diff mbox series

[v5,3/3] mm,page_owner: Filter out stacks by a threshold counter

Message ID 20230516182537.3139-4-osalvador@suse.de
State New
Headers
Series page_owner: print stacks and their counter |

Commit Message

Oscar Salvador May 16, 2023, 6:25 p.m. UTC 
  We want to be able to filter out the output on a threshold basis,
in this way we can get rid of a lot of noise and focus only on those
stacks which have an allegedly high counter.

We can control the threshold value by a new file called
'page_owner_threshold', which is 0 by default.

Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
 lib/stackdepot.c |  5 ++++-
 mm/page_owner.c  | 21 +++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

Comments

Alexander Potapenko May 22, 2023, 8:40 a.m. UTC | #1 
On Tue, May 16, 2023 at 8:25 PM Oscar Salvador <osalvador@suse.de> wrote:
>
> We want to be able to filter out the output on a threshold basis,
> in this way we can get rid of a lot of noise and focus only on those
> stacks which have an allegedly high counter.
>
> We can control the threshold value by a new file called
> 'page_owner_threshold', which is 0 by default.
>
> Signed-off-by: Oscar Salvador <osalvador@suse.de>

Nack.
We must decouple stackdepot from page_owner as much as possible, not
add extra dependencies by sharing variables between the two.

What you need here is a pair of xxx_iter_start()/xxx_iter_next()
functions in stackdepot.c that will hold the iteration state in a
struct and return the next stack trace.
The threshold value can also be part of that struct.
Vlastimil Babka June 12, 2023, 10:53 a.m. UTC | #2 
On 5/22/23 10:40, Alexander Potapenko wrote:
> On Tue, May 16, 2023 at 8:25 PM Oscar Salvador <osalvador@suse.de> wrote:
>> We want to be able to filter out the output on a threshold basis,
>> in this way we can get rid of a lot of noise and focus only on those
>> stacks which have an allegedly high counter.
>>
>> We can control the threshold value by a new file called
>> 'page_owner_threshold', which is 0 by default.
>>
>> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> Nack.
> We must decouple stackdepot from page_owner as much as possible, not
> add extra dependencies by sharing variables between the two.
> 
> What you need here is a pair of xxx_iter_start()/xxx_iter_next()
> functions in stackdepot.c that will hold the iteration state in a
> struct and return the next stack trace.
> The threshold value can also be part of that struct.

Agreed, that should be a much cleaner approach.
diff mbox series

Patch

diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index c4af2e946500..7053221ce1d8 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -488,6 +488,9 @@  static struct stack_record *stack_depot_getstack(depot_stack_handle_t handle)
 }
 
 #ifdef CONFIG_PAGE_OWNER
+
+extern unsigned long page_owner_stack_threshold;
+
 void *stack_start(struct seq_file *m, loff_t *ppos)
 {
 	unsigned long *table = m->private;
@@ -543,7 +546,7 @@  int stack_print(struct seq_file *m, void *v)
 
 	if (!stack->size || stack->size < 0 ||
 	    stack->size > PAGE_SIZE || stack->handle.valid != 1 ||
-	    refcount_read(&stack->count) < 1)
+	    refcount_read(&stack->count) < page_owner_stack_threshold)
 		return 0;
 
 	buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
diff --git a/mm/page_owner.c b/mm/page_owner.c
index 2d97f6b34ea6..28c519fc9372 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -743,6 +743,23 @@  const struct file_operations page_owner_stack_operations = {
 	.release        = seq_release,
 };
 
+unsigned long page_owner_stack_threshold;
+
+int page_owner_threshold_get(void *data, u64 *val)
+{
+	*val = page_owner_stack_threshold;
+	return 0;
+}
+
+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)) {
@@ -755,6 +772,10 @@  static int __init pageowner_init(void)
 
 	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);
+
+	page_owner_stack_threshold = 0;
 
 	return 0;
 }