kconfig

linux 内核源代码

	  has the cost of more pagetable lookup overhead, and also
	  consumes more pagetable space per process.

# Common NUMA Features
config NUMA
	bool "Numa Memory Allocation and Scheduler Support (EXPERIMENTAL)"
	depends on SMP
	depends on X86_64 || (X86_32 && HIGHMEM64G && (X86_NUMAQ || (X86_SUMMIT || X86_GENERICARCH) && ACPI) && EXPERIMENTAL)
	default n if X86_PC
	default y if (X86_NUMAQ || X86_SUMMIT)
	help
	  Enable NUMA (Non Uniform Memory Access) support.
	  The kernel will try to allocate memory used by a CPU on the
	  local memory controller of the CPU and add some more
	  NUMA awareness to the kernel.

	  For i386 this is currently highly experimental and should be only
	  used for kernel development. It might also cause boot failures.
	  For x86_64 this is recommended on all multiprocessor Opteron systems.
	  If the system is EM64T, you should say N unless your system is
	  EM64T NUMA.

comment "NUMA (Summit) requires SMP, 64GB highmem support, ACPI"
	depends on X86_32 && X86_SUMMIT && (!HIGHMEM64G || !ACPI)

config K8_NUMA
       bool "Old style AMD Opteron NUMA detection"
       depends on X86_64 && NUMA && PCI
       default y
       help
	 Enable K8 NUMA node topology detection.  You should say Y here if
	 you have a multi processor AMD K8 system. This uses an old
	 method to read the NUMA configuration directly from the builtin
	 Northbridge of Opteron. It is recommended to use X86_64_ACPI_NUMA
	 instead, which also takes priority if both are compiled in.

config X86_64_ACPI_NUMA
	bool "ACPI NUMA detection"
	depends on X86_64 && NUMA && ACPI && PCI
	select ACPI_NUMA
	default y
	help
	  Enable ACPI SRAT based node topology detection.

config NUMA_EMU
	bool "NUMA emulation"
	depends on X86_64 && NUMA
	help
	  Enable NUMA emulation. A flat machine will be split
	  into virtual nodes when booted with "numa=fake=N", where N is the
	  number of nodes. This is only useful for debugging.

config NODES_SHIFT
	int
	default "6" if X86_64
	default "4" if X86_NUMAQ
	default "3"
	depends on NEED_MULTIPLE_NODES

config HAVE_ARCH_BOOTMEM_NODE
	bool
	depends on X86_32 && NUMA
	default y

config ARCH_HAVE_MEMORY_PRESENT
	bool
	depends on X86_32 && DISCONTIGMEM
	default y

config NEED_NODE_MEMMAP_SIZE
	bool
	depends on X86_32 && (DISCONTIGMEM || SPARSEMEM)
	default y

config HAVE_ARCH_ALLOC_REMAP
	bool
	depends on X86_32 && NUMA
	default y

config ARCH_FLATMEM_ENABLE
	def_bool y
	depends on (X86_32 && ARCH_SELECT_MEMORY_MODEL && X86_PC) || (X86_64 && !NUMA)

config ARCH_DISCONTIGMEM_ENABLE
	def_bool y
	depends on NUMA

config ARCH_DISCONTIGMEM_DEFAULT
	def_bool y
	depends on NUMA

config ARCH_SPARSEMEM_ENABLE
	def_bool y
	depends on NUMA || (EXPERIMENTAL && (X86_PC || X86_64))
	select SPARSEMEM_STATIC if X86_32
	select SPARSEMEM_VMEMMAP_ENABLE if X86_64

config ARCH_SELECT_MEMORY_MODEL
	def_bool y
	depends on X86_32 && ARCH_SPARSEMEM_ENABLE

config ARCH_MEMORY_PROBE
	def_bool X86_64
	depends on MEMORY_HOTPLUG

source "mm/Kconfig"

config HIGHPTE
	bool "Allocate 3rd-level pagetables from highmem"
	depends on X86_32 && (HIGHMEM4G || HIGHMEM64G)
	help
	  The VM uses one page table entry for each page of physical memory.
	  For systems with a lot of RAM, this can be wasteful of precious
	  low memory.  Setting this option will put user-space page table
	  entries in high memory.

config MATH_EMULATION
	bool
	prompt "Math emulation" if X86_32
	---help---
	  Linux can emulate a math coprocessor (used for floating point
	  operations) if you don't have one. 486DX and Pentium processors have
	  a math coprocessor built in, 486SX and 386 do not, unless you added
	  a 487DX or 387, respectively. (The messages during boot time can
	  give you some hints here ["man dmesg"].) Everyone needs either a
	  coprocessor or this emulation.

	  If you don't have a math coprocessor, you need to say Y here; if you
	  say Y here even though you have a coprocessor, the coprocessor will
	  be used nevertheless. (This behavior can be changed with the kernel
	  command line option "no387", which comes handy if your coprocessor
	  is broken. Try "man bootparam" or see the documentation of your boot
	  loader (lilo or loadlin) about how to pass options to the kernel at
	  boot time.) This means that it is a good idea to say Y here if you
	  intend to use this kernel on different machines.

	  More information about the internals of the Linux math coprocessor
	  emulation can be found in <file:arch/x86/math-emu/README>.

	  If you are not sure, say Y; apart from resulting in a 66 KB bigger
	  kernel, it won't hurt.

config MTRR
	bool "MTRR (Memory Type Range Register) support"
	---help---
	  On Intel P6 family processors (Pentium Pro, Pentium II and later)
	  the Memory Type Range Registers (MTRRs) may be used to control
	  processor access to memory ranges. This is most useful if you have
	  a video (VGA) card on a PCI or AGP bus. Enabling write-combining
	  allows bus write transfers to be combined into a larger transfer
	  before bursting over the PCI/AGP bus. This can increase performance
	  of image write operations 2.5 times or more. Saying Y here creates a
	  /proc/mtrr file which may be used to manipulate your processor's
	  MTRRs. Typically the X server should use this.

	  This code has a reasonably generic interface so that similar
	  control registers on other processors can be easily supported
	  as well:

	  The Cyrix 6x86, 6x86MX and M II processors have Address Range
	  Registers (ARRs) which provide a similar functionality to MTRRs. For
	  these, the ARRs are used to emulate the MTRRs.
	  The AMD K6-2 (stepping 8 and above) and K6-3 processors have two
	  MTRRs. The Centaur C6 (WinChip) has 8 MCRs, allowing
	  write-combining. All of these processors are supported by this code
	  and it makes sense to say Y here if you have one of them.

	  Saying Y here also fixes a problem with buggy SMP BIOSes which only
	  set the MTRRs for the boot CPU and not for the secondary CPUs. This
	  can lead to all sorts of problems, so it's good to say Y here.

	  You can safely say Y even if your machine doesn't have MTRRs, you'll
	  just add about 9 KB to your kernel.

	  See <file:Documentation/mtrr.txt> for more information.

config EFI
	bool "Boot from EFI support"
	depends on X86_32 && ACPI
	default n
	---help---
	This enables the kernel to boot on EFI platforms using
	system configuration information passed to it from the firmware.
	This also enables the kernel to use any EFI runtime services that are
	available (such as the EFI variable services).

	This option is only useful on systems that have EFI firmware
	and will result in a kernel image that is ~8k larger.  In addition,
	you must use the latest ELILO loader available at
	<http://elilo.sourceforge.net> in order to take advantage of
	kernel initialization using EFI information (neither GRUB nor LILO know
	anything about EFI).  However, even with this option, the resultant
	kernel should continue to boot on existing non-EFI platforms.

config IRQBALANCE
	bool "Enable kernel irq balancing"
	depends on X86_32 && SMP && X86_IO_APIC
	default y
	help
	  The default yes will allow the kernel to do irq load balancing.
	  Saying no will keep the kernel from doing irq load balancing.

# turning this on wastes a bunch of space.
# Summit needs it only when NUMA is on
config BOOT_IOREMAP
	bool
	depends on X86_32 && (((X86_SUMMIT || X86_GENERICARCH) && NUMA) || (X86 && EFI))
	default y

config SECCOMP
	bool "Enable seccomp to safely compute untrusted bytecode"
	depends on PROC_FS
	default y
	help
	  This kernel feature is useful for number crunching applications
	  that may need to compute untrusted bytecode during their
	  execution. By using pipes or other transports made available to
	  the process as file descriptors supporting the read/write
	  syscalls, it's possible to isolate those applications in
	  their own address space using seccomp. Once seccomp is
	  enabled via /proc/<pid>/seccomp, it cannot be disabled
	  and the task is only allowed to execute a few safe syscalls
	  defined by each seccomp mode.

	  If unsure, say Y. Only embedded should say N here.

config CC_STACKPROTECTOR
	bool "Enable -fstack-protector buffer overflow detection (EXPERIMENTAL)"
	depends on X86_64 && EXPERIMENTAL
	help
         This option turns on the -fstack-protector GCC feature. This
	  feature puts, at the beginning of critical functions, a canary
	  value on the stack just before the return address, and validates
	  the value just before actually returning.  Stack based buffer
	  overflows (that need to overwrite this return address) now also
	  overwrite the canary, which gets detected and the attack is then
	  neutralized via a kernel panic.

	  This feature requires gcc version 4.2 or above, or a distribution
	  gcc with the feature backported. Older versions are automatically
	  detected and for those versions, this configuration option is ignored.

config CC_STACKPROTECTOR_ALL
	bool "Use stack-protector for all functions"
	depends on CC_STACKPROTECTOR
	help
	  Normally, GCC only inserts the canary value protection for
	  functions that use large-ish on-stack buffers. By enabling
	  this option, GCC will be asked to do this for ALL functions.

source kernel/Kconfig.hz

config KEXEC
	bool "kexec system call"
	help
	  kexec is a system call that implements the ability to shutdown your
	  current kernel, and to start another kernel.  It is like a reboot
	  but it is independent of the system firmware.   And like a reboot
	  you can start any kernel with it, not just Linux.

	  The name comes from the similarity to the exec system call.

	  It is an ongoing process to be certain the hardware in a machine
	  is properly shutdown, so do not be surprised if this code does not
	  initially work for you.  It may help to enable device hotplugging
	  support.  As of this writing the exact hardware interface is
	  strongly in flux, so no good recommendation can be made.

config CRASH_DUMP
	bool "kernel crash dumps (EXPERIMENTAL)"
	depends on EXPERIMENTAL
	depends on X86_64 || (X86_32 && HIGHMEM)
	help
	  Generate crash dump after being started by kexec.
	  This should be normally only set in special crash dump kernels
	  which are loaded in the main kernel with kexec-tools into
	  a specially reserved region and then later executed after
	  a crash by kdump/kexec. The crash dump kernel must be compiled
	  to a memory address not used by the main kernel or BIOS using
	  PHYSICAL_START, or it must be built as a relocatable image
	  (CONFIG_RELOCATABLE=y).
	  For more details see Documentation/kdump/kdump.txt

config PHYSICAL_START
	hex "Physical address where the kernel is loaded" if (EMBEDDED || CRASH_DUMP)
	default "0x1000000" if X86_NUMAQ
	default "0x200000" if X86_64
	default "0x100000"
	help
	  This gives the physical address where the kernel is loaded.

	  If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
	  bzImage will decompress itself to above physical address and
	  run from there. Otherwise, bzImage will run from the address where
	  it has been loaded by the boot loader and will ignore above physical
	  address.

	  In normal kdump cases one does not have to set/change this option
	  as now bzImage can be compiled as a completely relocatable image
	  (CONFIG_RELOCATABLE=y) and be used to load and run from a different
	  address. This option is mainly useful for the folks who don't want
	  to use a bzImage for capturing the crash dump and want to use a
	  vmlinux instead. vmlinux is not relocatable hence a kernel needs
	  to be specifically compiled to run from a specific memory area
	  (normally a reserved region) and this option comes handy.

	  So if you are using bzImage for capturing the crash dump, leave
	  the value here unchanged to 0x100000 and set CONFIG_RELOCATABLE=y.
	  Otherwise if you plan to use vmlinux for capturing the crash dump
	  change this value to start of the reserved region (Typically 16MB
	  0x1000000). In other words, it can be set based on the "X" value as
	  specified in the "crashkernel=YM@XM" command line boot parameter
	  passed to the panic-ed kernel. Typically this parameter is set as
	  crashkernel=64M@16M. Please take a look at
	  Documentation/kdump/kdump.txt for more details about crash dumps.

	  Usage of bzImage for capturing the crash dump is recommended as
	  one does not have to build two kernels. Same kernel can be used
	  as production kernel and capture kernel. Above option should have
	  gone away after relocatable bzImage support is introduced. But it
	  is present because there are users out there who continue to use
	  vmlinux for dump capture. This option should go away down the
	  line.

	  Don't change this unless you know what you are doing.

config RELOCATABLE
	bool "Build a relocatable kernel (EXPERIMENTAL)"
	depends on EXPERIMENTAL
	help
	  This builds a kernel image that retains relocation information
	  so it can be loaded someplace besides the default 1MB.
	  The relocations tend to make the kernel binary about 10% larger,
	  but are discarded at runtime.

	  One use is for the kexec on panic case where the recovery kernel
	  must live at a different physical address than the primary
	  kernel.

	  Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
	  it has been loaded at and the compile time physical address
	  (CONFIG_PHYSICAL_START) is ignored.

config PHYSICAL_ALIGN
	hex
	prompt "Alignment value to which kernel should be aligned" if X86_32
	default "0x100000" if X86_32
	default "0x200000" if X86_64
	range 0x2000 0x400000
	help
	  This value puts the alignment restrictions on physical address
	  where kernel is loaded and run from. Kernel is compiled for an
	  address which meets above alignment restriction.

	  If bootloader loads the kernel at a non-aligned address and
	  CONFIG_RELOCATABLE is set, kernel will move itself to nearest
	  address aligned to above value and run from there.

	  If bootloader loads the kernel at a non-aligned address and
	  CONFIG_RELOCATABLE is not set, kernel will ignore the run time
	  load address and decompress itself to the address it has been
	  compiled for and run from there. The address for which kernel is
	  compiled already meets above alignment restrictions. Hence the
	  end result is that kernel runs from a physical address meeting
	  above alignment restrictions.

	  Don't change this unless you know what you are doing.

config HOTPLUG_CPU
	bool "Support for suspend on SMP and hot-pluggable CPUs (EXPERIMENTAL)"
	depends on SMP && HOTPLUG && EXPERIMENTAL && !X86_VOYAGER
	---help---
	  Say Y here to experiment with turning CPUs off and on, and to
	  enable suspend on SMP systems. CPUs can be controlled through
	  /sys/devices/system/cpu.
	  Say N if you want to disable CPU hotplug and don't need to
	  suspend.

config COMPAT_VDSO
	bool "Compat VDSO support"
	default y
	depends on X86_32
	help
	  Map the VDSO to the predictable old-style address too.
	---help---
	  Say N here if you are running a sufficiently recent glibc
	  version (2.3.3 or later), to remove the high-mapped
	  VDSO mapping and to exclusively use the randomized VDSO.

	  If unsure, say Y.

endmenu

config ARCH_ENABLE_MEMORY_HOTPLUG
	def_bool y
	depends on X86_64 || (X86_32 && HIGHMEM)

config MEMORY_HOTPLUG_RESERVE
	def_bool X86_64
	depends on (MEMORY_HOTPLUG && DISCONTIGMEM)

config HAVE_ARCH_EARLY_PFN_TO_NID
	def_bool X86_64
	depends on NUMA

config OUT_OF_LINE_PFN_TO_PAGE