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Diffstat (limited to 'kernel/time/Kconfig')
| -rw-r--r-- | kernel/time/Kconfig | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig new file mode 100644 index 0000000000..bae8f11070 --- /dev/null +++ b/kernel/time/Kconfig @@ -0,0 +1,213 @@ +# 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 CLOCKSOURCE_WATCHDOG + bool + +# Architecture has extra clocksource data +config ARCH_CLOCKSOURCE_DATA + bool + +# Architecture has extra clocksource init called from registration +config ARCH_CLOCKSOURCE_INIT + bool + +# Clocksources require validation of the clocksource against the last +# cycle update - x86/TSC misfeature +config CLOCKSOURCE_VALIDATE_LAST_CYCLE + bool + +# Timekeeping vsyscall support +config GENERIC_TIME_VSYSCALL + bool + +# The generic clock events infrastructure +config GENERIC_CLOCKEVENTS + def_bool !LEGACY_TIMER_TICK + +# Architecture can handle broadcast in a driver-agnostic way +config ARCH_HAS_TICK_BROADCAST + bool + +# Clockevents broadcasting infrastructure +config GENERIC_CLOCKEVENTS_BROADCAST + bool + depends on GENERIC_CLOCKEVENTS + +# Automatically adjust the min. reprogramming time for +# clock event device +config GENERIC_CLOCKEVENTS_MIN_ADJUST + bool + +# Generic update of CMOS clock +config GENERIC_CMOS_UPDATE + bool + +# Select to handle posix CPU timers from task_work +# and not from the timer interrupt context +config HAVE_POSIX_CPU_TIMERS_TASK_WORK + bool + +config POSIX_CPU_TIMERS_TASK_WORK + bool + default y if POSIX_TIMERS && HAVE_POSIX_CPU_TIMERS_TASK_WORK + +config LEGACY_TIMER_TICK + bool + help + The legacy timer tick helper is used by platforms that + lack support for the generic clockevent framework. + New platforms should use generic clockevents instead. + +config TIME_KUNIT_TEST + tristate "KUnit test for kernel/time functions" if !KUNIT_ALL_TESTS + depends on KUNIT + default KUNIT_ALL_TESTS + help + Enable this option to test RTC library functions. + + If unsure, say N. + +config CONTEXT_TRACKING + bool + +config CONTEXT_TRACKING_IDLE + bool + select CONTEXT_TRACKING + help + Tracks idle state on behalf of RCU. + +if GENERIC_CLOCKEVENTS +menu "Timers subsystem" + +# Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is +# only related to the tick functionality. Oneshot clockevent devices +# are supported independent of this. +config TICK_ONESHOT + bool + +config NO_HZ_COMMON + bool + select TICK_ONESHOT + +choice + prompt "Timer tick handling" + default NO_HZ_IDLE if NO_HZ + +config HZ_PERIODIC + 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 NO_HZ_IDLE + bool "Idle dynticks system (tickless idle)" + select NO_HZ_COMMON + 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 NO_HZ_FULL + bool "Full dynticks system (tickless)" + # NO_HZ_COMMON dependency + # We need at least one periodic CPU for timekeeping + depends on SMP + depends on HAVE_CONTEXT_TRACKING_USER + # VIRT_CPU_ACCOUNTING_GEN dependency + depends on HAVE_VIRT_CPU_ACCOUNTING_GEN + select NO_HZ_COMMON + select RCU_NOCB_CPU + select VIRT_CPU_ACCOUNTING_GEN + select IRQ_WORK + select CPU_ISOLATION + 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 to use it. This is implemented at + the expense of some overhead in user <-> kernel transitions: + syscalls, exceptions and interrupts. + + By default, without passing the nohz_full parameter, this behaves just + like NO_HZ_IDLE. + + If you're a distro say Y. + +endchoice + +config CONTEXT_TRACKING_USER + bool + depends on HAVE_CONTEXT_TRACKING_USER + select CONTEXT_TRACKING + help + Track transitions between kernel and user on behalf of RCU and + tickless cputime accounting. The former case relies on context + tracking to enter/exit RCU extended quiescent states. + +config CONTEXT_TRACKING_USER_FORCE + bool "Force user context tracking" + depends on CONTEXT_TRACKING_USER + default y if !NO_HZ_FULL + help + The major pre-requirement for full dynticks to work is to + support the user 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 + user context tracking backend but doesn't yet fulfill all the + requirements to make the full dynticks feature working. + Without the full dynticks, there is no way to test the support + for user 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 user context tracking on all + CPUs in the system. + + Say Y only if you're working on the development of an + architecture backend for the user context tracking. + + Say N otherwise, this option brings an overhead that you + don't want in production. + +config NO_HZ + bool "Old Idle dynticks config" + 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 HIGH_RES_TIMERS + bool "High Resolution Timer Support" + select TICK_ONESHOT + 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. + +config CLOCKSOURCE_WATCHDOG_MAX_SKEW_US + int "Clocksource watchdog maximum allowable skew (in μs)" + depends on CLOCKSOURCE_WATCHDOG + range 50 1000 + default 125 + help + Specify the maximum amount of allowable watchdog skew in + microseconds before reporting the clocksource to be unstable. + The default is based on a half-second clocksource watchdog + interval and NTP's maximum frequency drift of 500 parts + per million. If the clocksource is good enough for NTP, + it is good enough for the clocksource watchdog! + +endmenu +endif |