| # 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 |
