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-rw-r--r--init/Kconfig17
1 files changed, 10 insertions, 7 deletions
diff --git a/init/Kconfig b/init/Kconfig
index 717584064a7..a3a2304fa6d 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -582,13 +582,16 @@ 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.
-
- Say Y if energy efficiency is critically important, and you don't
- care about real-time response.
+ 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 increased grace-period durations.
Say N if you are unsure.