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 # Platforms has a persistent clock
16 config ALWAYS_USE_PERSISTENT_CLOCK
20 # Timekeeping vsyscall support
21 config GENERIC_TIME_VSYSCALL
24 # Timekeeping vsyscall support
25 config GENERIC_TIME_VSYSCALL_OLD
28 # ktime_t scalar 64bit nsec representation
32 # Old style timekeeping
33 config ARCH_USES_GETTIMEOFFSET
36 # The generic clock events infrastructure
37 config GENERIC_CLOCKEVENTS
40 # Migration helper. Builds, but does not invoke
41 config GENERIC_CLOCKEVENTS_BUILD
44 depends on GENERIC_CLOCKEVENTS
46 # Architecture can handle broadcast in a driver-agnostic way
47 config ARCH_HAS_TICK_BROADCAST
50 # Clockevents broadcasting infrastructure
51 config GENERIC_CLOCKEVENTS_BROADCAST
53 depends on GENERIC_CLOCKEVENTS
55 # Automatically adjust the min. reprogramming time for
57 config GENERIC_CLOCKEVENTS_MIN_ADJUST
60 # Generic update of CMOS clock
61 config GENERIC_CMOS_UPDATE
64 if GENERIC_CLOCKEVENTS
65 menu "Timers subsystem"
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 independ of this.
75 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
79 prompt "Timer tick handling"
80 default NO_HZ_IDLE if NO_HZ
83 bool "Periodic timer ticks (constant rate, no dynticks)"
85 This option keeps the tick running periodically at a constant
86 rate, even when the CPU doesn't need it.
89 bool "Idle dynticks system (tickless idle)"
90 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
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.
97 Most of the time you want to say Y here.
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
105 # RCU_USER_QS dependency
106 depends on HAVE_CONTEXT_TRACKING
107 # VIRT_CPU_ACCOUNTING_GEN dependency
112 select VIRT_CPU_ACCOUNTING_GEN
113 select CONTEXT_TRACKING_FORCE
116 Adaptively try to shutdown the tick whenever possible, even when
117 the CPU is running tasks. Typically this requires running a single
118 task on the CPU. Chances for running tickless are maximized when
119 the task mostly runs in userspace and has few kernel activity.
121 You need to fill up the nohz_full boot parameter with the
122 desired range of dynticks CPUs.
124 This is implemented at the expense of some overhead in user <-> kernel
125 transitions: syscalls, exceptions and interrupts. Even when it's
132 config NO_HZ_FULL_ALL
133 bool "Full dynticks system on all CPUs by default"
134 depends on NO_HZ_FULL
136 If the user doesn't pass the nohz_full boot option to
137 define the range of full dynticks CPUs, consider that all
138 CPUs in the system are full dynticks by default.
139 Note the boot CPU will still be kept outside the range to
140 handle the timekeeping duty.
143 bool "Old Idle dynticks config"
144 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
146 This is the old config entry that enables dynticks idle.
147 We keep it around for a little while to enforce backward
148 compatibility with older config files.
150 config HIGH_RES_TIMERS
151 bool "High Resolution Timer Support"
152 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
155 This option enables high resolution timer support. If your
156 hardware is not capable then this option only increases
157 the size of the kernel image.