From: Zqiang <qiang1.zhang@xxxxxxxxx>
The lazy_rcu_shrink_count() shrinker function is registered even in
kernels built with CONFIG_RCU_LAZY=n, in which case this function
uselessly consumes cycles learning that no CPU has any lazy callbacks
queued.
This commit therefore registers this shrinker function only in the kernels
built with CONFIG_RCU_LAZY=y, where it might actually do something useful.
Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree_nocb.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index 9e1c8caec5ce..f2280616f9d5 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -1312,6 +1312,7 @@ int rcu_nocb_cpu_offload(int cpu)
}
EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload);
+#ifdef CONFIG_RCU_LAZY
static unsigned long
lazy_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
{
@@ -1360,6 +1361,7 @@ static struct shrinker lazy_rcu_shrinker = {
.batch = 0,
.seeks = DEFAULT_SEEKS,
};
+#endif // #ifdef CONFIG_RCU_LAZY
void __init rcu_init_nohz(void)
{
@@ -1391,8 +1393,10 @@ void __init rcu_init_nohz(void)
if (!rcu_state.nocb_is_setup)
return;
+#ifdef CONFIG_RCU_LAZY
if (register_shrinker(&lazy_rcu_shrinker, "rcu-lazy"))
pr_err("Failed to register lazy_rcu shrinker!\n");
+#endif // #ifdef CONFIG_RCU_LAZY
if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n");
--
2.40.0.rc1.284.g88254d51c5-goog
