tree 1c985777f8639c43bf82e917e6286860864b8dc1
parent f417d2b3f060864ee8fd187b0145288fb95515e8
author Paul E. McKenney <paulmck@linux.vnet.ibm.com> 1345437353 -0700
committer Paul E. McKenney <paulmck@linux.vnet.ibm.com> 1348075832 -0700

rcu: Add callback-free CPUs

RCU callback execution can add significant OS jitter and also can degrade
scheduling latency.  This commit therefore adds the ability for selected
CPUs ("rcu_nocbs=" boot parameter) to have their callbacks offloaded to
kthreads.  If the "rcu_nocb_poll" boot parameter is also specified, these
kthreads will do polling, removing the need for the offloaded CPUs to do
wakeups.  At least one CPU must be doing normal callback processing:
currently CPU 0 cannot be selected as a no-CBs CPU.  In addition, attempts
to offline the last normal-CBs CPU will fail.

This feature was inspired by Jim Houston's and Joe Korty's JRCU.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>