rcu: Parallelize and economize NOCB kthread wakeups

[linux.git] / init / Kconfig

config ARCH
	string
	option env="ARCH"

config KERNELVERSION
	string
	option env="KERNELVERSION"

config DEFCONFIG_LIST
	string
	depends on !UML
	option defconfig_list
	default "/lib/modules/$UNAME_RELEASE/.config"
	default "/etc/kernel-config"
	default "/boot/config-$UNAME_RELEASE"
	default "$ARCH_DEFCONFIG"
	default "arch/$ARCH/defconfig"

config CONSTRUCTORS
	bool
	depends on !UML

config IRQ_WORK
	bool

config BUILDTIME_EXTABLE_SORT
	bool

menu "General setup"

config BROKEN
	bool

config BROKEN_ON_SMP
	bool
	depends on BROKEN || !SMP
	default y

config INIT_ENV_ARG_LIMIT
	int
	default 32 if !UML
	default 128 if UML
	help
	  Maximum of each of the number of arguments and environment
	  variables passed to init from the kernel command line.


config CROSS_COMPILE
	string "Cross-compiler tool prefix"
	help
	  Same as running 'make CROSS_COMPILE=prefix-' but stored for
	  default make runs in this kernel build directory.  You don't
	  need to set this unless you want the configured kernel build
	  directory to select the cross-compiler automatically.

config COMPILE_TEST
	bool "Compile also drivers which will not load"
	default n
	help
	  Some drivers can be compiled on a different platform than they are
	  intended to be run on. Despite they cannot be loaded there (or even
	  when they load they cannot be used due to missing HW support),
	  developers still, opposing to distributors, might want to build such
	  drivers to compile-test them.

	  If you are a developer and want to build everything available, say Y
	  here. If you are a user/distributor, say N here to exclude useless
	  drivers to be distributed.

config LOCALVERSION
	string "Local version - append to kernel release"
	help
	  Append an extra string to the end of your kernel version.
	  This will show up when you type uname, for example.
	  The string you set here will be appended after the contents of
	  any files with a filename matching localversion* in your
	  object and source tree, in that order.  Your total string can
	  be a maximum of 64 characters.

config LOCALVERSION_AUTO
	bool "Automatically append version information to the version string"
	default y
	help
	  This will try to automatically determine if the current tree is a
	  release tree by looking for git tags that belong to the current
	  top of tree revision.

	  A string of the format -gxxxxxxxx will be added to the localversion
	  if a git-based tree is found.  The string generated by this will be
	  appended after any matching localversion* files, and after the value
	  set in CONFIG_LOCALVERSION.

	  (The actual string used here is the first eight characters produced
	  by running the command:

	    $ git rev-parse --verify HEAD

	  which is done within the script "scripts/setlocalversion".)

config HAVE_KERNEL_GZIP
	bool

config HAVE_KERNEL_BZIP2
	bool

config HAVE_KERNEL_LZMA
	bool

config HAVE_KERNEL_XZ
	bool

config HAVE_KERNEL_LZO
	bool

config HAVE_KERNEL_LZ4
	bool

choice
	prompt "Kernel compression mode"
	default KERNEL_GZIP
	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
	help
	  The linux kernel is a kind of self-extracting executable.
	  Several compression algorithms are available, which differ
	  in efficiency, compression and decompression speed.
	  Compression speed is only relevant when building a kernel.
	  Decompression speed is relevant at each boot.

	  If you have any problems with bzip2 or lzma compressed
	  kernels, mail me (Alain Knaff) <[email protected]>. (An older
	  version of this functionality (bzip2 only), for 2.4, was
	  supplied by Christian Ludwig)

	  High compression options are mostly useful for users, who
	  are low on disk space (embedded systems), but for whom ram
	  size matters less.

	  If in doubt, select 'gzip'

config KERNEL_GZIP
	bool "Gzip"
	depends on HAVE_KERNEL_GZIP
	help
	  The old and tried gzip compression. It provides a good balance
	  between compression ratio and decompression speed.

config KERNEL_BZIP2
	bool "Bzip2"
	depends on HAVE_KERNEL_BZIP2
	help
	  Its compression ratio and speed is intermediate.
	  Decompression speed is slowest among the choices.  The kernel
	  size is about 10% smaller with bzip2, in comparison to gzip.
	  Bzip2 uses a large amount of memory. For modern kernels you
	  will need at least 8MB RAM or more for booting.

config KERNEL_LZMA
	bool "LZMA"
	depends on HAVE_KERNEL_LZMA
	help
	  This compression algorithm's ratio is best.  Decompression speed
	  is between gzip and bzip2.  Compression is slowest.
	  The kernel size is about 33% smaller with LZMA in comparison to gzip.

config KERNEL_XZ
	bool "XZ"
	depends on HAVE_KERNEL_XZ
	help
	  XZ uses the LZMA2 algorithm and instruction set specific
	  BCJ filters which can improve compression ratio of executable
	  code. The size of the kernel is about 30% smaller with XZ in
	  comparison to gzip. On architectures for which there is a BCJ
	  filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
	  will create a few percent smaller kernel than plain LZMA.

	  The speed is about the same as with LZMA: The decompression
	  speed of XZ is better than that of bzip2 but worse than gzip
	  and LZO. Compression is slow.

config KERNEL_LZO
	bool "LZO"
	depends on HAVE_KERNEL_LZO
	help
	  Its compression ratio is the poorest among the choices. The kernel
	  size is about 10% bigger than gzip; however its speed
	  (both compression and decompression) is the fastest.

config KERNEL_LZ4
	bool "LZ4"
	depends on HAVE_KERNEL_LZ4
	help
	  LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
	  A preliminary version of LZ4 de/compression tool is available at
	  <https://code.google.com/p/lz4/>.

	  Its compression ratio is worse than LZO. The size of the kernel
	  is about 8% bigger than LZO. But the decompression speed is
	  faster than LZO.

endchoice

config DEFAULT_HOSTNAME
	string "Default hostname"
	default "(none)"
	help
	  This option determines the default system hostname before userspace
	  calls sethostname(2). The kernel traditionally uses "(none)" here,
	  but you may wish to use a different default here to make a minimal
	  system more usable with less configuration.

config SWAP
	bool "Support for paging of anonymous memory (swap)"
	depends on MMU && BLOCK
	default y
	help
	  This option allows you to choose whether you want to have support
	  for so called swap devices or swap files in your kernel that are
	  used to provide more virtual memory than the actual RAM present
	  in your computer.  If unsure say Y.

config SYSVIPC
	bool "System V IPC"
	---help---
	  Inter Process Communication is a suite of library functions and
	  system calls which let processes (running programs) synchronize and
	  exchange information. It is generally considered to be a good thing,
	  and some programs won't run unless you say Y here. In particular, if
	  you want to run the DOS emulator dosemu under Linux (read the
	  DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
	  you'll need to say Y here.

	  You can find documentation about IPC with "info ipc" and also in
	  section 6.4 of the Linux Programmer's Guide, available from
	  <http://www.tldp.org/guides.html>.

config SYSVIPC_SYSCTL
	bool
	depends on SYSVIPC
	depends on SYSCTL
	default y

config POSIX_MQUEUE
	bool "POSIX Message Queues"
	depends on NET
	---help---
	  POSIX variant of message queues is a part of IPC. In POSIX message
	  queues every message has a priority which decides about succession
	  of receiving it by a process. If you want to compile and run
	  programs written e.g. for Solaris with use of its POSIX message
	  queues (functions mq_*) say Y here.

	  POSIX message queues are visible as a filesystem called 'mqueue'
	  and can be mounted somewhere if you want to do filesystem
	  operations on message queues.

	  If unsure, say Y.

config POSIX_MQUEUE_SYSCTL
	bool
	depends on POSIX_MQUEUE
	depends on SYSCTL
	default y

config CROSS_MEMORY_ATTACH
	bool "Enable process_vm_readv/writev syscalls"
	depends on MMU
	default y
	help
	  Enabling this option adds the system calls process_vm_readv and
	  process_vm_writev which allow a process with the correct privileges
	  to directly read from or write to to another process's address space.
	  See the man page for more details.

config FHANDLE
	bool "open by fhandle syscalls"
	select EXPORTFS
	help
	  If you say Y here, a user level program will be able to map
	  file names to handle and then later use the handle for
	  different file system operations. This is useful in implementing
	  userspace file servers, which now track files using handles instead
	  of names. The handle would remain the same even if file names
	  get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
	  syscalls.

config USELIB
	bool "uselib syscall"
	default y
	help
	  This option enables the uselib syscall, a system call used in the
	  dynamic linker from libc5 and earlier.  glibc does not use this
	  system call.  If you intend to run programs built on libc5 or
	  earlier, you may need to enable this syscall.  Current systems
	  running glibc can safely disable this.

config AUDIT
	bool "Auditing support"
	depends on NET
	help
	  Enable auditing infrastructure that can be used with another
	  kernel subsystem, such as SELinux (which requires this for
	  logging of avc messages output).  Does not do system-call
	  auditing without CONFIG_AUDITSYSCALL.

config HAVE_ARCH_AUDITSYSCALL
	bool

config AUDITSYSCALL
	bool "Enable system-call auditing support"
	depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
	default y if SECURITY_SELINUX
	help
	  Enable low-overhead system-call auditing infrastructure that
	  can be used independently or with another kernel subsystem,
	  such as SELinux.

config AUDIT_WATCH
	def_bool y
	depends on AUDITSYSCALL
	select FSNOTIFY

config AUDIT_TREE
	def_bool y
	depends on AUDITSYSCALL
	select FSNOTIFY

source "kernel/irq/Kconfig"
source "kernel/time/Kconfig"

menu "CPU/Task time and stats accounting"

config VIRT_CPU_ACCOUNTING
	bool

choice
	prompt "Cputime accounting"
	default TICK_CPU_ACCOUNTING if !PPC64
	default VIRT_CPU_ACCOUNTING_NATIVE if PPC64

# Kind of a stub config for the pure tick based cputime accounting
config TICK_CPU_ACCOUNTING
	bool "Simple tick based cputime accounting"
	depends on !S390 && !NO_HZ_FULL
	help
	  This is the basic tick based cputime accounting that maintains
	  statistics about user, system and idle time spent on per jiffies
	  granularity.

	  If unsure, say Y.

config VIRT_CPU_ACCOUNTING_NATIVE
	bool "Deterministic task and CPU time accounting"
	depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
	select VIRT_CPU_ACCOUNTING
	help
	  Select this option to enable more accurate task and CPU time
	  accounting.  This is done by reading a CPU counter on each
	  kernel entry and exit and on transitions within the kernel
	  between system, softirq and hardirq state, so there is a
	  small performance impact.  In the case of s390 or IBM POWER > 5,
	  this also enables accounting of stolen time on logically-partitioned
	  systems.

config VIRT_CPU_ACCOUNTING_GEN
	bool "Full dynticks CPU time accounting"
	depends on HAVE_CONTEXT_TRACKING
	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
	select VIRT_CPU_ACCOUNTING
	select CONTEXT_TRACKING
	help
	  Select this option to enable task and CPU time accounting on full
	  dynticks systems. This accounting is implemented by watching every
	  kernel-user boundaries using the context tracking subsystem.
	  The accounting is thus performed at the expense of some significant
	  overhead.

	  For now this is only useful if you are working on the full
	  dynticks subsystem development.

	  If unsure, say N.

config IRQ_TIME_ACCOUNTING
	bool "Fine granularity task level IRQ time accounting"
	depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
	help
	  Select this option to enable fine granularity task irq time
	  accounting. This is done by reading a timestamp on each
	  transitions between softirq and hardirq state, so there can be a
	  small performance impact.

	  If in doubt, say N here.

endchoice

config BSD_PROCESS_ACCT
	bool "BSD Process Accounting"
	help
	  If you say Y here, a user level program will be able to instruct the
	  kernel (via a special system call) to write process accounting
	  information to a file: whenever a process exits, information about
	  that process will be appended to the file by the kernel.  The
	  information includes things such as creation time, owning user,
	  command name, memory usage, controlling terminal etc. (the complete
	  list is in the struct acct in <file:include/linux/acct.h>).  It is
	  up to the user level program to do useful things with this
	  information.  This is generally a good idea, so say Y.

config BSD_PROCESS_ACCT_V3
	bool "BSD Process Accounting version 3 file format"
	depends on BSD_PROCESS_ACCT
	default n
	help
	  If you say Y here, the process accounting information is written
	  in a new file format that also logs the process IDs of each
	  process and it's parent. Note that this file format is incompatible
	  with previous v0/v1/v2 file formats, so you will need updated tools
	  for processing it. A preliminary version of these tools is available
	  at <http://www.gnu.org/software/acct/>.

config TASKSTATS
	bool "Export task/process statistics through netlink"
	depends on NET
	default n
	help
	  Export selected statistics for tasks/processes through the
	  generic netlink interface. Unlike BSD process accounting, the
	  statistics are available during the lifetime of tasks/processes as
	  responses to commands. Like BSD accounting, they are sent to user
	  space on task exit.

	  Say N if unsure.

config TASK_DELAY_ACCT
	bool "Enable per-task delay accounting"
	depends on TASKSTATS
	help
	  Collect information on time spent by a task waiting for system
	  resources like cpu, synchronous block I/O completion and swapping
	  in pages. Such statistics can help in setting a task's priorities
	  relative to other tasks for cpu, io, rss limits etc.

	  Say N if unsure.

config TASK_XACCT
	bool "Enable extended accounting over taskstats"
	depends on TASKSTATS
	help
	  Collect extended task accounting data and send the data
	  to userland for processing over the taskstats interface.

	  Say N if unsure.

config TASK_IO_ACCOUNTING
	bool "Enable per-task storage I/O accounting"
	depends on TASK_XACCT
	help
	  Collect information on the number of bytes of storage I/O which this
	  task has caused.

	  Say N if unsure.

endmenu # "CPU/Task time and stats accounting"

menu "RCU Subsystem"

choice
	prompt "RCU Implementation"
	default TREE_RCU

config TREE_RCU
	bool "Tree-based hierarchical RCU"
	depends on !PREEMPT && SMP
	select IRQ_WORK
	help
	  This option selects the RCU implementation that is
	  designed for very large SMP system with hundreds or
	  thousands of CPUs.  It also scales down nicely to
	  smaller systems.

config TREE_PREEMPT_RCU
	bool "Preemptible tree-based hierarchical RCU"
	depends on PREEMPT
	select IRQ_WORK
	help
	  This option selects the RCU implementation that is
	  designed for very large SMP systems with hundreds or
	  thousands of CPUs, but for which real-time response
	  is also required.  It also scales down nicely to
	  smaller systems.

	  Select this option if you are unsure.

config TINY_RCU
	bool "UP-only small-memory-footprint RCU"
	depends on !PREEMPT && !SMP
	help
	  This option selects the RCU implementation that is
	  designed for UP systems from which real-time response
	  is not required.  This option greatly reduces the
	  memory footprint of RCU.

endchoice

config PREEMPT_RCU
	def_bool TREE_PREEMPT_RCU
	help
	  This option enables preemptible-RCU code that is common between
	  the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.

config RCU_STALL_COMMON
	def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
	help
	  This option enables RCU CPU stall code that is common between
	  the TINY and TREE variants of RCU.  The purpose is to allow
	  the tiny variants to disable RCU CPU stall warnings, while
	  making these warnings mandatory for the tree variants.

config CONTEXT_TRACKING
       bool

config RCU_USER_QS
	bool "Consider userspace as in RCU extended quiescent state"
	depends on HAVE_CONTEXT_TRACKING && SMP
	select CONTEXT_TRACKING
	help
	  This option sets hooks on kernel / userspace boundaries and
	  puts RCU in extended quiescent state when the CPU runs in
	  userspace. It means that when a CPU runs in userspace, it is
	  excluded from the global RCU state machine and thus doesn't
	  try to keep the timer tick on for RCU.

	  Unless you want to hack and help the development of the full
	  dynticks mode, you shouldn't enable this option.  It also
	  adds unnecessary overhead.

	  If unsure say N

config CONTEXT_TRACKING_FORCE
	bool "Force context tracking"
	depends on CONTEXT_TRACKING
	default y if !NO_HZ_FULL
	help
	  The major pre-requirement for full dynticks to work is to
	  support the context tracking subsystem. But there are also
	  other dependencies to provide in order to make the full
	  dynticks working.

	  This option stands for testing when an arch implements the
	  context tracking backend but doesn't yet fullfill all the
	  requirements to make the full dynticks feature working.
	  Without the full dynticks, there is no way to test the support
	  for context tracking and the subsystems that rely on it: RCU
	  userspace extended quiescent state and tickless cputime
	  accounting. This option copes with the absence of the full
	  dynticks subsystem by forcing the context tracking on all
	  CPUs in the system.

	  Say Y only if you're working on the development of an
	  architecture backend for the context tracking.

	  Say N otherwise, this option brings an overhead that you
	  don't want in production.


config RCU_FANOUT
	int "Tree-based hierarchical RCU fanout value"
	range 2 64 if 64BIT
	range 2 32 if !64BIT
	depends on TREE_RCU || TREE_PREEMPT_RCU
	default 64 if 64BIT
	default 32 if !64BIT
	help
	  This option controls the fanout of hierarchical implementations
	  of RCU, allowing RCU to work efficiently on machines with
	  large numbers of CPUs.  This value must be at least the fourth
	  root of NR_CPUS, which allows NR_CPUS to be insanely large.
	  The default value of RCU_FANOUT should be used for production
	  systems, but if you are stress-testing the RCU implementation
	  itself, small RCU_FANOUT values allow you to test large-system
	  code paths on small(er) systems.

	  Select a specific number if testing RCU itself.
	  Take the default if unsure.

config RCU_FANOUT_LEAF
	int "Tree-based hierarchical RCU leaf-level fanout value"
	range 2 RCU_FANOUT if 64BIT
	range 2 RCU_FANOUT if !64BIT
	depends on TREE_RCU || TREE_PREEMPT_RCU
	default 16
	help
	  This option controls the leaf-level fanout of hierarchical
	  implementations of RCU, and allows trading off cache misses
	  against lock contention.  Systems that synchronize their
	  scheduling-clock interrupts for energy-efficiency reasons will
	  want the default because the smaller leaf-level fanout keeps
	  lock contention levels acceptably low.  Very large systems
	  (hundreds or thousands of CPUs) will instead want to set this
	  value to the maximum value possible in order to reduce the
	  number of cache misses incurred during RCU's grace-period
	  initialization.  These systems tend to run CPU-bound, and thus
	  are not helped by synchronized interrupts, and thus tend to
	  skew them, which reduces lock contention enough that large
	  leaf-level fanouts work well.

	  Select a specific number if testing RCU itself.

	  Select the maximum permissible value for large systems.

	  Take the default if unsure.

config RCU_FANOUT_EXACT
	bool "Disable tree-based hierarchical RCU auto-balancing"
	depends on TREE_RCU || TREE_PREEMPT_RCU
	default n
	help
	  This option forces use of the exact RCU_FANOUT value specified,
	  regardless of imbalances in the hierarchy.  This is useful for
	  testing RCU itself, and might one day be useful on systems with
	  strong NUMA behavior.

	  Without RCU_FANOUT_EXACT, the code will balance the hierarchy.

	  Say N if unsure.

config RCU_FAST_NO_HZ
	bool "Accelerate last non-dyntick-idle CPU's grace periods"
	depends on NO_HZ_COMMON && SMP
	default n
	help
	  This option permits CPUs to enter dynticks-idle state even if
	  they have RCU callbacks queued, and prevents RCU from waking
	  these CPUs up more than roughly once every four jiffies (by
	  default, you can adjust this using the rcutree.rcu_idle_gp_delay
	  parameter), thus improving energy efficiency.  On the other
	  hand, this option increases the duration of RCU grace periods,
	  for example, slowing down synchronize_rcu().

	  Say Y if energy efficiency is critically important, and you
	  	don't care about increased grace-period durations.

	  Say N if you are unsure.

config TREE_RCU_TRACE
	def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
	select DEBUG_FS
	help
	  This option provides tracing for the TREE_RCU and
	  TREE_PREEMPT_RCU implementations, permitting Makefile to
	  trivially select kernel/rcutree_trace.c.

config RCU_BOOST
	bool "Enable RCU priority boosting"
	depends on RT_MUTEXES && PREEMPT_RCU
	default n
	help
	  This option boosts the priority of preempted RCU readers that
	  block the current preemptible RCU grace period for too long.
	  This option also prevents heavy loads from blocking RCU
	  callback invocation for all flavors of RCU.

	  Say Y here if you are working with real-time apps or heavy loads
	  Say N here if you are unsure.

config RCU_BOOST_PRIO
	int "Real-time priority to boost RCU readers to"
	range 1 99
	depends on RCU_BOOST
	default 1
	help
	  This option specifies the real-time priority to which long-term
	  preempted RCU readers are to be boosted.  If you are working
	  with a real-time application that has one or more CPU-bound
	  threads running at a real-time priority level, you should set
	  RCU_BOOST_PRIO to a priority higher then the highest-priority
	  real-time CPU-bound thread.  The default RCU_BOOST_PRIO value
	  of 1 is appropriate in the common case, which is real-time
	  applications that do not have any CPU-bound threads.

	  Some real-time applications might not have a single real-time
	  thread that saturates a given CPU, but instead might have
	  multiple real-time threads that, taken together, fully utilize
	  that CPU.  In this case, you should set RCU_BOOST_PRIO to
	  a priority higher than the lowest-priority thread that is
	  conspiring to prevent the CPU from running any non-real-time
	  tasks.  For example, if one thread at priority 10 and another
	  thread at priority 5 are between themselves fully consuming
	  the CPU time on a given CPU, then RCU_BOOST_PRIO should be
	  set to priority 6 or higher.

	  Specify the real-time priority, or take the default if unsure.

config RCU_BOOST_DELAY
	int "Milliseconds to delay boosting after RCU grace-period start"
	range 0 3000
	depends on RCU_BOOST
	default 500
	help
	  This option specifies the time to wait after the beginning of
	  a given grace period before priority-boosting preempted RCU
	  readers blocking that grace period.  Note that any RCU reader
	  blocking an expedited RCU grace period is boosted immediately.

	  Accept the default if unsure.

config RCU_NOCB_CPU
	bool "Offload RCU callback processing from boot-selected CPUs"
	depends on TREE_RCU || TREE_PREEMPT_RCU
	default n
	help
	  Use this option to reduce OS jitter for aggressive HPC or
	  real-time workloads.	It can also be used to offload RCU
	  callback invocation to energy-efficient CPUs in battery-powered
	  asymmetric multiprocessors.

	  This option offloads callback invocation from the set of
	  CPUs specified at boot time by the rcu_nocbs parameter.
	  For each such CPU, a kthread ("rcuox/N") will be created to
	  invoke callbacks, where the "N" is the CPU being offloaded,
	  and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
	  "s" for RCU-sched.  Nothing prevents this kthread from running
	  on the specified CPUs, but (1) the kthreads may be preempted
	  between each callback, and (2) affinity or cgroups can be used
	  to force the kthreads to run on whatever set of CPUs is desired.

	  Say Y here if you want to help to debug reduced OS jitter.
	  Say N here if you are unsure.

choice
	prompt "Build-forced no-CBs CPUs"
	default RCU_NOCB_CPU_NONE
	help
	  This option allows no-CBs CPUs (whose RCU callbacks are invoked
	  from kthreads rather than from softirq context) to be specified
	  at build time.  Additional no-CBs CPUs may be specified by
	  the rcu_nocbs= boot parameter.

config RCU_NOCB_CPU_NONE
	bool "No build_forced no-CBs CPUs"
	depends on RCU_NOCB_CPU && !NO_HZ_FULL
	help
	  This option does not force any of the CPUs to be no-CBs CPUs.
	  Only CPUs designated by the rcu_nocbs= boot parameter will be
	  no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
	  kthreads whose names begin with "rcuo".  All other CPUs will
	  invoke their own RCU callbacks in softirq context.

	  Select this option if you want to choose no-CBs CPUs at
	  boot time, for example, to allow testing of different no-CBs
	  configurations without having to rebuild the kernel each time.

config RCU_NOCB_CPU_ZERO
	bool "CPU 0 is a build_forced no-CBs CPU"
	depends on RCU_NOCB_CPU && !NO_HZ_FULL
	help
	  This option forces CPU 0 to be a no-CBs CPU, so that its RCU
	  callbacks are invoked by a per-CPU kthread whose name begins
	  with "rcuo".	Additional CPUs may be designated as no-CBs
	  CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
	  All other CPUs will invoke their own RCU callbacks in softirq
	  context.

	  Select this if CPU 0 needs to be a no-CBs CPU for real-time
	  or energy-efficiency reasons, but the real reason it exists
	  is to ensure that randconfig testing covers mixed systems.

config RCU_NOCB_CPU_ALL
	bool "All CPUs are build_forced no-CBs CPUs"
	depends on RCU_NOCB_CPU
	help
	  This option forces all CPUs to be no-CBs CPUs.  The rcu_nocbs=
	  boot parameter will be ignored.  All CPUs' RCU callbacks will
	  be executed in the context of per-CPU rcuo kthreads created for
	  this purpose.  Assuming that the kthreads whose names start with
	  "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
	  on the remaining CPUs, but might decrease memory locality during
	  RCU-callback invocation, thus potentially degrading throughput.

	  Select this if all CPUs need to be no-CBs CPUs for real-time
	  or energy-efficiency reasons.

endchoice

endmenu # "RCU Subsystem"

config IKCONFIG
	tristate "Kernel .config support"
	---help---
	  This option enables the complete Linux kernel ".config" file
	  contents to be saved in the kernel. It provides documentation
	  of which kernel options are used in a running kernel or in an
	  on-disk kernel.  This information can be extracted from the kernel
	  image file with the script scripts/extract-ikconfig and used as
	  input to rebuild the current kernel or to build another kernel.
	  It can also be extracted from a running kernel by reading
	  /proc/config.gz if enabled (below).

config IKCONFIG_PROC
	bool "Enable access to .config through /proc/config.gz"
	depends on IKCONFIG && PROC_FS
	---help---
	  This option enables access to the kernel configuration file
	  through /proc/config.gz.

config LOG_BUF_SHIFT
	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
	range 12 21
	default 17
	help
	  Select kernel log buffer size as a power of 2.
	  Examples:
	  	     17 => 128 KB
		     16 => 64 KB
	             15 => 32 KB
	             14 => 16 KB
		     13 =>  8 KB
		     12 =>  4 KB

#
# Architectures with an unreliable sched_clock() should select this:
#
config HAVE_UNSTABLE_SCHED_CLOCK
	bool

config GENERIC_SCHED_CLOCK
	bool

#
# For architectures that want to enable the support for NUMA-affine scheduler
# balancing logic:
#
config ARCH_SUPPORTS_NUMA_BALANCING
	bool

#
# For architectures that know their GCC __int128 support is sound
#
config ARCH_SUPPORTS_INT128
	bool

# For architectures that (ab)use NUMA to represent different memory regions
# all cpu-local but of different latencies, such as SuperH.
#
config ARCH_WANT_NUMA_VARIABLE_LOCALITY
	bool

#
# For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
config ARCH_WANTS_PROT_NUMA_PROT_NONE
	bool

config ARCH_USES_NUMA_PROT_NONE
	bool
	default y
	depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
	depends on NUMA_BALANCING

config NUMA_BALANCING_DEFAULT_ENABLED
	bool "Automatically enable NUMA aware memory/task placement"
	default y
	depends on NUMA_BALANCING
	help
	  If set, automatic NUMA balancing will be enabled if running on a NUMA
	  machine.

config NUMA_BALANCING
	bool "Memory placement aware NUMA scheduler"
	depends on ARCH_SUPPORTS_NUMA_BALANCING
	depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
	depends on SMP && NUMA && MIGRATION
	help
	  This option adds support for automatic NUMA aware memory/task placement.
	  The mechanism is quite primitive and is based on migrating memory when
	  it has references to the node the task is running on.

	  This system will be inactive on UMA systems.

menuconfig CGROUPS
	boolean "Control Group support"
	select KERNFS
	help
	  This option adds support for grouping sets of processes together, for
	  use with process control subsystems such as Cpusets, CFS, memory
	  controls or device isolation.
	  See
		- Documentation/scheduler/sched-design-CFS.txt	(CFS)
		- Documentation/cgroups/ (features for grouping, isolation
					  and resource control)

	  Say N if unsure.

if CGROUPS

config CGROUP_DEBUG
	bool "Example debug cgroup subsystem"
	default n
	help
	  This option enables a simple cgroup subsystem that
	  exports useful debugging information about the cgroups
	  framework.

	  Say N if unsure.

config CGROUP_FREEZER
	bool "Freezer cgroup subsystem"
	help
	  Provides a way to freeze and unfreeze all tasks in a
	  cgroup.

config CGROUP_DEVICE
	bool "Device controller for cgroups"
	help
	  Provides a cgroup implementing whitelists for devices which
	  a process in the cgroup can mknod or open.

config CPUSETS
	bool "Cpuset support"
	help
	  This option will let you create and manage CPUSETs which
	  allow dynamically partitioning a system into sets of CPUs and
	  Memory Nodes and assigning tasks to run only within those sets.
	  This is primarily useful on large SMP or NUMA systems.

	  Say N if unsure.

config PROC_PID_CPUSET
	bool "Include legacy /proc/<pid>/cpuset file"
	depends on CPUSETS
	default y

config CGROUP_CPUACCT
	bool "Simple CPU accounting cgroup subsystem"
	help
	  Provides a simple Resource Controller for monitoring the
	  total CPU consumed by the tasks in a cgroup.

config RESOURCE_COUNTERS
	bool "Resource counters"
	help
	  This option enables controller independent resource accounting
	  infrastructure that works with cgroups.

config MEMCG
	bool "Memory Resource Controller for Control Groups"
	depends on RESOURCE_COUNTERS
	select EVENTFD
	help
	  Provides a memory resource controller that manages both anonymous
	  memory and page cache. (See Documentation/cgroups/memory.txt)

	  Note that setting this option increases fixed memory overhead
	  associated with each page of memory in the system. By this,
	  8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
	  usage tracking struct at boot. Total amount of this is printed out
	  at boot.

	  Only enable when you're ok with these trade offs and really
	  sure you need the memory resource controller. Even when you enable
	  this, you can set "cgroup_disable=memory" at your boot option to
	  disable memory resource controller and you can avoid overheads.
	  (and lose benefits of memory resource controller)

config MEMCG_SWAP
	bool "Memory Resource Controller Swap Extension"
	depends on MEMCG && SWAP
	help
	  Add swap management feature to memory resource controller. When you
	  enable this, you can limit mem+swap usage per cgroup. In other words,
	  when you disable this, memory resource controller has no cares to
	  usage of swap...a process can exhaust all of the swap. This extension
	  is useful when you want to avoid exhaustion swap but this itself
	  adds more overheads and consumes memory for remembering information.
	  Especially if you use 32bit system or small memory system, please
	  be careful about enabling this. When memory resource controller
	  is disabled by boot option, this will be automatically disabled and
	  there will be no overhead from this. Even when you set this config=y,
	  if boot option "swapaccount=0" is set, swap will not be accounted.
	  Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
	  size is 4096bytes, 512k per 1Gbytes of swap.
config MEMCG_SWAP_ENABLED
	bool "Memory Resource Controller Swap Extension enabled by default"
	depends on MEMCG_SWAP
	default y
	help
	  Memory Resource Controller Swap Extension comes with its price in
	  a bigger memory consumption. General purpose distribution kernels
	  which want to enable the feature but keep it disabled by default
	  and let the user enable it by swapaccount=1 boot command line
	  parameter should have this option unselected.
	  For those who want to have the feature enabled by default should
	  select this option (if, for some reason, they need to disable it
	  then swapaccount=0 does the trick).
config MEMCG_KMEM
	bool "Memory Resource Controller Kernel Memory accounting"
	depends on MEMCG
	depends on SLUB || SLAB
	help
	  The Kernel Memory extension for Memory Resource Controller can limit
	  the amount of memory used by kernel objects in the system. Those are
	  fundamentally different from the entities handled by the standard
	  Memory Controller, which are page-based, and can be swapped. Users of
	  the kmem extension can use it to guarantee that no group of processes
	  will ever exhaust kernel resources alone.

	  WARNING: Current implementation lacks reclaim support. That means
	  allocation attempts will fail when close to the limit even if there
	  are plenty of kmem available for reclaim. That makes this option
	  unusable in real life so DO NOT SELECT IT unless for development
	  purposes.

config CGROUP_HUGETLB
	bool "HugeTLB Resource Controller for Control Groups"
	depends on RESOURCE_COUNTERS && HUGETLB_PAGE
	default n
	help
	  Provides a cgroup Resource Controller for HugeTLB pages.
	  When you enable this, you can put a per cgroup limit on HugeTLB usage.
	  The limit is enforced during page fault. Since HugeTLB doesn't
	  support page reclaim, enforcing the limit at page fault time implies
	  that, the application will get SIGBUS signal if it tries to access
	  HugeTLB pages beyond its limit. This requires the application to know
	  beforehand how much HugeTLB pages it would require for its use. The
	  control group is tracked in the third page lru pointer. This means
	  that we cannot use the controller with huge page less than 3 pages.

config CGROUP_PERF
	bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
	depends on PERF_EVENTS && CGROUPS
	help
	  This option extends the per-cpu mode to restrict monitoring to
	  threads which belong to the cgroup specified and run on the
	  designated cpu.

	  Say N if unsure.

menuconfig CGROUP_SCHED
	bool "Group CPU scheduler"
	default n
	help
	  This feature lets CPU scheduler recognize task groups and control CPU
	  bandwidth allocation to such task groups. It uses cgroups to group
	  tasks.

if CGROUP_SCHED
config FAIR_GROUP_SCHED
	bool "Group scheduling for SCHED_OTHER"
	depends on CGROUP_SCHED
	default CGROUP_SCHED

config CFS_BANDWIDTH
	bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
	depends on FAIR_GROUP_SCHED
	default n
	help
	  This option allows users to define CPU bandwidth rates (limits) for
	  tasks running within the fair group scheduler.  Groups with no limit
	  set are considered to be unconstrained and will run with no
	  restriction.
	  See tip/Documentation/scheduler/sched-bwc.txt for more information.

config RT_GROUP_SCHED
	bool "Group scheduling for SCHED_RR/FIFO"
	depends on CGROUP_SCHED
	default n
	help
	  This feature lets you explicitly allocate real CPU bandwidth
	  to task groups. If enabled, it will also make it impossible to
	  schedule realtime tasks for non-root users until you allocate
	  realtime bandwidth for them.
	  See Documentation/scheduler/sched-rt-group.txt for more information.

endif #CGROUP_SCHED

config BLK_CGROUP
	bool "Block IO controller"
	depends on BLOCK
	default n
	---help---
	Generic block IO controller cgroup interface. This is the common
	cgroup interface which should be used by various IO controlling
	policies.

	Currently, CFQ IO scheduler uses it to recognize task groups and
	control disk bandwidth allocation (proportional time slice allocation)
	to such task groups. It is also used by bio throttling logic in
	block layer to implement upper limit in IO rates on a device.

	This option only enables generic Block IO controller infrastructure.
	One needs to also enable actual IO controlling logic/policy. For
	enabling proportional weight division of disk bandwidth in CFQ, set
	CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
	CONFIG_BLK_DEV_THROTTLING=y.

	See Documentation/cgroups/blkio-controller.txt for more information.

config DEBUG_BLK_CGROUP
	bool "Enable Block IO controller debugging"
	depends on BLK_CGROUP
	default n
	---help---
	Enable some debugging help. Currently it exports additional stat
	files in a cgroup which can be useful for debugging.

endif # CGROUPS

config CHECKPOINT_RESTORE
	bool "Checkpoint/restore support" if EXPERT
	default n
	help
	  Enables additional kernel features in a sake of checkpoint/restore.
	  In particular it adds auxiliary prctl codes to setup process text,
	  data and heap segment sizes, and a few additional /proc filesystem
	  entries.

	  If unsure, say N here.

menuconfig NAMESPACES
	bool "Namespaces support" if EXPERT
	default !EXPERT
	help
	  Provides the way to make tasks work with different objects using
	  the same id. For example same IPC id may refer to different objects
	  or same user id or pid may refer to different tasks when used in
	  different namespaces.

if NAMESPACES

config UTS_NS
	bool "UTS namespace"
	default y
	help
	  In this namespace tasks see different info provided with the
	  uname() system call

config IPC_NS
	bool "IPC namespace"
	depends on (SYSVIPC || POSIX_MQUEUE)
	default y
	help
	  In this namespace tasks work with IPC ids which correspond to
	  different IPC objects in different namespaces.

config USER_NS
	bool "User namespace"
	default n
	help
	  This allows containers, i.e. vservers, to use user namespaces
	  to provide different user info for different servers.

	  When user namespaces are enabled in the kernel it is
	  recommended that the MEMCG and MEMCG_KMEM options also be
	  enabled and that user-space use the memory control groups to
	  limit the amount of memory a memory unprivileged users can
	  use.

	  If unsure, say N.

config PID_NS
	bool "PID Namespaces"
	default y
	help
	  Support process id namespaces.  This allows having multiple
	  processes with the same pid as long as they are in different
	  pid namespaces.  This is a building block of containers.

config NET_NS
	bool "Network namespace"
	depends on NET
	default y
	help
	  Allow user space to create what appear to be multiple instances
	  of the network stack.

endif # NAMESPACES

config SCHED_AUTOGROUP
	bool "Automatic process group scheduling"
	select CGROUPS
	select CGROUP_SCHED
	select FAIR_GROUP_SCHED
	help
	  This option optimizes the scheduler for common desktop workloads by
	  automatically creating and populating task groups.  This separation
	  of workloads isolates aggressive CPU burners (like build jobs) from
	  desktop applications.  Task group autogeneration is currently based
	  upon task session.

config SYSFS_DEPRECATED
	bool "Enable deprecated sysfs features to support old userspace tools"
	depends on SYSFS
	default n
	help
	  This option adds code that switches the layout of the "block" class
	  devices, to not show up in /sys/class/block/, but only in
	  /sys/block/.

	  This switch is only active when the sysfs.deprecated=1 boot option is
	  passed or the SYSFS_DEPRECATED_V2 option is set.

	  This option allows new kernels to run on old distributions and tools,
	  which might get confused by /sys/class/block/. Since 2007/2008 all
	  major distributions and tools handle this just fine.

	  Recent distributions and userspace tools after 2009/2010 depend on
	  the existence of /sys/class/block/, and will not work with this
	  option enabled.

	  Only if you are using a new kernel on an old distribution, you might
	  need to say Y here.

config SYSFS_DEPRECATED_V2
	bool "Enable deprecated sysfs features by default"
	default n
	depends on SYSFS
	depends on SYSFS_DEPRECATED
	help
	  Enable deprecated sysfs by default.

	  See the CONFIG_SYSFS_DEPRECATED option for more details about this
	  option.

	  Only if you are using a new kernel on an old distribution, you might
	  need to say Y here. Even then, odds are you would not need it
	  enabled, you can always pass the boot option if absolutely necessary.

config RELAY
	bool "Kernel->user space relay support (formerly relayfs)"
	help
	  This option enables support for relay interface support in
	  certain file systems (such as debugfs).
	  It is designed to provide an efficient mechanism for tools and
	  facilities to relay large amounts of data from kernel space to
	  user space.

	  If unsure, say N.

config BLK_DEV_INITRD
	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
	depends on BROKEN || !FRV
	help
	  The initial RAM filesystem is a ramfs which is loaded by the
	  boot loader (loadlin or lilo) and that is mounted as root
	  before the normal boot procedure. It is typically used to
	  load modules needed to mount the "real" root file system,
	  etc. See <file:Documentation/initrd.txt> for details.

	  If RAM disk support (BLK_DEV_RAM) is also included, this
	  also enables initial RAM disk (initrd) support and adds
	  15 Kbytes (more on some other architectures) to the kernel size.

	  If unsure say Y.

if BLK_DEV_INITRD

source "usr/Kconfig"

endif

config CC_OPTIMIZE_FOR_SIZE
	bool "Optimize for size"
	help
	  Enabling this option will pass "-Os" instead of "-O2" to gcc
	  resulting in a smaller kernel.

	  If unsure, say N.

config SYSCTL
	bool

config ANON_INODES
	bool

config HAVE_UID16
	bool

config SYSCTL_EXCEPTION_TRACE
	bool
	help
	  Enable support for /proc/sys/debug/exception-trace.

config SYSCTL_ARCH_UNALIGN_NO_WARN
	bool
	help
	  Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
	  Allows arch to define/use @no_unaligned_warning to possibly warn
	  about unaligned access emulation going on under the hood.

config SYSCTL_ARCH_UNALIGN_ALLOW
	bool
	help
	  Enable support for /proc/sys/kernel/unaligned-trap
	  Allows arches to define/use @unaligned_enabled to runtime toggle
	  the unaligned access emulation.
	  see arch/parisc/kernel/unaligned.c for reference

config HAVE_PCSPKR_PLATFORM
	bool

menuconfig EXPERT
	bool "Configure standard kernel features (expert users)"
	# Unhide debug options, to make the on-by-default options visible
	select DEBUG_KERNEL
	help
	  This option allows certain base kernel options and settings
          to be disabled or tweaked. This is for specialized
          environments which can tolerate a "non-standard" kernel.
          Only use this if you really know what you are doing.

config UID16
	bool "Enable 16-bit UID system calls" if EXPERT
	depends on HAVE_UID16
	default y
	help
	  This enables the legacy 16-bit UID syscall wrappers.

config SGETMASK_SYSCALL
	bool "sgetmask/ssetmask syscalls support" if EXPERT
	def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
	---help---
	  sys_sgetmask and sys_ssetmask are obsolete system calls
	  no longer supported in libc but still enabled by default in some
	  architectures.

	  If unsure, leave the default option here.

config SYSFS_SYSCALL
	bool "Sysfs syscall support" if EXPERT
	default y
	---help---
	  sys_sysfs is an obsolete system call no longer supported in libc.
	  Note that disabling this option is more secure but might break
	  compatibility with some systems.

	  If unsure say Y here.

config SYSCTL_SYSCALL
	bool "Sysctl syscall support" if EXPERT
	depends on PROC_SYSCTL
	default n
	select SYSCTL
	---help---
	  sys_sysctl uses binary paths that have been found challenging
	  to properly maintain and use.  The interface in /proc/sys
	  using paths with ascii names is now the primary path to this
	  information.

	  Almost nothing using the binary sysctl interface so if you are
	  trying to save some space it is probably safe to disable this,
	  making your kernel marginally smaller.

	  If unsure say N here.

config KALLSYMS
	 bool "Load all symbols for debugging/ksymoops" if EXPERT
	 default y
	 help
	   Say Y here to let the kernel print out symbolic crash information and
	   symbolic stack backtraces. This increases the size of the kernel
	   somewhat, as all symbols have to be loaded into the kernel image.

config KALLSYMS_ALL
	bool "Include all symbols in kallsyms"
	depends on DEBUG_KERNEL && KALLSYMS
	help
	   Normally kallsyms only contains the symbols of functions for nicer
	   OOPS messages and backtraces (i.e., symbols from the text and inittext
	   sections). This is sufficient for most cases. And only in very rare
	   cases (e.g., when a debugger is used) all symbols are required (e.g.,
	   names of variables from the data sections, etc).

	   This option makes sure that all symbols are loaded into the kernel
	   image (i.e., symbols from all sections) in cost of increased kernel
	   size (depending on the kernel configuration, it may be 300KiB or
	   something like this).

	   Say N unless you really need all symbols.

config PRINTK
	default y
	bool "Enable support for printk" if EXPERT
	select IRQ_WORK
	help
	  This option enables normal printk support. Removing it
	  eliminates most of the message strings from the kernel image
	  and makes the kernel more or less silent. As this makes it
	  very difficult to diagnose system problems, saying N here is
	  strongly discouraged.

config BUG
	bool "BUG() support" if EXPERT
	default y
	help
          Disabling this option eliminates support for BUG and WARN, reducing
          the size of your kernel image and potentially quietly ignoring
          numerous fatal conditions. You should only consider disabling this
          option for embedded systems with no facilities for reporting errors.
          Just say Y.

config ELF_CORE
	depends on COREDUMP
	default y
	bool "Enable ELF core dumps" if EXPERT
	help
	  Enable support for generating core dumps. Disabling saves about 4k.


config PCSPKR_PLATFORM
	bool "Enable PC-Speaker support" if EXPERT
	depends on HAVE_PCSPKR_PLATFORM
	select I8253_LOCK
	default y
	help
          This option allows to disable the internal PC-Speaker
          support, saving some memory.

config BASE_FULL
	default y
	bool "Enable full-sized data structures for core" if EXPERT
	help
	  Disabling this option reduces the size of miscellaneous core
	  kernel data structures. This saves memory on small machines,
	  but may reduce performance.

config FUTEX
	bool "Enable futex support" if EXPERT
	default y
	select RT_MUTEXES
	help
	  Disabling this option will cause the kernel to be built without
	  support for "fast userspace mutexes".  The resulting kernel may not
	  run glibc-based applications correctly.

config HAVE_FUTEX_CMPXCHG
	bool
	help
	  Architectures should select this if futex_atomic_cmpxchg_inatomic()
	  is implemented and always working. This removes a couple of runtime
	  checks.

config EPOLL
	bool "Enable eventpoll support" if EXPERT
	default y
	select ANON_INODES
	help
	  Disabling this option will cause the kernel to be built without
	  support for epoll family of system calls.

config SIGNALFD
	bool "Enable signalfd() system call" if EXPERT
	select ANON_INODES
	default y
	help
	  Enable the signalfd() system call that allows to receive signals
	  on a file descriptor.

	  If unsure, say Y.

config TIMERFD
	bool "Enable timerfd() system call" if EXPERT
	select ANON_INODES
	default y
	help
	  Enable the timerfd() system call that allows to receive timer
	  events on a file descriptor.

	  If unsure, say Y.

config EVENTFD
	bool "Enable eventfd() system call" if EXPERT
	select ANON_INODES
	default y
	help
	  Enable the eventfd() system call that allows to receive both
	  kernel notification (ie. KAIO) or userspace notifications.

	  If unsure, say Y.

config SHMEM
	bool "Use full shmem filesystem" if EXPERT
	default y
	depends on MMU
	help
	  The shmem is an internal filesystem used to manage shared memory.
	  It is backed by swap and manages resource limits. It is also exported
	  to userspace as tmpfs if TMPFS is enabled. Disabling this
	  option replaces shmem and tmpfs with the much simpler ramfs code,
	  which may be appropriate on small systems without swap.

config AIO
	bool "Enable AIO support" if EXPERT
	default y
	help
	  This option enables POSIX asynchronous I/O which may by used
	  by some high performance threaded applications. Disabling
	  this option saves about 7k.

config PCI_QUIRKS
	default y
	bool "Enable PCI quirk workarounds" if EXPERT
	depends on PCI
	help
	  This enables workarounds for various PCI chipset
	  bugs/quirks. Disable this only if your target machine is
	  unaffected by PCI quirks.

config EMBEDDED
	bool "Embedded system"
	option allnoconfig_y
	select EXPERT
	help
	  This option should be enabled if compiling the kernel for
	  an embedded system so certain expert options are available
	  for configuration.

config HAVE_PERF_EVENTS
	bool
	help
	  See tools/perf/design.txt for details.

config PERF_USE_VMALLOC
	bool
	help
	  See tools/perf/design.txt for details

menu "Kernel Performance Events And Counters"

config PERF_EVENTS
	bool "Kernel performance events and counters"
	default y if PROFILING
	depends on HAVE_PERF_EVENTS
	select ANON_INODES
	select IRQ_WORK
	help
	  Enable kernel support for various performance events provided
	  by software and hardware.

	  Software events are supported either built-in or via the
	  use of generic tracepoints.

	  Most modern CPUs support performance events via performance
	  counter registers. These registers count the number of certain
	  types of hw events: such as instructions executed, cachemisses
	  suffered, or branches mis-predicted - without slowing down the
	  kernel or applications. These registers can also trigger interrupts
	  when a threshold number of events have passed - and can thus be
	  used to profile the code that runs on that CPU.

	  The Linux Performance Event subsystem provides an abstraction of
	  these software and hardware event capabilities, available via a
	  system call and used by the "perf" utility in tools/perf/. It
	  provides per task and per CPU counters, and it provides event
	  capabilities on top of those.

	  Say Y if unsure.

config DEBUG_PERF_USE_VMALLOC
	default n
	bool "Debug: use vmalloc to back perf mmap() buffers"
	depends on PERF_EVENTS && DEBUG_KERNEL
	select PERF_USE_VMALLOC
	help
	 Use vmalloc memory to back perf mmap() buffers.

	 Mostly useful for debugging the vmalloc code on platforms
	 that don't require it.

	 Say N if unsure.

endmenu

config VM_EVENT_COUNTERS
	default y
	bool "Enable VM event counters for /proc/vmstat" if EXPERT
	help
	  VM event counters are needed for event counts to be shown.
	  This option allows the disabling of the VM event counters
	  on EXPERT systems.  /proc/vmstat will only show page counts
	  if VM event counters are disabled.

config SLUB_DEBUG
	default y
	bool "Enable SLUB debugging support" if EXPERT
	depends on SLUB && SYSFS
	help
	  SLUB has extensive debug support features. Disabling these can
	  result in significant savings in code size. This also disables
	  SLUB sysfs support. /sys/slab will not exist and there will be
	  no support for cache validation etc.

config COMPAT_BRK
	bool "Disable heap randomization"
	default y
	help
	  Randomizing heap placement makes heap exploits harder, but it
	  also breaks ancient binaries (including anything libc5 based).
	  This option changes the bootup default to heap randomization
	  disabled, and can be overridden at runtime by setting
	  /proc/sys/kernel/randomize_va_space to 2.

	  On non-ancient distros (post-2000 ones) N is usually a safe choice.

choice
	prompt "Choose SLAB allocator"
	default SLUB
	help
	   This option allows to select a slab allocator.

config SLAB
	bool "SLAB"
	help
	  The regular slab allocator that is established and known to work
	  well in all environments. It organizes cache hot objects in
	  per cpu and per node queues.

config SLUB
	bool "SLUB (Unqueued Allocator)"
	help
	   SLUB is a slab allocator that minimizes cache line usage
	   instead of managing queues of cached objects (SLAB approach).
	   Per cpu caching is realized using slabs of objects instead
	   of queues of objects. SLUB can use memory efficiently
	   and has enhanced diagnostics. SLUB is the default choice for
	   a slab allocator.

config SLOB
	depends on EXPERT
	bool "SLOB (Simple Allocator)"
	help
	   SLOB replaces the stock allocator with a drastically simpler
	   allocator. SLOB is generally more space efficient but
	   does not perform as well on large systems.

endchoice

config SLUB_CPU_PARTIAL
	default y
	depends on SLUB && SMP
	bool "SLUB per cpu partial cache"
	help
	  Per cpu partial caches accellerate objects allocation and freeing
	  that is local to a processor at the price of more indeterminism
	  in the latency of the free. On overflow these caches will be cleared
	  which requires the taking of locks that may cause latency spikes.
	  Typically one would choose no for a realtime system.

config MMAP_ALLOW_UNINITIALIZED
	bool "Allow mmapped anonymous memory to be uninitialized"
	depends on EXPERT && !MMU
	default n
	help
	  Normally, and according to the Linux spec, anonymous memory obtained
	  from mmap() has it's contents cleared before it is passed to
	  userspace.  Enabling this config option allows you to request that
	  mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
	  providing a huge performance boost.  If this option is not enabled,
	  then the flag will be ignored.

	  This is taken advantage of by uClibc's malloc(), and also by
	  ELF-FDPIC binfmt's brk and stack allocator.

	  Because of the obvious security issues, this option should only be
	  enabled on embedded devices where you control what is run in
	  userspace.  Since that isn't generally a problem on no-MMU systems,
	  it is normally safe to say Y here.

	  See Documentation/nommu-mmap.txt for more information.

config SYSTEM_TRUSTED_KEYRING
	bool "Provide system-wide ring of trusted keys"
	depends on KEYS
	help
	  Provide a system keyring to which trusted keys can be added.  Keys in
	  the keyring are considered to be trusted.  Keys may be added at will
	  by the kernel from compiled-in data and from hardware key stores, but
	  userspace may only add extra keys if those keys can be verified by
	  keys already in the keyring.

	  Keys in this keyring are used by module signature checking.

config PROFILING
	bool "Profiling support"
	help
	  Say Y here to enable the extended profiling support mechanisms used
	  by profilers such as OProfile.

#
# Place an empty function call at each tracepoint site. Can be
# dynamically changed for a probe function.
#
config TRACEPOINTS
	bool

source "arch/Kconfig"

endmenu		# General setup

config HAVE_GENERIC_DMA_COHERENT
	bool
	default n

config SLABINFO
	bool
	depends on PROC_FS
	depends on SLAB || SLUB_DEBUG
	default y

config RT_MUTEXES
	boolean

config BASE_SMALL
	int
	default 0 if BASE_FULL
	default 1 if !BASE_FULL

menuconfig MODULES
	bool "Enable loadable module support"
	option modules
	help
	  Kernel modules are small pieces of compiled code which can
	  be inserted in the running kernel, rather than being
	  permanently built into the kernel.  You use the "modprobe"
	  tool to add (and sometimes remove) them.  If you say Y here,
	  many parts of the kernel can be built as modules (by
	  answering M instead of Y where indicated): this is most
	  useful for infrequently used options which are not required
	  for booting.  For more information, see the man pages for
	  modprobe, lsmod, modinfo, insmod and rmmod.

	  If you say Y here, you will need to run "make
	  modules_install" to put the modules under /lib/modules/
	  where modprobe can find them (you may need to be root to do
	  this).

	  If unsure, say Y.

if MODULES

config MODULE_FORCE_LOAD
	bool "Forced module loading"
	default n
	help
	  Allow loading of modules without version information (ie. modprobe
	  --force).  Forced module loading sets the 'F' (forced) taint flag and
	  is usually a really bad idea.

config MODULE_UNLOAD
	bool "Module unloading"
	help
	  Without this option you will not be able to unload any
	  modules (note that some modules may not be unloadable
	  anyway), which makes your kernel smaller, faster
	  and simpler.  If unsure, say Y.

config MODULE_FORCE_UNLOAD
	bool "Forced module unloading"
	depends on MODULE_UNLOAD
	help
	  This option allows you to force a module to unload, even if the
	  kernel believes it is unsafe: the kernel will remove the module
	  without waiting for anyone to stop using it (using the -f option to
	  rmmod).  This is mainly for kernel developers and desperate users.
	  If unsure, say N.

config MODVERSIONS
	bool "Module versioning support"
	help
	  Usually, you have to use modules compiled with your kernel.
	  Saying Y here makes it sometimes possible to use modules
	  compiled for different kernels, by adding enough information
	  to the modules to (hopefully) spot any changes which would
	  make them incompatible with the kernel you are running.  If
	  unsure, say N.

config MODULE_SRCVERSION_ALL
	bool "Source checksum for all modules"
	help
	  Modules which contain a MODULE_VERSION get an extra "srcversion"
	  field inserted into their modinfo section, which contains a
    	  sum of the source files which made it.  This helps maintainers
	  see exactly which source was used to build a module (since
	  others sometimes change the module source without updating
	  the version).  With this option, such a "srcversion" field
	  will be created for all modules.  If unsure, say N.

config MODULE_SIG
	bool "Module signature verification"
	depends on MODULES
	select SYSTEM_TRUSTED_KEYRING
	select KEYS
	select CRYPTO
	select ASYMMETRIC_KEY_TYPE
	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
	select PUBLIC_KEY_ALGO_RSA
	select ASN1
	select OID_REGISTRY
	select X509_CERTIFICATE_PARSER
	help
	  Check modules for valid signatures upon load: the signature
	  is simply appended to the module. For more information see
	  Documentation/module-signing.txt.

	  !!!WARNING!!!  If you enable this option, you MUST make sure that the
	  module DOES NOT get stripped after being signed.  This includes the
	  debuginfo strip done by some packagers (such as rpmbuild) and
	  inclusion into an initramfs that wants the module size reduced.

config MODULE_SIG_FORCE
	bool "Require modules to be validly signed"
	depends on MODULE_SIG
	help
	  Reject unsigned modules or signed modules for which we don't have a
	  key.  Without this, such modules will simply taint the kernel.

config MODULE_SIG_ALL
	bool "Automatically sign all modules"
	default y
	depends on MODULE_SIG
	help
	  Sign all modules during make modules_install. Without this option,
	  modules must be signed manually, using the scripts/sign-file tool.

comment "Do not forget to sign required modules with scripts/sign-file"
	depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL

choice
	prompt "Which hash algorithm should modules be signed with?"
	depends on MODULE_SIG
	help
	  This determines which sort of hashing algorithm will be used during
	  signature generation.  This algorithm _must_ be built into the kernel
	  directly so that signature verification can take place.  It is not
	  possible to load a signed module containing the algorithm to check
	  the signature on that module.

config MODULE_SIG_SHA1
	bool "Sign modules with SHA-1"
	select CRYPTO_SHA1

config MODULE_SIG_SHA224
	bool "Sign modules with SHA-224"
	select CRYPTO_SHA256

config MODULE_SIG_SHA256
	bool "Sign modules with SHA-256"
	select CRYPTO_SHA256

config MODULE_SIG_SHA384
	bool "Sign modules with SHA-384"
	select CRYPTO_SHA512

config MODULE_SIG_SHA512
	bool "Sign modules with SHA-512"
	select CRYPTO_SHA512

endchoice

config MODULE_SIG_HASH
	string
	depends on MODULE_SIG
	default "sha1" if MODULE_SIG_SHA1
	default "sha224" if MODULE_SIG_SHA224
	default "sha256" if MODULE_SIG_SHA256
	default "sha384" if MODULE_SIG_SHA384
	default "sha512" if MODULE_SIG_SHA512

endif # MODULES

config INIT_ALL_POSSIBLE
	bool
	help
	  Back when each arch used to define their own cpu_online_mask and
	  cpu_possible_mask, some of them chose to initialize cpu_possible_mask
	  with all 1s, and others with all 0s.  When they were centralised,
	  it was better to provide this option than to break all the archs
	  and have several arch maintainers pursuing me down dark alleys.

config STOP_MACHINE
	bool
	default y
	depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
	help
	  Need stop_machine() primitive.

source "block/Kconfig"

config PREEMPT_NOTIFIERS
	bool

config PADATA
	depends on SMP
	bool

# Can be selected by architectures with broken toolchains
# that get confused by correct const<->read_only section
# mappings
config BROKEN_RODATA
	bool

config ASN1
	tristate
	help
	  Build a simple ASN.1 grammar compiler that produces a bytecode output
	  that can be interpreted by the ASN.1 stream decoder and used to
	  inform it as to what tags are to be expected in a stream and what
	  functions to call on what tags.

source "kernel/Kconfig.locks"