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Diffstat (limited to 'kernel/time/Kconfig')
| -rw-r--r-- | kernel/time/Kconfig | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig new file mode 100644 index 000000000..7ceb68656 --- /dev/null +++ b/kernel/time/Kconfig @@ -0,0 +1,199 @@ +# +# 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 + +# 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 && !SCHED_BFS + # 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 |