| # |
| # 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 |
| |
| # 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 |
| |
| # Timekeeping vsyscall support |
| config GENERIC_TIME_VSYSCALL_OLD |
| bool |
| |
| # Old style timekeeping |
| config ARCH_USES_GETTIMEOFFSET |
| bool |
| |
| # The generic clock events infrastructure |
| config GENERIC_CLOCKEVENTS |
| bool |
| |
| # Migration helper. Builds, but does not invoke |
| config GENERIC_CLOCKEVENTS_BUILD |
| bool |
| default y |
| depends on GENERIC_CLOCKEVENTS |
| |
| # 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 |
| |
| 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 independ of this. |
| config TICK_ONESHOT |
| bool |
| |
| config NO_HZ_COMMON |
| bool |
| depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS |
| 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)" |
| depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS |
| 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 |
| depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS |
| # We need at least one periodic CPU for timekeeping |
| depends on SMP |
| # RCU_USER_QS dependency |
| depends on HAVE_CONTEXT_TRACKING |
| # VIRT_CPU_ACCOUNTING_GEN dependency |
| depends on HAVE_VIRT_CPU_ACCOUNTING_GEN |
| select NO_HZ_COMMON |
| select RCU_USER_QS |
| select RCU_NOCB_CPU |
| select VIRT_CPU_ACCOUNTING_GEN |
| select IRQ_WORK |
| 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 NO_HZ_FULL_ALL |
| bool "Full dynticks system on all CPUs by default (except CPU 0)" |
| depends on NO_HZ_FULL |
| help |
| If the user doesn't pass the nohz_full boot option to |
| define the range of full dynticks CPUs, consider that all |
| CPUs in the system are full dynticks by default. |
| Note the boot CPU will still be kept outside the range to |
| handle the timekeeping duty. |
| |
| config NO_HZ_FULL_SYSIDLE |
| bool "Detect full-system idle state for full dynticks system" |
| depends on NO_HZ_FULL |
| default n |
| help |
| At least one CPU must keep the scheduling-clock tick running for |
| timekeeping purposes whenever there is a non-idle CPU, where |
| "non-idle" also includes dynticks CPUs as long as they are |
| running non-idle tasks. Because the underlying adaptive-tick |
| support cannot distinguish between all CPUs being idle and |
| all CPUs each running a single task in dynticks mode, the |
| underlying support simply ensures that there is always a CPU |
| handling the scheduling-clock tick, whether or not all CPUs |
| are idle. This Kconfig option enables scalable detection of |
| the all-CPUs-idle state, thus allowing the scheduling-clock |
| tick to be disabled when all CPUs are idle. Note that scalable |
| detection of the all-CPUs-idle state means that larger systems |
| will be slower to declare the all-CPUs-idle state. |
| |
| Say Y if you would like to help debug all-CPUs-idle detection. |
| |
| Say N if you are unsure. |
| |
| config NO_HZ_FULL_SYSIDLE_SMALL |
| int "Number of CPUs above which large-system approach is used" |
| depends on NO_HZ_FULL_SYSIDLE |
| range 1 NR_CPUS |
| default 8 |
| help |
| The full-system idle detection mechanism takes a lazy approach |
| on large systems, as is required to attain decent scalability. |
| However, on smaller systems, scalability is not anywhere near as |
| large a concern as is energy efficiency. The sysidle subsystem |
| therefore uses a fast but non-scalable algorithm for small |
| systems and a lazier but scalable algorithm for large systems. |
| This Kconfig parameter defines the number of CPUs in the largest |
| system that will be considered to be "small". |
| |
| The default value will be fine in most cases. Battery-powered |
| systems that (1) enable NO_HZ_FULL_SYSIDLE, (2) have larger |
| numbers of CPUs, and (3) are suffering from battery-lifetime |
| problems due to long sysidle latencies might wish to experiment |
| with larger values for this Kconfig parameter. On the other |
| hand, they might be even better served by disabling NO_HZ_FULL |
| entirely, given that NO_HZ_FULL is intended for HPC and |
| real-time workloads that at present do not tend to be run on |
| battery-powered systems. |
| |
| Take the default if you are unsure. |
| |
| config NO_HZ |
| bool "Old Idle dynticks config" |
| depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS |
| 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" |
| depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS |
| 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. |
| |
| endmenu |
| endif |
