On Thu, Jan 18, 2018 at 06:33:43PM +0800, Liu, Changcheng wrote:
> Do not allocate space for rcu boost field when
> RCU BOOST is not configured.
>
> Signed-off-by: Liu Changcheng <[email protected]>
The added #ifdef in rcu_read_unlock_special() is a deal-breaker.
Just out of curiosity, is this decrease in storage measurable at
the system level?
Thanx, Paul
> diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
> index 46a5d19..88f087e 100644
> --- a/kernel/rcu/tree.h
> +++ b/kernel/rcu/tree.h
> @@ -129,6 +129,7 @@ struct rcu_node {
> /* if there is no such task. If there */
> /* is no current expedited grace period, */
> /* then there can cannot be any such task. */
> +#ifdef CONFIG_RCU_BOOST
> struct list_head *boost_tasks;
> /* Pointer to first task that needs to be */
> /* priority boosted, or NULL if no priority */
> @@ -153,6 +154,8 @@ struct rcu_node {
> /* Number of tasks boosted for expedited GP. */
> unsigned long n_normal_boosts;
> /* Number of tasks boosted for normal GP. */
> +#endif/* #ifdef CONFIG_RCU_BOOST*/
> +
> #ifdef CONFIG_RCU_NOCB_CPU
> struct swait_queue_head nocb_gp_wq[2];
> /* Place for rcu_nocb_kthread() to wait GP. */
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index db85ca3..fee0b1e 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -506,8 +506,10 @@ void rcu_read_unlock_special(struct task_struct *t)
> if (IS_ENABLED(CONFIG_RCU_BOOST)) {
> /* Snapshot ->boost_mtx ownership w/rnp->lock held. */
> drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t;
> +#ifdef CONFIG_RCU_BOOST
> if (&t->rcu_node_entry == rnp->boost_tasks)
> rnp->boost_tasks = np;
> +#endif
> }
>
> /*
> --
> 2.7.4
>
