* rcu: enable rcu_normal_after_boot by default for RT
@ 2018-11-01 23:02 Paul E. McKenney
2018-11-08 15:52 ` Sebastian Andrzej Siewior
0 siblings, 1 reply; 3+ messages in thread
From: Paul E. McKenney @ 2018-11-01 23:02 UTC (permalink / raw)
To: lcapitulino, julia, bigeasy; +Cc: linux-rt-users, linux-kernel
> The forcing of an expedited grace period is an expensive and very
> RT-application unfriendly operation, as it forcibly preempts all running
> tasks on CPUs which are preventing the gp from expiring.
>
> By default, as a policy decision, disable the expediting of grace
> periods (after boot) on configurations which enable PREEMPT_RT_FULL.
>
> Suggested-by: Luiz Capitulino <lcapitulino@redhat.com>
> Signed-off-by: Julia Cartwright <julia@ni.com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
In case it matters:
Acked-by: Paul E. McKenney <paulmck@linux.ibm.com>
Alternatively, any reason that I should not pull this into -rcu?
Thanx, Paul
> diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
> index f56c0fbdf22e..12027723abaf 100644
> --- a/kernel/rcu/update.c
> +++ b/kernel/rcu/update.c
> @@ -67,7 +67,7 @@ extern int rcu_expedited; /* from sysctl */
> module_param(rcu_expedited, int, 0);
> extern int rcu_normal; /* from sysctl */
> module_param(rcu_normal, int, 0);
> -static int rcu_normal_after_boot;
> +static int rcu_normal_after_boot = IS_ENABLED(CONFIG_PREEMPT_RT_FULL);
> module_param(rcu_normal_after_boot, int, 0);
> #endif /* #ifndef CONFIG_TINY_RCU */
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: rcu: enable rcu_normal_after_boot by default for RT
2018-11-01 23:02 rcu: enable rcu_normal_after_boot by default for RT Paul E. McKenney
@ 2018-11-08 15:52 ` Sebastian Andrzej Siewior
2018-11-08 16:12 ` Paul E. McKenney
0 siblings, 1 reply; 3+ messages in thread
From: Sebastian Andrzej Siewior @ 2018-11-08 15:52 UTC (permalink / raw)
To: Paul E. McKenney; +Cc: lcapitulino, julia, linux-rt-users, linux-kernel
On 2018-11-01 16:02:35 [-0700], Paul E. McKenney wrote:
> > The forcing of an expedited grace period is an expensive and very
> > RT-application unfriendly operation, as it forcibly preempts all running
> > tasks on CPUs which are preventing the gp from expiring.
> >
> > By default, as a policy decision, disable the expediting of grace
> > periods (after boot) on configurations which enable PREEMPT_RT_FULL.
> >
> > Suggested-by: Luiz Capitulino <lcapitulino@redhat.com>
> > Signed-off-by: Julia Cartwright <julia@ni.com>
> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>
> In case it matters:
>
> Acked-by: Paul E. McKenney <paulmck@linux.ibm.com>
>
> Alternatively, any reason that I should not pull this into -rcu?
because we don't have CONFIG_PREEMPT_RT_FULL yet.
> Thanx, Paul
Sebastian
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: rcu: enable rcu_normal_after_boot by default for RT
2018-11-08 15:52 ` Sebastian Andrzej Siewior
@ 2018-11-08 16:12 ` Paul E. McKenney
0 siblings, 0 replies; 3+ messages in thread
From: Paul E. McKenney @ 2018-11-08 16:12 UTC (permalink / raw)
To: Sebastian Andrzej Siewior
Cc: lcapitulino, julia, linux-rt-users, linux-kernel
On Thu, Nov 08, 2018 at 04:52:26PM +0100, Sebastian Andrzej Siewior wrote:
> On 2018-11-01 16:02:35 [-0700], Paul E. McKenney wrote:
> > > The forcing of an expedited grace period is an expensive and very
> > > RT-application unfriendly operation, as it forcibly preempts all running
> > > tasks on CPUs which are preventing the gp from expiring.
> > >
> > > By default, as a policy decision, disable the expediting of grace
> > > periods (after boot) on configurations which enable PREEMPT_RT_FULL.
> > >
> > > Suggested-by: Luiz Capitulino <lcapitulino@redhat.com>
> > > Signed-off-by: Julia Cartwright <julia@ni.com>
> > > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> >
> > In case it matters:
> >
> > Acked-by: Paul E. McKenney <paulmck@linux.ibm.com>
> >
> > Alternatively, any reason that I should not pull this into -rcu?
> because we don't have CONFIG_PREEMPT_RT_FULL yet.
Fair enough. This particular case works without CONFIG_PREEMPT_RT_FULL
defined, but up to you guys.
Thanx, Paul
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-11-01 23:02 rcu: enable rcu_normal_after_boot by default for RT Paul E. McKenney
2018-11-08 15:52 ` Sebastian Andrzej Siewior
2018-11-08 16:12 ` Paul E. McKenney
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