From: Ankur Arora ankur.a.arora@oracle.com
PREEMPT_LAZY can be enabled stand-alone or alongside PREEMPT_DYNAMIC which allows for dynamic switching of preemption models.
The choice of PREEMPT_RCU or not, however, is fixed at compile time.
Given that PREEMPT_RCU makes some trade-offs to optimize for latency as opposed to throughput, configurations with limited preemption might prefer the stronger forward-progress guarantees of PREEMPT_RCU=n.
Accordingly, explicitly limit PREEMPT_RCU=y to the latency oriented preemption models: PREEMPT, PREEMPT_RT, and the runtime configurable model PREEMPT_DYNAMIC.
This means the throughput oriented models, PREEMPT_NONE, PREEMPT_VOLUNTARY, and PREEMPT_LAZY will run with PREEMPT_RCU=n.
Cc: Paul E. McKenney paulmck@kernel.org Cc: Peter Zijlstra peterz@infradead.org Reviewed-by: Frederic Weisbecker frederic@kernel.org Signed-off-by: Ankur Arora ankur.a.arora@oracle.com Signed-off-by: Paul E. McKenney paulmck@kernel.org Signed-off-by: Boqun Feng boqun.feng@gmail.com --- kernel/rcu/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig index e2206f3a070c..dd6251678e99 100644 --- a/kernel/rcu/Kconfig +++ b/kernel/rcu/Kconfig @@ -18,7 +18,7 @@ config TREE_RCU
config PREEMPT_RCU bool - default y if PREEMPTION + default y if (PREEMPT || PREEMPT_RT || PREEMPT_DYNAMIC) select TREE_RCU help This option selects the RCU implementation that is