1# 2# Timer subsystem related configuration options 3# 4 5# Options selectable by arch Kconfig 6 7# Watchdog function for clocksources to detect instabilities 8config CLOCKSOURCE_WATCHDOG 9 bool 10 11# Architecture has extra clocksource data 12config ARCH_CLOCKSOURCE_DATA 13 bool 14 15# Clocksources require validation of the clocksource against the last 16# cycle update - x86/TSC misfeature 17config CLOCKSOURCE_VALIDATE_LAST_CYCLE 18 bool 19 20# Timekeeping vsyscall support 21config GENERIC_TIME_VSYSCALL 22 bool 23 24# Old style timekeeping 25config ARCH_USES_GETTIMEOFFSET 26 bool 27 28# The generic clock events infrastructure 29config GENERIC_CLOCKEVENTS 30 bool 31 32# Architecture can handle broadcast in a driver-agnostic way 33config ARCH_HAS_TICK_BROADCAST 34 bool 35 36# Clockevents broadcasting infrastructure 37config GENERIC_CLOCKEVENTS_BROADCAST 38 bool 39 depends on GENERIC_CLOCKEVENTS 40 41# Automatically adjust the min. reprogramming time for 42# clock event device 43config GENERIC_CLOCKEVENTS_MIN_ADJUST 44 bool 45 46# Generic update of CMOS clock 47config GENERIC_CMOS_UPDATE 48 bool 49 50if GENERIC_CLOCKEVENTS 51menu "Timers subsystem" 52 53# Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is 54# only related to the tick functionality. Oneshot clockevent devices 55# are supported independent of this. 56config TICK_ONESHOT 57 bool 58 59config NO_HZ_COMMON 60 bool 61 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 62 select TICK_ONESHOT 63 64choice 65 prompt "Timer tick handling" 66 default NO_HZ_IDLE if NO_HZ 67 68config HZ_PERIODIC 69 bool "Periodic timer ticks (constant rate, no dynticks)" 70 help 71 This option keeps the tick running periodically at a constant 72 rate, even when the CPU doesn't need it. 73 74config NO_HZ_IDLE 75 bool "Idle dynticks system (tickless idle)" 76 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 77 select NO_HZ_COMMON 78 help 79 This option enables a tickless idle system: timer interrupts 80 will only trigger on an as-needed basis when the system is idle. 81 This is usually interesting for energy saving. 82 83 Most of the time you want to say Y here. 84 85config NO_HZ_FULL 86 bool "Full dynticks system (tickless)" 87 # NO_HZ_COMMON dependency 88 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 89 # We need at least one periodic CPU for timekeeping 90 depends on SMP 91 depends on HAVE_CONTEXT_TRACKING 92 # VIRT_CPU_ACCOUNTING_GEN dependency 93 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 94 select NO_HZ_COMMON 95 select RCU_NOCB_CPU 96 select VIRT_CPU_ACCOUNTING_GEN 97 select IRQ_WORK 98 select CPU_ISOLATION 99 help 100 Adaptively try to shutdown the tick whenever possible, even when 101 the CPU is running tasks. Typically this requires running a single 102 task on the CPU. Chances for running tickless are maximized when 103 the task mostly runs in userspace and has few kernel activity. 104 105 You need to fill up the nohz_full boot parameter with the 106 desired range of dynticks CPUs. 107 108 This is implemented at the expense of some overhead in user <-> kernel 109 transitions: syscalls, exceptions and interrupts. Even when it's 110 dynamically off. 111 112 Say N. 113 114endchoice 115 116config NO_HZ 117 bool "Old Idle dynticks config" 118 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 119 help 120 This is the old config entry that enables dynticks idle. 121 We keep it around for a little while to enforce backward 122 compatibility with older config files. 123 124config HIGH_RES_TIMERS 125 bool "High Resolution Timer Support" 126 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 127 select TICK_ONESHOT 128 help 129 This option enables high resolution timer support. If your 130 hardware is not capable then this option only increases 131 the size of the kernel image. 132 133endmenu 134endif 135