LXR linux/kernel/time/Kconfig

   1#
   2# Timer subsystem related configuration options
   3#
   4
   5# Options selectable by arch Kconfig
   6
   7# Watchdog function for clocksources to detect instabilities
   8config CLOCKSOURCE_WATCHDOG
   9        bool
  10
  11# Architecture has extra clocksource data
  12config ARCH_CLOCKSOURCE_DATA
  13        bool
  14
  15# Clocksources require validation of the clocksource against the last
  16# cycle update - x86/TSC misfeature
  17config CLOCKSOURCE_VALIDATE_LAST_CYCLE
  18        bool
  19
  20# Timekeeping vsyscall support
  21config GENERIC_TIME_VSYSCALL
  22        bool
  23
  24# Old style timekeeping
  25config ARCH_USES_GETTIMEOFFSET
  26        bool
  27
  28# The generic clock events infrastructure
  29config GENERIC_CLOCKEVENTS
  30        bool
  31
  32# Architecture can handle broadcast in a driver-agnostic way
  33config ARCH_HAS_TICK_BROADCAST
  34        bool
  35
  36# Clockevents broadcasting infrastructure
  37config GENERIC_CLOCKEVENTS_BROADCAST
  38        bool
  39        depends on GENERIC_CLOCKEVENTS
  40
  41# Automatically adjust the min. reprogramming time for
  42# clock event device
  43config GENERIC_CLOCKEVENTS_MIN_ADJUST
  44        bool
  45
  46# Generic update of CMOS clock
  47config GENERIC_CMOS_UPDATE
  48        bool
  49
  50if GENERIC_CLOCKEVENTS
  51menu "Timers subsystem"
  52
  53# Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is
  54# only related to the tick functionality. Oneshot clockevent devices
  55# are supported independent of this.
  56config TICK_ONESHOT
  57        bool
  58
  59config NO_HZ_COMMON
  60        bool
  61        depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
  62        select TICK_ONESHOT
  63
  64choice
  65        prompt "Timer tick handling"
  66        default NO_HZ_IDLE if NO_HZ
  67
  68config HZ_PERIODIC
  69        bool "Periodic timer ticks (constant rate, no dynticks)"
  70        help
  71          This option keeps the tick running periodically at a constant
  72          rate, even when the CPU doesn't need it.
  73
  74config NO_HZ_IDLE
  75        bool "Idle dynticks system (tickless idle)"
  76        depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
  77        select NO_HZ_COMMON
  78        help
  79          This option enables a tickless idle system: timer interrupts
  80          will only trigger on an as-needed basis when the system is idle.
  81          This is usually interesting for energy saving.
  82
  83          Most of the time you want to say Y here.
  84
  85config NO_HZ_FULL
  86        bool "Full dynticks system (tickless)"
  87        # NO_HZ_COMMON dependency
  88        depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
  89        # We need at least one periodic CPU for timekeeping
  90        depends on SMP
  91        depends on HAVE_CONTEXT_TRACKING
  92        # VIRT_CPU_ACCOUNTING_GEN dependency
  93        depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
  94        select NO_HZ_COMMON
  95        select RCU_NOCB_CPU
  96        select VIRT_CPU_ACCOUNTING_GEN
  97        select IRQ_WORK
  98        select CPU_ISOLATION
  99        help
 100         Adaptively try to shutdown the tick whenever possible, even when
 101         the CPU is running tasks. Typically this requires running a single
 102         task on the CPU. Chances for running tickless are maximized when
 103         the task mostly runs in userspace and has few kernel activity.
 104
 105         You need to fill up the nohz_full boot parameter with the
 106         desired range of dynticks CPUs.
 107
 108         This is implemented at the expense of some overhead in user <-> kernel
 109         transitions: syscalls, exceptions and interrupts. Even when it's
 110         dynamically off.
 111
 112         Say N.
 113
 114endchoice
 115
 116config NO_HZ_FULL_ALL
 117       bool "Full dynticks system on all CPUs by default (except CPU 0)"
 118       depends on NO_HZ_FULL
 119       help
 120         If the user doesn't pass the nohz_full boot option to
 121         define the range of full dynticks CPUs, consider that all
 122         CPUs in the system are full dynticks by default.
 123         Note the boot CPU will still be kept outside the range to
 124         handle the timekeeping duty.
 125
 126config NO_HZ
 127        bool "Old Idle dynticks config"
 128        depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
 129        help
 130          This is the old config entry that enables dynticks idle.
 131          We keep it around for a little while to enforce backward
 132          compatibility with older config files.
 133
 134config HIGH_RES_TIMERS
 135        bool "High Resolution Timer Support"
 136        depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
 137        select TICK_ONESHOT
 138        help
 139          This option enables high resolution timer support. If your
 140          hardware is not capable then this option only increases
 141          the size of the kernel image.
 142
 143endmenu
 144endif
 145