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# Timekeeping vsyscall support 16config GENERIC_TIME_VSYSCALL 17 bool 18 19# Timekeeping vsyscall support 20config GENERIC_TIME_VSYSCALL_OLD 21 bool 22 23# ktime_t scalar 64bit nsec representation 24config KTIME_SCALAR 25 bool 26 27# Old style timekeeping 28config ARCH_USES_GETTIMEOFFSET 29 bool 30 31# The generic clock events infrastructure 32config GENERIC_CLOCKEVENTS 33 bool 34 35# Migration helper. Builds, but does not invoke 36config GENERIC_CLOCKEVENTS_BUILD 37 bool 38 default y 39 depends on GENERIC_CLOCKEVENTS 40 41# Architecture can handle broadcast in a driver-agnostic way 42config ARCH_HAS_TICK_BROADCAST 43 bool 44 45# Clockevents broadcasting infrastructure 46config GENERIC_CLOCKEVENTS_BROADCAST 47 bool 48 depends on GENERIC_CLOCKEVENTS 49 50# Automatically adjust the min. reprogramming time for 51# clock event device 52config GENERIC_CLOCKEVENTS_MIN_ADJUST 53 bool 54 55# Generic update of CMOS clock 56config GENERIC_CMOS_UPDATE 57 bool 58 59if GENERIC_CLOCKEVENTS 60menu "Timers subsystem" 61 62# Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is 63# only related to the tick functionality. Oneshot clockevent devices 64# are supported independ of this. 65config TICK_ONESHOT 66 bool 67 68config NO_HZ_COMMON 69 bool 70 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 71 select TICK_ONESHOT 72 73choice 74 prompt "Timer tick handling" 75 default NO_HZ_IDLE if NO_HZ 76 77config HZ_PERIODIC 78 bool "Periodic timer ticks (constant rate, no dynticks)" 79 help 80 This option keeps the tick running periodically at a constant 81 rate, even when the CPU doesn't need it. 82 83config NO_HZ_IDLE 84 bool "Idle dynticks system (tickless idle)" 85 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 86 select NO_HZ_COMMON 87 help 88 This option enables a tickless idle system: timer interrupts 89 will only trigger on an as-needed basis when the system is idle. 90 This is usually interesting for energy saving. 91 92 Most of the time you want to say Y here. 93 94config NO_HZ_FULL 95 bool "Full dynticks system (tickless)" 96 # NO_HZ_COMMON dependency 97 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 98 # We need at least one periodic CPU for timekeeping 99 depends on SMP 100 # RCU_USER_QS dependency 101 depends on HAVE_CONTEXT_TRACKING 102 # VIRT_CPU_ACCOUNTING_GEN dependency 103 depends on 64BIT 104 select NO_HZ_COMMON 105 select RCU_USER_QS 106 select RCU_NOCB_CPU 107 select VIRT_CPU_ACCOUNTING_GEN 108 select CONTEXT_TRACKING_FORCE 109 select IRQ_WORK 110 help 111 Adaptively try to shutdown the tick whenever possible, even when 112 the CPU is running tasks. Typically this requires running a single 113 task on the CPU. Chances for running tickless are maximized when 114 the task mostly runs in userspace and has few kernel activity. 115 116 You need to fill up the nohz_full boot parameter with the 117 desired range of dynticks CPUs. 118 119 This is implemented at the expense of some overhead in user <-> kernel 120 transitions: syscalls, exceptions and interrupts. Even when it's 121 dynamically off. 122 123 Say N. 124 125endchoice 126 127config NO_HZ_FULL_ALL 128 bool "Full dynticks system on all CPUs by default" 129 depends on NO_HZ_FULL 130 help 131 If the user doesn't pass the nohz_full boot option to 132 define the range of full dynticks CPUs, consider that all 133 CPUs in the system are full dynticks by default. 134 Note the boot CPU will still be kept outside the range to 135 handle the timekeeping duty. 136 137config NO_HZ 138 bool "Old Idle dynticks config" 139 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 140 help 141 This is the old config entry that enables dynticks idle. 142 We keep it around for a little while to enforce backward 143 compatibility with older config files. 144 145config HIGH_RES_TIMERS 146 bool "High Resolution Timer Support" 147 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 148 select TICK_ONESHOT 149 help 150 This option enables high resolution timer support. If your 151 hardware is not capable then this option only increases 152 the size of the kernel image. 153 154endmenu 155endif 156