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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>
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1 changed files with 4 additions and 0 deletions
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@ -1312,6 +1312,7 @@ int rcu_nocb_cpu_offload(int cpu)
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}
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}
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EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload);
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EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload);
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#ifdef CONFIG_RCU_LAZY
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static unsigned long
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static unsigned long
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lazy_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
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lazy_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
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{
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{
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@ -1360,6 +1361,7 @@ static struct shrinker lazy_rcu_shrinker = {
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.batch = 0,
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.batch = 0,
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.seeks = DEFAULT_SEEKS,
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.seeks = DEFAULT_SEEKS,
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};
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};
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#endif // #ifdef CONFIG_RCU_LAZY
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void __init rcu_init_nohz(void)
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void __init rcu_init_nohz(void)
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{
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{
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@ -1391,8 +1393,10 @@ void __init rcu_init_nohz(void)
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if (!rcu_state.nocb_is_setup)
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if (!rcu_state.nocb_is_setup)
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return;
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return;
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#ifdef CONFIG_RCU_LAZY
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if (register_shrinker(&lazy_rcu_shrinker, "rcu-lazy"))
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if (register_shrinker(&lazy_rcu_shrinker, "rcu-lazy"))
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pr_err("Failed to register lazy_rcu shrinker!\n");
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pr_err("Failed to register lazy_rcu shrinker!\n");
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#endif // #ifdef CONFIG_RCU_LAZY
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if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
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if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
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pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n");
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pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n");
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