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