 459 bool "Enable frontswap to cache swap pages if tmem is present" 460 depends on SWAP 461 default n 462 help 463 Frontswap is so named because it can be thought of as the opposite 464 of a "backing" store for a swap device. The data is stored into 465 "transcendent memory", memory that is not directly accessible or 466 addressable by the kernel and is of unknown and possibly 467 time-varying size. When space in transcendent memory is available, 468 a significant swap I/O reduction may be achieved. When none is 469 available, all frontswap calls are reduced to a single pointer- 470 compare-against-NULL resulting in a negligible performance hit 471 and swap data is stored as normal on the matching swap device. 472 473 If unsure, say Y to enable frontswap. 474