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

 
  1#
  2# Timer subsystem related configuration options
  3#
  4
  5# Options selectable by arch Kconfig
  6
  7# Watchdog function for clocksources to detect instabilities
  8config CLOCKSOURCE_WATCHDOG
  9	bool
 10
 11# Architecture has extra clocksource data
 12config ARCH_CLOCKSOURCE_DATA
 13	bool
 14
 
 
 
 
 15# Clocksources require validation of the clocksource against the last
 16# cycle update - x86/TSC misfeature
 17config CLOCKSOURCE_VALIDATE_LAST_CYCLE
 18	bool
 19
 20# Timekeeping vsyscall support
 21config GENERIC_TIME_VSYSCALL
 22	bool
 23
 24# Old style timekeeping
 25config ARCH_USES_GETTIMEOFFSET
 26	bool
 27
 28# The generic clock events infrastructure
 29config GENERIC_CLOCKEVENTS
 30	bool
 31
 32# Architecture can handle broadcast in a driver-agnostic way
 33config ARCH_HAS_TICK_BROADCAST
 34	bool
 35
 36# Clockevents broadcasting infrastructure
 37config GENERIC_CLOCKEVENTS_BROADCAST
 38	bool
 39	depends on GENERIC_CLOCKEVENTS
 40
 41# Automatically adjust the min. reprogramming time for
 42# clock event device
 43config GENERIC_CLOCKEVENTS_MIN_ADJUST
 44	bool
 45
 46# Generic update of CMOS clock
 47config GENERIC_CMOS_UPDATE
 48	bool
 49
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 50if GENERIC_CLOCKEVENTS
 51menu "Timers subsystem"
 52
 53# Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is
 54# only related to the tick functionality. Oneshot clockevent devices
 55# are supported independent of this.
 56config TICK_ONESHOT
 57	bool
 58
 59config NO_HZ_COMMON
 60	bool
 61	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
 62	select TICK_ONESHOT
 63
 64choice
 65	prompt "Timer tick handling"
 66	default NO_HZ_IDLE if NO_HZ
 67
 68config HZ_PERIODIC
 69	bool "Periodic timer ticks (constant rate, no dynticks)"
 70	help
 71	  This option keeps the tick running periodically at a constant
 72	  rate, even when the CPU doesn't need it.
 73
 74config NO_HZ_IDLE
 75	bool "Idle dynticks system (tickless idle)"
 76	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
 77	select NO_HZ_COMMON
 78	help
 79	  This option enables a tickless idle system: timer interrupts
 80	  will only trigger on an as-needed basis when the system is idle.
 81	  This is usually interesting for energy saving.
 82
 83	  Most of the time you want to say Y here.
 84
 85config NO_HZ_FULL
 86	bool "Full dynticks system (tickless)"
 87	# NO_HZ_COMMON dependency
 88	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
 89	# We need at least one periodic CPU for timekeeping
 90	depends on SMP
 91	depends on HAVE_CONTEXT_TRACKING
 92	# VIRT_CPU_ACCOUNTING_GEN dependency
 93	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
 94	select NO_HZ_COMMON
 95	select RCU_NOCB_CPU
 96	select VIRT_CPU_ACCOUNTING_GEN
 97	select IRQ_WORK
 98	select CPU_ISOLATION
 99	help
100	 Adaptively try to shutdown the tick whenever possible, even when
101	 the CPU is running tasks. Typically this requires running a single
102	 task on the CPU. Chances for running tickless are maximized when
103	 the task mostly runs in userspace and has few kernel activity.
104
105	 You need to fill up the nohz_full boot parameter with the
106	 desired range of dynticks CPUs.
 
 
107
108	 This is implemented at the expense of some overhead in user <-> kernel
109	 transitions: syscalls, exceptions and interrupts. Even when it's
110	 dynamically off.
111
112	 Say N.
113
114endchoice
115
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
116config NO_HZ
117	bool "Old Idle dynticks config"
118	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
119	help
120	  This is the old config entry that enables dynticks idle.
121	  We keep it around for a little while to enforce backward
122	  compatibility with older config files.
123
124config HIGH_RES_TIMERS
125	bool "High Resolution Timer Support"
126	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
127	select TICK_ONESHOT
128	help
129	  This option enables high resolution timer support. If your
130	  hardware is not capable then this option only increases
131	  the size of the kernel image.
 
 
 
 
 
 
 
 
 
132
133endmenu
134endif