diff mbox series

[v8,05/13] mm: vmscan: use kvfree_rcu instead of call_rcu

Message ID 20210217001322.2226796-6-shy828301@gmail.com (mailing list archive)
State New
Headers show
Series Make shrinker's nr_deferred memcg aware | expand

Commit Message

Yang Shi Feb. 17, 2021, 12:13 a.m. UTC
Using kvfree_rcu() to free the old shrinker_maps instead of call_rcu().
We don't have to define a dedicated callback for call_rcu() anymore.

Signed-off-by: Yang Shi <shy828301@gmail.com>
---
 mm/vmscan.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

Comments

Roman Gushchin Feb. 17, 2021, 1:59 a.m. UTC | #1
On Tue, Feb 16, 2021 at 04:13:14PM -0800, Yang Shi wrote:
> Using kvfree_rcu() to free the old shrinker_maps instead of call_rcu().
> We don't have to define a dedicated callback for call_rcu() anymore.
> 
> Signed-off-by: Yang Shi <shy828301@gmail.com>

Acked-by: Roman Gushchin <guro@fb.com>

Thanks!

> ---
>  mm/vmscan.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 2e753c2516fa..c2a309acd86b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -192,11 +192,6 @@ static inline int shrinker_map_size(int nr_items)
>  	return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
>  }
>  
> -static void free_shrinker_map_rcu(struct rcu_head *head)
> -{
> -	kvfree(container_of(head, struct memcg_shrinker_map, rcu));
> -}
> -
>  static int expand_one_shrinker_map(struct mem_cgroup *memcg,
>  				   int size, int old_size)
>  {
> @@ -219,7 +214,7 @@ static int expand_one_shrinker_map(struct mem_cgroup *memcg,
>  		memset((void *)new->map + old_size, 0, size - old_size);
>  
>  		rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new);
> -		call_rcu(&old->rcu, free_shrinker_map_rcu);
> +		kvfree_rcu(old);
>  	}
>  
>  	return 0;
> -- 
> 2.26.2
>
Kirill Tkhai Feb. 17, 2021, 6:25 a.m. UTC | #2
On 17.02.2021 03:13, Yang Shi wrote:
> Using kvfree_rcu() to free the old shrinker_maps instead of call_rcu().
> We don't have to define a dedicated callback for call_rcu() anymore.
> 
> Signed-off-by: Yang Shi <shy828301@gmail.com>

Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com>

> ---
>  mm/vmscan.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 2e753c2516fa..c2a309acd86b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -192,11 +192,6 @@ static inline int shrinker_map_size(int nr_items)
>  	return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
>  }
>  
> -static void free_shrinker_map_rcu(struct rcu_head *head)
> -{
> -	kvfree(container_of(head, struct memcg_shrinker_map, rcu));
> -}
> -
>  static int expand_one_shrinker_map(struct mem_cgroup *memcg,
>  				   int size, int old_size)
>  {
> @@ -219,7 +214,7 @@ static int expand_one_shrinker_map(struct mem_cgroup *memcg,
>  		memset((void *)new->map + old_size, 0, size - old_size);
>  
>  		rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new);
> -		call_rcu(&old->rcu, free_shrinker_map_rcu);
> +		kvfree_rcu(old);
>  	}
>  
>  	return 0;
>
Shakeel Butt March 8, 2021, 6:13 a.m. UTC | #3
On Tue, Feb 16, 2021 at 4:13 PM Yang Shi <shy828301@gmail.com> wrote:
>
> Using kvfree_rcu() to free the old shrinker_maps instead of call_rcu().
> We don't have to define a dedicated callback for call_rcu() anymore.
>
> Signed-off-by: Yang Shi <shy828301@gmail.com>
> ---
>  mm/vmscan.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 2e753c2516fa..c2a309acd86b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -192,11 +192,6 @@ static inline int shrinker_map_size(int nr_items)
>         return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
>  }
>
> -static void free_shrinker_map_rcu(struct rcu_head *head)
> -{
> -       kvfree(container_of(head, struct memcg_shrinker_map, rcu));
> -}
> -
>  static int expand_one_shrinker_map(struct mem_cgroup *memcg,
>                                    int size, int old_size)
>  {
> @@ -219,7 +214,7 @@ static int expand_one_shrinker_map(struct mem_cgroup *memcg,
>                 memset((void *)new->map + old_size, 0, size - old_size);
>
>                 rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new);
> -               call_rcu(&old->rcu, free_shrinker_map_rcu);
> +               kvfree_rcu(old);

Please use kvfree_rcu(old, rcu) instead of kvfree_rcu(old). The single
param can call synchronize_rcu().
Paul E. McKenney March 8, 2021, 2:54 p.m. UTC | #4
On Sun, Mar 07, 2021 at 10:13:04PM -0800, Shakeel Butt wrote:
> On Tue, Feb 16, 2021 at 4:13 PM Yang Shi <shy828301@gmail.com> wrote:
> >
> > Using kvfree_rcu() to free the old shrinker_maps instead of call_rcu().
> > We don't have to define a dedicated callback for call_rcu() anymore.
> >
> > Signed-off-by: Yang Shi <shy828301@gmail.com>
> > ---
> >  mm/vmscan.c | 7 +------
> >  1 file changed, 1 insertion(+), 6 deletions(-)
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 2e753c2516fa..c2a309acd86b 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -192,11 +192,6 @@ static inline int shrinker_map_size(int nr_items)
> >         return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
> >  }
> >
> > -static void free_shrinker_map_rcu(struct rcu_head *head)
> > -{
> > -       kvfree(container_of(head, struct memcg_shrinker_map, rcu));
> > -}
> > -
> >  static int expand_one_shrinker_map(struct mem_cgroup *memcg,
> >                                    int size, int old_size)
> >  {
> > @@ -219,7 +214,7 @@ static int expand_one_shrinker_map(struct mem_cgroup *memcg,
> >                 memset((void *)new->map + old_size, 0, size - old_size);
> >
> >                 rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new);
> > -               call_rcu(&old->rcu, free_shrinker_map_rcu);
> > +               kvfree_rcu(old);
> 
> Please use kvfree_rcu(old, rcu) instead of kvfree_rcu(old). The single
> param can call synchronize_rcu().

Especially given that you already have the ->rcu field that the
two-argument form requires.

The reason for using the single-argument form is when you have lots of
little data structures, such that getting rid of that rcu_head structure
is valuable enough to be worth the occasional call to synchronize_rcu().
However, please note that this call to synchronize_rcu() happens only
under OOM conditions.

							Thanx, Paul
Roman Gushchin March 8, 2021, 4:49 p.m. UTC | #5
On Sun, Mar 07, 2021 at 10:13:04PM -0800, Shakeel Butt wrote:
> On Tue, Feb 16, 2021 at 4:13 PM Yang Shi <shy828301@gmail.com> wrote:
> >
> > Using kvfree_rcu() to free the old shrinker_maps instead of call_rcu().
> > We don't have to define a dedicated callback for call_rcu() anymore.
> >
> > Signed-off-by: Yang Shi <shy828301@gmail.com>
> > ---
> >  mm/vmscan.c | 7 +------
> >  1 file changed, 1 insertion(+), 6 deletions(-)
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 2e753c2516fa..c2a309acd86b 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -192,11 +192,6 @@ static inline int shrinker_map_size(int nr_items)
> >         return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
> >  }
> >
> > -static void free_shrinker_map_rcu(struct rcu_head *head)
> > -{
> > -       kvfree(container_of(head, struct memcg_shrinker_map, rcu));
> > -}
> > -
> >  static int expand_one_shrinker_map(struct mem_cgroup *memcg,
> >                                    int size, int old_size)
> >  {
> > @@ -219,7 +214,7 @@ static int expand_one_shrinker_map(struct mem_cgroup *memcg,
> >                 memset((void *)new->map + old_size, 0, size - old_size);
> >
> >                 rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new);
> > -               call_rcu(&old->rcu, free_shrinker_map_rcu);
> > +               kvfree_rcu(old);
> 
> Please use kvfree_rcu(old, rcu) instead of kvfree_rcu(old). The single
> param can call synchronize_rcu().

Oh, I didn't know about this difference. Thank you for noticing!
Yang Shi March 8, 2021, 6:15 p.m. UTC | #6
On Mon, Mar 8, 2021 at 6:54 AM Paul E. McKenney <paulmck@kernel.org> wrote:
>
> On Sun, Mar 07, 2021 at 10:13:04PM -0800, Shakeel Butt wrote:
> > On Tue, Feb 16, 2021 at 4:13 PM Yang Shi <shy828301@gmail.com> wrote:
> > >
> > > Using kvfree_rcu() to free the old shrinker_maps instead of call_rcu().
> > > We don't have to define a dedicated callback for call_rcu() anymore.
> > >
> > > Signed-off-by: Yang Shi <shy828301@gmail.com>
> > > ---
> > >  mm/vmscan.c | 7 +------
> > >  1 file changed, 1 insertion(+), 6 deletions(-)
> > >
> > > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > > index 2e753c2516fa..c2a309acd86b 100644
> > > --- a/mm/vmscan.c
> > > +++ b/mm/vmscan.c
> > > @@ -192,11 +192,6 @@ static inline int shrinker_map_size(int nr_items)
> > >         return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
> > >  }
> > >
> > > -static void free_shrinker_map_rcu(struct rcu_head *head)
> > > -{
> > > -       kvfree(container_of(head, struct memcg_shrinker_map, rcu));
> > > -}
> > > -
> > >  static int expand_one_shrinker_map(struct mem_cgroup *memcg,
> > >                                    int size, int old_size)
> > >  {
> > > @@ -219,7 +214,7 @@ static int expand_one_shrinker_map(struct mem_cgroup *memcg,
> > >                 memset((void *)new->map + old_size, 0, size - old_size);
> > >
> > >                 rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new);
> > > -               call_rcu(&old->rcu, free_shrinker_map_rcu);
> > > +               kvfree_rcu(old);
> >
> > Please use kvfree_rcu(old, rcu) instead of kvfree_rcu(old). The single
> > param can call synchronize_rcu().
>
> Especially given that you already have the ->rcu field that the
> two-argument form requires.
>
> The reason for using the single-argument form is when you have lots of
> little data structures, such that getting rid of that rcu_head structure
> is valuable enough to be worth the occasional call to synchronize_rcu().
> However, please note that this call to synchronize_rcu() happens only
> under OOM conditions.

Thanks, Shakeel and Paul. I didn't realize the difference. Will use
the two params form in the new version.

>
>                                                         Thanx, Paul
Yang Shi March 8, 2021, 8:22 p.m. UTC | #7
On Mon, Mar 8, 2021 at 8:49 AM Roman Gushchin <guro@fb.com> wrote:
>
> On Sun, Mar 07, 2021 at 10:13:04PM -0800, Shakeel Butt wrote:
> > On Tue, Feb 16, 2021 at 4:13 PM Yang Shi <shy828301@gmail.com> wrote:
> > >
> > > Using kvfree_rcu() to free the old shrinker_maps instead of call_rcu().
> > > We don't have to define a dedicated callback for call_rcu() anymore.
> > >
> > > Signed-off-by: Yang Shi <shy828301@gmail.com>
> > > ---
> > >  mm/vmscan.c | 7 +------
> > >  1 file changed, 1 insertion(+), 6 deletions(-)
> > >
> > > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > > index 2e753c2516fa..c2a309acd86b 100644
> > > --- a/mm/vmscan.c
> > > +++ b/mm/vmscan.c
> > > @@ -192,11 +192,6 @@ static inline int shrinker_map_size(int nr_items)
> > >         return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
> > >  }
> > >
> > > -static void free_shrinker_map_rcu(struct rcu_head *head)
> > > -{
> > > -       kvfree(container_of(head, struct memcg_shrinker_map, rcu));
> > > -}
> > > -
> > >  static int expand_one_shrinker_map(struct mem_cgroup *memcg,
> > >                                    int size, int old_size)
> > >  {
> > > @@ -219,7 +214,7 @@ static int expand_one_shrinker_map(struct mem_cgroup *memcg,
> > >                 memset((void *)new->map + old_size, 0, size - old_size);
> > >
> > >                 rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new);
> > > -               call_rcu(&old->rcu, free_shrinker_map_rcu);
> > > +               kvfree_rcu(old);
> >
> > Please use kvfree_rcu(old, rcu) instead of kvfree_rcu(old). The single
> > param can call synchronize_rcu().
>
> Oh, I didn't know about this difference. Thank you for noticing!

BTW, I think I could keep you and Kirill's acked-by with this change
(using two params form kvfree_rcu) since the change seems trivial.
Shakeel Butt March 8, 2021, 9:11 p.m. UTC | #8
On Mon, Mar 8, 2021 at 12:22 PM Yang Shi <shy828301@gmail.com> wrote:
>
> On Mon, Mar 8, 2021 at 8:49 AM Roman Gushchin <guro@fb.com> wrote:
> >
> > On Sun, Mar 07, 2021 at 10:13:04PM -0800, Shakeel Butt wrote:
> > > On Tue, Feb 16, 2021 at 4:13 PM Yang Shi <shy828301@gmail.com> wrote:
> > > >
> > > > Using kvfree_rcu() to free the old shrinker_maps instead of call_rcu().
> > > > We don't have to define a dedicated callback for call_rcu() anymore.
> > > >
> > > > Signed-off-by: Yang Shi <shy828301@gmail.com>
> > > > ---
> > > >  mm/vmscan.c | 7 +------
> > > >  1 file changed, 1 insertion(+), 6 deletions(-)
> > > >
> > > > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > > > index 2e753c2516fa..c2a309acd86b 100644
> > > > --- a/mm/vmscan.c
> > > > +++ b/mm/vmscan.c
> > > > @@ -192,11 +192,6 @@ static inline int shrinker_map_size(int nr_items)
> > > >         return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
> > > >  }
> > > >
> > > > -static void free_shrinker_map_rcu(struct rcu_head *head)
> > > > -{
> > > > -       kvfree(container_of(head, struct memcg_shrinker_map, rcu));
> > > > -}
> > > > -
> > > >  static int expand_one_shrinker_map(struct mem_cgroup *memcg,
> > > >                                    int size, int old_size)
> > > >  {
> > > > @@ -219,7 +214,7 @@ static int expand_one_shrinker_map(struct mem_cgroup *memcg,
> > > >                 memset((void *)new->map + old_size, 0, size - old_size);
> > > >
> > > >                 rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new);
> > > > -               call_rcu(&old->rcu, free_shrinker_map_rcu);
> > > > +               kvfree_rcu(old);
> > >
> > > Please use kvfree_rcu(old, rcu) instead of kvfree_rcu(old). The single
> > > param can call synchronize_rcu().
> >
> > Oh, I didn't know about this difference. Thank you for noticing!
>
> BTW, I think I could keep you and Kirill's acked-by with this change
> (using two params form kvfree_rcu) since the change seems trivial.

Once you change, you can add:

Reviewed-by: Shakeel Butt <shakeelb@google.com>
diff mbox series

Patch

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 2e753c2516fa..c2a309acd86b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -192,11 +192,6 @@  static inline int shrinker_map_size(int nr_items)
 	return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
 }
 
-static void free_shrinker_map_rcu(struct rcu_head *head)
-{
-	kvfree(container_of(head, struct memcg_shrinker_map, rcu));
-}
-
 static int expand_one_shrinker_map(struct mem_cgroup *memcg,
 				   int size, int old_size)
 {
@@ -219,7 +214,7 @@  static int expand_one_shrinker_map(struct mem_cgroup *memcg,
 		memset((void *)new->map + old_size, 0, size - old_size);
 
 		rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, new);
-		call_rcu(&old->rcu, free_shrinker_map_rcu);
+		kvfree_rcu(old);
 	}
 
 	return 0;