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# Platforms has a persistent clock 16config ALWAYS_USE_PERSISTENT_CLOCK 17 bool 18 default n 19 20# Timekeeping vsyscall support 21config GENERIC_TIME_VSYSCALL 22 bool 23 24# Timekeeping vsyscall support 25config GENERIC_TIME_VSYSCALL_OLD 26 bool 27 28# ktime_t scalar 64bit nsec representation 29config KTIME_SCALAR 30 bool 31 32# Old style timekeeping 33config ARCH_USES_GETTIMEOFFSET 34 bool 35 36# The generic clock events infrastructure 37config GENERIC_CLOCKEVENTS 38 bool 39 40# Migration helper. Builds, but does not invoke 41config GENERIC_CLOCKEVENTS_BUILD 42 bool 43 default y 44 depends on GENERIC_CLOCKEVENTS 45 46# Architecture can handle broadcast in a driver-agnostic way 47config ARCH_HAS_TICK_BROADCAST 48 bool 49 50# Clockevents broadcasting infrastructure 51config GENERIC_CLOCKEVENTS_BROADCAST 52 bool 53 depends on GENERIC_CLOCKEVENTS 54 55# Automatically adjust the min. reprogramming time for 56# clock event device 57config GENERIC_CLOCKEVENTS_MIN_ADJUST 58 bool 59 60# Generic update of CMOS clock 61config GENERIC_CMOS_UPDATE 62 bool 63 64if GENERIC_CLOCKEVENTS 65menu "Timers subsystem" 66 67# Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is 68# only related to the tick functionality. Oneshot clockevent devices 69# are supported independ of this. 70config TICK_ONESHOT 71 bool 72 73config NO_HZ_COMMON 74 bool 75 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 76 select TICK_ONESHOT 77 78choice 79 prompt "Timer tick handling" 80 default NO_HZ_IDLE if NO_HZ 81 82config HZ_PERIODIC 83 bool "Periodic timer ticks (constant rate, no dynticks)" 84 help 85 This option keeps the tick running periodically at a constant 86 rate, even when the CPU doesn't need it. 87 88config NO_HZ_IDLE 89 bool "Idle dynticks system (tickless idle)" 90 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 91 select NO_HZ_COMMON 92 help 93 This option enables a tickless idle system: timer interrupts 94 will only trigger on an as-needed basis when the system is idle. 95 This is usually interesting for energy saving. 96 97 Most of the time you want to say Y here. 98 99config NO_HZ_FULL 100 bool "Full dynticks system (tickless)" 101 # NO_HZ_COMMON dependency 102 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 103 # We need at least one periodic CPU for timekeeping 104 depends on SMP 105 # RCU_USER_QS dependency 106 depends on HAVE_CONTEXT_TRACKING 107 # VIRT_CPU_ACCOUNTING_GEN dependency 108 depends on 64BIT 109 select NO_HZ_COMMON 110 select RCU_USER_QS 111 select RCU_NOCB_CPU 112 select VIRT_CPU_ACCOUNTING_GEN 113 select CONTEXT_TRACKING_FORCE 114 select IRQ_WORK 115 help 116 Adaptively try to shutdown the tick whenever possible, even when 117 the CPU is running tasks. Typically this requires running a single 118 task on the CPU. Chances for running tickless are maximized when 119 the task mostly runs in userspace and has few kernel activity. 120 121 You need to fill up the nohz_full boot parameter with the 122 desired range of dynticks CPUs. 123 124 This is implemented at the expense of some overhead in user <-> kernel 125 transitions: syscalls, exceptions and interrupts. Even when it's 126 dynamically off. 127 128 Say N. 129 130endchoice 131 132config NO_HZ_FULL_ALL 133 bool "Full dynticks system on all CPUs by default" 134 depends on NO_HZ_FULL 135 help 136 If the user doesn't pass the nohz_full boot option to 137 define the range of full dynticks CPUs, consider that all 138 CPUs in the system are full dynticks by default. 139 Note the boot CPU will still be kept outside the range to 140 handle the timekeeping duty. 141 142config NO_HZ 143 bool "Old Idle dynticks config" 144 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 145 help 146 This is the old config entry that enables dynticks idle. 147 We keep it around for a little while to enforce backward 148 compatibility with older config files. 149 150config HIGH_RES_TIMERS 151 bool "High Resolution Timer Support" 152 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 153 select TICK_ONESHOT 154 help 155 This option enables high resolution timer support. If your 156 hardware is not capable then this option only increases 157 the size of the kernel image. 158 159endmenu 160endif 161