1 # SPDX-License-Identifier: GPL-2.0-only
3 # Timer subsystem related configuration options
6 # Options selectable by arch Kconfig
8 # Watchdog function for clocksources to detect instabilities
9 config CLOCKSOURCE_WATCHDOG
12 # Architecture has extra clocksource data
13 config ARCH_CLOCKSOURCE_DATA
16 # Architecture has extra clocksource init called from registration
17 config ARCH_CLOCKSOURCE_INIT
20 # Clocksources require validation of the clocksource against the last
21 # cycle update - x86/TSC misfeature
22 config CLOCKSOURCE_VALIDATE_LAST_CYCLE
25 # Timekeeping vsyscall support
26 config GENERIC_TIME_VSYSCALL
29 # The generic clock events infrastructure
30 config GENERIC_CLOCKEVENTS
33 # Architecture can handle broadcast in a driver-agnostic way
34 config ARCH_HAS_TICK_BROADCAST
37 # Clockevents broadcasting infrastructure
38 config GENERIC_CLOCKEVENTS_BROADCAST
40 depends on GENERIC_CLOCKEVENTS
42 # Automatically adjust the min. reprogramming time for
44 config GENERIC_CLOCKEVENTS_MIN_ADJUST
47 # Generic update of CMOS clock
48 config GENERIC_CMOS_UPDATE
51 # Select to handle posix CPU timers from task_work
52 # and not from the timer interrupt context
53 config HAVE_POSIX_CPU_TIMERS_TASK_WORK
56 config POSIX_CPU_TIMERS_TASK_WORK
58 default y if POSIX_TIMERS && HAVE_POSIX_CPU_TIMERS_TASK_WORK
60 if GENERIC_CLOCKEVENTS
61 menu "Timers subsystem"
63 # Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is
64 # only related to the tick functionality. Oneshot clockevent devices
65 # are supported independent of this.
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)"
87 This option enables a tickless idle system: timer interrupts
88 will only trigger on an as-needed basis when the system is idle.
89 This is usually interesting for energy saving.
91 Most of the time you want to say Y here.
94 bool "Full dynticks system (tickless)"
95 # NO_HZ_COMMON dependency
96 # We need at least one periodic CPU for timekeeping
98 depends on HAVE_CONTEXT_TRACKING
99 # VIRT_CPU_ACCOUNTING_GEN dependency
100 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
103 select VIRT_CPU_ACCOUNTING_GEN
107 Adaptively try to shutdown the tick whenever possible, even when
108 the CPU is running tasks. Typically this requires running a single
109 task on the CPU. Chances for running tickless are maximized when
110 the task mostly runs in userspace and has few kernel activity.
112 You need to fill up the nohz_full boot parameter with the
113 desired range of dynticks CPUs.
115 This is implemented at the expense of some overhead in user <-> kernel
116 transitions: syscalls, exceptions and interrupts. Even when it's
123 config CONTEXT_TRACKING
126 config CONTEXT_TRACKING_FORCE
127 bool "Force context tracking"
128 depends on CONTEXT_TRACKING
129 default y if !NO_HZ_FULL
131 The major pre-requirement for full dynticks to work is to
132 support the context tracking subsystem. But there are also
133 other dependencies to provide in order to make the full
136 This option stands for testing when an arch implements the
137 context tracking backend but doesn't yet fullfill all the
138 requirements to make the full dynticks feature working.
139 Without the full dynticks, there is no way to test the support
140 for context tracking and the subsystems that rely on it: RCU
141 userspace extended quiescent state and tickless cputime
142 accounting. This option copes with the absence of the full
143 dynticks subsystem by forcing the context tracking on all
146 Say Y only if you're working on the development of an
147 architecture backend for the context tracking.
149 Say N otherwise, this option brings an overhead that you
150 don't want in production.
153 bool "Old Idle dynticks config"
155 This is the old config entry that enables dynticks idle.
156 We keep it around for a little while to enforce backward
157 compatibility with older config files.
159 config HIGH_RES_TIMERS
160 bool "High Resolution Timer Support"
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.