From 21871d7eff2c96ae67e18e00adf59d56940e2fcc Mon Sep 17 00:00:00 2001 From: Clark Williams Date: Fri, 12 Sep 2014 21:21:09 -0500 Subject: 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 [ paulmck: Ported to rcu/dev, applied Paul Bolle and Peter Zijlstra feedback. ] Signed-off-by: Paul E. McKenney --- init/Kconfig | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) (limited to 'init') diff --git a/init/Kconfig b/init/Kconfig index 0c9546ba56e8..15c299cc7c1e 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -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. -config RCU_BOOST_PRIO - int "Real-time priority to boost RCU readers to" +config RCU_KTHREAD_PRIO + int "Real-time priority to use for RCU worker threads" range 1 99 depends on RCU_BOOST default 1 help - 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. -- cgit v1.2.3