Re: [v8 PATCH 05/13] mm: vmscan: use kvfree_rcu instead of call_rcu
On Mon, Mar 8, 2021 at 12:22 PM Yang Shi wrote:
>
> On Mon, Mar 8, 2021 at 8:49 AM Roman Gushchin 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 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
> > > > ---
> > > > 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
Re: [v8 PATCH 05/13] mm: vmscan: use kvfree_rcu instead of call_rcu
On Mon, Mar 8, 2021 at 8:49 AM Roman Gushchin 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 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
> > > ---
> > > 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.
Re: [v8 PATCH 05/13] mm: vmscan: use kvfree_rcu instead of call_rcu
On Mon, Mar 8, 2021 at 6:54 AM Paul E. McKenney 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 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
> > > ---
> > > 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
Re: [v8 PATCH 05/13] mm: vmscan: use kvfree_rcu instead of call_rcu
On Sun, Mar 07, 2021 at 10:13:04PM -0800, Shakeel Butt wrote:
> On Tue, Feb 16, 2021 at 4:13 PM 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
> > ---
> > 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!
Re: [v8 PATCH 05/13] mm: vmscan: use kvfree_rcu instead of call_rcu
On Sun, Mar 07, 2021 at 10:13:04PM -0800, Shakeel Butt wrote:
> On Tue, Feb 16, 2021 at 4:13 PM 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
> > ---
> > 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
Re: [v8 PATCH 05/13] mm: vmscan: use kvfree_rcu instead of call_rcu
On Tue, Feb 16, 2021 at 4:13 PM 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
> ---
> 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().
Re: [v8 PATCH 05/13] mm: vmscan: use kvfree_rcu instead of call_rcu
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
Acked-by: Kirill Tkhai
> ---
> 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;
>
Re: [v8 PATCH 05/13] mm: vmscan: use kvfree_rcu instead of call_rcu
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
Acked-by: Roman Gushchin
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
>
