|author||Clark Williams <email@example.com>||2014-09-12 21:21:09 -0500|
|committer||Paul E. McKenney <firstname.lastname@example.org>||2014-10-29 10:19:41 -0700|
rcu: Unify boost and kthread priorities
Rename CONFIG_RCU_BOOST_PRIO to CONFIG_RCU_KTHREAD_PRIO and use this value for both the per-CPU kthreads (rcuc/N) and the rcu boosting threads (rcub/n). Also, create the module_parameter rcutree.kthread_prio to be used on the kernel command line at boot to set a new value (rcutree.kthread_prio=N). Signed-off-by: Clark Williams <email@example.com> [ paulmck: Ported to rcu/dev, applied Paul Bolle and Peter Zijlstra feedback. ] Signed-off-by: Paul E. McKenney <firstname.lastname@example.org>
Diffstat (limited to 'init/Kconfig')
1 files changed, 12 insertions, 11 deletions
diff --git a/init/Kconfig b/init/Kconfig
index 0c9546ba56e8..15c299cc7c1e 100644
@@ -672,30 +672,31 @@ config RCU_BOOST
Say Y here if you are working with real-time apps or heavy loads
Say N here if you are unsure.
- int "Real-time priority to boost RCU readers to"
+ int "Real-time priority to use for RCU worker threads"
range 1 99
depends on RCU_BOOST
- This option specifies the real-time priority to which long-term
- preempted RCU readers are to be boosted. If you are working
- with a real-time application that has one or more CPU-bound
- threads running at a real-time priority level, you should set
- RCU_BOOST_PRIO to a priority higher then the highest-priority
- real-time CPU-bound thread. The default RCU_BOOST_PRIO value
- of 1 is appropriate in the common case, which is real-time
+ This option specifies the SCHED_FIFO priority value that will be
+ assigned to the rcuc/n and rcub/n threads and is also the value
+ used for RCU_BOOST (if enabled). If you are working with a
+ real-time application that has one or more CPU-bound threads
+ running at a real-time priority level, you should set
+ RCU_KTHREAD_PRIO to a priority higher than the highest-priority
+ real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
+ value of 1 is appropriate in the common case, which is real-time
applications that do not have any CPU-bound threads.
Some real-time applications might not have a single real-time
thread that saturates a given CPU, but instead might have
multiple real-time threads that, taken together, fully utilize
- that CPU. In this case, you should set RCU_BOOST_PRIO to
+ that CPU. In this case, you should set RCU_KTHREAD_PRIO to
a priority higher than the lowest-priority thread that is
conspiring to prevent the CPU from running any non-real-time
tasks. For example, if one thread at priority 10 and another
thread at priority 5 are between themselves fully consuming
- the CPU time on a given CPU, then RCU_BOOST_PRIO should be
+ the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
set to priority 6 or higher.
Specify the real-time priority, or take the default if unsure.