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 55# Select to handle posix CPU timers from task_work 56# and not from the timer interrupt context 57config HAVE_POSIX_CPU_TIMERS_TASK_WORK 58 bool 59 60config POSIX_CPU_TIMERS_TASK_WORK 61 bool 62 default y if POSIX_TIMERS && HAVE_POSIX_CPU_TIMERS_TASK_WORK 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 independent 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 depends on HAVE_CONTEXT_TRACKING 106 # VIRT_CPU_ACCOUNTING_GEN dependency 107 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 108 select NO_HZ_COMMON 109 select RCU_NOCB_CPU 110 select VIRT_CPU_ACCOUNTING_GEN 111 select IRQ_WORK 112 select CPU_ISOLATION 113 help 114 Adaptively try to shutdown the tick whenever possible, even when 115 the CPU is running tasks. Typically this requires running a single 116 task on the CPU. Chances for running tickless are maximized when 117 the task mostly runs in userspace and has few kernel activity. 118 119 You need to fill up the nohz_full boot parameter with the 120 desired range of dynticks CPUs. 121 122 This is implemented at the expense of some overhead in user <-> kernel 123 transitions: syscalls, exceptions and interrupts. Even when it's 124 dynamically off. 125 126 Say N. 127 128endchoice 129 130config CONTEXT_TRACKING 131 bool 132 133config CONTEXT_TRACKING_FORCE 134 bool "Force context tracking" 135 depends on CONTEXT_TRACKING 136 default y if !NO_HZ_FULL 137 help 138 The major pre-requirement for full dynticks to work is to 139 support the context tracking subsystem. But there are also 140 other dependencies to provide in order to make the full 141 dynticks working. 142 143 This option stands for testing when an arch implements the 144 context tracking backend but doesn't yet fullfill all the 145 requirements to make the full dynticks feature working. 146 Without the full dynticks, there is no way to test the support 147 for context tracking and the subsystems that rely on it: RCU 148 userspace extended quiescent state and tickless cputime 149 accounting. This option copes with the absence of the full 150 dynticks subsystem by forcing the context tracking on all 151 CPUs in the system. 152 153 Say Y only if you're working on the development of an 154 architecture backend for the context tracking. 155 156 Say N otherwise, this option brings an overhead that you 157 don't want in production. 158 159config NO_HZ 160 bool "Old Idle dynticks config" 161 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 162 help 163 This is the old config entry that enables dynticks idle. 164 We keep it around for a little while to enforce backward 165 compatibility with older config files. 166 167config HIGH_RES_TIMERS 168 bool "High Resolution Timer Support" 169 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS 170 select TICK_ONESHOT 171 help 172 This option enables high resolution timer support. If your 173 hardware is not capable then this option only increases 174 the size of the kernel image. 175 176endmenu 177endif 178