2023-02-23 13:28:20

by Qi Zheng

Subject: [PATCH v2 4/7] mm: shrinkers: make count and scan in shrinker debugfs lockless

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 <[email protected]>
---
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