CONFIG_NO_HZ_FULL may be enabled widely on distros nowadays but actual users should be a tiny minority, if actually any.
Also there is a risk that affining the GP kthread to a single CPU could end up noticeably reducing RCU performances and increasing energy consumption. So lets affine the GP kthread only when nohz full is actually used (ie: when the nohz_full= parameter is filled or CONFIG_NO_HZ_FULL_ALL=y) Signed-off-by: Frederic Weisbecker <fweis...@gmail.com> Cc: Josh Triplett <j...@joshtriplett.org> Cc: Steven Rostedt <rost...@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoy...@efficios.com> --- kernel/rcu/tree_plugin.h | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index cbc2c45..726f52c 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2843,12 +2843,16 @@ static bool rcu_nohz_full_cpu(struct rcu_state *rsp) */ static void rcu_bind_gp_kthread(void) { -#ifdef CONFIG_NO_HZ_FULL - int cpu = ACCESS_ONCE(tick_do_timer_cpu); + int cpu; + + if (!tick_nohz_full_enabled()) + return; + + cpu = ACCESS_ONCE(tick_do_timer_cpu); if (cpu < 0 || cpu >= nr_cpu_ids) return; + if (raw_smp_processor_id() != cpu) set_cpus_allowed_ptr(current, cpumask_of(cpu)); -#endif /* #ifdef CONFIG_NO_HZ_FULL */ } -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/