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rcu: Force per-rcu_node kthreads off of the outgoing CPU

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The scheduler has had some heartburn in the past when too many real-time
kthreads were affinitied to the outgoing CPU.  So, this commit lightens
the load by forcing the per-rcu_node and the boost kthreads off of the
outgoing CPU.  Note that RCU's per-CPU kthread remains on the outgoing
CPU until the bitter end, as it must in order to preserve correctness.

Also avoid disabling hardirqs across calls to set_cpus_allowed_ptr(),
given that this function can block.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
2011-04-14 12:13:53 -07:00
committed by Paul E. McKenney
parent 27f4d28057
commit 0f962a5e72
2 changed files with 24 additions and 8 deletions
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8
kernel/rcutree_plugin.h
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@@ -1212,17 +1212,19 @@ static void rcu_initiate_boost(struct rcu_node *rnp)
}
}
/*
* Set the affinity of the boost kthread. The CPU-hotplug locks are
* held, so no one should be messing with the existence of the boost
* kthread.
*/
static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp,
cpumask_var_t cm)
{
unsigned long flags;
struct task_struct *t;
raw_spin_lock_irqsave(&rnp->lock, flags);
t = rnp->boost_kthread_task;
if (t != NULL)
set_cpus_allowed_ptr(rnp->boost_kthread_task, cm);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
#define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000)