Commit db4cb768 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

doc: Remove obsolete kernel-per-CPU-kthreads RCU_FAST_NO_HZ advice 



This document advises building with both CONFIG_NO_HZ=y and
CONFIG_RCU_FAST_NO_HZ=y.  However, CONFIG_NO_HZ=y offloads callbacks from
all nohz_full CPUs, and CPUs with offloaded callbacks do not benefit from
CONFIG_RCU_FAST_NO_HZ=y.  Quite the opposite: CONFIG_RCU_FAST_NO_HZ=y
simply adds a bit of idle entry/exit overhead.

This commit therefore changes that advice to only CONFIG_NO_HZ=y.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 8c0abfd6

Documentation/admin-guide/kernel-per-CPU-kthreads.rst

+1 −1
Original line number Original line Diff line number Diff line
@@ -208,7 +208,7 @@ Do at least one of the following: 
2.	Enable RCU to do its processing remotely via dyntick-idle by

2.	Enable RCU to do its processing remotely via dyntick-idle by

	doing all of the following:

	doing all of the following:





	a.	Build with CONFIG_NO_HZ=y and CONFIG_RCU_FAST_NO_HZ=y.

	a.	Build with CONFIG_NO_HZ=y.

	b.	Ensure that the CPU goes idle frequently, allowing other

	b.	Ensure that the CPU goes idle frequently, allowing other

		CPUs to detect that it has passed through an RCU quiescent

		CPUs to detect that it has passed through an RCU quiescent

		state.	If the kernel is built with CONFIG_NO_HZ_FULL=y,

		state.	If the kernel is built with CONFIG_NO_HZ_FULL=y,