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# Architecture has extra clocksource init called from registration 16config ARCH_CLOCKSOURCE_INIT 17 bool 18 19# Clocksources require validation of the clocksource against the last 20# cycle update - x86/TSC misfeature 21config CLOCKSOURCE_VALIDATE_LAST_CYCLE 22 bool 23 24# Timekeeping vsyscall support 25config GENERIC_TIME_VSYSCALL 26 bool 27 28# Old style timekeeping 29config ARCH_USES_GETTIMEOFFSET 30 bool 31 32# The generic clock events infrastructure 33config GENERIC_CLOCKEVENTS 34 bool 35 36# Architecture can handle broadcast in a driver-agnostic way 37config ARCH_HAS_TICK_BROADCAST 38 bool 39 40# Clockevents broadcasting infrastructure 41config GENERIC_CLOCKEVENTS_BROADCAST 42 bool 43 depends on GENERIC_CLOCKEVENTS 44 45# Automatically adjust the min. reprogramming time for 46# clock event device 47config GENERIC_CLOCKEVENTS_MIN_ADJUST 48 bool 49 50# Generic update of CMOS clock 51config GENERIC_CMOS_UPDATE 52 bool 53 54if GENERIC_CLOCKEVENTS 55menu "Timers subsystem" 56 57# Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is 58# only related to the tick functionality. Oneshot clockevent devices 59# are supported independent of this. 60config TICK_ONESHOT 61 bool 62 63config NO_HZ_COMMON 64 bool 65 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 66 select TICK_ONESHOT 67 68choice 69 prompt "Timer tick handling" 70 default NO_HZ_IDLE if NO_HZ 71 72config HZ_PERIODIC 73 bool "Periodic timer ticks (constant rate, no dynticks)" 74 help 75 This option keeps the tick running periodically at a constant 76 rate, even when the CPU doesn't need it. 77 78config NO_HZ_IDLE 79 bool "Idle dynticks system (tickless idle)" 80 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 81 select NO_HZ_COMMON 82 help 83 This option enables a tickless idle system: timer interrupts 84 will only trigger on an as-needed basis when the system is idle. 85 This is usually interesting for energy saving. 86 87 Most of the time you want to say Y here. 88 89config NO_HZ_FULL 90 bool "Full dynticks system (tickless)" 91 # NO_HZ_COMMON dependency 92 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 93 # We need at least one periodic CPU for timekeeping 94 depends on SMP 95 depends on HAVE_CONTEXT_TRACKING 96 # VIRT_CPU_ACCOUNTING_GEN dependency 97 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 98 select NO_HZ_COMMON 99 select RCU_NOCB_CPU 100 select VIRT_CPU_ACCOUNTING_GEN 101 select IRQ_WORK 102 select CPU_ISOLATION 103 help 104 Adaptively try to shutdown the tick whenever possible, even when 105 the CPU is running tasks. Typically this requires running a single 106 task on the CPU. Chances for running tickless are maximized when 107 the task mostly runs in userspace and has few kernel activity. 108 109 You need to fill up the nohz_full boot parameter with the 110 desired range of dynticks CPUs. 111 112 This is implemented at the expense of some overhead in user <-> kernel 113 transitions: syscalls, exceptions and interrupts. Even when it's 114 dynamically off. 115 116 Say N. 117 118endchoice 119 120config CONTEXT_TRACKING 121 bool 122 123config CONTEXT_TRACKING_FORCE 124 bool "Force context tracking" 125 depends on CONTEXT_TRACKING 126 default y if !NO_HZ_FULL 127 help 128 The major pre-requirement for full dynticks to work is to 129 support the context tracking subsystem. But there are also 130 other dependencies to provide in order to make the full 131 dynticks working. 132 133 This option stands for testing when an arch implements the 134 context tracking backend but doesn't yet fullfill all the 135 requirements to make the full dynticks feature working. 136 Without the full dynticks, there is no way to test the support 137 for context tracking and the subsystems that rely on it: RCU 138 userspace extended quiescent state and tickless cputime 139 accounting. This option copes with the absence of the full 140 dynticks subsystem by forcing the context tracking on all 141 CPUs in the system. 142 143 Say Y only if you're working on the development of an 144 architecture backend for the context tracking. 145 146 Say N otherwise, this option brings an overhead that you 147 don't want in production. 148 149config NO_HZ 150 bool "Old Idle dynticks config" 151 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 152 help 153 This is the old config entry that enables dynticks idle. 154 We keep it around for a little while to enforce backward 155 compatibility with older config files. 156 157config HIGH_RES_TIMERS 158 bool "High Resolution Timer Support" 159 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 160 select TICK_ONESHOT 161 help 162 This option enables high resolution timer support. If your 163 hardware is not capable then this option only increases 164 the size of the kernel image. 165 166endmenu 167endif 168