Merge commit '8700c95adb03' into timers/nohz

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / init / Kconfig

diff --git a/init/Kconfig b/init/Kconfig
index 8f97a7407714736cf6507c1d6f897f3303f12e6f..66f67afad4fad4758d802938d5c3a4fefbc4dbf4 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -28,10 +28,6 @@ config BUILDTIME_EXTABLE_SORT
 
 menu "General setup"
 
-config EXPERIMENTAL
-       bool
-       default y
-
 config BROKEN
        bool
 
@@ -583,13 +579,16 @@ config RCU_FAST_NO_HZ
        depends on NO_HZ_COMMON && SMP
        default n
        help
-         This option causes RCU to attempt to accelerate grace periods in
-         order to allow CPUs to enter dynticks-idle state more quickly.
-         On the other hand, this option increases the overhead of the
-         dynticks-idle checking, thus degrading scheduling latency.
+         This option permits CPUs to enter dynticks-idle state even if
+         they have RCU callbacks queued, and prevents RCU from waking
+         these CPUs up more than roughly once every four jiffies (by
+         default, you can adjust this using the rcutree.rcu_idle_gp_delay
+         parameter), thus improving energy efficiency.  On the other
+         hand, this option increases the duration of RCU grace periods,
+         for example, slowing down synchronize_rcu().
 
-         Say Y if energy efficiency is critically important, and you don't
-               care about real-time response.
+         Say Y if energy efficiency is critically important, and you
+               don't care about increased grace-period durations.
 
          Say N if you are unsure.
 
@@ -656,7 +655,7 @@ config RCU_BOOST_DELAY
          Accept the default if unsure.
 
 config RCU_NOCB_CPU
-       bool "Offload RCU callback processing from boot-selected CPUs"
+       bool "Offload RCU callback processing from boot-selected CPUs (EXPERIMENTAL"
        depends on TREE_RCU || TREE_PREEMPT_RCU
        default n
        help
@@ -667,16 +666,56 @@ config RCU_NOCB_CPU
 
          This option offloads callback invocation from the set of
          CPUs specified at boot time by the rcu_nocbs parameter.
-         For each such CPU, a kthread ("rcuoN") will be created to
-         invoke callbacks, where the "N" is the CPU being offloaded.
-         Nothing prevents this kthread from running on the specified
-         CPUs, but (1) the kthreads may be preempted between each
-         callback, and (2) affinity or cgroups can be used to force
-         the kthreads to run on whatever set of CPUs is desired.
-
-         Say Y here if you want reduced OS jitter on selected CPUs.
+         For each such CPU, a kthread ("rcuox/N") will be created to
+         invoke callbacks, where the "N" is the CPU being offloaded,
+         and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
+         "s" for RCU-sched.  Nothing prevents this kthread from running
+         on the specified CPUs, but (1) the kthreads may be preempted
+         between each callback, and (2) affinity or cgroups can be used
+         to force the kthreads to run on whatever set of CPUs is desired.
+
+         Say Y here if you want to help to debug reduced OS jitter.
          Say N here if you are unsure.
 
+choice
+       prompt "Build-forced no-CBs CPUs"
+       default RCU_NOCB_CPU_NONE
+       help
+         This option allows no-CBs CPUs to be specified at build time.
+         Additional no-CBs CPUs may be specified by the rcu_nocbs=
+         boot parameter.
+
+config RCU_NOCB_CPU_NONE
+       bool "No build_forced no-CBs CPUs"
+       depends on RCU_NOCB_CPU
+       help
+         This option does not force any of the CPUs to be no-CBs CPUs.
+         Only CPUs designated by the rcu_nocbs= boot parameter will be
+         no-CBs CPUs.
+
+config RCU_NOCB_CPU_ZERO
+       bool "CPU 0 is a build_forced no-CBs CPU"
+       depends on RCU_NOCB_CPU
+       help
+         This option forces CPU 0 to be a no-CBs CPU.  Additional CPUs
+         may be designated as no-CBs CPUs using the rcu_nocbs= boot
+         parameter will be no-CBs CPUs.
+
+         Select this if CPU 0 needs to be a no-CBs CPU for real-time
+         or energy-efficiency reasons.
+
+config RCU_NOCB_CPU_ALL
+       bool "All CPUs are build_forced no-CBs CPUs"
+       depends on RCU_NOCB_CPU
+       help
+         This option forces all CPUs to be no-CBs CPUs.  The rcu_nocbs=
+         boot parameter will be ignored.
+
+         Select this if all CPUs need to be no-CBs CPUs for real-time
+         or energy-efficiency reasons.
+
+endchoice
+
 endmenu # "RCU Subsystem"
 
 config IKCONFIG