#
  # Timer subsystem related configuration options
  #

  # Options selectable by arch Kconfig
  
  # Watchdog function for clocksources to detect instabilities
  config CLOCKSOURCE_WATCHDOG
  	bool
  
  # Architecture has extra clocksource data
  config ARCH_CLOCKSOURCE_DATA
  	bool

  # Clocksources require validation of the clocksource against the last
  # cycle update - x86/TSC misfeature
  config CLOCKSOURCE_VALIDATE_LAST_CYCLE
  	bool

  # Timekeeping vsyscall support

  config GENERIC_TIME_VSYSCALL
  	bool
  
  # Timekeeping vsyscall support

  config GENERIC_TIME_VSYSCALL_OLD

  	bool

  # Old style timekeeping
  config ARCH_USES_GETTIMEOFFSET
  	bool
  
  # The generic clock events infrastructure
  config GENERIC_CLOCKEVENTS
  	bool

  # Architecture can handle broadcast in a driver-agnostic way
  config ARCH_HAS_TICK_BROADCAST
  	bool

  # Clockevents broadcasting infrastructure
  config GENERIC_CLOCKEVENTS_BROADCAST
  	bool
  	depends on GENERIC_CLOCKEVENTS

  # Automatically adjust the min. reprogramming time for
  # clock event device
  config GENERIC_CLOCKEVENTS_MIN_ADJUST
  	bool

  # Generic update of CMOS clock
  config GENERIC_CMOS_UPDATE
  	bool

  
  if GENERIC_CLOCKEVENTS
  menu "Timers subsystem"

  # Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is

  # only related to the tick functionality. Oneshot clockevent devices
  # are supported independ of this.
  config TICK_ONESHOT
  	bool

  config NO_HZ_COMMON
  	bool
  	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
  	select TICK_ONESHOT

  choice
  	prompt "Timer tick handling"
  	default NO_HZ_IDLE if NO_HZ

  config HZ_PERIODIC

  	bool "Periodic timer ticks (constant rate, no dynticks)"
  	help
  	  This option keeps the tick running periodically at a constant
  	  rate, even when the CPU doesn't need it.
  
  config NO_HZ_IDLE
  	bool "Idle dynticks system (tickless idle)"

  	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS

  	select NO_HZ_COMMON

  	help

  	  This option enables a tickless idle system: timer interrupts
  	  will only trigger on an as-needed basis when the system is idle.
  	  This is usually interesting for energy saving.
  
  	  Most of the time you want to say Y here.

  config NO_HZ_FULL

  	bool "Full dynticks system (tickless)"

  	# NO_HZ_COMMON dependency

  	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS

  	# We need at least one periodic CPU for timekeeping
  	depends on SMP

  	depends on HAVE_CONTEXT_TRACKING

  	# VIRT_CPU_ACCOUNTING_GEN dependency

  	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN

  	select NO_HZ_COMMON

  	select RCU_NOCB_CPU

  	select VIRT_CPU_ACCOUNTING_GEN

  	select IRQ_WORK

  	help
  	 Adaptively try to shutdown the tick whenever possible, even when

  	 the CPU is running tasks. Typically this requires running a single
  	 task on the CPU. Chances for running tickless are maximized when
  	 the task mostly runs in userspace and has few kernel activity.

  	 You need to fill up the nohz_full boot parameter with the

  	 desired range of dynticks CPUs.
  
  	 This is implemented at the expense of some overhead in user <-> kernel
  	 transitions: syscalls, exceptions and interrupts. Even when it's
  	 dynamically off.
  
  	 Say N.

  endchoice

  config NO_HZ_FULL_ALL

         bool "Full dynticks system on all CPUs by default (except CPU 0)"

         depends on NO_HZ_FULL
         help
           If the user doesn't pass the nohz_full boot option to
  	 define the range of full dynticks CPUs, consider that all
  	 CPUs in the system are full dynticks by default.
  	 Note the boot CPU will still be kept outside the range to
  	 handle the timekeeping duty.

  config NO_HZ_FULL_SYSIDLE
  	bool "Detect full-system idle state for full dynticks system"
  	depends on NO_HZ_FULL
  	default n
  	help
  	 At least one CPU must keep the scheduling-clock tick running for
  	 timekeeping purposes whenever there is a non-idle CPU, where
  	 "non-idle" also includes dynticks CPUs as long as they are
  	 running non-idle tasks.  Because the underlying adaptive-tick
  	 support cannot distinguish between all CPUs being idle and
  	 all CPUs each running a single task in dynticks mode, the
  	 underlying support simply ensures that there is always a CPU
  	 handling the scheduling-clock tick, whether or not all CPUs
  	 are idle.  This Kconfig option enables scalable detection of
  	 the all-CPUs-idle state, thus allowing the scheduling-clock
  	 tick to be disabled when all CPUs are idle.  Note that scalable
  	 detection of the all-CPUs-idle state means that larger systems
  	 will be slower to declare the all-CPUs-idle state.
  
  	 Say Y if you would like to help debug all-CPUs-idle detection.
  
  	 Say N if you are unsure.

  config NO_HZ_FULL_SYSIDLE_SMALL
  	int "Number of CPUs above which large-system approach is used"
  	depends on NO_HZ_FULL_SYSIDLE
  	range 1 NR_CPUS
  	default 8
  	help
  	 The full-system idle detection mechanism takes a lazy approach
  	 on large systems, as is required to attain decent scalability.
  	 However, on smaller systems, scalability is not anywhere near as
  	 large a concern as is energy efficiency.  The sysidle subsystem
  	 therefore uses a fast but non-scalable algorithm for small
  	 systems and a lazier but scalable algorithm for large systems.
  	 This Kconfig parameter defines the number of CPUs in the largest
  	 system that will be considered to be "small".
  
  	 The default value will be fine in most cases.	Battery-powered
  	 systems that (1) enable NO_HZ_FULL_SYSIDLE, (2) have larger
  	 numbers of CPUs, and (3) are suffering from battery-lifetime
  	 problems due to long sysidle latencies might wish to experiment
  	 with larger values for this Kconfig parameter.  On the other
  	 hand, they might be even better served by disabling NO_HZ_FULL
  	 entirely, given that NO_HZ_FULL is intended for HPC and
  	 real-time workloads that at present do not tend to be run on
  	 battery-powered systems.
  
  	 Take the default if you are unsure.

  config NO_HZ
  	bool "Old Idle dynticks config"
  	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
  	help
  	  This is the old config entry that enables dynticks idle.
  	  We keep it around for a little while to enforce backward
  	  compatibility with older config files.

  config HIGH_RES_TIMERS
  	bool "High Resolution Timer Support"
  	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
  	select TICK_ONESHOT
  	help
  	  This option enables high resolution timer support. If your
  	  hardware is not capable then this option only increases
  	  the size of the kernel image.
  
  endmenu
  endif