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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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e20b8cca76
Having separate page flags for the head and the tail of a compound page allows the compiler to use bitops instead of operations on a word to check for a tail page. That is f.e. important for virt_to_head_page() which is used in various critical code paths (kfree for example): Code for PageTail(page) Before: mov (%rdi),%rdx page->flags mov %rdx,%rax 3 bytes and $0x12000,%eax 5 bytes cmp $0x12000,%rax 6 bytes je 897 <kfree+0xa7> After: mov (%rdi),%rax test $0x40,%ah (3 bytes) jne 887 <kfree+0x97> So we go from 14 bytes to 3 bytes and from 3 instructions to one. From the use of 2 registers we go to none. We can only use page flags for this if we have page flags available. This patch introduces CONFIG_PAGEFLAGS_EXTENDED that is set if pageflags are not scarce due to SPARSEMEM using page flags for its sectionid on 32 bit NUMA platforms. Additional page flag definitions can be added to the CONFIG_PAGEFLAGS_EXTENDED section in page-flags.h if the functionality depends on PAGEFLAGS_EXTENDED or if more page flag overlapping tricks are used for the !PAGEFLAGS_EXTENDED fallback (the upcoming virtual compound patch may hook in here and Rik's/Lee's additional page flags to solve the reclaim issues could also be added there [hint... hint... where are these patchsets?]). Avoiding the overlaying of Pg_reclaim also clears the way for possible use of compound pages for the pagecache or on the LRU. Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
208 lines
6.2 KiB
Plaintext
208 lines
6.2 KiB
Plaintext
config SELECT_MEMORY_MODEL
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def_bool y
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depends on EXPERIMENTAL || 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 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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def_bool n
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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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def_bool n
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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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# 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 && !HIBERNATION && ARCH_ENABLE_MEMORY_HOTPLUG
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depends on (IA64 || X86 || PPC64 || SUPERH)
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comment "Memory hotplug is currently incompatible with Software Suspend"
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depends on SPARSEMEM && HOTPLUG && HIBERNATION
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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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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 || !NUMA || !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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#
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config SPLIT_PTLOCK_CPUS
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int
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default "4096" if ARM && !CPU_CACHE_VIPT
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default "4096" if PARISC && !PA20
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default "4"
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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
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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 for
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example on NUMA systems to put pages nearer to the processors accessing
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the page.
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config RESOURCES_64BIT
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bool "64 bit Memory and IO resources (EXPERIMENTAL)" if (!64BIT && EXPERIMENTAL)
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default 64BIT
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help
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This option allows memory and IO resources to be 64 bit.
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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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def_bool y
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depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
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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 SUPERH
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default "1"
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config VIRT_TO_BUS
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def_bool y
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depends on !ARCH_NO_VIRT_TO_BUS
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