aboutsummaryrefslogtreecommitdiff
path: root/init
diff options
context:
space:
mode:
authorIngo Molnar <mingo@kernel.org>2013-04-10 12:55:49 +0200
committerIngo Molnar <mingo@kernel.org>2013-04-10 12:55:49 +0200
commit8fcfae31719c0a6c03f2cf63f815b46d378d8be4 (patch)
tree3da9d65885de6a2b046fbd5eebc0d19def0c1e2c /init
parentd02a9a89db3437467de45a451739e520877f4a48 (diff)
parent6d87669357936bffa1e8fea7a4e7743e76905736 (diff)
downloadlinux-linaro-stable-8fcfae31719c0a6c03f2cf63f815b46d378d8be4.tar.gz
Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu
Pull RCU updates from Paul E. McKenney: * Remove restrictions on no-CBs CPUs, make RCU_FAST_NO_HZ take advantage of numbered callbacks, do additional callback accelerations based on numbered callbacks. Posted to LKML at https://lkml.org/lkml/2013/3/18/960. * RCU documentation updates. Posted to LKML at https://lkml.org/lkml/2013/3/18/570. * Miscellaneous fixes. Posted to LKML at https://lkml.org/lkml/2013/3/18/594. Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'init')
-rw-r--r--init/Kconfig73
1 files changed, 58 insertions, 15 deletions
diff --git a/init/Kconfig b/init/Kconfig
index 5341d7232c3a..71bb9e73011a 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -578,13 +578,16 @@ config RCU_FAST_NO_HZ
depends on NO_HZ && 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.
@@ -651,7 +654,7 @@ 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
@@ -662,16 +665,56 @@ 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