2020-06-04 10:41:02

by peter enderborg

Subject: [PATCH] rcu: Stop shrinker loop

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 <[email protected]>
---
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

2020-06-04 13:45:53

by Uladzislau Rezki

Subject: Re: [PATCH] rcu: Stop shrinker loop

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 <[email protected]>
> ---
> 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) <[email protected]>

--
Vlad Rezki

2020-06-04 18:54:14

by Paul E. McKenney

Subject: Re: [PATCH] rcu: Stop shrinker loop

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 <[email protected]>
> > ---
> > 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) <[email protected]>

Queued, thank you both!

Thanx, Paul

2020-06-04 19:13:50

by Uladzislau Rezki

Subject: Re: [PATCH] rcu: Stop shrinker loop

> 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 <[email protected]>
> > > ---
> > > 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) <[email protected]>
>
> Queued, thank you both!
>
Thank you, Paul!

--
Vlad Rezki