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