1 # SPDX-License-Identifier: GPL-2.0-only 1 # SPDX-License-Identifier: GPL-2.0-only
2 # 2 #
3 # Timer subsystem related configuration option 3 # Timer subsystem related configuration options
4 # 4 #
5 5
6 # Options selectable by arch Kconfig 6 # Options selectable by arch Kconfig
7 7
8 # Watchdog function for clocksources to detect 8 # Watchdog function for clocksources to detect instabilities
9 config CLOCKSOURCE_WATCHDOG 9 config CLOCKSOURCE_WATCHDOG
10 bool 10 bool
11 11
12 # Architecture has extra clocksource data 12 # Architecture has extra clocksource data
13 config ARCH_CLOCKSOURCE_DATA 13 config ARCH_CLOCKSOURCE_DATA
14 bool 14 bool
15 15
16 # Architecture has extra clocksource init call 16 # Architecture has extra clocksource init called from registration
17 config ARCH_CLOCKSOURCE_INIT 17 config ARCH_CLOCKSOURCE_INIT
18 bool 18 bool
19 19
20 # Clocksources require validation of the clock 20 # Clocksources require validation of the clocksource against the last
21 # cycle update - x86/TSC misfeature 21 # cycle update - x86/TSC misfeature
22 config CLOCKSOURCE_VALIDATE_LAST_CYCLE 22 config CLOCKSOURCE_VALIDATE_LAST_CYCLE
23 bool 23 bool
24 24
25 # Timekeeping vsyscall support 25 # Timekeeping vsyscall support
26 config GENERIC_TIME_VSYSCALL 26 config GENERIC_TIME_VSYSCALL
27 bool 27 bool
28 28
29 # The generic clock events infrastructure 29 # The generic clock events infrastructure
30 config GENERIC_CLOCKEVENTS 30 config GENERIC_CLOCKEVENTS
31 def_bool !LEGACY_TIMER_TICK 31 def_bool !LEGACY_TIMER_TICK
32 32
33 # Architecture can handle broadcast in a drive 33 # Architecture can handle broadcast in a driver-agnostic way
34 config ARCH_HAS_TICK_BROADCAST 34 config ARCH_HAS_TICK_BROADCAST
35 bool 35 bool
36 36
37 # Clockevents broadcasting infrastructure 37 # Clockevents broadcasting infrastructure
38 config GENERIC_CLOCKEVENTS_BROADCAST 38 config GENERIC_CLOCKEVENTS_BROADCAST
39 bool 39 bool
40 depends on GENERIC_CLOCKEVENTS 40 depends on GENERIC_CLOCKEVENTS
41 41
42 # Handle broadcast in default_idle_call() 42 # Handle broadcast in default_idle_call()
43 config GENERIC_CLOCKEVENTS_BROADCAST_IDLE 43 config GENERIC_CLOCKEVENTS_BROADCAST_IDLE
44 bool 44 bool
45 depends on GENERIC_CLOCKEVENTS_BROADCA 45 depends on GENERIC_CLOCKEVENTS_BROADCAST
46 46
47 # Automatically adjust the min. reprogramming 47 # Automatically adjust the min. reprogramming time for
48 # clock event device 48 # clock event device
49 config GENERIC_CLOCKEVENTS_MIN_ADJUST 49 config GENERIC_CLOCKEVENTS_MIN_ADJUST
50 bool 50 bool
51 51
52 # Generic update of CMOS clock 52 # Generic update of CMOS clock
53 config GENERIC_CMOS_UPDATE 53 config GENERIC_CMOS_UPDATE
54 bool 54 bool
55 55
56 # Select to handle posix CPU timers from task_ 56 # Select to handle posix CPU timers from task_work
57 # and not from the timer interrupt context 57 # and not from the timer interrupt context
58 config HAVE_POSIX_CPU_TIMERS_TASK_WORK 58 config HAVE_POSIX_CPU_TIMERS_TASK_WORK
59 bool 59 bool
60 60
61 config POSIX_CPU_TIMERS_TASK_WORK 61 config POSIX_CPU_TIMERS_TASK_WORK
62 bool 62 bool
63 default y if POSIX_TIMERS && HAVE_POSI 63 default y if POSIX_TIMERS && HAVE_POSIX_CPU_TIMERS_TASK_WORK
64 64
65 config LEGACY_TIMER_TICK 65 config LEGACY_TIMER_TICK
66 bool 66 bool
67 help 67 help
68 The legacy timer tick helper is used 68 The legacy timer tick helper is used by platforms that
69 lack support for the generic clockev 69 lack support for the generic clockevent framework.
70 New platforms should use generic clo 70 New platforms should use generic clockevents instead.
71 71
72 config TIME_KUNIT_TEST 72 config TIME_KUNIT_TEST
73 tristate "KUnit test for kernel/time f 73 tristate "KUnit test for kernel/time functions" if !KUNIT_ALL_TESTS
74 depends on KUNIT 74 depends on KUNIT
75 default KUNIT_ALL_TESTS 75 default KUNIT_ALL_TESTS
76 help 76 help
77 Enable this option to test RTC libra 77 Enable this option to test RTC library functions.
78 78
79 If unsure, say N. 79 If unsure, say N.
80 80
81 config CONTEXT_TRACKING 81 config CONTEXT_TRACKING
82 bool 82 bool
83 83
84 config CONTEXT_TRACKING_IDLE 84 config CONTEXT_TRACKING_IDLE
85 bool 85 bool
86 select CONTEXT_TRACKING 86 select CONTEXT_TRACKING
87 help 87 help
88 Tracks idle state on behalf of RCU. 88 Tracks idle state on behalf of RCU.
89 89
90 if GENERIC_CLOCKEVENTS 90 if GENERIC_CLOCKEVENTS
91 menu "Timers subsystem" 91 menu "Timers subsystem"
92 92
93 # Core internal switch. Selected by NO_HZ_COMM 93 # Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is
94 # only related to the tick functionality. Ones 94 # only related to the tick functionality. Oneshot clockevent devices
95 # are supported independent of this. 95 # are supported independent of this.
96 config TICK_ONESHOT 96 config TICK_ONESHOT
97 bool 97 bool
98 98
99 config NO_HZ_COMMON 99 config NO_HZ_COMMON
100 bool 100 bool
101 select TICK_ONESHOT 101 select TICK_ONESHOT
102 102
103 choice 103 choice
104 prompt "Timer tick handling" 104 prompt "Timer tick handling"
105 default NO_HZ_IDLE if NO_HZ 105 default NO_HZ_IDLE if NO_HZ
106 106
107 config HZ_PERIODIC 107 config HZ_PERIODIC
108 bool "Periodic timer ticks (constant r 108 bool "Periodic timer ticks (constant rate, no dynticks)"
109 help 109 help
110 This option keeps the tick running p 110 This option keeps the tick running periodically at a constant
111 rate, even when the CPU doesn't need 111 rate, even when the CPU doesn't need it.
112 112
113 config NO_HZ_IDLE 113 config NO_HZ_IDLE
114 bool "Idle dynticks system (tickless i 114 bool "Idle dynticks system (tickless idle)"
115 select NO_HZ_COMMON 115 select NO_HZ_COMMON
116 help 116 help
117 This option enables a tickless idle 117 This option enables a tickless idle system: timer interrupts
118 will only trigger on an as-needed ba 118 will only trigger on an as-needed basis when the system is idle.
119 This is usually interesting for ener 119 This is usually interesting for energy saving.
120 120
121 Most of the time you want to say Y h 121 Most of the time you want to say Y here.
122 122
123 config NO_HZ_FULL 123 config NO_HZ_FULL
124 bool "Full dynticks system (tickless)" 124 bool "Full dynticks system (tickless)"
125 # NO_HZ_COMMON dependency 125 # NO_HZ_COMMON dependency
126 # We need at least one periodic CPU fo 126 # We need at least one periodic CPU for timekeeping
127 depends on SMP 127 depends on SMP
128 depends on HAVE_CONTEXT_TRACKING_USER 128 depends on HAVE_CONTEXT_TRACKING_USER
129 # VIRT_CPU_ACCOUNTING_GEN dependency 129 # VIRT_CPU_ACCOUNTING_GEN dependency
130 depends on HAVE_VIRT_CPU_ACCOUNTING_GE 130 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
131 select NO_HZ_COMMON 131 select NO_HZ_COMMON
132 select RCU_NOCB_CPU 132 select RCU_NOCB_CPU
133 select VIRT_CPU_ACCOUNTING_GEN 133 select VIRT_CPU_ACCOUNTING_GEN
134 select IRQ_WORK 134 select IRQ_WORK
135 select CPU_ISOLATION 135 select CPU_ISOLATION
136 help 136 help
137 Adaptively try to shutdown the tick w 137 Adaptively try to shutdown the tick whenever possible, even when
138 the CPU is running tasks. Typically t 138 the CPU is running tasks. Typically this requires running a single
139 task on the CPU. Chances for running 139 task on the CPU. Chances for running tickless are maximized when
140 the task mostly runs in userspace and 140 the task mostly runs in userspace and has few kernel activity.
141 141
142 You need to fill up the nohz_full boo 142 You need to fill up the nohz_full boot parameter with the
143 desired range of dynticks CPUs to use 143 desired range of dynticks CPUs to use it. This is implemented at
144 the expense of some overhead in user 144 the expense of some overhead in user <-> kernel transitions:
145 syscalls, exceptions and interrupts. 145 syscalls, exceptions and interrupts.
146 146
147 By default, without passing the nohz_ 147 By default, without passing the nohz_full parameter, this behaves just
148 like NO_HZ_IDLE. 148 like NO_HZ_IDLE.
149 149
150 If you're a distro say Y. 150 If you're a distro say Y.
151 151
152 endchoice 152 endchoice
153 153
154 config CONTEXT_TRACKING_USER 154 config CONTEXT_TRACKING_USER
155 bool 155 bool
156 depends on HAVE_CONTEXT_TRACKING_USER 156 depends on HAVE_CONTEXT_TRACKING_USER
157 select CONTEXT_TRACKING 157 select CONTEXT_TRACKING
158 help 158 help
159 Track transitions between kernel and 159 Track transitions between kernel and user on behalf of RCU and
160 tickless cputime accounting. The for 160 tickless cputime accounting. The former case relies on context
161 tracking to enter/exit RCU extended 161 tracking to enter/exit RCU extended quiescent states.
162 162
163 config CONTEXT_TRACKING_USER_FORCE 163 config CONTEXT_TRACKING_USER_FORCE
164 bool "Force user context tracking" 164 bool "Force user context tracking"
165 depends on CONTEXT_TRACKING_USER 165 depends on CONTEXT_TRACKING_USER
166 default y if !NO_HZ_FULL 166 default y if !NO_HZ_FULL
167 help 167 help
168 The major pre-requirement for full d 168 The major pre-requirement for full dynticks to work is to
169 support the user context tracking su 169 support the user context tracking subsystem. But there are also
170 other dependencies to provide in ord 170 other dependencies to provide in order to make the full
171 dynticks working. 171 dynticks working.
172 172
173 This option stands for testing when 173 This option stands for testing when an arch implements the
174 user context tracking backend but do 174 user context tracking backend but doesn't yet fulfill all the
175 requirements to make the full dyntic 175 requirements to make the full dynticks feature working.
176 Without the full dynticks, there is 176 Without the full dynticks, there is no way to test the support
177 for user context tracking and the su 177 for user context tracking and the subsystems that rely on it: RCU
178 userspace extended quiescent state a 178 userspace extended quiescent state and tickless cputime
179 accounting. This option copes with t 179 accounting. This option copes with the absence of the full
180 dynticks subsystem by forcing the us 180 dynticks subsystem by forcing the user context tracking on all
181 CPUs in the system. 181 CPUs in the system.
182 182
183 Say Y only if you're working on the 183 Say Y only if you're working on the development of an
184 architecture backend for the user co 184 architecture backend for the user context tracking.
185 185
186 Say N otherwise, this option brings 186 Say N otherwise, this option brings an overhead that you
187 don't want in production. 187 don't want in production.
188 188
189 config NO_HZ 189 config NO_HZ
190 bool "Old Idle dynticks config" 190 bool "Old Idle dynticks config"
191 help 191 help
192 This is the old config entry that en 192 This is the old config entry that enables dynticks idle.
193 We keep it around for a little while 193 We keep it around for a little while to enforce backward
194 compatibility with older config file 194 compatibility with older config files.
195 195
196 config HIGH_RES_TIMERS 196 config HIGH_RES_TIMERS
197 bool "High Resolution Timer Support" 197 bool "High Resolution Timer Support"
198 select TICK_ONESHOT 198 select TICK_ONESHOT
199 help 199 help
200 This option enables high resolution 200 This option enables high resolution timer support. If your
201 hardware is not capable then this op 201 hardware is not capable then this option only increases
202 the size of the kernel image. 202 the size of the kernel image.
203 203
204 config CLOCKSOURCE_WATCHDOG_MAX_SKEW_US 204 config CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
205 int "Clocksource watchdog maximum allo 205 int "Clocksource watchdog maximum allowable skew (in microseconds)"
206 depends on CLOCKSOURCE_WATCHDOG 206 depends on CLOCKSOURCE_WATCHDOG
207 range 50 1000 207 range 50 1000
208 default 125 208 default 125
209 help 209 help
210 Specify the maximum amount of allowa 210 Specify the maximum amount of allowable watchdog skew in
211 microseconds before reporting the cl 211 microseconds before reporting the clocksource to be unstable.
212 The default is based on a half-secon 212 The default is based on a half-second clocksource watchdog
213 interval and NTP's maximum frequency 213 interval and NTP's maximum frequency drift of 500 parts
214 per million. If the clocksource is 214 per million. If the clocksource is good enough for NTP,
215 it is good enough for the clocksourc 215 it is good enough for the clocksource watchdog!
216 216
217 endmenu 217 endmenu
218 endif 218 endif
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