Commit a3941517 authored by Neeraj Upadhyay's avatar Neeraj Upadhyay Committed by Paul E. McKenney
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rcu: Clarify nocb kthreads naming in RCU_NOCB_CPU config 



This commit clarifies that the "p" and the "s" in the in the RCU_NOCB_CPU
config-option description refer to the "x" in the "rcuox/N" kthread name.

Signed-off-by: default avatarNeeraj Upadhyay <neeraju@codeaurora.org>
[ paulmck: While in the area, update description and advice. ]
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent ed73860c

kernel/rcu/Kconfig

+12 −8
Original line number Diff line number Diff line
@@ -221,19 +221,23 @@ config RCU_NOCB_CPU 
	  Use this option to reduce OS jitter for aggressive HPC or

	  real-time workloads.	It can also be used to offload RCU

	  callback invocation to energy-efficient CPUs in battery-powered

	  asymmetric multiprocessors.

	  asymmetric multiprocessors.  The price of this reduced jitter

	  is that the overhead of call_rcu() increases and that some

	  workloads will incur significant increases in context-switch

	  rates.



	  This option offloads callback invocation from the set of CPUs

	  specified at boot time by the rcu_nocbs parameter.  For each

	  such CPU, a kthread ("rcuox/N") will be created to invoke

	  callbacks, where the "N" is the CPU being offloaded, and where

	  the "p" for RCU-preempt (PREEMPTION kernels) and "s" for RCU-sched

	  (!PREEMPTION kernels).  Nothing prevents this kthread from running

	  on the specified CPUs, but (1) the kthreads may be preempted

	  between each callback, and (2) affinity or cgroups can be used

	  to force the kthreads to run on whatever set of CPUs is desired.



	  Say Y here if you want to help to debug reduced OS jitter.

	  the "x" is "p" for RCU-preempt (PREEMPTION kernels) and "s" for

	  RCU-sched (!PREEMPTION kernels).  Nothing prevents this kthread

	  from running on the specified CPUs, but (1) the kthreads may be

	  preempted between each callback, and (2) affinity or cgroups can

	  be used to force the kthreads to run on whatever set of CPUs is

	  desired.



	  Say Y here if you need reduced OS jitter, despite added overhead.

	  Say N here if you are unsure.



config TASKS_TRACE_RCU_READ_MB