# SPDX-License-Identifier: GPL-2.0-only
#
# Timer subsystem related configuration options
#
# Options selectable by arch Kconfig
# Watchdog function for clocksources to detect instabilities
config [31mCONFIG_CLOCKSOURCE_WATCHDOG[0m
bool
# Architecture has extra clocksource data
config [31mCONFIG_ARCH_CLOCKSOURCE_DATA[0m
bool
# Architecture has extra clocksource init called from registration
config [31mCONFIG_ARCH_CLOCKSOURCE_INIT[0m
bool
# Clocksources require validation of the clocksource against the last
# cycle update - x86/TSC misfeature
config [31mCONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE[0m
bool
# Timekeeping vsyscall support
config [31mCONFIG_GENERIC_TIME_VSYSCALL[0m
bool
# Old style timekeeping
config [31mCONFIG_ARCH_USES_GETTIMEOFFSET[0m
bool
# The generic clock events infrastructure
config [31mCONFIG_GENERIC_CLOCKEVENTS[0m
bool
# Architecture can handle broadcast in a driver-agnostic way
config [31mCONFIG_ARCH_HAS_TICK_BROADCAST[0m
bool
# Clockevents broadcasting infrastructure
config [31mCONFIG_GENERIC_CLOCKEVENTS_BROADCAST[0m
bool
depends on [31mCONFIG_GENERIC_CLOCKEVENTS[0m
# Automatically adjust the min. reprogramming time for
# clock event device
config [31mCONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST[0m
bool
# Generic update of CMOS clock
config [31mCONFIG_GENERIC_CMOS_UPDATE[0m
bool
if [31mCONFIG_GENERIC_CLOCKEVENTS[0m
menu "Timers subsystem"
# Core internal switch. Selected by [31mCONFIG_NO_HZ_COMMON[0m / [31mCONFIG_HIGH_RES_TIMERS[0m. This is
# only related to the tick functionality. Oneshot clockevent devices
# are supported independent of this.
config [31mCONFIG_TICK_ONESHOT[0m
bool
config [31mCONFIG_NO_HZ_COMMON[0m
bool
depends on ![31mCONFIG_ARCH_USES_GETTIMEOFFSET[0m && [31mCONFIG_GENERIC_CLOCKEVENTS[0m
select [31mCONFIG_TICK_ONESHOT[0m
choice
prompt "Timer tick handling"
default [31mCONFIG_NO_HZ_IDLE[0m if [31mCONFIG_NO_HZ[0m
config [31mCONFIG_HZ_PERIODIC[0m
bool "Periodic timer ticks (constant rate, no dynticks)"
help
This option keeps the tick running periodically at a constant
rate, even when the CPU doesn't need it.
config [31mCONFIG_NO_HZ_IDLE[0m
bool "Idle dynticks system (tickless idle)"
depends on ![31mCONFIG_ARCH_USES_GETTIMEOFFSET[0m && [31mCONFIG_GENERIC_CLOCKEVENTS[0m
select [31mCONFIG_NO_HZ_COMMON[0m
help
This option enables a tickless idle system: timer interrupts
will only trigger on an as-needed basis when the system is idle.
This is usually interesting for energy saving.
Most of the time you want to say Y here.
config [31mCONFIG_NO_HZ_FULL[0m
bool "Full dynticks system (tickless)"
# [31mCONFIG_NO_HZ_COMMON[0m dependency
depends on ![31mCONFIG_ARCH_USES_GETTIMEOFFSET[0m && [31mCONFIG_GENERIC_CLOCKEVENTS[0m
# We need at least one periodic CPU for timekeeping
depends on [31mCONFIG_SMP[0m
depends on [31mCONFIG_HAVE_CONTEXT_TRACKING[0m
# [31mCONFIG_VIRT_CPU_ACCOUNTING_GEN[0m dependency
depends on [31mCONFIG_HAVE_VIRT_CPU_ACCOUNTING_GEN[0m
select [31mCONFIG_NO_HZ_COMMON[0m
select [31mCONFIG_RCU_NOCB_CPU[0m
select [31mCONFIG_VIRT_CPU_ACCOUNTING_GEN[0m
select [31mCONFIG_IRQ_WORK[0m
select [31mCONFIG_CPU_ISOLATION[0m
help
Adaptively try to shutdown the tick whenever possible, even when
the CPU is running tasks. Typically this requires running a single
task on the CPU. Chances for running tickless are maximized when
the task mostly runs in userspace and has few kernel activity.
You need to fill up the nohz_full boot parameter with the
desired range of dynticks CPUs.
This is implemented at the expense of some overhead in user <-> kernel
transitions: syscalls, exceptions and interrupts. Even when it's
dynamically off.
Say N.
endchoice
config [31mCONFIG_CONTEXT_TRACKING[0m
bool
config [31mCONFIG_CONTEXT_TRACKING_FORCE[0m
bool "Force context tracking"
depends on [31mCONFIG_CONTEXT_TRACKING[0m
default y if ![31mCONFIG_NO_HZ_FULL[0m
help
The major pre-requirement for full dynticks to work is to
support the context tracking subsystem. But there are also
other dependencies to provide in order to make the full
dynticks working.
This option stands for testing when an arch implements the
context tracking backend but doesn't yet fullfill all the
requirements to make the full dynticks feature working.
Without the full dynticks, there is no way to test the support
for context tracking and the subsystems that rely on it: RCU
userspace extended quiescent state and tickless cputime
accounting. This option copes with the absence of the full
dynticks subsystem by forcing the context tracking on all
CPUs in the system.
Say Y only if you're working on the development of an
architecture backend for the context tracking.
Say N otherwise, this option brings an overhead that you
don't want in production.
config [31mCONFIG_NO_HZ[0m
bool "Old Idle dynticks config"
depends on ![31mCONFIG_ARCH_USES_GETTIMEOFFSET[0m && [31mCONFIG_GENERIC_CLOCKEVENTS[0m
help
This is the old config entry that enables dynticks idle.
We keep it around for a little while to enforce backward
compatibility with older config files.
config [31mCONFIG_HIGH_RES_TIMERS[0m
bool "High Resolution Timer Support"
depends on ![31mCONFIG_ARCH_USES_GETTIMEOFFSET[0m && [31mCONFIG_GENERIC_CLOCKEVENTS[0m
select [31mCONFIG_TICK_ONESHOT[0m
help
This option enables high resolution timer support. If your
hardware is not capable then this option only increases
the size of the kernel image.
endmenu
endif