rcu: Update RCU_FAST_NO_HZ help text

The RCU_FAST_NO_HZ help text included a warning about overhead on large
systems, but that issue has since been resolved.  The main remaining
issue with RCU_FAST_NO_HZ is increased real-time latency.  This commit
therefore updates the help text accordingly.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2012-10-07 09:26:13 -07:00 committed by Paul E. McKenney
parent 4d9a5d4319
commit ba49df4767

View File

@ -582,14 +582,13 @@ config RCU_FAST_NO_HZ
depends on NO_HZ && SMP depends on NO_HZ && SMP
default n default n
help help
This option causes RCU to attempt to accelerate grace periods This option causes RCU to attempt to accelerate grace periods in
in order to allow CPUs to enter dynticks-idle state more order to allow CPUs to enter dynticks-idle state more quickly.
quickly. On the other hand, this option increases the overhead On the other hand, this option increases the overhead of the
of the dynticks-idle checking, particularly on systems with dynticks-idle checking, thus degrading scheduling latency.
large numbers of CPUs.
Say Y if energy efficiency is critically important, particularly Say Y if energy efficiency is critically important, and you don't
if you have relatively few CPUs. care about real-time response.
Say N if you are unsure. Say N if you are unsure.