Currently, the synchronize_shrinkers() is only used by TTM pool. It only
requires that no shrinkers run in parallel.
After we use RCU+refcount method to implement the lockless slab shrink,
we can not use shrinker_rwsem or synchronize_rcu() to guarantee that all
shrinker invocations have seen an update before freeing memory.
So we introduce a new pool_shrink_rwsem to implement a private
synchronize_shrinkers(), so as to achieve the same purpose.
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
---
drivers/gpu/drm/ttm/ttm_pool.c | 15 +++++++++++++++
include/linux/shrinker.h | 1 -
mm/shrinker.c | 15 ---------------
3 files changed, 15 insertions(+), 16 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
index cddb9151d20f..713b1c0a70e1 100644
--- a/drivers/gpu/drm/ttm/ttm_pool.c
+++ b/drivers/gpu/drm/ttm/ttm_pool.c
@@ -74,6 +74,7 @@ static struct ttm_pool_type global_dma32_uncached[MAX_ORDER + 1];
static spinlock_t shrinker_lock;
static struct list_head shrinker_list;
static struct shrinker mm_shrinker;
+static DECLARE_RWSEM(pool_shrink_rwsem);
/* Allocate pages of size 1 << order with the given gfp_flags */
static struct page *ttm_pool_alloc_page(struct ttm_pool *pool, gfp_t gfp_flags,
@@ -317,6 +318,7 @@ static unsigned int ttm_pool_shrink(void)
unsigned int num_pages;
struct page *p;
+ down_read(&pool_shrink_rwsem);
spin_lock(&shrinker_lock);
pt = list_first_entry(&shrinker_list, typeof(*pt), shrinker_list);
list_move_tail(&pt->shrinker_list, &shrinker_list);
@@ -329,6 +331,7 @@ static unsigned int ttm_pool_shrink(void)
} else {
num_pages = 0;
}
+ up_read(&pool_shrink_rwsem);
return num_pages;
}
@@ -572,6 +575,18 @@ void ttm_pool_init(struct ttm_pool *pool, struct device *dev,
}
EXPORT_SYMBOL(ttm_pool_init);
+/**
+ * synchronize_shrinkers - Wait for all running shrinkers to complete.
+ *
+ * This is useful to guarantee that all shrinker invocations have seen an
+ * update, before freeing memory, similar to rcu.
+ */
+static void synchronize_shrinkers(void)
+{
+ down_write(&pool_shrink_rwsem);
+ up_write(&pool_shrink_rwsem);
+}
+
/**
* ttm_pool_fini - Cleanup a pool
*
diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index 8dc15aa37410..6b5843c3b827 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -103,7 +103,6 @@ extern int __printf(2, 3) register_shrinker(struct shrinker *shrinker,
const char *fmt, ...);
extern void unregister_shrinker(struct shrinker *shrinker);
extern void free_prealloced_shrinker(struct shrinker *shrinker);
-extern void synchronize_shrinkers(void);
#ifdef CONFIG_SHRINKER_DEBUG
extern int __printf(2, 3) shrinker_debugfs_rename(struct shrinker *shrinker,
diff --git a/mm/shrinker.c b/mm/shrinker.c
index 043c87ccfab4..a16cd448b924 100644
--- a/mm/shrinker.c
+++ b/mm/shrinker.c
@@ -692,18 +692,3 @@ void unregister_shrinker(struct shrinker *shrinker)
shrinker->nr_deferred = NULL;
}
EXPORT_SYMBOL(unregister_shrinker);
-
-/**
- * synchronize_shrinkers - Wait for all running shrinkers to complete.
- *
- * This is equivalent to calling unregister_shrink() and register_shrinker(),
- * but atomically and with less overhead. This is useful to guarantee that all
- * shrinker invocations have seen an update, before freeing memory, similar to
- * rcu.
- */
-void synchronize_shrinkers(void)
-{
- down_write(&shrinker_rwsem);
- up_write(&shrinker_rwsem);
-}
-EXPORT_SYMBOL(synchronize_shrinkers);
--
2.30.2Am 16.08.23 um 10:34 schrieb Qi Zheng:
> Currently, the synchronize_shrinkers() is only used by TTM pool. It only
> requires that no shrinkers run in parallel.
>
> After we use RCU+refcount method to implement the lockless slab shrink,
> we can not use shrinker_rwsem or synchronize_rcu() to guarantee that all
> shrinker invocations have seen an update before freeing memory.
>
> So we introduce a new pool_shrink_rwsem to implement a private
> synchronize_shrinkers(), so as to achieve the same purpose.
>
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
> Reviewed-by: Muchun Song <songmuchun@bytedance.com>
> ---
> drivers/gpu/drm/ttm/ttm_pool.c | 15 +++++++++++++++
> include/linux/shrinker.h | 1 -
> mm/shrinker.c | 15 ---------------
> 3 files changed, 15 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
> index cddb9151d20f..713b1c0a70e1 100644
> --- a/drivers/gpu/drm/ttm/ttm_pool.c
> +++ b/drivers/gpu/drm/ttm/ttm_pool.c
> @@ -74,6 +74,7 @@ static struct ttm_pool_type global_dma32_uncached[MAX_ORDER + 1];
> static spinlock_t shrinker_lock;
> static struct list_head shrinker_list;
> static struct shrinker mm_shrinker;
> +static DECLARE_RWSEM(pool_shrink_rwsem);
>
> /* Allocate pages of size 1 << order with the given gfp_flags */
> static struct page *ttm_pool_alloc_page(struct ttm_pool *pool, gfp_t gfp_flags,
> @@ -317,6 +318,7 @@ static unsigned int ttm_pool_shrink(void)
> unsigned int num_pages;
> struct page *p;
>
> + down_read(&pool_shrink_rwsem);
> spin_lock(&shrinker_lock);
> pt = list_first_entry(&shrinker_list, typeof(*pt), shrinker_list);
> list_move_tail(&pt->shrinker_list, &shrinker_list);
> @@ -329,6 +331,7 @@ static unsigned int ttm_pool_shrink(void)
> } else {
> num_pages = 0;
> }
> + up_read(&pool_shrink_rwsem);
>
> return num_pages;
> }
> @@ -572,6 +575,18 @@ void ttm_pool_init(struct ttm_pool *pool, struct device *dev,
> }
> EXPORT_SYMBOL(ttm_pool_init);
>
> +/**
> + * synchronize_shrinkers - Wait for all running shrinkers to complete.
> + *
> + * This is useful to guarantee that all shrinker invocations have seen an
> + * update, before freeing memory, similar to rcu.
> + */
> +static void synchronize_shrinkers(void)
Please rename that function to ttm_pool_synchronize_shrinkers().
With that done feel free to add Reviewed-by: Christian König
<christian.koenig@amd.com>
Regards,
Christian.
> +{
> + down_write(&pool_shrink_rwsem);
> + up_write(&pool_shrink_rwsem);
> +}
> +
> /**
> * ttm_pool_fini - Cleanup a pool
> *
> diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
> index 8dc15aa37410..6b5843c3b827 100644
> --- a/include/linux/shrinker.h
> +++ b/include/linux/shrinker.h
> @@ -103,7 +103,6 @@ extern int __printf(2, 3) register_shrinker(struct shrinker *shrinker,
> const char *fmt, ...);
> extern void unregister_shrinker(struct shrinker *shrinker);
> extern void free_prealloced_shrinker(struct shrinker *shrinker);
> -extern void synchronize_shrinkers(void);
>
> #ifdef CONFIG_SHRINKER_DEBUG
> extern int __printf(2, 3) shrinker_debugfs_rename(struct shrinker *shrinker,
> diff --git a/mm/shrinker.c b/mm/shrinker.c
> index 043c87ccfab4..a16cd448b924 100644
> --- a/mm/shrinker.c
> +++ b/mm/shrinker.c
> @@ -692,18 +692,3 @@ void unregister_shrinker(struct shrinker *shrinker)
> shrinker->nr_deferred = NULL;
> }
> EXPORT_SYMBOL(unregister_shrinker);
> -
> -/**
> - * synchronize_shrinkers - Wait for all running shrinkers to complete.
> - *
> - * This is equivalent to calling unregister_shrink() and register_shrinker(),
> - * but atomically and with less overhead. This is useful to guarantee that all
> - * shrinker invocations have seen an update, before freeing memory, similar to
> - * rcu.
> - */
> -void synchronize_shrinkers(void)
> -{
> - down_write(&shrinker_rwsem);
> - up_write(&shrinker_rwsem);
> -}
> -EXPORT_SYMBOL(synchronize_shrinkers);
Hi Christian,
On 2023/8/16 17:14, Christian König wrote:
> Am 16.08.23 um 10:34 schrieb Qi Zheng:
>> Currently, the synchronize_shrinkers() is only used by TTM pool. It only
>> requires that no shrinkers run in parallel.
>>
>> After we use RCU+refcount method to implement the lockless slab shrink,
>> we can not use shrinker_rwsem or synchronize_rcu() to guarantee that all
>> shrinker invocations have seen an update before freeing memory.
>>
>> So we introduce a new pool_shrink_rwsem to implement a private
>> synchronize_shrinkers(), so as to achieve the same purpose.
>>
>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
>> Reviewed-by: Muchun Song <songmuchun@bytedance.com>
>> ---
>> drivers/gpu/drm/ttm/ttm_pool.c | 15 +++++++++++++++
>> include/linux/shrinker.h | 1 -
>> mm/shrinker.c | 15 ---------------
>> 3 files changed, 15 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c
>> b/drivers/gpu/drm/ttm/ttm_pool.c
>> index cddb9151d20f..713b1c0a70e1 100644
>> --- a/drivers/gpu/drm/ttm/ttm_pool.c
>> +++ b/drivers/gpu/drm/ttm/ttm_pool.c
>> @@ -74,6 +74,7 @@ static struct ttm_pool_type
>> global_dma32_uncached[MAX_ORDER + 1];
>> static spinlock_t shrinker_lock;
>> static struct list_head shrinker_list;
>> static struct shrinker mm_shrinker;
>> +static DECLARE_RWSEM(pool_shrink_rwsem);
>> /* Allocate pages of size 1 << order with the given gfp_flags */
>> static struct page *ttm_pool_alloc_page(struct ttm_pool *pool, gfp_t
>> gfp_flags,
>> @@ -317,6 +318,7 @@ static unsigned int ttm_pool_shrink(void)
>> unsigned int num_pages;
>> struct page *p;
>> + down_read(&pool_shrink_rwsem);
>> spin_lock(&shrinker_lock);
>> pt = list_first_entry(&shrinker_list, typeof(*pt), shrinker_list);
>> list_move_tail(&pt->shrinker_list, &shrinker_list);
>> @@ -329,6 +331,7 @@ static unsigned int ttm_pool_shrink(void)
>> } else {
>> num_pages = 0;
>> }
>> + up_read(&pool_shrink_rwsem);
>> return num_pages;
>> }
>> @@ -572,6 +575,18 @@ void ttm_pool_init(struct ttm_pool *pool, struct
>> device *dev,
>> }
>> EXPORT_SYMBOL(ttm_pool_init);
>> +/**
>> + * synchronize_shrinkers - Wait for all running shrinkers to complete.
>> + *
>> + * This is useful to guarantee that all shrinker invocations have
>> seen an
>> + * update, before freeing memory, similar to rcu.
>> + */
>> +static void synchronize_shrinkers(void)
>
> Please rename that function to ttm_pool_synchronize_shrinkers().
OK, will do.
>
> With that done feel free to add Reviewed-by: Christian König
> <christian.koenig@amd.com>
>
Thanks,
Qi
> Regards,
> Christian.
>
>> +{
>> + down_write(&pool_shrink_rwsem);
>> + up_write(&pool_shrink_rwsem);
>> +}
>> +
>> /**
>> * ttm_pool_fini - Cleanup a pool
>> *
>> diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
>> index 8dc15aa37410..6b5843c3b827 100644
>> --- a/include/linux/shrinker.h
>> +++ b/include/linux/shrinker.h
>> @@ -103,7 +103,6 @@ extern int __printf(2, 3) register_shrinker(struct
>> shrinker *shrinker,
>> const char *fmt, ...);
>> extern void unregister_shrinker(struct shrinker *shrinker);
>> extern void free_prealloced_shrinker(struct shrinker *shrinker);
>> -extern void synchronize_shrinkers(void);
>> #ifdef CONFIG_SHRINKER_DEBUG
>> extern int __printf(2, 3) shrinker_debugfs_rename(struct shrinker
>> *shrinker,
>> diff --git a/mm/shrinker.c b/mm/shrinker.c
>> index 043c87ccfab4..a16cd448b924 100644
>> --- a/mm/shrinker.c
>> +++ b/mm/shrinker.c
>> @@ -692,18 +692,3 @@ void unregister_shrinker(struct shrinker *shrinker)
>> shrinker->nr_deferred = NULL;
>> }
>> EXPORT_SYMBOL(unregister_shrinker);
>> -
>> -/**
>> - * synchronize_shrinkers - Wait for all running shrinkers to complete.
>> - *
>> - * This is equivalent to calling unregister_shrink() and
>> register_shrinker(),
>> - * but atomically and with less overhead. This is useful to guarantee
>> that all
>> - * shrinker invocations have seen an update, before freeing memory,
>> similar to
>> - * rcu.
>> - */
>> -void synchronize_shrinkers(void)
>> -{
>> - down_write(&shrinker_rwsem);
>> - up_write(&shrinker_rwsem);
>> -}
>> -EXPORT_SYMBOL(synchronize_shrinkers);
>
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