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