Re: [PATCH 12/13] rcu/nocb: Prepare for finegrained deferred wakeup

2021-03-16 Thread Paul E. McKenney
On Tue, Mar 16, 2021 at 12:45:26PM +0100, Frederic Weisbecker wrote:
> On Mon, Mar 15, 2021 at 08:02:39PM -0700, Paul E. McKenney wrote:
> > On Tue, Feb 23, 2021 at 01:10:10AM +0100, Frederic Weisbecker wrote:
> > > Provide a way to tune the deferred wakeup level we want to perform from
> > > a safe wakeup point. Currently those sites are:
> > > 
> > > * nocb_timer
> > > * user/idle/guest entry
> > > * CPU down
> > > * softirq/rcuc
> > > 
> > > All of these sites perform the wake up for both RCU_NOCB_WAKE and
> > > RCU_NOCB_WAKE_FORCE.
> > > 
> > > In order to merge nocb_timer and nocb_bypass_timer together, we plan to
> > > add a new RCU_NOCB_WAKE_BYPASS that really want to be deferred until
> > > a timer fires so that we don't wake up the NOCB-gp kthread too early.
> > > 
> > > To prepare for that, integrate a wake up level/limit that a callsite is
> > > deemed to perform.
> > 
> > This appears to need the following in order to build for non-NOCB
> > configurations.  I will fold it in and am retesting.
> > 
> > Thanx, Paul
> > 
> > 
> > 
> > commit 55f59dd75a11455cf558fd387fbf9011017dcc8a
> > Author: Paul E. McKenney 
> > Date:   Mon Mar 15 20:00:34 2021 -0700
> > 
> > squash! rcu/nocb: Prepare for fine-grained deferred wakeup
> > 
> > [ paulmck: Fix non-NOCB rcu_nocb_need_deferred_wakeup() definition. ]
> > Signed-off-by: Paul E. McKenney 
> > 
> > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> > index 0cc7f68..dfb048e 100644
> > --- a/kernel/rcu/tree_plugin.h
> > +++ b/kernel/rcu/tree_plugin.h
> > @@ -2926,7 +2926,7 @@ static void __init 
> > rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
> >  {
> >  }
> >  
> > -static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp)
> > +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level)
> >  {
> > return false;
> >  }
> 
> Oops thanks, I missed that.

And with this, light rcutorture testing passed.  I hope to pound on it
harder later this week.

Thanx, Paul


Re: [PATCH 12/13] rcu/nocb: Prepare for finegrained deferred wakeup

2021-03-16 Thread Frederic Weisbecker
On Mon, Mar 15, 2021 at 08:02:39PM -0700, Paul E. McKenney wrote:
> On Tue, Feb 23, 2021 at 01:10:10AM +0100, Frederic Weisbecker wrote:
> > Provide a way to tune the deferred wakeup level we want to perform from
> > a safe wakeup point. Currently those sites are:
> > 
> > * nocb_timer
> > * user/idle/guest entry
> > * CPU down
> > * softirq/rcuc
> > 
> > All of these sites perform the wake up for both RCU_NOCB_WAKE and
> > RCU_NOCB_WAKE_FORCE.
> > 
> > In order to merge nocb_timer and nocb_bypass_timer together, we plan to
> > add a new RCU_NOCB_WAKE_BYPASS that really want to be deferred until
> > a timer fires so that we don't wake up the NOCB-gp kthread too early.
> > 
> > To prepare for that, integrate a wake up level/limit that a callsite is
> > deemed to perform.
> 
> This appears to need the following in order to build for non-NOCB
> configurations.  I will fold it in and am retesting.
> 
>   Thanx, Paul
> 
> 
> 
> commit 55f59dd75a11455cf558fd387fbf9011017dcc8a
> Author: Paul E. McKenney 
> Date:   Mon Mar 15 20:00:34 2021 -0700
> 
> squash! rcu/nocb: Prepare for fine-grained deferred wakeup
> 
> [ paulmck: Fix non-NOCB rcu_nocb_need_deferred_wakeup() definition. ]
> Signed-off-by: Paul E. McKenney 
> 
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index 0cc7f68..dfb048e 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -2926,7 +2926,7 @@ static void __init 
> rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
>  {
>  }
>  
> -static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp)
> +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level)
>  {
>   return false;
>  }


Oops thanks, I missed that.


Re: [PATCH 12/13] rcu/nocb: Prepare for finegrained deferred wakeup

2021-03-15 Thread Paul E. McKenney
On Tue, Feb 23, 2021 at 01:10:10AM +0100, Frederic Weisbecker wrote:
> Provide a way to tune the deferred wakeup level we want to perform from
> a safe wakeup point. Currently those sites are:
> 
> * nocb_timer
> * user/idle/guest entry
> * CPU down
> * softirq/rcuc
> 
> All of these sites perform the wake up for both RCU_NOCB_WAKE and
> RCU_NOCB_WAKE_FORCE.
> 
> In order to merge nocb_timer and nocb_bypass_timer together, we plan to
> add a new RCU_NOCB_WAKE_BYPASS that really want to be deferred until
> a timer fires so that we don't wake up the NOCB-gp kthread too early.
> 
> To prepare for that, integrate a wake up level/limit that a callsite is
> deemed to perform.

This appears to need the following in order to build for non-NOCB
configurations.  I will fold it in and am retesting.

Thanx, Paul



commit 55f59dd75a11455cf558fd387fbf9011017dcc8a
Author: Paul E. McKenney 
Date:   Mon Mar 15 20:00:34 2021 -0700

squash! rcu/nocb: Prepare for fine-grained deferred wakeup

[ paulmck: Fix non-NOCB rcu_nocb_need_deferred_wakeup() definition. ]
Signed-off-by: Paul E. McKenney 

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 0cc7f68..dfb048e 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2926,7 +2926,7 @@ static void __init rcu_boot_init_nocb_percpu_data(struct 
rcu_data *rdp)
 {
 }
 
-static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp)
+static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level)
 {
return false;
 }