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Commit 3ca277e4 authored by Frederic Weisbecker's avatar Frederic Weisbecker
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nohz: Pack nohz Kconfig option in a menu of choices 



Now the user has the choice between three implementations of
the timer tick:

* Static periodic tick
* Idle dynticks
* Full dynticks

At least for now, these are mutually exclusive choices, so
let's rely on the proper Kconfig feature to display these
to the user.

A new entry CONFIG_NO_HZ_IDLE is created and the old
CONFIG_NO_HZ maps to it for config file backward compatibility.
The old name was too general now that we have more
granular dynticks implementations.

While at it, add some explanation to help the user on
his decision between the 3 entries.

Reported-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
parent 3451d024

kernel/time/Kconfig

+23 −5
Original line number Diff line number Diff line
@@ -75,17 +75,33 @@ config NO_HZ_COMMON 
	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS

	select TICK_ONESHOT



# Kept around for compatibility, maps to NO_HZ_IDLE

config NO_HZ

	bool "Tickless System (Dynamic Ticks)"

	bool



choice

	prompt "Timer tick handling"

	default NO_HZ_IDLE if NO_HZ



config PERIODIC_HZ

	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 system: timer interrupts will

	  only trigger on an as-needed basis both when the system is

	  busy and when the system is idle.

	  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_EXTENDED

	bool "Full dynticks system"

	bool "Full dynticks system (tickless single task)"

	# NO_HZ_COMMON dependency

	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS

	# RCU_USER_QS
@@ -112,6 +128,8 @@ config NO_HZ_EXTENDED 


	 Say N.



endchoice



config HIGH_RES_TIMERS

	bool "High Resolution Timer Support"

	depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS