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[PATCH v4 5/8] mm: shrinkers: make count and scan in shrinker debugfs lockless

Qi Zheng posted 8 patches 3 years, 1 month ago
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[PATCH v4 5/8] mm: shrinkers: make count and scan in shrinker debugfs lockless
Posted by Qi Zheng 3 years, 1 month ago 
Like global and memcg slab shrink, also use SRCU to
make count and scan operations in memory shrinker
debugfs lockless.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 mm/shrinker_debug.c | 24 +++++++-----------------
 1 file changed, 7 insertions(+), 17 deletions(-)

diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
index 39c3491e28a3..6aa7a7ec69da 100644
--- a/mm/shrinker_debug.c
+++ b/mm/shrinker_debug.c
@@ -9,6 +9,7 @@
 /* defined in vmscan.c */
 extern struct rw_semaphore shrinker_rwsem;
 extern struct list_head shrinker_list;
+extern struct srcu_struct shrinker_srcu;
 
 static DEFINE_IDA(shrinker_debugfs_ida);
 static struct dentry *shrinker_debugfs_root;
@@ -49,18 +50,13 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
 	struct mem_cgroup *memcg;
 	unsigned long total;
 	bool memcg_aware;
-	int ret, nid;
+	int ret = 0, nid, srcu_idx;
 
 	count_per_node = kcalloc(nr_node_ids, sizeof(unsigned long), GFP_KERNEL);
 	if (!count_per_node)
 		return -ENOMEM;
 
-	ret = down_read_killable(&shrinker_rwsem);
-	if (ret) {
-		kfree(count_per_node);
-		return ret;
-	}
-	rcu_read_lock();
+	srcu_idx = srcu_read_lock(&shrinker_srcu);
 
 	memcg_aware = shrinker->flags & SHRINKER_MEMCG_AWARE;
 
@@ -91,8 +87,7 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
 		}
 	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
 
-	rcu_read_unlock();
-	up_read(&shrinker_rwsem);
+	srcu_read_unlock(&shrinker_srcu, srcu_idx);
 
 	kfree(count_per_node);
 	return ret;
@@ -115,9 +110,8 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
 		.gfp_mask = GFP_KERNEL,
 	};
 	struct mem_cgroup *memcg = NULL;
-	int nid;
+	int nid, srcu_idx;
 	char kbuf[72];
-	ssize_t ret;
 
 	read_len = size < (sizeof(kbuf) - 1) ? size : (sizeof(kbuf) - 1);
 	if (copy_from_user(kbuf, buf, read_len))
@@ -146,11 +140,7 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
 		return -EINVAL;
 	}
 
-	ret = down_read_killable(&shrinker_rwsem);
-	if (ret) {
-		mem_cgroup_put(memcg);
-		return ret;
-	}
+	srcu_idx = srcu_read_lock(&shrinker_srcu);
 
 	sc.nid = nid;
 	sc.memcg = memcg;
@@ -159,7 +149,7 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
 
 	shrinker->scan_objects(shrinker, &sc);
 
-	up_read(&shrinker_rwsem);
+	srcu_read_unlock(&shrinker_srcu, srcu_idx);
 	mem_cgroup_put(memcg);
 
 	return size;
-- 
2.20.1
Re: [PATCH v4 5/8] mm: shrinkers: make count and scan in shrinker debugfs lockless
Posted by Kirill Tkhai 3 years, 1 month ago 
On 07.03.2023 09:56, Qi Zheng wrote:
> Like global and memcg slab shrink, also use SRCU to
> make count and scan operations in memory shrinker
> debugfs lockless.
> 
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>

Acked-by: Kirill Tkhai <tkhai@ya.ru>

> ---
>  mm/shrinker_debug.c | 24 +++++++-----------------
>  1 file changed, 7 insertions(+), 17 deletions(-)
> 
> diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
> index 39c3491e28a3..6aa7a7ec69da 100644
> --- a/mm/shrinker_debug.c
> +++ b/mm/shrinker_debug.c
> @@ -9,6 +9,7 @@
>  /* defined in vmscan.c */
>  extern struct rw_semaphore shrinker_rwsem;
>  extern struct list_head shrinker_list;
> +extern struct srcu_struct shrinker_srcu;
>  
>  static DEFINE_IDA(shrinker_debugfs_ida);
>  static struct dentry *shrinker_debugfs_root;
> @@ -49,18 +50,13 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
>  	struct mem_cgroup *memcg;
>  	unsigned long total;
>  	bool memcg_aware;
> -	int ret, nid;
> +	int ret = 0, nid, srcu_idx;
>  
>  	count_per_node = kcalloc(nr_node_ids, sizeof(unsigned long), GFP_KERNEL);
>  	if (!count_per_node)
>  		return -ENOMEM;
>  
> -	ret = down_read_killable(&shrinker_rwsem);
> -	if (ret) {
> -		kfree(count_per_node);
> -		return ret;
> -	}
> -	rcu_read_lock();
> +	srcu_idx = srcu_read_lock(&shrinker_srcu);
>  
>  	memcg_aware = shrinker->flags & SHRINKER_MEMCG_AWARE;
>  
> @@ -91,8 +87,7 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
>  		}
>  	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
>  
> -	rcu_read_unlock();
> -	up_read(&shrinker_rwsem);
> +	srcu_read_unlock(&shrinker_srcu, srcu_idx);
>  
>  	kfree(count_per_node);
>  	return ret;
> @@ -115,9 +110,8 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
>  		.gfp_mask = GFP_KERNEL,
>  	};
>  	struct mem_cgroup *memcg = NULL;
> -	int nid;
> +	int nid, srcu_idx;
>  	char kbuf[72];
> -	ssize_t ret;
>  
>  	read_len = size < (sizeof(kbuf) - 1) ? size : (sizeof(kbuf) - 1);
>  	if (copy_from_user(kbuf, buf, read_len))
> @@ -146,11 +140,7 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
>  		return -EINVAL;
>  	}
>  
> -	ret = down_read_killable(&shrinker_rwsem);
> -	if (ret) {
> -		mem_cgroup_put(memcg);
> -		return ret;
> -	}
> +	srcu_idx = srcu_read_lock(&shrinker_srcu);
>  
>  	sc.nid = nid;
>  	sc.memcg = memcg;
> @@ -159,7 +149,7 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
>  
>  	shrinker->scan_objects(shrinker, &sc);
>  
> -	up_read(&shrinker_rwsem);
> +	srcu_read_unlock(&shrinker_srcu, srcu_idx);
>  	mem_cgroup_put(memcg);
>  
>  	return size;
Re: [PATCH v4 5/8] mm: shrinkers: make count and scan in shrinker debugfs lockless
Posted by Vlastimil Babka 3 years, 1 month ago 
On 3/7/23 07:56, Qi Zheng wrote:
> Like global and memcg slab shrink, also use SRCU to
> make count and scan operations in memory shrinker
> debugfs lockless.
> 
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
> ---
>  mm/shrinker_debug.c | 24 +++++++-----------------
>  1 file changed, 7 insertions(+), 17 deletions(-)
> 
> diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
> index 39c3491e28a3..6aa7a7ec69da 100644
> --- a/mm/shrinker_debug.c
> +++ b/mm/shrinker_debug.c

Forgot to mention that this file should now likely also #include <linux/srcu.h>

> @@ -9,6 +9,7 @@
>  /* defined in vmscan.c */
>  extern struct rw_semaphore shrinker_rwsem;
>  extern struct list_head shrinker_list;
> +extern struct srcu_struct shrinker_srcu;
Re: [PATCH v4 5/8] mm: shrinkers: make count and scan in shrinker debugfs lockless
Posted by Qi Zheng 3 years, 1 month ago 

On 2023/3/9 17:39, Vlastimil Babka wrote:
> On 3/7/23 07:56, Qi Zheng wrote:
>> Like global and memcg slab shrink, also use SRCU to
>> make count and scan operations in memory shrinker
>> debugfs lockless.
>>
>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
>> ---
>>   mm/shrinker_debug.c | 24 +++++++-----------------
>>   1 file changed, 7 insertions(+), 17 deletions(-)
>>
>> diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
>> index 39c3491e28a3..6aa7a7ec69da 100644
>> --- a/mm/shrinker_debug.c
>> +++ b/mm/shrinker_debug.c
> 
> Forgot to mention that this file should now likely also #include <linux/srcu.h>

Got it. Will do.

Thanks,
Qi

> 
>> @@ -9,6 +9,7 @@
>>   /* defined in vmscan.c */
>>   extern struct rw_semaphore shrinker_rwsem;
>>   extern struct list_head shrinker_list;
>> +extern struct srcu_struct shrinker_srcu;
>
Re: [PATCH v4 5/8] mm: shrinkers: make count and scan in shrinker debugfs lockless
Posted by Vlastimil Babka 3 years, 1 month ago 
On 3/7/23 07:56, Qi Zheng wrote:
> Like global and memcg slab shrink, also use SRCU to
> make count and scan operations in memory shrinker
> debugfs lockless.
> 
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>  mm/shrinker_debug.c | 24 +++++++-----------------
>  1 file changed, 7 insertions(+), 17 deletions(-)
> 
> diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
> index 39c3491e28a3..6aa7a7ec69da 100644
> --- a/mm/shrinker_debug.c
> +++ b/mm/shrinker_debug.c
> @@ -9,6 +9,7 @@
>  /* defined in vmscan.c */
>  extern struct rw_semaphore shrinker_rwsem;
>  extern struct list_head shrinker_list;
> +extern struct srcu_struct shrinker_srcu;
>  
>  static DEFINE_IDA(shrinker_debugfs_ida);
>  static struct dentry *shrinker_debugfs_root;
> @@ -49,18 +50,13 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
>  	struct mem_cgroup *memcg;
>  	unsigned long total;
>  	bool memcg_aware;
> -	int ret, nid;
> +	int ret = 0, nid, srcu_idx;
>  
>  	count_per_node = kcalloc(nr_node_ids, sizeof(unsigned long), GFP_KERNEL);
>  	if (!count_per_node)
>  		return -ENOMEM;
>  
> -	ret = down_read_killable(&shrinker_rwsem);
> -	if (ret) {
> -		kfree(count_per_node);
> -		return ret;
> -	}
> -	rcu_read_lock();
> +	srcu_idx = srcu_read_lock(&shrinker_srcu);
>  
>  	memcg_aware = shrinker->flags & SHRINKER_MEMCG_AWARE;
>  
> @@ -91,8 +87,7 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
>  		}
>  	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
>  
> -	rcu_read_unlock();
> -	up_read(&shrinker_rwsem);
> +	srcu_read_unlock(&shrinker_srcu, srcu_idx);
>  
>  	kfree(count_per_node);
>  	return ret;
> @@ -115,9 +110,8 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
>  		.gfp_mask = GFP_KERNEL,
>  	};
>  	struct mem_cgroup *memcg = NULL;
> -	int nid;
> +	int nid, srcu_idx;
>  	char kbuf[72];
> -	ssize_t ret;
>  
>  	read_len = size < (sizeof(kbuf) - 1) ? size : (sizeof(kbuf) - 1);
>  	if (copy_from_user(kbuf, buf, read_len))
> @@ -146,11 +140,7 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
>  		return -EINVAL;
>  	}
>  
> -	ret = down_read_killable(&shrinker_rwsem);
> -	if (ret) {
> -		mem_cgroup_put(memcg);
> -		return ret;
> -	}
> +	srcu_idx = srcu_read_lock(&shrinker_srcu);
>  
>  	sc.nid = nid;
>  	sc.memcg = memcg;
> @@ -159,7 +149,7 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
>  
>  	shrinker->scan_objects(shrinker, &sc);
>  
> -	up_read(&shrinker_rwsem);
> +	srcu_read_unlock(&shrinker_srcu, srcu_idx);
>  	mem_cgroup_put(memcg);
>  
>  	return size;

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