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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-07-02 10:13:24 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-07-07 15:13:44 -0700
commitb58cc46c5f6b57f1c814e374dbc47176e6b4938e (patch)
treeda592215d7ebbd15cdb0773770cd45ed91c538d2 /kernel
parentfbce7497ee5af800a1c350c73f3c3f103cb27a15 (diff)
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/rcu/tree_plugin.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index b27b86c7bbfa..17eed0856b03 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2473,6 +2473,9 @@ static void __init rcu_spawn_nocb_kthreads(struct rcu_state *rsp)
if (rcu_nocb_mask == NULL)
return;
+#ifdef CONFIG_NO_HZ_FULL
+ cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask);
+#endif /* #ifdef CONFIG_NO_HZ_FULL */
if (ls == -1) {
ls = int_sqrt(nr_cpu_ids);
rcu_nocb_leader_stride = ls;