[PATCH v7 4/4] mm,page_owner: Filter out stacks by a threshold

[Oscar Salvador]

We want to be able to filter out the stacks based on
a threshold we can tune.
By writing to 'page_owner_threshold' file, we can adjust
the threshold value.

Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
---
 mm/page_owner.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/mm/page_owner.c b/mm/page_owner.c
index aea212734557..d95a73cf2581 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -780,14 +780,18 @@ static void *stack_next(struct seq_file *m, void *v, loff_t *ppos)
 	return stack;
 }
 
+static unsigned long page_owner_stack_threshold;
+
 static int stack_print(struct seq_file *m, void *v)
 {
 	char *buf;
 	int ret = 0;
 	struct stack_iterator *iter = m->private;
 	struct stack_record *stack = iter->last_stack;
+	int stack_count = refcount_read(&stack->count);
 
-	if (!stack->size || stack->size < 0 || refcount_read(&stack->count) < 2)
+	if (!stack->size || stack->size < 0 || stack_count < 2 ||
+	    stack_count < page_owner_stack_threshold)
 		return 0;
 
 	buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
@@ -832,6 +836,21 @@ const struct file_operations page_owner_stack_operations = {
 	.release	= seq_release,
 };
 
+static int page_owner_threshold_get(void *data, u64 *val)
+{
+	*val = page_owner_stack_threshold;
+	return 0;
+}
+
+static int page_owner_threshold_set(void *data, u64 val)
+{
+	page_owner_stack_threshold = val;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(proc_page_owner_threshold, &page_owner_threshold_get,
+			&page_owner_threshold_set, "%llu");
+
 static int __init pageowner_init(void)
 {
 	if (!static_branch_unlikely(&page_owner_inited)) {
@@ -843,6 +862,8 @@ static int __init pageowner_init(void)
 			    &proc_page_owner_operations);
 	debugfs_create_file("page_owner_stacks", 0400, NULL, NULL,
 			    &page_owner_stack_operations);
+	debugfs_create_file("page_owner_threshold", 0600, NULL, NULL,
+			    &proc_page_owner_threshold);
 
 	return 0;
 }
-- 
2.43.0