On 2/12/24 23:30, 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 implement {inc,dec}_stack_record_count() which increments
> or decrements on respective allocation and free operations, via
> __reset_page_owner() (free operation) and __set_page_owner() (alloc
> operation).
>
> 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.
> inc_stack_record_count() is responsible of adding new stack_records
> into the list stack_list.
>
> Modifications on the list are protected via a spinlock with irqs
> disabled, since this code can also be reached from IRQ context.
>
> Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
> ---
> include/linux/stackdepot.h | 9 +++++
> lib/stackdepot.c | 8 +++++
> mm/page_owner.c | 73 ++++++++++++++++++++++++++++++++++++++
> 3 files changed, 90 insertions(+)
> static inline void __set_page_owner_handle(struct page_ext *page_ext,
> @@ -199,6 +271,7 @@ noinline void __set_page_owner(struct page *page, unsigned short order,
> return;
> __set_page_owner_handle(page_ext, handle, order, gfp_mask);
> page_ext_put(page_ext);
> + inc_stack_record_count(handle);
What if this is dummy handle, which means we have recursed in page owner,
and we'll by trying to kmalloc() its struct stack and link it to the
stack_list because it was returned for the first time? Also failure_handle.
Could you pre-create static (not kmalloc) struct stack for these handles
with refcount of 0 and insert them to stack_list, all during
init_page_owner()? Bonus: no longer treating stack_list == NULL in a special
way in add_stack_record_to_list() (although you don't need to handle it
extra even now, AFAICS).
> }
>
> void __set_page_owner_migrate_reason(struct page *page, int reason)
