aboutsummaryrefslogtreecommitdiff
path: root/init
diff options
context:
space:
mode:
authorIngo Molnar <mingo@kernel.org>2012-12-03 06:27:05 +0100
committerIngo Molnar <mingo@kernel.org>2012-12-03 06:27:05 +0100
commit630e1e0bcddfda9566462d4f9a0d58b31c29d467 (patch)
treeb09a28cf7b9ff0fee53af2245a7e3f8d006ae091 /init
parent7e5530af11be68f3109672aed59243f82e1272f0 (diff)
parent91d1aa43d30505b0b825db8898ffc80a8eca96c7 (diff)
downloadlinaro-lsk-630e1e0bcddfda9566462d4f9a0d58b31c29d467.tar.gz
Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu
Conflicts: arch/x86/kernel/ptrace.c Pull the latest RCU tree from Paul E. McKenney: " The major features of this series are: 1. A first version of no-callbacks CPUs. This version prohibits offlining CPU 0, but only when enabled via CONFIG_RCU_NOCB_CPU=y. Relaxing this constraint is in progress, but not yet ready for prime time. These commits were posted to LKML at https://lkml.org/lkml/2012/10/30/724, and are at branch rcu/nocb. 2. Changes to SRCU that allows statically initialized srcu_struct structures. These commits were posted to LKML at https://lkml.org/lkml/2012/10/30/296, and are at branch rcu/srcu. 3. Restructuring of RCU's debugfs output. These commits were posted to LKML at https://lkml.org/lkml/2012/10/30/341, and are at branch rcu/tracing. 4. Additional CPU-hotplug/RCU improvements, posted to LKML at https://lkml.org/lkml/2012/10/30/327, and are at branch rcu/hotplug. Note that the commit eliminating __stop_machine() was judged to be too-high of risk, so is deferred to 3.9. 5. Changes to RCU's idle interface, most notably a new module parameter that redirects normal grace-period operations to their expedited equivalents. These were posted to LKML at https://lkml.org/lkml/2012/10/30/739, and are at branch rcu/idle. 6. Additional diagnostics for RCU's CPU stall warning facility, posted to LKML at https://lkml.org/lkml/2012/10/30/315, and are at branch rcu/stall. The most notable change reduces the default RCU CPU stall-warning time from 60 seconds to 21 seconds, so that it once again happens sooner than the softlockup timeout. 7. Documentation updates, which were posted to LKML at https://lkml.org/lkml/2012/10/30/280, and are at branch rcu/doc. A couple of late-breaking changes were posted at https://lkml.org/lkml/2012/11/16/634 and https://lkml.org/lkml/2012/11/16/547. 8. Miscellaneous fixes, which were posted to LKML at https://lkml.org/lkml/2012/10/30/309, along with a late-breaking change posted at Fri, 16 Nov 2012 11:26:25 -0800 with message-ID <20121116192625.GA447@linux.vnet.ibm.com>, but which lkml.org seems to have missed. These are at branch rcu/fixes. 9. Finally, a fix for an lockdep-RCU splat was posted to LKML at https://lkml.org/lkml/2012/11/7/486. This is at rcu/next. " Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'init')
-rw-r--r--init/Kconfig67
1 files changed, 44 insertions, 23 deletions
diff --git a/init/Kconfig b/init/Kconfig
index 6fdd6e33932..2054e048bb9 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -486,35 +486,35 @@ config PREEMPT_RCU
This option enables preemptible-RCU code that is common between
the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
+config CONTEXT_TRACKING
+ bool
+
config RCU_USER_QS
bool "Consider userspace as in RCU extended quiescent state"
- depends on HAVE_RCU_USER_QS && SMP
+ depends on HAVE_CONTEXT_TRACKING && SMP
+ select CONTEXT_TRACKING
help
This option sets hooks on kernel / userspace boundaries and
puts RCU in extended quiescent state when the CPU runs in
userspace. It means that when a CPU runs in userspace, it is
excluded from the global RCU state machine and thus doesn't
- to keep the timer tick on for RCU.
+ try to keep the timer tick on for RCU.
Unless you want to hack and help the development of the full
- tickless feature, you shouldn't enable this option. It adds
- unnecessary overhead.
+ dynticks mode, you shouldn't enable this option. It also
+ adds unnecessary overhead.
If unsure say N
-config RCU_USER_QS_FORCE
- bool "Force userspace extended QS by default"
- depends on RCU_USER_QS
+config CONTEXT_TRACKING_FORCE
+ bool "Force context tracking"
+ depends on CONTEXT_TRACKING
help
- Set the hooks in user/kernel boundaries by default in order to
- test this feature that treats userspace as an extended quiescent
- state until we have a real user like a full adaptive nohz option.
-
- Unless you want to hack and help the development of the full
- tickless feature, you shouldn't enable this option. It adds
- unnecessary overhead.
-
- If unsure say N
+ Probe on user/kernel boundaries by default in order to
+ test the features that rely on it such as userspace RCU extended
+ quiescent states.
+ This test is there for debugging until we have a real user like the
+ full dynticks mode.
config RCU_FANOUT
int "Tree-based hierarchical RCU fanout value"
@@ -582,14 +582,13 @@ 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, particularly on systems with
- large numbers of CPUs.
+ 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.
- Say Y if energy efficiency is critically important, particularly
- if you have relatively few CPUs.
+ Say Y if energy efficiency is critically important, and you don't
+ care about real-time response.
Say N if you are unsure.
@@ -655,6 +654,28 @@ config RCU_BOOST_DELAY
Accept the default if unsure.
+config RCU_NOCB_CPU
+ bool "Offload RCU callback processing from boot-selected CPUs"
+ depends on TREE_RCU || TREE_PREEMPT_RCU
+ default n
+ help
+ Use this option to reduce OS jitter for aggressive HPC or
+ real-time workloads. It can also be used to offload RCU
+ callback invocation to energy-efficient CPUs in battery-powered
+ asymmetric multiprocessors.
+
+ 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.
+ Say N here if you are unsure.
+
endmenu # "RCU Subsystem"
config IKCONFIG