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rcu: Bind RCU grace-period kthreads if NO_HZ_FULL

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Currently, RCU binds the grace-period kthreads to the timekeeping
CPU only if CONFIG_NO_HZ_FULL_SYSIDLE=y.  This means that these
kthreads must be bound manually when CONFIG_NO_HZ_FULL_SYSIDLE=n and
CONFIG_NO_HZ_FULL=y: Otherwise, these kthreads will induce OS jitter on
random CPUs.  Given that we are trying to reduce the amount of manual
tweaking required to make CONFIG_NO_HZ_FULL=y work nicely, this commit
makes this binding happen when CONFIG_NO_HZ_FULL=y, even in cases where
CONFIG_NO_HZ_FULL_SYSIDLE=n.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Paul E. McKenney 2014-04-01 11:20:36 -07:00
parent 71a9b26963
commit 5057f55e54
1 changed files with 16 additions and 18 deletions
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34
kernel/rcu/tree_plugin.h
View file

@ -2595,20 +2595,6 @@ static bool is_sysidle_rcu_state(struct rcu_state *rsp)
return rsp == rcu_sysidle_state; return rsp == rcu_sysidle_state;
} }
/*
* Bind the grace-period kthread for the sysidle flavor of RCU to the
* timekeeping CPU.
*/
static void rcu_bind_gp_kthread(void)
{
int 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));
}
/* /*
* Return a delay in jiffies based on the number of CPUs, rcu_node * Return a delay in jiffies based on the number of CPUs, rcu_node
* leaf fanout, and jiffies tick rate. The idea is to allow larger * leaf fanout, and jiffies tick rate. The idea is to allow larger
@ -2819,10 +2805,6 @@ static bool is_sysidle_rcu_state(struct rcu_state *rsp)
return false; return false;
} }
static void rcu_bind_gp_kthread(void)
{
}
static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle,
unsigned long maxj) unsigned long maxj)
{ {
@ -2853,3 +2835,19 @@ static bool rcu_nohz_full_cpu(struct rcu_state *rsp)
#endif /* #ifdef CONFIG_NO_HZ_FULL */ #endif /* #ifdef CONFIG_NO_HZ_FULL */
return 0; return 0;
} }
/*
* Bind the grace-period kthread for the sysidle flavor of RCU to the
* timekeeping CPU.
*/
static void rcu_bind_gp_kthread(void)
{
#ifdef CONFIG_NO_HZ_FULL
int 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 */
}