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nohz: Unhide full dynticks feature from its dependencies

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The full dynticks feature only shows up when all its
Kconfig dependencies are met (RCU nocbs, RCU user mode, ...)

This is far from being user friendly as those who want to
activate this feature need to look into the Kconfig files
and iterate through each dependency then activate these
by hand in order to show and select the full dynticks
Kconfig option.

So process the other way around: show up the Kconfig option
if the minimal low level dependencies are met and activate
the high level ones when we enable the feature.

Note there is one exception in the picture:
CONFIG_VIRT_CPU_ACCOUNTING_GEN is part of a Kconfig choice
menu and it appears we can't select it from another Kconfig
selection when it's under such layout. So for now this
particular item stays as a passive dependency.

Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Frederic 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>
This commit is contained in:
Frederic Weisbecker 2011-08-10 23:21:01 +02:00
parent 1c20091e77
commit ab71d36ddb
1 changed files with 14 additions and 5 deletions
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19
kernel/time/Kconfig
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@ -80,11 +80,20 @@ config NO_HZ
busy and when the system is idle. busy and when the system is idle.
config NO_HZ_EXTENDED config NO_HZ_EXTENDED
bool "Full dynticks system" bool "Full dynticks system"
depends on NO_HZ && RCU_USER_QS && VIRT_CPU_ACCOUNTING_GEN && RCU_NOCB_CPU && SMP # NO_HZ dependency
select CONTEXT_TRACKING_FORCE depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
help # RCU_USER_QS
Adaptively try to shutdown the tick whenever possible, even when depends on HAVE_CONTEXT_TRACKING && SMP
# RCU_NOCB_CPU dependency
depends on TREE_RCU || TREE_PREEMPT_RCU
depends on VIRT_CPU_ACCOUNTING_GEN
select NO_HZ
select RCU_USER_QS
select RCU_NOCB_CPU
select CONTEXT_TRACKING_FORCE
help
Adaptively try to shutdown the tick whenever possible, even when
the CPU is running tasks. Typically this requires running a single the CPU is running tasks. Typically this requires running a single
task on the CPU. Chances for running tickless are maximized when task on the CPU. Chances for running tickless are maximized when
the task mostly runs in userspace and has few kernel activity. the task mostly runs in userspace and has few kernel activity.