2 # Timer subsystem related configuration options
5 # Options selectable by arch Kconfig
7 # Watchdog function for clocksources to detect instabilities
8 config CLOCKSOURCE_WATCHDOG
11 # Architecture has extra clocksource data
12 config ARCH_CLOCKSOURCE_DATA
15 # Timekeeping vsyscall support
16 config GENERIC_TIME_VSYSCALL
19 # Timekeeping vsyscall support
20 config GENERIC_TIME_VSYSCALL_OLD
23 # ktime_t scalar 64bit nsec representation
27 # Old style timekeeping
28 config ARCH_USES_GETTIMEOFFSET
31 # The generic clock events infrastructure
32 config GENERIC_CLOCKEVENTS
35 # Migration helper. Builds, but does not invoke
36 config GENERIC_CLOCKEVENTS_BUILD
39 depends on GENERIC_CLOCKEVENTS
41 # Architecture can handle broadcast in a driver-agnostic way
42 config ARCH_HAS_TICK_BROADCAST
45 # Clockevents broadcasting infrastructure
46 config GENERIC_CLOCKEVENTS_BROADCAST
48 depends on GENERIC_CLOCKEVENTS
50 # Automatically adjust the min. reprogramming time for
52 config GENERIC_CLOCKEVENTS_MIN_ADJUST
55 # Generic update of CMOS clock
56 config GENERIC_CMOS_UPDATE
59 if GENERIC_CLOCKEVENTS
60 menu "Timers subsystem"
62 # Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is
63 # only related to the tick functionality. Oneshot clockevent devices
64 # are supported independ of this.
70 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
74 prompt "Timer tick handling"
75 default NO_HZ_IDLE if NO_HZ
78 bool "Periodic timer ticks (constant rate, no dynticks)"
80 This option keeps the tick running periodically at a constant
81 rate, even when the CPU doesn't need it.
84 bool "Idle dynticks system (tickless idle)"
85 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
88 This option enables a tickless idle system: timer interrupts
89 will only trigger on an as-needed basis when the system is idle.
90 This is usually interesting for energy saving.
92 Most of the time you want to say Y here.
95 bool "Full dynticks system (tickless)"
96 # NO_HZ_COMMON dependency
97 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
98 # We need at least one periodic CPU for timekeeping
100 # RCU_USER_QS dependency
101 depends on HAVE_CONTEXT_TRACKING
102 # VIRT_CPU_ACCOUNTING_GEN dependency
107 select VIRT_CPU_ACCOUNTING_GEN
108 select CONTEXT_TRACKING_FORCE
111 Adaptively try to shutdown the tick whenever possible, even when
112 the CPU is running tasks. Typically this requires running a single
113 task on the CPU. Chances for running tickless are maximized when
114 the task mostly runs in userspace and has few kernel activity.
116 You need to fill up the nohz_full boot parameter with the
117 desired range of dynticks CPUs.
119 This is implemented at the expense of some overhead in user <-> kernel
120 transitions: syscalls, exceptions and interrupts. Even when it's
127 config NO_HZ_FULL_ALL
128 bool "Full dynticks system on all CPUs by default"
129 depends on NO_HZ_FULL
131 If the user doesn't pass the nohz_full boot option to
132 define the range of full dynticks CPUs, consider that all
133 CPUs in the system are full dynticks by default.
134 Note the boot CPU will still be kept outside the range to
135 handle the timekeeping duty.
138 bool "Old Idle dynticks config"
139 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
141 This is the old config entry that enables dynticks idle.
142 We keep it around for a little while to enforce backward
143 compatibility with older config files.
145 config HIGH_RES_TIMERS
146 bool "High Resolution Timer Support"
147 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
150 This option enables high resolution timer support. If your
151 hardware is not capable then this option only increases
152 the size of the kernel image.