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rcu: Clarify RCU_LAZY and RCU_LAZY_DEFAULT_OFF help text

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This commit wordsmiths the RCU_LAZY and RCU_LAZY_DEFAULT_OFF Kconfig
options' help text.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
This commit is contained in:
Paul E. McKenney 2025-01-08 19:50:37 -08:00 committed by Boqun Feng
parent 053ca72554
commit 81a208c56e
1 changed files with 13 additions and 7 deletions
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20
kernel/rcu/Kconfig
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@ -323,21 +323,27 @@ config RCU_LAZY
depends on RCU_NOCB_CPU
default n
help
To save power, batch RCU callbacks and flush after delay, memory
pressure, or callback list growing too big.
To save power, batch RCU callbacks and delay starting the
corresponding grace period for multiple seconds. The grace
period will be started after this delay, in case of memory
pressure, or if the corresponding CPU's callback list grows
too large.
Requires rcu_nocbs=all to be set.
These delays happen only on rcu_nocbs CPUs, that is, CPUs
whose callbacks have been offloaded.
Use rcutree.enable_rcu_lazy=0 to turn it off at boot time.
Use the rcutree.enable_rcu_lazy=0 kernel-boot parameter to
globally disable these delays.
config RCU_LAZY_DEFAULT_OFF
bool "Turn RCU lazy invocation off by default"
depends on RCU_LAZY
default n
help
Allows building the kernel with CONFIG_RCU_LAZY=y yet keep it default
off. Boot time param rcutree.enable_rcu_lazy=1 can be used to switch
it back on.
Build the kernel with CONFIG_RCU_LAZY=y, but cause the kernel
to boot with these energy-efficiency delays disabled. Use the
rcutree.enable_rcu_lazy=0 kernel-boot parameter to override
the this option at boot time, thus re-enabling these delays.
config RCU_DOUBLE_CHECK_CB_TIME
bool "RCU callback-batch backup time check"