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 <[email protected]>
---
include/linux/stackdepot.h | 11 +++++++++++
lib/stackdepot.c | 8 ++++++++
mm/page_owner.c | 15 +++++++++++++++
3 files changed, 34 insertions(+)
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 = {
--
2.43.0
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 <[email protected]>
Reviewed-by: Vlastimil Babka <[email protected]>
On Thu, 15 Feb 2024 at 11:55, Vlastimil Babka <[email protected]> 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 <[email protected]>
>
> Reviewed-by: Vlastimil Babka <[email protected]>
>
+1
Reviewed-by: Marco Elver <[email protected]>