Re: [RFC][PATCH 2/7] memcg: don't use mem_cgroup_get() when creating a kmemcg cache
>>> You are putting references but I do not see any single css_{try}get
>>> here. /me puzzled.
>>>
>>
>> There are two things being done in this code:
>> First, we acquired a css_ref to make sure that the underlying cgroup
>> would not go away. That is a short lived reference, and it is put as
>> soon as the cache is created.
>> At this point, we acquire a long-lived per-cache memcg reference count
>> to guarantee that the memcg will still be alive.
>>
>> so it is:
>>
>> enqueue: css_get
>> create : memcg_get, css_put
>> destroy: css_put
>>
>> If I understand Li's patch correctly, he is not touching the first
>> css_get, only turning that into the long lived reference (which was not
>> possible before, since that would prevent rmdir).
>>
>> Then he only needs to get rid of the memcg_get, change the memcg_put to
>> css_put, and get rid of the now extra css_put.
>>
>> He is issuing extra css_puts in memcg_create_kmem_cache, but only in
>> failure paths. So the code reads as:
>> * css_get on enqueue (already done, so not shown in patch)
>> * if it fails, css_put
>> * if it succeeds, don't do anything. This is already the long-lived
>> reference count. put it at release time.
>
> OK, this makes more sense now. It is __memcg_create_cache_enqueue which
> takes the reference and it is not put after this because it replaced
> mem_cgroup reference counting.
> Li, please put something along these lines into the changelog. This is
> really tricky and easy to get misunderstand.
>
Yeah, I think I'll just steal Glauber's explanation as the changelog.
> You can put my Acked-by then.
>
Thanks!
>> The code looks correct, and of course, extremely simpler due to the
>> use of a single reference.
>>
>> Li, am I right in my understanding that this is your intention?
>>
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Re: [RFC][PATCH 2/7] memcg: don't use mem_cgroup_get() when creating a kmemcg cache
On Fri 05-04-13 14:51:10, KAMEZAWA Hiroyuki wrote:
> (2013/04/03 18:12), Li Zefan wrote:
> > Use css_get()/css_put() instead of mem_cgroup_get()/mem_cgroup_put().
> >
> > Signed-off-by: Li Zefan
> > ---
> > mm/memcontrol.c | 10 +-
> > 1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index 43ca91d..dafacb8 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -3191,7 +3191,7 @@ void memcg_release_cache(struct kmem_cache *s)
> > list_del(&s->memcg_params->list);
> > mutex_unlock(&memcg->slab_caches_mutex);
> >
> > - mem_cgroup_put(memcg);
> > + css_put(&memcg->css);
> > out:
> > kfree(s->memcg_params);
> > }
> > @@ -3350,16 +3350,18 @@ static struct kmem_cache
> > *memcg_create_kmem_cache(struct mem_cgroup *memcg,
> >
> > mutex_lock(&memcg_cache_mutex);
> > new_cachep = cachep->memcg_params->memcg_caches[idx];
> > - if (new_cachep)
> > + if (new_cachep) {
> > + css_put(&memcg->css);
> > goto out;
> > + }
>
> Where css_get() against this is done ?
As glauber explained in another email in this thread. It was
__memcg_create_cache_enqueue which took the reference.
--
Michal Hocko
SUSE Labs
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Re: [RFC][PATCH 2/7] memcg: don't use mem_cgroup_get() when creating a kmemcg cache
On Fri 05-04-13 14:28:12, Glauber Costa wrote:
> On 04/03/2013 07:31 PM, Michal Hocko wrote:
> > On Wed 03-04-13 17:12:21, Li Zefan wrote:
> >> Use css_get()/css_put() instead of mem_cgroup_get()/mem_cgroup_put().
> >>
> >> Signed-off-by: Li Zefan
> >> ---
> >> mm/memcontrol.c | 10 +-
> >> 1 file changed, 5 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> >> index 43ca91d..dafacb8 100644
> >> --- a/mm/memcontrol.c
> >> +++ b/mm/memcontrol.c
> >> @@ -3191,7 +3191,7 @@ void memcg_release_cache(struct kmem_cache *s)
> >>list_del(&s->memcg_params->list);
> >>mutex_unlock(&memcg->slab_caches_mutex);
> >>
> >> - mem_cgroup_put(memcg);
> >> + css_put(&memcg->css);
> >> out:
> >>kfree(s->memcg_params);
> >> }
> >> @@ -3350,16 +3350,18 @@ static struct kmem_cache
> >> *memcg_create_kmem_cache(struct mem_cgroup *memcg,
> >>
> >>mutex_lock(&memcg_cache_mutex);
> >>new_cachep = cachep->memcg_params->memcg_caches[idx];
> >> - if (new_cachep)
> >> + if (new_cachep) {
> >> + css_put(&memcg->css);
> >>goto out;
> >> + }
> >>
> >>new_cachep = kmem_cache_dup(memcg, cachep);
> >>if (new_cachep == NULL) {
> >>new_cachep = cachep;
> >> + css_put(&memcg->css);
> >>goto out;
> >>}
> >>
> >> - mem_cgroup_get(memcg);
> >>atomic_set(&new_cachep->memcg_params->nr_pages , 0);
> >>
> >>cachep->memcg_params->memcg_caches[idx] = new_cachep;
> >> @@ -3449,8 +3451,6 @@ static void memcg_create_cache_work_func(struct
> >> work_struct *w)
> >>
> >>cw = container_of(w, struct create_work, work);
> >>memcg_create_kmem_cache(cw->memcg, cw->cachep);
> >> - /* Drop the reference gotten when we enqueued. */
> >> - css_put(&cw->memcg->css);
> >>kfree(cw);
> >> }
> >
> > You are putting references but I do not see any single css_{try}get
> > here. /me puzzled.
> >
>
> There are two things being done in this code:
> First, we acquired a css_ref to make sure that the underlying cgroup
> would not go away. That is a short lived reference, and it is put as
> soon as the cache is created.
> At this point, we acquire a long-lived per-cache memcg reference count
> to guarantee that the memcg will still be alive.
>
> so it is:
>
> enqueue: css_get
> create : memcg_get, css_put
> destroy: css_put
>
> If I understand Li's patch correctly, he is not touching the first
> css_get, only turning that into the long lived reference (which was not
> possible before, since that would prevent rmdir).
>
> Then he only needs to get rid of the memcg_get, change the memcg_put to
> css_put, and get rid of the now extra css_put.
>
> He is issuing extra css_puts in memcg_create_kmem_cache, but only in
> failure paths. So the code reads as:
> * css_get on enqueue (already done, so not shown in patch)
> * if it fails, css_put
> * if it succeeds, don't do anything. This is already the long-lived
> reference count. put it at release time.
OK, this makes more sense now. It is __memcg_create_cache_enqueue which
takes the reference and it is not put after this because it replaced
mem_cgroup reference counting.
Li, please put something along these lines into the changelog. This is
really tricky and easy to get misunderstand.
You can put my Acked-by then.
> The code looks correct, and of course, extremely simpler due to the
> use of a single reference.
>
> Li, am I right in my understanding that this is your intention?
>
> --
> To unsubscribe from this list: send the line "unsubscribe cgroups" in
> the body of a message to majord...@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Michal Hocko
SUSE Labs
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Re: [RFC][PATCH 2/7] memcg: don't use mem_cgroup_get() when creating a kmemcg cache
On 04/03/2013 07:31 PM, Michal Hocko wrote:
> On Wed 03-04-13 17:12:21, Li Zefan wrote:
>> Use css_get()/css_put() instead of mem_cgroup_get()/mem_cgroup_put().
>>
>> Signed-off-by: Li Zefan
>> ---
>> mm/memcontrol.c | 10 +-
>> 1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 43ca91d..dafacb8 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -3191,7 +3191,7 @@ void memcg_release_cache(struct kmem_cache *s)
>> list_del(&s->memcg_params->list);
>> mutex_unlock(&memcg->slab_caches_mutex);
>>
>> -mem_cgroup_put(memcg);
>> +css_put(&memcg->css);
>> out:
>> kfree(s->memcg_params);
>> }
>> @@ -3350,16 +3350,18 @@ static struct kmem_cache
>> *memcg_create_kmem_cache(struct mem_cgroup *memcg,
>>
>> mutex_lock(&memcg_cache_mutex);
>> new_cachep = cachep->memcg_params->memcg_caches[idx];
>> -if (new_cachep)
>> +if (new_cachep) {
>> +css_put(&memcg->css);
>> goto out;
>> +}
>>
>> new_cachep = kmem_cache_dup(memcg, cachep);
>> if (new_cachep == NULL) {
>> new_cachep = cachep;
>> +css_put(&memcg->css);
>> goto out;
>> }
>>
>> -mem_cgroup_get(memcg);
>> atomic_set(&new_cachep->memcg_params->nr_pages , 0);
>>
>> cachep->memcg_params->memcg_caches[idx] = new_cachep;
>> @@ -3449,8 +3451,6 @@ static void memcg_create_cache_work_func(struct
>> work_struct *w)
>>
>> cw = container_of(w, struct create_work, work);
>> memcg_create_kmem_cache(cw->memcg, cw->cachep);
>> -/* Drop the reference gotten when we enqueued. */
>> -css_put(&cw->memcg->css);
>> kfree(cw);
>> }
>
> You are putting references but I do not see any single css_{try}get
> here. /me puzzled.
>
There are two things being done in this code:
First, we acquired a css_ref to make sure that the underlying cgroup
would not go away. That is a short lived reference, and it is put as
soon as the cache is created.
At this point, we acquire a long-lived per-cache memcg reference count
to guarantee that the memcg will still be alive.
so it is:
enqueue: css_get
create : memcg_get, css_put
destroy: css_put
If I understand Li's patch correctly, he is not touching the first
css_get, only turning that into the long lived reference (which was not
possible before, since that would prevent rmdir).
Then he only needs to get rid of the memcg_get, change the memcg_put to
css_put, and get rid of the now extra css_put.
He is issuing extra css_puts in memcg_create_kmem_cache, but only in
failure paths. So the code reads as:
* css_get on enqueue (already done, so not shown in patch)
* if it fails, css_put
* if it succeeds, don't do anything. This is already the long-lived
reference count. put it at release time.
The code looks correct, and of course, extremely simpler due to the
use of a single reference.
Li, am I right in my understanding that this is your intention?
--
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Re: [RFC][PATCH 2/7] memcg: don't use mem_cgroup_get() when creating a kmemcg cache
(2013/04/03 18:12), Li Zefan wrote:
> Use css_get()/css_put() instead of mem_cgroup_get()/mem_cgroup_put().
>
> Signed-off-by: Li Zefan
> ---
> mm/memcontrol.c | 10 +-
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 43ca91d..dafacb8 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3191,7 +3191,7 @@ void memcg_release_cache(struct kmem_cache *s)
> list_del(&s->memcg_params->list);
> mutex_unlock(&memcg->slab_caches_mutex);
>
> - mem_cgroup_put(memcg);
> + css_put(&memcg->css);
> out:
> kfree(s->memcg_params);
> }
> @@ -3350,16 +3350,18 @@ static struct kmem_cache
> *memcg_create_kmem_cache(struct mem_cgroup *memcg,
>
> mutex_lock(&memcg_cache_mutex);
> new_cachep = cachep->memcg_params->memcg_caches[idx];
> - if (new_cachep)
> + if (new_cachep) {
> + css_put(&memcg->css);
> goto out;
> + }
Where css_get() against this is done ?
Thanks,
-Kame
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Re: [RFC][PATCH 2/7] memcg: don't use mem_cgroup_get() when creating a kmemcg cache
On Wed 03-04-13 17:12:21, Li Zefan wrote:
> Use css_get()/css_put() instead of mem_cgroup_get()/mem_cgroup_put().
>
> Signed-off-by: Li Zefan
> ---
> mm/memcontrol.c | 10 +-
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 43ca91d..dafacb8 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3191,7 +3191,7 @@ void memcg_release_cache(struct kmem_cache *s)
> list_del(&s->memcg_params->list);
> mutex_unlock(&memcg->slab_caches_mutex);
>
> - mem_cgroup_put(memcg);
> + css_put(&memcg->css);
> out:
> kfree(s->memcg_params);
> }
> @@ -3350,16 +3350,18 @@ static struct kmem_cache
> *memcg_create_kmem_cache(struct mem_cgroup *memcg,
>
> mutex_lock(&memcg_cache_mutex);
> new_cachep = cachep->memcg_params->memcg_caches[idx];
> - if (new_cachep)
> + if (new_cachep) {
> + css_put(&memcg->css);
> goto out;
> + }
>
> new_cachep = kmem_cache_dup(memcg, cachep);
> if (new_cachep == NULL) {
> new_cachep = cachep;
> + css_put(&memcg->css);
> goto out;
> }
>
> - mem_cgroup_get(memcg);
> atomic_set(&new_cachep->memcg_params->nr_pages , 0);
>
> cachep->memcg_params->memcg_caches[idx] = new_cachep;
> @@ -3449,8 +3451,6 @@ static void memcg_create_cache_work_func(struct
> work_struct *w)
>
> cw = container_of(w, struct create_work, work);
> memcg_create_kmem_cache(cw->memcg, cw->cachep);
> - /* Drop the reference gotten when we enqueued. */
> - css_put(&cw->memcg->css);
> kfree(cw);
> }
You are putting references but I do not see any single css_{try}get
here. /me puzzled.
--
Michal Hocko
SUSE Labs
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Re: [RFC][PATCH 2/7] memcg: don't use mem_cgroup_get() when creating a kmemcg cache
On 04/03/2013 01:12 PM, Li Zefan wrote:
> Use css_get()/css_put() instead of mem_cgroup_get()/mem_cgroup_put().
>
> Signed-off-by: Li Zefan
> ---
> mm/memcontrol.c | 10 +-
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 43ca91d..dafacb8 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3191,7 +3191,7 @@ void memcg_release_cache(struct kmem_cache *s)
> list_del(&s->memcg_params->list);
> mutex_unlock(&memcg->slab_caches_mutex);
>
> - mem_cgroup_put(memcg);
> + css_put(&memcg->css);
> out:
> kfree(s->memcg_params);
> }
> @@ -3350,16 +3350,18 @@ static struct kmem_cache
> *memcg_create_kmem_cache(struct mem_cgroup *memcg,
>
> mutex_lock(&memcg_cache_mutex);
> new_cachep = cachep->memcg_params->memcg_caches[idx];
> - if (new_cachep)
> + if (new_cachep) {
> + css_put(&memcg->css);
> goto out;
> + }
>
> new_cachep = kmem_cache_dup(memcg, cachep);
> if (new_cachep == NULL) {
> new_cachep = cachep;
> + css_put(&memcg->css);
> goto out;
> }
>
> - mem_cgroup_get(memcg);
> atomic_set(&new_cachep->memcg_params->nr_pages , 0);
>
> cachep->memcg_params->memcg_caches[idx] = new_cachep;
> @@ -3449,8 +3451,6 @@ static void memcg_create_cache_work_func(struct
> work_struct *w)
>
> cw = container_of(w, struct create_work, work);
> memcg_create_kmem_cache(cw->memcg, cw->cachep);
> - /* Drop the reference gotten when we enqueued. */
> - css_put(&cw->memcg->css);
> kfree(cw);
> }
>
>
At first look, this one seems all right.
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[RFC][PATCH 2/7] memcg: don't use mem_cgroup_get() when creating a kmemcg cache
Use css_get()/css_put() instead of mem_cgroup_get()/mem_cgroup_put().
Signed-off-by: Li Zefan
---
mm/memcontrol.c | 10 +-
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 43ca91d..dafacb8 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3191,7 +3191,7 @@ void memcg_release_cache(struct kmem_cache *s)
list_del(&s->memcg_params->list);
mutex_unlock(&memcg->slab_caches_mutex);
- mem_cgroup_put(memcg);
+ css_put(&memcg->css);
out:
kfree(s->memcg_params);
}
@@ -3350,16 +3350,18 @@ static struct kmem_cache
*memcg_create_kmem_cache(struct mem_cgroup *memcg,
mutex_lock(&memcg_cache_mutex);
new_cachep = cachep->memcg_params->memcg_caches[idx];
- if (new_cachep)
+ if (new_cachep) {
+ css_put(&memcg->css);
goto out;
+ }
new_cachep = kmem_cache_dup(memcg, cachep);
if (new_cachep == NULL) {
new_cachep = cachep;
+ css_put(&memcg->css);
goto out;
}
- mem_cgroup_get(memcg);
atomic_set(&new_cachep->memcg_params->nr_pages , 0);
cachep->memcg_params->memcg_caches[idx] = new_cachep;
@@ -3449,8 +3451,6 @@ static void memcg_create_cache_work_func(struct
work_struct *w)
cw = container_of(w, struct create_work, work);
memcg_create_kmem_cache(cw->memcg, cw->cachep);
- /* Drop the reference gotten when we enqueued. */
- css_put(&cw->memcg->css);
kfree(cw);
}
--
1.8.0.2
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