tree da592215d7ebbd15cdb0773770cd45ed91c538d2
parent fbce7497ee5af800a1c350c73f3c3f103cb27a15
author Paul E. McKenney <paulmck@linux.vnet.ibm.com> 1404321204 -0700
committer Paul E. McKenney <paulmck@linux.vnet.ibm.com> 1404771224 -0700

rcu: Don't offload callbacks unless specifically requested

Enabling NO_HZ_FULL currently has the side effect of enabling callback
offloading on all CPUs.  This results in lots of additional rcuo kthreads,
and can also increase context switching and wakeups, even in cases where
callback offloading is neither needed nor particularly desirable.  This
commit therefore enables callback offloading on a given CPU only if
specifically requested at build time or boot time, or if that CPU has
been specifically designated (again, either at build time or boot time)
as a nohz_full CPU.

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