Messages in this thread | | | Date | Thu, 18 Jan 2018 09:38:25 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] rcu: refine structure rcu_node field for rcu boost |
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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 <changcheng.liu@intel.com>
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 >
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