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Commit c9336643 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Paul E. McKenney
Browse files

rcu: Clarify help text for RCU_BOOST_PRIO 



The old text confused real-time applications with real-time threads, so
that you pretty much needed to understand how this kernel configuration
parameter worked to understand the help text.  This commit therefore
attempts to make the help text human-readable.

Reported-by: default avatarJörn Engel <joern@purestorage.com>
Signed-off-by: default avatarPaul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent f88022a4

init/Kconfig

+19 −4
Original line number Diff line number Diff line
@@ -515,10 +515,25 @@ config RCU_BOOST_PRIO 
	depends on RCU_BOOST

	default 1

	help

	  This option specifies the real-time priority to which preempted

	  RCU readers are to be boosted.  If you are working with CPU-bound

	  real-time applications, you should specify a priority higher then

	  the highest-priority CPU-bound application.

	  This option specifies the real-time priority to which long-term

	  preempted RCU readers are to be boosted.  If you are working

	  with a real-time application that has one or more CPU-bound

	  threads running at a real-time priority level, you should set

	  RCU_BOOST_PRIO to a priority higher then the highest-priority

	  real-time CPU-bound thread.  The default RCU_BOOST_PRIO value

	  of 1 is appropriate in the common case, which is real-time

	  applications that do not have any CPU-bound threads.



	  Some real-time applications might not have a single real-time

	  thread that saturates a given CPU, but instead might have

	  multiple real-time threads that, taken together, fully utilize

	  that CPU.  In this case, you should set RCU_BOOST_PRIO to

	  a priority higher than the lowest-priority thread that is

	  conspiring to prevent the CPU from running any non-real-time

	  tasks.  For example, if one thread at priority 10 and another

	  thread at priority 5 are between themselves fully consuming

	  the CPU time on a given CPU, then RCU_BOOST_PRIO should be

	  set to priority 6 or higher.



	  Specify the real-time priority, or take the default if unsure.