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 # Timekeeping vsyscall support
>> 25 config GENERIC_TIME_VSYSCALL_OLD
>> 26 bool
>> 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 independ 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 <<
136 help 102 help
137 Adaptively try to shutdown the tick w 103 Adaptively try to shutdown the tick whenever possible, even when
138 the CPU is running tasks. Typically t 104 the CPU is running tasks. Typically this requires running a single
139 task on the CPU. Chances for running 105 task on the CPU. Chances for running tickless are maximized when
140 the task mostly runs in userspace and 106 the task mostly runs in userspace and has few kernel activity.
141 107
142 You need to fill up the nohz_full boo 108 You need to fill up the nohz_full boot parameter with the
143 desired range of dynticks CPUs to use !! 109 desired range of dynticks CPUs.
144 the expense of some overhead in user <<
145 syscalls, exceptions and interrupts. <<
146 110
147 By default, without passing the nohz_ !! 111 This is implemented at the expense of some overhead in user <-> kernel
148 like NO_HZ_IDLE. !! 112 transitions: syscalls, exceptions and interrupts. Even when it's
>> 113 dynamically off.
149 114
150 If you're a distro say Y. !! 115 Say N.
151 116
152 endchoice 117 endchoice
153 118
154 config CONTEXT_TRACKING_USER !! 119 config NO_HZ_FULL_ALL
155 bool !! 120 bool "Full dynticks system on all CPUs by default (except CPU 0)"
156 depends on HAVE_CONTEXT_TRACKING_USER !! 121 depends on NO_HZ_FULL
157 select CONTEXT_TRACKING !! 122 help
158 help !! 123 If the user doesn't pass the nohz_full boot option to
159 Track transitions between kernel and !! 124 define the range of full dynticks CPUs, consider that all
160 tickless cputime accounting. The for !! 125 CPUs in the system are full dynticks by default.
161 tracking to enter/exit RCU extended !! 126 Note the boot CPU will still be kept outside the range to
162 !! 127 handle the timekeeping duty.
163 config CONTEXT_TRACKING_USER_FORCE !! 128
164 bool "Force user context tracking" !! 129 config NO_HZ_FULL_SYSIDLE
165 depends on CONTEXT_TRACKING_USER !! 130 bool "Detect full-system idle state for full dynticks system"
166 default y if !NO_HZ_FULL !! 131 depends on NO_HZ_FULL
167 help !! 132 default n
168 The major pre-requirement for full d !! 133 help
169 support the user context tracking su !! 134 At least one CPU must keep the scheduling-clock tick running for
170 other dependencies to provide in ord !! 135 timekeeping purposes whenever there is a non-idle CPU, where
171 dynticks working. !! 136 "non-idle" also includes dynticks CPUs as long as they are
172 !! 137 running non-idle tasks. Because the underlying adaptive-tick
173 This option stands for testing when !! 138 support cannot distinguish between all CPUs being idle and
174 user context tracking backend but do !! 139 all CPUs each running a single task in dynticks mode, the
175 requirements to make the full dyntic !! 140 underlying support simply ensures that there is always a CPU
176 Without the full dynticks, there is !! 141 handling the scheduling-clock tick, whether or not all CPUs
177 for user context tracking and the su !! 142 are idle. This Kconfig option enables scalable detection of
178 userspace extended quiescent state a !! 143 the all-CPUs-idle state, thus allowing the scheduling-clock
179 accounting. This option copes with t !! 144 tick to be disabled when all CPUs are idle. Note that scalable
180 dynticks subsystem by forcing the us !! 145 detection of the all-CPUs-idle state means that larger systems
181 CPUs in the system. !! 146 will be slower to declare the all-CPUs-idle state.
182 !! 147
183 Say Y only if you're working on the !! 148 Say Y if you would like to help debug all-CPUs-idle detection.
184 architecture backend for the user co !! 149
>> 150 Say N if you are unsure.
>> 151
>> 152 config NO_HZ_FULL_SYSIDLE_SMALL
>> 153 int "Number of CPUs above which large-system approach is used"
>> 154 depends on NO_HZ_FULL_SYSIDLE
>> 155 range 1 NR_CPUS
>> 156 default 8
>> 157 help
>> 158 The full-system idle detection mechanism takes a lazy approach
>> 159 on large systems, as is required to attain decent scalability.
>> 160 However, on smaller systems, scalability is not anywhere near as
>> 161 large a concern as is energy efficiency. The sysidle subsystem
>> 162 therefore uses a fast but non-scalable algorithm for small
>> 163 systems and a lazier but scalable algorithm for large systems.
>> 164 This Kconfig parameter defines the number of CPUs in the largest
>> 165 system that will be considered to be "small".
>> 166
>> 167 The default value will be fine in most cases. Battery-powered
>> 168 systems that (1) enable NO_HZ_FULL_SYSIDLE, (2) have larger
>> 169 numbers of CPUs, and (3) are suffering from battery-lifetime
>> 170 problems due to long sysidle latencies might wish to experiment
>> 171 with larger values for this Kconfig parameter. On the other
>> 172 hand, they might be even better served by disabling NO_HZ_FULL
>> 173 entirely, given that NO_HZ_FULL is intended for HPC and
>> 174 real-time workloads that at present do not tend to be run on
>> 175 battery-powered systems.
185 176
186 Say N otherwise, this option brings !! 177 Take the default if you are unsure.
187 don't want in production. <<
188 178
189 config NO_HZ 179 config NO_HZ
190 bool "Old Idle dynticks config" 180 bool "Old Idle dynticks config"
>> 181 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
191 help 182 help
192 This is the old config entry that en 183 This is the old config entry that enables dynticks idle.
193 We keep it around for a little while 184 We keep it around for a little while to enforce backward
194 compatibility with older config file 185 compatibility with older config files.
195 186
196 config HIGH_RES_TIMERS 187 config HIGH_RES_TIMERS
197 bool "High Resolution Timer Support" 188 bool "High Resolution Timer Support"
>> 189 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
198 select TICK_ONESHOT 190 select TICK_ONESHOT
199 help 191 help
200 This option enables high resolution 192 This option enables high resolution timer support. If your
201 hardware is not capable then this op 193 hardware is not capable then this option only increases
202 the size of the kernel image. 194 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 <<
216 195
217 endmenu 196 endmenu
218 endif 197 endif
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