[PATCH v9 6/7] mm,page_owner: Filter out stacks by a threshold

[Oscar Salvador <osalvador@suse.de>]

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

Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
 mm/page_owner.c | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/mm/page_owner.c b/mm/page_owner.c
index 5258a417f4d1..9b975f59b773 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -846,9 +846,11 @@ 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)
 {
-	int i;
+	int i, stack_count;
 	struct stack *stack = v;
 	unsigned long *entries;
 	unsigned long nr_entries;
@@ -856,14 +858,15 @@ static int stack_print(struct seq_file *m, void *v)
 
 	nr_entries = stack_record->size;
 	entries = stack_record->entries;
+	stack_count = refcount_read(&stack_record->count);
 
-	if (!nr_entries || nr_entries < 0 ||
-	    refcount_read(&stack_record->count) < 2)
+	if (!nr_entries || nr_entries < 0 || stack_count < 2 ||
+	    stack_count < page_owner_stack_threshold)
 		return 0;
 
 	for (i = 0; i < nr_entries; i++)
 		seq_printf(m, " %pS\n", (void *)entries[i]);
-	seq_printf(m, "stack_count: %d\n\n", refcount_read(&stack_record->count));
+	seq_printf(m, "stack_count: %d\n\n", stack_count);
 
 	return 0;
 }
@@ -891,6 +894,22 @@ static const struct file_operations page_owner_stack_operations = {
 	.release	= seq_release,
 };
 
+static int page_owner_threshold_get(void *data, u64 *val)
+{
+	*val = READ_ONCE(page_owner_stack_threshold);
+	return 0;
+}
+
+static int page_owner_threshold_set(void *data, u64 val)
+{
+	WRITE_ONCE(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)
 {
 	struct dentry *dir;
@@ -905,6 +924,8 @@ static int __init pageowner_init(void)
 	dir = debugfs_create_dir("page_owner_stacks", NULL);
 	debugfs_create_file("show_stacks", 0400, dir, NULL,
 			    &page_owner_stack_operations);
+	debugfs_create_file("count_threshold", 0600, dir, NULL,
+			    &proc_page_owner_threshold);
 
 	return 0;
 }
-- 
2.43.0