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# Clocksources require validation of the clocksource against the last 16# cycle update - x86/TSC misfeature 17config CLOCKSOURCE_VALIDATE_LAST_CYCLE 18 bool 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# 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 independ 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 help 103 Adaptively try to shutdown the tick whenever possible, even when 104 the CPU is running tasks. Typically this requires running a single 105 task on the CPU. Chances for running tickless are maximized when 106 the task mostly runs in userspace and has few kernel activity. 107 108 You need to fill up the nohz_full boot parameter with the 109 desired range of dynticks CPUs. 110 111 This is implemented at the expense of some overhead in user <-> kernel 112 transitions: syscalls, exceptions and interrupts. Even when it's 113 dynamically off. 114 115 Say N. 116 117endchoice 118 119config NO_HZ_FULL_ALL 120 bool "Full dynticks system on all CPUs by default (except CPU 0)" 121 depends on NO_HZ_FULL 122 help 123 If the user doesn't pass the nohz_full boot option to 124 define the range of full dynticks CPUs, consider that all 125 CPUs in the system are full dynticks by default. 126 Note the boot CPU will still be kept outside the range to 127 handle the timekeeping duty. 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