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rcu: Register rcu-lazy shrinker only for CONFIG_RCU_LAZY=y kernels 

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@intel.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
This commit is contained in:
Zqiang 2023-01-30 15:17:37 +08:00 committed by Joel Fernandes (Google)
parent db7b464df9
commit 2450b78e0b
1 changed files with 4 additions and 0 deletions
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4
kernel/rcu/tree_nocb.h
View File

@ -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");