# # 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 # Timekeeping vsyscall support config GENERIC_TIME_VSYSCALL bool # Timekeeping vsyscall support config GENERIC_TIME_VSYSCALL_OLD bool # ktime_t scalar 64bit nsec representation config KTIME_SCALAR bool # Old style timekeeping config ARCH_USES_GETTIMEOFFSET bool # The generic clock events infrastructure config GENERIC_CLOCKEVENTS bool # Migration helper. Builds, but does not invoke config GENERIC_CLOCKEVENTS_BUILD bool default y depends on GENERIC_CLOCKEVENTS # 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 # RCU_USER_QS dependency depends on HAVE_CONTEXT_TRACKING # VIRT_CPU_ACCOUNTING_GEN dependency depends on 64BIT select NO_HZ_COMMON select RCU_USER_QS select RCU_NOCB_CPU select VIRT_CPU_ACCOUNTING_GEN select CONTEXT_TRACKING_FORCE 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 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