projects/linux·blob v5.13 · refs

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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# The generic clock events infrastructure
30config GENERIC_CLOCKEVENTS
31 def_bool !LEGACY_TIMER_TICK
32
33# Architecture can handle broadcast in a driver-agnostic way
34config ARCH_HAS_TICK_BROADCAST
35 bool
36
37# Clockevents broadcasting infrastructure
38config GENERIC_CLOCKEVENTS_BROADCAST
39 bool
40 depends on GENERIC_CLOCKEVENTS
41
42# Automatically adjust the min. reprogramming time for
43# clock event device
44config GENERIC_CLOCKEVENTS_MIN_ADJUST
45 bool
46
47# Generic update of CMOS clock
48config GENERIC_CMOS_UPDATE
49 bool
50
51# Select to handle posix CPU timers from task_work
52# and not from the timer interrupt context
53config HAVE_POSIX_CPU_TIMERS_TASK_WORK
54 bool
55
56config POSIX_CPU_TIMERS_TASK_WORK
57 bool
58 default y if POSIX_TIMERS && HAVE_POSIX_CPU_TIMERS_TASK_WORK
59
60config LEGACY_TIMER_TICK
61 bool
62 help
63 The legacy timer tick helper is used by platforms that
64 lack support for the generic clockevent framework.
65 New platforms should use generic clockevents instead.
66
67if GENERIC_CLOCKEVENTS
68menu "Timers subsystem"
69
70# Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is
71# only related to the tick functionality. Oneshot clockevent devices
72# are supported independent of this.
73config TICK_ONESHOT
74 bool
75
76config NO_HZ_COMMON
77 bool
78 select TICK_ONESHOT
79
80choice
81 prompt "Timer tick handling"
82 default NO_HZ_IDLE if NO_HZ
83
84config HZ_PERIODIC
85 bool "Periodic timer ticks (constant rate, no dynticks)"
86 help
87 This option keeps the tick running periodically at a constant
88 rate, even when the CPU doesn't need it.
89
90config NO_HZ_IDLE
91 bool "Idle dynticks system (tickless idle)"
92 select NO_HZ_COMMON
93 help
94 This option enables a tickless idle system: timer interrupts
95 will only trigger on an as-needed basis when the system is idle.
96 This is usually interesting for energy saving.
97
98 Most of the time you want to say Y here.
99
100config NO_HZ_FULL
101 bool "Full dynticks system (tickless)"
102 # NO_HZ_COMMON dependency
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 fulfill 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 help
162 This is the old config entry that enables dynticks idle.
163 We keep it around for a little while to enforce backward
164 compatibility with older config files.
165
166config HIGH_RES_TIMERS
167 bool "High Resolution Timer Support"
168 select TICK_ONESHOT
169 help
170 This option enables high resolution timer support. If your
171 hardware is not capable then this option only increases
172 the size of the kernel image.
173
174endmenu
175endif