From 2450b78e0bb1e034eaa2a33dca689282bd8c892a Mon Sep 17 00:00:00 2001 From: Zqiang Date: Mon, 30 Jan 2023 15:17:37 +0800 Subject: [PATCH] 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 Reviewed-by: Frederic Weisbecker Reviewed-by: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney Signed-off-by: Joel Fernandes (Google) --- 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");