Re: [Intel-gfx] [PATCH v15 12/23] drm/shmem-helper: Add and use pages_pin_count
On 8/28/23 14:46, Boris Brezillon wrote:
> On Sun, 27 Aug 2023 20:54:38 +0300
> Dmitry Osipenko wrote:
>
>> Add separate pages_pin_count for tracking of whether drm-shmem pages are
>> moveable or not. With the addition of memory shrinker support to drm-shmem,
>> the pages_use_count will no longer determine whether pages are hard-pinned
>> in memory, but whether pages exit and are soft-pinned (and could be swapped
>> out). The pages_pin_count > 1 will hard-pin pages in memory.
>>
>> Suggested-by: Boris Brezillon
>> Signed-off-by: Dmitry Osipenko
>> ---
>> drivers/gpu/drm/drm_gem_shmem_helper.c | 22 +-
>> include/drm/drm_gem_shmem_helper.h | 10 ++
>> 2 files changed, 27 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c
>> b/drivers/gpu/drm/drm_gem_shmem_helper.c
>> index d545d3d227d7..1a7e5c332fd8 100644
>> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
>> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
>> @@ -234,14 +234,22 @@ static int drm_gem_shmem_pin_locked(struct
>> drm_gem_shmem_object *shmem)
>>
>> dma_resv_assert_held(shmem->base.resv);
>>
>> +if (kref_get_unless_zero(>pages_pin_count))
>> +return 0;
>> +
>> ret = drm_gem_shmem_get_pages_locked(shmem);
>> +if (!ret)
>> +kref_init(>pages_pin_count);
>>
>> return ret;
>> }
>>
>> -static void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
>> +static void drm_gem_shmem_kref_unpin_pages(struct kref *kref)
>> {
>> -dma_resv_assert_held(shmem->base.resv);
>> +struct drm_gem_shmem_object *shmem;
>> +
>> +shmem = container_of(kref, struct drm_gem_shmem_object,
>> + pages_pin_count);
>>
>> drm_gem_shmem_put_pages_locked(shmem);
>> }
>> @@ -263,6 +271,9 @@ int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
>>
>> drm_WARN_ON(obj->dev, obj->import_attach);
>>
>> +if (kref_get_unless_zero(>pages_pin_count))
>> +return 0;
>> +
>> ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
>> if (ret)
>> return ret;
>> @@ -286,9 +297,10 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object
>> *shmem)
>>
>> drm_WARN_ON(obj->dev, obj->import_attach);
>>
>> -dma_resv_lock(shmem->base.resv, NULL);
>> -drm_gem_shmem_unpin_locked(shmem);
>> -dma_resv_unlock(shmem->base.resv);
>> +if (kref_put_dma_resv(>pages_pin_count,
>> + drm_gem_shmem_kref_unpin_pages,
>> + obj->resv, NULL))
>> +dma_resv_unlock(obj->resv);
>> }
>> EXPORT_SYMBOL_GPL(drm_gem_shmem_unpin);
>>
>> diff --git a/include/drm/drm_gem_shmem_helper.h
>> b/include/drm/drm_gem_shmem_helper.h
>> index ec2d8b24e3cf..afb7cd671e2a 100644
>> --- a/include/drm/drm_gem_shmem_helper.h
>> +++ b/include/drm/drm_gem_shmem_helper.h
>> @@ -39,6 +39,16 @@ struct drm_gem_shmem_object {
>> */
>> unsigned int pages_use_count;
>>
>> +/**
>> + * @pages_pin_count:
>> + *
>> + * Reference count on the pinned pages table.
>> + * The pages allowed to be evicted and purged by memory
>> + * shrinker only when the count is zero, otherwise pages
>> + * are hard-pinned in memory.
>> + */
>> +struct kref pages_pin_count;
>
> I know it's tempting to use kref for the pages use/pin count, but I'm
> wondering if we wouldn't be better using a refcount_t, which provides
> overflow/underflow protection while still letting us control how we
> want to handle the locking for 0 <-> 1 transitions. By doing that, we
> avoid introducing core locking changes that might be more
> controversial/longer to get accepted. Besides, I suspect the resulting
> code (the one using a refcount_t) won't be more verbose/complicated (no
> release functions needed if you don't use kref_put(), which makes
> things closer to what we have right now).
Alright, let's try to use refcount_t since Christian also doesn't like kref
--
Best regards,
Dmitry
Re: [Intel-gfx] [PATCH v15 12/23] drm/shmem-helper: Add and use pages_pin_count
On Sun, 27 Aug 2023 20:54:38 +0300
Dmitry Osipenko wrote:
> Add separate pages_pin_count for tracking of whether drm-shmem pages are
> moveable or not. With the addition of memory shrinker support to drm-shmem,
> the pages_use_count will no longer determine whether pages are hard-pinned
> in memory, but whether pages exit and are soft-pinned (and could be swapped
> out). The pages_pin_count > 1 will hard-pin pages in memory.
>
> Suggested-by: Boris Brezillon
> Signed-off-by: Dmitry Osipenko
> ---
> drivers/gpu/drm/drm_gem_shmem_helper.c | 22 +-
> include/drm/drm_gem_shmem_helper.h | 10 ++
> 2 files changed, 27 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c
> b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index d545d3d227d7..1a7e5c332fd8 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -234,14 +234,22 @@ static int drm_gem_shmem_pin_locked(struct
> drm_gem_shmem_object *shmem)
>
> dma_resv_assert_held(shmem->base.resv);
>
> + if (kref_get_unless_zero(>pages_pin_count))
> + return 0;
> +
> ret = drm_gem_shmem_get_pages_locked(shmem);
> + if (!ret)
> + kref_init(>pages_pin_count);
>
> return ret;
> }
>
> -static void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
> +static void drm_gem_shmem_kref_unpin_pages(struct kref *kref)
> {
> - dma_resv_assert_held(shmem->base.resv);
> + struct drm_gem_shmem_object *shmem;
> +
> + shmem = container_of(kref, struct drm_gem_shmem_object,
> + pages_pin_count);
>
> drm_gem_shmem_put_pages_locked(shmem);
> }
> @@ -263,6 +271,9 @@ int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
>
> drm_WARN_ON(obj->dev, obj->import_attach);
>
> + if (kref_get_unless_zero(>pages_pin_count))
> + return 0;
> +
> ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
> if (ret)
> return ret;
> @@ -286,9 +297,10 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object
> *shmem)
>
> drm_WARN_ON(obj->dev, obj->import_attach);
>
> - dma_resv_lock(shmem->base.resv, NULL);
> - drm_gem_shmem_unpin_locked(shmem);
> - dma_resv_unlock(shmem->base.resv);
> + if (kref_put_dma_resv(>pages_pin_count,
> + drm_gem_shmem_kref_unpin_pages,
> + obj->resv, NULL))
> + dma_resv_unlock(obj->resv);
> }
> EXPORT_SYMBOL_GPL(drm_gem_shmem_unpin);
>
> diff --git a/include/drm/drm_gem_shmem_helper.h
> b/include/drm/drm_gem_shmem_helper.h
> index ec2d8b24e3cf..afb7cd671e2a 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -39,6 +39,16 @@ struct drm_gem_shmem_object {
>*/
> unsigned int pages_use_count;
>
> + /**
> + * @pages_pin_count:
> + *
> + * Reference count on the pinned pages table.
> + * The pages allowed to be evicted and purged by memory
> + * shrinker only when the count is zero, otherwise pages
> + * are hard-pinned in memory.
> + */
> + struct kref pages_pin_count;
I know it's tempting to use kref for the pages use/pin count, but I'm
wondering if we wouldn't be better using a refcount_t, which provides
overflow/underflow protection while still letting us control how we
want to handle the locking for 0 <-> 1 transitions. By doing that, we
avoid introducing core locking changes that might be more
controversial/longer to get accepted. Besides, I suspect the resulting
code (the one using a refcount_t) won't be more verbose/complicated (no
release functions needed if you don't use kref_put(), which makes
things closer to what we have right now).
> +
> /**
>* @madv: State for madvise
>*
Re: [Intel-gfx] [PATCH v15 12/23] drm/shmem-helper: Add and use pages_pin_count
On Sun, 27 Aug 2023 20:54:38 +0300
Dmitry Osipenko wrote:
> Add separate pages_pin_count for tracking of whether drm-shmem pages are
> moveable or not. With the addition of memory shrinker support to drm-shmem,
> the pages_use_count will no longer determine whether pages are hard-pinned
> in memory, but whether pages exit and are soft-pinned (and could be swapped
^exist
> out). The pages_pin_count > 1 will hard-pin pages in memory.
>
> Suggested-by: Boris Brezillon
> Signed-off-by: Dmitry Osipenko
> ---
> drivers/gpu/drm/drm_gem_shmem_helper.c | 22 +-
> include/drm/drm_gem_shmem_helper.h | 10 ++
> 2 files changed, 27 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c
> b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index d545d3d227d7..1a7e5c332fd8 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -234,14 +234,22 @@ static int drm_gem_shmem_pin_locked(struct
> drm_gem_shmem_object *shmem)
>
> dma_resv_assert_held(shmem->base.resv);
>
> + if (kref_get_unless_zero(>pages_pin_count))
> + return 0;
> +
> ret = drm_gem_shmem_get_pages_locked(shmem);
> + if (!ret)
> + kref_init(>pages_pin_count);
>
> return ret;
> }
>
> -static void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
> +static void drm_gem_shmem_kref_unpin_pages(struct kref *kref)
> {
> - dma_resv_assert_held(shmem->base.resv);
> + struct drm_gem_shmem_object *shmem;
> +
> + shmem = container_of(kref, struct drm_gem_shmem_object,
> + pages_pin_count);
>
> drm_gem_shmem_put_pages_locked(shmem);
> }
> @@ -263,6 +271,9 @@ int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
>
> drm_WARN_ON(obj->dev, obj->import_attach);
>
> + if (kref_get_unless_zero(>pages_pin_count))
> + return 0;
> +
> ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
> if (ret)
> return ret;
> @@ -286,9 +297,10 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object
> *shmem)
>
> drm_WARN_ON(obj->dev, obj->import_attach);
>
> - dma_resv_lock(shmem->base.resv, NULL);
> - drm_gem_shmem_unpin_locked(shmem);
> - dma_resv_unlock(shmem->base.resv);
> + if (kref_put_dma_resv(>pages_pin_count,
> + drm_gem_shmem_kref_unpin_pages,
> + obj->resv, NULL))
> + dma_resv_unlock(obj->resv);
> }
> EXPORT_SYMBOL_GPL(drm_gem_shmem_unpin);
>
> diff --git a/include/drm/drm_gem_shmem_helper.h
> b/include/drm/drm_gem_shmem_helper.h
> index ec2d8b24e3cf..afb7cd671e2a 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -39,6 +39,16 @@ struct drm_gem_shmem_object {
>*/
> unsigned int pages_use_count;
>
> + /**
> + * @pages_pin_count:
> + *
> + * Reference count on the pinned pages table.
> + * The pages allowed to be evicted and purged by memory
> + * shrinker only when the count is zero, otherwise pages
> + * are hard-pinned in memory.
> + */
> + struct kref pages_pin_count;
> +
> /**
>* @madv: State for madvise
>*
[Intel-gfx] [PATCH v15 12/23] drm/shmem-helper: Add and use pages_pin_count
Add separate pages_pin_count for tracking of whether drm-shmem pages are
moveable or not. With the addition of memory shrinker support to drm-shmem,
the pages_use_count will no longer determine whether pages are hard-pinned
in memory, but whether pages exit and are soft-pinned (and could be swapped
out). The pages_pin_count > 1 will hard-pin pages in memory.
Suggested-by: Boris Brezillon
Signed-off-by: Dmitry Osipenko
---
drivers/gpu/drm/drm_gem_shmem_helper.c | 22 +-
include/drm/drm_gem_shmem_helper.h | 10 ++
2 files changed, 27 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c
b/drivers/gpu/drm/drm_gem_shmem_helper.c
index d545d3d227d7..1a7e5c332fd8 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -234,14 +234,22 @@ static int drm_gem_shmem_pin_locked(struct
drm_gem_shmem_object *shmem)
dma_resv_assert_held(shmem->base.resv);
+ if (kref_get_unless_zero(>pages_pin_count))
+ return 0;
+
ret = drm_gem_shmem_get_pages_locked(shmem);
+ if (!ret)
+ kref_init(>pages_pin_count);
return ret;
}
-static void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
+static void drm_gem_shmem_kref_unpin_pages(struct kref *kref)
{
- dma_resv_assert_held(shmem->base.resv);
+ struct drm_gem_shmem_object *shmem;
+
+ shmem = container_of(kref, struct drm_gem_shmem_object,
+pages_pin_count);
drm_gem_shmem_put_pages_locked(shmem);
}
@@ -263,6 +271,9 @@ int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem)
drm_WARN_ON(obj->dev, obj->import_attach);
+ if (kref_get_unless_zero(>pages_pin_count))
+ return 0;
+
ret = dma_resv_lock_interruptible(shmem->base.resv, NULL);
if (ret)
return ret;
@@ -286,9 +297,10 @@ void drm_gem_shmem_unpin(struct drm_gem_shmem_object
*shmem)
drm_WARN_ON(obj->dev, obj->import_attach);
- dma_resv_lock(shmem->base.resv, NULL);
- drm_gem_shmem_unpin_locked(shmem);
- dma_resv_unlock(shmem->base.resv);
+ if (kref_put_dma_resv(>pages_pin_count,
+ drm_gem_shmem_kref_unpin_pages,
+ obj->resv, NULL))
+ dma_resv_unlock(obj->resv);
}
EXPORT_SYMBOL_GPL(drm_gem_shmem_unpin);
diff --git a/include/drm/drm_gem_shmem_helper.h
b/include/drm/drm_gem_shmem_helper.h
index ec2d8b24e3cf..afb7cd671e2a 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -39,6 +39,16 @@ struct drm_gem_shmem_object {
*/
unsigned int pages_use_count;
+ /**
+* @pages_pin_count:
+*
+* Reference count on the pinned pages table.
+* The pages allowed to be evicted and purged by memory
+* shrinker only when the count is zero, otherwise pages
+* are hard-pinned in memory.
+*/
+ struct kref pages_pin_count;
+
/**
* @madv: State for madvise
*
--
2.41.0
