## Timer subsystem related configuration options# # Options selectable by arch Kconfig # Watchdog function for clocksources to detect instabilitiesconfig CLOCKSOURCE_WATCHDOG	bool # Architecture has extra clocksource dataconfig ARCH_CLOCKSOURCE_DATA	bool # Timekeeping vsyscall supportconfig GENERIC_TIME_VSYSCALL	bool # Timekeeping vsyscall supportconfig GENERIC_TIME_VSYSCALL_OLD	bool # ktime_t scalar 64bit nsec representationconfig KTIME_SCALAR	bool # Old style timekeepingconfig ARCH_USES_GETTIMEOFFSET	bool # The generic clock events infrastructureconfig GENERIC_CLOCKEVENTS	bool # Migration helper. Builds, but does not invokeconfig GENERIC_CLOCKEVENTS_BUILD	bool	default y	depends on GENERIC_CLOCKEVENTS # Architecture can handle broadcast in a driver-agnostic wayconfig ARCH_HAS_TICK_BROADCAST	bool # Clockevents broadcasting infrastructureconfig GENERIC_CLOCKEVENTS_BROADCAST	bool	depends on GENERIC_CLOCKEVENTS # Automatically adjust the min. reprogramming time for# clock event deviceconfig GENERIC_CLOCKEVENTS_MIN_ADJUST	bool # Generic update of CMOS clockconfig GENERIC_CMOS_UPDATE	bool if GENERIC_CLOCKEVENTSmenu "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	# RCU_USER_QS dependency	depends on HAVE_CONTEXT_TRACKING	# VIRT_CPU_ACCOUNTING_GEN dependency	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN	select NO_HZ_COMMON	select RCU_USER_QS	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"       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. endmenuendif