508 lines
17 KiB
Plaintext
508 lines
17 KiB
Plaintext
config SELECT_MEMORY_MODEL
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def_bool y
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depends on ARCH_SELECT_MEMORY_MODEL
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choice
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prompt "Memory model"
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depends on SELECT_MEMORY_MODEL
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default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
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default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
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default FLATMEM_MANUAL
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config FLATMEM_MANUAL
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bool "Flat Memory"
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depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
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help
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This option allows you to change some of the ways that
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Linux manages its memory internally. Most users will
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only have one option here: FLATMEM. This is normal
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and a correct option.
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Some users of more advanced features like NUMA and
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memory hotplug may have different options here.
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DISCONTIGMEM is an more mature, better tested system,
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but is incompatible with memory hotplug and may suffer
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decreased performance over SPARSEMEM. If unsure between
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"Sparse Memory" and "Discontiguous Memory", choose
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"Discontiguous Memory".
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If unsure, choose this option (Flat Memory) over any other.
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config DISCONTIGMEM_MANUAL
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bool "Discontiguous Memory"
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depends on ARCH_DISCONTIGMEM_ENABLE
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help
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This option provides enhanced support for discontiguous
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memory systems, over FLATMEM. These systems have holes
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in their physical address spaces, and this option provides
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more efficient handling of these holes. However, the vast
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majority of hardware has quite flat address spaces, and
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can have degraded performance from the extra overhead that
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this option imposes.
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Many NUMA configurations will have this as the only option.
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If unsure, choose "Flat Memory" over this option.
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config SPARSEMEM_MANUAL
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bool "Sparse Memory"
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depends on ARCH_SPARSEMEM_ENABLE
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help
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This will be the only option for some systems, including
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memory hotplug systems. This is normal.
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For many other systems, this will be an alternative to
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"Discontiguous Memory". This option provides some potential
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performance benefits, along with decreased code complexity,
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but it is newer, and more experimental.
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If unsure, choose "Discontiguous Memory" or "Flat Memory"
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over this option.
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endchoice
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config DISCONTIGMEM
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def_bool y
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depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
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config SPARSEMEM
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def_bool y
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depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
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config FLATMEM
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def_bool y
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depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
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config FLAT_NODE_MEM_MAP
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def_bool y
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depends on !SPARSEMEM
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#
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# Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
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# to represent different areas of memory. This variable allows
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# those dependencies to exist individually.
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#
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config NEED_MULTIPLE_NODES
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def_bool y
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depends on DISCONTIGMEM || NUMA
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config HAVE_MEMORY_PRESENT
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def_bool y
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depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
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#
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# SPARSEMEM_EXTREME (which is the default) does some bootmem
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# allocations when memory_present() is called. If this cannot
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# be done on your architecture, select this option. However,
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# statically allocating the mem_section[] array can potentially
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# consume vast quantities of .bss, so be careful.
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#
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# This option will also potentially produce smaller runtime code
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# with gcc 3.4 and later.
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#
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config SPARSEMEM_STATIC
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bool
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#
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# Architecture platforms which require a two level mem_section in SPARSEMEM
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# must select this option. This is usually for architecture platforms with
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# an extremely sparse physical address space.
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#
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config SPARSEMEM_EXTREME
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def_bool y
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depends on SPARSEMEM && !SPARSEMEM_STATIC
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config SPARSEMEM_VMEMMAP_ENABLE
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bool
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config SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
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def_bool y
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depends on SPARSEMEM && X86_64
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config SPARSEMEM_VMEMMAP
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bool "Sparse Memory virtual memmap"
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depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
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default y
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help
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SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
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pfn_to_page and page_to_pfn operations. This is the most
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efficient option when sufficient kernel resources are available.
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config HAVE_MEMBLOCK
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boolean
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config HAVE_MEMBLOCK_NODE_MAP
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boolean
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config ARCH_DISCARD_MEMBLOCK
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boolean
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config NO_BOOTMEM
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boolean
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config MEMORY_ISOLATION
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boolean
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config MOVABLE_NODE
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boolean "Enable to assign a node which has only movable memory"
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depends on HAVE_MEMBLOCK
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depends on NO_BOOTMEM
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depends on X86_64
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depends on NUMA
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default n
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help
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Allow a node to have only movable memory. Pages used by the kernel,
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such as direct mapping pages cannot be migrated. So the corresponding
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memory device cannot be hotplugged. This option allows users to
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online all the memory of a node as movable memory so that the whole
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node can be hotplugged. Users who don't use the memory hotplug
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feature are fine with this option on since they don't online memory
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as movable.
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Say Y here if you want to hotplug a whole node.
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Say N here if you want kernel to use memory on all nodes evenly.
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#
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# Only be set on architectures that have completely implemented memory hotplug
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# feature. If you are not sure, don't touch it.
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#
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config HAVE_BOOTMEM_INFO_NODE
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def_bool n
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# eventually, we can have this option just 'select SPARSEMEM'
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config MEMORY_HOTPLUG
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bool "Allow for memory hot-add"
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depends on SPARSEMEM || X86_64_ACPI_NUMA
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depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG
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depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
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config MEMORY_HOTPLUG_SPARSE
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def_bool y
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depends on SPARSEMEM && MEMORY_HOTPLUG
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config MEMORY_HOTREMOVE
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bool "Allow for memory hot remove"
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select MEMORY_ISOLATION
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select HAVE_BOOTMEM_INFO_NODE if X86_64
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depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
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depends on MIGRATION
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#
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# If we have space for more page flags then we can enable additional
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# optimizations and functionality.
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#
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# Regular Sparsemem takes page flag bits for the sectionid if it does not
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# use a virtual memmap. Disable extended page flags for 32 bit platforms
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# that require the use of a sectionid in the page flags.
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#
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config PAGEFLAGS_EXTENDED
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def_bool y
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depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
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# Heavily threaded applications may benefit from splitting the mm-wide
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# page_table_lock, so that faults on different parts of the user address
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# space can be handled with less contention: split it at this NR_CPUS.
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# Default to 4 for wider testing, though 8 might be more appropriate.
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# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
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# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
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# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
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#
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config SPLIT_PTLOCK_CPUS
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int
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default "999999" if ARM && !CPU_CACHE_VIPT
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default "999999" if PARISC && !PA20
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default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
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default "4"
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#
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# support for memory balloon compaction
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config BALLOON_COMPACTION
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bool "Allow for balloon memory compaction/migration"
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def_bool y
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depends on COMPACTION && VIRTIO_BALLOON
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help
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Memory fragmentation introduced by ballooning might reduce
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significantly the number of 2MB contiguous memory blocks that can be
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used within a guest, thus imposing performance penalties associated
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with the reduced number of transparent huge pages that could be used
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by the guest workload. Allowing the compaction & migration for memory
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pages enlisted as being part of memory balloon devices avoids the
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scenario aforementioned and helps improving memory defragmentation.
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#
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# support for memory compaction
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config COMPACTION
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bool "Allow for memory compaction"
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def_bool y
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select MIGRATION
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depends on MMU
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help
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Allows the compaction of memory for the allocation of huge pages.
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#
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# support for page migration
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#
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config MIGRATION
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bool "Page migration"
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def_bool y
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depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA
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help
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Allows the migration of the physical location of pages of processes
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while the virtual addresses are not changed. This is useful in
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two situations. The first is on NUMA systems to put pages nearer
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to the processors accessing. The second is when allocating huge
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pages as migration can relocate pages to satisfy a huge page
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allocation instead of reclaiming.
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config PHYS_ADDR_T_64BIT
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def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
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config ZONE_DMA_FLAG
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int
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default "0" if !ZONE_DMA
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default "1"
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config BOUNCE
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bool "Enable bounce buffers"
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default y
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depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
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help
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Enable bounce buffers for devices that cannot access
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the full range of memory available to the CPU. Enabled
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by default when ZONE_DMA or HIGHMEM is selected, but you
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may say n to override this.
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# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
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# have more than 4GB of memory, but we don't currently use the IOTLB to present
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# a 32-bit address to OHCI. So we need to use a bounce pool instead.
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#
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# We also use the bounce pool to provide stable page writes for jbd. jbd
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# initiates buffer writeback without locking the page or setting PG_writeback,
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# and fixing that behavior (a second time; jbd2 doesn't have this problem) is
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# a major rework effort. Instead, use the bounce buffer to snapshot pages
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# (until jbd goes away). The only jbd user is ext3.
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config NEED_BOUNCE_POOL
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bool
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default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD)
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config NR_QUICK
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int
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depends on QUICKLIST
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default "2" if AVR32
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default "1"
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config VIRT_TO_BUS
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bool
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help
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An architecture should select this if it implements the
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deprecated interface virt_to_bus(). All new architectures
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should probably not select this.
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config MMU_NOTIFIER
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bool
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config KSM
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bool "Enable KSM for page merging"
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depends on MMU
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help
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Enable Kernel Samepage Merging: KSM periodically scans those areas
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of an application's address space that an app has advised may be
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mergeable. When it finds pages of identical content, it replaces
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the many instances by a single page with that content, so
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saving memory until one or another app needs to modify the content.
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Recommended for use with KVM, or with other duplicative applications.
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See Documentation/vm/ksm.txt for more information: KSM is inactive
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until a program has madvised that an area is MADV_MERGEABLE, and
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root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
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config DEFAULT_MMAP_MIN_ADDR
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int "Low address space to protect from user allocation"
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depends on MMU
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default 4096
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help
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This is the portion of low virtual memory which should be protected
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from userspace allocation. Keeping a user from writing to low pages
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can help reduce the impact of kernel NULL pointer bugs.
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For most ia64, ppc64 and x86 users with lots of address space
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a value of 65536 is reasonable and should cause no problems.
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On arm and other archs it should not be higher than 32768.
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Programs which use vm86 functionality or have some need to map
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this low address space will need CAP_SYS_RAWIO or disable this
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protection by setting the value to 0.
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This value can be changed after boot using the
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/proc/sys/vm/mmap_min_addr tunable.
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config MMAP_NOEXEC_TAINT
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int "Turns on tainting of mmap()d files from noexec mountpoints"
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depends on MMU
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default 1
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help
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By default, the ability to change the protections of a virtual
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memory area to allow execution depend on if the vma has the
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VM_MAYEXEC flag. When mapping regions from files, VM_MAYEXEC
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will be unset if the containing mountpoint is mounted MNT_NOEXEC.
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By setting the value to 0, any mmap()d region may be later
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mprotect()d with PROT_EXEC.
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If unsure, keep the value set to 1.
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This value can be changed after boot using the
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/proc/sys/vm/mmap_noexec_taint tunable.
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config ARCH_SUPPORTS_MEMORY_FAILURE
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bool
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config MEMORY_FAILURE
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depends on MMU
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depends on ARCH_SUPPORTS_MEMORY_FAILURE
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bool "Enable recovery from hardware memory errors"
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select MEMORY_ISOLATION
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help
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Enables code to recover from some memory failures on systems
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with MCA recovery. This allows a system to continue running
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even when some of its memory has uncorrected errors. This requires
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special hardware support and typically ECC memory.
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config HWPOISON_INJECT
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tristate "HWPoison pages injector"
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depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
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select PROC_PAGE_MONITOR
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config NOMMU_INITIAL_TRIM_EXCESS
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int "Turn on mmap() excess space trimming before booting"
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depends on !MMU
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default 1
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help
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The NOMMU mmap() frequently needs to allocate large contiguous chunks
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of memory on which to store mappings, but it can only ask the system
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allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
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more than it requires. To deal with this, mmap() is able to trim off
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the excess and return it to the allocator.
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If trimming is enabled, the excess is trimmed off and returned to the
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system allocator, which can cause extra fragmentation, particularly
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if there are a lot of transient processes.
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If trimming is disabled, the excess is kept, but not used, which for
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long-term mappings means that the space is wasted.
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Trimming can be dynamically controlled through a sysctl option
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(/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
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excess pages there must be before trimming should occur, or zero if
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no trimming is to occur.
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This option specifies the initial value of this option. The default
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of 1 says that all excess pages should be trimmed.
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See Documentation/nommu-mmap.txt for more information.
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config TRANSPARENT_HUGEPAGE
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bool "Transparent Hugepage Support"
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depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
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select COMPACTION
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help
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Transparent Hugepages allows the kernel to use huge pages and
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huge tlb transparently to the applications whenever possible.
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This feature can improve computing performance to certain
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applications by speeding up page faults during memory
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allocation, by reducing the number of tlb misses and by speeding
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up the pagetable walking.
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If memory constrained on embedded, you may want to say N.
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choice
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prompt "Transparent Hugepage Support sysfs defaults"
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depends on TRANSPARENT_HUGEPAGE
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default TRANSPARENT_HUGEPAGE_ALWAYS
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help
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Selects the sysfs defaults for Transparent Hugepage Support.
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config TRANSPARENT_HUGEPAGE_ALWAYS
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bool "always"
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help
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Enabling Transparent Hugepage always, can increase the
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memory footprint of applications without a guaranteed
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benefit but it will work automatically for all applications.
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config TRANSPARENT_HUGEPAGE_MADVISE
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bool "madvise"
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help
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Enabling Transparent Hugepage madvise, will only provide a
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performance improvement benefit to the applications using
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madvise(MADV_HUGEPAGE) but it won't risk to increase the
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memory footprint of applications without a guaranteed
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benefit.
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endchoice
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config CROSS_MEMORY_ATTACH
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bool "Cross Memory Support"
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depends on MMU
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default y
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help
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Enabling this option adds the system calls process_vm_readv and
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process_vm_writev which allow a process with the correct privileges
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to directly read from or write to to another process's address space.
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See the man page for more details.
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#
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# UP and nommu archs use km based percpu allocator
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#
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config NEED_PER_CPU_KM
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depends on !SMP
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bool
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default y
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config CLEANCACHE
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bool "Enable cleancache driver to cache clean pages if tmem is present"
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default n
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help
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Cleancache can be thought of as a page-granularity victim cache
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for clean pages that the kernel's pageframe replacement algorithm
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(PFRA) would like to keep around, but can't since there isn't enough
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memory. So when the PFRA "evicts" a page, it first attempts to use
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cleancache code to put the data contained in that page into
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"transcendent memory", memory that is not directly accessible or
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addressable by the kernel and is of unknown and possibly
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time-varying size. And when a cleancache-enabled
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filesystem wishes to access a page in a file on disk, it first
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checks cleancache to see if it already contains it; if it does,
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the page is copied into the kernel and a disk access is avoided.
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When a transcendent memory driver is available (such as zcache or
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Xen transcendent memory), a significant I/O reduction
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may be achieved. When none is available, all cleancache calls
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are reduced to a single pointer-compare-against-NULL resulting
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in a negligible performance hit.
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If unsure, say Y to enable cleancache
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config FRONTSWAP
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bool "Enable frontswap to cache swap pages if tmem is present"
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depends on SWAP
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default n
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help
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Frontswap is so named because it can be thought of as the opposite
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of a "backing" store for a swap device. The data is stored into
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"transcendent memory", memory that is not directly accessible or
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addressable by the kernel and is of unknown and possibly
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time-varying size. When space in transcendent memory is available,
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a significant swap I/O reduction may be achieved. When none is
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available, all frontswap calls are reduced to a single pointer-
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compare-against-NULL resulting in a negligible performance hit
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and swap data is stored as normal on the matching swap device.
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If unsure, say Y to enable frontswap.
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config LOW_MEM_NOTIFY
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bool "Create device that lets processes detect low-memory conditions"
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default n
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help
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A process can poll the /dev/low_mem device to be notified of
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low-memory conditions. The process can then attempt to free memory
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before a OOM condition develops and the OOM killer takes over. This
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is meant to be used in systems with no or very little swap space. In
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the presence of large swap space, the system is likely to become
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unusable before the OOM killer is triggered.
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