1ec8f24b7SThomas Gleixner# SPDX-License-Identifier: GPL-2.0-only 259e0b520SChristoph Hellwig 359e0b520SChristoph Hellwigmenu "Memory Management options" 459e0b520SChristoph Hellwig 5e1785e85SDave Hansenconfig SELECT_MEMORY_MODEL 6e1785e85SDave Hansen def_bool y 7a8826eebSKees Cook depends on ARCH_SELECT_MEMORY_MODEL 8e1785e85SDave Hansen 93a9da765SDave Hansenchoice 103a9da765SDave Hansen prompt "Memory model" 11e1785e85SDave Hansen depends on SELECT_MEMORY_MODEL 12e1785e85SDave Hansen default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT 13d41dee36SAndy Whitcroft default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT 14e1785e85SDave Hansen default FLATMEM_MANUAL 15d66d109dSMike Rapoport help 16d66d109dSMike Rapoport This option allows you to change some of the ways that 17d66d109dSMike Rapoport Linux manages its memory internally. Most users will 18d66d109dSMike Rapoport only have one option here selected by the architecture 19d66d109dSMike Rapoport configuration. This is normal. 203a9da765SDave Hansen 21e1785e85SDave Hansenconfig FLATMEM_MANUAL 223a9da765SDave Hansen bool "Flat Memory" 23c898ec16SAnton Blanchard depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE 243a9da765SDave Hansen help 25d66d109dSMike Rapoport This option is best suited for non-NUMA systems with 26d66d109dSMike Rapoport flat address space. The FLATMEM is the most efficient 27d66d109dSMike Rapoport system in terms of performance and resource consumption 28d66d109dSMike Rapoport and it is the best option for smaller systems. 293a9da765SDave Hansen 30d66d109dSMike Rapoport For systems that have holes in their physical address 31d66d109dSMike Rapoport spaces and for features like NUMA and memory hotplug, 32*dd33d29aSRandy Dunlap choose "Sparse Memory". 33d41dee36SAndy Whitcroft 34d41dee36SAndy Whitcroft If unsure, choose this option (Flat Memory) over any other. 353a9da765SDave Hansen 36e1785e85SDave Hansenconfig DISCONTIGMEM_MANUAL 37f3519f91SDave Hansen bool "Discontiguous Memory" 383a9da765SDave Hansen depends on ARCH_DISCONTIGMEM_ENABLE 393a9da765SDave Hansen help 40785dcd44SDave Hansen This option provides enhanced support for discontiguous 41785dcd44SDave Hansen memory systems, over FLATMEM. These systems have holes 42785dcd44SDave Hansen in their physical address spaces, and this option provides 43d66d109dSMike Rapoport more efficient handling of these holes. 44785dcd44SDave Hansen 45d66d109dSMike Rapoport Although "Discontiguous Memory" is still used by several 46d66d109dSMike Rapoport architectures, it is considered deprecated in favor of 47d66d109dSMike Rapoport "Sparse Memory". 48785dcd44SDave Hansen 49d66d109dSMike Rapoport If unsure, choose "Sparse Memory" over this option. 503a9da765SDave Hansen 51d41dee36SAndy Whitcroftconfig SPARSEMEM_MANUAL 52d41dee36SAndy Whitcroft bool "Sparse Memory" 53d41dee36SAndy Whitcroft depends on ARCH_SPARSEMEM_ENABLE 54d41dee36SAndy Whitcroft help 55d41dee36SAndy Whitcroft This will be the only option for some systems, including 56d66d109dSMike Rapoport memory hot-plug systems. This is normal. 57d41dee36SAndy Whitcroft 58d66d109dSMike Rapoport This option provides efficient support for systems with 59d66d109dSMike Rapoport holes is their physical address space and allows memory 60d66d109dSMike Rapoport hot-plug and hot-remove. 61d41dee36SAndy Whitcroft 62d66d109dSMike Rapoport If unsure, choose "Flat Memory" over this option. 63d41dee36SAndy Whitcroft 643a9da765SDave Hansenendchoice 653a9da765SDave Hansen 66e1785e85SDave Hansenconfig DISCONTIGMEM 67e1785e85SDave Hansen def_bool y 68e1785e85SDave Hansen depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL 69e1785e85SDave Hansen 70d41dee36SAndy Whitcroftconfig SPARSEMEM 71d41dee36SAndy Whitcroft def_bool y 721a83e175SRussell King depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL 73d41dee36SAndy Whitcroft 74e1785e85SDave Hansenconfig FLATMEM 75e1785e85SDave Hansen def_bool y 76d41dee36SAndy Whitcroft depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL 77d41dee36SAndy Whitcroft 78d41dee36SAndy Whitcroftconfig FLAT_NODE_MEM_MAP 79d41dee36SAndy Whitcroft def_bool y 80d41dee36SAndy Whitcroft depends on !SPARSEMEM 81e1785e85SDave Hansen 8293b7504eSDave Hansen# 8393b7504eSDave Hansen# Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's 8493b7504eSDave Hansen# to represent different areas of memory. This variable allows 8593b7504eSDave Hansen# those dependencies to exist individually. 8693b7504eSDave Hansen# 8793b7504eSDave Hansenconfig NEED_MULTIPLE_NODES 8893b7504eSDave Hansen def_bool y 8993b7504eSDave Hansen depends on DISCONTIGMEM || NUMA 90af705362SAndy Whitcroft 91af705362SAndy Whitcroftconfig HAVE_MEMORY_PRESENT 92af705362SAndy Whitcroft def_bool y 93d41dee36SAndy Whitcroft depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM 94802f192eSBob Picco 95802f192eSBob Picco# 963e347261SBob Picco# SPARSEMEM_EXTREME (which is the default) does some bootmem 973e347261SBob Picco# allocations when memory_present() is called. If this cannot 983e347261SBob Picco# be done on your architecture, select this option. However, 993e347261SBob Picco# statically allocating the mem_section[] array can potentially 1003e347261SBob Picco# consume vast quantities of .bss, so be careful. 1013e347261SBob Picco# 1023e347261SBob Picco# This option will also potentially produce smaller runtime code 1033e347261SBob Picco# with gcc 3.4 and later. 1043e347261SBob Picco# 1053e347261SBob Piccoconfig SPARSEMEM_STATIC 1069ba16087SJan Beulich bool 1073e347261SBob Picco 1083e347261SBob Picco# 10944c09201SMatt LaPlante# Architecture platforms which require a two level mem_section in SPARSEMEM 110802f192eSBob Picco# must select this option. This is usually for architecture platforms with 111802f192eSBob Picco# an extremely sparse physical address space. 112802f192eSBob Picco# 1133e347261SBob Piccoconfig SPARSEMEM_EXTREME 1143e347261SBob Picco def_bool y 1153e347261SBob Picco depends on SPARSEMEM && !SPARSEMEM_STATIC 1164c21e2f2SHugh Dickins 11729c71111SAndy Whitcroftconfig SPARSEMEM_VMEMMAP_ENABLE 1189ba16087SJan Beulich bool 11929c71111SAndy Whitcroft 12029c71111SAndy Whitcroftconfig SPARSEMEM_VMEMMAP 121a5ee6daaSGeoff Levand bool "Sparse Memory virtual memmap" 122a5ee6daaSGeoff Levand depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE 123a5ee6daaSGeoff Levand default y 124a5ee6daaSGeoff Levand help 125a5ee6daaSGeoff Levand SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise 126a5ee6daaSGeoff Levand pfn_to_page and page_to_pfn operations. This is the most 127a5ee6daaSGeoff Levand efficient option when sufficient kernel resources are available. 12829c71111SAndy Whitcroft 1297c0caeb8STejun Heoconfig HAVE_MEMBLOCK_NODE_MAP 1306341e62bSChristoph Jaeger bool 1317c0caeb8STejun Heo 13270210ed9SPhilipp Hachtmannconfig HAVE_MEMBLOCK_PHYS_MAP 1336341e62bSChristoph Jaeger bool 13470210ed9SPhilipp Hachtmann 13567a929e0SChristoph Hellwigconfig HAVE_FAST_GUP 136050a9adcSChristoph Hellwig depends on MMU 1376341e62bSChristoph Jaeger bool 1382667f50eSSteve Capper 139350e88baSMike Rapoportconfig ARCH_KEEP_MEMBLOCK 1406341e62bSChristoph Jaeger bool 141c378ddd5STejun Heo 142ee6f509cSMinchan Kimconfig MEMORY_ISOLATION 1436341e62bSChristoph Jaeger bool 144ee6f509cSMinchan Kim 14546723bfaSYasuaki Ishimatsu# 14646723bfaSYasuaki Ishimatsu# Only be set on architectures that have completely implemented memory hotplug 14746723bfaSYasuaki Ishimatsu# feature. If you are not sure, don't touch it. 14846723bfaSYasuaki Ishimatsu# 14946723bfaSYasuaki Ishimatsuconfig HAVE_BOOTMEM_INFO_NODE 15046723bfaSYasuaki Ishimatsu def_bool n 15146723bfaSYasuaki Ishimatsu 1523947be19SDave Hansen# eventually, we can have this option just 'select SPARSEMEM' 1533947be19SDave Hansenconfig MEMORY_HOTPLUG 1543947be19SDave Hansen bool "Allow for memory hot-add" 155ec69acbbSKeith Mannthey depends on SPARSEMEM || X86_64_ACPI_NUMA 15640b31360SStephen Rothwell depends on ARCH_ENABLE_MEMORY_HOTPLUG 1573947be19SDave Hansen 158ec69acbbSKeith Manntheyconfig MEMORY_HOTPLUG_SPARSE 159ec69acbbSKeith Mannthey def_bool y 160ec69acbbSKeith Mannthey depends on SPARSEMEM && MEMORY_HOTPLUG 161ec69acbbSKeith Mannthey 1628604d9e5SVitaly Kuznetsovconfig MEMORY_HOTPLUG_DEFAULT_ONLINE 1638604d9e5SVitaly Kuznetsov bool "Online the newly added memory blocks by default" 1648604d9e5SVitaly Kuznetsov depends on MEMORY_HOTPLUG 1658604d9e5SVitaly Kuznetsov help 1668604d9e5SVitaly Kuznetsov This option sets the default policy setting for memory hotplug 1678604d9e5SVitaly Kuznetsov onlining policy (/sys/devices/system/memory/auto_online_blocks) which 1688604d9e5SVitaly Kuznetsov determines what happens to newly added memory regions. Policy setting 1698604d9e5SVitaly Kuznetsov can always be changed at runtime. 170cb1aaebeSMauro Carvalho Chehab See Documentation/admin-guide/mm/memory-hotplug.rst for more information. 1718604d9e5SVitaly Kuznetsov 1728604d9e5SVitaly Kuznetsov Say Y here if you want all hot-plugged memory blocks to appear in 1738604d9e5SVitaly Kuznetsov 'online' state by default. 1748604d9e5SVitaly Kuznetsov Say N here if you want the default policy to keep all hot-plugged 1758604d9e5SVitaly Kuznetsov memory blocks in 'offline' state. 1768604d9e5SVitaly Kuznetsov 1770c0e6195SKAMEZAWA Hiroyukiconfig MEMORY_HOTREMOVE 1780c0e6195SKAMEZAWA Hiroyuki bool "Allow for memory hot remove" 17946723bfaSYasuaki Ishimatsu select MEMORY_ISOLATION 180f7e3334aSNathan Fontenot select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64) 1810c0e6195SKAMEZAWA Hiroyuki depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 1820c0e6195SKAMEZAWA Hiroyuki depends on MIGRATION 1830c0e6195SKAMEZAWA Hiroyuki 1844c21e2f2SHugh Dickins# Heavily threaded applications may benefit from splitting the mm-wide 1854c21e2f2SHugh Dickins# page_table_lock, so that faults on different parts of the user address 1864c21e2f2SHugh Dickins# space can be handled with less contention: split it at this NR_CPUS. 1874c21e2f2SHugh Dickins# Default to 4 for wider testing, though 8 might be more appropriate. 1884c21e2f2SHugh Dickins# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 1897b6ac9dfSHugh Dickins# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 190a70caa8bSHugh Dickins# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 1914c21e2f2SHugh Dickins# 1924c21e2f2SHugh Dickinsconfig SPLIT_PTLOCK_CPUS 1934c21e2f2SHugh Dickins int 1949164550eSKirill A. Shutemov default "999999" if !MMU 195a70caa8bSHugh Dickins default "999999" if ARM && !CPU_CACHE_VIPT 196a70caa8bSHugh Dickins default "999999" if PARISC && !PA20 1974c21e2f2SHugh Dickins default "4" 1987cbe34cfSChristoph Lameter 199e009bb30SKirill A. Shutemovconfig ARCH_ENABLE_SPLIT_PMD_PTLOCK 2006341e62bSChristoph Jaeger bool 201e009bb30SKirill A. Shutemov 2027cbe34cfSChristoph Lameter# 20309316c09SKonstantin Khlebnikov# support for memory balloon 20409316c09SKonstantin Khlebnikovconfig MEMORY_BALLOON 2056341e62bSChristoph Jaeger bool 20609316c09SKonstantin Khlebnikov 20709316c09SKonstantin Khlebnikov# 20818468d93SRafael Aquini# support for memory balloon compaction 20918468d93SRafael Aquiniconfig BALLOON_COMPACTION 21018468d93SRafael Aquini bool "Allow for balloon memory compaction/migration" 21118468d93SRafael Aquini def_bool y 21209316c09SKonstantin Khlebnikov depends on COMPACTION && MEMORY_BALLOON 21318468d93SRafael Aquini help 21418468d93SRafael Aquini Memory fragmentation introduced by ballooning might reduce 21518468d93SRafael Aquini significantly the number of 2MB contiguous memory blocks that can be 21618468d93SRafael Aquini used within a guest, thus imposing performance penalties associated 21718468d93SRafael Aquini with the reduced number of transparent huge pages that could be used 21818468d93SRafael Aquini by the guest workload. Allowing the compaction & migration for memory 21918468d93SRafael Aquini pages enlisted as being part of memory balloon devices avoids the 22018468d93SRafael Aquini scenario aforementioned and helps improving memory defragmentation. 22118468d93SRafael Aquini 22218468d93SRafael Aquini# 223e9e96b39SMel Gorman# support for memory compaction 224e9e96b39SMel Gormanconfig COMPACTION 225e9e96b39SMel Gorman bool "Allow for memory compaction" 22605106e6aSRik van Riel def_bool y 227e9e96b39SMel Gorman select MIGRATION 22833a93877SAndrea Arcangeli depends on MMU 229e9e96b39SMel Gorman help 230b32eaf71SMichal Hocko Compaction is the only memory management component to form 231b32eaf71SMichal Hocko high order (larger physically contiguous) memory blocks 232b32eaf71SMichal Hocko reliably. The page allocator relies on compaction heavily and 233b32eaf71SMichal Hocko the lack of the feature can lead to unexpected OOM killer 234b32eaf71SMichal Hocko invocations for high order memory requests. You shouldn't 235b32eaf71SMichal Hocko disable this option unless there really is a strong reason for 236b32eaf71SMichal Hocko it and then we would be really interested to hear about that at 237b32eaf71SMichal Hocko linux-mm@kvack.org. 238e9e96b39SMel Gorman 239e9e96b39SMel Gorman# 2407cbe34cfSChristoph Lameter# support for page migration 2417cbe34cfSChristoph Lameter# 2427cbe34cfSChristoph Lameterconfig MIGRATION 243b20a3503SChristoph Lameter bool "Page migration" 2446c5240aeSChristoph Lameter def_bool y 245de32a817SChen Gang depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU 246b20a3503SChristoph Lameter help 247b20a3503SChristoph Lameter Allows the migration of the physical location of pages of processes 248e9e96b39SMel Gorman while the virtual addresses are not changed. This is useful in 249e9e96b39SMel Gorman two situations. The first is on NUMA systems to put pages nearer 250e9e96b39SMel Gorman to the processors accessing. The second is when allocating huge 251e9e96b39SMel Gorman pages as migration can relocate pages to satisfy a huge page 252e9e96b39SMel Gorman allocation instead of reclaiming. 2536550e07fSGreg Kroah-Hartman 254c177c81eSNaoya Horiguchiconfig ARCH_ENABLE_HUGEPAGE_MIGRATION 2556341e62bSChristoph Jaeger bool 256c177c81eSNaoya Horiguchi 2579c670ea3SNaoya Horiguchiconfig ARCH_ENABLE_THP_MIGRATION 2589c670ea3SNaoya Horiguchi bool 2599c670ea3SNaoya Horiguchi 2608df995f6SAlexandre Ghiticonfig CONTIG_ALLOC 2618df995f6SAlexandre Ghiti def_bool (MEMORY_ISOLATION && COMPACTION) || CMA 2628df995f6SAlexandre Ghiti 263600715dcSJeremy Fitzhardingeconfig PHYS_ADDR_T_64BIT 264d4a451d5SChristoph Hellwig def_bool 64BIT 265600715dcSJeremy Fitzhardinge 2662a7326b5SChristoph Lameterconfig BOUNCE 2679ca24e2eSVinayak Menon bool "Enable bounce buffers" 2689ca24e2eSVinayak Menon default y 2692a7326b5SChristoph Lameter depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 2709ca24e2eSVinayak Menon help 2719ca24e2eSVinayak Menon Enable bounce buffers for devices that cannot access 2729ca24e2eSVinayak Menon the full range of memory available to the CPU. Enabled 2739ca24e2eSVinayak Menon by default when ZONE_DMA or HIGHMEM is selected, but you 2749ca24e2eSVinayak Menon may say n to override this. 2752a7326b5SChristoph Lameter 276f057eac0SStephen Rothwellconfig VIRT_TO_BUS 2774febd95aSStephen Rothwell bool 2784febd95aSStephen Rothwell help 2794febd95aSStephen Rothwell An architecture should select this if it implements the 2804febd95aSStephen Rothwell deprecated interface virt_to_bus(). All new architectures 2814febd95aSStephen Rothwell should probably not select this. 2824febd95aSStephen Rothwell 283cddb8a5cSAndrea Arcangeli 284cddb8a5cSAndrea Arcangeliconfig MMU_NOTIFIER 285cddb8a5cSAndrea Arcangeli bool 28683fe27eaSPranith Kumar select SRCU 28799cb252fSJason Gunthorpe select INTERVAL_TREE 288fc4d5c29SDavid Howells 289f8af4da3SHugh Dickinsconfig KSM 290f8af4da3SHugh Dickins bool "Enable KSM for page merging" 291f8af4da3SHugh Dickins depends on MMU 29259e1a2f4STimofey Titovets select XXHASH 293f8af4da3SHugh Dickins help 294f8af4da3SHugh Dickins Enable Kernel Samepage Merging: KSM periodically scans those areas 295f8af4da3SHugh Dickins of an application's address space that an app has advised may be 296f8af4da3SHugh Dickins mergeable. When it finds pages of identical content, it replaces 297d0f209f6SHugh Dickins the many instances by a single page with that content, so 298f8af4da3SHugh Dickins saving memory until one or another app needs to modify the content. 299f8af4da3SHugh Dickins Recommended for use with KVM, or with other duplicative applications. 300ad56b738SMike Rapoport See Documentation/vm/ksm.rst for more information: KSM is inactive 301c73602adSHugh Dickins until a program has madvised that an area is MADV_MERGEABLE, and 302c73602adSHugh Dickins root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 303f8af4da3SHugh Dickins 304e0a94c2aSChristoph Lameterconfig DEFAULT_MMAP_MIN_ADDR 305e0a94c2aSChristoph Lameter int "Low address space to protect from user allocation" 3066e141546SDavid Howells depends on MMU 307e0a94c2aSChristoph Lameter default 4096 308e0a94c2aSChristoph Lameter help 309e0a94c2aSChristoph Lameter This is the portion of low virtual memory which should be protected 310e0a94c2aSChristoph Lameter from userspace allocation. Keeping a user from writing to low pages 311e0a94c2aSChristoph Lameter can help reduce the impact of kernel NULL pointer bugs. 312e0a94c2aSChristoph Lameter 313e0a94c2aSChristoph Lameter For most ia64, ppc64 and x86 users with lots of address space 314e0a94c2aSChristoph Lameter a value of 65536 is reasonable and should cause no problems. 315e0a94c2aSChristoph Lameter On arm and other archs it should not be higher than 32768. 316788084abSEric Paris Programs which use vm86 functionality or have some need to map 317788084abSEric Paris this low address space will need CAP_SYS_RAWIO or disable this 318788084abSEric Paris protection by setting the value to 0. 319e0a94c2aSChristoph Lameter 320e0a94c2aSChristoph Lameter This value can be changed after boot using the 321e0a94c2aSChristoph Lameter /proc/sys/vm/mmap_min_addr tunable. 322e0a94c2aSChristoph Lameter 323d949f36fSLinus Torvaldsconfig ARCH_SUPPORTS_MEMORY_FAILURE 324d949f36fSLinus Torvalds bool 325e0a94c2aSChristoph Lameter 3266a46079cSAndi Kleenconfig MEMORY_FAILURE 3276a46079cSAndi Kleen depends on MMU 328d949f36fSLinus Torvalds depends on ARCH_SUPPORTS_MEMORY_FAILURE 3296a46079cSAndi Kleen bool "Enable recovery from hardware memory errors" 330ee6f509cSMinchan Kim select MEMORY_ISOLATION 33197f0b134SXie XiuQi select RAS 3326a46079cSAndi Kleen help 3336a46079cSAndi Kleen Enables code to recover from some memory failures on systems 3346a46079cSAndi Kleen with MCA recovery. This allows a system to continue running 3356a46079cSAndi Kleen even when some of its memory has uncorrected errors. This requires 3366a46079cSAndi Kleen special hardware support and typically ECC memory. 3376a46079cSAndi Kleen 338cae681fcSAndi Kleenconfig HWPOISON_INJECT 339413f9efbSAndi Kleen tristate "HWPoison pages injector" 34027df5068SAndi Kleen depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 341478c5ffcSWu Fengguang select PROC_PAGE_MONITOR 342cae681fcSAndi Kleen 343fc4d5c29SDavid Howellsconfig NOMMU_INITIAL_TRIM_EXCESS 344fc4d5c29SDavid Howells int "Turn on mmap() excess space trimming before booting" 345fc4d5c29SDavid Howells depends on !MMU 346fc4d5c29SDavid Howells default 1 347fc4d5c29SDavid Howells help 348fc4d5c29SDavid Howells The NOMMU mmap() frequently needs to allocate large contiguous chunks 349fc4d5c29SDavid Howells of memory on which to store mappings, but it can only ask the system 350fc4d5c29SDavid Howells allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 351fc4d5c29SDavid Howells more than it requires. To deal with this, mmap() is able to trim off 352fc4d5c29SDavid Howells the excess and return it to the allocator. 353fc4d5c29SDavid Howells 354fc4d5c29SDavid Howells If trimming is enabled, the excess is trimmed off and returned to the 355fc4d5c29SDavid Howells system allocator, which can cause extra fragmentation, particularly 356fc4d5c29SDavid Howells if there are a lot of transient processes. 357fc4d5c29SDavid Howells 358fc4d5c29SDavid Howells If trimming is disabled, the excess is kept, but not used, which for 359fc4d5c29SDavid Howells long-term mappings means that the space is wasted. 360fc4d5c29SDavid Howells 361fc4d5c29SDavid Howells Trimming can be dynamically controlled through a sysctl option 362fc4d5c29SDavid Howells (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 363fc4d5c29SDavid Howells excess pages there must be before trimming should occur, or zero if 364fc4d5c29SDavid Howells no trimming is to occur. 365fc4d5c29SDavid Howells 366fc4d5c29SDavid Howells This option specifies the initial value of this option. The default 367fc4d5c29SDavid Howells of 1 says that all excess pages should be trimmed. 368fc4d5c29SDavid Howells 369fc4d5c29SDavid Howells See Documentation/nommu-mmap.txt for more information. 370bbddff05STejun Heo 3714c76d9d1SAndrea Arcangeliconfig TRANSPARENT_HUGEPAGE 37213ece886SAndrea Arcangeli bool "Transparent Hugepage Support" 37315626062SGerald Schaefer depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 3745d689240SAndrea Arcangeli select COMPACTION 3753a08cd52SMatthew Wilcox select XARRAY_MULTI 3764c76d9d1SAndrea Arcangeli help 3774c76d9d1SAndrea Arcangeli Transparent Hugepages allows the kernel to use huge pages and 3784c76d9d1SAndrea Arcangeli huge tlb transparently to the applications whenever possible. 3794c76d9d1SAndrea Arcangeli This feature can improve computing performance to certain 3804c76d9d1SAndrea Arcangeli applications by speeding up page faults during memory 3814c76d9d1SAndrea Arcangeli allocation, by reducing the number of tlb misses and by speeding 3824c76d9d1SAndrea Arcangeli up the pagetable walking. 3834c76d9d1SAndrea Arcangeli 3844c76d9d1SAndrea Arcangeli If memory constrained on embedded, you may want to say N. 3854c76d9d1SAndrea Arcangeli 38613ece886SAndrea Arcangelichoice 38713ece886SAndrea Arcangeli prompt "Transparent Hugepage Support sysfs defaults" 38813ece886SAndrea Arcangeli depends on TRANSPARENT_HUGEPAGE 38913ece886SAndrea Arcangeli default TRANSPARENT_HUGEPAGE_ALWAYS 39013ece886SAndrea Arcangeli help 39113ece886SAndrea Arcangeli Selects the sysfs defaults for Transparent Hugepage Support. 39213ece886SAndrea Arcangeli 39313ece886SAndrea Arcangeli config TRANSPARENT_HUGEPAGE_ALWAYS 39413ece886SAndrea Arcangeli bool "always" 39513ece886SAndrea Arcangeli help 39613ece886SAndrea Arcangeli Enabling Transparent Hugepage always, can increase the 39713ece886SAndrea Arcangeli memory footprint of applications without a guaranteed 39813ece886SAndrea Arcangeli benefit but it will work automatically for all applications. 39913ece886SAndrea Arcangeli 40013ece886SAndrea Arcangeli config TRANSPARENT_HUGEPAGE_MADVISE 40113ece886SAndrea Arcangeli bool "madvise" 40213ece886SAndrea Arcangeli help 40313ece886SAndrea Arcangeli Enabling Transparent Hugepage madvise, will only provide a 40413ece886SAndrea Arcangeli performance improvement benefit to the applications using 40513ece886SAndrea Arcangeli madvise(MADV_HUGEPAGE) but it won't risk to increase the 40613ece886SAndrea Arcangeli memory footprint of applications without a guaranteed 40713ece886SAndrea Arcangeli benefit. 40813ece886SAndrea Arcangeliendchoice 40913ece886SAndrea Arcangeli 41038d8b4e6SHuang Yingconfig ARCH_WANTS_THP_SWAP 41138d8b4e6SHuang Ying def_bool n 41238d8b4e6SHuang Ying 41338d8b4e6SHuang Yingconfig THP_SWAP 41438d8b4e6SHuang Ying def_bool y 41514fef284SHuang Ying depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP 41638d8b4e6SHuang Ying help 41738d8b4e6SHuang Ying Swap transparent huge pages in one piece, without splitting. 41814fef284SHuang Ying XXX: For now, swap cluster backing transparent huge page 41914fef284SHuang Ying will be split after swapout. 42038d8b4e6SHuang Ying 42138d8b4e6SHuang Ying For selection by architectures with reasonable THP sizes. 42238d8b4e6SHuang Ying 423e496cf3dSKirill A. Shutemovconfig TRANSPARENT_HUGE_PAGECACHE 424e496cf3dSKirill A. Shutemov def_bool y 425953c66c2SAneesh Kumar K.V depends on TRANSPARENT_HUGEPAGE 426e496cf3dSKirill A. Shutemov 427e496cf3dSKirill A. Shutemov# 428bbddff05STejun Heo# UP and nommu archs use km based percpu allocator 429bbddff05STejun Heo# 430bbddff05STejun Heoconfig NEED_PER_CPU_KM 431bbddff05STejun Heo depends on !SMP 432bbddff05STejun Heo bool 433bbddff05STejun Heo default y 434077b1f83SDan Magenheimer 435077b1f83SDan Magenheimerconfig CLEANCACHE 436077b1f83SDan Magenheimer bool "Enable cleancache driver to cache clean pages if tmem is present" 437077b1f83SDan Magenheimer help 438077b1f83SDan Magenheimer Cleancache can be thought of as a page-granularity victim cache 439077b1f83SDan Magenheimer for clean pages that the kernel's pageframe replacement algorithm 440077b1f83SDan Magenheimer (PFRA) would like to keep around, but can't since there isn't enough 441077b1f83SDan Magenheimer memory. So when the PFRA "evicts" a page, it first attempts to use 442140a1ef2SMichael Witten cleancache code to put the data contained in that page into 443077b1f83SDan Magenheimer "transcendent memory", memory that is not directly accessible or 444077b1f83SDan Magenheimer addressable by the kernel and is of unknown and possibly 445077b1f83SDan Magenheimer time-varying size. And when a cleancache-enabled 446077b1f83SDan Magenheimer filesystem wishes to access a page in a file on disk, it first 447077b1f83SDan Magenheimer checks cleancache to see if it already contains it; if it does, 448077b1f83SDan Magenheimer the page is copied into the kernel and a disk access is avoided. 449077b1f83SDan Magenheimer When a transcendent memory driver is available (such as zcache or 450077b1f83SDan Magenheimer Xen transcendent memory), a significant I/O reduction 451077b1f83SDan Magenheimer may be achieved. When none is available, all cleancache calls 452077b1f83SDan Magenheimer are reduced to a single pointer-compare-against-NULL resulting 453077b1f83SDan Magenheimer in a negligible performance hit. 454077b1f83SDan Magenheimer 455077b1f83SDan Magenheimer If unsure, say Y to enable cleancache 45627c6aec2SDan Magenheimer 45727c6aec2SDan Magenheimerconfig FRONTSWAP 45827c6aec2SDan Magenheimer bool "Enable frontswap to cache swap pages if tmem is present" 45927c6aec2SDan Magenheimer depends on SWAP 46027c6aec2SDan Magenheimer help 46127c6aec2SDan Magenheimer Frontswap is so named because it can be thought of as the opposite 46227c6aec2SDan Magenheimer of a "backing" store for a swap device. The data is stored into 46327c6aec2SDan Magenheimer "transcendent memory", memory that is not directly accessible or 46427c6aec2SDan Magenheimer addressable by the kernel and is of unknown and possibly 46527c6aec2SDan Magenheimer time-varying size. When space in transcendent memory is available, 46627c6aec2SDan Magenheimer a significant swap I/O reduction may be achieved. When none is 46727c6aec2SDan Magenheimer available, all frontswap calls are reduced to a single pointer- 46827c6aec2SDan Magenheimer compare-against-NULL resulting in a negligible performance hit 46927c6aec2SDan Magenheimer and swap data is stored as normal on the matching swap device. 47027c6aec2SDan Magenheimer 47127c6aec2SDan Magenheimer If unsure, say Y to enable frontswap. 472f825c736SAneesh Kumar K.V 473f825c736SAneesh Kumar K.Vconfig CMA 474f825c736SAneesh Kumar K.V bool "Contiguous Memory Allocator" 475aca52c39SMike Rapoport depends on MMU 476f825c736SAneesh Kumar K.V select MIGRATION 477f825c736SAneesh Kumar K.V select MEMORY_ISOLATION 478f825c736SAneesh Kumar K.V help 479f825c736SAneesh Kumar K.V This enables the Contiguous Memory Allocator which allows other 480f825c736SAneesh Kumar K.V subsystems to allocate big physically-contiguous blocks of memory. 481f825c736SAneesh Kumar K.V CMA reserves a region of memory and allows only movable pages to 482f825c736SAneesh Kumar K.V be allocated from it. This way, the kernel can use the memory for 483f825c736SAneesh Kumar K.V pagecache and when a subsystem requests for contiguous area, the 484f825c736SAneesh Kumar K.V allocated pages are migrated away to serve the contiguous request. 485f825c736SAneesh Kumar K.V 486f825c736SAneesh Kumar K.V If unsure, say "n". 487f825c736SAneesh Kumar K.V 488f825c736SAneesh Kumar K.Vconfig CMA_DEBUG 489f825c736SAneesh Kumar K.V bool "CMA debug messages (DEVELOPMENT)" 490f825c736SAneesh Kumar K.V depends on DEBUG_KERNEL && CMA 491f825c736SAneesh Kumar K.V help 492f825c736SAneesh Kumar K.V Turns on debug messages in CMA. This produces KERN_DEBUG 493f825c736SAneesh Kumar K.V messages for every CMA call as well as various messages while 494f825c736SAneesh Kumar K.V processing calls such as dma_alloc_from_contiguous(). 495f825c736SAneesh Kumar K.V This option does not affect warning and error messages. 496bf550fc9SAlexander Graf 49728b24c1fSSasha Levinconfig CMA_DEBUGFS 49828b24c1fSSasha Levin bool "CMA debugfs interface" 49928b24c1fSSasha Levin depends on CMA && DEBUG_FS 50028b24c1fSSasha Levin help 50128b24c1fSSasha Levin Turns on the DebugFS interface for CMA. 50228b24c1fSSasha Levin 503a254129eSJoonsoo Kimconfig CMA_AREAS 504a254129eSJoonsoo Kim int "Maximum count of the CMA areas" 505a254129eSJoonsoo Kim depends on CMA 506a254129eSJoonsoo Kim default 7 507a254129eSJoonsoo Kim help 508a254129eSJoonsoo Kim CMA allows to create CMA areas for particular purpose, mainly, 509a254129eSJoonsoo Kim used as device private area. This parameter sets the maximum 510a254129eSJoonsoo Kim number of CMA area in the system. 511a254129eSJoonsoo Kim 512a254129eSJoonsoo Kim If unsure, leave the default value "7". 513a254129eSJoonsoo Kim 514af8d417aSDan Streetmanconfig MEM_SOFT_DIRTY 515af8d417aSDan Streetman bool "Track memory changes" 516af8d417aSDan Streetman depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 517af8d417aSDan Streetman select PROC_PAGE_MONITOR 5184e2e2770SSeth Jennings help 519af8d417aSDan Streetman This option enables memory changes tracking by introducing a 520af8d417aSDan Streetman soft-dirty bit on pte-s. This bit it set when someone writes 521af8d417aSDan Streetman into a page just as regular dirty bit, but unlike the latter 522af8d417aSDan Streetman it can be cleared by hands. 523af8d417aSDan Streetman 5241ad1335dSMike Rapoport See Documentation/admin-guide/mm/soft-dirty.rst for more details. 5254e2e2770SSeth Jennings 5262b281117SSeth Jenningsconfig ZSWAP 5272b281117SSeth Jennings bool "Compressed cache for swap pages (EXPERIMENTAL)" 5282b281117SSeth Jennings depends on FRONTSWAP && CRYPTO=y 5292b281117SSeth Jennings select CRYPTO_LZO 53012d79d64SDan Streetman select ZPOOL 5312b281117SSeth Jennings help 5322b281117SSeth Jennings A lightweight compressed cache for swap pages. It takes 5332b281117SSeth Jennings pages that are in the process of being swapped out and attempts to 5342b281117SSeth Jennings compress them into a dynamically allocated RAM-based memory pool. 5352b281117SSeth Jennings This can result in a significant I/O reduction on swap device and, 5362b281117SSeth Jennings in the case where decompressing from RAM is faster that swap device 5372b281117SSeth Jennings reads, can also improve workload performance. 5382b281117SSeth Jennings 5392b281117SSeth Jennings This is marked experimental because it is a new feature (as of 5402b281117SSeth Jennings v3.11) that interacts heavily with memory reclaim. While these 5412b281117SSeth Jennings interactions don't cause any known issues on simple memory setups, 5422b281117SSeth Jennings they have not be fully explored on the large set of potential 5432b281117SSeth Jennings configurations and workloads that exist. 5442b281117SSeth Jennings 545af8d417aSDan Streetmanconfig ZPOOL 546af8d417aSDan Streetman tristate "Common API for compressed memory storage" 5470f8975ecSPavel Emelyanov help 548af8d417aSDan Streetman Compressed memory storage API. This allows using either zbud or 549af8d417aSDan Streetman zsmalloc. 5500f8975ecSPavel Emelyanov 551af8d417aSDan Streetmanconfig ZBUD 5529a001fc1SVitaly Wool tristate "Low (Up to 2x) density storage for compressed pages" 553af8d417aSDan Streetman help 554af8d417aSDan Streetman A special purpose allocator for storing compressed pages. 555af8d417aSDan Streetman It is designed to store up to two compressed pages per physical 556af8d417aSDan Streetman page. While this design limits storage density, it has simple and 557af8d417aSDan Streetman deterministic reclaim properties that make it preferable to a higher 558af8d417aSDan Streetman density approach when reclaim will be used. 559bcf1647dSMinchan Kim 5609a001fc1SVitaly Woolconfig Z3FOLD 5619a001fc1SVitaly Wool tristate "Up to 3x density storage for compressed pages" 5629a001fc1SVitaly Wool depends on ZPOOL 5639a001fc1SVitaly Wool help 5649a001fc1SVitaly Wool A special purpose allocator for storing compressed pages. 5659a001fc1SVitaly Wool It is designed to store up to three compressed pages per physical 5669a001fc1SVitaly Wool page. It is a ZBUD derivative so the simplicity and determinism are 5679a001fc1SVitaly Wool still there. 5689a001fc1SVitaly Wool 569bcf1647dSMinchan Kimconfig ZSMALLOC 570d867f203SMinchan Kim tristate "Memory allocator for compressed pages" 571bcf1647dSMinchan Kim depends on MMU 572bcf1647dSMinchan Kim help 573bcf1647dSMinchan Kim zsmalloc is a slab-based memory allocator designed to store 574bcf1647dSMinchan Kim compressed RAM pages. zsmalloc uses virtual memory mapping 575bcf1647dSMinchan Kim in order to reduce fragmentation. However, this results in a 576bcf1647dSMinchan Kim non-standard allocator interface where a handle, not a pointer, is 577bcf1647dSMinchan Kim returned by an alloc(). This handle must be mapped in order to 578bcf1647dSMinchan Kim access the allocated space. 579bcf1647dSMinchan Kim 580bcf1647dSMinchan Kimconfig PGTABLE_MAPPING 581bcf1647dSMinchan Kim bool "Use page table mapping to access object in zsmalloc" 582bcf1647dSMinchan Kim depends on ZSMALLOC 583bcf1647dSMinchan Kim help 584bcf1647dSMinchan Kim By default, zsmalloc uses a copy-based object mapping method to 585bcf1647dSMinchan Kim access allocations that span two pages. However, if a particular 586bcf1647dSMinchan Kim architecture (ex, ARM) performs VM mapping faster than copying, 587bcf1647dSMinchan Kim then you should select this. This causes zsmalloc to use page table 588bcf1647dSMinchan Kim mapping rather than copying for object mapping. 589bcf1647dSMinchan Kim 5902216ee85SBen Hutchings You can check speed with zsmalloc benchmark: 5912216ee85SBen Hutchings https://github.com/spartacus06/zsmapbench 5929e5c33d7SMark Salter 5930f050d99SGanesh Mahendranconfig ZSMALLOC_STAT 5940f050d99SGanesh Mahendran bool "Export zsmalloc statistics" 5950f050d99SGanesh Mahendran depends on ZSMALLOC 5960f050d99SGanesh Mahendran select DEBUG_FS 5970f050d99SGanesh Mahendran help 5980f050d99SGanesh Mahendran This option enables code in the zsmalloc to collect various 5990f050d99SGanesh Mahendran statistics about whats happening in zsmalloc and exports that 6000f050d99SGanesh Mahendran information to userspace via debugfs. 6010f050d99SGanesh Mahendran If unsure, say N. 6020f050d99SGanesh Mahendran 6039e5c33d7SMark Salterconfig GENERIC_EARLY_IOREMAP 6049e5c33d7SMark Salter bool 605042d27acSHelge Deller 606042d27acSHelge Dellerconfig MAX_STACK_SIZE_MB 607042d27acSHelge Deller int "Maximum user stack size for 32-bit processes (MB)" 608042d27acSHelge Deller default 80 609042d27acSHelge Deller range 8 2048 610042d27acSHelge Deller depends on STACK_GROWSUP && (!64BIT || COMPAT) 611042d27acSHelge Deller help 612042d27acSHelge Deller This is the maximum stack size in Megabytes in the VM layout of 32-bit 613042d27acSHelge Deller user processes when the stack grows upwards (currently only on parisc 6145f171577SJames Hogan arch). The stack will be located at the highest memory address minus 6155f171577SJames Hogan the given value, unless the RLIMIT_STACK hard limit is changed to a 6165f171577SJames Hogan smaller value in which case that is used. 617042d27acSHelge Deller 618042d27acSHelge Deller A sane initial value is 80 MB. 6193a80a7faSMel Gorman 6203a80a7faSMel Gormanconfig DEFERRED_STRUCT_PAGE_INIT 6211ce22103SVlastimil Babka bool "Defer initialisation of struct pages to kthreads" 622d39f8fb4SMike Rapoport depends on SPARSEMEM 623ab1e8d89SPavel Tatashin depends on !NEED_PER_CPU_KM 624889c695dSPasha Tatashin depends on 64BIT 6253a80a7faSMel Gorman help 6263a80a7faSMel Gorman Ordinarily all struct pages are initialised during early boot in a 6273a80a7faSMel Gorman single thread. On very large machines this can take a considerable 6283a80a7faSMel Gorman amount of time. If this option is set, large machines will bring up 6293a80a7faSMel Gorman a subset of memmap at boot and then initialise the rest in parallel 6301ce22103SVlastimil Babka by starting one-off "pgdatinitX" kernel thread for each node X. This 6311ce22103SVlastimil Babka has a potential performance impact on processes running early in the 6321ce22103SVlastimil Babka lifetime of the system until these kthreads finish the 6331ce22103SVlastimil Babka initialisation. 634033fbae9SDan Williams 63533c3fc71SVladimir Davydovconfig IDLE_PAGE_TRACKING 63633c3fc71SVladimir Davydov bool "Enable idle page tracking" 63733c3fc71SVladimir Davydov depends on SYSFS && MMU 63833c3fc71SVladimir Davydov select PAGE_EXTENSION if !64BIT 63933c3fc71SVladimir Davydov help 64033c3fc71SVladimir Davydov This feature allows to estimate the amount of user pages that have 64133c3fc71SVladimir Davydov not been touched during a given period of time. This information can 64233c3fc71SVladimir Davydov be useful to tune memory cgroup limits and/or for job placement 64333c3fc71SVladimir Davydov within a compute cluster. 64433c3fc71SVladimir Davydov 6451ad1335dSMike Rapoport See Documentation/admin-guide/mm/idle_page_tracking.rst for 6461ad1335dSMike Rapoport more details. 64733c3fc71SVladimir Davydov 64817596731SRobin Murphyconfig ARCH_HAS_PTE_DEVMAP 64965f7d049SOliver O'Halloran bool 65065f7d049SOliver O'Halloran 651033fbae9SDan Williamsconfig ZONE_DEVICE 6525042db43SJérôme Glisse bool "Device memory (pmem, HMM, etc...) hotplug support" 653033fbae9SDan Williams depends on MEMORY_HOTPLUG 654033fbae9SDan Williams depends on MEMORY_HOTREMOVE 65599490f16SDan Williams depends on SPARSEMEM_VMEMMAP 65617596731SRobin Murphy depends on ARCH_HAS_PTE_DEVMAP 6573a08cd52SMatthew Wilcox select XARRAY_MULTI 658033fbae9SDan Williams 659033fbae9SDan Williams help 660033fbae9SDan Williams Device memory hotplug support allows for establishing pmem, 661033fbae9SDan Williams or other device driver discovered memory regions, in the 662033fbae9SDan Williams memmap. This allows pfn_to_page() lookups of otherwise 663033fbae9SDan Williams "device-physical" addresses which is needed for using a DAX 664033fbae9SDan Williams mapping in an O_DIRECT operation, among other things. 665033fbae9SDan Williams 666033fbae9SDan Williams If FS_DAX is enabled, then say Y. 66706a660adSLinus Torvalds 668e7638488SDan Williamsconfig DEV_PAGEMAP_OPS 669e7638488SDan Williams bool 670e7638488SDan Williams 6719c240a7bSChristoph Hellwig# 6729c240a7bSChristoph Hellwig# Helpers to mirror range of the CPU page tables of a process into device page 6739c240a7bSChristoph Hellwig# tables. 6749c240a7bSChristoph Hellwig# 675c0b12405SJérôme Glisseconfig HMM_MIRROR 6769c240a7bSChristoph Hellwig bool 677f442c283SChristoph Hellwig depends on MMU 678c0b12405SJérôme Glisse 6795042db43SJérôme Glisseconfig DEVICE_PRIVATE 6805042db43SJérôme Glisse bool "Unaddressable device memory (GPU memory, ...)" 6817328d9ccSChristoph Hellwig depends on ZONE_DEVICE 682e7638488SDan Williams select DEV_PAGEMAP_OPS 6835042db43SJérôme Glisse 6845042db43SJérôme Glisse help 6855042db43SJérôme Glisse Allows creation of struct pages to represent unaddressable device 6865042db43SJérôme Glisse memory; i.e., memory that is only accessible from the device (or 6875042db43SJérôme Glisse group of devices). You likely also want to select HMM_MIRROR. 6885042db43SJérôme Glisse 6898025e5ddSJan Karaconfig FRAME_VECTOR 6908025e5ddSJan Kara bool 69163c17fb8SDave Hansen 69263c17fb8SDave Hansenconfig ARCH_USES_HIGH_VMA_FLAGS 69363c17fb8SDave Hansen bool 69466d37570SDave Hansenconfig ARCH_HAS_PKEYS 69566d37570SDave Hansen bool 69630a5b536SDennis Zhou 69730a5b536SDennis Zhouconfig PERCPU_STATS 69830a5b536SDennis Zhou bool "Collect percpu memory statistics" 69930a5b536SDennis Zhou help 70030a5b536SDennis Zhou This feature collects and exposes statistics via debugfs. The 70130a5b536SDennis Zhou information includes global and per chunk statistics, which can 70230a5b536SDennis Zhou be used to help understand percpu memory usage. 70364c349f4SKirill A. Shutemov 70464c349f4SKirill A. Shutemovconfig GUP_BENCHMARK 70564c349f4SKirill A. Shutemov bool "Enable infrastructure for get_user_pages_fast() benchmarking" 70664c349f4SKirill A. Shutemov help 70764c349f4SKirill A. Shutemov Provides /sys/kernel/debug/gup_benchmark that helps with testing 70864c349f4SKirill A. Shutemov performance of get_user_pages_fast(). 70964c349f4SKirill A. Shutemov 71064c349f4SKirill A. Shutemov See tools/testing/selftests/vm/gup_benchmark.c 7113010a5eaSLaurent Dufour 71239656e83SChristoph Hellwigconfig GUP_GET_PTE_LOW_HIGH 71339656e83SChristoph Hellwig bool 71439656e83SChristoph Hellwig 71599cb0dbdSSong Liuconfig READ_ONLY_THP_FOR_FS 71699cb0dbdSSong Liu bool "Read-only THP for filesystems (EXPERIMENTAL)" 71799cb0dbdSSong Liu depends on TRANSPARENT_HUGE_PAGECACHE && SHMEM 71899cb0dbdSSong Liu 71999cb0dbdSSong Liu help 72099cb0dbdSSong Liu Allow khugepaged to put read-only file-backed pages in THP. 72199cb0dbdSSong Liu 72299cb0dbdSSong Liu This is marked experimental because it is a new feature. Write 72399cb0dbdSSong Liu support of file THPs will be developed in the next few release 72499cb0dbdSSong Liu cycles. 72599cb0dbdSSong Liu 7263010a5eaSLaurent Dufourconfig ARCH_HAS_PTE_SPECIAL 7273010a5eaSLaurent Dufour bool 72859e0b520SChristoph Hellwig 729cbd34da7SChristoph Hellwig# 730cbd34da7SChristoph Hellwig# Some architectures require a special hugepage directory format that is 731cbd34da7SChristoph Hellwig# required to support multiple hugepage sizes. For example a4fe3ce76 732cbd34da7SChristoph Hellwig# "powerpc/mm: Allow more flexible layouts for hugepage pagetables" 733cbd34da7SChristoph Hellwig# introduced it on powerpc. This allows for a more flexible hugepage 734cbd34da7SChristoph Hellwig# pagetable layouts. 735cbd34da7SChristoph Hellwig# 736cbd34da7SChristoph Hellwigconfig ARCH_HAS_HUGEPD 737cbd34da7SChristoph Hellwig bool 738cbd34da7SChristoph Hellwig 739c5acad84SThomas Hellstromconfig MAPPING_DIRTY_HELPERS 740c5acad84SThomas Hellstrom bool 741c5acad84SThomas Hellstrom 74259e0b520SChristoph Hellwigendmenu 743