1# SPDX-License-Identifier: GPL-2.0-only 2# 3# Timer subsystem related configuration options 4# 5 6# Options selectable by arch Kconfig 7 8# Watchdog function for clocksources to detect instabilities 9config CLOCKSOURCE_WATCHDOG 10 bool 11 12# Architecture has extra clocksource data 13config ARCH_CLOCKSOURCE_DATA 14 bool 15 16# Architecture has extra clocksource init called from registration 17config ARCH_CLOCKSOURCE_INIT 18 bool 19 20# Clocksources require validation of the clocksource against the last 21# cycle update - x86/TSC misfeature 22config CLOCKSOURCE_VALIDATE_LAST_CYCLE 23 bool 24 25# Timekeeping vsyscall support 26config GENERIC_TIME_VSYSCALL 27 bool 28 29# Old style timekeeping 30config ARCH_USES_GETTIMEOFFSET 31 bool 32 33# The generic clock events infrastructure 34config GENERIC_CLOCKEVENTS 35 bool 36 37# Architecture can handle broadcast in a driver-agnostic way 38config ARCH_HAS_TICK_BROADCAST 39 bool 40 41# Clockevents broadcasting infrastructure 42config GENERIC_CLOCKEVENTS_BROADCAST 43 bool 44 depends on GENERIC_CLOCKEVENTS 45 46# Automatically adjust the min. reprogramming time for 47# clock event device 48config GENERIC_CLOCKEVENTS_MIN_ADJUST 49 bool 50 51# Generic update of CMOS clock 52config GENERIC_CMOS_UPDATE 53 bool 54 55if GENERIC_CLOCKEVENTS 56menu "Timers subsystem" 57 58# Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is 59# only related to the tick functionality. Oneshot clockevent devices 60# are supported independent of this. 61config TICK_ONESHOT 62 bool 63 64config NO_HZ_COMMON 65 bool 66 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 67 select TICK_ONESHOT 68 69choice 70 prompt "Timer tick handling" 71 default NO_HZ_IDLE if NO_HZ 72 73config HZ_PERIODIC 74 bool "Periodic timer ticks (constant rate, no dynticks)" 75 help 76 This option keeps the tick running periodically at a constant 77 rate, even when the CPU doesn't need it. 78 79config NO_HZ_IDLE 80 bool "Idle dynticks system (tickless idle)" 81 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 82 select NO_HZ_COMMON 83 help 84 This option enables a tickless idle system: timer interrupts 85 will only trigger on an as-needed basis when the system is idle. 86 This is usually interesting for energy saving. 87 88 Most of the time you want to say Y here. 89 90config NO_HZ_FULL 91 bool "Full dynticks system (tickless)" 92 # NO_HZ_COMMON dependency 93 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 94 # We need at least one periodic CPU for timekeeping 95 depends on SMP 96 depends on HAVE_CONTEXT_TRACKING 97 # VIRT_CPU_ACCOUNTING_GEN dependency 98 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 99 select NO_HZ_COMMON 100 select RCU_NOCB_CPU 101 select VIRT_CPU_ACCOUNTING_GEN 102 select IRQ_WORK 103 select CPU_ISOLATION 104 help 105 Adaptively try to shutdown the tick whenever possible, even when 106 the CPU is running tasks. Typically this requires running a single 107 task on the CPU. Chances for running tickless are maximized when 108 the task mostly runs in userspace and has few kernel activity. 109 110 You need to fill up the nohz_full boot parameter with the 111 desired range of dynticks CPUs. 112 113 This is implemented at the expense of some overhead in user <-> kernel 114 transitions: syscalls, exceptions and interrupts. Even when it's 115 dynamically off. 116 117 Say N. 118 119endchoice 120 121config CONTEXT_TRACKING 122 bool 123 124config CONTEXT_TRACKING_FORCE 125 bool "Force context tracking" 126 depends on CONTEXT_TRACKING 127 default y if !NO_HZ_FULL 128 help 129 The major pre-requirement for full dynticks to work is to 130 support the context tracking subsystem. But there are also 131 other dependencies to provide in order to make the full 132 dynticks working. 133 134 This option stands for testing when an arch implements the 135 context tracking backend but doesn't yet fullfill all the 136 requirements to make the full dynticks feature working. 137 Without the full dynticks, there is no way to test the support 138 for context tracking and the subsystems that rely on it: RCU 139 userspace extended quiescent state and tickless cputime 140 accounting. This option copes with the absence of the full 141 dynticks subsystem by forcing the context tracking on all 142 CPUs in the system. 143 144 Say Y only if you're working on the development of an 145 architecture backend for the context tracking. 146 147 Say N otherwise, this option brings an overhead that you 148 don't want in production. 149 150config NO_HZ 151 bool "Old Idle dynticks config" 152 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 153 help 154 This is the old config entry that enables dynticks idle. 155 We keep it around for a little while to enforce backward 156 compatibility with older config files. 157 158config HIGH_RES_TIMERS 159 bool "High Resolution Timer Support" 160 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 161 select TICK_ONESHOT 162 help 163 This option enables high resolution timer support. If your 164 hardware is not capable then this option only increases 165 the size of the kernel image. 166 167endmenu 168endif 169