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# Timekeeping vsyscall support
16config GENERIC_TIME_VSYSCALL
 
 
 
 
 
17	bool
18
19# ktime_t scalar 64bit nsec representation
20config KTIME_SCALAR
21	bool
22
23# Old style timekeeping
24config ARCH_USES_GETTIMEOFFSET
25	bool
26
27# The generic clock events infrastructure
28config GENERIC_CLOCKEVENTS
29	bool
30
31# Migration helper. Builds, but does not invoke
32config GENERIC_CLOCKEVENTS_BUILD
33	bool
34	default y
35	depends on GENERIC_CLOCKEVENTS
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
51if GENERIC_CLOCKEVENTS
52menu "Timers subsystem"
53
54# Core internal switch. Selected by NO_HZ / HIGH_RES_TIMERS. This is
55# only related to the tick functionality. Oneshot clockevent devices
56# are supported independ of this.
57config TICK_ONESHOT
58	bool
59
60config NO_HZ
61	bool "Tickless System (Dynamic Ticks)"
62	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
63	select TICK_ONESHOT
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
64	help
65	  This option enables a tickless system: timer interrupts will
66	  only trigger on an as-needed basis both when the system is
67	  busy and when the system is idle.
68
69config HIGH_RES_TIMERS
70	bool "High Resolution Timer Support"
71	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
72	select TICK_ONESHOT
73	help
74	  This option enables high resolution timer support. If your
75	  hardware is not capable then this option only increases
76	  the size of the kernel image.
77
78endmenu
79endif

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