1 # SPDX-License-Identifier: GPL-2.0-only <<
2 # 1 #
3 # Timer subsystem related configuration option 2 # Timer subsystem related configuration options
4 # 3 #
5 4
6 # Options selectable by arch Kconfig 5 # Options selectable by arch Kconfig
7 6
8 # Watchdog function for clocksources to detect 7 # Watchdog function for clocksources to detect instabilities
9 config CLOCKSOURCE_WATCHDOG 8 config CLOCKSOURCE_WATCHDOG
10 bool 9 bool
11 10
12 # Architecture has extra clocksource data 11 # Architecture has extra clocksource data
13 config ARCH_CLOCKSOURCE_DATA 12 config ARCH_CLOCKSOURCE_DATA
14 bool 13 bool
15 14
16 # Architecture has extra clocksource init call <<
17 config ARCH_CLOCKSOURCE_INIT <<
18 bool <<
19 <<
20 # Clocksources require validation of the clock 15 # Clocksources require validation of the clocksource against the last
21 # cycle update - x86/TSC misfeature 16 # cycle update - x86/TSC misfeature
22 config CLOCKSOURCE_VALIDATE_LAST_CYCLE 17 config CLOCKSOURCE_VALIDATE_LAST_CYCLE
23 bool 18 bool
24 19
25 # Timekeeping vsyscall support 20 # Timekeeping vsyscall support
26 config GENERIC_TIME_VSYSCALL 21 config GENERIC_TIME_VSYSCALL
27 bool 22 bool
28 23
>> 24 # Old style timekeeping
>> 25 config ARCH_USES_GETTIMEOFFSET
>> 26 bool
>> 27
29 # The generic clock events infrastructure 28 # The generic clock events infrastructure
30 config GENERIC_CLOCKEVENTS 29 config GENERIC_CLOCKEVENTS
31 def_bool !LEGACY_TIMER_TICK !! 30 bool
32 31
33 # Architecture can handle broadcast in a drive 32 # Architecture can handle broadcast in a driver-agnostic way
34 config ARCH_HAS_TICK_BROADCAST 33 config ARCH_HAS_TICK_BROADCAST
35 bool 34 bool
36 35
37 # Clockevents broadcasting infrastructure 36 # Clockevents broadcasting infrastructure
38 config GENERIC_CLOCKEVENTS_BROADCAST 37 config GENERIC_CLOCKEVENTS_BROADCAST
39 bool 38 bool
40 depends on GENERIC_CLOCKEVENTS 39 depends on GENERIC_CLOCKEVENTS
41 40
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 41 # Automatically adjust the min. reprogramming time for
48 # clock event device 42 # clock event device
49 config GENERIC_CLOCKEVENTS_MIN_ADJUST 43 config GENERIC_CLOCKEVENTS_MIN_ADJUST
50 bool 44 bool
51 45
52 # Generic update of CMOS clock 46 # Generic update of CMOS clock
53 config GENERIC_CMOS_UPDATE 47 config GENERIC_CMOS_UPDATE
54 bool 48 bool
55 49
56 # Select to handle posix CPU timers from task_ <<
57 # and not from the timer interrupt context <<
58 config HAVE_POSIX_CPU_TIMERS_TASK_WORK <<
59 bool <<
60 <<
61 config POSIX_CPU_TIMERS_TASK_WORK <<
62 bool <<
63 default y if POSIX_TIMERS && HAVE_POSI <<
64 <<
65 config LEGACY_TIMER_TICK <<
66 bool <<
67 help <<
68 The legacy timer tick helper is used <<
69 lack support for the generic clockev <<
70 New platforms should use generic clo <<
71 <<
72 config TIME_KUNIT_TEST <<
73 tristate "KUnit test for kernel/time f <<
74 depends on KUNIT <<
75 default KUNIT_ALL_TESTS <<
76 help <<
77 Enable this option to test RTC libra <<
78 <<
79 If unsure, say N. <<
80 <<
81 config CONTEXT_TRACKING <<
82 bool <<
83 <<
84 config CONTEXT_TRACKING_IDLE <<
85 bool <<
86 select CONTEXT_TRACKING <<
87 help <<
88 Tracks idle state on behalf of RCU. <<
89 <<
90 if GENERIC_CLOCKEVENTS 50 if GENERIC_CLOCKEVENTS
91 menu "Timers subsystem" 51 menu "Timers subsystem"
92 52
93 # Core internal switch. Selected by NO_HZ_COMM 53 # Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is
94 # only related to the tick functionality. Ones 54 # only related to the tick functionality. Oneshot clockevent devices
95 # are supported independent of this. 55 # are supported independent of this.
96 config TICK_ONESHOT 56 config TICK_ONESHOT
97 bool 57 bool
98 58
99 config NO_HZ_COMMON 59 config NO_HZ_COMMON
100 bool 60 bool
>> 61 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
101 select TICK_ONESHOT 62 select TICK_ONESHOT
102 63
103 choice 64 choice
104 prompt "Timer tick handling" 65 prompt "Timer tick handling"
105 default NO_HZ_IDLE if NO_HZ 66 default NO_HZ_IDLE if NO_HZ
106 67
107 config HZ_PERIODIC 68 config HZ_PERIODIC
108 bool "Periodic timer ticks (constant r 69 bool "Periodic timer ticks (constant rate, no dynticks)"
109 help 70 help
110 This option keeps the tick running p 71 This option keeps the tick running periodically at a constant
111 rate, even when the CPU doesn't need 72 rate, even when the CPU doesn't need it.
112 73
113 config NO_HZ_IDLE 74 config NO_HZ_IDLE
114 bool "Idle dynticks system (tickless i 75 bool "Idle dynticks system (tickless idle)"
>> 76 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
115 select NO_HZ_COMMON 77 select NO_HZ_COMMON
116 help 78 help
117 This option enables a tickless idle 79 This option enables a tickless idle system: timer interrupts
118 will only trigger on an as-needed ba 80 will only trigger on an as-needed basis when the system is idle.
119 This is usually interesting for ener 81 This is usually interesting for energy saving.
120 82
121 Most of the time you want to say Y h 83 Most of the time you want to say Y here.
122 84
123 config NO_HZ_FULL 85 config NO_HZ_FULL
124 bool "Full dynticks system (tickless)" 86 bool "Full dynticks system (tickless)"
125 # NO_HZ_COMMON dependency 87 # NO_HZ_COMMON dependency
>> 88 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
126 # We need at least one periodic CPU fo 89 # We need at least one periodic CPU for timekeeping
127 depends on SMP 90 depends on SMP
128 depends on HAVE_CONTEXT_TRACKING_USER !! 91 depends on HAVE_CONTEXT_TRACKING
129 # VIRT_CPU_ACCOUNTING_GEN dependency 92 # VIRT_CPU_ACCOUNTING_GEN dependency
130 depends on HAVE_VIRT_CPU_ACCOUNTING_GE 93 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
131 select NO_HZ_COMMON 94 select NO_HZ_COMMON
132 select RCU_NOCB_CPU 95 select RCU_NOCB_CPU
133 select VIRT_CPU_ACCOUNTING_GEN 96 select VIRT_CPU_ACCOUNTING_GEN
134 select IRQ_WORK 97 select IRQ_WORK
135 select CPU_ISOLATION 98 select CPU_ISOLATION
136 help 99 help
137 Adaptively try to shutdown the tick w 100 Adaptively try to shutdown the tick whenever possible, even when
138 the CPU is running tasks. Typically t 101 the CPU is running tasks. Typically this requires running a single
139 task on the CPU. Chances for running 102 task on the CPU. Chances for running tickless are maximized when
140 the task mostly runs in userspace and 103 the task mostly runs in userspace and has few kernel activity.
141 104
142 You need to fill up the nohz_full boo 105 You need to fill up the nohz_full boot parameter with the
143 desired range of dynticks CPUs to use !! 106 desired range of dynticks CPUs.
144 the expense of some overhead in user <<
145 syscalls, exceptions and interrupts. <<
146 107
147 By default, without passing the nohz_ !! 108 This is implemented at the expense of some overhead in user <-> kernel
148 like NO_HZ_IDLE. !! 109 transitions: syscalls, exceptions and interrupts. Even when it's
>> 110 dynamically off.
149 111
150 If you're a distro say Y. !! 112 Say N.
151 113
152 endchoice 114 endchoice
153 115
154 config CONTEXT_TRACKING_USER !! 116 config NO_HZ_FULL_ALL
155 bool !! 117 bool "Full dynticks system on all CPUs by default (except CPU 0)"
156 depends on HAVE_CONTEXT_TRACKING_USER !! 118 depends on NO_HZ_FULL
157 select CONTEXT_TRACKING !! 119 help
158 help !! 120 If the user doesn't pass the nohz_full boot option to
159 Track transitions between kernel and !! 121 define the range of full dynticks CPUs, consider that all
160 tickless cputime accounting. The for !! 122 CPUs in the system are full dynticks by default.
161 tracking to enter/exit RCU extended !! 123 Note the boot CPU will still be kept outside the range to
162 !! 124 handle the timekeeping duty.
163 config CONTEXT_TRACKING_USER_FORCE <<
164 bool "Force user context tracking" <<
165 depends on CONTEXT_TRACKING_USER <<
166 default y if !NO_HZ_FULL <<
167 help <<
168 The major pre-requirement for full d <<
169 support the user context tracking su <<
170 other dependencies to provide in ord <<
171 dynticks working. <<
172 <<
173 This option stands for testing when <<
174 user context tracking backend but do <<
175 requirements to make the full dyntic <<
176 Without the full dynticks, there is <<
177 for user context tracking and the su <<
178 userspace extended quiescent state a <<
179 accounting. This option copes with t <<
180 dynticks subsystem by forcing the us <<
181 CPUs in the system. <<
182 <<
183 Say Y only if you're working on the <<
184 architecture backend for the user co <<
185 <<
186 Say N otherwise, this option brings <<
187 don't want in production. <<
188 125
189 config NO_HZ 126 config NO_HZ
190 bool "Old Idle dynticks config" 127 bool "Old Idle dynticks config"
>> 128 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
191 help 129 help
192 This is the old config entry that en 130 This is the old config entry that enables dynticks idle.
193 We keep it around for a little while 131 We keep it around for a little while to enforce backward
194 compatibility with older config file 132 compatibility with older config files.
195 133
196 config HIGH_RES_TIMERS 134 config HIGH_RES_TIMERS
197 bool "High Resolution Timer Support" 135 bool "High Resolution Timer Support"
>> 136 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
198 select TICK_ONESHOT 137 select TICK_ONESHOT
199 help 138 help
200 This option enables high resolution 139 This option enables high resolution timer support. If your
201 hardware is not capable then this op 140 hardware is not capable then this option only increases
202 the size of the kernel image. 141 the size of the kernel image.
203 <<
204 config CLOCKSOURCE_WATCHDOG_MAX_SKEW_US <<
205 int "Clocksource watchdog maximum allo <<
206 depends on CLOCKSOURCE_WATCHDOG <<
207 range 50 1000 <<
208 default 125 <<
209 help <<
210 Specify the maximum amount of allowa <<
211 microseconds before reporting the cl <<
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 <<
216 142
217 endmenu 143 endmenu
218 endif 144 endif
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