[PATCH] rcu: Stop shrinker loop

[PATCH] rcu: Stop shrinker loop

[Peter Enderborg]

The count and scan can be separated in time. It is a fair chance
that all work is already done when the scan starts. It
then might retry. This is can be avoided with returning SHRINK_STOP.

Signed-off-by: Peter Enderborg <peter.enderborg@sony.com>
---
 kernel/rcu/tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index c716eadc7617..8b36c6b2887d 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3310,7 +3310,7 @@ kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 			break;
 	}
 
-	return freed;
+	return freed == 0 ? SHRINK_STOP : freed;
 }
 
 static struct shrinker kfree_rcu_shrinker = {
-- 
2.17.1

Re: [PATCH] rcu: Stop shrinker loop

[Uladzislau Rezki]

On Thu, Jun 04, 2020 at 12:23:20PM +0200, Peter Enderborg wrote:
> The count and scan can be separated in time. It is a fair chance
> that all work is already done when the scan starts. It
> then might retry. This is can be avoided with returning SHRINK_STOP.
> 
> Signed-off-by: Peter Enderborg <peter.enderborg@sony.com>
> ---
>  kernel/rcu/tree.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index c716eadc7617..8b36c6b2887d 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3310,7 +3310,7 @@ kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
>  			break;
>  	}
>  
> -	return freed;
> +	return freed == 0 ? SHRINK_STOP : freed;
>  }
>  
The loop will be stopped anyway sooner or later, but sooner is better :)
To me that change makes sense.

Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

--
Vlad Rezki

Re: [PATCH] rcu: Stop shrinker loop

[Paul E. McKenney]

On Thu, Jun 04, 2020 at 03:42:55PM +0200, Uladzislau Rezki wrote:
> On Thu, Jun 04, 2020 at 12:23:20PM +0200, Peter Enderborg wrote:
> > The count and scan can be separated in time. It is a fair chance
> > that all work is already done when the scan starts. It
> > then might retry. This is can be avoided with returning SHRINK_STOP.
> > 
> > Signed-off-by: Peter Enderborg <peter.enderborg@sony.com>
> > ---
> >  kernel/rcu/tree.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index c716eadc7617..8b36c6b2887d 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -3310,7 +3310,7 @@ kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
> >  			break;
> >  	}
> >  
> > -	return freed;
> > +	return freed == 0 ? SHRINK_STOP : freed;
> >  }
> >  
> The loop will be stopped anyway sooner or later, but sooner is better :)
> To me that change makes sense.
> 
> Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

Queued, thank you both!

							Thanx, Paul

Re: [PATCH] rcu: Stop shrinker loop

[Uladzislau Rezki]

> On Thu, Jun 04, 2020 at 03:42:55PM +0200, Uladzislau Rezki wrote:
> > On Thu, Jun 04, 2020 at 12:23:20PM +0200, Peter Enderborg wrote:
> > > The count and scan can be separated in time. It is a fair chance
> > > that all work is already done when the scan starts. It
> > > then might retry. This is can be avoided with returning SHRINK_STOP.
> > > 
> > > Signed-off-by: Peter Enderborg <peter.enderborg@sony.com>
> > > ---
> > >  kernel/rcu/tree.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > > index c716eadc7617..8b36c6b2887d 100644
> > > --- a/kernel/rcu/tree.c
> > > +++ b/kernel/rcu/tree.c
> > > @@ -3310,7 +3310,7 @@ kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
> > >  			break;
> > >  	}
> > >  
> > > -	return freed;
> > > +	return freed == 0 ? SHRINK_STOP : freed;
> > >  }
> > >  
> > The loop will be stopped anyway sooner or later, but sooner is better :)
> > To me that change makes sense.
> > 
> > Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> 
> Queued, thank you both!
> 
Thank you, Paul!

--
Vlad Rezki