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 PERIODIC_HZ 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 single task)" 101 # NO_HZ_COMMON dependency 102 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 103 # RCU_USER_QS 104 depends on HAVE_CONTEXT_TRACKING && SMP 105 # RCU_NOCB_CPU dependency 106 depends on TREE_RCU || TREE_PREEMPT_RCU 107 depends on VIRT_CPU_ACCOUNTING_GEN 108 select NO_HZ_COMMON 109 select RCU_USER_QS 110 select RCU_NOCB_CPU 111 select CONTEXT_TRACKING_FORCE 112 help 113 Adaptively try to shutdown the tick whenever possible, even when 114 the CPU is running tasks. Typically this requires running a single 115 task on the CPU. Chances for running tickless are maximized when 116 the task mostly runs in userspace and has few kernel activity. 117 118 You need to fill up the nohz_full boot parameter with the 119 desired range of dynticks CPUs. 120 121 This is implemented at the expense of some overhead in user <-> kernel 122 transitions: syscalls, exceptions and interrupts. Even when it's 123 dynamically off. 124 125 Say N. 126 127endchoice 128 129config NO_HZ 130 bool "Old Idle dynticks config" 131 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 132 help 133 This is the old config entry that enables dynticks idle. 134 We keep it around for a little while to enforce backward 135 compatibility with older config files. 136 137config HIGH_RES_TIMERS 138 bool "High Resolution Timer Support" 139 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 140 select TICK_ONESHOT 141 help 142 This option enables high resolution timer support. If your 143 hardware is not capable then this option only increases 144 the size of the kernel image. 145 146endmenu 147endif 148