diff mbox series

[v9,3/7] mm,page_owner: Maintain own list of stack_records structs

Message ID 20240214170157.17530-4-osalvador@suse.de
State New
Headers
Series page_owner: print stacks and their outstanding allocations |

Commit Message

Oscar Salvador Feb. 14, 2024, 5:01 p.m. UTC 
  page_owner needs to increment a stack_record refcount when a new allocation
occurs, and decrement it on a free operation.
In order to do that, we need to have a way to get a stack_record from a
handle.
Implement __stack_depot_get_stack_record() which just does that, and make
it public so page_owner can use it.

Also, traversing all stackdepot buckets comes with its own complexity,
plus we would have to implement a way to mark only those stack_records
that were originated from page_owner, as those are the ones we are
interested in.
For that reason, page_owner maintains its own list of stack_records,
because traversing that list is faster than traversing all buckets
while keeping at the same time a low complexity.

For now, add to stack_list only the stack_records of dummy_handle and
failure_handle, and set their refcount of 1.

Further patches will add code to increment or decrement stack_records
count on allocation and free operation.

Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
 include/linux/stackdepot.h | 11 +++++++++++
 lib/stackdepot.c           |  8 ++++++++
 mm/page_owner.c            | 15 +++++++++++++++
 3 files changed, 34 insertions(+)

Comments

Vlastimil Babka Feb. 15, 2024, 10:55 a.m. UTC | #1 
On 2/14/24 18:01, Oscar Salvador wrote:
> page_owner needs to increment a stack_record refcount when a new allocation
> occurs, and decrement it on a free operation.
> In order to do that, we need to have a way to get a stack_record from a
> handle.
> Implement __stack_depot_get_stack_record() which just does that, and make
> it public so page_owner can use it.
> 
> Also, traversing all stackdepot buckets comes with its own complexity,
> plus we would have to implement a way to mark only those stack_records
> that were originated from page_owner, as those are the ones we are
> interested in.
> For that reason, page_owner maintains its own list of stack_records,
> because traversing that list is faster than traversing all buckets
> while keeping at the same time a low complexity.
> 
> For now, add to stack_list only the stack_records of dummy_handle and
> failure_handle, and set their refcount of 1.
> 
> Further patches will add code to increment or decrement stack_records
> count on allocation and free operation.
> 
> Signed-off-by: Oscar Salvador <osalvador@suse.de>

Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Marco Elver Feb. 15, 2024, 12:52 p.m. UTC | #2 
On Thu, 15 Feb 2024 at 11:55, Vlastimil Babka <vbabka@suse.cz> wrote:
>
> On 2/14/24 18:01, Oscar Salvador wrote:
> > page_owner needs to increment a stack_record refcount when a new allocation
> > occurs, and decrement it on a free operation.
> > In order to do that, we need to have a way to get a stack_record from a
> > handle.
> > Implement __stack_depot_get_stack_record() which just does that, and make
> > it public so page_owner can use it.
> >
> > Also, traversing all stackdepot buckets comes with its own complexity,
> > plus we would have to implement a way to mark only those stack_records
> > that were originated from page_owner, as those are the ones we are
> > interested in.
> > For that reason, page_owner maintains its own list of stack_records,
> > because traversing that list is faster than traversing all buckets
> > while keeping at the same time a low complexity.
> >
> > For now, add to stack_list only the stack_records of dummy_handle and
> > failure_handle, and set their refcount of 1.
> >
> > Further patches will add code to increment or decrement stack_records
> > count on allocation and free operation.
> >
> > Signed-off-by: Oscar Salvador <osalvador@suse.de>
>
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
>

+1

Reviewed-by: Marco Elver <elver@google.com>
diff mbox series

Patch

diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
index c4b5ad57c066..3c6caa5abc7c 100644
--- a/include/linux/stackdepot.h
+++ b/include/linux/stackdepot.h
@@ -178,6 +178,17 @@  depot_stack_handle_t stack_depot_save_flags(unsigned long *entries,
 depot_stack_handle_t stack_depot_save(unsigned long *entries,
 				      unsigned int nr_entries, gfp_t gfp_flags);
 
+/**
+ * __stack_depot_get_stack_record - Get a pointer to a stack_record struct
+ *
+ * @handle: Stack depot handle
+ *
+ * This function is only for internal purposes.
+ *
+ * Return: Returns a pointer to a stack_record struct
+ */
+struct stack_record *__stack_depot_get_stack_record(depot_stack_handle_t handle);
+
 /**
  * stack_depot_fetch - Fetch a stack trace from stack depot
  *
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 4a661a6777da..3da6d7cfcdfb 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -687,6 +687,14 @@  depot_stack_handle_t stack_depot_save(unsigned long *entries,
 }
 EXPORT_SYMBOL_GPL(stack_depot_save);
 
+struct stack_record *__stack_depot_get_stack_record(depot_stack_handle_t handle)
+{
+	if (!handle)
+		return NULL;
+
+	return depot_fetch_stack(handle);
+}
+
 unsigned int stack_depot_fetch(depot_stack_handle_t handle,
 			       unsigned long **entries)
 {
diff --git a/mm/page_owner.c b/mm/page_owner.c
index 5634e5d890f8..33e342b15d9b 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -36,6 +36,14 @@  struct page_owner {
 	pid_t free_tgid;
 };
 
+struct stack {
+	struct stack_record *stack_record;
+	struct stack *next;
+};
+static struct stack dummy_stack;
+static struct stack failure_stack;
+static struct stack *stack_list;
+
 static bool page_owner_enabled __initdata;
 DEFINE_STATIC_KEY_FALSE(page_owner_inited);
 
@@ -95,6 +103,13 @@  static __init void init_page_owner(void)
 	register_early_stack();
 	static_branch_enable(&page_owner_inited);
 	init_early_allocated_pages();
+	/* Initialize dummy and failure stacks and link them to stack_list */
+	dummy_stack.stack_record = __stack_depot_get_stack_record(dummy_handle);
+	failure_stack.stack_record = __stack_depot_get_stack_record(failure_handle);
+	refcount_set(&dummy_stack.stack_record->count, 1);
+	refcount_set(&failure_stack.stack_record->count, 1);
+	dummy_stack.next = &failure_stack;
+	stack_list = &dummy_stack;
 }
 
 struct page_ext_operations page_owner_ops = {