nohz: Basic full dynticks interface
[deliverable/linux.git] / kernel / time / Kconfig
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1#
2# Timer subsystem related configuration options
3#
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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
05ad717c 15# Platforms has a persistent clock
6f16eebe 16config ALWAYS_USE_PERSISTENT_CLOCK
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17 bool
18 default n
19
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20# Timekeeping vsyscall support
21config GENERIC_TIME_VSYSCALL
22 bool
23
b5e498ad 24# Timekeeping vsyscall support
70639421 25config GENERIC_TIME_VSYSCALL_OLD
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26 bool
27
28# ktime_t scalar 64bit nsec representation
29config KTIME_SCALAR
30 bool
31
32# Old style timekeeping
33config ARCH_USES_GETTIMEOFFSET
34 bool
35
36# The generic clock events infrastructure
37config GENERIC_CLOCKEVENTS
38 bool
39
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40# Migration helper. Builds, but does not invoke
41config GENERIC_CLOCKEVENTS_BUILD
42 bool
43 default y
44 depends on GENERIC_CLOCKEVENTS
45
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46# Architecture can handle broadcast in a driver-agnostic way
47config ARCH_HAS_TICK_BROADCAST
48 bool
49
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50# Clockevents broadcasting infrastructure
51config GENERIC_CLOCKEVENTS_BROADCAST
52 bool
53 depends on GENERIC_CLOCKEVENTS
54
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55# Automatically adjust the min. reprogramming time for
56# clock event device
57config GENERIC_CLOCKEVENTS_MIN_ADJUST
58 bool
59
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60# Generic update of CMOS clock
61config GENERIC_CMOS_UPDATE
62 bool
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63
64if GENERIC_CLOCKEVENTS
65menu "Timers subsystem"
66
67# Core internal switch. Selected by NO_HZ / HIGH_RES_TIMERS. This is
68# only related to the tick functionality. Oneshot clockevent devices
69# are supported independ of this.
70config TICK_ONESHOT
71 bool
72
73config NO_HZ
74 bool "Tickless System (Dynamic Ticks)"
75 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
76 select TICK_ONESHOT
77 help
78 This option enables a tickless system: timer interrupts will
79 only trigger on an as-needed basis both when the system is
80 busy and when the system is idle.
81
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82config NO_HZ_EXTENDED
83 bool "Full dynticks system"
84 depends on NO_HZ && RCU_USER_QS && VIRT_CPU_ACCOUNTING_GEN && RCU_NOCB_CPU && SMP
85 select CONTEXT_TRACKING_FORCE
86 help
87 Adaptively try to shutdown the tick whenever possible, even when
88 the CPU is running tasks. Typically this requires running a single
89 task on the CPU. Chances for running tickless are maximized when
90 the task mostly runs in userspace and has few kernel activity.
91
92 You need to fill up the nohz_extended boot parameter with the
93 desired range of dynticks CPUs.
94
95 This is implemented at the expense of some overhead in user <-> kernel
96 transitions: syscalls, exceptions and interrupts. Even when it's
97 dynamically off.
98
99 Say N.
100
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101config HIGH_RES_TIMERS
102 bool "High Resolution Timer Support"
103 depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
104 select TICK_ONESHOT
105 help
106 This option enables high resolution timer support. If your
107 hardware is not capable then this option only increases
108 the size of the kernel image.
109
110endmenu
111endif
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