diff mbox series

[v3,09/11] mm: vmscan: don't need allocate shrinker->nr_deferred for memcg aware shrinkers

Message ID 20210105225817.1036378-10-shy828301@gmail.com (mailing list archive)
State New, archived
Headers show
Series Make shrinker's nr_deferred memcg aware | expand

Commit Message

Yang Shi Jan. 5, 2021, 10:58 p.m. UTC 
Now nr_deferred is available on per memcg level for memcg aware shrinkers, so don't need
allocate shrinker->nr_deferred for such shrinkers anymore.

The prealloc_memcg_shrinker() would return -ENOSYS if !CONFIG_MEMCG or memcg is disabled
by kernel command line, then shrinker's SHRINKER_MEMCG_AWARE flag would be cleared.
This makes the implementation of this patch simpler.

Signed-off-by: Yang Shi <shy828301@gmail.com>
---
 mm/vmscan.c | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

Comments

Kirill Tkhai Jan. 6, 2021, 11:15 a.m. UTC | #1 
On 06.01.2021 01:58, Yang Shi wrote:
> Now nr_deferred is available on per memcg level for memcg aware shrinkers, so don't need
> allocate shrinker->nr_deferred for such shrinkers anymore.
> 
> The prealloc_memcg_shrinker() would return -ENOSYS if !CONFIG_MEMCG or memcg is disabled
> by kernel command line, then shrinker's SHRINKER_MEMCG_AWARE flag would be cleared.
> This makes the implementation of this patch simpler.
> 
> Signed-off-by: Yang Shi <shy828301@gmail.com>
> ---
>  mm/vmscan.c | 33 ++++++++++++++++++---------------
>  1 file changed, 18 insertions(+), 15 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index f20ed8e928c2..d9795fb0f1c5 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -340,6 +340,9 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
>  {
>  	int id, ret = -ENOMEM;
>  
> +	if (mem_cgroup_disabled())
> +		return -ENOSYS;
> +
>  	down_write(&shrinker_rwsem);
>  	/* This may call shrinker, so it must use down_read_trylock() */
>  	id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL);
> @@ -424,7 +427,7 @@ static bool writeback_throttling_sane(struct scan_control *sc)
>  #else
>  static int prealloc_memcg_shrinker(struct shrinker *shrinker)
>  {
> -	return 0;
> +	return -ENOSYS;
>  }
>  
>  static void unregister_memcg_shrinker(struct shrinker *shrinker)
> @@ -535,8 +538,20 @@ unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone
>   */
>  int prealloc_shrinker(struct shrinker *shrinker)
>  {
> -	unsigned int size = sizeof(*shrinker->nr_deferred);
> +	unsigned int size;
> +	int err;
> +
> +	if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
> +		err = prealloc_memcg_shrinker(shrinker);
> +		if (!err)
> +			return 0;
> +		if (err != -ENOSYS)
> +			return err;
> +
> +		shrinker->flags &= ~SHRINKER_MEMCG_AWARE;

This looks very confusing.

In case of you want to disable preallocation branch for !MEMCG case,
you should firstly consider something like the below:

#ifdef CONFIG_MEMCG
#define SHRINKER_MEMCG_AWARE    (1 << 2)
#else
#define SHRINKER_MEMCG_AWARE    0
#endif

> +	}
>  
> +	size = sizeof(*shrinker->nr_deferred);
>  	if (shrinker->flags & SHRINKER_NUMA_AWARE)
>  		size *= nr_node_ids;
>  
> @@ -544,26 +559,14 @@ int prealloc_shrinker(struct shrinker *shrinker)
>  	if (!shrinker->nr_deferred)
>  		return -ENOMEM;
>  
> -	if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
> -		if (prealloc_memcg_shrinker(shrinker))
> -			goto free_deferred;
> -	}
>  
>  	return 0;
> -
> -free_deferred:
> -	kfree(shrinker->nr_deferred);
> -	shrinker->nr_deferred = NULL;
> -	return -ENOMEM;
>  }
>  
>  void free_prealloced_shrinker(struct shrinker *shrinker)
>  {
> -	if (!shrinker->nr_deferred)
> -		return;
> -
>  	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
> -		unregister_memcg_shrinker(shrinker);
> +		return unregister_memcg_shrinker(shrinker);
>  
>  	kfree(shrinker->nr_deferred);
>  	shrinker->nr_deferred = NULL;
>
Yang Shi Jan. 11, 2021, 6:40 p.m. UTC | #2 
On Wed, Jan 6, 2021 at 3:16 AM Kirill Tkhai <ktkhai@virtuozzo.com> wrote:
>
> On 06.01.2021 01:58, Yang Shi wrote:
> > Now nr_deferred is available on per memcg level for memcg aware shrinkers, so don't need
> > allocate shrinker->nr_deferred for such shrinkers anymore.
> >
> > The prealloc_memcg_shrinker() would return -ENOSYS if !CONFIG_MEMCG or memcg is disabled
> > by kernel command line, then shrinker's SHRINKER_MEMCG_AWARE flag would be cleared.
> > This makes the implementation of this patch simpler.
> >
> > Signed-off-by: Yang Shi <shy828301@gmail.com>
> > ---
> >  mm/vmscan.c | 33 ++++++++++++++++++---------------
> >  1 file changed, 18 insertions(+), 15 deletions(-)
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index f20ed8e928c2..d9795fb0f1c5 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -340,6 +340,9 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
> >  {
> >       int id, ret = -ENOMEM;
> >
> > +     if (mem_cgroup_disabled())
> > +             return -ENOSYS;
> > +
> >       down_write(&shrinker_rwsem);
> >       /* This may call shrinker, so it must use down_read_trylock() */
> >       id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL);
> > @@ -424,7 +427,7 @@ static bool writeback_throttling_sane(struct scan_control *sc)
> >  #else
> >  static int prealloc_memcg_shrinker(struct shrinker *shrinker)
> >  {
> > -     return 0;
> > +     return -ENOSYS;
> >  }
> >
> >  static void unregister_memcg_shrinker(struct shrinker *shrinker)
> > @@ -535,8 +538,20 @@ unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone
> >   */
> >  int prealloc_shrinker(struct shrinker *shrinker)
> >  {
> > -     unsigned int size = sizeof(*shrinker->nr_deferred);
> > +     unsigned int size;
> > +     int err;
> > +
> > +     if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
> > +             err = prealloc_memcg_shrinker(shrinker);
> > +             if (!err)
> > +                     return 0;
> > +             if (err != -ENOSYS)
> > +                     return err;
> > +
> > +             shrinker->flags &= ~SHRINKER_MEMCG_AWARE;
>
> This looks very confusing.
>
> In case of you want to disable preallocation branch for !MEMCG case,
> you should firstly consider something like the below:

Not only !CONFIG_MEMCG, but also "cgroup_disable=memory" case.

>
> #ifdef CONFIG_MEMCG
> #define SHRINKER_MEMCG_AWARE    (1 << 2)
> #else
> #define SHRINKER_MEMCG_AWARE    0
> #endif

This could handle !CONFIG_MEMCG case, but can't deal with
"cgroup_disable=memory" case. We could consider check
mem_cgroup_disabled() when initializing shrinker, but this may result
in touching fs codes like below:

--- a/fs/super.c
+++ b/fs/super.c
@@ -266,7 +266,9 @@ static struct super_block *alloc_super(struct
file_system_type *type, int flags,
        s->s_shrink.scan_objects = super_cache_scan;
        s->s_shrink.count_objects = super_cache_count;
        s->s_shrink.batch = 1024;
-       s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE;
+       s->s_shrink.flags = SHRINKER_NUMA_AWARE;
+       if (!mem_cgroup_disabled())
+               s->s_shrink.flags |= SHRINKER_MEMCG_AWARE;
        if (prealloc_shrinker(&s->s_shrink))
                goto fail;
        if (list_lru_init_memcg(&s->s_dentry_lru, &s->s_shrink))


>
> > +     }
> >
> > +     size = sizeof(*shrinker->nr_deferred);
> >       if (shrinker->flags & SHRINKER_NUMA_AWARE)
> >               size *= nr_node_ids;
> >
> > @@ -544,26 +559,14 @@ int prealloc_shrinker(struct shrinker *shrinker)
> >       if (!shrinker->nr_deferred)
> >               return -ENOMEM;
> >
> > -     if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
> > -             if (prealloc_memcg_shrinker(shrinker))
> > -                     goto free_deferred;
> > -     }
> >
> >       return 0;
> > -
> > -free_deferred:
> > -     kfree(shrinker->nr_deferred);
> > -     shrinker->nr_deferred = NULL;
> > -     return -ENOMEM;
> >  }
> >
> >  void free_prealloced_shrinker(struct shrinker *shrinker)
> >  {
> > -     if (!shrinker->nr_deferred)
> > -             return;
> > -
> >       if (shrinker->flags & SHRINKER_MEMCG_AWARE)
> > -             unregister_memcg_shrinker(shrinker);
> > +             return unregister_memcg_shrinker(shrinker);
> >
> >       kfree(shrinker->nr_deferred);
> >       shrinker->nr_deferred = NULL;
> >
>
>
Kirill Tkhai Jan. 11, 2021, 9:57 p.m. UTC | #3 
On 11.01.2021 21:40, Yang Shi wrote:
> On Wed, Jan 6, 2021 at 3:16 AM Kirill Tkhai <ktkhai@virtuozzo.com> wrote:
>>
>> On 06.01.2021 01:58, Yang Shi wrote:
>>> Now nr_deferred is available on per memcg level for memcg aware shrinkers, so don't need
>>> allocate shrinker->nr_deferred for such shrinkers anymore.
>>>
>>> The prealloc_memcg_shrinker() would return -ENOSYS if !CONFIG_MEMCG or memcg is disabled
>>> by kernel command line, then shrinker's SHRINKER_MEMCG_AWARE flag would be cleared.
>>> This makes the implementation of this patch simpler.
>>>
>>> Signed-off-by: Yang Shi <shy828301@gmail.com>
>>> ---
>>>  mm/vmscan.c | 33 ++++++++++++++++++---------------
>>>  1 file changed, 18 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>> index f20ed8e928c2..d9795fb0f1c5 100644
>>> --- a/mm/vmscan.c
>>> +++ b/mm/vmscan.c
>>> @@ -340,6 +340,9 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
>>>  {
>>>       int id, ret = -ENOMEM;
>>>
>>> +     if (mem_cgroup_disabled())
>>> +             return -ENOSYS;
>>> +
>>>       down_write(&shrinker_rwsem);
>>>       /* This may call shrinker, so it must use down_read_trylock() */
>>>       id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL);
>>> @@ -424,7 +427,7 @@ static bool writeback_throttling_sane(struct scan_control *sc)
>>>  #else
>>>  static int prealloc_memcg_shrinker(struct shrinker *shrinker)
>>>  {
>>> -     return 0;
>>> +     return -ENOSYS;
>>>  }
>>>
>>>  static void unregister_memcg_shrinker(struct shrinker *shrinker)
>>> @@ -535,8 +538,20 @@ unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone
>>>   */
>>>  int prealloc_shrinker(struct shrinker *shrinker)
>>>  {
>>> -     unsigned int size = sizeof(*shrinker->nr_deferred);
>>> +     unsigned int size;
>>> +     int err;
>>> +
>>> +     if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
>>> +             err = prealloc_memcg_shrinker(shrinker);
>>> +             if (!err)
>>> +                     return 0;
>>> +             if (err != -ENOSYS)
>>> +                     return err;
>>> +
>>> +             shrinker->flags &= ~SHRINKER_MEMCG_AWARE;
>>
>> This looks very confusing.
>>
>> In case of you want to disable preallocation branch for !MEMCG case,
>> you should firstly consider something like the below:
> 
> Not only !CONFIG_MEMCG, but also "cgroup_disable=memory" case.
> 
>>
>> #ifdef CONFIG_MEMCG
>> #define SHRINKER_MEMCG_AWARE    (1 << 2)
>> #else
>> #define SHRINKER_MEMCG_AWARE    0
>> #endif
> 
> This could handle !CONFIG_MEMCG case, but can't deal with
> "cgroup_disable=memory" case. We could consider check
> mem_cgroup_disabled() when initializing shrinker, but this may result
> in touching fs codes like below:
> 
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -266,7 +266,9 @@ static struct super_block *alloc_super(struct
> file_system_type *type, int flags,
>         s->s_shrink.scan_objects = super_cache_scan;
>         s->s_shrink.count_objects = super_cache_count;
>         s->s_shrink.batch = 1024;
> -       s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE;
> +       s->s_shrink.flags = SHRINKER_NUMA_AWARE;
> +       if (!mem_cgroup_disabled())
> +               s->s_shrink.flags |= SHRINKER_MEMCG_AWARE;
>         if (prealloc_shrinker(&s->s_shrink))
>                 goto fail;
>         if (list_lru_init_memcg(&s->s_dentry_lru, &s->s_shrink))

Oh. If so, then initial variant was better.

>>
>>> +     }
>>>
>>> +     size = sizeof(*shrinker->nr_deferred);
>>>       if (shrinker->flags & SHRINKER_NUMA_AWARE)
>>>               size *= nr_node_ids;
>>>
>>> @@ -544,26 +559,14 @@ int prealloc_shrinker(struct shrinker *shrinker)
>>>       if (!shrinker->nr_deferred)
>>>               return -ENOMEM;
>>>
>>> -     if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
>>> -             if (prealloc_memcg_shrinker(shrinker))
>>> -                     goto free_deferred;
>>> -     }
>>>
>>>       return 0;
>>> -
>>> -free_deferred:
>>> -     kfree(shrinker->nr_deferred);
>>> -     shrinker->nr_deferred = NULL;
>>> -     return -ENOMEM;
>>>  }
>>>
>>>  void free_prealloced_shrinker(struct shrinker *shrinker)
>>>  {
>>> -     if (!shrinker->nr_deferred)
>>> -             return;
>>> -
>>>       if (shrinker->flags & SHRINKER_MEMCG_AWARE)
>>> -             unregister_memcg_shrinker(shrinker);
>>> +             return unregister_memcg_shrinker(shrinker);
>>>
>>>       kfree(shrinker->nr_deferred);
>>>       shrinker->nr_deferred = NULL;
>>>
>>
>>
diff mbox series

Patch

diff --git a/mm/vmscan.c b/mm/vmscan.c
index f20ed8e928c2..d9795fb0f1c5 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -340,6 +340,9 @@  static int prealloc_memcg_shrinker(struct shrinker *shrinker)
 {
 	int id, ret = -ENOMEM;
 
+	if (mem_cgroup_disabled())
+		return -ENOSYS;
+
 	down_write(&shrinker_rwsem);
 	/* This may call shrinker, so it must use down_read_trylock() */
 	id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL);
@@ -424,7 +427,7 @@  static bool writeback_throttling_sane(struct scan_control *sc)
 #else
 static int prealloc_memcg_shrinker(struct shrinker *shrinker)
 {
-	return 0;
+	return -ENOSYS;
 }
 
 static void unregister_memcg_shrinker(struct shrinker *shrinker)
@@ -535,8 +538,20 @@  unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone
  */
 int prealloc_shrinker(struct shrinker *shrinker)
 {
-	unsigned int size = sizeof(*shrinker->nr_deferred);
+	unsigned int size;
+	int err;
+
+	if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
+		err = prealloc_memcg_shrinker(shrinker);
+		if (!err)
+			return 0;
+		if (err != -ENOSYS)
+			return err;
+
+		shrinker->flags &= ~SHRINKER_MEMCG_AWARE;
+	}
 
+	size = sizeof(*shrinker->nr_deferred);
 	if (shrinker->flags & SHRINKER_NUMA_AWARE)
 		size *= nr_node_ids;
 
@@ -544,26 +559,14 @@  int prealloc_shrinker(struct shrinker *shrinker)
 	if (!shrinker->nr_deferred)
 		return -ENOMEM;
 
-	if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
-		if (prealloc_memcg_shrinker(shrinker))
-			goto free_deferred;
-	}
 
 	return 0;
-
-free_deferred:
-	kfree(shrinker->nr_deferred);
-	shrinker->nr_deferred = NULL;
-	return -ENOMEM;
 }
 
 void free_prealloced_shrinker(struct shrinker *shrinker)
 {
-	if (!shrinker->nr_deferred)
-		return;
-
 	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
-		unregister_memcg_shrinker(shrinker);
+		return unregister_memcg_shrinker(shrinker);
 
 	kfree(shrinker->nr_deferred);
 	shrinker->nr_deferred = NULL;