rcu: Remove the RCU_FAST_NO_HZ Kconfig option

All of the uses of CONFIG_RCU_FAST_NO_HZ=y that I have seen involve
systems with RCU callbacks offloaded.  In this situation, all that this
Kconfig option does is slow down idle entry/exit with an additional
allways-taken early exit.  If this is the only use case, then this
Kconfig option nothing but an attractive nuisance that needs to go away.

This commit therefore removes the RCU_FAST_NO_HZ Kconfig option.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney
2021-09-27 14:18:51 -07:00
parent 24eab6e1ff
commit e2c73a6860
11 changed files with 7 additions and 269 deletions

View File

@@ -15,7 +15,6 @@ CONFIG_PROVE_RCU -- Hardwired to CONFIG_PROVE_LOCKING.
CONFIG_RCU_BOOST -- one of PREEMPT_RCU.
CONFIG_RCU_FANOUT -- Cover hierarchy, but overlap with others.
CONFIG_RCU_FANOUT_LEAF -- Do one non-default.
CONFIG_RCU_FAST_NO_HZ -- Do one, but not with all nohz_full CPUs.
CONFIG_RCU_NOCB_CPU -- Do three, one with no rcu_nocbs CPUs, one with
rcu_nocbs=0, and one with all rcu_nocbs CPUs.
CONFIG_RCU_TRACE -- Do half.